SPINE - AAOS

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SPINE - AAOS

SPINE
PAPERS
Table 1.
PSF Group
Collar Group
PAPER NO. 76
Mortality
20% (5/25)
12.5% (4/33)
Functional and Radiographic Outcomes of Geriatric
Odontoid Fractures Treated with Rigid Collar or
Posterior Fusion
Complications
24% (6/25)
6% (2/33)
Fracture Healing
28% (7/25)
6% (2/33)
Mobile Nonunion
0%
67% (20/30)
William J. Molinari, III, MD, Rochester, NY
Oner Khera, MD, Glendale, AZ
William Gruhn, PA-C, Rochester, NY
Robert W. Molinari, MD, Pittsford, NY
INTRODUCTION: Controversy exists as to the most effective
management option for elderly patients with type II odontoid
fractures. Furthermore, outcomes for those patients who do not
achieve fusion or fracture healing after treatment remain unclear
in the literature. The purpose of this study is to evaluate fracture
healing rates, functional outcomes, complications, and mortality
associated with rigid cervical collar and posterior fusion surgery
for the management of geriatric type II odontoid fractures.
METHODS: Fifty-eight consecutive elderly patients with type II
odontoid fractures were treated by the same fellowship-trained
spinal surgeon at a level 1 trauma center during an eight-year
period. Patients with greater than 50% odontoid displacement
were treated with posterior fusion surgery including C1-2 (PSF
Group, n= 25, Ave age = 80 yrs). Patients with less than 50%
odontoid displacement were treated with a rigid cervical collar for
12 weeks (Collar Group, n=33, Ave age = 83 yrs). Chart reviews
were performed evaluating patient comorbidities, treatment
complications, and mortality rates. At the time of ultimate
follow up, patients had open mouth, flexion and extension
radiographs to assess fracture stability and healing. Additionally,
functional outcomes were assessed using Neck Disability Index
(NDI), analog pain and satisfaction questionnaire scores.
RESULTS: At average 14 month follow up (range 3-48 months),
fracture healing rates were higher in the operative group (28%
vs 6%). A total of 64% of the nonoperative patients had mobile
nonunion versus 0% in the operative group. The average mobility of
the nonunion was 2.5mm (range 1-12mm). NDI scores were lower
in the nonoperative group (13 vs. 18.3) indicating a trend toward
less disability in the nonoperative group (p=0.23). There was
also a trend toward lower analog pain scores in the nonoperative
group (1.3 vs. 1.9, p=0.26). Satisfaction scores were equally high
in both groups (9.1 vs. 8.9). Mobile odontoid nonunion was not
associated with higher levels of disability or neck pain, and did not
affect scores for patient satisfaction. Mortality rate was 12.5% in
the C-collar group and 20% in the operative group. Complications
were higher in the operative group (24% vs 6%) (Table 1, Figure 1).
DISCUSSION AND CONCLUSION: Rates of type II odontoid
facture healing and stability appear to be higher in geriatric patients
treated with posterior fusion surgery. Fracture healing and stability
did not correlate with improved outcomes with respect to levels of
pain, function and satisfaction. Mortality and complication rates
are lower in those patients who are treated with a cervical collar
and early mobilization.
951
PAPER NO. 77
Reoperation Following Degenerative Spondylolisthesis
Surgery: A Subgroup Analysis of the SPORT
Edward P. Curry, MD, Philadelphia, PA
Kristen E. Radcliff, MD, Margate City, NJ
Alan S. Hilibrand, MD, Philadelphia, PA
Jeffrey A. Rihn, MD, Media, PA
Todd J. Albert, MD, Philadelphia, PA
Wenyan Zhao, PhD, Hanover, NH
Jon Lurie, MD, Lebanon, NH
James N. Weinstein, DO, Lebanon, NH
INTRODUCTION: Several factors are known to influence the
outcome of surgery of degenerative spondylolisthesis. However,
less is known about the predictors of reoperation. The SPORT trial
is a prospective, multicenter study of surgical treatment versus
nonoperative treatment for lumbar conditions. The hypothesis
of study is that there would be significant baseline differences
between patients who underwent reoperation and patients who
did not undergo reoperation for degenerative spondylolisthesis.
Such data might be helpful in identifying patients at risk for
developing additional problems at other levels METHODS:
This is a subgroup analysis of patients enrolled in SPORT for
treatment of degenerative spondylolisthesis with randomized
and observational cohorts. The degenerative spondylolisthesis
patients were divided according to reoperation (n=58) or
no reoperation (n=333). Change in primary and secondary
outcome measures and treatment effect of surgery were assessed
at baseline, one year, two years, three years, and four years.
RESULTS: At baseline, there were no significant differences
between reoperation and no reoperation patients in demographic
characteristics, clinical outcome scores, body mass index. The
u The FDA has not cleared the drug and/or medical device for the use described in this presentation (i.e. the drug or medical device is being discussed for an off label use).
For full information refer to page 14. An alphabetical faculty financial disclosure list can be found starting on page 19.
PAPERS, POSTERS & SCIENTIFIC EXHIBITS SPINE
reoperation patients had a significantly lower likelihood of having
pseudoclaudication (74% vs. 88%, p=0.007) or asymmetric
depressed reflexes (12% vs. 28%, p=0.015). There was no
difference between reoperation and no-reoperation patients in
type of procedure, levels of fusion, decompression level, or number
of levels decompressed. There was a significantly increased
percentage of complications of the index surgery in the reoperation
patients. By the final four year follow up, there was no significant
difference between reoperation and no reoperation groups in SF36
BP, SF36 PF, SF36 PCS, SF36 MCS, ODI, Sciatica Bothersomeness
Index, Low Back Bothersomeness, Percent Satisfaction, Leg Pain
Bothersomeness Index. The most common reasons for reoperation
were recurrent stenosis/progressive spondylolisthesis (5%), new
condition (2.4%), infection (2.4%), pseudoarthrosis/fusion
exploration (1.1%). The overall rate of reoperation at four years was
14.8% for patients with degenerative spondylolisthesis in the SPORT.
DISCUSSION AND CONCLUSION: The overall incidence
of reoperation at four years was 14.8% for degenerative
spondylolisthesis. Type of fusion, number of levels addressed, and
instrumentation were not associated with a change in incidence
of reoperation in patients with degenerative spondylolisthesis.
Preoperative symptoms of pseudoclaudication and asymmetric
depressed reflexes were associated with reduced risk of reoperation
for degenerative spondylolisthesis. There was no significant
difference in the outcome of patients who underwent reoperation
for degenerative spondylolisthesis versus patients who did not
undergo reoperation.
PAPER NO. 78
The Limited Benefit of Coronal Cobb Angle Correction
in the Setting of Adult Spinal Deformity
Virginie Lafage, PhD, New York, NY
Frank J. Schwab, MD, New York, NY
Benjamin Blondel, MD, New York, NY
Justin S. Smith, MD, Charlottesville, VA
Jason Demakakos
Keith H. Bridwell, MD, Saint Louis, MO
Steven D. Glassman, MD, Louisville, KY
Christopher I. Shaffrey, MD, Charlottesville, VA
INTRODUCTION: Adult spinal deformity (ASD) can cause
pain and disability due to global malalignment. The extent of
coronal plane deformity correction needed for clinical benefit
remains controversial but Cobb angle has been described
as a key parameter for evaluation of ASD patients. The aim
of this study was to evaluate the amount of Cobb angle
correction needed to achieve incremental clinical benefit and
likelihood of reaching minimal clinically important difference
(MCID) using health related quality of life (HRQL) scores.
METHODS: Baseline and two year radiographic and HRQL data
(ODI, SRS-22r and SF-12) were retrospectively analyzed for patients
consecutively enrolled in a multi-center, prospective ASD database.
Patients were divided into three groups based on postoperative
Cobb angle improvement: 35°. Pre and post-op results for
each group and changes in HRQL scores for each improvement
subdivision were analyzed using paired t-test and one-way ANOVA.
RESULTS: Sixty patients with thoraco-lumbar or lumbar curve
>50° were included. A significant improvement for HRQOL
scores was found between pre-op and last follow up data across
the study population (p<0.05). A correction of <25° resulted in
a significant improvement in HRQL scores (p35° also did not
improve the likelihood to reach MCID for SRS pain but increased
it for appearance (88%), activity (82%) and SF-12 PCS (82%).
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DISCUSSION AND CONCLUSION: This prospective study
offers clinically important data on the mixed benefit of limited
coronal deformity correction in the setting of ASD. To improve
patient reported pain, a Cobb correction of >25° but <35° appears
sufficient with no added benefit to further deformity correction.
Findings from this study add to the importance of pre-operative
planning and patient counseling (risk vs. benefit) in terms of need
for correction of coronal deformity.
PAPER NO. 79
A New Spine Surgery Specific Score to Predict
Morbidity and Mortality in Elective Spine Surgery
Abhishek Manu, Coimbatore, India
Ashok Thomas, Coimbatore, India
Janardhan Yerramshetty, PhD, Coimbatore, India
Ajoy P P. Shetty, Coimbatore, India
S. Rajasekaran, PhD, Coimbatore, India
INTRODUCTION: Spine surgery is associated with significant
postoperative complications which are probably caused
by both magnitude of the surgery and associated patient
comorbidities. Objectives of this study were to identify various
pre-operative comorbidities and factors reflecting magnitude of
surgeries that are associated with postoperative complications
and to formulate a scoring system specific to spine surgery.
METHODS: Pre-operative comorbidities and surgical factors
(Table 1) along with mortality, major morbidity (life threatening
complications that required intervention) and minor morbidity
(mild and not life threatening complications) were documented in
1,217 elective spine surgeries for model development and testing.
The maximum time period for assessing morbidity was one month.
Using cross-tabulations and Chi-square analysis, groupings were
identified for each significant factor based on major morbidity.
Using risk stratification analysis, a weightage score was assigned to
each group in all significant factors. Summation of all scores gave a
final morbidity score for each patient. Using ROC and discriminant
analyses, the developed score was tested to see whether it can do
any better than chance at predicting morbidity and mortality in
patients. The score was also validated on 200 randomly chosen
patients from the same sample. Finally, the commonly used
Charlson’s comorbidity index (CCI), an indicator of mortality, was
also assessed in 665 patients and was compared to this study’s score.
RESULTS: There were six deaths, 52 major morbidities and 142
minor morbidities. Chi-square analysis indicated that all individual
factors had significant effect on post-operative major and minor
morbidity. The ROC curves constructed from the final scores of
all patients showed that the areas under the curves of Ganga spine
scores for minor and major morbidities were 0.78 and 0.80 (nearly
80% chance that the score of a morbid case will be greater than nomorbid case) and significant (p<0.001), whereas, the CCI index
produced an area of 0.64 (p<0.01). Based on discriminant analysis,
an overall 74% of major morbid and 71% of minor morbid cases
were correctly classified by Ganga score compared to 67% by CCI.
Validation on randomly chosen 200 cases resulted in an overall
correct classification of 82.8% major morbid and 74% of minor
morbid cases indicating a stable and reliable model. Only age,
ASA, BMI and ambulatory status came out as significant factors
contributing to mortality. ROC analysis produced a significant
curve area of 0.94 and an overall correct classification of 88% cases.
DISCUSSION AND CONCLUSION: The study was able to
determine important factors contributing to post-operative
complications and was able to generate a score based on these
factors, which performed better than CCI. While intra-operative
factors emerged as predominant contributors to morbidity (Table
1), pre-operative comorbidities emerged as significant factors in
identifying mortality. Even though the number of deaths were
much less (six cases), the model used for morbidity performed
even better at discriminating mortality, which is also an important
and required factor that can help a surgeon in making better and
patient condition-based decisions.
Table 1: Strength of association (Kendall’s Tau-b) of individual factors
with major & minor morbidity
Variable
Magnitude
of surgery
factors
Pre-operative
factors
Tau-b
(major
morbidity)
Tau-b
(minor
morbidity)
Critical
Levels
Blood loss
0.21
0.32
> 1400 ml
Duration of surgery
0.18
0.26
> 240 min
Instrumentation
0.17
0.29
> 5 levels
Age
0.15
0.11
> 70 years
ASA
0.14
0.13
> 3rd group
Ambulatory status
0.087
0.19
>= 3rd group
BMI
0.060
0.082
< 18.5
PAPER NO. 80
The Fate of Asymptomatic Cervical Stenosis: A
Prospective Cohort Study
K. D. Riew, MD, Saint Louis, MO
Michael P. Kelly, MD, St Louis, MO
Moon Soo Park, MD, Anyang-Si, Republic of Korea
Carie R. Kennedy, BS, RN, St Louis, MO
INTRODUCTION: The natural history of asymptomatic patients
who have cervical stenosis is not well-defined and the treatment
of such patients remains controversial. As a result, there is
variability in treatment recommendations for such patients. Some
surgeons favor prophylactic decompression in order to prevent a
catastrophic neurological injury, while others favor observation.
Unfortunately, there are few long-term natural history studies that
can provide a scientific rationale for treatment of such individuals.
METHODS: We prospectively enrolled adult patients with spinal
canal AP diameter measuring < 9mm on an MRI with no cord
signal, no symptoms of myelopathy who were willing to participate
in a long-term study with an endpoint of surgical intervention or
neurologic injury. Exclusion criteria: Age over 80 years, pathologic or
traumatic compression, instability requiring stabilization. Enrolled
patients were recommended to have repeat physical exams and MRIs
annually. Anyone who developed myelopathy, cord signal change
or recalcitrant radiculopathy had operative intervention. Our null
hypothesis is that a high percentage of asymptomatic persons
with a spinal canal size ≤9 mm per MRI will become paralyzed
or need operative intervention within a short period of time.
RESULTS: We enrolled 73 patients. The space available for the
spinal cord was between 3-9 mm. Follow up was between 1-12
years (mean 3.7 years; cumulative follow-up of 218.3 patientyears), with 48 patients having a minimum two-year followup (mean 4.6 years, 197.8 patient-years follow up). No patient
became para or tetraplegic. The cumulative follow up of these
patients represents 218.3 patient-years without irreversible
neurologic deterioration. Only eight patients eventually
required surgery (one arthroplasty, two laminaplasties, five
anterior corpectomy/discectomies). Of these, three had
myelopathy, two myeloradiculopathy and three radiculopathy.
DISCUSSION AND CONCLUSION: Few prospective natural
history studies with long-term follow up regarding the cervical
spine exist. To our knowledge, this is the largest prospective
953
study with the longest follow up regarding the natural history
of patients with cervical spinal stenosis without cord signal
change or myelopathy. With over 218 patient-years of follow up,
no one suffered a catastrophic neurologic event or even a minor
neurologic deficit. This suggests that such events are relatively
rare and that most patients can be managed safely with repeat
exams, MRIs and education regarding the signs and symptoms of
myelopathy. However, further follow up is needed to determine if
such a regimen is safe long-term.
PAPER NO. 81
Do Epidural Steroid Injections Affect Outcomes for
Lumbar Stenosis and Degenerative Spondylolisthesis
Patients?
Christopher Kepler, MD, Philadelphia, PA
Jonathan Lurie, MD, Lebanon, NH
James N. Weinstein, DO, Lebanon, NH
INTRODUCTION: The SPORT trial is a prospective, multicenter
study of surgical treatment versus nonoperative treatment
for lumbar stenosis and degenerative spondylolisthesis. The
hypothesis of this subgroup analysis was that patients who
received epidural steroid injections (ESI) during treatment
would have improved outcome and a lower rate of crossover
to surgery compared to patients who did not receive ESI.
METHODS: The study population includes patients enrolled
in SPORT for treatment of spinal stenosis or degenerative
spondylolisthesis who did not receive ESI prior to enrollment in
the study. Patients who received epidural steroid injections during
the first three months of the study were compared to patients
who did not receive epidural injections during the first three
months of the study (No ESI). Change in primary and secondary
outcome measures and treatment effect of surgery were assessed
at baseline, one year, two years, three years, and four years.
RESULTS: In the spinal stenosis cohort, there were 69 ESI patients
and 207 No-ESI patients. There were no significant differences in
demographic factors, baseline clinical outcome scores, or operative
details but there was an increased preference for nonsurgical
treatment among the ESI patients (p<0.001). There was an average
26 minute increase in operative time and an increased length of
stay by 0.9 days in the ESI patients. Averaged over four years, there
was significantly less improvement in SF36 PF in surgically treated
ESI patients (ESI 14.8 vs. No-ESI 22.5, p=0.025). Averaged over
four years, there was significantly less improvement in SF36 BP
(ESI 7.3 vs. No-ESI 16.7, p=0.007) and SF36 PF (ESI 5.5 vs. No-ESI
15.2, p=0.009). Of the spinal stenosis patients assigned to surgical
treatment at enrollment, there was increased crossover associated
with ESI to nonsurgical treatment (ESI 32% vs. No-ESI 11%). There
was also increased crossover of spinal stenosis ESI patients assigned
to nonsurgical treatment to surgery (ESI 58% vs. No-ESI 32%).
In the spondylolisthesis cohort, there were 118 No-ESI patients
and 45 ESI patients. There were significant differences in baseline
SF36 BP, SF36 MCS, and leg pain bothersomeness index favoring
No ESI patients. There were no other significant differences in
baseline demographic factors or clinical outcome scores, but there
was an increased preference for nonsurgical treatment among
the ESI patients (p<0.001). Averaged over four years, there was
significantly less improvement in the nonsurgically treated patients
in SF36 BP (ESI 7.8 vs. No-ESI 17.8, p=0.005), SF36 PF (ESI 4.3 vs.
No ESI 13.1, p=0.005), and sciatica bothersomeness index (ESI
-2.4 vs. No ESI -4.1, p=0.041). There was a trend at four years for
increased reoperation in the ESI patients (ESI 26% vs. No-ESI 15%,
p=0.07). There was no significant difference in crossover with ESI.
DISCUSSION AND CONCLUSION: Despite equivalent baseline
status, the group of patients who received ESI had significantly less
improvement and no evidence of surgical avoidance.
These results were not statistically significant (p=0.632).
DISCUSSION AND CONCLUSION: When addressing long
segments of spinal stenosis with limited areas of instability, there
is no need to extend the fusion to adjacent decompressed levels.
Patients with decompressed but unfused adjacent segments do
show a 63% rate of ASD, but the reoperation rate is low and clinical
outcomes do not differ from those with an absence of ASD.
PAPER NO. 82
Neurologic Recovery after Anterior Cervical
Discectomy and Fusion
Seven Year Clinical and Radiographic Results of
Decompressed But Unfused Adjacent Lumbar
Segments
Zachary Gordon, MD, Lyndhurst, OH
F. Andrew A. Rowan, MD, MS, San Francisco, CA
Christopher G. Furey, MD, Cleveland, OH
INTRODUCTION: Adjacent segment degeneration is a welldescribed consequence of lumbar spinal fusion. However, there
is little information known about the fate of decompressed
segments immediately superior to a fused segment. Extending
the fusion from the unstable segment to all decompressed
segments may be unnecessary and expose the patient to extra
surgical time, blood loss, and complications. A retrospective
review of patients at our institution who had a simultaneous
decompression and fusion with a decompressed segment
immediately superior to the fusion mass was conducted. Longterm clinical outcomes and radiographic results are discussed.
METHODS: From 1998 to 2005, 63 patients at our institution
underwent lumbar decompression and fusion with at least one
segment immediately superior to the fusion segment decompressed
but left unfused. Forty-three were alive and available for follow up.
A questionnaire assessing visual analog scales (VAS) for pain and
function, prescription pain medication use, and a modified SF-36
physical activity and limitations score was sent to each living patient.
Twenty-six patients (60%) responded and were analyzed for the
clinical results. Outcomes for VAS pain, VAS function, medication
use, and SF-36 physical activity scores were evaluated individually,
and then equally weighted to stratify outcomes into one of four
categories: Excellent, Good, Fair, or Poor. The average length of
clinical follow up was seven years (range 2.7 to 10.9 years). Full
radiographic follow up with an average of 3.5 years (range 0.2 to
8.4 years) was available for 19 of the 26 patients who returned the
survey. Postoperative radiographs were compared to preoperative
radiographs for degenerative changes at the adjacent, unfused level.
RESULTS: Overall eight patients had an excellent result, five had a
good result, five had a fair result, and eight had a poor result. Only
one of the 26 survey respondents required an additional operation
(3.8%). One additional patient who was living but did not respond
to the survey went on to reoperation, for an overall reoperation
rate of 4.7%. Average VAS pain scores pre- and post-operatively
were 8.4 and 3.6, showing a 54% reduction in pain (p<0.0001).
A total of 77% of patients reported improvement in function.
Average pre- and post-operative VAS function scores were reported
as 40% and 67% of pre-disease function (p=0.001). Some 65%
of respondents showed a decrease in use of prescription pain
medication. A total of 23% reported an increase in medication
use, but did not have an increase in pain. Some 63% of patients
with full radiographic follow up showed evidence of ASD, with
the one reoperation occurring in a patient with ASD. When ASD
was present there were six excellent or good outcomes, and six
fair or poor outcomes. When ASD was not present there were
two excellent or good outcomes, and five fair or poor outcomes.
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PAPER NO. 83
Charles L. Lehmann, MD, Saint Louis, MO
Jacob M. Buchowski, MD, Saint Louis, MO
Geoffrey Stoker, BS, Saint Louis, MO
INTRODUCTION: Recovery of neurological function is an expected
outcome in patients undergoing anterior cervical discectomy and
fusion (ACDF). The rate of neurologic recovery, however, is not well
described in the literature. Furthermore, the etiology of neurologic
deficits that arise after ACDF is unclear. The purpose of this study is
to describe the natural history of neurological recovery after ACDF.
METHODS: Patients who were 18-80 years of age, diagnosed with
cervical radiculopathy, underwent single-level ACDF between 1/98
and 3/09, and followed for a minimum of two years, were identified
from a prospectively collected database. Sensory and motor
deficits were documented, graded based on physical exam findings
at pre- and postop visits, and used to calculate rates of deficit.
RESULTS: Of 120 included patients, 31% were smokers, there was
a 1.07:1 male to female ratio, the mean age was 45.6±9.3 years, and
the mean follow-up time was 3.9±2.1 years. At the time of surgery,
66% had a sensory deficit (Figure 1). Recovery of sensory function
was seen in 83% of patients by one year. By final follow up, new
sensory deficits developed in 35% of patients of whom 61% had
adjacent level sensory deficits. Interestingly, those patients with
a preoperative sensory deficit were significantly more likely to
develop a new postoperative deficit (p<0.05) (Table 1). At the time
of surgery, 56% had a motor deficit. Recovery of motor function was
seen in 96% of patients by one year, while 17% developed new postop
motor deficits by final follow up. Of the patients who developed
a new motor deficit postop, 80% did so at the adjacent level.
DISCUSSION AND CONCLUSION: A high percentage of patients
with both sensory and motor deficits recover neurological function
during the first year after ACDF. Adjacent level degeneration
appears to be a large contributor to neurological deficits that are
seen in subsequent years.
lead to increased recruitment of osseous precursor cells and
the differentiation of these cells along the osteogenic lineage.
However, the mechanisms of how inflammation stimulates
bone formation during spine fusion are not well understood.
A better understanding of these mechanisms may lead to the
development of novel therapeutic strategies for the treatment
of ankylosis spondylitis or the improvement of bone formation
during spine fusion. The progressive ankylosis protein (ANK)
transports intracellular pyrophosphate to the extracellular
milieu. Lack of ANK function in ank/ank mice results in an
ankylosis spondylitis phenotype. We hypothesized that the
ank/ank mouse model represents a new animal model for
the understanding of the mechanisms of how inflammation
stimulates bone formation and ultimately spine fusion.
METHODS: We utilized a well-established spinal fusion model
using iliac crest allograft in six-week-old ANK-deficient (ank/ank)
mice and wild type (WT) littermates. Mice were followed with weekly
x-rays and groups were euthanized at two and five weeks (n = 5 in each
group). Bone fusion including the size and levels fused was analyzed.
RESULTS: Clinically the ank/ank mice were less mobile and had
a prominent kyphosis, especially after five weeks from surgery.
Unlike the WT mice, ank/ank mice were unable to stand on their
hind limbs. Radiographically the ank/ank mice showed a marked
increase in trabecular bone formation from L2-L5 when compared
to WT littermates after two weeks. After five weeks the iliac crest
allograft was no longer distinguished in the ank/ank mice and a large
trabecular bone mass covering at least three levels was evident (Fig.
1A). The fusion mass in the WT mice was markedly smaller (Fig. 1B).
DISCUSSION AND CONCLUSION: In this study we show for the
first time that ANK plays a crucial role in spine fusion. Lack of ANK
resulted in a larger and more robust spine fusion extending more
levels. Despite our previous findings showing that the lack of ANK
function delays the differentiation of early osteoblasts into mature
osteoblasts causing an osteoporotic bone phenotype in ank/ank
mice, bone formation during spine fusion was increased in ank/
ank mice similar to patients with ankylosis spondylitis. These
findings suggest that an abnormal/chronic inflammatory response
in these mice results in increased bone formation during spine
fusion. Therefore, the ank/ank mice provide a novel animal model
to study the mechanisms of how inflammatory responses cause
increased bone formation during spine fusion. The understanding
of these mechanisms may provide insights into novel therapeutic
strategies for the treatment of ankylosis spondylitis or the
improvement of bone formation during spine fusion.
PAPER NO. 84
The Role of the Progressive Ankylosis Protein (ANK) in
Spine Fusion
Martin Quirno, MD, New York, NY
Kirk A. Campbell, MD, New York, NY
Andrew Yoo, BA, New York, NY
Thomas J. Errico, MD, New York, NY
Thorsten Kirsch, PhD, New York, NY
INTRODUCTION: Spine fusion follows a well-orchestrated
cascade of cellular events that when altered, such as in ankylosing
spondylitis, results in a significant increase in trabecular bone
formation. Increased bone formation ultimately resulting in
spontaneous spine fusion in patients with ankylosis spondylitis
is caused by chronic inflammation. Chronic inflammation can
955
PAPER NO. 85
PAPER NO. 86
Cervical Spondylotic Mielopathy - Minimal 10 Years
Follow Up Study
Congenital Stenosis and Symptomatic Adjacent
Segment Disease in the Cervical Spine
Manuel Ribeiro Da Silva, Porto, Portugal
Nuno Neves, MD, Porto, Portugal
Rui Matos, MD, Porto, Portugal
Pedro C. Rodrigues, Porto, Portugal
Joana Freitas, MD, Gaia, Portugal
Manuel Santos Carvalho, Porto, Portugal
Artur Antunes, MD, Vila Nova De Gaia, Portugal
Rui A. Pinto, MD, Porto, Portugal
Jason Eubanks, MD, Willoughby Hills, OH
Jon Belding, MD, MS, BA, Cleveland, OH
Andrew A. Rowan, MD, MS, San Francisco, CA
Gable B. Moffitt, BS, Cleveland Heights, OH
Vinay Cheruvu, Kent, OH
Justin Hohl, MD, Sandy, UT
Henry H. Bohlman, MD, Cleveland, OH
James Kang, MD, Pittsburgh, PA
INTRODUCTION: Cervical spondylotic mielopathy (CSM) is
the most common cause of spinal cord dysfunction in the adult
population. Treatment implies surgical decompression as soon as
possible after the diagnosis. In this study the authors present the long
term results of minimal 10 years follow up study of 99 patients that
underwent anterior decompression and arthrodesis surgery for CSM.
METHODS: Patients that underwent surgery for CSM between
January 1990 and December 1994 were evaluated for sex, age,
number of levels operated, functional evaluation with Nurick Scale
pre operatively, one year after surgery and at the final the revision
that took place in 2007 and 2008, evidence of consolidation and
complications. All the patients were operated by anterior approach.
T-Student Test was performed with SPSS for statistical analysis.
RESULTS: Ninety-nine patients were evaluated during the study,
73 male, 26 female, with a mean age of 56, six years (42-86) and
mean follow up time of 14,4 years. Three patients died in the
immediate post op period, one in the first year, eight during the
15 year evaluation period. Sixteen patients were operated for one
level, 22 for two levels, 36 for three levels and 22 for four levels
(mean on 2,7±1,0 levels for patient). Pre op Nurick was 3,8±0,9.
There was a significant improvement in neurological condition
after one year surgery (Nurick 2,2±1,1; p<0,001), and between
pre op and final evaluation (2,3±1,2; p<0,001). The degradation
between the first year and the final evaluation was statistically
significant (p=0,004). There was a strong correlation between
age and the number of operated levels (r=0,391, p=0,01), age and
initial neurologic status (r=0,238, p=0,05), initial neurological
status and number of operated levels (r=0,251, p=0,05) and sex and
number of operated levels, with women being operated on for more
levels (r=0,208, p=0,05). There was also e stronger neurological
deterioration between year one and year 15 in young patients when
compared to older ones (r=0,250, p=0,05). There is a strong clinical
relation between first year recuperation and final recuperation
(r=0,838, p=0,01). There was a 100% rate of consolidation.
DISCUSSION AND CONCLUSION: Surgical treatment for
decompression and arthrodesis is considered the best option for
the treatment of CSM in terms of improvement of pain, alignment
and neurological function. A significant neurological improvement
comes from surgery, and despite a significant clinical deterioration
between the first year and the final evaluation, the benefits of
surgery are still evident 15 years after, with a better neurological
status when compared to the pre operative period.
956
INTRODUCTION: Symptomatic adjacent segment disease (ASD)
after anterior cervical arthrodesis can be seen in up to 25% of
patients at 10 year follow up. Some debate exists as to whether this
degeneration represents the natural history of the adjacent disc or
whether the increased biomechanical stresses placed by the fusion
accelerate this degenerative cascade. Congenital stenosis has been
established as an important risk factor in the development of
myelopathy. Further, MRI studies have suggested that congenitally
stenotic spines experience greater pathological changes in the
intervertebral discs and ensuing cord compression than spines
with a normal canal diameter. The current study hypothesized
that patients with congenital stenosis would have an increased
prevalence of symptomatic adjacent segment disease after
anterior arthrodesis than patients with normal canal diameters.
METHODS: A retrospective review was performed on 497 patients
undergoing a one to four level anterior cervical decompression and
fusion by a single surgeon. Radiographs were evaluated for bony
congenital stenosis by measuring the space available for the cord
(SAC) and the Pavlov Ratio (PAV) using the stenosis parameters
described by Kang et al. Radiographic ASD was measured according
to the criteria established by Hilibrand et al. and correlated with
clinically symptomatic ASD evaluated through chart review.
Clinical outcome scores were graded on the Robinson and Odom
criteria. Statistical analysis was performed using student t-tests and
a linear regression model comparing symptomatic adjacent segment
disease among patients with and without congenital stenosis.
RESULTS: Congenital stenosis was observed in 87 (17.5%)
patients. There were 239 men and 255 women in the study
cohort. The average length of follow up was 46.6 months. There
were 227 single level fusions (8 C3/C4, 22 C4/C5, 110 C5/C6,
47 C6/C7), 155 two level fusions (18 C3-C5, 53 C4-C6, 84 C5C7), 84 three level fusions (23 C3-C6, 61 C4-C7), 26 four level
fusions (C3-C7) and a smattering of non-contiguous, multilevel fusions. In the 87 patients with congenital stenosis, 35 had
stenosis at C6 or C7. Pan-cervical stenosis (four or more levels)
was apparent in 27 patients. Of the 497 patients, 188 (37.5%)
developed ASD. Neither age (p=0.78), nor gender (p=0.86),
nor congenital stenosis (p=0.62) correlated with the presence of
clinically symptomatic ASD. Overall, clinical results demonstrated
excellent or good Robinson scores in 86.7% of patients, whereas
excellent or good Odom scores were reported in 90.1% of patients.
DISCUSSION AND CONCLUSION: Congenital stenosis appears
in 17.5% of patients undergoing anterior cervical decompression
and fusion. Despite a predominance of excellent to good surgical
outcomes, symptomatic ASD is common, occurring in 37.5%
of patients at a mean follow up of 47 months. Contrary to our
hypothesis, bony congenital stenosis does not appear to be a
predictor of symptomatic ASD. ASD may represent more the
natural history of the degenerating disc rather than the end product
of underlying biomechanics in the congenitally stenotic cervical
canal or the change in forces created by surgical arthrodesis.
PAPER NO. 87
Does Opioid Pain Medication Use Affect the Outcome of
Patients with Lumbar Disk Herniation?
Roman Isaac, MD, Philadelphia, PA
INTRODUCTION: The SPORT trial is a prospective,
multicenter study of surgical treatment versus nonoperative
treatment for lumbar intervertebral disk herniation (IDH).
The purpose of this study was to review the results of patients
who received opioid pain medications during treatment
compared to patients who did not receive opioid medications.
METHODSThe study population includes patients enrolled in SPORT
for treatment of IDH in combined randomized and observational
cohorts. Patients who were receiving opioid pain medications at
baseline (Opioid) were compared to those who were not (NoOpoid). Outcome measures were assessed at baseline, one year, two
years, three years, and four years. The difference in improvement
between surgical and nonoperative treatment (treatment
effect) was determined at each follow period for each group.
RESULTS: There were 520 patients in the Non-Opioid group
and 542 patients in the Opioid group. At baseline, there was a
significantly higher percentage of patients in the opioid medication
group (p<0.05) on disability, with compensation claims, and
actively smoking. Among the opioid medication group there
were significantly (p<0.001) worse baseline scores for SF36 BP,
SF36 PF, SF36 MCS, SF36 PCS, ODI, Sciatica Frequency Index,
Sciatica Bothersomeness Index, Back Pain Bothersomeness Index,
and percent dissatisfaction with current treatment. There was an
increased percentage of patients in the opioid medication group
with the perception of worsening symptoms (p<0.001). There was
a statistically significant increase incidence of any neurological
deficit (p<0.001), motor weakness (p=0.008), decreased sensation
(p<0.001), and received surgery (p<0.001) in the opioid medication
group. At four years follow up, there were no significant differences
in primary or secondary outcome measures or treatment effect
of surgery between opioid and non-opioid medication patients.
There was significantly less crossover to nonsurgical treatment in
the opioid patients versus the non-opioid patients (11% vs. 19%,
p=0.0108). There was significantly increased crossover to surgery in
the opioid pain medication patients (45% versus 31%, p=0.0045).
DISCUSSION AND CONCLUSION: Despite treatment with
stronger pain medications, patients who were treated with opioids
had significantly worse baseline pain and quality of life. At final
follow up, there was no long term improvement in outcome
associated with opioid pain medication use. Opioid medication
use was associated with increased crossover to surgery. FDA Device
Status: No off label usage is discussed.
PAPER NO. 88
Direct Reduction and Transforaminal Lumbar Interbody
Fusion for High Grade Isthmic Spondylolisthesis
Wael Koptan, MD, Cairo, Egypt
Fady S. Sedra, MSc, MBBS, Hounslow, United Kingdom
Yasser H. El Miligui, MD, FRCS, Cairo, Egypt
Mohammad M. El-Sharkawi, MD, Assiut, Egypt
INTRODUCTION: Several controversies exist over the most
appropriate approach for managing high grade spondylolisthesis.
957
The classic interbody fusions are associated with a considerable
degree of complications. The aim of this work is to determine the
safety and efficacy of unilateral transforaminal lumbar interbody
fusion (TLIF) in managing high grade isthmic spondylolisthesis.
METHODS: The study was conducted between 2000 and 2008 and
included 44 patients with high grade isthmic spondylolisthesis
(Meyerding grades III and IV). The mean age was 24y (range 17
- 38y). All patients had severe back and radicular symptoms that
failed to conservative treatment. Eighteen were at L4/5 and 26 at
L5/S1. Limited decompression, pedicle screw instrumentation
were performed; 21 had additional unilateral TLIF and
direct reduction (Group 1) and 23 had an indirect reduction
and posterolateral fusion using autograft bone (Group 2).
Patients were followed up for an average of 4.5y (range 3 - 7y).
RESULTS: Between Groups 1 and 2, Group 1 had significantly
better ODI improvement (averaged 63% and 58% respectively);
VAS improved significantly more (averaged 93% and 89%
respectively); better anterolisthesis correction (averaged 56%
and 48% respectively); better improvement in disc space
height (averaged 46% and 37% respectively). None in Group
1 had an implant failure and its overall fusion rate was 94%;
Group 2 had two patients with implant failure requiring
revision and an overall fusion rate of 86%. Both groups had a
similar complication rate of 4% including transient foot drop
(one patient in each group) that spontaneously recovered.
DISCUSSION AND CONCLUSION: Direct instrumented
reduction and TLIF is an efficient option to treat high grade isthmic
spondylolisthesis. It provided immediate stability and better
clinical and radiological outcomes.
PAPER NO. 89
Early Diagnosis of Lumbar Spondylolysis in Young
Athletes Using Magnetic Resonance Imaging
Atsushi Kobayashi, MD, Maebashi Gunma, Japan
Tsutomu Kobayashi, MD, Gunma, Japan
Hiroshi Higuchi, MD, Maebashi-Shi, Japan
Kazuo KATOU, MD, Gunma, Japan
INTRODUCTION: Lumbar spondylolysis is a defect of the
pars interarticularis and is considered to be a stress fracture.
Active spondylolysis is a common cause of low back pain in
young athletes. The early stage of spondylolysis is very difficult
to diagnose using plain radiographs, and they often do not
visualize defects seen on computed tomography (CT) scans. In
a recent study, the usefulness of signal changes of the pedicle
on magnetic resonance imaging (MRI) for the early diagnosis
of spondylolysis was evaluated. However, only a few reports
indicated the onset frequency of spondylolysis with MRI in cases
without spondylolysis using plain radiographs. In addition, there
are no validated examination findings for active spondylolysis.
The purpose of this study was to evaluate the usefulness of MRI
for the early diagnosis of active spondylolysis and frequency
of spondylolysis in cases without spondylolysis using plain
radiographs, and to evaluate whether there is any clinical assessment
test assisting in the early detection of active spondylolysis.
METHODS: A prospective cohort design was employed. We
investigated 200 patients who presented to our clinic because of low
back pain between May 2009 and May 2011. The inclusion criteria
in this study were active in sports, and no or unclear spondylolysis
on plain radiographs. There were 144 male and 56 female patients.
The mean age was 14.1 years (range, 10-18 years). All were examined
using plain radiographs and MRI. Only patients who showed a
stress reaction on MRI were examined by CT. Stress reactions were
diagnosed when there was a high signal intensity in the region of
the pars interarticularis on short tau inversion (STIR) axial and
sagittal images on MRI. We assessed the presence or absence of
low back pain at the time of lumbar spine extension, flexion,
knock, or the right/left kemp test as physical examination findings
on the initial consultation of each case. For statistical analysis,
Mann-Whitney’s U test and logistic regression analysis were used.
RESULTS: Because the right and left pars interarticularis were
studied separately, 129 pars interarticularis in 97 subjects (48.5%)
showed evidence of active spondylosis as defined by MRI. CT was
performed in 92 subjects. Based on CT images, these pars defects
were organized into various categories as follows: 52 non-lysis, 37
prefissure, 22 fissure, 10 progressive, and no pseudoarthrosis. The
affected vertebral level was L3 in seven patients, L4 in 29 patients,
and L5 in 61 patients. We could not identify a significant factor
for physical examination findings assisting in the early detection
of active spondylosis. In addition, a case showing pain at the time
of lumbar spine extension described as diagnostic for lumbar
spondylolysis was noted in a group without (90.3%) and in a group
with (88.7%) spondylolysis, and both frequencies were high.
DISCUSSION AND CONCLUSION: The progression of active
spondylolysis to pseudoarthrosis has been associated with an
increased incidence of spondylolisthesis. Moreover, the early
detection and treatment of acute spondylolysis are associated
with improved fracture healing and are important in preventing
progression to established pseudoarthrosis. These results suggest
that MRI is useful for the early diagnosis of active spondylolysis,
and there is high rate of active spondylolysis based on MRI in
young athletes with low back pain in cases without spondylolysis
using plain radiographs. Because there was no significant factor for
physical examination findings in assisting in the early detection
of active spondylosis, even if spondylolysis cannot be detected on
plain radiographs, it is considered that MRI should be employed
for young athletes with low back pain.
PAPER NO. 90
Evaluation of a Center of Excellence Program for Spine
Surgery
Nelson F. SooHoo, MD, Los Angeles, CA
Ateev Mehrotra, MD, Pittsburgh, PA
Elizabeth Sloss, PhD, Arlington, VA
Peter Hussey, Arlington, VA
Susan Lovejoy, Pittsburgh, PA
INTRODUCTION: Medicare and many private health plans are
encouraging patients to seek care at hospitals which are designated
as centers of excellence. Few evaluations of whether the quality of
care at hospitals designated as centers of excellence is better have
been conducted. The Blue Cross Blue Shield Association, whose
member plans insure one in three Americans, has established an
initiative to designate hospitals as centers of excellence for spine
surgery. The objective of our study was to test the hypothesis
that hospitals designated as a spine surgery center of excellence
would provide higher-quality care as demonstrated by a lower rate
of complications and readmissions and, therefore, lower costs.
METHODS: Claims from approximately 54 million enrollees
were retrospectively analyzed. We identified individuals in 20079 who underwent one of three types of spine surgery, one or two
level cervical fusion, one or two level lumbar fusion, or lumbar
discectomy and/or decompression. Our main outcomes were the
composite rate of complication, rates of readmission within 30 days
of discharge, and costs within 90 days following the procedure.
RESULTS: In our sample 29,775 patients had a one or two level
cervical fusion, 27,689 patients had a one or two level lumbar
fusion, and 29,338 patients had a lumbar discectomy and/or
958
decompression. Of the three types of surgery, 33.8%, 33.3%, and
40.2%, respectively, were performed at a hospital designated by
Blue Cross/Blue Shield as a center of excellence for spine surgery.
Designated spine surgery hospitals had a larger number of beds
and were more likely to be an academic center. There were no
significant differences in the risk of complications between patients
having cervical fusion, lumbar fusion, or lumbar discectomy/
decompression at a designated hospital and patients having the
same type of spine surgery at one of the other hospitals. There were
also no significant differences in 90-day index hospitalization costs.
DISCUSSION AND CONCLUSION: On average, hospitals
designated as spine surgery centers of excellence in this program
had similar rates of complications, readmissions, and costs to other
hospitals. Our results emphasize that it is important to empirically
evaluate whether centers of excellence provide higher-quality care.
PAPER NO. 286
Ferromagnetic Interactions and Radiofrequency
Induced Heating of Small Arms Ballistics in MRI
(1.5T,3T,7T)
Russell D. Dedini, MD, San Francisco, CA
Robert T. McClellan, MD, San Francisco, CA
Murat Pekmezci, MD, San Francisco, CA
INTRODUCTION: This study was designed to test the safety of
retained bullets in magnetic resonance imaging (MRI) scanners.
Although limited prior studies suggest retained bullets are
generally safe in 1.5 tesla (T) scanners it is not known if they
are safe in increasingly common 3T and 7T MRI scanners. The
purpose of this study is to analyze the motion as well as heat
generation by retained bullets in different magnetic field strengths.
METHODS: Thirty-nine commercially available bullets
and shotgun pellets were tested in 1.5, 3.0, and 7 Tesla MRI
scanners. The parameters that were measured include the exvivo translational force, rotational force (RF) and RF induced
heating. Translational force in dynes was calculated using a
previously described deflection angle technique and the equation
F=mg*sinØ/cosØ where “F” is the translational force, “m” is the
mass of the object in grams, “g” is the gravitational acceleration
constant (980 cm/sec2) and “Ø” is the deflection angle from
the vertical measured on a protractor. Qualitative assessment of
rotational torque was made using a previously described 0-4 point
scale to describe the force and speed with which each sample
aligned its long axis within the static magnetic field. RF-induced
heating was measured using a custom temperature probe and Fast
Spin Echo T2 weighted sequences designed to simulate worst-case
scenario exposure to the FDA-approved limit of radiofrequency
induced excitation (3.2 watts/kilogram specific absorption rate).
RESULTS: Of 33 bullets and six shotgun pellets tested, only a
single armor-piercing bullet manufactured with a hardened steel
core and two steel pellets were found to be ferromagnetic, with
translational forces in excess of that considered safe in all three
magnetic field strengths. Only a single armor-piercing bullet
demonstrated unsafe rotational torque. RF-induced heating of
0.6°C was measured during the T2-weighted worst-case sequence.
DISCUSSION AND CONCLUSION: Common, commercially
available bullets manufactured in the United States are safe in
MRI scanners up to 7 Tesla in strength. In contrast, armor-piercing
bullets with steel cores and stainless steel shotgun pellets are not
safe. While RF-induced heating occurs, it is minimal, and likely
clinically insignificant. These findings suggest MRI should not be
used when bullets known to contain steel are located very near
to critical anatomic structures and underscores the importance of
obtaining forensic information on retained projectiles whenever
possible.
Peritoneal rent requiring repair
2 (3.5%)
0
Dyspareunia
1 (1.8%)
0
PAPER NO. 287
Incisional Hernia
1 (1.8%)
0
Scrotal/Penile Swelling
1 (1.8%)
0
Complications After Anterior Lumbar Spine Exposure
by a Spine Surgeon With and Without an Access
Surgeon
Micah Smith, MD, Redwood City, CA
Kevin A. Rahn, MD, Fort Wayne, IN
Robert M. Shugart, MD, Fort Wayne, IN
Christopher D. Belschner, PA-C, Fort Wayne, IN
Kary Stout, BS, Fort Wayne, IN
Ivan Cheng, MD, Redwood City, CA
INTRODUCTION: The anterior approach to the lumbar spine
continues to be a useful technique for many pathologies. It seems,
however, that anterior lumbar surgery often places a spine surgeon
in an anatomic territory with which they are unfamiliar. Many
spine surgeons utilize the service of a general surgeon or vascular
surgeon to perform the surgical exposure. A review of the Englishlanguage literature reveals a lack of direct comparison of anterior
spine surgery performed with and without the assistance of an
access surgeon. Purpose: To compare perioperative parameters
and complications in anterior lumbar spine surgery with the
exposure performed by a spine surgeon versus an access surgeon.
Study Design/Setting: A retrospective cohort study of consecutive
patients. Patient Sample: 96 consecutive patients who underwent
anterior lumbar spine surgery between L3-S1 by two spine
surgeons. Outcome Measures: Estimated blood loss, operative
time, length of hospital stay and complications METHODS: A
retrospective review was completed on 96 consecutive patients
who underwent anterior spine surgery between levels L3 and S1
from 1995 to 2008. Patient and surgery characteristics including
demographics, comorbidities, perioperative parameters and
complications were noted. In the first 56 consecutive patients,
a general surgeon completed the exposure with an additional
patient who later had the exposure performed by a general
surgeon due to extensive prior abdominal surgeries. In the next
39 patients, the orthopaedic surgeon completed the exposure.
RESULTSThe group without the assistance of an access surgeon
for the exposure had statistically lower values with respect to
estimated blood loss (204mL vs 420mL, p=0.0007), operative time
(2.8 vs 3.9 hours, p=0.0003) and length of hospital stay (3.5 vs 4.7
days, p=0.0006). In the “with assistance” group, 82% of patients
(47/57) experienced a complication versus 28% (11/39) in the
“without assistance” group (p<0.000001). Major complications
noted in the “with assistance” group included deep venous
thrombus (one), retrograde ejaculation (two), iliac vein bleeding
requiring repair (one) and dyspareunia (one). The most common
minor complication was an ileus that occurred in 33 (58%) of the
patients in the “with assistance” group and in one patient (2.6%)
in the “without assistance” group.
Table. Post-operative complications comparing surgery with an access
surgeon versus without.
With Assistance
n (%)
Without
Assistance n (%)
Ileus
33 (58%)
1 (2.6%)
Deep venous thrombus
1 (1.8%)
0
Retrograde Ejaculation
2 (3.5%)
0
Iliac Vein Bleeding
1 (1.8%)
0
Post-operative Complication
959
DISCUSSION AND CONCLUSION: The approach for anterior
lumbar spine surgery is safe, and a trained spine surgeon who is
knowledgeable and familiar with the anatomy can safely perform
the exposure without the assistance of an access surgeon.
PAPER NO. 288
Coumadin is Associated with Increased Blood Loss and
Transfusion in Lumbar Surgery Despite Preoperative
Correction
Ernest Young, MS, Cleveland Heights, OH
Kasra Ahmadinia, MD, Cleveland, OH
Nicholas U. Ahn, MD, Shaker Heights, OH
INTRODUCTION: Blood loss in lumbar surgery is an established
concern. Previous studies have demonstrated that blood loss is
increased with addition of levels decompressed and/or fused, use
of instrumentation, male sex and advanced age. Prior studies have
demonstrated that prior use of anticoagulants, even when stopped,
can lead to increased surgical blood loss in orthopaedic procedures;
however, the relationship has not been evaluated in spine surgery.
METHODS: A total of 256 consecutive patients who underwent
lumbar decompression were retrospectively divided into two groups
including patients who were taking coumadin prior to surgery, and
a control group with no anticoagulation history. We verified that
patients in the anticoagulation group were reversed prior to surgery
in accordance with accepted guidelines: INR < 1.5 and greater than
one week off of anticoagulants. Operative and hospital records
were obtained to determine intraoperative blood loss (EBL), length
of hospital stay and postoperative transfusion requirements.
RESULTS: Linear regression was used to evaluate the effect of
pre-operative anticoagulation use on EBL as well as hospital stay.
Confounding factors, such as age, sex, race, number of levels
decompressed and number of co-morbidities were corrected for.
A pre-operative history of coumadin led to a significant increase
in blood loss (200cc/level; p = 0.01), transfusion requirements
(0.21units/level; p = 0.05) and hospital stay (0.43days/level; p = 0.02).
DISCUSSION AND CONCLUSION: Our results indicate that even
with adequate reversal, patients on anticoagulants prior to lumbar
surgery have increased blood loss, tranfusion requirements and
hospital stay. This is particularly important given the increasing
number of anticoagulated patients. The results of this study will
allow the surgeon to better counsel patients regarding blood loss
and will allow the surgeon to be better prepared for blood loss in
patients with a history of anticoagulation use.
PAPER NO. 289
Timing of Thromboembolic Chemoprophylaxis in
Postoperative Spinal Trauma Patients
Lloydine Jacobs, MD, Pittsburgh, PA
Justin Hohl, MD, Sandy, UT
Joon Y. Lee, MD, Pittsburgh, PA
INTRODUCTION: There is a paucity of literature available
addressing the safety and efficacy of chemoprophylactic agents
in postoperative spinal trauma patients. Because of this, there is a
large degree of variability regarding administration of these agents.
Most surgeons agree that patients with substantial risk factors for
development of thromboembolic complications should receive
postoperative chemoprophylaxis, but there remains no consensus
regarding the optimal time for initiation of these agents. The
purpose of this study was to review the timing of thromboembolic
chemoprophylaxis in postoperative spinal trauma patients as
well as the risk of hemorrhagic and thromboembolic events.
METHODS: A retrospective analysis of 252 spinal trauma surgical
patients was conducted at a level 1 trauma center from 2009-2010. Data
collected included patient demographics (age, gender, body mass
index), use of postoperative thromboembolic chemoprophylaxis,
time to initiation of chemoprophylaxis, the incidence of bleeding
complications (epidural hematoma, wound drainage and wound
hematoma) and the incidence of thromboembolic complications
(deep venous thrombosis (DVT) and pulmonary embolism (PE)).
RESULTS: The study population consisted of 163 males (65%)
and 89 females (35%). The average age was 50 years and the
average BMI was 27.3. All patients received sequential compression
devices or thromboembolic deterrent stockings with or without
chemoprophylaxis postoperatively. A total of 204 patients (80%)
received chemoprophylaxis. The average time to initiation
of chemoprophylaxis was 2.5 days. No patients developed
epidural hematoma (0%), nine patients (3.5%) developed
wound drainage requiring surgical irrigation and debridement
and one patient developed a superficial wound hematoma
(0.3%) requiring surgical drainage. Postoperative DVT was
diagnosed in 13 patients (6.3%) during their hospital stay. Five
patients developed PE (1.9%). The average time to initiation of
chemoprophylaxis in patients who developed thromboembolic
complications was three days, while the average time to
initiation in patients without evidence of thromboembolism
was 2.5 days. All patients that developed DVT and PE were
treated with both mechanical thromboembolic prophylactic
devices in addition to chemoprophylaxis prior to diagnosis.
DISCUSSION AND CONCLUSION: The incidence of hemorrhagic
and thromboembolic complications in this series was similar to
that reported in the literature. The results of this study suggest that
initiating thromboembolic chemoprophylaxis in postoperative
spinal trauma patients at 2.5 days postoperatively may be a safe
protocol. Although this timing of chemoprophylaxis did not lead
to any epidural hematomas, there was a significant rate of wound
drainage that may be attributable to chemoprophylaxis. In 252
spinal trauma patients who had postoperative thromboembolic
chemoprophylaxis initiated 2.5 days after surgery there were no
epidural hematomas, but 3.5% of patients had draining wounds
that required surgical irrigation and debridement. Larger studies
are necessary to further evaluate the optimal timing for initiation
of chemoprophylaxis.
PAPER NO. 290
The Seasonality of Postoperative Infection in Spine
Surgery
Jordan Gruskay, Philadelphia, PA
Jeremy S. Smith, MD, Irvine, CA
James Harrop, MD, Philadelphia, PA
Alexander Vaccaro, MD, PhD, Gladwyne, PA
INTRODUCTION: Seasonality of infection rates is a well-known
phenomenon. Previous studies have found an association with
the summer months and an increased rate of infection. The
elevated temperature and humidity of these months is often
960
cited as being responsible for this increase. The “July Effect,”
a hypothesis that the inexperience of new housestaff at the
beginning of an academic year leads to an increase in wound
complications, has also been considered. Finally, an increase in
trauma-related admissions in the summer months likely results
in an increased incidence of postoperative infections. Previous
studies have revealed mixed results concerning perioperative
spinal wound infections in the summer months. This study
seeks to determine whether there is significant variation in
postoperative spinal infection rates over the course of the year.
METHODS: All spine surgery cases at a single tertiary referral
institution in a five-year period between January 2005 and
December 2009 were reviewed. A total of 8,120 cases were
included. Patients presenting with a contaminated wound or
active infection were excluded. Postoperative infections presenting
within 30 days for simple decompressions and one year for spinal
fusion were identified by the Division of Infectious Diseases using
Center for Disease Control (CDC) guidelines. Infection rates
were calculated on a monthly and seasonal basis and compared.
RESULTS: A statistically significant increase in infection rate was
present on both a seasonal and monthly basis (p = 0.03 and 0.024
respectively) comparing the periods of seasonal change from
spring to summer. A significant decrease in infection rate was seen
on a seasonal basis during the change from fall to winter (p = 0.04).
The seasonal rate of infection was highest in the summer (4.1%)
and decreased to the lowest point in the spring (2.8%) (p = 0.03).
DISCUSSION AND CONCLUSION: At this tertiary referral
institution, spine surgery cases performed during the summer and
fall months were associated with a significantly higher incidence
of surgical wound infection compared to the winter and spring.
Infection rates reached their peak during the summer months
(July, August and September) and fell to their low point in the
spring (April, May, June). This data supports the existence of a
seasonal effect on perioperative spinal infection rates, which may
be explained by seasonal variation in weather patterns and in
housestaff experience.
PAPER NO. 291
Risk Factors for Heterotopic Ossification in Patients
with Spinal Cord Injury: A Case-Control Study
Mustafa Citak, MD, Bochum, Germany
Eduardo M. Suero, MD, New York, NY
Manuel Backhaus, MD, Bochum, Germany
Renate C. Meindl, SR, MD, Bochum, Germany
Thomas A. Schildhauer, MD, Bochum, Germany
INTRODUCTION: Spinal cord injured patients have a high
risk of developing heterotopic ossification (HO), with an
incidence varying from 1% to 50%. Although the incidence
of HO after spinal cord injury is relatively high, the exact
etiopathogenesis is still unknown. Therefore, we designed a
case-control study to analyze the risk factors associated with the
development of HO in patients with traumatic spinal cord injury.
METHODS: Patients who were treated for a traumatic spinal cord
injury (SCI) in our hospital, and who subsequently developed
HO, were identified by querying the electronic database at our
hospital from January 2002 through December 2010. Onehundred and thirty-two patients met the inclusion and exclusion
criteria and were included in the study. From the same database,
we randomly selected a control group of patients over the
age of 18, who were treated for traumatic SCI and who did not
develop HO. Our primary outcome measures were the risk of
developing HO according to whether the patient had suffered
from (1) a complete spinal cord lesion (ASIA A); (2) tetraplegia or
paraplegia; (3) cervical, thoracic or lumbar injury; (4) severe chest
trauma; and (5) the time interval between injury and surgery.
Secondary risk factors explored were: patient age; sex; presence
and number of co-morbities; length of hospital and intensive
care unit (ICU) stay; associated traumatic injuries; type of
surgical procedure; presence of spasticity 13, pressure ulcers, deep
venous thrombosis and urinary tract infection; and pulmonary
complications, such as pneumonia and necessity of tracheostomy.
RESULTS: Level of injury (paraplegia or tetraplegia) and time
interval between injury and surgery did not influence the
development of HO. However, patients with a complete lesion
had an approximately six-fold increased risk of developing HO.
Patients with lumbar lesions had a lower risk of developing HO.
An approximately two-fold increased risk of HO development was
found in patients with associated thoracic trauma. No differences
in age, gender and mean length of hospital or ICU stay were found
between the cases and controls. Patients with associated spasticity,
pneumonia, presence of tracheostomy and urinary tract infection
had a higher risk of developing HO. Fewer comorbidities were
found in patients with HO. However, smokers had approximately
a three-fold increased risk of developing HO. Associated head/
brain injuries, upper limb injuries, lower limb injuries, abdominal
trauma, pelvic trauma, pressure ulcers and deep vein thrombosis, as
well as the type of surgery, did not influence the development of HO.
DISCUSSION AND CONCLUSION: This is the largest study
to date evaluating the risk factors for developing HO following
traumatic spinal cord injury. Based on our data, we believe that
inflammatory processes play an important role in developing
HO. Interestingly, patients with associated pneumonia, thoracic
trauma and necessity of tracheostomy had a higher risk of HO
development. Smokers also had a higher risk of HO development.
All those factors are associated with inflammatory reactions of the
lung, which might be a key factor for HO development. It is also
known that lung disease may lead to new bone formation. Various
possible mechanisms for this effect have been proposed, including
nerve stimulation, secretion of growth factors and overproduction
of prostaglandin E2. Our study adds valuable new information
to the literature and could guide further clinical and laboratory
studies analyzing the development of HO in SCI patients.
PAPER NO. 292
uSubsidence and Osteolysis in Patients undergoing
ALIF with and without rhBMP-2 Graft Augmentation
Eugene Carragee, MD, Redwood City, CA
Michael S. Wildstein, MD, Charleston, SC
INTRODUCTION: Fusion with rhBMP-2 has been associated
with increasing rates of rhBMP-2 associated complications
which were not reported in the original industry-sponsored
trials. These complications have included osteolysis, implant
subsidence and migration, inflammatory cyst formation,
radiculitis and retrograde ejaculation. Few controlled trials
unassociated with the device manufacturer have been reported.
METHODS:
Consecutive
patients
having
unilateral
transpedicular screw instrumentation and anterior lumbar
interbody fusion (ALIF) with a femoral ring allograph for
degenerative conditions or isthmic spondylolisthesis: comparing
outcomes with (after 6/2003) and without (before 6/2003)
rhBMP-2 in (ALIF) were compared using a protocol follow up
by independent examiner and blinded radiographic review.
RESULTS: Early subsidence, endplate erosion, loss of distraction,
loosening of pedicle screw constructs and reoperation were greater
in the rhBMP-2 group (p < 0.01). In 25 males there were three
episodes of retrograde ejaculation in the rhBMP-2 group, two of
961
which resolved; in 29 males there were no episodes in the control
group. (p = 0.09) Final pain scores, Oswestry Disability Index,
medication intake and occupational duties were all trended worse
in the rhBMP-2 group (p 0.1 - 0.05). Reoperation rate was higher
in the rhBMP-2 group (p = 0.05) and occurred predominantly in
women. The incidence of solid fusion was higher in the rhBMP-2
group at one year (p = 0.06), two years (0.17) but not at five years.
Earlier return to work (RTW) was not different in either group,
but there was a trend to earlier RTW in the rhBMP-2 group who
did heavy labor (p = 0.21). Satisfaction with surgery was higher
in the control group compared with the rhBMP-2 group (p=0.02).
DISCUSSION AND CONCLUSION: This is one of the few controlled
studies of rhBMP-2 reported by nonindustry-sponsored authors.
In our experience, the use of rhBMP-2 in single or double level
ALIF with unilateral posterior instrumentation has a greater loss
of initial alignment, implant subsidence and reoperations than use
of the same construct without rhBMP-2. This effect was greater in
especially in women and may relate to early osteolysis in less dense
bone. The addition of rhBMP-2 had a modest benefit with earlier
radiographic fusion, however, this extremely expensive additional
intervention did not improve ultimate clinical outcomes or patient
satisfaction. Retrograde ejaculation risk in men may be increased
with rhBMP-2 use in a retroperitoneal approach to the lower
lumbar spine. The value added for use of this additional, expensive
drug/implant was overall negative. Value may be improved if use
is selectively directed to subjects with more metabolic morbidity
(e.g. predisposing to union) or local pathologic risk of non-union
(e.g. revision or avascular necrosis of bone) or longer constructs.
PAPER NO. 293
Chronic Antiplatelet Use is Associated with Increased
Blood Loss in Lumbar Surgery Despite Adherence to
Protocols
INTRODUCTION: Preoperative use of antiplatelets is of
particular concern in lumbar surgery in which blood loss tends
to be significant. In order to minimize this risk, platelet inhibitors
such as aspirin and clopidogrel bisulfate are discontinued seven
days prior to surgery. This study was performed to determine
if blood loss and transfusion requirements during lumbar
surgery reach normal levels if these guidelines are followed.
METHODS: We retrospectively reviewed the records of 490
consecutive subjects who had undergone lumbar decompression
with or without fusion and instrumentation. Patients with
underlying coagulopathies or neoplastic disease were excluded
from this study. Age, sex, intraoperative blood loss, transfusion
requirements, chronic use of antiplatelets, number of levels
decompressed, number of levels fused and use of instrumentation
were recorded from patient files. Patients were separated into
groups based on the current use of antiplatelets and into a
control group with no history of antiplatelet therapy. Multivariate
ANOVAs correcting for the above variables, and Chi-Square tests
were used to determine differences in blood loss and the need
for transfusion in patients who were taking chronic antiplatelets.
RESULTS: Significant differences between patients using clopidogrel
bisulfate were seen in mean blood loss per decompressed level (772cc
vs. 964cc, p=0.02), per fused level (932cc vs. 1089cc, p=0.05) and
per instrumented level (926cc vs. 1126cc, p=0.02). Additionally,
differences between patients using aspirin and those not were seen
in mean blood loss per fused level (924cc vs. 1054cc, p<0.01) and
per instrumented level (914cc vs. 1084cc, p<0.01). Clopidogrel
bisulfate and aspirin were associated with increased requirement
for intraoperative transfusion (OR 3.35, p<0.01, OR 2.28, p<0.01).
DISCUSSION AND CONCLUSION: The chronic use of antiplatelet
medications appears to increase surgical blood loss and transfusion
requirements in patients undergoing lumbar surgery despite
adherence to protocols and measures to stop the usage of these
drugs prior to surgery. This increases the potential complications in
this patient population. Extra care should be taken in these patients
and surgeons should be aware of the potential for increased blood
loss and transfusion requirements.
PAPER NO. 294
Prospective, Randomized Study of Surgical Site
Infections with One Year Follow Up
Richelle C. Takemoto, MD, New York, NY
Pedro Ricart Hoffiz, MD, MS, Valhalla, NY
Tate Andres, BS, New York, NY
Jeffrey A. Goldstein, MD, New York, NY
Jeffrey M. Spivak, MD, New York, NY
John A. Bendo, MD, New York, NY
Baron Lonner, MD, New York, NY
INTRODUCTION: Drains that are left in place for a prolonged
period of time have a higher rate of bacterial contamination.
However in spinal surgery if a drain has a significantly high output,
it may be left in place for a longer period of time. Spinal surgery has
a higher incidence of infection than other orthopaedic procedures
and it has been shown that the use of a drain can help prevent
infections. Given the significant consequences of an infection
following spine surgery and the lack of data with regards to the use
of antibiotics and drains, the purpose of our study was to compare
infection rates in patients who were treated with antibiotics
for 24 hours versus the duration of time the drain is in place.
METHODS: A total of 363 patients who underwent thoracolumbar
spine surgery requiring a post-operative drain were enrolled
and randomized into two groups: one group receiving 24
hours of perioperative antibiotics (24) and one group receiving
antibiotics for the duration (DUR) that the drain was in
place. Data collected included demographics, medical comorbidities, type of spine surgery and surgical site infection.
These patients were prospectively followed for one year.
RESULTS: A total of 24/172 (12.2%) in the 24 group developed
a surgical site infection while 23/144 (13.8%) in the DUR group
were found to have a surgical site infection. The differences
between each group were not significant (p=0.754). There were
no significant differences between the groups with respect to
demographics, surgical time, type of surgery, drain output
or length of stay. Five patients in the 24 group developed
delayed infections whereas one patient in the DUR group
developed a late infection. This was not significant (p=0.321).
DISCUSSION AND CONCLUSION: Continuing peri-operative
antibiotics for the entire duration a drain is in place after spine
surgery does not confer additional protection against infection
than 24 hour antibiotic administration in patients with one year
follow up.
962
PAPER NO. 295
Incidence and Risk Factors for Venous
Thromboembolism after Spine Surgery
Katsuhito Yoshioka, MD, Atlanta, GA
Takeshi Oshima, Kanazawa, Japan
Hideki Murakami, MD, Kanazawa, Japan
Satoru Demura, MD, Kanazawa, Japan
Yoshiyasu Fujimaki, MD, Kanazawa, Japan
Satoshi Kato, MD, Kanazawa, Japan
Takashi Ota, MD, Kanazawa, Ishikawa, Japan
Kazuya Shinmura, MD, Ishikawa, Japan
Hiroyuki Tsuchiya, MD, Kanazawa, Japan
INTRODUCTION: Previously reported incidence and risk
factors for venous thromboembolism (VTE) include various
kinds of disease and different types of spine surgery. However,
there has been no comparative study on VTE after spine surgery.
The goal of this study is to demonstrate the incidence and
identify the associated risk factors of VTE after spine surgery.
METHODS: Four groups of patients were included in this study: 1) 82
patients with spine tumor treated with total en bloc spondylectomy
or piecemeal excision with stabilization were defined as the tumor
group; 2) 90 patients with lumbar and/or thoracic degenerative
disease treated with spinal fusion were defined as the fusion
group; 3) 79 patients with lumbar spinal stenosis treated with
decompression without fusion were defined as the decompression
group; 4) 89 patients with cervical degenerative disease treated
with decompression and/or fusion were defined as the cervical
group. All 340 patients received mechanical prophylaxis, including
compression stocking and intermittent pneumatic compression
devices, and all were examined with duplex ultrasonography
assessments of both lower extremities and with lung perfusion
scintigraphy seven to 10 days after surgery. If VTE was suspected,
the patient underwent multidetector CT venography. The incidence
of VTE was evaluated in relation to the tumor, operative time,
intraoperative blood loss, obesity (body mass index), duration of
bed rest and neurologic deficit. Statistical analysis was performed
using the χ2 test, the Mann-Whitney U-test and the Fisher exact test.
RESULTS: The overall incidence of VTE was 14.1% (48/340 patients).
Distal thrombi were identified in 35, of whom 88.6% (31/35
patients) had thrombi in the soleus vein (seven patients bilateral,
15 in the left, nine in the right). Proximal thrombi were identified
in six patients. Some 2.9% (10/340 patients) showed pulmonary
embolism (PE), and in six of these 10, no deep venous thrombosis
(DVT) was found. In the tumor group, 6.1% (5/82 patients)
showed PE. The incidence of symptomatic PE was 0.59% (two/340
patients). Statistically significant was found in the existence of a
tumor (P=0.023), operative time (P=0.020) and intraoperative
blood loss (P=0.005). The incidence of VTE was 24.4% (20/82
patients) in the tumor group, 13.3% (12/90 patients) in the fusion
group, 15.2% (12/79 patients) in the decompression group and
4.5% (four/89 patients) in the cervical group. The cervical group
has a low risk of VTE (P<0.05). Operative time, intraoperative
blood loss, obesity, duration of bed rest and neurologic deficit
were not risk factors in any of groups. The incidence of VTE in
the tumor group with more than 1000ml intraoperative blood
loss indicated at the high rate of 33.3% (eight/24 patients).
DISCUSSION AND CONCLUSION: This study shows that surgery
for spine tumor has a high risk of VTE, especially associated with
intraoperative blood loss. Cervical spine surgery has a low risk of
VTE when compared with other groups studied. The decompression
group indicated the same level incidence of VTE as the fusion
group. No DVT was found in six of 10 patients with PE. This result
indicates that screening for VTE using only duplex ultrasonography
assessments is less than satifactory. Lung perfusion scintigraphy or
multidetector CT venography is also needed for the screening of
PE high risk patients such as spine tumor surgery associated with
intraoperative blood loss.
PAPER NO. 297
How Much Can Preoperative Embolization Decrease
Blood Loss During Palliative Surgery for Spinal
Metastasis?
Jordan Gruskay, Philadelphia, PA
Jeremy S. Smith, MD, Irvine, CA
Hiroyuki Hayashi, MD, Kanazawa, Japan
Kei Inoue, PhD, Kanazawa, Japan
INTRODUCTION: Postoperative wound infection is the most
common complication following spinal surgery. The incidence
reported in the literature varies from 0.5% to 20%. The addition
of instrumentation, use of preoperative prophylactic antibiotics,
length of procedure and intraoperative blood loss have all been
found to influence infection rate. No previous study, however, has
attempted to correlate the case order with infection risk after surgery.
METHODS: We reviewed all spine surgery cases at this institution
between January 2005 and December 2009. Subjects were classified
into four categories: fusion, laminectomy, tumor or preoperative
infection. Postoperative infections were identified by the Division
of Infectious Diseases. Hospital-acquired infections were defined
as those occurring postoperatively within 30 days for simple
decompressions and one year for fusions per CDC guidelines. Case
order was determined, with each procedure labeled one to five
depending on the number of previous cases in the room. Variables
such as the American Society of Anesthesiologists (ASA) score,
number of operative levels, wound class, age, sex and length of
surgery were also tracked. A step-down binary regression was used
to analyze each variable as a potential risk factor for infection.
RESULTS: A total of 6,666 surgical procedures were analyzed
including 5,023 fusions and 1,643 decompressions. Patients
with tumor, traumatic injury or a active infection were excluded.
Decompression cases had a 2.4% incidence of infection. Longer
surgical time (OR 1.02 (1.009-1.022), p<0.001), and higher case
order (OR 1.88 (1.20-2.93), p=0.005) were found to be significant
risk factors for lumbar decompressions. Fusion cases had a 3.5%
incidence of infection. Analysis of cervical fusions showed
that the posterior approach (OR 15.4 (6.6-35.8), p<0.001) and
revision cases (OR 2.2 (1.18-4.1), p=0.013 were significant risk
factors for infection. For lumbar fusion cases, longer surgical
time (OR: 1.002 (1.001-1.004), p=0.021), higher ASA score
(OR: 1.68 (1.14-2.48), p=0.009) and older age (OR 1.024 (1.011.04), p=0.005) were all significant risk factors for infection.
DISCUSSION AND CONCLUSION: Decompressive procedures
performed later in the day carry a higher risk for postoperative
infection although no similar trend was shown for fusion
procedures, possibly due to the high inherent risk of infection and a
tendency to perform complicated fusion cases early in the day. Our
results identify potential modifiable risk factors contributing to
infection rates in spinal procedures. Specific risk factors, although
not defined in this study, might be related to contamination of
the operative theater, cross contamination between healthcare
providers over the course of the day, use of flash sterilization and
mid-day shift changes. Although this data is limited to spinal
procedures, our findings have potential implications for infection
control in all surgical disciplines.
INTRODUCTION: Palliative posterior decompression and
instrumentation surgeries for spinal metastasis are effective
in improving quality of life by providing good pain control
and neurologic improvement. Preoperative transarterial
embolization is usually performed because excessive blood
loss is one of the main complications during the surgery.
Hitherto, there have been some studies carried out to evaluate
the effectiveness of preoperative transarterial embolization
in devascularizing theses tumors. However, none of these
studies have measured the effect of transarterial embolization
on intraoperative blood loss in a single operative procedure.
The purpose of this study was to evaluate the effectiveness of
preoperative transarterial embolization in palliative posterior
decompression and instrumentation surgery for spinal metastasis.
METHODS: Forty-five patients were included in this study.
Between 2000 and 2010, the patients underwent a palliative
posterior decompression and instrumentation as the primary
surgery for spinal metastasis in thoracolumbar spine. Not all of
the patients had bleeding diathesis. One to three vertebral levels
were decompressed by laminectomy and aggressive debulking
of vertebral tumor. Five to seven vertebrae were stabilized using
posterior instrumentation. Preoperative transarterial embolization
was carried out on 23 patients (embolization group). In the
embolization group, the primary tumors were in lung (seven
patients), breast (four patients), kidney (four patients), prostate
(two patients) and the others (six patients). The surgeries were
carried out within three days after the embolization. The embolic
materials used were gelatin sponge, polyvinyl alcohol foam and
metallic coils. The other 22 patients did not have the embolization
(no embolization group). In the no embolization group, the
primary tumor were in lung (eight patients), prostate (three
patients), colon (three patients), breast (two patients), thyroid
(two patients), kidney (one patient) and the others (three patients).
RESULTS: Angiography and embolization was performed in all
23 patients in the embolization group without causing neurologic
deficit, skin or muscle necrosis. The pain and neurologic
symptoms in all 45 patients were relieved after their surgery.
The average intraoperative blood loss was 520 ml (range, 1401380 ml) in the embolization group. This is significantly lower
than 1059 ml (100- 3260 ml) in the no embolization group
(p<0.05). In the embolization group, the intraoperative blood
loss was not correlated with tumor vascularization degree,
embolization degree and time between embolization and surgery.
DISCUSSION AND CONCLUSION: The intraoperative blood loss,
after preoparative transarterial embolization, was measured to be
about the half of the intraoperative blood loss measured without
preoperative arterial embolization.
PAPER NO. 296
The Correlation Between Frequency of Surgical Site
Infections and Surgery Case Order
963
PAPER NO. 298
PAPER NO. 299
MRI Findings and Decision Making on Implant
Removal in Deep Wound Infection after Lumbar Spinal
Instrumentation
Risks of Spinal Surgery in Dialysis-dependent Patients:
Analysis of a National Administrative Database
Masahiro Kanayama, MD, Hakodate, Japan
Daisuke Togawa, MD, Hakodate City Hokkaido, Japan
Tomoyuki Hashimoto, MD, Hakodate, Japan
Keiichi Shigenobu, MD, Hakodate, Japan
Fumihiro Oha, MD, Hakodate, Japan
INTRODUCTION: The objectives of this study were
to retrospectively review the treatment of deep wound
infection after instrumented lumbar fusion, and thereby
to advocate appropriate strategy for deep wound infection.
METHODS: A total of 1,219 consecutive patients who underwent
instrumented lumbar fusion were reviewed retrospectively. Type
of surgery was posterior lumbar interbody fusion (PLIF) in 837
patients, posterior lumbar fusion (PLF) in 247, transforaminal
lumbar interbody fusion (TLIF) in 113 and posterior fusion in 22
patients. There were 15 deep wound infections (1.2%) requiring
surgical treatment. MRI images were used to evaluate the presence
or absence of osteomyelitis of instrumented vertebra (Figure:
diffuse low signal intensity of instrumented vertebra in T1weighted images) and intervertebral abscess (Figure: high signal
intensity of cage-inserted disc space in T2-weighted images).
RESULTS: Of 15 deep wound infections, nine patients (60%)
underwent implant removal. All of them showed evidence of
spondylodiscitis in MRI. Two patients developed spinal instability,
but were successfully treated by redoing spinal reconstruction.
Six patients (40%) underwent debridement and wound irrigation
without implant removal. Four of them did not show evidence
of spondylodiscitis in MRI, and finally achieved a solid fusion.
However, the remaining two patients with MRI findings of
spondylodiscitis lost fixation stability due to screw loosening,
and showed progressive destruction of instrumented vertebra.
DISCUSSION AND CONCLUSION: The current study showed that
inappropriate retaining of spinal implant frequently complicated
postoperative wound infection. Once evidence of osteomyelitis
of instrumented vertebra or intervertebral abscess was found in
MRI, all the spinal implant should be removed. Otherwise, loss of
fixation stability due to screw loosening and progressive vertebral
bone destruction might eliminate feasibility of future spinal
reconstruction.
Hirotaka Chikuda, MD, PhD, Tokyo, Japan
Hideo Yasunaga, MD, PhD, Tokyo, Japan
Katsushi Takeshita, MD, Tokyo, Japan
Hiroshi Kawaguchi, MD, Tokyo, Japan
INTRODUCTION: Spine surgery in dialysis-dependent
renal failure patients remains a clinical challenge.
Impact of dialysis-dependency on perioperative risks
following spine surgery has not been fully understood.
METHODS: We analyzed abstracted data from the Diagnosis
Procedure Combination database, a national administrative
database in Japan. The survey is conducted annually for the sixmonth period between July 1 and December 31. The data of
years 2007 and 2008 were used. We included all patients who
had undergone any combination of laminectomy, laminoplasty,
discectomy and/or spinal arthrodesis. We compared the rates of inhospital death and major complications between non-dialysis and
dialysis-dependent patients. We further performed multivariate
logistic regression analyses to adjust for confounding items.
RESULTS: We identified 51,648 eligible patients (30,743 men
and 20,905 women; mean age, 62 years), including 869 (1.7%)
dialysis-dependent patients. Dialysis-dependent patients had
a significantly higher in-hospital mortality than non-dialysis
patients (3.57% vs 0.35%; p<0.001). Rates of cardiac events,
sepsis and respiratory complications were also significantly
increased in dialysis-dependent patients. After adjustment,
dialysis-dependent patients reMEd at 10-fold higher risk of
in-hospital death (odd ratio, 9.81; 95% confidence interval
5.96 to 16.29; p<0.001). Dialysis-dependent patients were
also at higher risk of postoperative major complications (odd
ratio, 2.43; 95% confidence interval 1.88 to 3.15; p<0.001).
DISCUSSION AND CONCLUSION: Our analysis of data on
>50,000 patients revealed that dialysis-dependent patients had
10-fold higher risk of in-hospital death than non-dialysis patients.
These patients were also more likely to have major complications
such as cardiac events, sepsis and respiratory complications.
PAPER NO. 300
Prophylactic Operative Site Powdered Vancomycin and
Postoperative Deep Spinal Wound Infection
Robert W. Molinari, MD, Pittsford, NY
William J. Molinari, III, MD, Rochester, NY
Oner Khera, MD, Glendale, AZ
INTRODUCTION: Deep surgical wound infection after spinal
surgery can result in higher postoperative morbidity, mortality, and
healthcare costs. While prophylaxis in the form of perioperative
intravenous antibiotic use has demonstrated to reduce the incidence
of deep infection, other intraoperative adjunctive measures
have not been sufficiently evaluated in the existing literature.
Powered forms of antibiotics which are deposited directly into
the spinal surgical wound prior to closure may be successful
means to reduce postoperative deep spinal wound infection.
Directly depositing the powdered form of the antibiotic into the
operative site theoretically achieves the highest levels of antibiotic
concentration in the spinal wound. The purpose of this study is
to evaluate the effect of intraoperative powdered vancomycin
on the rates of postoperative deep spinal wound infection.
METHODS: During the period from 2005-2010, 1,512 consecutive
adult spinal surgery cases were performed by the same fellowship-
964
trained spinal surgeon at a level one trauma center. One gram
of powdered vancomycin was placed in all surgical sites prior to
wound closure. A total of 849 cases were uninstrumented, 443
cases were instrumented posterior thoracic or lumbar, 27 were
instrumented anterior thoracic or lumbar, 146 were instrumented
anterior cervical and 47 were instrumented posterior cervical. A
retrospective operative data base and medical record review was
performed to evaluate for evidence of postoperative wound infection.
RESULTS: Thirteen of the 1,512 patients (0.86%) were identified
as having evidence of postoperative deep wound infection. All
13 patients had reoperation for wound irrigation, debridement
and reclosure. Staph aureus and MRSA were the most commonly
identified organisms (10/13 cases). The rate of deep wound
infection was 0.90% (6/663) for instrumented spinal surgeries,
and 0.82% (7/849) for uninstrumented surgeries. Deep infection
occurred in only 0.93% (3/324) of multilevel instrumented
posterior spinal fusions, 0.73% (1/73) of open posterior lumbar
interbody fusion procedures, and 0.81% (1/81) of single-level
instrumented posterior fusions. Deep infection was not observed
in any patient who had uninstrumented spinal fusion (0/162).
Increased rates of complications related to powered vancomycin use
were not identified in this series. (Tables 1& 2) DISCUSSION AND
CONCLUSION: In this series of 1,512 consecutive spinal surgeries,
the use of 1 gram of powdered intraoperative vancomycin placed
in the wound prior to wound closure appears to be associated with
a low rate deep spinal wound infection in both instrumented and
uninstrumented cases. Rates of deep infection for instrumented
fusion surgeries appear to be among the lowest reported in the
existing literature. Further investigation of this technique using the
case-controlled methodology with larger surgical subpopulations
is needed.
Table 1. Rates of Deep Wound Infection
Uninstrumented spinal surgeries
0,82% (7/849)
Uninstrumented spinal fusion
0% (0/162)
Instrumented spinal surgeries
0.90% (6/663)
Multilevel instrumented psf
0.935 (3/324)
Open PLIF procedures
1.37% (1/73)
Single-level instrumented psf
1.23% (1/81)
Single-level posterior decompression
0.40% (1/249)
Multi-level posterior decompression
1.00% (6/600)
Anterior cervical fusion
0% (0/146)
Posterior cervical fusion
2.13% (1/47)
Table 2. Deep Infection Rates by Study Year
2005
1.14% (2/175)
2006
1.50% (3/200)
2007
1.18% (3/254)
2008
0.36% (1/275)
2009
0.98% (3/306)
2010
0.33% (1/302)
965
PAPER NO. 451
Dynamic Somatosensory Evoked Potentials;
Electrophysiological Effects on the Spinal Cord with
Cervical Extension
Yuichiro Morishita, MD, PhD, Iizuka, Japan
Takeshi Maeda, Iizuka, Japan
Tsuneaki Takao, MD, Iizuka, Japan
Hiroaki Sakai, MD
Tetsuo Hayashi, MD, Fukuoka, Japan
Masatoshi Naito, MD, Fukuoka, Japan
Keiichiro Shiba, MD, Iizuka, Japan
INTRODUCTION: It is well known that static and dynamic
spinal cord compressed factors may play an important role in
the pathogenesis of cervical spondylotic myelopathy (CSM).
Recently, kinematic MRI studies have been performed to evaluate
dynamic alterations of the spinal canal and cord in patients
with CSM. However, it is difficult to make objective clinical
assessments of CSM based on radiological findings alone.
Many authors have reported somatosensory evoked potentials
(SSEPs) to be useful for neurophysiological study detecting
objective functional abnormalities of the spinal cord. When the
clinical presentations of CSM are equivocal, neurophysiological
investigations such as SSEPs may be useful to evaluate clinical
assessment. However, to the best of our knowledge, few
consecutive studies have reported the dynamic effects on the
spinal cord function using SSEPs. The purpose of this prospective
study was to evaluate the efficacy of analyzing the dynamic
SSEPs in order to predict the dynamic effects on the spinal cord.
METHODS: A total of 40 subjects, including 20 CSM patients
and 20 healthy volunteers, were prospectively examined using
dynamic SSEP. Twenty CSM patients demonstrated cervical
myelopathy due to cervical cord compression at the level of
C4-5 segment evaluated with MRI. Twenty healthy volunteers
presented none of the neurological deficit consciously. Both
Institutional Review Board approval and informed consent
was obtained from all patients. Median nerve SSEPs were
performed with three different postures, including cervical spine
neutral (neut), 10 minutes after 20° extensive (ext-10), and 20
minutes after 20° extensive (ext-20) postures. To confirm the
reproducibility of the SSEPs, each measurement was carried out
at least three times. N20 latencies and amplitudes were evaluated
between each posture for CSM patients and healthy volunteers.
RESULTS: In CSM subjects, N20 latencies were 20.94 ± 1.2
ms (neut), 20.99 ± 0.99 ms (ext-10), and 21.15 ± 1.26 ms (ext20), respectively. The latencies tended to be deteriorated with
cervical spine extension, however, no significant differences
were observed. With respect to N20 amplitudes, they were 1.71 ±
0.63 µV (neut), 1.43 ± 0.5 µV (ext-10), and 1.41 ± 0.63 µV (ext20), respectively. The amplitudes were significantly deteriorated
with cervical spine extension (p<0.05, p<0.05, respectively). In
healthy volunteers, N20 latencies were 19.11 ± 1.2 ms (neut), 19.27
± 1.23 ms (ext-10), and 19.27 ± 1.18 ms (ext-20), respectively.
The latencies tended to be deteriorated with cervical spine
extension, however, no significant differences were observed.
With respect to N20 amplitudes, they were 3.5 ± 1.17 µV (neut),
3.32 ± 1.18 µV (ext-10), and 3.32 ± 1.19 µV (ext-20), respectively.
The amplitudes tended to be deteriorated with cervical spine
extension, however, no significant differences were observed.
DISCUSSION AND CONCLUSION: Median nerve SSEPs
deteriorated with cervical spine extension in both CSM patients
and healthy volunteers. These results suggested that cervical spine
extension might lead to electrophysiological dysfunction of the
spinal cord without clinical neurological manifestation. Moreover,
N20 amplitudes were significantly deteriorated with cervical
spine extension in CSM patients. The dynamic SSEP is a useful
neurophysiological diagnostic technique to detect the effects of
dynamic factors on pathogenesis of CSM.
PAPER NO. 452
Preoperative Autologous Blood Donation Results in
More Transfusions in Idiopathic Scoliosis Surgery
Lukas P. Zebala, MD, Saint Louis, MO
Lawrence G. Lenke, MD, Saint Louis, MO
Brenda Sides, MA, Saint Louis, MO
PAPER NO. 453
INTRODUCTION: Preoperative autologous blood donation
(PABD) overuse in adolescent idiopathic scoliosis (AIS) surgery
increases morbidity and healthcare cost. Our purpose was to evaluate
the outcomes of PABD in adolescent idiopathic scoliosis surgery.
METHODS: We prospectively enrolled 86 single-center AIS
fusion patients from 2006-2010. Patients were divided into
PABD (n=32) or no donation (NPABD, n=54)) as chosen by
parents. Variables analyzed included demographic, radiographic,
surgical and postop data, # PABD units, preop/postop hematocrit
(Hct), and # intraop/postop transfusion units. Wasted PABD
was calculated (PABD units - autologous units transfused).
Continuous (t-test/Wilcoxon rank test) and categorical (Fischer’s
exact/chi-square) data were analyzed. Univariate/multivariate
logistic regressions were run. Twenty-eight PABD/NPABD
pairs were matched on preop Hct (within one unit) to assess
(McNemar’s test) if PABD patients are transfused at a higher Hct.
RESULTS: Baseline data was similar between groups (Table
1). More PABD than NPABD patients received intraop (56% vs.
33%, p=0.04), postop (56% vs. 15%, p<0.0001) and total (81%
vs. 41%, p=0.0003) transfusions. Transfusion was not related to
age, gender, ethnicity or height. Weight influenced transfusion
as 40% of patients <56kg and only 20% > 56kg were transfused
(p=0.04). Increased # PABD decreased preop Hct (r=-0.27,
p=0.01). Univariate logistic regression revealed transfusion was
related to preop Hct (OR=0.78, p=0.01), drain output (OR=1.1,
p=0.02), # fusion levels (OR=1.4, p=0.01) and PABD (OR=7.4,
p=0.0001). Multivariate logistic regression showed PABD (OR=7.7,
p=0.001), lower preop Hct (OR=0.75, p=0.03) and # fusion
levels (OR=1.6, p=0.003) increased transfusion. Independent
predictors of transfusion were EBL (r=0.67, p<0.0001) and
PABD (r=0.47, p<0.0001). In the matched analysis, PABD
patients were more likely to have transfusion at a given preop
(p=0.008) or postop Hct (p=0.005). The # PABD units had
a strong relationship with wasted PABD (r=0.76, p<0.0001).
DISCUSSION AND CONCLUSION: PABD lowers baseline Hct
and PABD patients are 7.7 times more likely to be transfused.
Transfusion triggers differed between groups; PABD patients were
more likely to get blood at a given Hct. More PABD was wasted
with increased # PABD units. A total of 81% of PABD patients
received a perioperative transfusion compared to 41% of NPABD
patients. Thinner patients were more likely to receive a transfusion.
PABD significantly reduced preoperative hematocrit and a lower
preoperative hematocrit and PABD correlated with increased
transfusions. At a given hematocrit, PABD patients had a greater
chance of receiving a transfusion than NPABD patients. Wasted
units of donated blood correlated with increased number of PABD
units.
966
Evaluation of the Thoracolumbar Injury Classification
System in 458 Consecutively Treated Patients
Andrei Joaquim, SR, MD, Campinas, Brazil
Michael D. Daubs, MD, Salt Lake City, UT
Brandon Lawrence, MD, Salt Lake Cty, UT
Darrel S. Brodke, MD, Salt Lake City, UT
Alpesh A. Patel, MD, Maywood, IL
INTRODUCTION: The Thoracolumbar Injury Classification
System (TLICS) system has been developed to improve injury
classification and guide surgical decision-making, yet validation
of this new system remains sparse. The objective of this study is to
evaluate the use of the TLICS in a large, consecutive series of patients.
METHODS: We performed a retrospective analysis of 458
consecutive patients treated for thoracic or lumbar spine trauma
from 2000 to 2010 at a single, tertiary medical center. Clinical
and radiological data were evaluated, classifying the injuries by
ASIA status, the Magerl/AO classification, and the TLICS system.
RESULTS: A total of 310 patients (67.6%) were treated
conservatively (Group 1) and 148 patients (32.3%) were surgically
(Group 2) treated. All patients in Group 1 were ASIA E, except one
(ASIA C). In this group, 304 patients (98%) had an AO type A
fracture. The TLICS score ranged from 1 to 7 (mean 1.53, median
1). Some 307/310 (99%) patients matched TLICS treatment
recommendation (TLICS ≤ 4), except three with distractive
injuries (TLICS 7) initially misdiagnosed. Nine patients (2.9%)
were converted to surgical management. In Group 2, 105 (70.9%)
were ASIA E while 43 (29%) had neurological deficits (ASIA A-D).
A total of 103 patients (69.5%) were classified as AO type A, 36
(24.3%) as type B, and nine (6%) as type C. The TLICS score
ranged from 2 to 10 (mean 4.29, median of 2). Sixty-nine patients
(46.6%) matched the TLICS recommendation; all discordant
patients (53.4%) were treated for stable burst fractures (TLICS=2).
No neurological complications occurred in either group.
DISCUSSION AND CONCLUSION: The TLICS recommendation
matched treatment in 301/310 patients (97.1%) in the
conservative group. However, in the surgical group, 53.4%
of patients did not match TLICS recommendations; all were
burst fractures without neurological injury (TLICS=2). The
TLICS system can be used to effectively classify thoracolumbar
injuries and guide conservative treatment. Inconsistencies,
however, remain in the treatment thoracolumbar burst fractures.
PAPER NO. 454
Influence of the Artery of Adamkiewicz Interruption on
Neurologic Function
was C in one, D in five, and E in 12. At follow up, the Frankel
grade was D in one, and E in 17. There was no case of neurologic
deterioration or paralysis at all, although ligation of the artery
of Adamkiewicz was performed during TES surgery in our series
of 18 cases. One case with a Frankel grade of C improved to E.
Of five cases with D before surgery, four cases became E and one
case became D at follow up. Transiently paralyzed patients in
early postoperative period of TES were not found in this series.
The number of excised vertebrae by TES was one in 10 cases,
two in three cases, and three in five cases. Even in the eight cases
with interruption of two or three pairs of segmental arteries
vertebrae, there was no neurologic deterioration after the surgery.
DISCUSSION AND CONCLUSION: On the basis of our results
of TES on up to three vertebrae, interruption of the artery of
Adamkiewicz for TES does not adversely affect neurologic
function. We advocate strongly that our surgeons are allowed to
sacrifice up to three pairs of segmental arteries, even including the
artery of Adamkiewicz, if necessary. Description of the artery of
Adamkiewicz in textbooks should be rewritten.
INTRODUCTION: The most important feeding artery of the
thoracolumbar spinal cord is the great anterior radiculomedullary
artery, also called the artery of Adamkiewicz. The artery of
Adamkiewicz supplies the lower two thirds of the spinal cord via the
anterior spinal artery. In textbooks of the spine, the potential risk
of neurologic deficits after sacrificing the artery of Adamkiewicz is
described repeatedly. It is naturally believed among spine surgeons
that interruption of the artery of Adamkiewicz during surgeries
is absolutely contraindicated. However, this is a recommendation
based on past experiences and there is no evidence. On the
other hand, total en bloc spondylectomy (TES) for spine tumors
requires interruption of bilateral segmental arteries corresponding
to the levels of tumor-containing vertebrae. It is necessary to
sacrifice the artery of Adamkiewicz during the surgery of TES,
when the tumor, by chance, exists at the level of the artery of
Adamkiewicz. Thus there is a possibility that the TES procedure
for thoracolumbar vertebral tumors can cause postoperative
paraplegia as a result of spinal cord ischemia brought about by
interruption of the bilateral segmental arteries including the artery
of Adamkiewicz. The purpose of this study is to assess neurologic
function after interruption of the artery of Adamkiewicz in TES.
METHODS: We have performed 211 cases of TES between 1990
and 2010. All cases except for few emergency cases received
preoperative embolization before TES. The artery of Adamkiewicz
was verified by angiography of the segmental arteries for the
preoperative embolization. In this study, we defined the artery
of Adamkiewicz as a spinal branch (radiculomedullary artery)
of the segmental artery which supplied the anterior spinal artery
extending to lumbar enlargement. There were 18 patients in which
the artery of Adamkiewicz was found at the levels of resected
vertebrae. TES on up to three vertebrae was performed in the 18
cases and up to three pairs of segmental arteries including the
artery of Adamkiewicz were interrupted. Neurologic function
was analyzed retrospectively according to Frankel grading system.
RESULTS: Of the 18 patients the Frankel grade before surgery
967
PAPER NO. 455
uProphylactic Intrathecal Steroids has a Protective
Effect in a Spinal Cord Injury Model
Martin Quirno, MD, New York, NY
Kirk A. Campbell, MD, New York, NY
Andrew Yoo, BA, New York, NY
Ying Zhang, MD, New York, NY
Thorsten Kirsch, PhD, New York, NY
INTRODUCTION: Many strategies have been developed to
avoid spinal cord injury in high-risk spinal deformity surgery.
Current monitoring strategies, through intraoperative conduction
studies, can only report an injury when it happens and some
injuries fail to be captured. This catastrophic complication is
usually irreversible. The purpose of this study was to determine
if prophylactic intrathecal steroid injection had a protective
effect on rats with mechanically induced spinal cord injury.
METHODS: We utilized a standardized rat spinal cord injury model
by introducing a small arterial fogarty catheter through a T10
laminotomy and compressing the cord through inflation. The goal
was to induce an incomplete spinal injury. Three different study
groups were established: group 1 was treated with prophylactic
intrathecal methylprednisone injection of prior to SCI; group 2 was
treated with intrathecal normal saline (NS) prior to SCI; and group
3 was only treated with intrathecal methylprednisone injection
and no SCI. Rats were followed twice weekly by a pair of blinded
evaluators for a period of eight weeks utilizing the Basso-BeattieBresnahan (BBB) standardized spinal cord clinical classification.
RESULTS: Post-operatively all rats that underwent SCI had a
36 hour spinal shock phase where they were all unable to move
both hind legs. Group 3 rats (without SCI) recovered from
surgery without any signs of cord pathology. Following the
initial 36 hours, group 1 (Steroids and SCI) had a significant
improvement in their BBB score and had full recovery to preoperative levels after only five weeks. This deferred from the
group 2 controls (NS and SCI) in which they only recovered to
approximately half their pre-operative status after eight weeks.
DISCUSSION AND CONCLUSION: Prophylactic intrathecal
treatment of rats prior to spinal cord injury has a protective
effect against myelin damage and leads to faster clinical
recovery. Similarly, the prophylactic treatment of patients in
high-risk spinal deformity surgery with high concentrations of
intrathecal steroid has the potential to fully restore pre-operative
physiological cord functions in the case of spinal cord injury.
This significant change in surgical protocol can have a large
impact on the life of the few who develop this complication.
PAPER NO. 456
Comparative Analysis of Clinical Outcomes in Patients
with OVCF: Conservative Treatment vs. Balloon
Kyphoplasty
Si Young Park, MD, PhD, Seoul, Republic of Korea
Seung B. Han, MD, Seoul, Republic of Korea
Woong Kyo Jeong, Seoul, Republic of Korea
Dae-Hee Lee, MD, Seoul, Republic of Korea
INTRODUCTION: Most osteoporotic vertebral compression
fractures (OVCF) can be treated conservatively. Recently,
kyphoplasty has become a common treatment for painful OVCF and
has shown numerous benefits. In spite of being a simple procedure,
numerous complications related to kyphoplasty have been reported.
Moreover, there is limited evidence to support its superiority.
METHODS: We prospectively enrolled 259 patients who had
acute painful OVCF confirmed by MRI. All patients were treated
conservatively (CV) in the initial three weeks. Kyphoplasty (KP)
was performed in 98 patients who complained of sustained back
pain and disability in spite of conservative treatment for the initial
three weeks. Participants were stratified according to demographic
data and radiographic data. VAS and ODI score were assessed at one
week and at one, three, six and 12 months RESULTS: A total of 238
patients (89 of 98 in the KP and 149 of 161 in CV) completed the oneyear follow up. Risk factors for failure of three weeks of conservative
treatment were older age, severe osteoporosis, overweight and
larger collapse rates. At one month, better clinical results were
observed in KP. However, there were not significant differences
in outcome measures between the two groups after first month.
DISCUSSION AND CONCLUSION: In summary, both treatments
of OVCF showed successful clinical results at the end of the one968
year follow-up period. Kyphoplasty showed better outcomes in the
first month only. Given these results, in the case of a patient with
OVCF that has no risk factors for failure of conservative treatment,
kyphoplasty might not be indicated. Rather, a trial of conservative
treatment for three weeks can be beneficial.
PAPER NO. 457
Incidence of Undiagnosed Cervical Myelopathy in
Patients with Odontoid Fractures
Julie L. Shaner, BA, Philadelphia, PA
INTRODUCTION: The most common mechanism leading to
odontoid fracture is a fall from standing height and this injury
is found predominantly in elderly patients. Despite extensive
study on outcomes and treatment method for odontoid
fractures, no studies have identified risk factors for falls in
this population which may predispose patients to odontoid
fractures. The purpose of this study was to identify patients
presenting with odontoid fracture who had undiagnosed
subaxial cervical stenosis with spinal cord compression, defined
factors which predispose patients to gait instability and falls.
METHODS: This retrospective, cohort study included consecutive
patients who presented to a single institution from 2006-2010
with an acute, displaced odontoid fracture. Patients were excluded
who had a history of known risk factors for gait instability or
falls including dementia, stroke, seizure disorder, Parkinson’s
disease or severe vision disorders. Additionally, patients with
subacute odontoid fractures were excluded. Charts were reviewed
for demographic information, co-morbidities and mechanism of
injury (fall from low energy fall vs. MVA vs. other). All CT and,
when available, MRI images were evaluated for subaxial stenosis
and spinal cord compression by a musculoskeletal radiologist
excluding findings at the level of the odontoid fracture or other
associated acute fractures. Cervical myelopathy was defined
as the presence of abnormal clinical examination findings
associated with corticospinal tract dysfunction including:
Babinski’s sign on plantar stroke, positive Hoffman’s reflex, the
presence of clonus and hyperreflexia in more than one extremity.
RESULTS: After excluding patients for subacute fracture and
confounding comorbidities, 110 patients were eligible, including
78 after acute falls from standing (FFS), 14 after MVA and 18 after
other mechanism of injury. Of the 78 patients presenting after
FFS, 14 patients (18%) had evidence of moderate to severe stenosis
at subaxial levels on CT scan. An additional seven patients (9%)
had evidence of moderate to severe stenosis on MRI for a total of
21 total patients with radiographic evidence of stenosis (27%).
Of the patients with stenosis, five patients (6%) had compressive
pathology which abutted the spinal cord and 13 patients (17%)
had evidence of spinal cord compression at subaxial levels.
Seventeen patients (22%) had abnormal clinical examination
findings in the setting of radiographic evidence of subaxial stenosis
consistent with the presence of myelopathy including 13 patients
(17%) with subaxial spinal cord abutment or compression.
DISCUSSION AND CONCLUSION: We found that 22% of patients
presenting with acute odontoid fracture after a fall from standing
have concomitant radiographic evidence of stenosis and abnormal
examination findings consistent with myelopathy. We hypothesize
that undiagnosed cervical myelopathy may be an important
etiology for falls in patients who present with odontoid fractures.
Identification and treatment of myelopathy may be important to
prevention of primary falls and reduction of subsequent fractures
after odontoid fracture.
PAPER NO. 458
Incidence of Undiagnosed Neurological Disorders in
Hip Fracture Patients
Roman Trimba, BS, Brooklyn, NY
Jeffrey B. Walker, BS, Media, PA
Javad Parvizi, MD, Philadelphia, PA
INTRODUCTION: Hip fractures are a common cause of
morbidity and mortality in elderly patients. Cervical myelopathy
is a common condition in elderly patients that can result
in significant ataxia. The hypothesis of this study was that
undiagnosed neurological dysfunction, most likely cervical
spondylotic myelopathy, would be a risk factor for falls resulting
in hip fracture in elderly patients. The purpose of this study was
to identify the incidence of undiagnosed cervical myelopathy
in patients who fall and develop hip fractures compared to agematched control patients who underwent total hip arthroplasty.
METHODS: Prospective, case control study of consecutive patients
who presented with displaced fractures involving the proximal
femur (femoral neck, intertroch, subtroch) or pelvis (pubic ramus)
after fall from standing. Exclusion criteria included cognitive
impairment, known diagnosis of cervical myelopathy, previous
cervical spine surgery, inability to comply with examination or
refusal to participate. The control group of this study was agematched elderly patients who underwent total hip arthroplasty.
Myelopathy was considered the most likely neurological disorder
based on clinical history elements (Japanese Orthopaedic
Association Score <15) and pathological reflexes. Comparison of
the incidence of myelopathy in the study population compared
to the control population was performed using Fisher’s exact test.
RESULTS: There were a total of 117 patients (68 hip fractures and
49 hip arthroplasties) who were eligible for enrollment in the study.
Fifty-five patients were excluded including 14 elective patients
and 41 hip fractures. The final study population included 28 hip
fractures and 35 elective patients. There were 5/28 patients with
cervical myelopathy among the fracture patients (18%) compared
to 0/35 (0%) patients in the total hip arthroplasty group (p=0.01).
DISCUSSION AND CONCLUSION: Hip fracture is a complex,
multifactorial process and the majority of patients (60%) were
not cognitively intact. However, 18% of the cognitively intact hip
fracture patients manifested symptoms and signs consistent with
a neurological disorder likely cervical spondylotic myelopathy.
Undiagnosed neurological disorders may predispose patients to
falls and development of fragility fractures. Screening for cervical
myelopathy should be part of the workup of all hip fracture
patients and may reduce the risk of subsequent fractures.
969
PAPER NO. 459
Cervical Spine Clearance Protocols in Level I, II and III
Trauma Centers in the State of CA
Robert G. Dionisio, BS, San Francisco, CA
Robert T. McClellan, MD, San Francisco, CA
INTRODUCTION: Cervical spine clearance protocols have been
developed to standardize the clearance of C-spine following high
energy blunt trauma and prevent neurological deficits secondary
to missed unstable spine injuries. The guidelines on cervical
spine clearance are evolving as new imaging techniques become
more available. Ideally each trauma center should develop and
update their cervical spine clearance protocols, however this is not
mandatory. The purpose of this study is to evaluate the cervical
spine clearance practice in trauma centers in the State of CA.
METHODS: Level I (n=15), II (n=30) and III (n=11) trauma
centers in the State of CA were identified through the Trauma
Managers Association of CA website. The trauma managers
in these centers are contacted via e-mail and phone calls. If the
center has an official cervical spine clearance protocol, these
protocols were evaluated to understand their current practice.
RESULTS: Overall, only 50% of all trauma centers in CA had a
cervical spine clearance protocol. Specifically, 80% of Level I,
47% of Level II and only 18% of Level III trauma centers had an
official cervical spine clearance protocol. Of the centers which
has an official c-spine clearance protocol, 67% of Level I, 57% of
Level II centers use Nexus criteria with/without painless ROM to
clear asymptomatic patients. Again, 67% of Level I, 64% of Level
II centers use multi-detector computed tomography scans as the
first line of imaging in symptomatic patients. Fifty-eight percent
of Level I and 28% of Level II centers prefer MRI in addition to
CT scans, whereas 25% of Level I and 21% of Level II centers
prefer CT scan only to clear cervical spine of obtunded patients.
Only two Level III centers had protocols, however they were
not clear with regard to the algorithm that should be followed.
DISCUSSION AND CONCLUSION: This study showed that only
50% of the trauma centers in CA have an official cervical spine
clearance protocol and only 30% of the centers have protocols
that follow current recommendations. Policies should be made to
improve the quality and use of official cervical spine protocols in
all trauma centers.
PAPER NO. 460
Emergent Surgical Management of Spinal Metastases
and Neurologic Deterioration
Christopher G. Furey, MD, Cleveland, OH
Sanford E. Emery, MD, MBA, Morgantown, WV
Jung U. Yoo, MD, Portland, OR
INTRODUCTION: Patients with spinal metastases with neural
compression and neurologic deterioration pose a great challenge
to the spine surgeon. While other palliative options are available,
including stereotactic radiosurgery, surgery is the best option in
cases of progressive neurologic deterioration. Numerous factors
must be considered when creating a treatment plan, including
the patient’s medical condition, prognosis, tumor location and
type, as well as the patient and family’s desires. The goal of
this study was to evaluate the outcomes of emergent surgery
performed on patients with progressive neurologic deterioration
due spinal metastases. Additionally, multiple clinical and
radiographic factors were analyzed in attempts to identify
prognostic factors for neurologic improvement following surgery.
METHODS: A total of 46 patients with neurologic deterioration
due to spinal metastatic disease underwent emergent surgery
over a six-year period (2004-2009). All 46 patients were unable to
ambulate at the time of presentation. Pre-operatively 29 patients
were ASIA B, 12 were ASIA C and five were ASIA D. Primary
tumor was renal cell in 12 patients, lung in 11, breast in nine,
prostate in eight, gastrointestinal in four, and unknown in two.
Some 33 patients had undergone radiation therapy at some point
prior to surgery. The location of tumor was in the thoracic spine
in 40 patients and the lumbar spine in six. The location of spinal
cord compression was anterior in 26 patients, posterior in seven
cases and circumferential in 13. Surgical management included
anterior decompression and structural grafting in six patients,
posterior decompression and instrumented fusion in 30 patients,
and a circumferential approach in 10 patients. Logistic regression
analysis was used to evaluate multiple clinical and radiographic
factors for their relationship to neurologic improvement.
RESULTS: The mean survival post-operatively was 8.9 months
(range: two weeks - 60 months). A total of 36 patients (78%)
had neurologic improvement of at least one ASIA grade, seven
(15%) did not improve, and three (7%) regressed a single grade.
Some 33 patients (72%) regained ambulation post-operatively.
Factors significantly associated with neurologic improvement
included age < 65 years, less severe neurologic deficit (ASIA C or
D), neurologic deficits present less than one week, neurologic
deterioration occurring less than 48 hours prior to surgery, presurgical hospitalization less than 48 hours, and post-operative
radiation therapy. Factors not significantly associated with
neurologic improvement included tumor location, type of
primary malignancy and surgical approach. Survival rates were
significantly better in those patients who regained ambulation.
Major peri-operative complications occurred in six patients
(13%) and two patients (4%) required additional surgery within
one week. Four patients (9%) died within six weeks of surgery.
Inability to ambulate, lung cancer and an anterior transthoracic
surgical approach were significant risk factors for early mortality.
DISCUSSION AND CONCLUSION: Surgery is effective in arresting
and reversing progressive neurologic deficits in patients with neural
compression due to metastatic spinal disease. Patients with less
severe neurologic deficits and those with neurolgic compromise
of shorter duration prior to surgery had greater likelihood of
neurologic recovery. Regaining the ability was associated with
longer life spans. Complication rates and re-operation rates were not
insignificant and were associated with worse neurologic recovery
and shorter survival. Although palliative, emergent surgical
management of patients with progressive neurologic deficits due
to spinal metastases is effective in improving neurologic function.
PAPER NO. 461
Are Spine Injuries Sustained in Battle Truly Different?
James A. Blair, MD, San Antonio, TX
Jeanne C. Patzkowski, MD, San Antonio, TX
Andrew Schoenfeld, MD, Canutillo, TX
Jessica D. Cross, MD, Fort Sam Houston, TX
Eric S. Grenier, MD, Fort Sam Houston, TX
Ronald A. Lehman, MD, Potomac, MD
Joseph R. Hsu, MD, San Antonio, TX
INTRODUCTION: The severity and prognosis of combatrelated injuries to the spine and spine injuries sustained
unrelated to direct combat has not been previously
compared. Differences may have implications on tactics,
treatment strategies and directions for future research.
METHODS: The Joint Theater Trauma Registry (JTTR) was queried
970
using ICD-9 codes to identify all individuals who sustained battle
and nonbattle injuries to the neck, back, spinal column or spinal
cord in Operation Iraqi Freedom (OIF) or Operation Enduring
Freedom (OEF) from October 2001 to December 2009. Medical
records of all identified service members were individually
reviewed. Demographic information including sex, age, military
rank, date of injury and final disposition were obtained for
all patients. Spinal injuries were categorized according to
anatomic location, associated neurological involvement,
precipitating mechanism of injury (MOI) and concomitant
wounds. These data points were compared for the groups battle
spine injuries (BSI) and non battle spine injuries (NBSI).
RESULTS: A total of 502 service members sustained a total of 1,837
battle injuries to the spinal column, including 1,687 fractures
(92%); compared to 92 service members sustaining 269 nonbattle
spinal column injuries, with 241 (90%) fractures. Ninety-one BSI
service members (18% of patients) sustained spinal cord injuries
(SCI) with 41 (45%) complete spinal cord injuries, compared to
13 (14% of patients) nonbattle SCI with six (46.2%) complete
injuries (p=0.92). The reported MOI for 335 BSI servicemembers
(66.7%) was an explosion compared to one NBSI explosive
injury. Eighty-four patients (17%) sustained gunshot wounds
(GSW) in battle compared to five (5.2%) nonbattle GSWs. Fifteen
patients (3.0%) sustained a battle-related fall compared to 29
(30%) nonbattle-related falls. BSI servicemembers underwent
significantly higher rates of surgical interventions (p<0.0001),
were injured by high energy injury mechanisms at a significantly
greater rate (p<0.0001) and demonstrated a trend toward lower
neurologic recovery rates following spinal cord injury (p=0.16).
DISCUSSION AND CONCLUSION: BSI and NBSI are separate
entities that may ultimately have disparate long-term prognoses.
NBSI patients, while having similar mechanisms of injury compared
to civilian spinal trauma, maintain a different patient demographic.
Further research must be directed at accurately quantifying the longterm disabilities of all spine injuries sustained in a combat theater,
whether they are the result of battle or not.
PAPER NO. 462
Stochastic Simulation of Operative vs. Non-operative
Management of Odontoid Fracture in the Elderly
Suneel B. Bhat, MD, Philadelphia, PA
INTRODUCTION: Fracture of the odontoid composes the majority
of all spine fractures in the geriatric population. While consensus
exists regarding treatment of Type I and Type III odontoid fractures,
management of Type II fractures remains controversial. These
fractures may be treated successfully either operatively or using
conservative bracing, however the relative population benefits of
these approaches remains unclear. This study aimed to characterize
the direct population implications on mortality and major
complication rate of operative vs. non-operative management
of traumatic Type II odontoid fracture in elderly patients.
METHODS: Consecutive cases of C2 fracture from June 1985 to July
2006 were retrospectively reviewed, and isolated Type II odontoid
injuries in patients 70 and older were identified for surgical or
non-surgical management, associated mortality, associated airway
complication or at least one associated major complication. A
unique stochastic decision tree model based on probabilities
derived from our data was developed, and a modified Monte Carlo
simulation was conducted with each management approach using
identical theoretical populations of 1,000,000 geriatric patients
modeled from the 2008 U.S. Census estimates. Individually
simulated patients accrued risk of Type II odontoid fracture,
management associated airway complication or presence of at least
one associated complication, and average length of inpatient stay.
The simulation was iterated 10 times to achieve stable estimates.
RESULTS: The incidence of Type II odontoid fracture for the
U.S. population over the age of 70 was approximated to 3.6
per 100,000, or 1,101 cases annually. In the elderly, operative
management is associated with 96.32 deaths (95% CI 71.87 to
120.78), and non-operative management is associated with 264.20
deaths (95% CI 234.99 to 293.42); operative management result
in a significant average annual reduction in mortality of 167.88
deaths. Non-operative management would on average prevent
55.04 airway complications and 247.69 major complications
annually, and avoid 7,477 inpatient person-days each year.
DISCUSSION AND CONCLUSION: Odontoid fracture in the
elderly can be acceptably managed by both operative and nonoperative approaches. While operative management will likely
prevent approximately 167.88 deaths annually, non-operative
management would avoid approximately 247.69 major treatment
complications, 55.04 airway complications and over 7,400
inpatient days each year, in part secondary to increased mortality.
processing with DR control processing, which expanded the visible
area in certain areas, while maintaining contrast in the area of
interest. The resultant visible areas included C1 to L5 and sacrum
to femoral head. MFP was used to improve the image sharpness
of the bone margins of the whole spine. As a result, our set of new
CR processing parameters can improve the clarity of whole spine
X-rays compared with conventional X-ray images. The greatest
advantage of image processing was that it enabled clear depiction
of the thoracolumbar junction, lumbar vertebrae, sacrum and
femoral head in the lateral view. The image processing technology
we used in this study involved the same level of radiation exposure
as that for conventional CR imaging. Furthermore, this image
processing is available on existing x-ray equipment. If we set the
image processing parameters in advance, a single mouse click
can enable viewing of the processed image. The improvements in
image clarity that we observed in this study suggest that CR image
processing of whole spine x-rays has the potential to facilitate
detailed evaluations involving various measurements and
alignment of the whole spine.
PAPER NO. 463
New Computed Radiography Processing Condition for
Whole Spine X-ray
Takeshi Sasagawa, MD, Tokyo, Japan
Junichi Kunogi, MD, Tokyo, Japan
Shigeru Masuyama, Shibuyaku, Tokyo, Japan
Satoshi Ogihara, Tokyo, Japan
INTRODUCTION: Computed radiography (CR), which is
now enjoying widespread use, has many advantages compared
with conventional x-rays, especially in image processing.
Although CR image processing technology is being used in
chest radiography and mammography, it thus far has not
found application to spine imaging. The purpose of this study
was to formulate a set of new CR processing parameters and to
test whether the resultant whole spine x-ray images visualize
the spine more clearly than conventional x-ray images.
METHODS: The study comprised 29 patients who underwent
whole spine x-rays. We used three image processing methods to
improve the clarity of whole spine x-rays: gradation processing,
dynamic range (DR) control processing and multi-objective
frequency processing (MFP). X-ray image definition was evaluated
using vertebrae sampled from each region of the whole spine,
specifically C4, C7, T8, T12, and L3; evaluation of the lateral
view included additionally the sacral spine and femoral head.
Image definition was assessed using a three-point grading system.
The conventional and processed CR images (both frontal and
lateral views) of all 29 study patients were evaluated by five spine
surgeons. The evaluating surgeons were blinded as to the category
of images they were evaluating: conventional or processed.
RESULTS: In all spinal regions on both frontal and lateral views,
the processed images showed statistically significantly better
clarity than the corresponding conventional images, especially
at T12, L3, sacral spine and femoral head on lateral view.
DISCUSSION AND CONCLUSION: We combined gradation
971
PAPER NO. 464
Clearing the C-spine in Obtunded Trauma Patients
Based on Admission CT: A Prospective Randomized
Controlled Trial
Christopher P. O’Boynick, MD, Saint Louis, MO
Tim M. Lonergan, BS, Saint Louis, MO
Howard M. Place, MD, Saint Louis, MO
INTRODUCTION: Cervical spine clearance of the obtunded
patient with normal radiographic appearance on CT scan has
been a matter of much debate in the trauma and spine surgery
literature. There are various algorithms across the nation for
excluding cervical spine injury in the obtunded patient, but no
true standardization exists. This lack of standardization results in
disjointed management of c-collar precautions often resulting in
prolonged and unnecessary immobilization. Immobilization is
not without consequence and has been associated with respiratory
deterioration, skin breakdown, venous thrombosis and delay of
head and neck surgical procedures. Each day spent in cervical
immobilization increases the risk of decubitus ulcer by 66%. The
purpose of this study was to prospectively analyze two c-spine
clearance protocols at a level 1 trauma center: Early radiographic
clearance at 48-72 hours using admission cervical CT vs. c-collar
immobilization until clinical exam. Our hypothesis is that the
c-spine in obtunded trauma patients can be safely cleared with
cervical CT without patient participation in a clinical exam.
METHODS: Ninety-six obtunded blunt trauma patients were
admitted to our Level 1 trauma center. Ages ranged from 18-81
years. All patients had cervical spine CT scans upon admission
negative for injury. Exclusions included cervical spine fracture,
abnormal spinal cord examination and return to normal mentation
within 48 hours. For the purposes of this study one spine surgeon
cleared the c-spine in obtunded trauma patients using cervical CT
alone at 48-72 hours following admission. The remaining spine
surgeons awaited patient participation in a clinical exam prior to
clearance. Participants were randomized to each arm based on
the spine surgeon on call at admission. Radiographic stability was
determined by the White & Panjabi stability scale and the cervical
spine injury severity score which was applied to each admission CT
scan. All patients cleared using CT alone underwent clinical exam
once awake and cooperative to rule out a missed injury. Flexion/
extension x-rays were obtained on any patient radiographically
cleared that reported pain on follow-up examination.
RESULTS: Forty-one patients underwent c-spine clearance
radiographically at a mean of four days with a range of two-14 days.
Fifty-five patients reMEd immobilized until clinical exam was
performed at an average of 15 days after admission. Immobilization
ranged from two-44 days. Patients cleared radiographically
decreased unnecessary immobilization by 11 days (p<0.001).
There was no difference in age (p=0.7), admission GCS (p=0.9)
or length of hospital stay (p=0.8). Documented pain-free c-spine
exam was available for all patients cleared radiographically upon
return to normal mentation. No patients had missed injury. Three
patients died of injuries unrelated to their c-spine with one in the
early clearance group and two in the clinical exam group. Eleven
patients were discharged in c-collar. One patient in the clinical
exam group was cleared via MRI after 21 days of immobilization.
DISCUSSION AND CONCLUSION: The overall goal of this
study was to analyze radiographic clearance of the c-spine using
CT scan for rates of missed injury and overall safety compared
to the standard protocol of immobilization. Additionally, we
hoped to safely reduce time spent in unnecessary c-collar as this
is not a benign entity. Removal of c-spine precautions based on a
negative CT scan at admission is a viable option in trauma patients
anticipated to remain obtunded for a significant amount of time.
We were able to safely decrease the duration of unnecessary CS
immobilization by 11 days. There were zero missed injuries that
resulted in clinical instability.
PAPER NO. 465
uDoes Provocative Discography Cause Clinically
Important Injury to the Lumbar Intervertebral Disc?
Jason M. Cuellar, MD PhD, New York, NY
Eric Hurwitz, DC, PhD, Honolulu, Hawaii
john A. carrino, MD, Baltimore, MD
Richard J. Herzog, MD, New York, NY
INTRODUCTION: Provocative discography, an invasive diagnostic
procedure involving disc puncture and injection, is purported to
detect discogenic sources of back pain in discs with otherwise
unremarkable imaging findings. The clinical validity and utility
of this test is unproven. Disc puncture in animal studies can
cause rapid disc degeneration. Discography in human subjects
has shown accelerated disc degeneration by MRI. Whether this
972
effect is associated with adverse clinical effects is not known.
METHODS: Seventy-five subjects underwent provocative, pressure
controlled discography, 75 control subjects did not. Subjects
matched at baseline for similar baseline MRI findings and other
clinical and demographic features. Subjects underwent one, two,
five and 10 year surveillance for adverse low back pain (LBP) events,
imagine studies, medical visits for LBP and surgery by blinded and
independent observers following a scripted interview protocol.
Charges for surgery and imaging procedures were calculated
using 2007 discounted rates at the primary university hospital.
RESULTS: Of enrolled 150 subjects, 71 discography subjects
completed the baseline evaluation, as did 72 of the control
subjects. At 10-years follow up, 57 discography and 53 control
subjects completed all interval surveillance evaluations. There
were 16 lumbar surgeries in the discography group, compared with
four in the control group (p = 0.02; Kaplan-Meier Log-Rank Test).
CT and MRI examinations were more frequent in the discography
group compared to control subjects (p = 0.04; Kaplan-Meier LogRank Test). The discography group had more adverse events,
increasing over time, for serious LBP episodes (year 1, p = 0.01;
year 10, p = 0.02 ; Fisher’s Exact Test), work loss (year 10, p =
0.01) and medical care visits (year 10, p = 0.002) compared to the
discography group. Increased cost for surgery and imaging alone
in the discography group were >$450,000 USD or $9,000/subject.
DISCUSSION AND CONCLUSION: Disc puncture and injection,
even with small gauge needle and low pressure techniques, can
cause significant clinical injury and increased clinical problems in
exposed subjects. The morbidity and costs of these downstream
events is high. The clinical benefit of discography or other disc
puncture interventions would need to be proven to be as high and
greater to off-set the demonstrable adverse effects of this procedure.
PAPER NO. 571
Drivers of Quality and Outcomes in Spine Implant
Surgery: Perceptions Among Medical Device
Representatives
Amy Wasterlain, Menlo Park, CA
S. R. Golish, MD, PHD, Ridgefield, WA
Mike Reed, PT, Palm Beach Gardens, FL
Hillary Braun, Redwood City, CA
Gaetano J. Scuderi, MD, Redwood City, CA
INTRODUCTION: Patient safety is one of the highest priorities
in healthcare. Although existing research has focused on drivers
of quality and surgical outcomes, little has been published on
perceptions of quality. Evidence that surgeons perceive teamwork
within their own teams more highly than others suggests that
physicians may not be the best equipped to evaluate their
own performance. We believe medical device representatives
provide a unique lens into the operating room (OR) because
they have a medical foundation in spine procedures and are
exposed to a variety of cases, institutions, and surgical teams.
METHODS: A total of 108 spine implant medical device
representatives with at least one year of OR experience were given a
21 question survey during the week of the 2011 AAOS in San Diego,
CA to understand how their perceptions of spine surgical outcomes
differ based on institution type, case complexity, staff quality, and
surgical team composition. Four distinct practice settings were
identified: university, small and large private hospitals (defined
as six spine implant cases/week), and ambulatory surgery center
(ASC). Overall perceptions were assessed by asking respondents
how likely they would be to recommend surgery to friends/
family for cases of varying complexity and practice settings.
RESULTS: Respondents included 96 males (89%) and 12 females
(11%) with a mean (±SD) of 6.3 (±3.3) years OR experience.
Respondents rated their impressions of surgeons as excellent
(26.5%), good (53.9%), average (16.1%), fair (3.2%), or poor
(0.3%). The proportion of surgeons rated as excellent or good
was significantly lower in ASCs than in other settings (p<0.01).
Significantly fewer circulating nurses were rated as excellent or
good in universities versus small and large hospitals (p<0.001).
In small hospitals, it was significantly more likely that 75% or
more of the primary team members had worked together before
versus universities (p0.05). There were significantly more cases
in which >3 people were scrubbed at universities versus all other
settings (p0.05). Respondents were more likely to recommend a
university or large private hospital for complex instrumentation
cases (p<0.001), whereas they recommended large private
hospitals over universities for simple instrumentation (p<0.01).
For cases without instrumentation, respondents were more likely
to recommend a large private hospital over a university (p=0.003).
DISCUSSION AND CONCLUSION: Overall, medical device
representatives were most likely to recommend large private
hospitals for simpler spine cases, and large private or university
hospitals for complex cases. Large private and university
hospitals were associated with higher surgeon ratings, less
consistency in the primary OR team, and similar complication
rates relative to other practice settings. However, nurses received
lower ratings, and more cases had at least three people scrubbed
in university hospitals relative to large private hospitals.
Together, these data suggest that the quality of all members
of the surgical team, including nurses and other assistants,
plays an integral role in how surgical teams are perceived.
PAPER NO. 572
Positive Cervical Sagittal Alignment Negatively Impacts
Outcomes Following Adult Cervical Fusion Procedures
Jessica A. Tang, BS, San Francisco, CA
Justin Scheer, San Francisco, CA
Vedat Deviren, MD, San Francisco, CA
Robert S. Bess, MD, Castle Rock, CO
Robert A. Hart, MD, Portland, OR
Christopher Ames, MD, San Francisco, CA
margin, has repeatedly shown to correlate with pain and
disability in thoracolumbar fusion. Multi-level cervical fusion is
commonly performed, yet the impact of cervical sagittal balance
on outcomes has not been reported. This study evaluated the
relationship between cervical sagittal alignment and postoperative
outcomes for patients receiving multi-level cervical fusion.
METHODS: From 2006-2010, 113 patients (M/F=61/52;
59±12y.o.) received multi-level cervical fusion for cervical
stenosis, myelopathy, and kyphosis. Average postop follow-up
was 187 days. An intermediate follow up was selected to facilitate
evaluation of patients recovered from surgery but prior to risk of
pseudoarthrosis that may impact outcome scores. Radiographic
measurements included: (1) C1-2 lordosis, (2) C2-7 lordosis, (3)
C2-7 sagittal vertical axis (C2-7 SVA; distance between C2 plumb
line and C7), and (4) Center of gravity of head SVA (CGH-C7
SVA; distance between external auditory canal plumb line and
C7). Health related quality of life measures (HRQOL) included
neck disability index (NDI), visual analog pain scale (VAS),
and SF-36 physical component (PCS) scores. Pearson productmoment correlation coefficients were calculated between pairs of
radiographic measures and HRQOL scores (significance = p<0.05).
Improvement in NDI scores following surgery were evaluated by
categorizing scores into standard intervals: no disability (0-4),
mild (5-14), moderate (15-24), severe (35-34), and complete (>34).
RESULTS: A total of 80% of patients experienced an improvement
of NDI scores or reMEd the same compared to preop. Some 20%
experienced deterioration. PCS scores improved by 22.0% ±
37.5%. Both C2-7 SVA and CGH-C7 SVA negatively correlated with
PCS (r=-0.43, p<0.001 and r=-0.36, p=0.005, respectively). C2C7 SVA positively correlated with NDI scores (r=0.20, p=0.036).
C2-7 SVA ranged from -5.5-95mm (36.2±15.9mm). CGH-C7
SVA ranged from -17.9-127.1mm (43.6±23.7mm). On average,
C1-2 lordosis constituted 76.0%±15.8% of total cervical lordosis
(defined as the sum of C1-2 and C2-7 lordosis). Comparisons
between radiographic parameters revealed significant correlations
between C2-7 SVA and C1-2 lordosis angles (r=0.33, p=0.0003).
DISCUSSION AND CONCLUSION: Positive cervical sagittal
malalignment, measured by C2-7 SVA, negatively affects HRQOL
scores after multi-level cervical fusion (Fig 1) at intermediate
follow up. Correlations between measures of cervical SVA and C1-2
lordosis suggest that these parameters are linked as patients attempt
to optimize craniocervical alignment. C1-2 alignment may be the
terminal link between the cranium and the cervical spine to regulate
the angle of gaze. This relationship is analogous to the manner by
which the pelvis changes alignment to maintain upright posture.
Also, the high positive correlation between C2-7 SVA and CGH-C7
SVA indicates that the C2 segment plays a critical role in determining
the location of the head center of gravity. This is the first study to
examine the impact that cervical SVA has upon HRQOL following
multi-level cervical fusion. Our findings demonstrate that, similar
to the thoracolumbar spine, the severity of disability increases with
positive sagittal malalignment following surgical reconstruction.
INTRODUCTION: Positive sagittal balance, defined as C7
plumb line >50mm anterior to the posterior superior sacral
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PAPER NO. 573
Cost-Effectiveness Analysis of Surgery for Adjacent
Segment Disease after Anterior Cervical Discectomy
and Fusion
PAPER NO. 574
Kevin R. O’Neill, MD, Nashville, TN
Robert J. Wilson, Nashville, TN
Katharine M. Burns, Nashville, TN
Lauren Mioton, BS, Nashville, TN
Brian T. Wright, BA, Nashville, TN
Owoicho Adogwa, BS, MPH, Nashville, TN
Matthew McGirt, MD, Nashville, TN
Clinton J. Devin, MD, Nashville, TN
Martin Hoffmann, MD, Grand Rapids, MI
Clifford B. Jones, MD, FACS, Grand Rapids, MI
Debra Sietsema, PhD, Grand Rapids, MI
INTRODUCTION: The incidence of symptomatic adjacent
segment disease (ASD) after anterior cervical discectomy and
fusion (ACDF) has been reported to occur in up to 25% of patients.
Quality of life assessments following surgical intervention for ASD
are lacking. Further, with rising healthcare costs and impending
systemic changes, increased understanding of quality of life
outcomes in relation to their economic impact is needed. The
goal of this study was to evaluate the quality of life and costeffectiveness of revision surgery for cervical ASD following ACDF.
METHODS: A retrospective review of 51 patients undergoing
surgery for treatment of ASD following ACDF was performed.
Two-year total neck-related medical resource utilization and
amount of missed work were determined. Quality adjusted life
years (QALYs) were calculated from EQ-5D assessments with U.S.
valuation. Two-year resource use was multiplied by unit costs
based on Medicare national allowable payment amounts (direct
cost) and patient work-day losses were multiplied by the selfreported gross-of-tax wage rate (indirect cost). Mean total twoyear cost per QALY gained after revision surgery was determined.
RESULTS: The duration between ACDF and subsequent surgery
for ASD was 5.1±6.1 years. Surgeries performed for ASD included
adjacent ACDF (78%), anterior corpectomy and fusion (6%),
posterior decompression and fusion (14%), and combined
anterior and posterior procedures (2%). A mean cumulative twoyear gain of 0.47 QALYs was observed after surgery for ASD. The
two-year cost of surgery for ASD was $34,689±26,875 (direct cost:
$27,921±10,989; indirect cost: $6,777±22,496, Table 1). Surgery was
associated with a mean two-year cost per QALY gained of $73,260.
DISCUSSION AND CONCLUSION: The surgical treatment for
symptomatic cervical ASD after ACDF resulted in a significant
improvement in quality of life after two years. Further, the twoyear cost per QALY gained of $73,260 suggests that surgery
to address ASD after ACDF is a cost-effective intervention.
974
uAdjuncts in Posterolateral Lumbar Spine Fusion: How
Does Bone Morphogenetic Protein-2 Stack Up to the
Gold Standard?
INTRODUCTION: Solid osseous fusion is an integral component
of the surgical management of degenerative diseases of the lumbar
spine. Iliac crest bone autograft is considered the gold standard
for bone graft and fusion procedures. Pseudarthrosis can, in turn,
lead to persistent pain, failure of the procedure, and the need for
revision surgery. Instrumentation for optimizing mechanical
variables has been proven as useful. Additional optimization
of biological variables is warranted. The use of osteobiologics
to enhance fusion has therefore become an important role in
these procedures. Especially rhBMP-2 in combination with
bone void fillers for posterolateral intertransverse process fusion
has been studied and became more popular over time because
of the need for a high bonegraft amount for this procedure.
The adjunctive use of rhBMP-2 has been criticized because of
higher costs, lacking FDA approval, and possible complications.
Demineralized bone matrix (DBM) has also been advocated as
fusion enhancement with a wider variety of FDA approval and
approximately 80% lower costs. The purpose of this study was to
define the efficacy of rhBMP-2 and DBM compared to autograft
in posterolateral spine fusion by comparing complication rates.
METHODS: During a seven-year period of time (2002-2009),
all patients undergoing lumbar posterolateral fusion were
retrospectively evaluated within a large orthopaedic surgery
private practice. Patient demographics, comorbidities, number
of levels, type of surgery, and types of bone void filler (BVF)
and osteobiologics were analyzed. Complications were defined
as reoperation secondary to failed symptomatic fusion, hyper
reaction resulting in compressive fluid collections, hyper
formation of bone resulting in neural compression, and infections.
RESULTS: A total of 1,398 consecutive patients were evaluated
with 575 (41.1%) males and 823 (58.9%) females. Average age
was 60 yo and BMI was 30.6 kg/m². The patients were subdivided
in treatment groups: rhBMP-2, 947 (67.7%), DBM 306 (21.9%),
and autograft 145 (10.4%). Mean length of hospital stay was 5.03
days for all groups combined. There was no significant difference
in length of stay between patients who underwent additional
iliac crest bone grafting and who did not (5.1 days vs. 5.03 days
respectively). The overall infection rate was 2.1%. No statistical
significant differences were found between the three groups
(χ²=0.488, χ²=0.739, and χ²=0.872, respectively). The incidence
of seroma formation was higher in the BMP group (3.2%) than
in the DBM or autograft group (2.0% and 1.4%, respectively)
but this was not statistically significant (χ²=0.286 and χ²=0.245,
respectively). A total of 103 patients (7.4%) underwent redo surgery
for clinically significant nonunion. We found significantly fewer
nonunions (4.3%) in the rhBMP-2 group (χ²<0.001) compared
to the DBM or autograft group (13.1% and 15.2%, respectively).
DISCUSSION AND CONCLUSION: Iliac crest bone graft is the
gold standard. Additional demineralized bone matrix leads
to comparable fusion rates and does not increase infection or
seroma formation. rhBMP-2 supplementation instead of ICBG or
bone marrow aspirate results in higher fusion rates compared to
autograft alone or autograft plus DBM.
PAPER NO. 575
Clinical Predictors of Psychological Distress in Patients
Presenting for a Spinal Evaluation
Michael D. Daubs, MD, Salt Lake City, UT
Jacob R. Adams, MD
Man Hung, PhD
Alpesh A. Patel, MD, Maywood, IL
Brandon Lawrence, MD, Salt Lake Cty, UT
Ashley Woodbury, BS
Darrel S. Brodke, MD, Salt Lake City, UT
INTRODUCTION: A recent study showed that spinal surgeons
are not very accurate in assessing patients for psychological
distress when compared to a validated screening questionnaire. A
majority of spinal surgeons do not routinely use a psychological
screening tool, but instead rely on their clinical impression
alone to assess a patients psychological distress level. Our
hypothesis is that a patient’s level of psychological distress can
be predicted utilizing readily available clinical information. The
purpose of our study was to determine the clinical information
that might predict a patient’s level of psychological distress.
METHODS: We studied 388 patients who presented to a tertiary
spine center for an initial evaluation. All patients prospectively
completed the Distress Risk Assessment Method (DRAM)
psychological questionnaire to determine their level of psychological
distress. We reviewed the medical records to record the Oswestry
Disability Index (ODI), the Visual Analogue Scale (VAS), patients’
current diagnosis, medical history, surgical treatment history and
current medications to determine which clinical factors predicted
a high distress level. We constructed classification trees utilizing
data mining to examine these factors as predictors. The prediction
model was then tested and retested for its accuracy and precision.
RESULTS: Our results show that ODI was the most critical
predictor for psychological stress. VAS also played an important
role in the prediction. Patients whose ODI was less than 45 and
VAS was less than 3, were more likely be in the normal group.
Those who had prior surgery and whose ODI was between 45
and 58 were more likely to be at risk psychologically. Patients
who had prior surgery and whose ODI was greater than 58,
were more likely to be in the highly distressed categories.
Measures of our model accuracy and precision were all well
above 80%, suggesting that our predictions were highly robust.
Discussion: ODI and VAS scores are highly predictive of a patients
level of psychological distress. Patients with ODI scores greater than
58 were highly likely to be in the severely psychologically distressed
975
categories, while patients with ODI scores less than 45 were more
likely to be in the normal category. Conclusion: The clinical
information that was most predictive of greater psychological
distress was the ODI and VAS scores. Higher ODI and VAS scores
predicted higher levels of psychological distress.
PAPER NO. 576
Surgical Treatment of Scoliosis in Spinal Muscular
Atrophy: Complications in a 10 Years Follow-up Study
Francesco Turturro, MD, Rome, Italy
Antonello Montanaro, MD, Rome, Italy
Luca Labianca, MD, Rome, Italy
Vincenzo Di Sanzo, MD, Rome, Italy
Andrea Ferretti, Rome, Italy
INTRODUCTION: There are no reports describing and comparing
complications with posterior spinal fusion (PSF) with Luque’s or
hybrid instrumentation in patients with neuromuscular scoliosis.
METHODS: Our experience includes 192 consecutive
neuromuscolar scoliosis surgically treated by the same surgeons,
using Luque’s (132) or hybrid (60) instrumentation (49 Cerebral
Palsy, 44 Muscular Dystrophy, 29 Spinal Muscular Atrophy,
14 Rett Syndrome, 11 poliomyelitis and 48 others) that were
divided in two groups according to surgical instrumentation
and within each group, for severity of curves in subgroup I
(<90º) and subgroup II (>90º). Perioperative (within three
months of surgery) and postoperative (after three months of
surgery and every two years) complications were retrospectively
reviewed. In 125 patients, pelvic fixation was performed.
RESULTS: Mean follow up was 9.7 years (range3-17). There were
30 major complications (15,1%) and 59 minor complications
(30,7%). Respiratory diseases requiring tracheotomy and
ICU care, hardware failure, neurological injury, deep wound
infection and death were major complications; while atelectesis,
pneumonia, mild pleural effusion, UTI, ileus, vomiting, gastritis,
tingling sensation or radiating pain in lower limb, superficial
infection and wound dehiscence were minor complications.
Fifty-eight (31%) patients had at least one major or one minor
complication. There were, within major complications, two
deaths, one due to cardiac arrest and one due to hypovolemic
shock, 15 deep infections, three tracheotomy, two paraplegias,
eight hardware removing. All but one hardware major failures
were described in patients with Luque instrumentation.
DISCUSSION AND CONCLUSION: The amount of complications
in the surgery of neuromuscular scoliosis is still remarkable.
Maybe the focus is to better understand what we mean
by complication. In our opinion, complication should be
anything that avoids or modifies the result of treatment. A good
knowledge of possible complications can’t avoid complications
but could help the surgeon in prompt choice of treatment.
of ASD correction has cost-effectiveness ratios above accepted
thresholds (>$50,000) at short-term follow up. The durability
of surgical correction may bring the cost of treatment into an
accepted range with long-term follow up. A thought experiment
estimating outpatient expenditure and revision surgery cost over
a 10-year follow up will be demonstrated. Non-operative patients
are unlikely to improve on outcome scores while operative patients
likely maintain their improvement despite relatively high revision
rates. The possible result is an economic benefit of surgical
management when considered over the patient’s lifetime.
PAPER NO. 578
Failure of Pelvic Fixation after Long Construct Fusions
in Adult Deformity Patients and Its Risk Factors
PAPER NO. 577
Adult Spinal Deformity: A Two-year Cost-Utility
Analysis and 10-year Thought Experiment
Daniel Warren, MD, New York, NY
Christian M. Hoelscher, BS, New York, NY
Jamie S. Terran, BS, New York, NY
INTRODUCTION: Adult spinal deformities (ASD) are disabling
conditions. Surgical management of ASD has demonstrated
effectiveness in clinical outcome scores. Despite this, the surgical
management has come under fire within the landscape of escalating
healthcare expenditure due to the cost of acute management. A costutility analysis of operative ASD patients comparing pre-operative
and post-operative outcome scores has never been performed.
METHODS: A total of 233 patients undergoing primary surgery
for ASD including Idiopathic Scoliosis (IS, n=189), Degenerative
Scoliosis (DS, n=39) and Congenital Scoliosis (CS, n=5) were
reviewed. We report pre and post-operative outcome scores (SRS,
ODI) with two years follow up. Quality Adjusted Life Years (QALYs)
were calculated based on reported regression formulas. Medicare
DRG hospital and CPT physician (surgeon, anesthesia and
neuromonitoring) re-imbursement codes were used to establish
an acute care cost (ACC). The ACC and QALY values are used to
perform a cost-utility analysis of the operative intervention for ASD.
RESULTS: DS patients were significantly older (62.2) vs. IS (47.9)
but not CS (44.2). Height and weight were similar. DS patients
were more likely to have osteoarthritis, leg pain, and leg pain with
ambulation (p<0.05). IS patients had a significantly lower pre-op
ODI and a higher corresponding utility score vs. DS patients. Preoperative SRS scores were similar. At two year follow up, all groups
improved on ODI and in each domain of SRS. The only significant
difference on SRS was higher mental health scores in DS vs. IS. Postoperative utility values were similar. Total QALYs gained at two
years were significantly greater for DS (0.20) vs. IS (0.12), but not
vs. CS (0.11). Total reimbursements averaged $35,883, $37,482, and
$38,787, respectively. At two years, the cost/QALY was $299,025 for
IS, $187,410 for DS, and $352,609 for CS. Single revision surgery
rate within two years was 20.6% and multiple revision was 3.9%.
DISCUSSION AND CONCLUSION: Our results confirm that
surgical correction improves patient outcome in ASD. High ACC
976
Woojin Cho, MD, New York, NY
Jonathan R. Mason, MD, Charlottesville, VA
Adam S. Wilson, MD, Charlottesville, VA
Francis H. Shen, MD, Charlottesville, VA
Adam L. Shimer, MD, Charlottesville, VA
Wendy Novicoff, PhD, Charlottesville, VA
Kaiming G. Fu, MD, PhD, Charlottesvle, VA
Joshua E. Heller, MD, Philadelphia, PA
Vincent Arlet, MD, Charlottesville, VA
INTRODUCTION: Pelvic fixations provide biomechanical support
to the base of the long constructs used for adult deformity. However, the
failure rate of the pelvic fixation and its risk factors are not well known.
METHODS: The retrospective review included 190 adult deformity
patients who had long construct instrumentation (> 6 levels)
with iliac screws. Patients’ clinical and radiographic data were
analyzed. Patients were divided into two groups: Failure (F) and
Non-Failure (N-F). A minimum two-year follow up was required
for inclusion in the N-F group. In the F group, regardless of the
failure occurred before or after two years, all patients were
included in the study. In both groups, the patients who needed
a revision due to causes other than pelvic fixation failure before
two years were also excluded (e.g. PJK). Failures were defined as
major and minor. Major F included rod breakage between L4 and
S1, failure of S1 screws (breakage, halo formation, or pullout), and
prominent iliac screws requiring removal. Minor F included rod
breakage between S1 and iliac screws and failure of iliac screws.
Minor F did not require revision surgery. Multiple clinical and
radiographic values were compared between Major F and N-F.
RESULTS: Out of 190 patients, 67 patients met inclusion criteria
and were enrolled. Overall F rate was 34.3%: eight patients in
Major F (11.9%) and 15 patients in minor F (22.4%). Major F
occurred at a statistically significant greater rate in those patients
who had previous lumbar surgery, greater pelvic incidence
(PI), and poor restoration of lumbar lordosis and/or sagittal
balance (i.e. undercorrection). Patients with a higher number
of co-morbidities and preoperative coronal imbalance showed
trends toward an increase in major F although these trends did
not reach statistical significance. Age, sex, body mass index,
smoking history, number of fusion segments, fusion grade, and
several other radiographic values were not shown to be associated
with increased risk of major failure. A total of 87.5% of patients
in the Major F group had anterior column support (ALIF or
TLIF) while 84.1% of the N-F had anterior column support.
DISCUSSION AND CONCLUSION: The incidence of overall
failure was 34.3%, but the clinically significant major failure after
pelvic fixation in adult deformity surgery was 11.9%. Risk factors
for major failures are a larger PI, revision surgery, and failure to
restore lumbar lordosis and sagittal balance. Adult deformity
surgeons who use pelvic fixation for long level fusions should
know the incidence of pelvic fixation failure and be familiar with
the clinical and radiographic risk factors identified in this study.
deficit and the involvement of L1-2, L2-3, L3-4 was found (six
weeks (p=0.347), 12 weeks (p=0.999) and six months (p=0.999),
12 months (p=0.817). There is an association between the
numbers of levels fused and the persistent nerve injury (12 months
follow up p<0.001). Bone graft material do not have an influence
on sensory or motor deficit at any time point. The multivariate
logistic regression model showed an independent association of
the following risk factor for a motor deficit at six weeks: gender
(female), duration of surgery, BMI (>30) and involvement of L 4-5.
DISCUSSION AND CONCLUSION: LLIF remains a valuable tool
for achieving fusion through a minimally invasive approach with
little risk to neurovascular structures. Approach related iliopsoas
weakness remains a common postoperative deficiency.
PAPER NO. 580
uThe Prevalence of Cervical Cord Compression Using
Mobile MRI in Local Inhabitants: The Road-MRI Study
PAPER NO. 579
Sensory and Motor Deficit Following Lateral Lumbar
Interbody Fusion
Matthias Pumberger, MD, Berlin, Germany
Suhel Kotwal, MD, Houston, TX
Arvind G. Von Keudell, MD, Chestnut Hill, MA
Michael Mayer, MD, Salzburg, Austria
Alexander P. Hughes, MD
Andrew A. Sama, MD, New York, NY
Frank P. Cammisa, Jr, MD, New York, NY
Federico P. Girardi, MD, New York, NY
INTRODUCTION: Lateral lumbar interbody fusion (LLIF) as
a minimally-invasive technique has gained growing interest
in recent years. However, one of the procedure’s limitations
remains the unknown incidence of sensory and/or motor deficit
following a trans-psoatic approach. We seek to identify the
incidence and nature of neurological events following LLIF.
METHODS: We performed a retrospective of 247 patients charts
undergoing LLIF between 2006 and 2009. We identified the
new onset of anterior thigh pain, sensory and motor deficit.
Each sensory deficit was reported to the according dermatome.
Motor deficits were divided into the muscle movement. Patient
charts were reviewed for demographics, medical co-morbidities,
subjective neurological complaints, and physical exam findings at
the following time points: pre-, peri- and post-operatively at six
weeks, three, six and 12 months follow up. The specific deficits
were correlated to the side and level of approach, numbers of levels
fused, length of surgery, and bone graft material employed. A
multivariate logistic regression models were created to evaluate the
independent associations of each potential explanatory variable.
RESULTS: A total of 237 patients (139 female, 98 male) underwent
LLIF surgery at our institution with a total of 463 levels fused.
Average age 61.5 years (range 31-88) and mean body mass index
(BMI) was 28.3 (range 17.4-60.3). At six weeks, 41.4%, 16.0% at
12 weeks, 3.7% at six months and 0.8% at 12 months experienced
thigh pain after surgery. We found a significant correlation
between the involvement of L 4-5 and the occurrence of motor
deficits at six weeks (p=0.009), 12 weeks (p=0.009) and 12
months (p=0.027). However, no correlation between a sensory
977
Keiji Nagata, Wakayama City, Japan
Hiroshi Hashizume, MD, Wakayama, Japan
Shigeyuki Muraki, PhD, MD, Tokyo, Japan
Yuyu Ishimoto, Wakayama, Japan
Hiroshi Yamada, MD, Wakayama, Japan
Noboru Takiguchi, Wakayama City, Japan
Hiroyuki Oka, MD
Toru Akune, MD, Tokyo, Japan
Noriko Yoshimura, MD, Tokyo, Japan
Munehito Yoshida, MD, Wakayama, Japan
INTRODUCTION: Cervical cord compression (CCC) is a
regressive and degenerative disorder caused by various factors
surrounding the spinal cord, such as disc degeneration, thickening
of facet joint and osteophyte, and it develops symptoms of the
spinal cord compression, that is - cervical myelopathy (CM).
Population-based cohort studies of the prevalence of CCC,
although essential for the clarification of the prevalence of slowly
progressive disease and specification of the time of incidence of
CCC, are not available. CM has a significant influence on physical
performance, i.e., finger motion, standing balance, and walking
speed. We aimed to investigate the prevalence of CCC using MRI
and to examine the association between CCC and myelopathic
signs/physical performance in a large population-based study.
METHODS: This cross-sectional study was part of the Japanese
Research on Osteoarthritis/Osteoporosis Against Disability
(ROAD) study. Residents (1,011; 336 men and 675 women) of a
coastal area and a mountain region were recruited. After exclusion
of individuals with disqualifications, 977 participants (324 men;
653 women) were evaluated using MRI of the cervical spine.
All participants underwent anthropometric measurements and
physical examinations. CCC was assessed using sagittal MRI
and was defined as compression with anterior and/or posterior
component of the spinal cord. We examined the prevalence of CCC
and its association with myelopathic signs (patellar hyperreflexia,
Hoffmann reflex, and Babinski reflex). Physical performance (gripand-release test (GRT), grip strength, six m walking time (at usual
and maximal pace), step length (at usual and maximal pace), chairstand time (CST), and one-leg standing time (OLS)) was also tested.
The prevalence of myelopathic signs and physical performance
were compared between participants with and without CCC. A
multiple logistic regression analysis (after adjustment for age,
gender, and body mass index (BMI)) was used to determine the
association between physical performance parameters and CCC.
RESULTS: The mean age of the participants was 67.2 ± 13.9 (men)
and 66.0 ± 13.4 (women) years. The prevalence of CCC (24.4%)
was significantly higher in men (29.3%; vs. 21.9% in women; P
= 0.011) and increased with age in men and women (Figure 1).
CCC was most recognized at the C5/6 level, followed by C4/5 and
C6/7, in men and women. CCC was not significantly associated
with myelopathic signs, with the exception of the Babinski reflex
in women. Each physical performance parameter was significantly
different between participants with and without CCC. The GRT
(odds ratio (OR), 0.96; 95% confidence interval (CI), 0.93-0.99;
P = 0.02), six m walking time at maximal pace (OR, 1.19; 95%
CI, 1.06-1.35; P = 0.003), step length at usual pace (OR, 0.98;
95% CI, 0.96-0.99; P = 0.01), step length at maximal pace (OR,
0.97; 95% CI, 0.96-0.99; P = 0.002), and CST (OR, 1.06; 95%
CI, 1.02-1.10; P = 0.007) were significantly associated with CCC.
DISCUSSION AND CONCLUSION: This ROAD/MRI study
clarified the prevalence of CCC and suggests that CCC has a
significant influence on physical performance from an early stage,
before myelopathic signs become clear.
PAPER NO. 581
uRetrograde Ejaculation Following Lumbar Anterior
Interbody Fusion Using rhBMP-2: A Cohort Controlled
Study
Kyle A. Mitsunaga, MD, Sacramento, CA
INTRODUCTION: The commercially available growth factor
rhBMP-2, used in spinal fusion, has been associated with numerous
adverse reactions including inflammatory reactions in soft tissue,
heterotopic bone formation, radiculitis, osteolysis and cage or
graft subsidence. The original FDA report of anterior lumbar
interbody fusion found 11 retrograde ejaculation events (7.9%) in
the rhBMP-2 groups compared with (1.4%) in the control group. It
had been debated whether this finding was related to rhBMP-2 use.
METHODS: From the comprehensive outcome database at a
high volume university practice, male subjects having anterior
lumbar interbody fusion (ALIF) for one (L5/S1) or two level (L4/5,
L5/S1) lumbar fusion were identified. Retrograde ejaculation
events were recorded and comparative incidence compared.
RESULTS: The two groups were comparable for age and additional
procedures performed. There were 155 single-level L5/S1 ALIFs
performed during the study period: 45 with using rhBMP-2 and
110 ALIFs without rhBMP-2. There were 24 and 64 were two-level
ALIFs performed with and without rhBMP-2, respectively. There
were five retrograde ejaculation events (7.2%) reported in the
rhBMP-2 group and one (0.6%) in the control group (p = 0.0025).
Comparing single level L5/S1 ALIF, there was a 6.7% and 0% rate
978
of retrograde ejaculation rate in the rhBMP-2 versus control groups,
respectively (p = 0.023). At one year after surgery, three of six
affected subjects reported resolution of the retrograde ejaculation.
DISCUSSION AND CONCLUSION: This study confirms previous
reports of a significantly higher rate of retrograde ejaculation in
ALIF procedures using rhBMP-2 and a retroperitoneal approach.
This may be an important consideration in patients concerned
with sterility after surgery.
PAPER NO. 582
Lenke 1C and 5C Spinal Deformities Fused Selectively:
A Natural History of Uninstrumented Compensatory
Curves
Ryan M. Ilgenfritz, MD, Iowa City, IA
Burt Yaszay, MD, San Diego, CA
Tracey Bastrom, MA, San Diego, CA
Peter O. Newton, MD, San Diego, CA
INTRODUCTION: Following a selective fusion for 1C and
5C AIS curve types, there is concern that uninstrumented
compensatory curves will continue to progress over time.
We analyzed the natural history of the uninstrumented
compensatory curves over a five-year post-operative period.
METHODS: Lenke 1C and 5C AIS cases, prospectively collected
from a multi-center study, were analyzed. All patients underwent a
selective fusion (1C only thoracic curve fused; 5C only thoracolumbar/
lumbar curve fused). Pre-operative, first erect, one-year, two-year,
and five-year post-operative coronal, sagittal and axial (Perdriolle)
radiographic outcomes were compared utilizing repeated measures
ANOVA with Bonferroni post hoc comparisons (p<0.05).
RESULTS: Twenty-four selectively fused Lenke 1C curves and 21
selectively fused Lenke 5C curves were available for review. Preoperative compensatory curve Cobb angles were 40± 6° and
25 ± 9° respectively. In Lenke 1C curves, the uninstrumented
compensatory lumbar curves corrected by 32 ± 16% (p<0.001)
at first erect, 44 ± 17% correction at one year (p=0.006), 38 ± 15
% correction (p=0.020) at two years, and 39 ± 19% at five years
(p=0.792). In Lenke 5C curves, the uninstrumented compensatory
thoracic curves corrected by a mean of 37 ± 29% (p<0.001) at
first erect, 42 ± 29% (p=0.742) at one year, 37 ± 29% (p=0.184)
at two years, and 30 ± 23% (p=0.412) at five years. The relative
magnitudes of the primary and compensatory curves in both Lenke
1C and 5C cases were different pre-op and at the first erect time
point (four to six weeks), then became and reMEd similar from
one to five years postop (Figure). The sagittal and axial measure
of the compensatory curve reMEd stable during the postop
period. All patients at five years post-operative were Risser 4 or 5.
DISCUSSION AND CONCLUSION: In Lenke 1C and 5C AIS
deformity patterns fused selectively, the uninstrumented
compensatory curves adjust to match the instrumented primary
curve and do not seem to progress between one and five years
post-operatively. Longer follow up on a larger number of patients
will be necessary in order to evaluate concern for progression of
uninstrumented compensatory curves beyond five years postoperatively.
PAPER NO. 584
Military Penetrating Spine Injuries Compared to Blunt
James A. Blair, MD, San Antonio, TX
Daniel R. Possley, DO, San Antonio, TX
Joseph L. Petfield, MD, Fort Sam Houston, TX
Joseph R. Hsu, MD, San Antonio, TX
PAPER NO. 583
Congenital Scoliosis: A Single Institution Experience
with Long-term Follow Up
Daniel J. Sucato, MD, Dallas, TX
Anna McClung, RN, Dallas, TX
Andrew Matthys, El Paso, TX
James Shaha, MD
INTRODUCTION: Congenital scoliosis is a challenging
spinal deformity to treat surgically. There are few
studies which have analyzed a large cohort of patients
to determine the long-term outcome of these patients.
METHODS: An Institutional Review Board-approved retrospective
review of a consecutive series of patients who had congenital
scoliosis from a single institution was performed. The medical record
was carefully reviewed to determine demographic information,
the surgical procedure, and complications. The radiographs
were reviewed to determine the type of congenital scoliosis, and
standard coronal and sagittal measurements were performed.
There was an average postoperative follow-up of 6.5 years.
RESULTS: There were 139 patients who had surgery between 1980
and 2004. The average age at surgery was 9.5 years (0.8 to 18 years)
and the average age at follow up was 16 years (3.6 to 21.7 years of
age). Neural axis abnormalities were noted in 31 (22.3%). There
were a similar distribution of males and females (51.6 vs. 48.4%).
The procedures were posterior fusion-63, anterior/posterior
fusion-49, hemivertebra excision seven, anterior fusion 13,
hemiephysiodesis four and miscellaneous three. The patients were
divided into three groups; Group HB-multiple hemivertebra±bar
(n=28), H-single hemivertebra (n=35), J-Jumbled Spine-(several
congenital abnormalities) (n=75). There were no differences
in the three groups with respect to preoperative major Cobb
(57.3° HB, 50.0° H, 54.8° J), major curve percentage correction
at two years (13.5% HB, 25% H, 22.4% J) and five years (4.4%
HB, 12.4% H, 8.2% J) postoperatively. Good coronal balance
was seen more often in the HB (75.0%, 67.9%), and H (76.5%,
67.7%) than the J (56.3%, 58.0%) group using C7-CSVL and trunk
shift measurements, respectively at final follow up. All groups
showed improved sagittal balance over preop at final follow up
(2.7 vs. 2.2cm HB, 3.4 vs. 2.7cm H, and 3.3 vs. 2.6cm J). There
were no differences between groups with respect to neurologic
complications, incidence of pseudoarthrosis, or curve progression.
DISCUSSION AND CONCLUSION: Patients with congenital
scoliosis undergoing surgical treatment overall have good outcomes
with respect to curve correction; however, greater involvement
of the spine with respect to congenital abnormalities may lead
to greater coronal plane imbalance at a minimum of five years.
Careful consideration of fusion levels and amount of correction is
necessary to achieve a balanced patient.
979
INTRODUCTION: The nature of blunt and penetrating
injuries to the spine and spinal column in Iraq (Operation
Iraqi Freedom) and Afghanistan (Operation Enduring
Freedom) has been poorly documented in the literature.
METHODS: The Joint Theater Trauma Registry (JTTR) was
queried for all American service members sustaining an injury
to the spinal column or spinal cord while deployed in Iraq or
Afghanistan. This data was manually reviewed for relevant
information regarding demographics, mechanism of injury,
concomitant injuries, surgical intervention, and neurologic injury.
RESULTS: A total of 598 service members sustained injuries to
the spine or spinal cord. Isolated blunt injuries were recorded
in 396 (66%) service members and 165 (28%) sustained
penetrating injuries. Thirty service members (5%) sustained
combined blunt and penetrating injuries to the spine. The most
commonly documented injuries were transverse process fractures,
compression fractures, and burst fractures in the blunt-injured
service members versus transverse process fractures, lamina
fractures, and spinous process fractures in those injured with a
penetrating injury. One-hundred-four (17%) service members
sustained spinal cord injuries, resulting in 10% of blunt injuries
and 38% of penetrating injuries (p<0.0001). Twenty-eight percent
(28%) of blunt-injured service members underwent a surgical
procedure compared to 41% of those injured by penetrating
mechanisms (p=0.4). Sixty percent (n=12/20) of blunt-injured
service members experienced a neurologic improvement after
surgical intervention at follow up compared to 43% of service
members (n=10/23) that underwent a surgical intervention
after a penetrating trauma (p=0.28). Explosions accounted
for 58% of blunt injuries and 47% of penetrating injuries,
while motor vehicle collisions accounted for 40% of blunt
injuries and 2% of penetrating injuries. Concomitant injuries
to the abdomen, chest, and head were common in both groups.
DISCUSSION AND CONCLUSION: Blunt and penetrating
injuries to the spinal column and spinal cord occur frequently in
the current conflicts in Iraq and Afghanistan. Penetrating injuries
result in significantly higher rates of spinal cord injury and trend
towards increased rates of operative interventions and decreased
neurologic improvement at follow up.
PAPER NO. 585
Negative Effects of Smoking and Secondary Gain Issues
on Pain and Disability Scores at Entry into Spine Care
Mark L. Prasarn, MD, Houston, TX
MaryBeth Horodyski, EdD, ATC, LAT, Gainesville, FL
Glenn R. Rechtine, II, MD, Pinellas Park, FL
INTRODUCTION: Back pain is a complex clinical and
social issue. Smoking and secondary gain (SG) have been
shown to predict poor treatment outcomes. This study
examines the impact of smoking and SG on disability and
pain scores at initiation of treatment for a spinal disorder.
METHODS: Following approval from the Institutional Review
Board, the medical records of 13,704 consecutive patients treated
at two university spine centers were reviewed to assess effects of
smoking and SG at the time of presentation. All patients completed
a questionnaire that included a modified ODI, VAS (current pain,
worst pain, least pain, and average pain over the week preceding
the baseline visit), smoking history, and secondary gain issues.
Patients reporting workers comp, motor vehicle crash, disability,
or malpractice were recorded as having secondary gain. Smoking
history was broken down as current smokers (CS), previous
smokers (PS), and no smoking (NS) history. ANOVAs with
Bonferroni (when appopriate) were used to analyze the data.
RESULTS: The ODI scores correlated with smoking history
directly CS>PS>NS (44.22>38.11>36.02). These results were
significant with pPS>NS. Within the calculation, SG and
smoking combined to create even higher scores. The statistical
significance was p<0.001 between CS and NS, and CS and
PS. There was no significant difference between PS and NS.
DISCUSSION AND CONCLUSION: This study demonstrates
that smoking and SG at entry to treatment contribute to poorer
outcomes in spine patients. The combination of smoking and SG
is additive in negative effect. While a six point difference in ODI
would not be considered clinically significant for an individual
patient, it is a dramatic difference for this sample size. Also of
note, PS had poorer scores than NS (significant for the ODI but
not pain scores). Smoking cessation and treatment addressing
psychological and social factors is imperative for optimal outcome
in spine patients.
include major and minor diameter, presence of tapering and
thread design. An optimal screw design can therefore be selected
based on the results of these comparisons for use in osteoporotic
bone. Optimized thread design produced a pullout strength 124N
greater than typical threads in osteoporotic foam. It is important
to know the specific design criteria for a pedicle screw in order to
understand which features result in an increased pullout strength.
It may be possible to design a pedicle screw to improve success
rates of spinal surgery in osteoporotic patients, hence reducing
postoperative implant related complications and revision surgery.
PAPER NO. 631
Optimal Pedicle Screw Thread Design for Use in
Osteoporotic Bone
INTRODUCTION: Standardized pullout testing was performed
per ASTM standards on a variety of pedicle screws to choose screw
design criteria that enhance holding power in osteoporotic bone.
METHODS: Thirteen different pedicle screws with unique
thread designs were analyzed. Each screw was tested per ASTM
F543 using three densities of foam blocks (n=30). One foam
density was chosen to mimic osteoporotic bone. A total of 1,170
tests were completed and the results collected and analyzed for
quantitative ranking. Screw pullout strength and insertion torque
for each individual test were collected during this experiment.
RESULTS: Insertion torque was highly correlated with pullout
strength for all foam densities tested; r2 = 0.80 to 0.89. The
length of the screw inserted was not a factor; r2 =0.003 to
0.012. Screw diameters (major and minor) showed a weak
correlation; r2 = 0.60 to 0.70. T-testing on the presence or
absence of a taper showed a statistical difference with tapered
screws displaying lower pullout strength in all densities of foam.
T-testing of single vs. dual lead pedicle screws demonstrated
dual leads had lower pullout strengths in osteoporotic foam.
DISCUSSION AND CONCLUSION: Pullout testing data were
compared to screw design characteristics in order to correlate
important screw parameters to screw pullout strength. Parameters
identified that affect pullout strength in an osteoporotic model
980
PAPER NO. 632
Whole Exome Sequencing of DNA from Patients with
Abnormal Responses to rhBMP-2 Assisted Spinal
Arthrodesis
Khaled M. Kebaish, MD, Baltimore, MD
Oheneba Boachie-Adjei, MD, New York, NY
Mark D. Rahm, MD, Temple, TX
Marilyn Gates, MD, Detroit, MI
Hani Mhaidli, MD, Gran Canaria, Spain
Donald A. Deinlein, MD, Birmingham, AL
Kenneth J. Paonessa, MD, North Franklin, CT
Gordon D. Donald, MD, Eatontown, NJ
Victoria Zismann, Phoenix, AZ
Paula Davidson, Grand Rapids, MI
Bart Williams, PhD, Grand Rapids, MI
Jeffrey Kiefer, PhD, Phoenix, AZ
James Mason, PhD, Grand Rapids, MI
Jeffrey M. Trent, PhD, Grand Rapids, MI
INTRODUCTION: Despite high fusion rates, the use of rhBMP-2 for
spinal arthrodesis remains controversial due to its “off-label” use,
cost, and reported complications. Altered responses to rhBMP-2
have not been fully elucidated. The hypothesis of this study was
that genetic variations explain the altered response to rhBMP-2.
METHODS: A total of 1,412 patients were identified that
underwent spinal arthrodesis from 2003-2009 at a Level I trauma
center. Complications related to rhBMP-2 were defined as hyper
reaction resulting in compressive fluid collections (37, 2.6%) and
reoperation secondary to failed symptomatic fusion (35, 2.5%). To
test the hypothesis, isolated DNA was collected from the patients
with complications and age- and gender-matched controls for exome
sequencing to identify genetic variations associated with these
abnormal responses to BMP treatment. Exomes from five hyperresponders and one hypo-responder were indexed and hybridized
and then sequenced to approximately 432x coverage. There were a
total of over 18.8 billion high quality bases called, 98.4% of which
aligned to the reference genome with an average error rate of 0.3%
per sample. Raw reads were converted to standard format using
software and custom scripts. Barcoded reads were split and all reads
for each sample were collected together. Reads were aligned to
reference human genome (build 36). Alignment were processed to
remove duplicates, recalibrate the quality scores, and sorted using a
custom scripts and software tools. Processed alignments were used
for variant calling using two callers_samtools and varscan. Only
those variants in coding regions that were picked up by both callers
were retained and annotated with gene names and other attributes.
RESULTS: A supervised approach was employed to look for
variants that mapped to BMP signaling and bone related biological
concepts. Of note, in the BMP hyper-responders, non-synomous
SNPs were identified in the genes FOS, ATF4 and SMAD9.
Additionally, two variants in calcium channel genes (CACNA1S and
CACNB1) were identified. Interestingly, the one hypo responder
variant, from our supervised list, was in the gene CACNB2.
DISCUSSION AND CONCLUSION: Whole exome sequencing
was utilized to identify genetic variations that may be associated
with an abnormal response to rhBMP-2 assisted spinal arthrodesis.
CACNB2, a calcium channel isoform, has previously not been
linked to alterations in bone biology, but has been linked to
cardiac muscle function. The functional consequences of the listed
variants awaits further experimental validation. Current work is
aimed at sequencing the exomes of additional individuals with
these abnormal responses and validating the potential biological
relevance of candidate genes identified in our preliminary analysis.
This may provide the foundation to support pre-operative genetic
screening to guide indication for rhBMP-2 use.
PAPER NO. 633
Demineralized Cancellous Allograft is Equivalent to
rhBMP-2 in Posterior Lumbar Interbody Fusion (PLIF)
Kade T. Huntsman, MD, Salt Lake City, UT
Steven M. Scott, MD, Salt Lake City, UT
Mauricio A. Berdugo, JR, MD, Salt Lake Cty, UT
Gregory A. Juda, Belgrade, Montana
Stephen G. Roper, Salt Lake City, UT
INTRODUCTION: An array of grafting materials has been used
in lumbar spinal fusion, including autograft, multiple types
of allograft, synthetic bone graft substitutes and recombinant
human bone morphogenetic protein (rhBMP-2). RhBMP-2
has demonstrated excellent rates of fusion in large series, but
associated side effects and safety concerns are being reported in a
growing body of literature. An FDA trial of rhBMP-2 in a posterior
lumbar interbody fusion (PLIF) application was halted due to
a 75% incidence of ectopic bone formation in the neural canal.
Despite these reports, rhBMP is still widely used off-label in PLIF
and transforaminal lumbar interbody fusion (TLIF) procedures,
constituting 30% of all rhBMP used in the U.S. from 2002-2007. The
purpose of this study was to prospectively evaluate whether a novel
cancellous form of DBM, when used with BMA, in a PLIF could
achieve fusion rates and clinical results equivalent to rhBMP-2.
METHODS: We randomized 28 consecutive patients undergoing
single and multi-level PLIF at one institution into two groups:
Group I, 16 patients with 33 levels fused, underwent PLIF using
cancellous DBM blocks soaked in iliac crest BMA and inserted
inside and between interbody cages, and Group II,12 patients
with 30 levels fused, underwent identical PLIF, using rhBMP-2.
Both groups also underwent identical posterior instrumentation
and posterolateral fusion. Clinical evaluation, quality of life
surveys and radiologic data were determined preoperatively.
At one year and two years post surgery, quality of life surveys,
X-rays and computed tomography (CT scans) were evaluated
in a blinded fashion. Fusion mass volume and continuity
981
were assessed on CT scan. CT scan attenuation, measured in
Hounsfield Units (HU), was used to measure fusion mass density.
RESULTS: The average age of the combined group was 63. Age and
comorbid conditions known to increase risk of failed arthrodesis
were similar in the two groups. There were no pseudoarthoses or
hardware failure in either group. At two years, average fusion mass
density for both groups, as measured by CT scan attenuation, was
greater than the adjacent vertebral bodies. Fusion mass densities
measured 199HU and 251HU for the DBM and rhBMP-2 groups
respectively (p=0.06). Subjective CT scan assessment of fusion
quality indicated no difference between groups (p=0.16). Visual
Analogue Scale (VAS) showed a marked increase in leg pain at one
year for the rhBMP-2 group (4.41) compared to the DBM group
(0.65) (p=.0006), but the difference normalized by two years.
The SF-36 v2 and Oswestry Disability Index scores showed no
statistical difference between the groups at one and two years.
DISCUSSION AND CONCLUSION: Blocks of demineralized
cancellous allograft soaked in BMA were equivalent to rhBMP-2 in
achieving successful fusion in PLIF when combined with posterior
instrumentation and posterolateral fusion in a small prospective
randomized controlled trial.
PAPER NO. 634
Combined Transplantation of Human Neuronal and
Mesenchymal Stem Cells Following Spinal Cord Injury
Don Y. Park, MD, San Francisco, CA
Robert E. Mayle, MD, Chicago, IL
R. L. Smith, PhD, Stanford, CA
Ian Corcoran-Schwartz, Palo Alto, CA
Alex Kharazi, MD, PhD
INTRODUCTION: Transplantation of human fetal neural stem
cells (hNSCs) has previously shown significant functional
recovery after spinal cord contusion in a rat model. Other
studies have indicated that human mesenchymal stem cells
(hMSCs) can home to areas of damage, cross the blood brain
barrier and migrate throughout the central nervous system.
hMSCs may produce a neuroprotective milieu at the site of
injury to reduce the effect of the injury. We hypothesized that
acute administration of hMSCs combined with subacute hNSCs
would enhance functional recovery in spinal cord injury.
METHODS: Female adult Long-Evans hooded rats underwent
laminectomy at the T10 level. A moderate spinal cord contusion
at the T10 level was induced by use of the MASCIS Impactor with
a 10g weight dropped from a height of 25mm. Four groups were
identified for this study. Group 1 received hMSCs intravenously
(IV) immediately after spinal cord injury (acute) and returned one
week later (subacute) for injection of hNSC directly at the site of
injury. Group 2 received hMSC IV acutely and cell media directly
subacutely. Group 3 received cell media IV acutely and hNSC
subacutely. Group 4 received cell media IV acutely and cell media
subacutely. Subjects were assessed functionally following injury and
then weekly for six weeks using the BBB Locomotor Rating Score.
RESULTS: Twenty-four subjects were utilized in this study, six subjects
in each group. A statistically significant functional improvement
was seen in the MSC+NSC group and the NSC-only group compared
with control (p=0.027 and 0.042 respectively), but the MSC-only
group did not demonstrate a significant improvement over control
(p=0.145, see Figure). Comparing the MSC+NSC group and the
NSC-only group, there was no significant difference (p=0.357).
DISCUSSION AND CONCLUSION: The subacute transplantation
of hNSCs into the contused spinal cord of a rat led to significant
functional recovery when injected either with or without the
acute IV administration of hMSCs. Neither the addition of hMSC
to hNSC treatment nor the delivery of hMSCs-alone resulted in
significant functional improvement. Although the use of hMSCs in
this study did not prove to be useful, future study may be necessary
to determine if the route and timing of administration may make
a significant difference.
Figure: BBB locomotor scores over time.
DISCUSSION AND CONCLUSION: Retrospective review and
comparison of complications and adverse events suggest the true
risk to patients receiving rhBMP-2 is conservatively 10 - 50 times
the original estimates calculated from industry-sponsored studies
published by authors with significant (>$9,000,000 per study)
financial associations with the manufacturer.
PAPER NO. 636
Modified Titanium Alloy Surfaces Induce Stem Cell
Osteogenic Differentiation
Barbara D. Boyan, PhD, Atlanta, GA
Rene Olivares-Navarrete, DDS, PhD, Atlanta, GA
Sharon L. Hyzy, BS, Atlanta, GA
Jennifer Schneider, MS, Mequon, WI
Rolando A. Gittens, MSc, Atlanta, GA
Peter F. Ullrich, Jr, MD, Neenah, WI
Zvi Schwartz, DMed, PhD, Atlanta, GA
PAPER NO. 635
Comparison of Adverse Events & Disclosures in the
Original rhBMP-2 Trials with FDA Data & Subsequent
Publications
Bradley K. Weiner, MD, Houston, TX
INTRODUCTION: There has been an appreciation in the spine surgery
literature of frequent and occasionally catastrophic complications
associated with use of rhBMP-2 in spine fusion surgeries of all types.
These adverse events were not reported or associated with rhBMP-2
use in the multiple industry-sponsored peer-review publications.
METHODS: Results and conclusions from original industrysponsored rhBMP-2 publications regarding safety and
efficacy were compared with available FDA data summaries,
follow-up publications, administrative and organizational
database analyses and possible conflict of interest disclosures.
RESULTS: There were 12 original industry-sponsored rhBMP-2
publications regarding safety and efficacy, including reporting and
analysis of 725 patients receiving rhBMP-2 on a prospective study
protocol. The average, minimum estimated financial association
with the manufacturer was $8,950,000 per study. Not one rhBMP-2
associated adverse event (0%) was reported in any of these studies
(99% CI of adverse event rate < 0.5%). Comparative review of
original FDA documents and subsequent publications revealed
many internal inconsistencies. A revised estimate of adverse-events
with rhBMP-2 use in the spine ranged from 5-15% with anterior
lumbar interbody fusion to 25-50% for posterior lumbar interbody
fusion techniques. Anterior cervical fusion with rhBMP-2 has an
estimated 40% greater risk of adverse events with rhBMP-2 in the
early postoperative period, including life-threatening events. In
posterolateral fusions the risk of adverse effects associated with
rhBMP-2 use was equivalent to or greater than that of iliac crest
bone graft harvesting. The high dose rhBMP-2 preparation in the
AMPLIFY product was associated with twice as many early serious
back and leg pain events and a greater risk of new malignancy
occurrence of approximately 90-95% probability (p < 0.10, >0.05).
982
INTRODUCTION: Direct integration of an implant with
surrounding bone, termed osseointegration, produces a biological
fixation that improves treatment success and long-term implant
stability. Peri-implant bone formation, which can be improved
by modifying the biomaterial surface, requires both osteogenesis
and angiogenesis to support newly formed bone. Titanium surface
roughness modifications (on a micro-scale) are known to play an
important role in enhancing in vitro osteoblast maturation and
increasing in vivo bone formation. While osteoblasts have been
demonstrated to be sensitive to changes in surface properties,
primary bone healing events are mediated by mesenchymal
stem cells (MSCs) and osteoprogenitor cells. The aim of the
present study was to elucidate whether two common spinal
fusion implant materials, PEEK and titanium alloy (Ti6Al4V),
induce MSC differentiation and whether they stimulate
cells to produce an angiogenic and osteogenic environment.
METHODS: Human MSCs were cultured on tissue culture
polystyrene (TCPS), PEEK, smooth Ti6Al4V [sTiAlV, Sa<90nm], or
rough Ti6Al4V [rTiAlV, Sa=1.81µm] surfaces. Cells were harvested
after seven days of culture. Cell number, alkaline phosphatase
activity (ALP) and secreted osteocalcin (OCN) were measured as
indicators of an osteoblastic phenotype. Levels of osteoprotegerin
(OPG), which prevents osteoclastic bone resorption, and TGFβ1,
an important modulator of osteoblasts and osteoclasts, were
measured to assess local factors. Secreted BMP2, BMP4, and
BMP7, and angiogenic factors VEGF, ANG1, and FGF2 were
analyzed in the conditioned media to assess osteogenic and
angiogenic environment. Data are presented as mean±SEM (n=6/
condition), analyzed by ANOVA with Bonferroni’s Student’s t-test.
RESULTS: Cells on TiAlV had lower cell number and higher
ALP and OCN than PEEK, but levels were higher on rTiAlV than
sTiAlV. Cells cultured on PEEK had a comparable osteogenic
phenotype as control cultures. MSCs cultured on rTiAlV had
greater OPG and BMP2 levels than cells on sTiAlV or PEEK, and
culture on TiAlV promoted greater BMP4 production than cells
on PEEK. Both active and latent TGFβ1 were higher on PEEK
than on sTiAlV and rTiAlV. VEGF production was higher on
TiAlV substrates than on PEEK. FGF2 and ANG1 production was
greatest on rTiAlV substrates in comparison to sTiAlV or PEEK.
DISCUSSION AND CONCLUSION: Rough titanium alloy surfaces
induce greater osteoblast differentiation of HMSCs than culture
on smooth titanium alloy or PEEK. Most importantly, HMSCs are
able to differentiate to osteoblasts on these rough surfaces without
addition of exogenous molecules or growth factors. Cells on
titanium alloy, but not on PEEK substrates, produce an osteogenic
and angiogenic microenvironment that may translate to more and
faster peri-implant bone formation, leading to earlier stability of
the bone-implant construct.
PAPER NO. 637
uPullout Strength of Calcium Triglyceride (CTG) versus
Polymethylmethacrylate (PMMA)
Lindsay Hickerson, MD, Richmond, VA
John R. Owen, PE, Richmond, VA
Jennifer S. Wayne, PhD, Chesterfield, VA
Hans R. Tuten, MD, Richmond, VA
INTRODUCTION: Calcium triglyceride (CTG) is a novel bone
cement with osseointegrative and adhesive properties that
undergoes a normothermic reaction and porosity expansion
upon mixing its components which are derived from naturally
occurring oils. Our hypothesis is that CTG’s unique property of
porosity expansion enhances initial interdigitation and increases
effective surface area of host bone-augmentation interface,
affording stronger fixation. This is a clinical advantage when
working with osteoporotic host bone and the increased risk of
loss of fixation. The purpose of this study is to use a pedicle screw
model to compare the pullout strength of CTG augmentation
versus the gold standard, polymethylmethacrylate (PMMA).
METHODS: The following methods are in accordance with
two separate American Society for Testing and Materials
(ASTM) standards1,2. Blocks of closed-cell polyurethane foam
of uniform density, 0.32 g/cm3 (ASTM grade 20), representing
subcortical bone in an osteoporotic pedicle were prepared3. The
components of PMMA (N=11) and CTG (N=11) were mixed
in a standardized fashion, 0.2ml was injected from deep to
superficial along a predrilled pilot hole followed by immediate
insertion of the pedicle screw. An unaugmented group (N=10)
was also prepared. Blocks were cured for 24 hrs, secured, and
screws pulled out a rate of 5mm/min. For the revision model,
the unaugmented group, after screw pullout, was augmented
with 0.8 ml PMMA (N=5) or CTG (N=5) as detailed above.
RESULTS: The mean pullout strengths (std dev) for the primary
models were: unaugmented 977N (94N), PMMA 1218N (67N),
and CTG 1842N (57N) (p<0.0001) and for the revision models:
PMMA 1939N (109N), CTG 2513N (149N) (p<0.0003).
DISCUSSION AND CONCLUSION: CTG augmentation of pedicle
screws resulted in significantly higher axial pullout strength in
primary and revision models compared to PMMA. References: 1)
ASTM F1839-08, “Standard specification for rigid polyurethane
foam for use as standard material for testing orthopaedic devices
and instruments,” ASTM international, West Conshohocken, PA
19428-2959. 2) ASTM F543-07, “Standard specification and test
methods for metallic medical bone screws,” ASTM international,
West Conshohocken, PA 19428-2959. 3) Hirano T, Hasegawa K,
Takahashi HE, et al. Structural characteristics of the pedicle and its
role in screw stability. Spine 1997;22:2504-9.
983
PAPER NO. 638
Is Congenital Cervical Stenosis Associated with
Congenital Lumbar Stenosis? A Study of 1,072 Human
Cadavers
Navrikat Bajwa, Cleveland, OH
INTRODUCTION: Congenital stenosis (CS) of the cervical and
lumbar spine occur when the bony anatomy of the spinal canal
is smaller than expected in the general population. This may
predispose an individual to symptomatic neural compression.
While tandem stenosis is known to occur in 25% of individuals
with symptomatic neural compression in one region, it is not
known whether this relationship is due to an increased risk of
degenerative disease in these individuals, or whether this finding
is due to the tandem presence of a congenitally small cervical and
lumbar canal. In our study we aim to find out if the presence of
CS in the cervical spine is associated with CS in the lumbar spine.
METHODS: A total of 1,072 adult skeletal specimens from the
Hamann Todd Collection in the Cleveland Museum of Natural
History were selected. Baseline data including age, sex, and race
of subjects were collected. Canal area at each level was calculated
using a formula that was verified by computerized measurements.
A standard distribution for each level was created, and values that
were -2SD below mean were considered as being congenitally
stenotic for each cervical and lumbar level. Linear regression
analysis was used to determine the association between the additive
canal area at all levels in the cervical spine and lumbar spine; and
to determine the association between the number of CS levels
in the cervical and lumbar spine. Logistic regression was used to
calculate odds ratios for CS in one area if CS was present in the other.
RESULTS: A positive association was found between the
additive area of all cervical and lumbar levels (p<0.01). A
positive association was also found between the number
of CS cervical and lumbar levels (p<0.01). Log regression
demonstrated a significant association between CS in the
cervical and lumbar spine with an odds ratio of 5.4 (p<0.05).
The prevelance of tandem stenosis was found out to be 2.05%.
DISCUSSION AND CONCLUSION: Based on our study of a large
population of adult skeletal specimens, it appears that CS of the
cervical spine is associated with CS of the lumbar spine. The
prevalence of tandem stenosis is lower than previously described in
studies but it appears to be, in part, related to the tandem presence
of a congenitally small cervical and lumbar canal.
PAPER NO. 639
The Feasibility of Translaminar Screws in the Subaxial
Cervical Spine: CT and Cadaveric Validation
Jason T. Le, BS, Norfolk, VA
Brian C. Werner, MD, Charlottesville, VA
Michael Iwanik, PhD, Charlottesville, VA
John A. Glaser, MD, Charleston, SC
INTRODUCTION: The use of translaminar screws may serve as a
viable salvage method for complicated cases. To our understanding,
the study of the feasibility of translaminar screw insertion in
the entire subaxial cervical spine has not been carried out yet.
METHODS: Eighteen cadaveric spines were harvested from C3 to
C7 and 1-mm CT scans and 3D reconstructions were created to
exclude any bony anomaly. Thirty anatomically intact segments
were collected (C3;2, C4;3, C5;3, C6;8,C7;14), and randomly
arranged. Twenty-one segments were physically separated at each
vertebral level (Group S), while nine segments were not separated
from the vertebral column and left in situ (Group N-S). Using the
trajectory proposed by the previous studies (Cho et al. 2010 CSRS,
2011 AAOS), and shown in Figure 1, translaminar screws were
placed at each level. CT measurements along the simulated trajectory
were used to determine the screw diameter to be utilized (Figure
2). If the diameter chosen for the 2° screw was not feasible due to
the 1° screw’s specific trajectory, only the 1° screw was inserted
which was always placed to maximize bony purchase. Twelve from
Group S and three from Group N-S were chosen to receive the
same diameter 1° and 2° screw. Nine from Group S and six from
Group N-S received screws that were 0.5mm larger in diameter. For
the vertebrae from group S, breakage of either the medial or lateral
cortex was visually confirmed. For each vertebra from group N-S,
breakage of the medial or lateral cortex was checked using CT scans.
RESULTS: The cortical breakage was shown in Figure 3
and Table 1. When 1° and 2° screws of the same size were
used, medial cortex breakage was found 13% and 33% of
the time, respectively. C7 was relatively safer than the other
levels. With larger sized screws, medial cortex breakage was
found in 47% and 46% of 1° and 2° screws, respectively.
There were no facet injuries due to the screws in group N-S.
DISCUSSION AND CONCLUSION: Translaminar screw insertion
in the subaxial cervical spine is feasible only when the lamina
is thick enough to avoid any breakage that could lead to further
complications. Otherwise, it is extremely dangerous; therefore,
the authors don’t recommend inserting translaminar screws in the
subaxial cervical spine except in some salvage cases in the presence
of a thick lamina. Preoperative CT scans are mandatory to measure
the thickness of the lamina.
PAPER NO. 640
Human Adipose-Derived Stromal Cells Treated with a
Novel Osteotropic Peptide for Spine Fusion
Haixiang Liang, MD, Charlottesville, VA
Gary Balian, PhD, Charlottesville, VA
INTRODUCTION: Bone autograft is currently the gold standard
for spine fusion; however, it is limited in availability and is
associated with high complication rates. Tissue engineering
offers the potential for the development of a practical bone graft
substitute, and requires the presence of both osteogenic cells
and osteoinductive factors. Human adipose-derived stromal
cells (hADSCs) are considered an excellent source of stem cells
for bone regeneration. Adipose tissue is a readily available and
984
viable source of multipotent hADSCs with minimal morbidity
associated with retrieval compared to autograft or bone marrow
stem cells, making it an ideal source for osteogenic cells. Peptides
offer distinct advantages over recombinant proteins such as
BMP-2, including speed of preparation, molecular stability, long
shelf lives and significantly decreased cost of manufacturing,
but have not previously been investigated. R1 peptide, a recently
developed novel osteotropic peptide, has shown promise
both in-vitro and in vivo. Our present study tests the osteogenic
differentiation of hADSCs induced by R1 osteotropic peptide.
METHODS: Cell culture: hADSCs were isolated from discarded
liposuction tissue. The cells were separated into five groups: 1.
Control, 2. OM (Osteogenic differentiation medium) 3. 1nM
R1 peptide (OM with 1ng/ml R1) 4. 5nM R1 (OM with 5ng/ml
R1) 5. 50nM R1 (OM with 50ng/ml R1). The cells were cultured
in monolayer for four weeks. Gene expression: hADSCs from
each group were harvested at one, two and four weeks. Total
RNA was isolated from the cells and expression of genes that
are associated with osteogenic differentiation were compared
among the groups by RT-PCR. Histology: Extracellular matrix
mineralization was detected by staining with Alizarin Red. This
was assessed both qualitatively and quantitatively. Statistics:
ANOVA was performed to determine whether there were
significant differences in gene expression or mineralization.
Data are presented as means ± S.D.. (*: P<0.05 vs. control, **:
P<0.05 vs. control & OM, ***: P<0.05 vs. control, OM, 1nM R1).
RESULTS: Gene expression: Gene expression for ALP, runX2,
osteocalcin and Collagen I increased in all of the groups that
were cultured with osteogenic medium. The 5nM and 50nM R1
groups demonstrated the highest gene expression (Figure 1).
Histology: All of the cultures treated with osteogenic medium
showed positive staining with Alizarin Red. The 5nM and 50nM
R1 groups showed stronger positive staining than the other
groups, which was confirmed by quantifying the stain (Figure 2).
DISCUSSION AND CONCLUSION: We have demonstrated
the osteogenic differentiation of hADSCs induced with a
novel osteotropic peptide. Gene expression studies indicate
that 5nM and 50nM concentrations of R1 peptide have a
significant effect on the osteogenic differentiation of hADSCs
compared to OM alone. Furthermore, the mineralization of
extracellular matrix confirmed the results of gene expression
and demonstrated that treatment of hADSCs with R1
osteotropic peptide elicits osteoprogenitor characteristics.
985
PAPER NO. 641
Effect of Metal Debris on Extracellular Matrix and
Cytokine Expression of Human Annulus Fibrosus
Chondrocytes
Edward R. Anderson, III, MD, San Antonio, TX
Michael Kurdziel, MS, Royal Oak, MI
Tristan Maerz, BS, Royal Oak, MI
Kevin Baker, MS, Royal Oak, MI
Jeffrey S Fischgrund, MD, Southfield, MI
Harry N. Herkowitz, MD, Royal Oak, MI
INTRODUCTION: Retrieval studies have illustrated significant
wear and corrosion of thoracolumbar instrumentation.
However, no studies to date have investigated the effect of
wear debris on the annulus fibrosus (AF). This study aims to
characterize the effect of metallic particulate on AF chondrocytes.
METHODS: Chondrocytes isolated from AF tissue collected during
primary lumbar interbody fusion procedures were exposed to
particles of titanium alloy (TiAl6V4), 316L stainless steel, and CoCr-Mo alloy at a 1000:1 dose (particles:cells) for seven days in vitro.
ECM gene expression was quantified by assaying Col1a1 and Col2a1
mRNA. Apoptosis was assayed by Caspase-3 mRNA, while culture
supernatant was characterized for pro-inflammatory cytokines and
matrix metalloproteinases(MMP) at days one, three, five and seven.
RESULTS: At day seven, results show 505% (639.9 pg/mL) and
379% (506.5 pg/mL) increase in IL-8 concentration due to
CoCrMo and 316L treatment, respectively, compared to baseline.
Concentration of granulocyte macrophage colony-stimulating
factor elevated 245% (2.0 pg/mL) and 384% (2.9 pg/mL) for
groups exposed to 316L steel and Co-Cr-Mo groups, respectively,
compared to control wells. Col1a1 was markedly downregulated
due to 316L and CoCroMo treatment at five and seven days; Col2a1
was downregulated due to CoCrMo at five days and due to CoCrMo
and 316L at seven days. Caspase-3 was not considerably affected.
DISCUSSION AND CONCLUSION: Metallic particles have a
negative effect on AF chondrocytes. Co-Cr-Mo and 316L steel
appear most inflammatory and decrease ECM expression to the
greatest extent while cells exhibited minimal response to TiAl6V4
particles. Wear debris has the potential to contribute to adjacent
level disc degeneration in the presence of metallic wear debris.
age at surgery, and intra-operatively for levels fused and anchor
density (Table 1). There was no difference in AVR (Table 2),
Cobb angle, correction rate and AVT between the two groups
at two-year follow up (Table 3). There was sufficient power on
post-hoc power analysis. Complications included one wound
infection in the CL group and one painful scar in the NCL group.
DISCUSSION AND CONCLUSION: We observed no differences
in maintenance of curve correction and vertebral rotation in
segmental pedicle screw constructs with or without cross linking
of the longitudinal rods in the surgical treatment of AIS.
Table 1 - Characteristics of CL vs NCL groups
Variable
CLmean
CLsd
NCLmean
NCLsd
p
age
13.8
2.2
14.1
2.4
0.64
Thoracic Cobb
58.6
11.2
56.2
11.5
0.38
Lumbar Cobb
37.8
14.1
36.5
11.5
0.67
Kyphosis
23.4
12.6
19.9
14.2
0.28
AVT
4.9
1.9
4.0
3.7
0.15
Levels fused
11.3
1.6
10.8
1.8
0.2
PAPER NO. 642
Anchors
19.9
3.0
18.9
3.1
0.2
uEffectiveness of Cross Linking Posterior Segmental
Instrumentation in Adolescent Idiopathic Scoliosis
(AIS)
Anchor density
1.76
0.1
1.76
0.1
0.91
Arjun Dhawale, MD, Wilmington, DE
Suken A. Shah, MD, Wilmington, DE
Petya Yorgova, MS, Wilmington, DE
Geraldine Neiss, PhD, Wilmington, DE
Douglas Layer, JR, Havertown, PA
Kenneth J. Rogers, PhD, Wilmington, DE
Peter G. Gabos, MD, Wilmington, DE
Larry Holmes, PhD, DrPH, Wilmington, DE
INTRODUCTION: A significant amount of practice variation exists
in the posterior treatment of adolescent idiopathic scoliosis (AIS).
Previous work has focused on the anchor or implant method,
but surgeons continue to debate the need for a cross link in
instrumentation constructs with segmental pedicle screws. There
are no clinical studies comparing the efficacy of cross links (CL)
versus no cross links (NCL) in maintenance of apical vertebral
rotation (AVR), apical vertebral translation (AVT) and curve
correction in AIS with screw constructs. Biomechanical studies
have been inconclusive. Detriments to the use of cross links include
added expense, late operative site pain and pseudarthrosis. This
study aims to compare the effectiveness of CL versus NCL in AIS.
METHODS: Seventy-five consecutive AIS patients <21yrs of age,
25 with cross links (CL) and 50 without cross links (NCL) treated
at single institution with two-year follow up are described. Preoperative and post-operative first erect, one and two year followup thoracic and lumbar Cobb angle, correction rate, AVT and
AVR were measured. AVR was assessed pre-operatively with Nash
Moe and postoperatively with Upasani et al grading. Groups were
compared with t test for pre-operative Cobb angle, age at surgery,
levels fused, anchor density and chi square test for sex, preoperative Risser, Lenke curve and AVR. Repeated measures analysis
of variance (ANOVA) and Chi square test were used for comparing
continuous and categorical data respectively. Analysis was
performed using SPSS and STATA, with significance set at p<0.05.
RESULTS: The average age at surgery was 14 years, the mean preop Cobb angle was 57°. The groups were similar pre-operatively
with respect to age, sex, Lenke curve, Cobb angle, AVT, Risser,
986
Table 2 -Comparison of apical vertebral rotation
CLn
CL%
Chi
p
FE po 0
AVR
6
24
12
NCLn
24
NCL%
0.04
0.97
FE po 1
13
52
27
54
“
“
FE po 2
6
24
11
22
“
“
1 yr po 0
5
21
11
22
0.5
0.78
1 yr po 1
15
60
26
52
“
“
1 yr po 2
5
20
13
26
“
“
2 yr po 0
5
20
10
20
0.01
0.99
2 yr po 1
13
52
26
52
“
“
2 yr po 2
7
28
14
28
“
“
Table 3 - Comparison of Cobb angle and AVT
variable
CLmean
CLsd
NCLmean
NCLsd
p
Thoracic Cobb pre-op
58.6
11.2
56.2
11.5
0.4
Thoracic Cobb first erect
16.1
6.2
15.6
5.8
“
Thoracic Cobb 1 year
17.7
5.2
19.6
6.9
“
Thoracic Cobb 2 years
20.5
6.3
20.4
7.2
“
AVT pre-op
4.9
1.9
4.0
3.7
0.09
AVT first erect
0.6
1.3
-0.1
1.5
“
AVT 1 year
1.1
1.4
0.7
1.4
“
AVT 2 years
1.4
1.1
0.9
1.5
“
PAPER NO. 644
Synergic Effect of Bone Morphogenetic Protein-2 and
-7 by Ex Vivo Gene Therapy in Rat Spinal Fusion Model
Takashi Kaito, MD, PhD, Osaka, Japan
Jared Johnson, MD, Los Angeles, CA
Jessica Ellerman, MD, Santa Monica, CA
Mehmet Aydogan, MD, Istanbul, Turkey
Mongkol Chatsrinopkun, Bangkok, Thailand
Stephanie Ngo, BS, Los Angeles, CA
Jeffrey C. Wang, MD, Santa Monica, CA
PAPER NO. 643
uHealing of Annulus Fibrosus Defect with
Mesenchymal Stem Cells and Platelet Rich Plasma: A
Natural 3D Scaffold
Joshua Schroeder, MD
Marianna Peroglio, PhD, Davos, Switzerland
Sibylle grad, Davos, Switzerland
Leon Kaplan, MD, Jerusalem, Israel
Amir Hasharoni, MD, Jerusalem, Israel
Yair Barzilay, MD, Jerusalem, Israel
Meir Liebergall, MD, Jerusalem, Israel
Mauro Alini, Davos Platz, Switzerland
INTRODUCTION: As annulus fibrosus (AF) degenerates, defects
lead to disc herniation. Increased extracellular matrix (ECM)
production and cell proliferation are needed to repair the AF
tissue. Platelet rich plasma (PRP) is a useful delivery system
containing growth factors. Mesenchymal stem cells (MSCs)
have been shown to differentiate to AF cells; therefore MSCs
are reasonable candidates for cellular therapy in AF defect.
METHODS: Blood aspirates were centrifuged producing PRP at
1/10 of the initial volume. AF cells were harvested from fresh discs.
MSCs were isolated from bone marrow of patients. AF cells alone
or co-cultures of MSCs and AF were incubated under the following
culture conditions: 25% PRP, 50% PRP, 10% FCS, or platelet
poor plasma. After 48 hours, DNA content, glycosaminoglycan
(GAG) levels and mRNA expression of collagen-I and II,
aggrecan, matrix-metalloproteinase-3 (MMP3) and MMP13 were
assessed. A defect was made in the AF of a bovine disc and PRP
or PRP with MSC was placed in the defect and grown for 14 days.
RESULTS: Medium containing PRP jelled, creating a 3D structure
in which the AF and MSCs harbored. A significant increase in the
DNA content and GAG production was seen in the PRP groups.
Gene expression of Col-I was up-regulated, Col-II was downregulated in the PRP groups, no change was seen in MMP3, MMP13
or aggrecan. In the whole disc, PRP caused an increase in GAG
production and induced cell activation. When MSCs were added,
new tissue formation was observed leading to defect closure.
DISCUSSION AND CONCLUSION: In-vitro AF cells proliferate and
produce increased ECM in the presence of PRP; MSCs when cocultured with AF cells increase GAG production and proliferation.
Ex-vivo PRP promoted GAG production in damaged intervertebral
discs, while the addition of MSCs showed an initial attempt toward
the healing of the defect. Taken together, these results indicate that
PRP might support AF regeneration in vivo.
987
INTRODUCTION: Although clinical bone morphogenetic
protein (BMP) therapy is effective, required doses are very
high. Previous studies have suggested that the co-expression
of two different BMP genes can result in the production of
heterodimeric BMPs that may be more potent than homodimers.
In this study, combined BMP-2 and BMP-7 ex vivo gene transfer
was performed to compare the new bone formation ability
with single BMP gene transfer in rat spinal fusion model.
METHODS: A total of 44 athymic rats aged 8-10 weeks were
operated with postelolateral fusion at L4-5 and implanted
collagen sponge containing 5 million human adipose derived
stem cells (HADSCs) treated five different ways. Group 1 (n=10):
untreated HADSCs. Group 2 (n=10): HADSCs transfected
with lenti-GFP. Group 3 (n=8): HADSCs transfected with lentiBMP-2. Group 4 (n=8): HADSCs transfected with lenti-BMP-7.
Group 5 (n=8): HADSCs transfected with both lenti-BMP-2
and lenti-BMP-7. The in vitro BMP-2 and BMP-7 production by
HADSCs was quantified by an enzyme-linked immunosorbent
assay (ELISA). Bony fusion at L4-5 was quantified using plain
radiographs obtained at four, six and eight-week time points. And
microcomputerized tomography (microCT) was used to quantify
a bone formation area at L4-5 axial plane and bone volume from
tip of L4 transverse process to base of L5 transverse process.
RESULTS: ELISA demonstrated that HADSCs transduced with
lenti-BMP-2 produced 3.4ng/ml of BMP2, HADSCs transduced
with lenti-BMP-7 produced 5.7ng/ml of BMP-7 and HADSCs
transduced with both lenti-BMP-2 and lenti-BMP-7 produced 0.7ng/
ml of BMP-2 and 0.9ng/ml of BMP-7, respectively. Briefly, Group 5
which treated by both lenti-BMP-2 and lenti-BMP2 produced less
than a quarter of BMP compared to the groups treated by single
lenti-BMP transfection (Group 3 and 4). In contrast, no detectable
BMP-2 or BMP-7 was produced by the HADSCs treated with no
lenti-virus and with lenti-GFP (Group 1 and 2). Radiograph analysis
showed all the spines of the Groups 3, 4, 5 rats (100%) appeared
fused on the plain radiograph by eight weeks. However, the spines
of the Groups 1and 2 showed minimal or no evidence of new bone
formation. Mean bone formation area at L4-5 level was 13.8mm2
in Group 1, 13.3mm 2 in Group 2, 34.0mm 2 in Group 3, 33.5mm 2 in
Group 4 and 77.0mm2 in Group 5. There was significant difference
between the Groups 1, 2 and the Groups 3, 4, 5 (p<0.01). Among
the Groups 3, 4, 5, the bone formation area was significantly
greater in Group 5 than the other groups (p<0.01)(Fig.1). Bone
volume was significantly greater in the Groups 3, 4, 5 compared
to the Groups 1, 2, however, there were no significant difference
among the Groups 3, 4, 5 (Group 1:181.6mm3, Group 2: 177.3mm3,
Group 3: 230.9 mm3, Group 4:223.0mm3, Group 5:228.0mm3 ).
DISCUSSION AND CONCLUSION: Although the HADSCs
treated by combined lenti-BMP-2 and lenti-BMP-7 (Group 5)
produced less than a quarter of BMPs than the HADSC treated
by single lenti-BMP, the Group 5 demonstrated significantly
greater bone formation area at L4-5 and equivalent fusion
rates and bone volume compared to the groups implanted with
HADSCs treated by single lenti-BMP gene transfer (Group 3
and 4). Combined BMP-2 and BMP-7 ex vivo gene transfer is
significantly more effective in inducing new bone formation than
individual BMP ex vivo gene transfer in rat spinal fusion model.
PAPER NO. 645
Intervertebral Disc Degeneration and Ectopic Bone
Formation in Apolipoprotein E Knockout Mice
Dawei Zhang, PhD, Charlottesville, VA
Li Jin, PhD, Charlottesville, VA
Davis Reames, MD, Charlottesville, VA
Xudong Li, MD, Charlottesville, VA
INTRODUCTION: Intervertebral disc degeneration is a multifactorial disease. Recently accumulating body of evidence
suggests an association between cardiovascular risk factors and
disc degeneration. Apolipoprotein E (ApoE) has been clearly
implicated in the development of atherosclerosis. The goal of the
present study is to elucidate the role of ApoE in disc degeneration.
METHODS: ApoE KO and wild-type (WT) mice were
characterized by histological/immunological, biochemical,
and real-time RT-PCR studies. Disc cells and bone marrow
cells (MSCs) were isolated to compare the extracellular
matrix
and
osteogenic
differentiation
capabilities.
RESULTS: ApoE was highly expressed in the endplates of WT discs,
and ectopic bone formed in the endplates of ApoE KO mice. The
bone MSCs of the KO mice showed significant higher osteogenic
differentiation than WT mice. Glycosaminoglycan content was
decreased in ApoE KO annulus fibrosus (AF) and nucleus pulposus
(NP) cells. Collagen levels were increased in AF and decreased in
NP cells. Matrix metalloproteinases-3, 9, and 13 expression was
increased which may at least partially explain the impaired matrix
production. The expression of collagen I, II, aggrecan and biglycan
increased in AF cells but decreased in NP cells. Apoptosis was
increased in the ApoE KO NP cells when compared to WT mice.
DISCUSSION AND CONCLUSION: ApoE, in addition to its
importance to cardiovascular disease, may play a critical role in disc
integrity and function and may represent a potential therapeutic
target. The relationship between cardiovascular disease and disc
degeneration warrants further investigation.
988
PAPER NO. 691
Vertebral Column Resection for Treatment of Adult
Spinal Deformities: Outcomes and Complications
Mostafa H. El Dafrawy, MD, Baltimore, MD
Firas Chamas, MD, PhD, Homewood, AL
Hamid Hassanzadeh, MD, Baltimore, MD
INTRODUCTION:
Correction
of
severe
rigid
spinal
deformities has been traditionally obtained via a combined
anterior/posterior approach. Single incision, all posterior
vertebral column resection (VCR) offers a potentially
superior alternative. There are few published reports with
the largest series describing VCR in the pediatric population.
METHODS: Retrospective review of 50 consecutive adult patients
(17 men and 33 women) with an average age of 50 years (2181) underwent posterior VCR by a single surgeon between
2004 and 2010. The deformities were divided into three main
groups: coronal (8), sagittal (31) and combined (coronal and
sagittal, 11). The average follow up was 22.6 months (3-76).
RESULTS: There were 27 lumbar and 26 thoracic VCRs (28
revisions & 22 primary). Forty-seven patients had a single level
and three patients had two nonadjacent levels VCRs. The average
number of levels fused was eight (2-16), average EBL of 3040cc
(550-9000) and average operative time 415 min (220-660). All
patients were ASA class 2 (28) and 3 (21). The average major Cobb
angle for coronal deformities (scoliosis and kyphoscoliosis) was
61° (20° to 105°) pre-op and corrected to 17.6° (1°to 39°). The
average preoperative thoracic kyphosis for thoracic deformity was
87.4° (38° to 137°) and corrected to 53.3° (34°to 72°). The average
lumbar lordosis for lumbar deformity was -27.2° (+30° to -65°)
and corrected to -40.3° (-11° to -87°). In the coronal group the
average focal correction in the patients with scoliosis was 34° (9°to
75°), while the average focal correction in the sagittal plane for
patients with kyphosis was 36° (6° to 76°). In the kyphoscoliosis
group the combined average correction for both planes was 62°.
The average preoperative sagittal imbalance was 83 mm (-61 to
351) pre-op and 30 mm (-48 to 187) at the last follow up. The
average preoperative coronal imbalance was 27 mm pre-op and
18 mm at the last follow up. The ODI, VAS and the SF 12 scores
were significantly improved at the last follow up (see table). There
were 13 major and 15 minor complications. Major complications
included six neurologic deficits manifested by distal lower
extremity weakness in a single nerve root, five in lumbar (four in
L5 VCR for treatment of high grade spondylolisthesis) and one in
a thoracic VCR. Four completely recovered and two had partial
recovery. There were two deep wound infections that resolved
with irrigation and drainage. Two patients suffered respiratory
failure requiring re-intubation. One patient developed pulmonary
embolism and one patient had pneumonia and one myocardial
infarction (NSTEMI). There were eight reoperations, two patients
required decompression for postoperative weakness, three had
extension of instrumentation for PJK while three patients had
their instrumentation removed. Minor complications: there was a
total of eight incidental durotomies (six in revision surgeries and
two in primary cases). There was one superficial wound infection
and two wound dehiscences treated with irrigation and drainage,
two patients had pleural effusion requiring chest tube insertion.
DISCUSSION AND CONCLUSION: All posterior VCR is a safe and
effective method in treating severe adult spinal deformities. Key
words: scoliosis, VCR, spine deformity, Kyphosis, Kyphoscoliosis
HRQL functional outcome
Pre-operative
PAPER NO. 693
Last follow up
P values
ODI
76.3 (48-92)
28.7 (21.9-36.4)
0.001
SF12
Physical health
32.1 (23.1-41.9)
54.9 (39.7-71.3)
0.012
SF12
Mental health
38.4 (28.2-47.7)
56.8 (41.3-74.8)
0.032
SRS
Self image
2.29 (1.2-3.7)
4.29 (3.2-5.0)
0.012
SRS
Activity
2.15 (1.1-2.6)
4.23 (2.8-5.0)
0.009
SRS
Pain
2.10 (1.4-2.9)
4.35 (3.0-5.0)
0.013
SRS
Mental
2.96 (2.0-3.7)
4.22 (2.6-5.0)
0.031
PAPER NO. 692
The Fate of the Adult Revision Spinal Deformity Patient:
A Single Institution Experience
Michael P. Kelly, MD, St Louis, MO
Linda A. Koester
INTRODUCTION: Reported revision rates for primary adult
spinal deformity (SD) surgeries have ranged from 9% to 25%,
but to our knowledge, the revision rate following revision SD
surgery has not been reported. The reported improvements
in health-related quality of life (HRQL) measures following
revision SD surgery have also been quite modest. The aim
of this study was to determine subsequent revision rates for
all revision SD surgeries performed at a single center and to
investigate the changes in measures of HRQL in these patients.
METHODS: A total of 504 consecutive adult revision SD
surgeries (1995-2008) were identified and the records were
reviewed to determine the reason for and timing to any
additional operation(s). SRS outcomes scores were recorded
at the first visit, and at planned follow-up (F/U) visits.
RESULTS: Ninety-six of 504 patients underwent further surgeries
for a subsequent revision rate of 19%. Two-year F/U was available
for 73 (77%) of these patients (mean F/U 6.0yrs, range 2.3-12.6,
gender: F=60, M=13, mean age 52.7yrs, range 21-78). The most
common causes of reoperation following revision surgery were
pseudarthrosis (N=28, 38%), adjacent segment disease (N=23,
32%), infection (N=13, 18%), and implant prominence/pain
(N=12, 16%). 15 (21%) patients underwent more than one
revision procedure. SRS outcomes scores were available for 50
(68%) patients, at an average F/U of 4.9yrs (range 2-11.4). The
mean improvements in the SRS outcomes measures were Pain: 0.74
(p<0.001), Self-Image: 0.8 (p<0.001), Function: 0.5 (p<0.001),
Satisfaction: 1.2 (p<0.001) and Mental Health: 0.3 (p=0.012).
DISCUSSION AND CONCLUSION: The rate of repeat revision
following revision spinal deformity surgery was 19%, most
commonly due to pseudarthrosis, adjacent segment disease,
infection and implant prominence/pain. However, significant
improvements in SRS outcome scores were still observed in those
patients requiring additional revision procedures.
989
Establishment of Parameters for Congenital Stenosis
of the Cervical Spine: A Study of 1,072 Cadaveric
Specimens
INTRODUCTION: ongenital cervical stenosis occurs when the
bony anatomy of the cervical canal is smaller than expected
in the general population. This may predispose an individual
to symptomatic neural compression. However, no studies have
defined congenital cervical stenosis (CCS) based on the normal
population. The diagnosis is currently made based on clinical
impression from radiographic studies which is subjective at best.
Exact measurements are needed which define this condition,
as are simple parameters that will accurately predict if CCS
is present. The purpose of this study is to provide a working
definition for congenital cervical stenosis, based on objective
measurements of cervical spine specimens, and to establish
parameters that will accurately predict if CCS is present.
METHODS: A total of 1,072 adult skeletal specimens from the
Hamann Todd Collection in the Cleveland Museum of Natural
History were selected. Baseline data including age, sex, and
race of subjects were collected. Digital calipers were used to
measure the following (C3-C7): sagittal canal diameter (sd),
interpedicular distance (ipd), and pedicle length (pl). Canal
area at each level was also calculated using a formula that was
verified by computerized measurements. A standard distribution
for each level was created, and values that were -2SD below mean
were considered as being congenitally stenotic. Once defined,
an analysis of deviance was performed to identify parameters
that were predictive of CCS. Logistic regression analysis was
used to determine odds ratios for CCS using these parameters.
RESULTS: CCS was defined at each level as: C3=1.82cm2;
C4=1.80cm2; C5=1.84cm2; C6=1.90cm2 ,C7=1.88 cm2. The sagittal
diameter (sd) and interpedicular distance (ipd) were found to be
predictive of CCS at each level with high sensitivity and specificity.
Predictive values were sd<13mm and ipd<22.5mm, which yielded
sensitivities and specificities of 88-100% at each level. Logistic
regression demonstrated a significant association between these
parameters and presence of CCS with OR>40 at each level.
Interestingly, pedicle length (pl) was not a good predictor of CCS.
CONCLUSIONS: Based on our study of a large population of adult
skeletal specimens, we have defined congenital cervical stenosis at
each level. Values of sd<13mm or ipd<22.5mm strongly predict the
presence of CCS at all levels C3- C7.
PAPER NO. 694
Nationwide Trends in the Surgical Management of
Lumbar Spinal Stenosis in all Age Groups
Hyun W. Bae, MD, Los Angeles, CA
Sean Rajaee, MS, Woodland Hills, CA
Linda E A Kanim, MA, Los Angeles, CA
INTRODUCTION: Over the last several decades, the number of
surgeries performed for patients with lumbar spinal stenosis (LSS)
has increased significantly. Several studies have reviewed indications
for surgical management of these patients and controversy still
exists as to what type of surgery should be performed. Select
group of patients are indicated for de-compressive surgery alone
and others are indicated for decompression with fusion with or
without instrumentation. Since lumbar spinal stenosis is most
prevalent in the older patient population who generally carry more
co-morbidities, benefits and risks must be carefully weighed in the
choice of surgical procedure. This current study aims to characterize
the epidemiology of surgical treatment for lumbar spinal stenosis
in the United States in all age groups from 2004 to 2008.
METHODS: Data were obtained from the Healthcare Cost
and Utilization Project Nationwide Inpatient Sample for
the years 2004-2008. Discharges were identified using
International Classification of Diseases, Ninth Revision,
Clinical Modification diagnostic and procedure codes for
patients with lumbar spinal stenosis. Population-based
utilization rates were calculated from United States census data.
RESULTS: Between 2004 and 2008, the annual number of
inpatient discharges with a primary diagnosis of lumbar spinal
stenosis increased from 91,630 to 101,936. The proportion of
patients (pts/xxx) between the age of 45 and 65 years with lumbar
spinal stenosis increased from 31.7% to 34.2% of all cases, while
all other age groups decreased in proportion. In 2004, 53.1% of
all patients with a primary inpatient diagnosis of LSS were treated
with surgical decompression alone without spinal fusion, while in
2008, this decreased to 43.7% of cases. Between 2004 and 2008,
the percentage of LSS discharges requiring a fusion increased
from 24.5% of all cases in 2004 to 34.2% in 2008. Out of all
LSS cases that required fusion in 2008, 32.8% involved the use
of bone morphogenetic protein, 43% used an interbody spinal
fusion device (cages/spacers), 0.5% used an interspinous process
spacer, and 11.7% of cases involved fusion of more than four
vertebral levels. Between 2004 and 2008, length of hospital stay
for patients receiving a fusion decreased from 4.60 days to 3.95
days, in hospital mortality decreased from 0.3% to 0.1% and
mean total hospital charges increased from $52,996 to $84,032.
DISCUSSION AND CONCLUSION: Among all inpatient discharges
for lumbar spinal stenosis, the proportion of cases requiring fusion
increased over the time period of 2004 to 2008. Mean hospital
charges for fusion cases increased by 56.8% from 2004 to 2008
while charges for decompression procedures increased by only
35.7%. The usage of bone morphogenetic protein and interbody
spinal fusion devices (spacers/cages) also increased over the time
period of this study. In addition to these findings, other patient
variables and hospital characteristics changed significantly
throughout the duration of this study.
990
PAPER NO. 695
Retrolisthesis and Lumbar Disc Herniation: A
Postoperative Assessment of Patient Function
Kevin Kang, MD, Brooklyn, NY
Michael Shen, MD, Broomfield, CO
Jonathan Lurie, MD, Lebanon, NH
Afshin Razi, MD, New York, NY
INTRODUCTION: Retrolisthesis in patients with L5-S1 disc
herniation has not been shown to have significant relationship with
worse baseline pain or function. Whether it can affect outcomes
following discectomy has yet to be established. The purpose of
this study was to determine the relation between retrolisthesis
(alone or in combination with other degenerative conditions) and
postoperative low back pain, physical function, and quality of life.
This study was intended to be a follow up to a previous investigation
that looked at preoperative assessment of patient function.
METHODS: This cross-sectional study was performed on patients
enrolled in the SPORT (Spine Patient Outcomes Research
Trial) study who underwent L5-S1 discectomy and who had
a complete MRI scan available for review (n=125). The SF36 bodily pain scale, SF-36 physical function scale, Oswestry
Disability Index (ODI), and Sciatica Bothersomeness Index
(SBI) were measured. Longitudinal regression models were
used to compare the time-weighted outcomes over four years.
RESULTS: Patients with retrolisthesis did significantly worse in
regard to bodily pain and physical function over four years. However,
there was no significant difference in terms of ODI or SBI. Similarly,
retrolisthesis was not a significant factor in operative time, blood
loss, length of stay, complications, rate of additional spine surgeries,
or recurrent disc herniations. Disc degeneration, modic changes,
and posterior degenerative changes did not affect outcomes.
DISCUSSION AND CONCLUSION: Although retrolisthesis in
patients with L5-S1 disc herniation did not affect baseline pain
or function, postoperative outcomes appeared to be somewhat
worse. It is possible that the contribution of pain or dysfunction
related to retrolisthesis became more evident after removal of the
disc herniation.
PAPER NO. 696
Scheuermann’s Kyphosis: Impact on Quality of Life in
86 Patients
Jamie S. Terran, BS, New York, NY
Randal R. Betz, MD, Philadelphia, PA
Paul D. Sponseller, MD, Baltimore, MD
Amer Samdani, MD
Harry L. Shufflebarger, MD, Miami, FL
INTRODUCTION: The clinical presentation and impact on healthrelated quality of life (HRQOL) of Scheuermann’s kyphosis (SK) has
not been previously evaluated in a prospective manner. Previous
studies have assessed the impact of adolescent idiopathic scoliosis
(AIS) and kyphosis in AIS patients on HRQOL. The purpose of this
study was to identify the clinical impact of Scheuermann’s kyphosis
on HRQOL compared to that for AIS and normal controls (NC).
METHODS: A total of 86 patients enrolled in a prospective study of
patients with operative Scheuermann’s kyphosis were evaluated.
Impact of kyphosis magnitude, apex location (thoracic, TL) were
evaluated with SRS-22 and VAS outcome instruments. These
patients were compared to a cohort of operative AIS patients from
a prospective database as well as to normal controls. ANOVA and
the Bonferroni post hoc comparison were utilized to compare the
groups. Pearson correlation was utilized for correlation comparisons.
RESULTS: Mean age for SK, AIS, and NC, were 14.96, 14.16 and
16.10 respectively (p<0.001). SK, AIS and NC were 39.5%, 75%
and 74.19 % female respectively (p< 0.001). Preoperatively, SK
patients have significantly lower scores in all domains of the
SRS-22 compared to AIS patients. SK and AIS patients scored
significantly lower than NC on the pain and image domains, as
well as mean scores (p<0.05). There was no significant difference
between SK and NC for the mental health domain. SK patients
with TL apex scored significantly lower than those with T apex
in the pain domain. There were no significant differences in SRS
scores between patients with kyphosis < 80° and > 80°. When
AIS and SK T5-12 K was pooled, there was a significant negative
correlation to all domains of the SRS. SK patients mean VAS
score was 3.36 ± 2.74. VAS score negatively correlates to pain,
image mental health and total SRS score. There is no correlation
of VAS to curve magnitude or apex location for AIS or SK.
DISCUSSION AND CONCLUSION: The clinical impact on
HRQOL of SK as compared to AIS and NC has been demonstrated
for the first time. Kyphosis appears to impart a significantly
negative impact on quality of life in the adolescent population.
991
PAPER NO. 697
Partial Facetectomy for Lumbar Foraminal Stenosis
Kevin Kang, MD, Brooklyn, NY
Juan Carlos C. Rodriguez-Olaverri, MD, PhD, New York,
NY
Jean-Pierre C. Farcy, MD, New York, NY
INTRODUCTION: Several techniques exist to address the pain
and disability caused by nerve root impingement. Failure to
adequately decompress the lumbar foramen has been cited as
a significant cause of failed back surgery syndrome. However,
aggressive treatment often causes spinal instability or may
require fusion for satisfactory results. The purpose of this study
was to describe a novel technique for decompression of the
lumbar nerve root and to demonstrate its effectiveness in relief of
radicular symptoms. This study was intended to be an evaluation
of outcomes following the removal of the medial portion of
the superior facet in patients with lumbar foraminal stenosis.
METHODS: Work status and activity level were measured in
patients who underwent partial facetectomy of the lumbar
spine (n=47). Average follow-up was 3.9 years. Those who
demonstrated neurogenic claudication without spinal instability
or central canal stenosis and failed conservative management
were eligible. Radiculopathy was defined as pain following a nerve
root distribution which was exacerbated by standing or walking.
On physical exam, patients exhibited muscle weakness without
atrophy as well as decreased reflexes. Conservative measures and
non-invasive rehabilitation exercises were used in all patients
for an average of 12 weeks. Patients with previous surgical
intervention, instability of the lumbar spine documented on
flexion/extension films, and central canal stenosis were excluded.
RESULTS: The average age of patients at time of surgery was 59
years (range 47-79). Twenty-seven of 47 (57%) report no back
pain and no functional limitations. They are able to participate
in recreational activities and work full time. Five of 47 (11%)
required additional surgery for continued degenerative symptoms.
DISCUSSION AND CONCLUSION: Partial facetectomy or removal
of the medial portion of the superior facet is an effective means to
decompress the lumbar nerve root foramen without causing spinal
instability.
PAPER NO. 698
Nurick Grade based Surgical Intervention in Cervical
Spondylotic Myelopathy Affects Improvement in
Symptoms
Han Jo Kim, MD, Saint Louis, MO
Arvind G. Von Keudell, MD, Chestnut Hill, MA
INTRODUCTION: Cervical spondylotic myelopathy is a relatively
common spinal disorder among elderly. If patients fail, conservative
management surgical treatment is indicated. Although several
surgical procedures are available the underlying difficulty of timing
and prediction of outcome remains poorly defined. We hypothesize
that clinical and functional improvement of myelopathic
symptoms is dependent on pre-operative severity of disease.
METHODS: We reviewed a consecutive series of all cervical
myelopathy patients who underwent surgical intervention by three
spine surgeons between 1/2000 and 10/2010 at our institution.
992
Patient’s medical records, operative reports and imaging studies
were studied. Patient demographics, persistence of myelopathic
symptoms, type of surgery and operative surgical levels were
collected. Patients were grouped according to their pre-operative
Nurick classification. The improvement of a pre-operative Nurick
Grade 0-2 was compared to the improvement of preoperative 3
and 4. This distinction was instituted because those with Grade 3
and 4 disease cannot be employed due to their cervical myelopathy.
RESULTS: A total of 258 patients (71 F; 188 M) were included
in this study. The average age was 59.22±13.27 and average
BMI was 28.3±5.1. Ten patients were lost during follow up time
(seven incomplete data; three deceased). Pre-operative duration
of myelopathic symptoms until surgical intervention was 14.93
months (1-101 months) and the average follow up was 15.3 (range
1-79 months). Of all patients, 213 patients underwent anterior
cervical decompression and fusion, three patients decompression
only and 42 patients (161 levels) underwent posterior cervical
decompression and fusion. In total, 110 patients had Nurick
grade 1, 90 grade 2, 48 grade 3 and 10 grade 4. Patients with
grade 2 (p=0.003) and grade 3 (p=0.005) were most likely to
have cure of all myelopathic symptoms. Largest improvement
of at least one Nurick grade was observed in pre-operative grade
2 (60%), grade 3 (50%), grade 1 (15%) and grade 4 (10%).
Parallel the greatest improvement with surgical intervention
to employment capable status based on pre-operative Nurick
Grade was observed in grade 2 (p<0.001) and grade 3 (p<0.001).
DISCUSSION AND CONCLUSION: Our data suggests that patients
with Grade 2 disease have the greatest likelihood of improvement
with surgery. Those with Grade 3 disease have an intermediate
prognosis for symptom resolution while those with Grade 4 disease
have a poorer prognosis even with surgical intervention.
RESULTS: Of the 14 cases reviewed, six were for the plaintiff. A
significant association was found between an adverse decision
and cases in which time to surgery was greater than 48 hours
(p<0.05, OR=2.1). There was no association with the functional
outcome, neurosurgical vs. orthopaedic consultation, initial
site of presentation, or initial diagnosis. Interestingly, it did
not appear that a rectal examination was performed in any of
the cases. Only four of the 14 cases (28.5%) involved an initial
presentation which included loss of bowel or bladder control.
DISCUSSION AND CONCLUSION: Based a study of court cases
involving CES, a positive association was found between time to
surgery greater than 48 hours and an adverse decision. The actual
degree of functional loss did not appear to affect the verdicts.
This study emphasizes the importance of early diagnosis of cauda
equina syndrome. As only 28.5% of the cases involved an initial
presentation which included loss of bowel or bladder control, it
also emphasizes the importance of cautioning all patients with
lumbar complaints of the risk of CES.
PAPER NO. 699
INTRODUCTION: APs are associated with spinal deformity.
It is thought that more APs are found with larger curves,
greater rotation, and more complex pathology. The
objective of this study is to study the incidence, subtypes,
and distribution of APs in spinal deformity patients.
METHODS: Low dose CT scans of 272 adolescent patients were
reviewed. Pedicles were classified as Type A: >4mm cancellous
channel, Type B: 2-4 mm channel, Type C: cortical channel, and
Type D: cortical or cancellous channel < 2mm channel. Group I
had 104 AIS patients, Group II had 69 patients with other spinal
deformities, and Group III had 99 patients with non-spinal
pathology. Curve and patient characteristics were analyzed.
RESULTS: A total of 8,661 pedicles were studied. In Group I, the
incidence of APs was 20.4%. In Group II, it was 19.7%. In Group
III, it was 9.8% (p<0.001). No significant difference was seen
between AIS and Non-AIS group (p=0.484). In the AIS group,
the incidence of thoracic APs was 29.8%, comprising 97.4% of
APs. Of those, 26.7% were type C or D. In the Non-AIS group,
the incidence of APs in the thoracic spine was 25.5%, comprising
92.8% of APs. Of those, 16.1% were type C or D. In the AIS group,
APs are 2.2X more likely to be located on the concave side of the
curve (p<0.001). In the Non-AIS group, APs are 2.4X more likely
to be located on the concave side of the curve (p<0.001). In the
AIS group, 31.9% of pedicles within severe curves (Cobb >70°)
are abnormal as compared to 21.8% in moderate curves (Cobb
40°-70°) (p<0.05). However, in the Non-AIS group, curve size
did not affect incidence of APs (p>0.05). Degree of kyphosis did
not impact pedicle morphology for both AIS and Non-AIS groups
(p>0.05). Female patients in both AIS and Non AIS groups had
significantly higher number of abnormal pedicles (p<0.0001).
DISCUSSION AND CONCLUSION: APs are more commonly
found in AIS and Non-AIS deformity patients than patients
A Review of Medicolegal Cases for Cauda Equina
Syndrome: What Factors Lead to an Adverse Outcome
for the Provider?
Eldra Daniels, Baltimore, MD
Zachary Gordon, MD, Lyndhurst, OH
Keisha French, Cleveland, OH
INTRODUCTION: Cauda equina syndrome (CES) is one of a
few true surgical emergencies involving the lumbar spine. While
treatment within a 48 hour period of time has been found to
correlate with improved outcomes, recovery of bowel and bladder
control unfortunately does not always occur and loss of this
function can be distressing to the patient. An understanding
of factors which affect the legal outcome can aid the clinician
in determining risk management for medicolegal cases of CES.
METHODS: The LexisNexis Academic legal search system was used
to identify 104 cases of CES. Cases involving social security disability
or claims against an employer were removed from the study. This
left 14 cases in which lawsuits were filed against treating physicians
for the management of CES. Outcomes data on trial verdicts were
collected, as were associated penalties. Case data was also compiled
on age, sex, initial site of presentation, initial diagnosis, whether
or not a rectal exam was performed, time to consultation with a
specialist, time to completion of advanced imaging study, time
to surgery, and neurosurgical versus orthopaedic consultation.
Univariate logistic regression analyses were performed to
determine the association between adverse decisions and case
data. Linear regression analyses were performed to determine
the association between the penalties and case data as well.
993
PAPER NO. 700
CT-Based Evaluation of 8,661 Pedicles: Curve
Characteristics Associated with Abnormal Morphology
Adam L. Wollowick, MD, New York, NY
Terry D. Amaral, MD, Bronx, NY
Beverly Thornhill, MD, Bronx, NY
Joshua D. Grossman, BA
Jonathan Horn, Bronx, NY
Etan Sugarman, MD, Bronx, NY
Preethi M. Kulkarni, Bronx, NY
Vishal Sarwahi, MD, Bronx, NY
without spinal deformity. There is no difference between AIS and
non-AIS in total APs. Significantly fewer Type C and D pedicles
(highly abnormal) were seen in the Non-AIS group. Abnormal
pedicles are common in patients with spinal deformity of all types.
Knowing the location of APs can aid in pre-operative planning and
help surgeons anticipate difficult screw placement.
PAPER NO. 701
Coronal Magnetic Resonance Imaging (MRI) Improves
the Diagnosis of Foraminal Stenosis
Trichy S. Rajagopal, Dr, Nottigham, United Kingdom
Robert W. Marshall, FRCS, Reading, United Kingdom
Neta Raz, MD, Berkshire, United Kingdom
Colin Archibald, Reading, United Kingdom
INTRODUCTION: Magnetic resonance imaging (MRI) has
become established as the investigation of choice in degenerative
disease of the lumbar spine. Conventional sagittal and axial
images demonstrate central and lateral recess stenosis well, but
do not detect foraminal stenosis with certainty. This is possibly
because scanning is not done in the plane of the exiting nerves.
Foraminal stenosis may thus be over-diagnosed. We found
that the diagnosis of foraminal stenosis can be improved by
additional coronal T 2- weighted and short T1 inversion recovery
(STIR) sequences. We studied the true incidence of foraminal
stenosis using coronal MRI in addition to conventional sequences.
METHODS: Two studies were done: Study 1 - a retrospective
analysis of conventional sagittal and axial MRI in 100 patients
with spinal stenosis treated by surgical decompression. We studied
the radiologists’ reports and noted their reported incidence of
foraminal stenosis and lateral recess stenosis. Study 2 - a prospective
analysis of lumbar spine MRI in 100 consecutive patients with
clinical features of spinal stenosis to assess the relative incidence
of foraminal stenosis and lateral recess stenosis. Three spinal
surgeons and a radiologist independently reviewed conventional
sagittal and axial T1 and T2-weighted sequences to identify signs
of nerve compression from L3 to S1 level. Each observer then
studied additional coronal scans to see if any nerve compression
could be identified. Any differences in diagnosis were recorded.
RESULTS: Study 1 - the analysis of these 100 MRI reports in the
study found that “foraminal stenosis” was reported by radiologists
in 46% using conventional sequences. The radiologists based
their diagnosis on sagittal and axial images only. Study 2 - the
prospective study of 100 patients suspected of having stenosis
included 48 men and 52 women. Their age ranged from 29 to 89
with a mean age of 67 years. MRI scans of 100 patients suspected
of having stenosis showed: spinal stenosis - 40; degenerative
spondylolisthesis - 14; posterolateral disc herniation - 14; normal
- 13; far lateral disc herniation - 7; isthmic spondylolisthesis - 6;
degenerative scoliosis - 6. Conventional sequences in patients
with spinal stenosis showed lateral recess stenosis reliably, but
also suggested foraminal stenosis in 43% (17 out of 40). However,
coronal sequences clearly showed no foraminal nerve compression
at all. In degenerative spondylolisthesis conventional scans
suggested foraminal stenosis in 10 of 14 cases. Coronal imaging
again showed no foraminal stenosis. In degenerative scoliosis
conventional scans suggested foraminal stenosis in all six cases.
Coronal imaging confirmed foraminal stenosis in five out of six
cases. In far lateral disc herniation (six out of seven) and isthmic
spondylolisthesis (six out of six), foraminal nerve compression
was confirmed by both conventional and coronal imaging.
DISCUSSION AND CONCLUSION: In cases of spinal stenosis
and degenerative spondylolisthesis, fine slice coronal MRI
sequences show that the exiting nerve roots are free, but
994
traversing nerve compression occurs in the lateral recesses
beneath the facet joints. Although axial and sagittal sequences
suggested foraminal stenosis, this impression seems mistaken
because the imaging is not in the plane of the nerve roots.
True foraminal stenosis with compression of the exiting nerves
does occur in conditions like isthmic spondylolisthesis, far lateral
disc herniation and degenerative scoliosis.The use of coronal
imaging tilted into the plane of the exiting nerve roots can improve
the accuracy of diagnosis of foraminal stenosis.
PAPER NO. 702
Are Thoracic Curves with a Low Apex (T11 or T11/12)
Really Thoracic Curves?
Milad Alam, San Diego, CA
INTRODUCTION: Curves with an apex at T11 and T11/T12
are classified by the SRS and Lenke classifications as thoracic
curves. In this study, we wished to determine whether this
classification is accurate or if curves with an apex at T11 or
T11/T12 represent a combination of both “thoracic” and
“thoracolumbar” curves or constitute their own class of curves.
METHODS: A review of data collected on 1,742 AIS cases from a
multi-center study was performed. Based on an analysis of the most
common curve apex levels (T9 for thoracic (TH) curves and L1 for
thoracolumbar/lumbar (TL/L) curves), two comparison groups
were created that represented “classic examples” of TH and TL/L
curves (Figure). Sixty-six cases with an apex at T11-T11/T12 were
identified and compared to 320 cases with an apex at T9 and 126
cases with an apex at L1. A distribution analysis of the curve lengths
and a Chi-square test comparing curve direction of the TH, TH/L,
and T11 - T11/T12 curves was performed (p<0.05). Additionally,
the three groups were compared with respect to the major Cobb
magnitude, trunk shift, and age at time of surgery. Finally, a
radiographic review of the T11-T11/T12 group was completed.
RESULTS: The curve direction of the three groups was significantly
different (TL/L: 84% Left, TH: 3% Left, and T11-T11/T12:16%
Left, p<.001). The mean number of vertebra in curves for the
T11-T11/T12 group (7.1 ± 1.2) fell in between the value for the
TL/L (5.7± 0.8) and TH (7.3 ± 1.0) groups. The T11-T11/T12
curve length distribution was a combination of a typical TH
curve and a typical TL/L curve. The T11-T11/T12 curves have a
greater trunk shift than both TL/L (p=0.002) and TH (p=0.011)
curves. There was not a significant difference between the three
groups in terms of major curve Cobb magnitude (p=0.09) or
age at time of surgery (p=0.76). The radiographic review of the
T11-T11/T12 curves revealed three curve patterns: 21 (32%)
long single curves, 28 (42%) short single curves, which are more
typical of a TL/L curves, and 17 (26%) double thoracic curves.
DISCUSSION AND CONCLUSION: We suggest caution in
lumping curves with an apex at either T11 or T11-12 disc together
with other thoracic apices in studies which involve principally
primary thoracic curves.
PAPER NO. 704
Should Shoulder Balance Determine Proximal Fusion
Levels in Patients with Lenke 5 Curves?
PAPER NO. 703
Restoring Thoracic Kyphosis During Posterior
Instrumentation for Adolescent Idiopathic Scoliosis
Shafagh Monazzam, MD, San Diego, CA
INTRODUCTION: Correcting hypokyphosis in adolescent
idiopathic scoliosis (AIS) patients is important in preventing
junctional kyphosis and increasing pulmonary function.
We wished to determine what factors were most predictive
of postop correction of hypokyphosis when segmental
posterior implants are used in treating thoracic AIS.
METHODS: Prospectively collected cases from a multi-center
study were analyzed. Lenke 1-4 AIS patients with preop kyphosis
of 5-20 degrees, treated with posterior pedicle screws, with a
surgeon who had at least 20 patients in the database were included.
Patients were divided into two groups postoperatively based on
first erect x-rays: those remaining hypokyphotic (HK, <20° or an
increase <5°) and those restored to normal kyphosis (NK, >20°
with >5° increase). Patients whose correction was less than 5
degrees were considered unchanged (hypokyphotic). Regression
analysis was done on four preop factors thought to influence the
postop kyphosis: pre-operative kyphosis, surgeon, rod material
utilized (steel vs. Ti) and use or not of a posterior release (Ponte).
RESULTS: Of the 280 patients included in the study, 227 reMEd
hypokyphotic and 53 achieved normal kyphosis. There were no
differences in preoperative kyphosis (13.4±5 HK group vs 14.5
±4 NK group) and age (14.7 HK group vs 14.6 NK group). Of the
factors evaluated, the surgeon was the most significant predictor
of restoration of normal kyphosis. Comparison of surgeons
showed the rate of normalizing kyphosis ranged from 6% to 42%
(p=.004) and there was no difference in the degree of preoperative
kyphosis between surgeons. Pre-operative kyphosis (p=.093),
rod material (p=.56), and use or not of a posterior release
(p=.622) were not significant predictors of restoration of normal
kyphosis. DISCUSSION AND CONCLUSION: Restoration of
thoracic kyphosis remains a challenge in posteriorly treated
thoracic AIS cases. “Surgeon” was the only significant predictor of
restoring normal kyphosis, emphasizing the importance of intraoperative techniques not presently measured in our study (e.g.,
extent of release, compression/distraction forces, rod contouring
techniques).
995
INTRODUCTION: A high left shoulder is an indication to
extend the fusion proximally in a right thoracic curve. Some
apply these same rules to high right shoulders in patients
with left thoracolumbar/lumbar curves. The purpose of
this study was to indentify the frequency of an opposite
high shoulder in Lenke 5 patients, and evaluate the factors
that influence shoulder balance both pre-op and post-op.
METHODS: A prospective multi-center AIS database was queried
for patients with Lenke 5 curves and a minimum of two-year follow
up. Pre-op and post-op shoulder height differences were recorded
and categorized by the opposite shoulder (right shoulder high in a
left thoracolumbar curve) as high (>1cm), level (within 1 cm), low
(>1cm). Pre-op and post-op radiographic variables were compared
based on the patients pre-op and post-op shoulder height.
RESULTS: Of the 104 patients identified, 37% patients had level
shoulders and 53% had a high opposite shoulder. The high and
low were further classified as slight (1-2 cm), moderate (2-3 cm),
significant (>3 cm) as per Kuklo et al. A high shoulder was associated
with a greater mean thoracic Cobb (31o) than those with a level or
low shoulder (24o and 26o, respectively; p=0.008). Post-op, 64%
of patients had level shoulders (<1 cm) and 93% had a shoulder
difference less than 2 cm. There were no significant factors predictive
for a high post-op shoulder including whether the thoracic curve
was included in the fusion (non-selective fusion). A slightly greater
proportion of the pre-op high shoulders (36%) had a non-selective
fusion than those with a level (27%) or low (9%) shoulder. Among
the 29 patients with a pre-op moderate or significant high shoulder
(>2 cm), only three continued to have a high shoulder greater than
2 cm which was not influenced by fusion of the thoracic spine.
DISCUSSION AND CONCLUSION: Half of all Lenke 5 curves
have a high opposite shoulder which is influenced by the size of
the compensatory thoracic curve. Post-op, the majority of patients
had level shoulders. Inclusion of the thoracic spine (non-selective
fusion) did not appear to influence post-op shoulder balance
even among those with a moderate or significant high opposite
shoulder.
PAPER NO. 705
urhBMP-2 and Modern Surgical Techniques Reduce
the Pseudarthrosis Rate in Adult Spinal Deformity
Samuel Kang-Wook Cho, MD, Palisades Park, NJ
Matthew M. Kang, MD
Joshua Pahys, MD, Wynnewood, PA
INTRODUCTION: Pseudarthrosis (PA) rates up to 30%
have been reported in adult spinal deformity fusion to the
sacrum. This study assessed outcomes of upper thoracic
(T2-T5) to sacrum spinal fusion (UT SF) with BMP and
modern surgical techniques in adult deformity surgery.
METHODS: We analyzed a single-center prospective cohort of 48
patients (47 F) with primary UT SF from 2002-2008 at mean f/u of
2.7 years (2-5.1 yrs). Study inclusion criteria were minimum mean
5 mg BMP/ level and mean 1.7 fixation points/level. The study
had a return rate of 84% (eight pts < 2-yr f/u, one pt died from
cancer). Fusion was done with autograft/local bone (no iliac crest
harvest), allograft and BMP. PA was diagnosed as implant failure.
Forty patients had additional oblique x-rays or CT scan for fusion
assessment. SRS scores, ODI and complications were recorded.
RESULTS: The cohort averaged 61.7 years (43.1-80.9 yrs) with
a BMI of 26.4 (18.7-46.1). SF averaged 15.2 posterior (mean 1.9
fixation points/level) and 1.5 anterior (71% of patients; 79% TLIF)
levels. BMP averaged 12.1 mg/posterior and 9.7 mg/anterior level.
Major coronal curve correction averaged 59%. Mean surgical time
was 493 minutes (330-660 min) with a mean EBL of 1.7 liters
(0.3-4.7 L). Mean hospital stay was 9.9 days (6-36 days). One
patient (2.1%) developed a pseudarthrosis. This patient had a
T2-sacrum PSF (5 mg BMP/posterior level) with L5-S1 TLIF (12
mg BMP) and presented with pain/broken rods at L3-L4 at 1.6
year f/u. Revision surgery confirmed L2-L5 PA treated with BMP/
allograft. Eight patients had intraoperative complications (six
minor, two major). Some 23% had a major acute perioperative
and 10% had a long-term complication. There were no local
or systemic complications due to BMP. Mean improvement in
SRS self-image (1.6), satisfaction (1.5), pain (0.8), subscore
(0.7), mental health (0.5) and ODI (-14.2) were significant.
DISCUSSION AND CONCLUSION: BMP, aggressive local bone
graft harvest and pedicle screw fixation may be a competitive
alternative to PSF with ICBG. This technique resulted in a 2.1%
pseudarthrosis rate in 48 adult deformity fusions. No complications
were directly attributable to BMP use. HRQOL scores significantly
improved and overall complication rate was consistent with
established norms. A surgical technique of aggressive local bone
graft harvesting combined with an average of 10 mg BMP/posterior
level and pedicle screw fixation resulted in only one pseudarthrosis
in upper thoracic to sacrum adult deformity fusions. This rate is
much lower than prior published rates for these difficult adult
deformity fusions. No local or systemic complications were
attributed to BMP use and Health Related Quality of Life scores
improved significantly for this patient cohort.
996
POSTERS
POSTER NO. P346
Staging Regimen in Adult Spinal Deformity Surgery
Impacts Functional Outcome, Complications & Total
Hospital Days
Joseph P. Gjolaj, MD, Miami, FL
Amit Jain, BS, Portland, OR
David A. Cohen, MD, Baltimore, MD
INTRODUCTION: The effect of the staging regimen on the
surgical outcome in patients undergoing combined anterior/
posterior surgery for treatment of spinal deformity has not
been studied. We hypothesize that in patients undergoing
combined posterior and anterior procedures, delaying the
second surgery (>21 days) is associated with less complications,
shorter hospital stay and better outcome compared to
performing both surgeries during the same hospitalization.
METHODS: Retrospective review of a prospectively collected
data in 63 consecutive patients (50 F, 13 M) >40 years
undergoing combined anterior and posterior fusions for
spinal deformities. We compared the clinical and radiographic
parameters, complications and functional outcome. All
patients completed a minimum two years follow up.
RESULTS: Twenty-nine patients underwent posterior and anterior
surgery during the same hospitalization (group I), average age 62
years (41-80). Thirty-four patients underwent their surgeries in
two separate hospitalization, staged (>21 days)(group II) average
age 60 ys (41-81). Group I and group II had similar preoperative
ASA status 2.7 (2-3) vs. 2.7 (2-4) and number of previous
surgeries 1.03 (0-2) vs. 1.08 (0-6). The average levels fused were
9(4-16) posterior & 1.6(1-3) anterior for group I and 9.5 (5-17)
and 1.03 (1-2) for the group II. The average time between the
two stages was seven days (0-15) for group I, and 38 days (2261) for group II. Average operative time; two stages combined
was similar in both groups; 624 min (430-820) for group I &
623 min (505-770) for group II. The average combined hospital
days was lower for group II, 12 days (6-44) compared to group
I, 14 days (7-70). The combined total estimated blood loss, 4L
(1.8-10.1L) was lower for the group II than the group I with 4.5L
(1.90-8.75L). Preoperative SRS-24 and ODI scores were similar in
the two groups, but significantly better in group II compared to
group I at six weeks and at final follow up, respectively (Table 1).
DISCUSSION AND CONCLUSION: When combined anterior and
posterior surgery is indicated, staging the two procedures in two
different hospitalizations (>21 days) decreased total hospital days
and complications with significantly improved outcome. Staging
combined anterior and porterior surgery in adult spinal deformity
should be considered whenever possible, as it may decrease cost,
lessen complications and improve outcome.
POSTER NO. P348
uOutcome of Operative Treatment for Spinal Deformity
in Patients with Syringomyelia Compared to AIS
Patients
Daniel J. Sucato, MD, Dallas, TX
Anna McClung, RN, Dallas, TX
Trey Allen, BS, Dallas, TX
Benjamin D. Martin, MD, Washington, DC
POSTER NO. P347
Metanalysis of Class I Results of Anterior Cervical
Decompression and Fusion with Allograft and Plating
Kenneth A. Pettine, MD, Loveland, CO
Lukas Eiserman, BS, San Diego, CA
INTRODUCTION: What are the clinical results of anterior
cervical discectomy and fusion (ACDF) with plating? Most spine
surgeons would answer a one-level ACDF has a 95% fusion rate
and 95% excellent clinical results. This perception is based on
class III or class IV data, retrospective reviews typically performed
by a spine fellow or resident on a senior author’s surgical series.
METHODS: Class I data from six FDA IDE studies involving
ACDF allograft with plating were reviewed. The studies include:
The Prestige (265 patients), ProDisc (103 patients), Bryan (221
patients), PCM (185 patients), Kineflex-C (133 patients), and
Secure-C (144 patients) artificial discs versus intervertebral
allograft with plating. Total number of patients included in this
metanalysis was 1,051. FDA clinical success was very similar
in all studies and defined as a 15 point or 20% improvement
in NDI, no reoperation, and no neurologic deterioration.
RESULTS: The average re-operation rate for a pseudoarthrosis,
adjacent level degeneration, or index level revision at two-year
follow up was 9.8% (table one illustrates individual study results).
Clinical success rates at two-year follow up averaged 68% (table
two illustrates individual study results).
Table One: Reoperation Rates at Two Year Follow Up
Prestige
19.9%
ProDisc-C
08.5%
Bryan
04.1%
PCM
06.6%
Kineflex-C
13.5%
Secure-C
06.25%
Table Two: Clinical Success at Two Year Follow Up
Prestige
72.6%
ProDisc-C
68.3%
Bryan
72.7%
PCM
60.9%
Kineflex-C
61.7%
Secure-C
71.7%
DISCUSSION AND CONCLUSION: Based on a metanalysis of
class I data, the results of ACDF with allograft and plating are a
9.8% reoperation rate at two-year follow up due to pseudoarthrosis,
adjacent level degeneration or revision of the index surgical site and
a 68% clinical success. These results emphasize the importance
in differentiating the validity of information gained from class I
versus class III and IV data.
997
INTRODUCTION: Spinal deformity associated with a
syringomyelia may be more challenging to treat than adolescent
idiopathic scoliosis (AIS) due to kyphosis, curve stiffness and
trying to determine fusion levels. The purpose of this study is to
quantify the differences between patients with syringomyeliaassociated scoliosis and AIS and to determine correct fusion levels
to achieve a balanced spine in the coronal and sagittal planes.
METHODS: An IRB-approved retrospective review of a
consecutive series of patients who had scoliosis associated
with syringomyelia (SS group) were compared to AIS patients
(AIS group) matched by curve type and magnitude (1:2 ratio).
Medical record and radiographs were reviewed preop, postop
and at two years. Radiographic outcome was characterized
as satisfactory at two years if the coronal balance ≤2 cm.
RESULTS: There was no difference between the SS (N= 38) and AIS
group (N= 82) for age (13.3 vs. 14.1 yrs), ethnicity and curve type,
however, there were more males (39.5% vs. 17.1%, p=0.01) in the
SS group. SS group had a higher incidence of being pre-menarchal
(57.9% vs. 28.4%, p=0.02) and a Risser sign of 2 or less (60.5%
vs. 39.5%, p=0.04). The coronal major curve preoperatively
was similar (62.6º vs. 64.5º), but curves were stiffer (flexibility
index: 39.7% vs. 54.2%, p=0.001) particularly in patients with a
neurosurgical decompression of the syrinx (37%, vs. 45.1% (no
decompression) and 54.4% (AIS), p=0.004), and thoracic curves
were more often to the left (51.5% vs. 2.8%, p<.0001) in the SS
group. Thoracic kyphosis was greater in the SS group preop (38.8º
vs. 21.2º, p<.0001), and at two years (31.7º vs. 23.9º, p=0.01).
Major coronal curve correction was similar postoperatively (56.1%
vs. 60.2%) and final follow up (47.4% vs. 53.5%), without a
difference in number of fusion levels (10.7 vs. 10.2). Preoperative
coronal (1.6cm vs. 1.7cm) and sagittal balance (2.3cm vs. 2.6cm)
and final follow up (1.3cm vs. 1.1cm) (3.0cm vs. 3.4cm) were
similar. Selection of the LIV was no different between the SS and
the AIS groups relative to the neutral (p=0.05), stable (p=0.08),
distal end vertebra (p=0.2) or the last vertebra touched by the center
sacral line (p=0.4). Intraoperative neuromonitoring had similar
rates for baseline SSEP (97.4% vs. 93.9%, p=0.6), however patients
with decompression of syrinx had decreased rates of obtaining
baseline MEP (64% vs. 100% (No decompression) and 94 % (AIS),
p=0.003). Rates of change in SSEP (5.3% vs. 0.0%, p=0.6) and MEP
(2.6% vs. 0.0%, p=0.3) monitoring were similar. There were no
neurologic deficits in this series. Overall rates of complications were
similar between both groups (7.9% (n=3) vs. 10% (n=4), p=1.0).
DISCUSSION AND CONCLUSION: Surgical treatment of scoliosis
associated with a syrinx has a high likelihood of achieving a
satisfactory result at two years postoperatively using similar fusion
levels and selection of an LIV that is similar to AIS patients. The
need to include more fusion levels for the syrinx group similar to a
neuromuscular construct was not seen in this series; despite syrinx
patients’ greater skeletal immaturity, having less flexible curves
and greater kyphosis.
POSTER NO. P349
The Ventral Lamina and Superior Facet Rule: The Key
to Accurate Placement for Thoracic Pedicle Screws
Daniel Kang, MD, Bethesda, MD
Rachel E. Gaume, BS
Haines Paik, MD, Fairfax, VA
Adam Bevevino, MD, Washington, DC
INTRODUCTION: With the increasing popularity of thoracic
pedicle screws, the freehand technique has been espoused to
be safe and effective. However, there is currently no objective,
definable landmark to assist with freehand insertion of pedicle
screws in the thoracic spine. With our own increasing surgical
experience, we have noted a reproducible and unique anatomic
structure known as the ventral lamina. We set out to define
the morphologic relationship of the ventral lamina (VL) to
the superior articular facet (SAF) and pedicle, and describe an
optimal pedicle screw starting point in the thoracic spine, which
we term the “Superior Facet Rule.” METHODS: A total of 115
thoracic spine vertebral levels (n=230 pedicles) were evaluated.
After the vertebral body was removed at the junction of the
pedicle, Kirschner wires were inserted retrograde along the four
boundaries of the pedicle (medial, lateral, caudad and cephalad).
Using digital calipers, we measured width of the SAF and pedicle
at the isthmus, and from the borders of the SAF to the boundaries
of the pedicle. We calculated the morphologic relationship of
the ventral lamina and center of the pedicle (COP), to the SAF.
RESULTS: A total of 229 pedicles were measured (one excluded due
to SAF fracture). The VL was clearly identifiable in all specimens
at all levels forming the roof of the spinal canal, and confluent
with the medial pedicle wall (MPW). The mean distance from
SAF midline to the MPW was 1.34±1.25 mm medial. The MPW
was lateral to SAF midline in 34 (14.85%) pedicles, with a mean
distance of only 0.52±0.51 mm lateral. The mean distance from SAF
midline to COP was 2.22±1.49 mm lateral. The COP was medial
to SAF midline in only nine (3.39%) pedicles. The mean distance
from the SAF superior border to the COP was 13.15±2.47 mm.
DISCUSSION AND CONCLUSION: The ventral lamina is a valid
and anatomically reproducible structure, consistently located
medial to the SAF midline (85%). We also found the COP
consistently lateral to the SAF midline (97%). Based on these
morphologic findings the optimal starting point for thoracic
pedicle screws, termed the “Superior Facet Rule,” should be 2-3 mm
lateral to the SAF midline, allowing screw placement in the center
of the pedicle and avoiding penetration into the spinal canal.
998
POSTER NO. P350
Radiation Dose Imparted by Cone-beam Computed
Tomography in Thoraco-Lumbar Spinal Surgery
Jeffrey K. Lange, MD, Worcester, MA
Andrew Karellas, PhD, Worcester, MA
John T. Street, MD, Vancouver, BC, Canada
Natalie M. Egge, MD, Worcester, MA
Jason C. Eck, DO, Worcester, MA
Anthony S. Lapinsky, MD, Holden, MA
Patrick J. Connolly, MD, Worcester, MA
Christian DiPaola, MD, Worcester, MA
INTRODUCTION: The use of surgical navigation coupled with
intraoperative cone-beam CT-guided technology in spinal
surgery is primarily utilized to enhance safe insertion of spinal
instrumentation. The consequent increased use of CT scans,
however, may pose long-term health risks to patients as a result
of radiation exposure. To our knowledge, a clinically targeted
assessment of radiation exposure for typical posterior spinal
procedures using intraoperative cone-beam CT technology does
not exist. The purpose of this study is to evaluate the radiation dose
to the patient imparted during typical posterior thoraco-lumbar
instrumented spinal procedures using intraoperative cone-beam CT.
METHODS: This is an observational study quantifying radiation
exposure to simulated patients in a simulated operating room.
Cone-beam CT scans were obtained using an O-arm in standard
mode. Thermoluminescence radiation dosimeters were placed
in a linear array on a foam-plastic thoraco-lumbar spine model
centered above the radiation source for O-arm presets of lumbar
scans for small or large patients. In-air dosimeter measurements
were converted to skin surface dose measurements using
published conversion factors. Dose-length product (DLP)
was calculated from these values, and effective dose (ED)
was estimated using published ED:DLP conversion factors.
RESULTS: Radiation dose from a single CT scan using the O-arm
“small patient” setting was 3.24 +/- 0.04 mSv (error range 2.374.12 mSv). Radiation dose from a single CT scan using the O-arm
“large patient” setting was 8.09 +/- 0.23 mSv (error range 5.9110.27 mSv). These doses tend to be lower than published typical
effective doses for abdominal CT scans (10-20 mSv). For the
“small patient” setting, two to three scans will impart an effective
radiation dose approaching the dose imparted by a typical
abdominal CT scan (Table 1). For the “large patient” setting,
one scan will impart an effective radiation dose approaching
the dose imparted by a typical abdominal CT scan (Table 1).
DISCUSSION AND CONCLUSION: Single thoraco-lumbar conebeam CT scans using an O-arm tend to deliver less radiation to
patients than standard body CT scans. However, the radiation
dose increases as patient size increases, and the radiation dose
received by larger patients for single scans may approach the dose
received during standard body CT scans. Quantitative information
regarding the radiation imparted to patients by cone-beam CT is
important for assessing the risks and benefits of this technology,
especially when spinal surgical procedures will require multiple
intraoperative scans.
Effective radiation dose (ED) imparted by multiple O-arm scans
expressed in milli-Sieverts (mSv).
Average ED in mSv,
Small Lumbar Preset
Average ED in mSv,
Large Lumbar Preset
1 scan
3.24 +/- 0.04 (2.37-4.12)
8.09 +/- 0.23 (5.91-10.27)
2 scans
6.48 +/- 0.08 (4.74-8.24)
16.18 +/- 0.46 (11.82-20.54)
3 scans
9.72 +/- 0.12 (7.11-12.36)
24.27 +/- 0.69 (17.73-30.81)
POSTER NO. P351
ALTERNATE PAPER: SPINE I
Comparison of Simple Posterior Decompression with
Laminoplasty for Patients with Cervical Compressive
Myelopathy
Mamoru Kawakami, MD, Wakayama, Japan
Shin-ichi Nakao, MD, Katsuragi-Cho, Japan
Daisuke Fukui, MD, Wakayama, Japan
INTRODUCTION: It has been reported that cervical
laminoplasty with structural reconstruction of the posterior
elements results in favorable outcomes for patients with
cervical compressive myelopathy. However, it is still unknown
if the reconstruction of the posterior elements itself is clinically
needed in a laminoplasty. We have developed a simple posterior
decompression surgery using mesh plate and cancellous screws
at the lateral mass through splitting spinous processes approach.
The purpose of this retrospective cohort study was to compare
the clinical outcomes in patients with cervical myelopathy
treated with two types of posterior decompression surgery.
METHODS: We compared 89 consecutive patients with
myelopathy undergoing posterior surgery into two groups: Group
I, 44 patients received a laminoplasty with use of laminar spacers
to secure expansive spinal canal and reattach the spinous process
and extensor musculatures and Group II, 45 patients had a simple
posterior decompression through splitting spinous processes
approach. We evaluated the clinical outcomes utilizing the
Japanese Orthopaedic Association Cervical Myelopathy Evaluation
Questionnaire (JOACMEQ) and radiological changes of the cervical
spine at two years postoperatively. Five subscales, which consisted
of cervical spine function, upper extremity function, lower
extremity function, bladder function and QOL, were measured
as a point calculated with the JOACMEQ. These evaluations
were based on a structured protocol established prior to patient
enrollment. The reviewers were blinded as to treatment group.
RESULTS: The demographics and preoperative subscales of
JOACMEQ were similar between the groups. Mean operation time
was no different, but mean blood loss in Group II (115 ml) was
significantly less than that in Group I (209 ml) (P<0.05). Three
patients were lost to follow up. Two patients in Group I, who had
revision surgeries due to postoperative neurological deterioration,
were excluded at the final examination. Postoperative changes of
upper extremity function, lower extremity function and bladder
function of JOACMEQ subscales were similar between the groups.
999
However, cervical spine function and QOL of JOACMEQ subscales
were improved in Group II more than those in Group I (Cervical
spine function: Group I, 12.9 points vs. Group II, 19.8 points,
QOL: Group I, 15.8 points vs. Group II, 24.1 points, P<0.05).
Improvement of axial pain (a recovery scale using Visual Analog
Scale, mm) in Group II was superior to that in Group I (Group
I: 11mm vs. Group II: 26mm, P age of 65 years), respectively.
DISCUSSION AND CONCLUSION: This simple posterior
decompression surgery resulted in a significant improvement
in axial pain, cervical spine function and QOL of patients with
cervical myelopathy compared to a laminoplasty. Postoperative
sagittal alignment of the cervical spine did not show any significant
change in both groups. Collectively, these results suggest that
structural reconstruction of the posterior elements is not needed
in cervical posterior decompression surgery.
POSTER NO. P352
uEvaluation of Spinal Fusion Capacity by a
Biodegradable Nanogel
Wellington K. Hsu, MD, Chicago, IL
Marco Mendoza, MD, Chicago, IL
Jacob Babu, MS, BS, Burr Ridge, IL
Mahesh Polavarapu, Chicago, IL
Stuart Kaltz, MS, Oak Park, IL
Samuel I. Stupp, PhD, Chicago, IL
Jeff McKee, PhD, Round Lake, IL
Shawn F. Bairstow, PhD, Round Lake, IL
Erin L. L. Hsu, PhD, Chicago, IL
INTRODUCTION: The use of recombinant BMP-2 (rhBMP-2) in
the cervical spine requires supra-physiologic doses, which has led
to complications such as localized swelling and edema, vertebral
body resorption, and airway difficulties. Although rhBMP-2
would benefit patients who are at high risk of nonunion, its
current use has been warned against by the FDA. Improvements
in carrier technology may allow surgeons to utilize rhBMP-2 in the
cervical spine safely by decreasing the exogenous dose necessary
to achieve successful fusion. This study investigates the capability
of a biodegradable nanofiber matrix containing a BMP-2-binding
epitope to elicit spine fusion. By sequestration of BMP-2 at the
fusion bed, such a technology could decrease or eliminate the
reported complications associated with the use of this growth factor.
METHODS: Posterolateral lumbar intertransverse spinal fusions
were performed on Sprague-Dawley rats assigned to groups treated
with one of two scaffolds: absorbable collagen sponge (ACS) or BMP2-binding nanogel (BMP-2PA). Each group was further divided
into sub-groups, where scaffolds were preloaded with 0, 0.1, or
1.0µg rhBMP-2. Ten µg rhBMP-2/ACS served as a positive control.
Fusion was assessed via AP radiographs and manual palpation.
Spines were scored by three blinded observers using a previouslyestablished scoring system: 0=no bridging bone; 1=unilateral
bridging; 2=bilateral bridging; 3=bilateral bridging with abundant
bone. Spines which scored an average of ≥1.0 were considered
successfully fused. The ability to sequester rhBMP-2 in vitro was
evaluated in both the ACS and the nanogel groups via ELISA.
RESULTS: When preloaded with 0, 0.1, or 1.0µg rhBMP-2, the BMP2PA elicited significantly higher fusion scores relative to ACS (Fig
1A). The BMP-2PA preloaded with 0, 0.1, and 1.0µg rhBMP-2 elicited
fusion rates of approximately 42%, 33%, and 100% respectively,
which were also significantly higher than that of ACS. Notably,
BMP-2PA preloaded with 1.0 ug rhBMP-2 had equivalent fusion
scores and rates to the positive control (10 ug rhBMP-2/ACS). An in
vitro BMP-2 release assay demonstrated a slower release pattern for
BMP-2PA compared to an early burst-type pattern for ACS (Fig 1B).
DISCUSSION AND CONCLUSION: Animals implanted with
the BMP-2PA nanogel demonstrated superior spine fusion rates
and scores relative to those treated with ACS, decreasing the
required rhBMP-2 dose by 10-fold. Furthermore, the nanogel
resulted in a spine fusion rate of 42% without any exogenous
rhBMP-2 compared to 0% for ACS. In vitro studies suggest that
the BMP2-binding epitope included in the nanogel sequesters
and releases rhBMP-2 in a more optimal fashion than ACS.
Consequently, this nanogel may maintain higher levels of
endogenous BMP-2 at the fusion bed site. Further studies will
evaluate the potential of this technology to lower the dose of
growth factor required for successful spine fusion in humans.
POSTER NO. P353
uRecombinant Human Bone Morphogenetic Protein-2
in Posterolateral Spine Fusion: What is the Correct
Dose?
INTRODUCTION: There are continued efforts to enhance the
process of achieving spine fusion and to eliminate the need for
autogenous iliac bone graft harvest. The use of osteobiologics to
enhance fusion has become an important role in these procedures.
Despite the fact of restricted approval, off-label use of BMPs has
become a permanent trend. About 85% of the procedures using
BMP were for off-label use. Especially rhBMP-2 in combination
with bone void fillers without or in combination with iliac
crest autograft for posterolateral intertransverse process fusion
has been studied and became more popular over time because
1000
of the need for a higher bonegraft amount for this procedure
especially in patients with poor bone quality. The adjunctive use
of rhBMP-2 has been found to result in larger and more consistent
fusion masses. The purpose of this study was to define the
amount of rhBMP-2 necessary to achieve reliable fusion rates in
posterolateral spine fusion by avoiding greater complication rates.
METHODS: During a seven-year period of time (2002-2009),
all patients undergoing lumbar posterolateral fusion utilizing of
rhBMP-2 were retrospectively evaluated within a large orthopaedic
surgery private practice. Patient demographics, comorbidities,
number of levels, type of surgery, and types of bone void filler
were analyzed. Complications related to rhBMP were defined
as reoperation secondary to symptomatic failed fusion, hyper
reaction resulting in compressive fluid collections, hyper
formation of bone resulting in neural compression, and infections.
RESULTS: A total of 559 consecutive patients were evaluated with
232 (41.5%) males and 327 (58.5%) females. Average age was 63
years and BMI was 31.3 kg/m². Number of levels fused was: 1 (169,
30.2%), 2 (244, 43.6%), 3 (92, 16.5%), 4 (35, 6.3%), 5 (8, 1.4%), 6
(5, 0.9%), 7 (2, 0.4%), and 8 (4, 0.7%). Sixty-three of 559 patients
(11.3%) had surgical complications. Seroma with acute neural
compression 18 (3.2%), excess bone formation with development
of neural compression requiring re-decompression 1 (0.2%),
infection requiring debridement 18 (3.2%), and symptomatic
nonunion requiring redo fusion and instrumentation 21 (3.8%).
Nonunion was not related to smoking, number of levels fused, or
steroid medication. There was an increased risk for nonunion in
female patients with increasing BMI (F=6.197, p=0.002). There was
no difference in nonunion risk for patients who received 6-11.9 mg
rhBMP-2/level (2.4%) compared to patients with ≥12 mg rhBMP-2/
level (2.3%). Patients undergoing fusion with 4-5.9 mg rhBMP-2/
level had a significant higher risk of nonunion compared to those
who received ≥ 6mg rhBMP-2/level (9.1% vs. 2.4%, p=0.012). No
significant differences were found for infection or seroma formation
in patients undergoing fusion with different levels of rhBMP-2.
DISCUSSION AND CONCLUSION: Different doses and
concentrations per level have been used in the past to achieve
the highest possible fusion rate. Studies in nonhuman primates
suggested 18 to 32 mg BMP-2 per side resulting in 36 to 64 mg BMP-2
per level to achieve solid fusion. In the following, multiple clinical
studies have been performed using 40 mg per level fused. Fusion
rates up to 100% were reported. There was also a growing concern
of complications and adverse effects. A systematic literature review
showed that the use of BMP in the lumbar spine can be associated
with graft resorption, extradiscal, ectopic, and heterotopic bone
formation, radiculopathies, epidural cyst formation, and seromas.
According to our findings, we recommend a dose of 6-12 mg
rhBMP-2 per level for successful instrumented lumbar fusion.
POSTER NO. P354
Image Changes of Multifidus Lumborum and Clinical
Correlations in Patients with Lumbar Stenosis
Yan-Yu Chen, MD, Taipei, Taiwan
Jwo-Luen Pao, MD, Taipei, Taiwan
Rong-Sen Yang, MD, Taipei, Taiwan
Karl Wu, MD, Taipei, Taiwan
Chih-Wei Chen, MD, Taipei City, Taiwan
Che-Nan Huang, MD, Taipei City, Taiwan
Yeong-Jang Chen, MD, Taipei, Taiwan
I-Ting Liao, MD, Taipei City, Taiwan
INTRODUCTION: Fatty infiltration (FI) of paraspinal muscles
has been correlated to chronic back pain in severity. The
clinical role of paraspinal muscle volume in patients with
spinal stenosis has yet been clarified. This study focused on the
clinical correlations of image changes of multifidus lumborum
to functional performance in patients with lumbar stenosis.
METHODS: Seventy patients diagnosed as lumbar stenosis at
L4-5 level without mechanical back pain or segmental instability
were included. Age, sex, body mass index (BMI), number of level
involved, and symptom duration were recorded and analyzed.
Cross-section MRI images of L4-5 intervertebral level were
evaluated. FI of multifidus lumborum was evaluated using T1weighted MRI images. Relative cross-sectional area (RCSA) of
multifidus lumborum was defined as the ratio of multifidus to
ipsilateral psoas muscle at L4-5 level. Functional performance was
evaluated with Japanese Orthopedic Association score (JOA score).
RESULTS: Age more than 60 was correlated with more FI (p<0.01)
while male gender was correlated with larger RCSA (p<0.01).
FI and RCSA were neither correlated with BMI, number of level
involved, nor symptom duration. More FI was correlated with
poorer JOA score in motor disturbance and urinary bladder
function (p<0.05). Smaller RCSA was correlated with poorer
JOA score in motor disturbance, turn-over when lying, taking
shower, leaning forward, and urinary bladder function (p<0.05).
DISCUSSION AND CONCLUSION: FI in multifidus lumborum
has been correlated with patients with chronic low back pain, but its
correlation with functional performance has not been established.
RCSA was first described in this study and was independent to
different BMI and image modalities. The result of this study may
provide useful information for explanation of different life quality
and treatment outcome in patients with lumbar stenosis.
min (270-660) EBL 2.75L (0.3-8.5) in group II. There were 10
major (17%) and 15 minor (26%) complications in group I, and
18 major (17%) and 37 minor (34%) in group II. The SRS-24 and
ODI for both groups are listed in the Table. All participants had
significant improvements in all SRS domains (Self Image, p<.001;
Pain, p<.001; Activity, p<.001; and Mental, p<.001). There was
significant reduction in disability as measured by ODI (p<.001).
Preoperative, there was no significant difference in the SRS
domain scores (Self Image, p=789; Pain, p=.481; Activity, p=.360;
Mental, p=.955) or ODI (p=.989) between the two groups. Postoperative, there was significant difference in mental health (p=
0.04). At final follow up, there was significant difference in selfimage (p= 0.02) with better outcome favoring revision patients.
DISCUSSION AND CONCLUSION: Revision surgery for
spinal deformity in adult patients, although technically
challenging and considered higher risk by most surgeons, has
comparable complications and favorable outcome compared
to primary surgery in the properly selected individuals.
Revision surgery for spinal deformity in adults should
not be contraindicated in the properly selected patients.
POSTER NO. P355
Clinical Results and Functional Outcome in Adult
Patients Following Spinal Deformity Surgery: Primary
vs. Revision
A. J. Khanna, MD, Baltimore, MD
Philip R. Neubauer, MD, White Hall, MD
Addisu Mesfin, MD, St Louis, MO
Richard L. Skolasky, Jr, Prof., Baltimore, MD
A Five-year Review of Response to Abnormal
Somatosensory Evoked Potential Monitoring in
Complex Spinal Surgery
Ivor Vanhegan, BSc(Hons), MBBS, MRCS, Dip SEM,
London, United Kingdom
Gemma Cannon, MSc, BS, Stanmore, United Kingdom
Syed Kabir, London, United Kingdom
Joseph Cowan, MB, ChB, Stanmore, United Kingdom
Adrian Casey, FRCS, London, United Kingdom
INTRODUCTION: Few reports examined the outcomes of
surgery in adults with spinal deformities; even fewer studies
evaluated the outcome of revision surgery. We hypothesize
that although the perioperative complications in revision
surgery may be higher than those of primary procedures,
the long term outcome in the two groups is comparable.
METHODS: We retrospectively reviewed 167 (128F, 39M)
consecutive patients ≥40 years, undergoing surgeries for spinal
deformity using a prospectively collected data. We compared
the clinical and radiographic parameters, complications and
outcome. All patients had minimum two years follow up.
RESULTS: Fifty-eight patients average age 60 years (40-87)
underwent primary surgery (group I) and 109 patients, age 59 (4080) underwent revision (group II). Group II had on average two
(1-14) prior surgeries. Number of levels fused in group I was seven
(4-18) & in group II six (3-17). Most commonly fused levels in
both groups were T11-S2, and most common upper instrumented
vertebra (UIV) was T11. Preop, postop and final f/u radiographic
data in the two groups are listed (Table). Average operative time
was 540 min (232-690,(EBL) 2.35L (0.4-8.5) in group I and 495
1001
POSTER NO. P356
INTRODUCTION: Evidence suggests that intra-operative
spinal cord monitoring is sensitive and specific for detecting
neurological injury. However, little is known about surgeons’
responses to trace changes and the resultant neurological
outcome. The objective is to examine the role of intra-operative
somatosensory evoked potential (SSEP) monitoring in the
prevention of neurological injury, specifically sensitivity and
sensitivity, and whether the abnormalities were reversible.
METHODS: A total of 2,953 consecutive complex spine operations
(male 36% female 64%, median age 25yrs) prospectively performed
using spinal cord monitoring (SCM) at a single institution (20052009). All traces and neurophysiological events were prospectively
recorded by the neurophysiology technician. All patients with a
significant neurophysiology event were examined clinically by
a neurologist, separate from the spinal surgery team. Significant
trace abnormality was defined as a decrease in signal amplitude
of 50% or a 10% increase in latency. Timing of trace abnormality,
surgeon’s response and prospective neurological outcome were
recorded. Sensitivity, specificity, positive / negative predictive
value were calculated. A Chi-squared test was performed to assess
the impact of intervention on neurological outcome (p < 0.05).
RESULTS: A total of 2,953 operations involving SCM were
performed and 106 recorded a significant trace abnormality.
This most often occurred during instrumentation and the most
common reaction was adjustment of metalwork. SSEP monitoring
had a sensitivity of 100%, specificity 97.3%, PPV 24%, NPV
100%. There were 79 false positives and no false negatives in
this series. Chi-squared test was not significant (p=0.18) possibly
suggesting intervention did not affect neurological outcome.
DISCUSSION AND CONCLUSION: Triggering events are
uncommon and the development of a persistent neurological
deficit is rare with an incidence of 0.85% in this series of 2,953
operations. In the majority of cases detection of a monitoring
abnormality prompts a corrective reaction by the surgeon. Of
those with an abnormal trace, 76% were neurologically normal
at follow up.
patients with and without FAC was as follows: MMP-1 was 611.0
(±191.8) vs. 84.2 (±52.3); MCP-1 was 68.7 (±22.3) vs. 12.7 (±4.1);
MIP-1b was 5.32 (±1.33) vs. 0.053 (±0.053); and RANTES was 310.2
(±72.5) vs. 6.55 (±2.11). Figures 1 and 2 illustrate the differences for
MIP-1beta. Both graphs are included due to the presence of outliers.
DISCUSSION AND CONCLUSION: Fragments of structural
matrix proteins, such as FAC, are significantly associated with
proinflammatory cytokines and matrix metalloproteinases in
cervical disc disease w/ radiculopathy. Complex interactions among
inflammatory markers, proteases, and structural matrix proteins
have been observed in the symptomatic lumbar disc disease and
in painful intraarticular pathology of the knee. Further evaluation
of FAC and associated biomarkers in painful disc disease in the
cervical spine appears warranted.
POSTER NO. P357
Correlation of Cervical Disc Disease with FibronectinAggrecan Complex, Cytokines and Matrix
Metalloproteinases
S. R. Golish, MD, PHD, Ridgefield, WA
Matthew Smuck, MD, Redwood City, CA
Ma Agnes Ith, Redwood City, CA
Lewis Hanna, PhD, Jupiter, FL
INTRODUCTION: Several classes of molecular biomarkers
have been implicated in intervertebral disc disease, including
inflammatory
mediators,
proteases,
structural
matrix
proteins and their fragments. We investigated the presence of
proinflammatory cytokines, matrix metalloproteinases, and
a structural breakdown product termed fibronectin-aggrecan
complex (FAC) in patients undergoing discectomy at a single level
for cervical radiculopathy due to herniated disc and/or stenosis.
METHODS: This study was a single center, prospective, consecutive
case series of patients undergoing treatment for radiculopathy due
to cervical disc herniation or stenosis. Inclusion criteria included
patients with radiculopathic pain, numbness or weakness with
MRI positive for disc herniation and/or stenosis correlating with
their symptoms at a single level. Each patient elected for anterior
cervical discectomy and fusion with instrumentation, and gave
informed consent for study participation. Lavage was performed
by excision of diseased disc after fluoroscopic localization of
the correct level. The lavage fluid was assayed for FAC, MMP-1,
MMP-3, MMP-9, IL-1beta, IL-1ra, IL-6, eotaxin, IFN-gamma, IP10, MCP-1, MIP-1beta, PDGF-BB, RANTES, TNF-alpha, VEGF.
RESULTS: There were 23 patients including eight females and 15
males with mean (±standard error of mean) age of 56.5 (±2.8) and
with symptoms for 32.2 (±4.6) weeks. Weakness was present in six
patients (26.1%) with sensory symptoms only in the remainder.
Herniated nucleus pulposus predominated in 13 patients (56.5%)
with stenosis predominating in 10 patients (43.5%). The surgical
level was C5-6 for 11 patients (47.8%), C6-7 for eight patients
(34.8%), and other levels for four patients (17.4%). Symptoms
were left sided in 12 patients (52.2%), right sided in seven patients,
and bilateral in four patients (17.4%). FAC was detectable in 16
of 23 patients (69.6%). Between patients with and without FAC,
there were significant differences in MMP-1 (p=0.002), MCP1 (p=0.003), MIP-1beta (p=0.001), and RANTES (p<0.001) by
Mann-Whitney U test after Bonferroni multitest correction. The
mean (±standard error of mean) in picograms/milliliter between
1002
POSTER NO. P358
Surgical Treatment of Cervical Spondylotic Amyotrophy
Predicting Factor Related with Poor Outcome
Ryoji Tauchi, MD, Nagoya, Japan
Shiro Imagama, MD, Nagoya, Japan
Zenya Ito, Nagoya, Japan
Kei Ando, MD, Nagoya, Japan
Kenichi Hirano, MD, Nagoya, Japan
Akio Muramoto, Nagoya, Aichi, Japan
Hiroki Matsui, Nagoya, Japan
Naoki Ishiguro, MD, Nagoya, Japan
INTRODUCTION: Cervical spondylosis causes upper extremity
muscle atrophy without sensory disturbance, which is called
as cervical spondylotic amyotrophy (CSA). Since Keegan first
reported autopsy case of this patient, there have been various
reports regarding treatment strategies, diagnostic methods,
conservative treatments, and surgical results for CSA, as well as
the conditions of CSA. However, several questions associated with
CSA still remain. In this study, we evaluate the predicting factors
related with poor outcome after surgical treatment in CSA patients.
METHODS: Of 27,807 registered patients who underwent spinal
surgery between 1995 and December 2009, 57 underwent
surgery for CSA, of whom 40 could be followed up for one year
or longer, and they were evaluated. The subjects were 37 men
and three women, with an average age of 59 years (39 to 78). The
mean follow-up period was three years (1 year to 12 years and 9
months). To evaluate the surgical treatment effect, MMT (manual
muscle test) was used, and improvements in the muscle strength of
the most atrophic impaired muscle were classified in four grades.
These were: “excellent,” full recovery; “good,” 1 grade of recovery
by MMT; “fair,” no improvement by MMT; “poor,” worsening by
MMT before surgery and at the time of the last follow up. The
evaluation items included the duration of CSA, time needed for
an improvement of at least 1 MMT grade postoperatively, whether
the subjects had proximal- or distal-type CSA, ranges of spinal
cord compression shown on cervical MRI, and surgical methods.
RESULTS: The duration of CSA was 6.8 months on average, 28
patients had proximal-type CSA, and 12 patients had distal-type
CSA. The surgical results were: excellent for 22 patients, good
for eight, fair for nine, and poor for one. Intramedullary signal
intensity changes were confirmed in 13 of 38 subjects, and spinal
cord compressions were found at an average of 2.8 intervertebral
levels. In terms of the surgical method, laminoplasty with or
without foraminotomy was performed for 31 patients, posterior
fusion for four patients, and anterior spinal fusion for five patients.
The time needed for a postoperative improvement of at least 1MMT
grade was approximately five months. In comparison between
patients rated as excellent or good and those rated as fair, the
patients who had fair or poor outcome after surgery revealed that
the duration of CSA was longer (284 vs. 176 days, respectively),
preoperative MMT grades showed a tendency to be lower (grade:
1.8 vs. 2.5, respectively), and the proportion of distal-type
CSA was higher in the poor outcome group. In addition, seven
patients of poor outcome group underwent laminoplasty without
foraminotomy, and the remaining two underwent posterior fusion.
DISCUSSION AND CONCLUSION: From these results, it
was demonstrated that the duration of CSA was longer, and
preoperative MMT grades showed a tendency to be lower in the
patients with poor surgical outcome than in those with good
outcome. Based on these results, early surgery is recommended
for patients in whom a diagnosis of CSA has been made and
conservative treatments have not been successful. On the subject
about surgical methods, laminoplasty without foraminotomy was
performed at a higher probability in those with poor results, and,
hence, if the CSA patients present ventral nerve root impingement,
appropriate foraminotomy should be performed in consideration
of the decompression site based on imaging findings.
POSTER NO. P359
Hypertrophy of Ligamentum Flavum in Lumbar Spinal
Stenosis is Associated with Increased bFGF Expression
Sittisak Honsawek, MD, PhD, Bangkok, Thailand
Chookiet Chalermpanpipat, MD, Bangkok, Thailand
Wicharn Yingsakmongkol, MD, Bangkok, Thailand
INTRODUCTION: Lumbar spinal canal stenosis is the most
common spinal disorder in elderly patients, causing low back and leg
1003
pain, radiculopathy, and cauda equina syndrome. Canal narrowing
partly results from hyperthrophy of ligamentum flavum (LF), which
mechanically compresses nerve roots. Basic fibroblast growth factor
(bFGF) is a potent regulator of many cellular functions including
proliferation, differentiation, wound healing, and angiogenesis.
METHODS: The purpose of this study was to investigate the pattern
of bFGF expression in the ligamentum flavum (LF) of patients
with lumbar spinal stenosis. We quantified and localized bFGF
expression in LF tissues obtained during surgery from 19 patients
with lumbar spinal stenosis. bFGF expression was determined
with in situ using immunohistochemistry, reverse transcriptasepolymerase chain reaction (RT-PCR), and quantitative real-time
PCR. The values of bFGF in the surgically obtained LF specimens
were analyzed by enzyme-linked immunosorbent assay.
RESULTS: The bFGF expression was significantly higher in
hypertrophic LF of spinal stenosis than that in nonpathologic LF
of controls. bFGF was detected in the cytoplasm of LF fibroblasts.
The mean concentration of bFGF in the hypertrophic LF was
remarkably greater in the pathologic LF of spinal stenosis when
compared to the nonpathologic LF of controls (P=0.003). In RTPCR, the mean optical density of bFGF was substantially higher
in the hypertrophic LF than controls (P=0.006). There was greater
bFGF expression in lumbar spinal stenosis patients as quantified
by real-time PCR (P=0.001). Moreover, there was a positive
correlation between the tissue bFGF expression of the pathologic
LF and patient age in spinal stenosis patients (r = 0.63, P < 0.001).
DISCUSSION AND CONCLUSION: This data demonstrated that
increased bFGF expression was associated with the degenerative
changes of hypertrophic LF, suggesting that bFGF could play a
potential role in pathogenesis of hypertrophic ligamentum flavum
in lumbar spinal stenosis patients.
POSTER NO. P360
Diagnostic Classification for Lumbar Spine Registry
Development
Leah Y. Carreon, MD, Louisville, KY
Paul A. Anderson, MD, Madison, WI
Daniel Resnick, MD, MS, Madison, WI
INTRODUCTION: Low back pain (LBP) is a symptom not a
diagnosis. The failure to differentiate underlying diagnoses in
patients complaining of LBP is one of the primary reasons that
studies examining treatments for LBP have yielded inconsistent
results. In order to design a lumbar spine registry such that the
accumulated data provides applicable guidance for clinical
treatment, the incorporation of a functional diagnostic matrix
is critical. One of the primary difficulties in evaluating the
effectiveness of lumbar fusion is that, outside of spondylolisthesis,
specific diagnostic indications for surgery are poorly defined.
This lack of diagnostic specificity markedly limits the ability
to accurately determine either relative benefit of surgery versus
medical management or the optimal surgical procedure for a
given clinical scenario. The purpose of this study is to propose
a clinically relevant diagnostic classification scheme, simple
enough for use in clinical practice but granular enough to
differentiate characteristics which impact clinical outcome.
METHODS: Thirty case histories were compiled. Each case
consisted of a brief clinical history with PE findings as well as
pertinent radiographic images, including CT scan and MRI
when available. Thirty-six physicians were asked to provide a
three-digit diagnostic code, specifying Symptoms, Structural
Pathology and Compressive Pathology for each case (Figure
1). The cases were then randomly re-arranged and sent back to
the physicians two weeks later for a second review. Multi-rater
Kappa values for inter and intra-rater reliability was determined.
RESULTS: The inter-rater agreement was substantial for
Symptoms (κ=0.70) and moderate for Structural Pathology
(κ=0.58) and Compressive Pathology (κ=0.53). The intra-rater
agreement was substantial for Symptoms (κ=0.78), Structural
Pathology (κ=0.70) or Compressive Pathology (κ=0.67).
DISCUSSION AND CONCLUSION: This study demonstrates that
improved diagnostic stratification of lumbar spine disorders is a
feasible goal. The diagnostic coding matrix, based on clinically
relevant descriptors, yielded substantial inter-rater consistency
for symptoms, moderate inter-rater consistency for structural and
compressive pathology, and substantial intra-rater consistency for
all elements.
Digit 1
Symptoms
Description
1
Back Pain
Dominant - Acute
Primary complaint is Low Back Pain. Symptoms ≤ 3
months duration.
2
Leg Pain Dominant
- Acute
Primary complaint is Leg Pain. Symptoms ≤ 3
months duration.
3
Back Pain = Leg
Pain - Acute
Patient reports 50% ± 10% Low Back Pain and 50%
± 10% Leg Pain. Symptoms ≤ 3 months duration.
4
Back Pain
Dominant Chronic
Primary complaint is Low Back Pain. Symptoms > 3
months duration.
May include multiple recurrent episodes of back pain
(acute on chronic).
5
Leg Pain Dominant
- Chronic
Primary complaint is Leg Pain. Symptoms > 3
months duration.
May include multiple recurrent episodes of leg pain
(acute on chronic).
6
Back Pain = Leg
Pain - Chronic
Patient reports 50% ± 10% Low Back Pain and 50%
± 10% Leg Pain. Symptoms > 3 months duration.
May include multiple recurrent episodes of back and
leg pain (acute on chronic).
7
Neurogenic
Claudication
Numbness, weakness or pain to the buttocks or
legs, exacerbated by walking or standing, relieved
by sitting.
8
Cauda Equina
Syndrome
Dominant complaint is motor weakness,
incontinence or Cauda Equina Syndrome, with or
without associated complaints of pain.
Digit 2
Structural
Pathology
No study ordered.
Or, no study interpretation available for
determination of structural pathology
0
1
Age Appropriate
Structural changes are consistent with normal aging
and not a clinically relevant source of symptoms
2
Disc Pathology
with normal disc
height
Disc pathology without significant loss of disc
height; includes disc herniation, internal disc
desiccation and annular tear
3
Disc Space
Collapse
Disc pathology with mechanical disc space collapse
with or without associated disc space pathology
4
Spondylolisthesis/
Spondylolysis
Any listhesis, including degenerative and isthmic
spondylolisthesis
5
Scoliosis/
Kyphosis
Lumbar spinal deformity including localized scoliosis
or kyphosis
6
Facet Pathology
Significant facet arthrosis or degeneration, including
synovial cysts
7
Non-union
Failure of prior surgical fusion
Digit 3
1004
Description
Compressive
Pathology
0
Not defined
No study or ordered.
Or, no interpretation available for determination of
compressive pathology
1
None
No clinically relevant compressive pathology
2
Central
Compression
Compression in the central canal region (between
the lateral margins of the dura) from any etiology.
3
Lateral
Compression
Compression in the lateral recess or foraminal
regions (lateral to the lateral margins of the dura)
from any etiology.
4
Combined Central
and Lateral
Compression
Compression in the central canal and lateral recess/
foraminal regions from any etiology.
5
Recurrent
Compression
Recurrent compression following previous surgical
treatment at the same level, either in the central
canal and/or lateral recess/foraminal regions
POSTER NO. P361
Neck-Shoulder Crossover: How Often Do Neck and
Shoulder Pathology Masquerade as the Other?
Jonathan N. Sembrano, MD, Minneapolis, MN
Sharon C. Yson, MD, Minneapolis, MN
Okezika C. Kanu, Minneapolis, MN
Edward Rainier G. Santos, MD, Minneapolis, MN
Jonathan P. Braman, MD, Minneapolis, MN
Alicia K. Harrison, MD, Minneapolis, MN
David W. Polly, Jr, MD, Minneapolis, MN
INTRODUCTION: Identification of the correct pain generator is
a pre-requisite for providing effective treatment in patients with
neck and/or shoulder problems. However, distinguishing between
the two could be difficult. The relative frequencies of how often
one is mistaken for the other have not yet been well-established.
METHODS: A total of 694 new patients were seen at the orthopaedic
shoulder clinic (n=454) and spine clinic (n=240) at an academic
institution during a two-year period. One-hundred-nine patients
had previous shoulder surgery, and 36 had previous neck surgery.
The 549 patients (shoulder clinic = 348; spine clinic = 201) who
had no previous surgery were reviewed for workup performed,
final diagnosis, subsequent operative procedures, and incidence
of referral from the shoulder to the spine clinic and vice-versa.
RESULTS: Among patients seen at the shoulder clinic, 323 (92.8%)
were found to indeed have shoulder pathology, nine (2.6%) had
neck and not shoulder pathology, eight (2.3%) had both shoulder
and neck pathology, and eight (2.3%) had an unidentifiable
cause of pain. Among the 17 patients who had neck pathology,
only one (0.3%) underwent neck surgery. Among patients seen
at the spine clinic, 175 (87.1%) were found to indeed have neck
pathology, nine (4.5%) had shoulder and not neck pathology, four
(2.0%) had both neck and shoulder pathology, and 13 (6.5%) had
an unidentifiable cause of pain. Among the 13 patients who had
shoulder pathology, only one (0.5%) underwent shoulder surgery.
DISCUSSION AND CONCLUSION: For patients presenting to a
shoulder surgeon’s clinic for shoulder pain, 5% will turn out to
have neck pathology. For patients presenting to a spine surgeon’s
clinic for neck pain, 6.5% will turn out to have shoulder pathology.
Thus, approximately one in 20 patients seen at a surgeon’s clinic
for either a presumed shoulder or neck problem exhibit a neckshoulder crossover, where pathology in one may be mistaken for
or co-exist with the other.
Description
POSTER NO. P362
POSTER NO. P363
Anterior Release Generates More Thoracic Rotation
Than Ponte Osteotomy: A Biomechanical Human
Cadaver Spine Study
Sagittal Plane Spinal Deformity: Correction Thresholds
and Health Related Quality of Life at Two Years Follow Up
Erin Farrelly, MD, New York, NY
Kate Meyers, MS, New York, NY
Seth Grossman, MD, Bronx, NY
Timothy M. Wright, PhD, New York, NY
INTRODUCTION: Historically, large and/or stiff spinal
deformities were treated with anterior release to facilitate
correction. However, anterior release increases risks and requires a
two-part procedure. Recently, large or rigid deformities have been
treated with a single posterior procedure using pedicle screws and
osteotomies. No study in the literature has evaluated the effect
of anterior release or posterior osteotomy on thoracic rotation.
METHODS: Fourteen fresh frozen human thoracic spines were
randomly assigned to anterior or posterior groups. Specimens were
disarticulated at T4-T5 and T8-T9 to test upper, middle, and lower
thoracic segments. Sections were potted, and reflective markers
were placed on the vertebrae of interest (T2-T3, T6-T7, T10-T11).
Specimens were mounted on a servo-hydraulic load frame.
Specimens were cyclically loaded to ±5Nm axial rotation for 10
cycles with data from the tenth cycle analyzed. Specimens were
tested intact then retested after sequential sectioning or removal
of various structures. Anterior structures removed were: ALL,
annulus fibrosis, nucleus pulposis, and PLL. Posterior structures
removed were: intraspinous ligament, inferior facets, superior
facets, spinous process, lamina, and ligamentum flavum. Motion
was recorded using a 3D motion capture camera, and the relative
motion of one vertebra to the other in axial rotation was calculated.
RESULTS: Posterior sectioning produced a 27-82% increase
in rotation from the intact specimens, while anterior release
generated a 201-534% increase. Removal of the annulus, nucleus,
and PLL led to a significant increase in rotation compared to
intact specimens. Ponte osteotomy increased rotation 1.84.2°, while anterior release increased rotation 6.6-13.4°.
DISCUSSION AND CONCLUSION: Anterior release generated
significantly more thoracic rotation than Ponte osteotomy in
biomechanical testing of human cadaver spines. An anterior or
posterior structure that contributed most to rotational stability
was not identified. Significance: Although many surgeons favor
a single posterior approach to correct severe spinal deformity,
anterior release may be needed to maximize correction. With
increased emphasis being placed on spinal derotation, the use of
anterior release should be reconsidered.
Edward Chay, New York, NY
INTRODUCTION: Recent studies have defined sagittal
plane mal-alignment as the main driver of disability in adult
spinal deformity (ASD). While normative values for sagittal
plane parameters have been defined, this study aims to
evaluate the amount of sagittal correction needed to achieve
a minimal clinically important difference (MCID) in health
related quality of life (HRQOL) scores for ASD patients.
METHODS: This was a multicenter, retrospective analysis of
consecutively enrolled ASD patients in a prospective database.
Using demographic, radiographic, and HRQOL pre-operative
and two-year post-surgery data, ASD patients were divided into
two groups: pre-operative lumbar lordosis (LL) 80mm. Further
subdivision was based on amount of correction: 15°, 15°-30°,
and >30° for LL, and 120mm for SVA. HRQOL measures were
Oswestry Disability Index (ODI), Scoliosis Research Society
Questionnaire (SRS-22r) and Short Form 12 (SF-12). Statistical
analysis was performed using paired t-test and one-way ANOVA.
RESULTS: There were 79 and 76 patients in LL and SVA,
respectively. Each group showed HRQOL improvements between
pre-operative and two-year evaluations (p<0.05). In LL (mean
pre-op LL=13°), an increase of <15° improved HRQOL (SRS22r: 0.763 points; ODI: -15 points; p<0.05). Increasing LL by
15°-30° increased the likelihood of MCID for SRS activity
(92%) and appearance (91%) (p30° increase in LL decreased
the likelihood of MCID for SRS activity (61%) and appearance
(74%) (p<0.05). In SVA (mean pre-op SVA=14cm), correcting
by <60mm resulted in HRQOL improvements (SRS-22r: 0.757
points; ODI: -12 points, p120mm increased the likelihood
of MCID in SRS appearance, ODI and SF-12 PCS (p<0.05).
DISCUSSION AND CONCLUSION: The best HRQOL outcomes
for ASD patients with severe sagittal plane deformity were obtained
with corrections of 15°-30° for LL and >120mm for SVA. These
results identify surgical correction thresholds for reaching HRQOL
improvements for severe ASD patients.
POSTER NO. P364
Myelomalacia on MRI is Poorly Correlated with Severity
of Disease in Cervical Spondylitic Myelopathy
Joseph Nguyen, MPH, New York, NY
Dara Froemel, MD, New York, NY
INTRODUCTION: Myelomalacia is an MRI finding which
suggests spinal cord damage. However, it is not uniformly
found in patients with cervical spondylitic myelopathy (CSM)
1005
and its presence on MRI is of unknown prognostic significance.
We aim to provide correlative data between Myelomalacia and
its prevalence in patients with CSM. We hypothesize that the
presence of myelomalacia is associated with more advanced
myelopathy and overall is an indication of poor prognosis.
myelopathy patients who underwent surgical intervention of three
spine surgeons between 1/2000 and 10/2010 at our institution.
Patient demographics, medical office records, duration of
myelopathic symptoms and surgical levels were collected. Special
focus was placed on Nurick Grade at presentation and evidence
of myelomalacia on MRI. Post-operative symptom resolution and
Nurick grade was also recorded. Chi-Square test was performed
followed by a multivariate logistic regression analysis between the
presence of myelomalacia and post-op improvement in Nurick Grade.
RESULTS: A total of 259 patients (71 F; 188 M) were included in
this study. The average age was 59.26±13.3 and average BMI was
28.3±5.1. Pre-operative duration of myelopathic symptoms until
surgical intervention was 14.93 months (1-101 months) and the
average follow up was 15.3 (range 1-79 months). Myelomalacia was
present in 51%, 35%, 11% and 3% of patients with pre-op Grade
1, 2, 3, 4 disease respectively (p=0.02, 0.26, 0.002, 0.329). Overall,
only 27% of the patients with myelomalacia had an improvement
in Nurick grade with surgery (p=<0.001). Myelomalacia had a
negative correlation with post-op improvement with an adjusted
odds ratio (aOR) of 0.26, 0.27 and 0.01 for patients who improved
to Grade 2, 1 and 0 disease (p=<0.001, <0.001, <0.001) respectively.
DISCUSSION AND CONCLUSION: Myelomalacia is not
associated with disease severity in CSM but provides significant
information on the recovery that patients may receive with surgical
intervention. The presence of myelomalacia on MRI indicates a
lower likelihood of improvement with surgical intervention than
in the absence of this finding.
POSTER NO. P365
The Insertion Technique of Translaminar Screws in the
Thoracic Spine: CT and Cadaveric Validation
portion of the base of the transverse process of the contralateral
side, and followed carefully to not break the inner/outer cortex of
the lamina. The length of the hole, representing the trajectory of
the screw made by the drill guide, was measured, and the 1° screws
were inserted according to the length measured. The entry point for
the 2° screw was the distance of the diameter of the screw below
the superior margin of the base of the spinous process and lamina
junction. The drill guide was pointed toward the inferior angle of
the contralateral junction of the rib and the vertebra along the slope
of the contralateral lamina. The 2° screw was inserted in the same
manner as before. The 2° screw diameter was downsized if there
was not enough space due to the 1° screw. For each vertebra from
the 11 separated cadaveric spines, medial or lateral cortex breakage
was checked visually. For the remaining four non-separated spines,
CT scan was used to find any medial or lateral cortex breakage.
RESULTS: Thirty-three vertebral levels were abandoned from
Group S due to altered anatomy. Out of 147 vertebral levels,
there was no vertebra that didn’t allow screw insertion. No
specimen required downsizing the 2° screws due to blockage
of the 1° screw. There was no cortical breakage by the screws
in group S. In group N-S, CT scan showed four medial cortex
breakages (2.72%) and three lateral cortex breakages (2.04%),
all of which were slight cortical breakages. There were no facet
injuries due to the screws in group N-S. There was no blockage
of the ribs during screw placement in all specimens, and the
drill guide could lean against the rib for guidance because the
angle of the rib and the opposite lamina tended to be the same.
DISCUSSION AND CONCLUSION: Translaminar screws can
be inserted relatively safely in the thoracic spine. For the 1°
translaminar screw, the entry point is the distance of the diameter
of the desired screw superior to the inferior margin of laminaspinous process junction. The trajectory should be targeted towards
the center of the base of the contralateral transverse process. For
the 2° translaminar screw, the entry point is the distance of the
diameter of the desired screw below the superior margin of laminaspinous process junction, and the target is the inferior angle of
the junction of the rib and the vertebra on the contralateral side.
INTRODUCTION: Translaminar screws can be a good
salvage technique in some cases of severe deformities,
infection, tumor, osteoporosis, and revision cases with altered
anatomy. To our knowledge, the insertion technique for
translaminar screws in the thoracic spine has not been studied.
METHODS: Fifteen cadaveric spines were harvested from T1 to
T12 and 1mm CT scans and 3D reconstructions were obtained to
rule out any bony anomaly. Eleven of the cadaveric spines were
separated at each level from T1 to 12 (Group S), and four were
not separated (Group N-S). Translaminar screws were inserted into
every level along the trajectories proposed by the previous studies
(Cho 2010 CSRS, 2011 AAOS)(Fig). The screw diameter was
determined based on the reference article (Xu Spine 1999). For T1-6,
screw diameters selected were 4mm; for T7-12, a 3.5mm screw was
utilized instead. The entry point for the 1° screw was the distance
of the diameter of the desired screw superior to the inferior margin
of the spinolaminar junction. To create the trajectory, a drill guide
was inserted at the entry point and directed toward the middle
1006
POSTER NO. P366
A New Midline Anterior Approach from the Right Side
to the Lumbar Spine for Anterior Spine Surgery
Gregory Edgard-Rosa, MD, Castelnau le lez, France
Guillaume Geneste, MD, Castelnau-le-Lez, France
Georges Negre, MD, Castelnau Le Lez, France
Sebastian Parratte, MD, Marseille, France
Thierry Marnay, MD, Castelnau Le Lez, France
INTRODUCTION: Midline anterior approach to the lumbar
spine has developed during these last years, mainly for interbody
fusion and disc arthroplasty surgery. This retroperitoneal
approach is well described in publications and classically made
from the left side. Major complications associated with the
approach are known: retrograde ejaculation, venous injuries
and arterial thrombosis.The aim of this prospective study was
to describe a midline anterior approach to the lumbar spine
from the right side, below the aortic bifurcation to L5S1 and
by mobilizing the vena cava from right to left between L2
and L5 and to evaluate the feasibility and complication rate.
METHODS: A total of 469 patients were included in a
prospective study between August 2003 and November 2010,
either for interbody fusion by anterior approach or for total disc
replacement, on one or several levels between L2-L3 and L5-S1.
RESULTS: Of the 154 patients who had a mobilization of
the vena cava, no injury occurred. Only four major venous
injuries occurred. There was no arterial complication
and the oxygen saturation signal was interrupted in only
one case. No case of retrograde ejaculation was found.
DISCUSSION AND CONCLUSION: The midline anterior
retroperitoneal approach from the right side is a safe alternative
compared to the classical approach from the left side. The low rate
of venous injury is explained by the sidewall thickness of the vena
cava compared to the left iliac vein sidewall. Contrary to what
happens by left sided approach, the vascular retraction required
for access to L4-L5 and above does not lead to arterial occlusion
and therefore diminishes the risk in atheromatous patients. The
absence of retrograde ejaculation confirms previous studies
made on the left anastomosis of the superior hypogastric plexus
suggesting that its approach and mobilization by the left side is
delicate.
mineral densities with age, but also suggest specific vertebral levels
at higher risk for fractures. These data may help further identify
patients at risk for fractures, and, as a result, may help inform
clinical decision making and targeted therapeutic interventions.
POSTER NO. P367
Analysis of Variance in Vertebral Bone Mineral Density
Shaun P. Patel, BS, Ann Arbor, MI
Sven Holcombe, BS, Ann Arbor, MI
Stewart C. Wang, Ann Arbor, MI
James A. Goulet, MD, Ann Arbor, MI
INTRODUCTION: Worldwide, vertebral fractures are estimated
to occur once every 22 seconds. They are a source of significant
morbidity and healthcare expenditure, which will continue
to increase as our population ages. Along with increased age,
low bone mineral density is known to be a significant risk
factor contributing to vertebral fractures. However, few studies
have investigated whether there is variance in bone mineral
density across vertebral levels and with respect to sex and age.
METHODS: We identified 2,622 trauma patients between 2002
and 2010 who underwent a CT scan encompassing any part
of their thoracic or lumbar spine. All CT scans were processed
using semi-automatic algorithms through MATLAB R2011a.
The mean Hounsfield Unit (quantitative scale for describing
radiodensity) within each vertebral body was ascertained,
which served as our measure of bone mineral density. This
was performed at each vertebral level present on a given CT
scan. Mean bone mineral density values were subsequently
analyzed with respect to vertebral level, sex, and age.
RESULTS: Analysis of CT scans yielded 26,346 unique vertebrae
(17,067 male, 9,279 female) for which bone mineral density
measurements were obtained. Across both sexes, there was a
downward trend in bone mineral density with age (Figures 1 and
2). Across both sexes and nearly all age ranges, the lowest mean
bone mineral density among thoracic vertebrae was at T8 and
among lumbar vertebrae it was at L3. These were significantly
lower when compared to the mean bone mineral density of the
cumulative vertebrae for any corresponding age range (p < 0.05).
DISCUSSION AND CONCLUSION: With this work, we present a
large scale analysis of vertebral bone mineral density values across a
diverse population. Our findings not only reaffirm declining bone
1007
POSTER NO. P368
uTransforaminal Lumbar Interbody Fusion: Outcomes
Among 155 Consecutive Patients from a High-Demand
Population
Dimitri M. Thomas, MD, El Paso, TX
Julia O. Bader, PhD, El Paso, TX
INTRODUCTION: Transforaminal interbody fusion (TLIF) is a safe
and effective technique for achieving lumbar fusion with anterior
column support. Few studies, however, have addressed outcomes
following TLIF, especially in physically active and high demand
populations, such as the U.S. military. This study sought to evaluate
the efficacy of TLIF among active duty service members using
retention within the military as an endpoint. The study also aimed
to identify factors predictive of successful outcome following TLIF.
METHODS: A consecutive cohort study was performed for all
patients undergoing TLIF within our department from 20052008. In total, 155 active duty service members receiving TLIF
were followed for a minimum of two years. The electronic medical
record was abstracted for demographic information including age,
gender, rank, branch of service, and smoking status. Pre-operative
diagnosis, presence of fusion, number of levels at which TLIF
was performed, complications, and revision surgeries were also
noted. The ability of the patient to remain on active duty service,
and whether they received a medical discharge for their spinal
condition were determined as the dependent variable. Univariate
and multivariate analyses were utilized to determine independent
factors predictive of successful outcome following TLIF.
RESULTS: The average age of the patients in the study was 36.3
years of age. Most patients (n= 136) were male and 19 were
female. Thirty-five patients were junior enlisted, 106 were senior
enlisted and there were 14 officers. Ninety-seven patients were
non-smokers. The majority of patients (n=148) were in the Army
and most carried a diagnosis of degenerative disc disease (n=129).
Eighty-one patients had single level fusions, whereas 74 had two
or more levels. There were six complications that required seven
subsequent procedures. Medical discharge for a spinal condition
occurred in 30.3% (47/155) of patients, whereas 69.7% (108/155)
were able to remain in the military. Univariate analysis determined
that age (p < 0.001) and military rank (p < 0.0003) were predictive
of retention, with older service members and those of higher rank
more likely to remain on active duty. Following multivariate testing,
only rank (p < .02) was found to be correlated with retention.
DISCUSSION AND CONCLUSION: Approximately 70% of those
receiving TLIF were able to remain on active duty. Older age and
high military rank were predictive of retention. This may be
indicative of patient motivation, occupational demands, and/
or social support structures that may play a role in influencing a
patient’s ability to remain in the military following TLIF. Results
presented here show that TLIF is a successful intervention for
younger, high-demand patients serving within the military.
POSTER NO. P369
The Age-Specific Prevalence of Pediatric Spine Injuries
Parallels the Rate of Motor Vehicle Injuries and Death
Sergio A. Mendoza-Lattes, MD, Iowa City, IA
Yubo Gao, PhD, Iowa City, IA
Gnanapradeep Gnanapragasam, MBBS, West Des Moines,
Iowa
Rachel Nash, Iowa City, IA
Stuart L. Weinstein, MD, Iowa City, IA
METHODS: The Healthcare Cost and Utilization Project
(HCUP) Kid’s Inpatient Database (KID) consists of data from
3,739 hospitals in 38 states and includes 3,452,325 nonbirth discharges from children 0-19 years old. Age-specific
prevalence of spine and spinal cord injuries are calculated.
Weighed data is presented for the 2006 U.S. population. These
results are compared with the National Highway Traffic Safety
Administration (U.S. DOT) 2006 report on injuries and mortality.
RESULTS: The prevalence of spinal injuries for 2006 was
106.8pmp (per million population) under the age of 20; 66%
higher than other industrialized nations. Children age 15-19
accounted for 81.2% of all injuries (prevalence of 240.2pmp)
(figure 1). Sixty percent of all spine injuries in children and
adolescents were related to motor vehicle collisions. This
was particularly relevant, in the group older than 15 years.
DISCUSSION AND CONCLUSION: The prevalence of spinal
injuries in children under the age of 20 (106.8pmp), represents a
34.7% increase in 10 years (1997 - 2006). The majority of spine
injuries occurred in children 15-19, and were predominantly
related to motor vehicle collisions.
1008
POSTER NO. P370
Duration of Symptoms has No Correlation to Disease
Severity in Cervical Spondylitic Myelopathy
Dara Froemel, MD, New York, NY
Michael Mayer, MD, Salzburg, Austria
INTRODUCTION: There is debate over the association of the
duration of symptoms and disease severity in cervical spondylitic
myelopathy (CSM). However, prolonged duration of symptoms
may not necessarily correlate to more progressive forms of the
disease. We aimed to associate duration of symptoms with disease
severity in CSM measured by Nurick grade. We hypothesize that
longer duration of symptoms are associated with more advanced
Nurick Grade and a worse prognosis with surgical intervention.
myelopathy patients who underwent surgical intervention
by three spine surgeons between 1/2000 and 10/2010 at our
institution. Patient demographics, medical office records, duration
of myelopathic symptoms and surgical levels were collected.
Special attention was focused on the duration of myelopathy
symptoms. Post-operative symptom resolution and Nurick grade
was also recorded. Chi-Square test was performed followed by a
multivariate logistic regression analysis between the presence
of myelomalacia and post-op improvement in Nurick Grade.
RESULTS: A total of 259 patients (71 F; 188 M) were included in
this study. The average age was 59.26±13.3 and average BMI was
28.3±5.1. Pre-operative duration of myelopathic symptoms until
surgical intervention was 14.93 months (1-101 months) and the
average follow up was 15.3 (range 1-79 months). More advanced
Nurick grades did not correlate with longer duration of symptoms
(p=0.813). However, those who improved at least one Nurick grade
with surgical intervention had 6.1 months shorter duration of
symptoms than those who stayed the same or worsened with surgery
(11.2 vs. 17.3 months respectively, p = 0.003). Multivariate logistic
regression showed a negative correlation with duration of symptoms
and recovery with surgical intervention to at least grade 2, 1 or 0
disease (aOR 0.96, 0.97, 0.97 respectively, p=0.002, 0.004, 0.029).
DISCUSSION AND CONCLUSION: Duration of myelopathic
symptoms do not correlate with severity of disease which question
the natural history of CSM. However, those patients who did
not improve with surgery had a longer duration of symptoms by
approximately six months.
POSTER NO. P371
Preoperative Vitamin D Status of Adults Undergoing
Spinal Fusion Surgery
Geoffrey Stoker, BS, Saint Louis, MO
POSTER NO. P372
INTRODUCTION: Vitamin D plays a critical role in establishing
optimal bone health, which, in turn, is vital to the success
of
spinal
arthrodesis.
Furthermore,
deficiency-induced
osteomalacia and osteoporosis predispose to postoperative
screw pullout and instrumentation failure. The purpose of
this study was to characterize the prevalence of preoperative
vitamin D abnormality in adults undergoing spinal fusion
and to determine whether previously identified risk factors
for suboptimal vitamin D can be applied to our population.
METHODS:
Serum 25-hydroxyvitamin D (25OHD) levels
were prospectively measured in adults (at least 18 years old)
undergoing spinal fusion at a single institution. Between
1/2010 and 3/2011, 313 consecutive patients were identified for
inclusion in this cross-sectional investigation. We generated a
composite disability instrument by pooling Neck and Oswestry
Disability Index scores of cervical and thoracolumbar patients,
respectively. Potential risk factors for vitamin D deficiency
were analyzed using Fisher’s exact, chi-squared, and MannWhitney U tests as well as multivariate logistic regression.
RESULTS: The mean baseline 25OHD level was 29 ± 14 ng/mL. The
prevalence of vitamin D inadequacy (<30 ng/mL) was 57%, and
that of deficiency (<20 ng/mL) was 27%. There were 176 (56%)
females. The overall mean age and BMI were 55 ± 13 years and 29 ±
5.8 kg/m^2, respectively. While 260 patients were diagnosed with
degenerative disease, 99 had spinal deformity, and there were 73
revision cases. The cervical spine was included in 48% of fusion
constructs; thoracic spine, 39%; lumbar spine, 51%. On average,
4.8 ± 4.7 motion segments were included. Deficient patients were
younger (P = 0.009) and more likely to be <50 years old (P <
0.050). There was no gender difference. Bone mineral density was
not lower in the setting of deficiency (P = 0.734). Deficient patients
had significantly higher body mass index (BMI; P = 0.001) and
disability scores (P = 0.004); likewise, they were more liable to be
obese than of normal BMI (P = 0.001) and rate their disability greater
than or equal to 60 than <60 (P = 0.005). The subgroup of patients
with prior vitamin D and/or multivitamin supplementation was
significantly older (P < 0.001) and more likely to be at least 50 years
of age than those without prior repletion (P = 0.001). Increasing
BMI (OR = 0.92, 95% CI = 0.87 - 0.97, P = 0.003), increasing
disability scores (OR = 0.97, 95% CI = 0.95 - 0.99, P = 0.028), and
a lack of prior vitamin D or multivitamin supplementation (OR =
0.14, 95% CI = 0.05 - 0.39, P < 0.001) reMEd significant predictors
upon multivariate analysis. In other words, each one-unit increase
in disability index equated to a 3% decrease in the likelihood of
having 25OHD of at least 20 ng/mL. In contrast, a lack of prior
supplementation conferred an 86% decrease in those odds.
DISCUSSION AND CONCLUSION: Our investigation revealed
an alarmingly high rate of vitamin D abnormality in the
1009
analyzed population. Since augmenting serum 25OHD is
straightforward and inexpensive, and hypovitaminosis-induced
spinal osteoporosis and osteomalacia may predispose to poor
surgical outcome, we advocate repletion for spine patients
with documented deficiency. Although advanced age is a wellestablished risk factor for deficiency, young adults undergoing
spinal fusion should not be overlooked with regard to preoperative
vitamin D screening; younger patients are less likely to have been
previously supplemented. Moreover, as validated indices of spinerelated disability are predictive of vitamin D deficiency, these
may be clinically useful tools in identifying at-risk patients in the
absence of other well-established, physiologic risk factors.
uThe Reliability of X-Ray Based Evaluation of Pedicle
Screw Misplacement in Adolescent Spinal Deformity
Paul Haynes, MD, Ocean, NJ
Beverly Thornhill, MD, Bronx, NY
Gordon Sims, BA, Bronx, NY
Jonathan Horn, Bronx, NY
Preethi M. Kulkarni, Bronx, NY
INTRODUCTION: Post-operative x-rays are routinely used to detect
misplaced pedicle screws. Kim, et al. have defined radiographic
criteria for evaluation of screw placement in spinal deformity. This
study evaluates pedicle screw misplacement on x-ray using these
criteria as well as anterior placement on lateral x-ray, and compared
them to screw misplacements seen on post-operative CT scan.
METHODS: Post-op x-rays and low dose CT scans of 104 adolescent
spinal deformity patients who underwent PSF were reviewed. A
blinded review of screw placement on x-ray was carried out using
Kim et al.’s criteria: 1)violation of the harmonious change; 2)
no crossing of medial pedicle wall by screw tip; 3)violation of
imaginary midline of the vertebral body. On lateral x-ray, a screw
was considered misplaced if: 1) an anterior breach was seen or 2)
the length of the screw inside the vertebral body was ≥ 80% of the
width of the vertebral body. Kappa analysis was used for overall
agreement as well as agreement within specific regions of the curve.
RESULTS: A total of 2,087 screws were evaluated on x-ray and
CT. CT classified 1,820 screws as acceptable, 143 lateral, 30
medial, and 94 anterior. X-ray had 908 acceptable, 304 lateral,
241 medial, and 634 anterior. X-ray correlated with CT Scan in
50% of acceptable screws, 213% of laterally placed screws, 803%
of medially placed screws, and in 674% of anteriorly placed
screws. X-ray overestimated the number of misplaced screws and
had poor reliability for detecting properly placed screws. Overall
agreement was 0.08, indicating poor correlation. 53 screws were
identified by CT scan as concerning - either breeching the canal
or lying adjacent to the aorta. Of these, only 35% were correctly
classified on x-ray. Further review of these screws on x-ray was
unable to identify any relationship to structures of concern.
DISCUSSION AND CONCLUSION: X-ray evaluation of screw
placement showed poor correlation with CT data. X-rays were found
to be inadequate to evaluate screw misplacement or relationship
to structures of concern. Routine postoperative x-rays have
significantly high false positive rates for screw misplacement. The
practice of evaluating accuracy on x-ray needs to be examined. Low
dose CT scan or intra-op image guidance should be considered.
POSTER NO. P373
ALTERNATE PAPER: SPINE VI
POSTER NO. P374
Patient Impressions of Reimbursement for Orthopedic
Spine Surgeons
M. M. Gomberawalla, MD, Ann Arbor, MI
Jeffrey S Fischgrund, MD, Southfield, MI
Gregory Graziano, MD, Ann Arbor, MI
Rakesh Patel, MD, Ann Arbor, MI
INTRODUCTION: The purpose of this study was to understand
patients’ impressions of reimbursement to orthopedic spine surgeons.
METHODS: A survey was mailed to patients who underwent a spine
procedure within the past three to 15 months at an academic and
private institution. Surveys were returned in an anonymous fashion.
RESULTS: A total of 103 surveys were completed. Some 76% of
patients underwent a larger procedure (cervical fusion, lumbar
fusion, or laminectomy with fusion), while others underwent
a smaller procedure (kyphoplasty, discectomy, or laminectomy
without fusion). Of those who underwent smaller procedures,
69% of patients felt the per-procedure reimbursement was between
$1,000 and 5,000. Of those who underwent larger fusion-based
procedures, 84% of patients felt the reimbursement was greater
than $5,000, of which 28% believed the reimbursement was
greater than $15,000 for their procedure (Figure 1). Most patients
(73%) believed procedural reimbursement should primarily
be based on technical difficulty. Only a minority of patients felt
that in-hospital rounding and outpatient follow up in the first
90 days were included in the procedural reimbursement (38%
and 26%, respectively). A total of 41% of patients believed spine
surgeons’ annual salaries are between $250,000 and $500,000,
and 22% believed it was between $500,000 and $750,000.
Most patients (73%) felt that spine surgeons are appropriately
compensated. Thirty-eight percent of patients believed
reimbursement should be addressed as a part of healthcare reform.
DISCUSSION AND CONCLUSION: A majority of patients believe
spine surgeons are reimbursed a higher amount per procedure than
factually true. Despite this, most patients feel that spine surgeons
are appropriately compensated. Additionally, most patients are not
aware that early post-operative inpatient rounding and outpatient
clinical care are included within the global billing period.
Cervical Sagittal Contour Decompensation Before and
After Surgery in Adolescent Idiopathic Scoliosis
Brian Winters, MD, Mount Laurel, NJ
Petya Yorgova, MS, Wilmington, DE
Geraldine Neiss, PhD, Wilmington, DE
INTRODUCTION: The cervical sagittal contour of patients with
adolescent idiopathic scoliosis (AIS) may be clinically important,
as neck pain is a major complaint in long term follow up studies.
Cervical spine alignment and sagittal vertical axis are affected by
thoracic kyphosis. Thoracic hypokyphosis is a common feature
of AIS and can be aggravated by contemporary instrumentation
techniques with segmental pedicle screw systems. This study sought
to examine the relationship of thoracic hypokyphosis and cervical
spine sagittal contour before and after posterior spinal fusion for AIS.
METHODS: A single-surgeon’s prospective, consecutive series
of patients (2005-2008) treated with segmental pedicle screw
instrumentation for thoracic AIS (Lenke 1,2) with minimum
two year follow up yielded 65 patients with adequate cervical
spine views for analysis. Cervical sagittal contour was measured
by one of two observers from the inferior endplate of C2 to
the inferior endplate of C6, as described by Hilibrand, et al
(1995) preoperatively, at the first erect film and at two year
follow up. Arm position was standardized with hands resting
on poles and arms flexed forward 20-30°. A comprehensive
collection of global and local sagittal parameters were analyzed.
RESULTS: “Flattening” of the cervical sagittal contour was observed
in patients with AIS before and after surgery. Preoperatively, the
sagittal contour from C2-C6 was 7.0 ± 2° of kyphosis and 4.6 ±
2° of kyphosis two years after surgery (p<0.01). Thoracic sagittal
contour preoperatively was 28 ± 6° of kyphosis (T2-T12) and was
preserved after surgery (29.6 ± 3°). A strong correlation existed
between thoracic hypokyphosis and the development of cervical
kyphosis - and this was significant preoperatively (p=0.003) and
two years postoperatively (p=0.004). A relatively small correction
of the thoracic kyphosis (4.8%) translated into a substantial
and spontaneous correction in the cervical lordosis of -39%.
DISCUSSION AND CONCLUSION: In AIS, thoracic hypokyphosis
is associated with a risk of cervical decompensation into kyphosis.
Efforts to restore even some thoracic kyphosis postoperatively
during scoliosis surgery may have profound effects in establishment
of cervical lordosis.
POSTER NO. P375
Ultrasonographic Quantification of Spinal Cord and
Dural Pulsations during Cervical Laminoplasty
Atsushi Kimura, MD, Shimotsuke, Japan
Atsushi Seichi, MD, Shimotsuke, Japan
Hirokazu Inoue, MD, Shimotsuke, Tochigi, Japan
Teruaki Endo, Shimotsuke City, Japan
Yuichi Hoshino, MD, Tochigi, Japan
INTRODUCTION: Pulsatile movements of the spinal cord and dura
mater have been interpreted as a sign that the cord is free within
the subarachnoid space, with no extrinsic compression. However,
the association between restoration of pulsation and adequate
decompression of the spinal cord has not been established. The
purpose of this study was to investigate the relationship between
the extent of spinal cord decompression and spinal cord and dural
1010
pulsations by quantitative analysis of intraoperative ultrasonopraphy.
METHODS: The study enrolled 85 consecutive patients with cervical
myelopathy (55 male, 30 female; mean age 64 ±13 years). Spinal
cord decompression status was classified as: Type 1, noncontact,
retaining the presence of the subarachnoid space on the ventral side
of the cord; Type 2, contact and apart, with the cord showing contact
with and separation from the anterior element of the cervical spine;
and Type 3, contact, with the cord in continuous contact with
the anterior element. Spinal cord and dura mater dynamics were
analyzed quantitatively using automatic video-tracking software.
RESULTS: The amplitude of spinal cord pulsations ranged from
0.01-0.84 mm (mean 0.30 ± 0.16 mm) and that of dural pulsations
ranged from 0.01-0.38 (mean 0.14 ± 0.08). The average spinal cord
pulsation amplitude in type 2 patients was significantly larger than
in other types. However, the average dural pulsation amplitudes
were similar in all groups. There was a significant correlation
between spinal cord and dural pulsation amplitudes in type 1, but
not in type 2 or type 3 patients. Type 3 patients showed a particularly
poor correlation between spinal cord and dural pulsations.
DISCUSSION AND CONCLUSION: The results of this study
revealed that restoration of dural pulsation is not a reliable indicator
of sufficient spinal cord decompression following a decompression
procedure.
POSTER NO. P376
Protective Changes in Cervical Spine Geometry
Occurring with Age: A Cadaveric Study of 1,072 Human
Skeletons
Navriakt Bajwa, Cleveland, OH
INTRODUCTION: Prior studies have shown changes in lumbar
vertebral parameters such as vertebral body diameter, sagittal
diameter, interpedicular distance and pedicle length with age.
Few studies have been done to evaluate changes in cervical spine
morphology with age, and these have primarily been in the
pediatric population. However no studies have been done which
study the changes in cervical anatomy with age in adulthood. This
study was performed to determine changes in cervical morphology
which occur with age in adults, and whether these changes have an
impact on development of cervical stenosis with advancing age.
METHODS: A total of 1,072 cadaveric lumbar specimens from
Hamann-Todd Osteological Collection in Cleveland, OH were
examined by a single examiner. Baseline data including age,
sex, and race of subjects were collected. The gross specimens
were measured subjectively with digital caliper. The following
measurements were made; body diameter, measured as the
anteroposterior distance of each vertebral body, the interpedicular
distance, the sagittal diameter and pedicle length at each of the
cervical levels (C3-C7). Linear regression analyses were then
used to determine the relationship between these parameters
while correcting for confounding factors of age, sex and race.
RESULTS: In all the specimens, there was a significant positive
association between changes in body diameter with age from C3 to C7
(p<0.01). At all levels there was also a significant association between
sagittal diameter and age (p<0.01). Pedicle length was associated
with age only at levels C4, C5 and C7 (p<0.03). Interpedicular
distance was not significantly associated age at any level (p>0.1).
DISCUSSION AND CONCLUSION: This study suggests that
changes occur in body diameter, sagittal diameter and pedicle
length with age in adulthood. The increases in cervical sagittal
diameter, in particular, are interesting as this parameter impacts
the presence of cervical stenosis. The forces across the cervical
spine may result in degenerative changes which lead to cord
1011
compression, but these same forces also appear to cause alterations
in bony anatomy with age, with an increase in sagittal diameter and
which in turn may have a protective effect in preventing cervical
stenosis. This may explain why cervical stenosis leading to cord
compression and myelopathy is uncommon despite tremendous
forces on cervical spine that occur over the course of time.
POSTER NO. P377
The Prevalence of Abnormal Preoperative Neurologic
Exam in Scheuermann’s Kyphosis
Guangxun Hu, Shenzhen City, China
Joshua Pahys, MD, Wynnewood, PA
Samuel Kang-Wook Cho, MD, Palisades park, NJ
Matthew M. Kang, MD
Linda A. Koester
INTRODUCTION: There have been sporadic reports about
abnormal neurologic findings in Scheuermann’s kyphosis
patients. The purpose of this study was to report the
prevalence of abnormal neurologic findings detected by
physical exam in Scheuermann’s kyphosis, and to correlate
it to x-rays, MRI findings, and results of operative treatment.
METHODS: Among 82 Scheuermann’s kyphosis patients who
underwent corrective surgery, 69 primary cases were selected.
Patient charts were reviewed retrospectively in terms of pre
and postop neurological exams. Sensory or motor change
was defined as an abnormal neurologic exam. Their duration,
associated problems, and various parameters on preop x-rays
and MRI exams were also measured to search for any atypical
findings associated with an abnormal neurologic exam.
RESULTS: There were six cases (9%)(Group AbN) with an abnormal
neurologic exam ranging from severe myelopathy to a subtle change
(eg. sensory paresthesias on trunk). Five patients recovered to a
normal neurologic exam after corrective surgery. The remaining
one severe myelopathic patient also showed marked improvement
and was ambulatory unassisted by two-year follow up. In patients
with a normal neurologic exam (Group N, n=63), only one patient
had neurologic sequelae due to anterior spinal artery syndrome
after combined A/P correction. No preop x-ray parameters were
significantly different between groups. Average age was 21.3
(AbN) and 18.6 (N) yrs (P=0.55). Average preop T5-12 kyphosis
was 69.0º(AbN) and 72.5º(N) (P=0.61). Forty-two MRIs were
obtained, all showed typical findings of Scheuermann’s kyphosis.
In AbN, five patients had MRI (one had a Ct/myelo) and in 37 in N.
DISCUSSION AND CONCLUSION: The prevalence of abnormal
neurology in Scheuermann’s kyphosis was 9%, emphasizing
the importance of detailed preop neurologic exam. If congenital
stenosis or herniated thorathic disc is combined, myelopathy
can occur. No x-ray findings correlated with the abnormal preop
neurologic exam. A normal MRI can exist in the face of an abnormal
neurologic exam, and conversely, a normal neurologic exam can
be seen with an abnormal MRI as well. Surgery was successful in
alleviating abnormal neurologic issues. Deformity surgeons who
correct Scheuermann’s kyphosis should rule out neurologic issues
preoperatively.
1012
POSTER NO. P378
Increased Incidence of C2 Fractures in the Elderly
Population
Yohan Robinson, MD, Uppsala, Sweden
Bengt Sanden, MBBS, Uppsala, Sweden
Claes Olerud, MD, Uppsala, Sweden
INTRODUCTION: Fractures of the second cervical vertebra
- axis - are a common injury in the elderly population and
treatment is often complicated due to patient morbidity. The
number of geriatric patients increased during the last decades
due to an increase in mean population age. Until now little
epidemiological data is available allowing investigating whether
the number of C2 fractures increased during the last decade.
METHODS: Data for all patients with C2 fractures admitted
to hospital between 1997 and 2009 were abstracted from the
Swedish National Hospital Discharge Register (SNHDR). The data
in the register are collected prospectively, recording all inpatient
admissions throughout Sweden. The SNHDR uses the codes for
diagnoses at discharge and surgical procedures according to the
Swedish version of the International Classification of Diseases (ICD).
RESULTS: A total number of 4,444 patients (2,072 women, 2,372
men) with C2 fractures were treated as inpatients in Sweden during
the years from 1997 to 2009. Of these 1,267 were operated. The
annual incidence of C2 fractures showed a linear increase during
the years (r=0.92). This was mainly due to an increase in the
geriatric subgroup, while the younger age groups reMEd unchanged
during the observation period. Interestingly the percentage
of operated patients rather decreased until 2009 (r=-0.65).
DISCUSSION AND CONCLUSION: While the elderly population
grows dramatically, the number of hospital admissions due to
elderly-specific C2 fractures increased during the last decade.
Possible explanations are greater awareness of fractures, improved
diagnostics, and a higher activity level of the patients. Due to the
continuous increase of odontoid fractures treatment modalities
have to be optimised to reduce fatalities. Obviously there is a trend
to more conservative treatment in Sweden. Randomized controlled
trials allowing evidence-based recommendations are needed to
establish a treatment rationale for C2 fractures.
POSTER NO. P379
Instability
1
1
Clinical Outcomes after Lumbar Fusion Complicated by
Deep Wound Infection: A Case-Control Study
Stenosis
2
2
Scoliosis
2
2
Disc pathology
5
5
Non-union
3
3
Post-decompression
5
5
Adjacent level
4
4
Age
44.77
44.57
0.864
Length of Stay
5.37
5.57
0.731
Operative Time
288.17
259.27
0.298
Estimated Blood Loss
857.59
750.86
0.617
ASA Grade
2.63
2.83
0.136
No. of Levels
1.93
1.83
0.705
BMI
31.62
34.22
0.200
Back Pain
7.31
7.87
0.413
Leg Pain
7.52
7.67
0.821
ODI
56.82
55.30
0.721
PCS
26.91
26.49
0.832
MCS
35.06
37.40
0.548
Back Pain
4.70
6.45
0.020
Leg Pain
5.07
5.73
0.392
ODI
39.73
48.20
0.198
PCS
34.25
30.04
0.144
MCS
37.98
37.65
0.931
Back Pain
17
13
0.439
Leg Pain
23
22
1.000
ODI
18
8
0.018
PCS
15
15
1.000
Julio Petilon, MD, Portsmouth, VA
John R. Dimar, II, MD, Louisville, KY
Leah Y. Carreon, MD, Louisville, KY
INTRODUCTION:
Postoperative
infection
following
instrumented spinal fusion is a major complication, often
resulting in substantial short term morbidity. However, there
is little literature reviewing how these patients do in the longer
term, after their infection has been managed. This study evaluated
the two-year clinical outcomes of patients who had instrumented
spinal fusions complicated by deep wound infections and
compared them to a propensity-matched control group.
METHODS: Surgical and clinical databases from 2001 to 2008
were reviewed for eligible subjects. Inclusion criteria consisted
of patients who underwent instrumented lumbar spinal fusion
with complete pre-operative and two-year postoperative outcome
measures and had acute (≤3 months) postoperative deep wound
infections necessitating irrigation and debridement. Thirty
subjects met criteria for analysis. Outcome measures included the
Oswestry Disability Index (ODI), SF-36 Physical (PCS) and Mental
(MCS) composite summaries and Numeric rating scales (0-10) for
back and leg pain. A non-infected control group was identified
using propensity-matching techniques based on demographics,
baseline clinical outcome measures and surgical characteristics.
Two year postoperative outcome measures of both groups were
compared. The proportion of patients in each group achieving
the minimum clinically important difference (MCID) for the
outcome measures was also assessed. Independent t-tests were
used to compare continuous variables and Fisher’s exact test was
used to compare categorical variables between the two groups.
RESULTS: Consistent with the propensity-matching technique,
there were no significant demographic or surgical differences
between the two groups at baseline (Table 1). ODI, PCS, back
and leg pain scores were statistically significantly better at two
years post-operative compared to baseline in both groups.
However, at two years post-operative, the infection group had
statistically significantly worse back pain scores compared to the
control group (6.45 vs. 4.7, p=0.020). Also, a greater proportion
of patients in the control group (18, 60%) achieved MCID
for ODI compared to the infection group (8, 27%, p=0.018).
patients with acute postoperative deep wound infections following
instrumented lumbar spinal fusion have improved outcome
measures after surgery but have greater back pain and a decreased
probability of achieving MCID for ODI than patients without
infection two years following surgery.
NO INFECTION
INFECTION
p-value
N
30
30
Sex (male)
12
8
0.402
ALIF
2
2
1.000
TLIF
8
8
PSF
17
17
ASF/PSF
3
3
Smoker
6
8
Workers’’ comp
2
1
8
8
Surgery
0.761
Diagnosis
Spondylolisthesis
1013
1.000
Baseline
Two-Year Post-operative
Proportion achieving MCID
POSTER NO. P380
Sagittal Classification for Ossification of the
Ligamentum Flavum of the Thoracic Spine
Kei Ando, MD, Nagoya, Japan
Shiro Imagama, MD, Nagoya, Japan
Zenya Ito, PhD, Nagoya, Japan
Yukihiro Matsuyama, MD, Hamamatsu, Japan
Naoki Ishiguro, MD, Nagoya, Japan
INTRODUCTION: Thoracic myelopathy due to an ossified
ligamentum flavum (OLF) generally requires surgical
intervention due to its progressive nature and its poor response
to conservative therapy. The purpose of this study was to
provide the first evidence for the influence of ossified anterior
longitudinal ligament (OALL) on the clinical features and
surgical outcomes in thoracic ossified ligamentum flavum (OLF).
METHODS: Sixty-three patients who underwent surgery for a one
level thoracic OLF were identified, and preoperative symptoms,
severity of symptoms and myelopathy, disease duration, MR
imaging and CT findings, surgical procedure, intraoperative
findings, complications, and postoperative recovery were
investigated in these patients. Findings on sagittal CT images that
was adjacent to or at the same vertebral level were classified into
four types: No discernible type (Type N); One sided type (Type
O); Discontinuous (Type D); and continuous type (Type C).
RESULTS: The duration of symptoms was especially long in the Type
D and C OALLs. Patients with Type D had a significantly poorer
percentage of recovery, the same as their preoperative JOA scores.
DISCUSSION AND CONCLUSION: The authors’ results showed
that a Type D OALL had strong relationships with preoperative
severity of symptoms and surgical outcomes. These findings may
allow surgeons to determine the severity of preoperative symptoms
and the probable surgical outcomes from the OALL classifications.
Moreover, the surgery with instrumentation for Type D OALL may
have better surgical outcome.
POSTER NO. P381
uAre Pedicle Screw Constructs Really More Expensive
than Hybrid Constructs?
Le-qun Shan, MD, PhD, Xi’An, China
David L. Skaggs, MD, Los Angeles, CA
Christopher Lee, East Greenwich, RI
Karen Myung, MD, Los Angeles, CA
INTRODUCTION: The use of pedicle screws in the treatment of
scoliosis has been increasingly adopted, with most studies showing
greater correction of spinal deformity than hybrid constructs.
However, the increased implant expense of pedicle screws compared
to hybrid constructs are concerning. The hypothesis of this study
is that if revision surgery secondary to implant failure is taken into
account, the total expense of pedicle screw versus hybrid constructs
in the treatment of adolescent idiopathic scoliosis (AIS) is similar.
METHODS: A retrospective review of 872 consecutive cases
of AIS patients that underwent posterior fusion (PSF) with
hybrid instrumentation or pedicle screw instrumentation at a
single institution from December 1995 to 2009 was performed.
Inclusion criteria consisted of diagnosis of AIS, posterior spinal
fusion with segmental instrumentation, and a minimum
of two-year follow up. Patient demographics, radiographic
parameters, operative data, and comprehensive charges for
implant related revision operations were recorded. Revision
surgery for infection was not included in the financial analysis.
RESULTS: A total of 167 patients with an average age of 14 years
and 11 levels fused (6-15) met inclusion criteria. Mean major
curve correction was 72% in the pedicle screw group and 54% in
the hybrid group (p=0.00). There was no significant difference
in average preoperative major Cobb angle (p=0.09), operative
time (p=0.48), anesthesia time (p=0.82) and average days in
ICU (p=0.42) between the two groups. Among the 44 patients
treated with all pedicle screws there were no implant related
surgical revisions. Of the 123 patients in the hybrid group, there
were 29 revision surgeries in 21 patients for implant failure
(revision rate of 17%). We calculated the present day charges in
our institution for an 11 level fusion using titanium implants to
be $42,450 for the average pedicle screw construct and $26,064
for the average hybrid construct. The mean charges of revision
surgery totaled $1,639,910, or $13,333 on average for each patient
in the hybrid group including implant charges, professional
fees, and hospital charges. Though the charge of initial surgery
was roughly $16,400 less in the hybrid construct group, when
revision charges for implant failure were added in, average
estimated charges for the pedicle screw group at final follow up
was 7.2% higher than the hybrid group ($42,450 vs. $39,397).
DISCUSSION AND CONCLUSION: Patients with AIS undergoing
PSF with all pedicle screw constructs had a markedly lower
revision rate (0% vs. 17%) when compared to hybrid constructs,
but total charges were 7.2% higher. In order to judge if new
technology is worth increased initial expense, a financial analysis
of complications over time should be assessed. In our opinion, the
markedly decreased revision rate with all pedicle screw constructs
compared to hybrid constructs are worth a 7.2% increase in spinal
implant charges.
1014
POSTER NO. P382
uTwo Year Bone Morphogenetic Protein (BMP) Clinical
Effects after Lumbar Fusion in Degenerative Disc
Disease (DDD)
Evalina L Burger, MD, Aurora, CO
Vikas V. Patel, MD, Denver, CO
Andriy Noshchenko, MD, PhD, Aurora, CO
INTRODUCTION: Several prospective randomized controlled
clinical trials (RCT) have reported that bone morphogenetic
protein (BMP) significantly improves lumbar fusion clinical
outcomes and fusion rates at 12 months postoperative, particularly
in patients with spondylolisthesis. However, other relatively
small studies have reported higher complication rates after
BMP use. The purpose of the present meta-analysis study was to
evaluate the effects of BMP on long-term lumbar fusion clinical
outcomes in patients with degenerative disc disease (DDD).
METHODS: The Cochrane database of randomized controlled
trails (RCT), Cochrane Database of Systematic Reviews, PubMed,
Medline, Embase, ClinicalTrial.gov, and published reviews were
used to search for published studies that met our inclusion/
exclusion criteria. Inclusion criteria were: 1) age >18 years, 2)
lumbar DDD with or without: stenosis, 3) grade I-II degenerative
spondylolisthesis, disk herniation, and other disk pathology, 4)
follow up ≥ 24 month for clinical outcomes and fusion rate, 5) use
of Oswestry disability index (ODI), back and/or leg pain Visual
analog scale (VAS), and/or SF-36 questionnaire, 6) not less than two
year postoperative complication rate, 7) employment rate before
and two years after surgery, 8) published between 2000 and 2010,
9) English language, 10) level of evidence ≥5 by van Tulder’s scale
for RCT, and ≥7 by Cowley’s scale for cohort studies and case series.
Exclusion criteria: scoliosis, trauma, isthmic spondylolisthesis,
tumors, radiculopathy. A meta-analysis was performed to assess
pooled treatment effect size, heterogeneity, and the risk of
publication bias. The data were grouped by whether or not BMP was
used. Data pooling was performed by randomized effect model.
RESULTS: A total of 18 studies from seven countries met the
inclusion/exclusion criteria: 14 RCT, three cohort studies, and
one retrospective case series. Pooled data showed significant
improvements in disability, pain, and physical health status
after lumbar fusion regardless of whether or not BMP was used,
(Table). Fusion rates were relatively high and approximately
similar for both BMP and non-BMP groups. Employment rate
did not improve significantly after surgery in either group.
BMP was not associated with an increased complication rate.
The risk of publication bias was not significant (p<0.001).
DISCUSSION AND CONCLUSION: Fusion outcomes at 2448 months postoperative for lumbar DDD are not significantly
improved by the use of BMP. This result suggests that the potential
benefits of BMP are limited to the early stages of fusion.
POSTER NO. P383
Loss of Lordosis Following Cervical Laminoplasty
Samuel M. Davis, MD, Atlanta, GA
John J. Rhee, MD, Atlanta, GA
INTRODUCTION: Although laminoplasty is not commonly
associated with the severe postoperative kyphotic deformities
that may occur with multilevel laminectomy alone, changes in
sagittal alignment, including loss of lordosis, can occur. However,
this process has not been extensively studied in the literature. The
purpose of this study was to evaluate the loss of lordosis that occurs
after open door laminoplasty, its pattern, extent, and timecourse.
METHODS: Thirty-one patients with satisfactory neutral lateral
radiographs at preop, six weeks, three months, six months, and
one year were selected from a cohort of patients who underwent
open door cervical laminoplasty between 2007-2009 for cervical
spondylotic myelopathy. At surgery, C2 muscle attachments were
preserved and not detached whenever possible or reattached if
necessary during closure. All patients were encouraged to begin
active range of motion and extensor muscle strengthening
exercises as soon as tolerable postop and to continue them
throughout the postoperative course. Sagital cobb angles of
the instrumented cervical levels were determined. Forward
pitch (FP) was measured as the distance from a vertical plumb
line drawn from the center of the cortical ring of C2 to the
anteroinferior corner of the lowest instrumented vertebrae (Fig
1). The change from preoperative was calculated for all patients
at each time interval. Per convention, negative numbers were
used to denote lordosis, positive numbers to denote kyphosis.
RESULTS: On average, patients lost 6o of lordosis from preop (-9.6
o
) to one year postop (-3.6 o). The greatest loss of lordosis occurred
between preop to six weeks and averaged 11 oof loss. Between three
to six months, the loss of lordosis gradually improved compared to
six weeks, but the overall lordosis never returned to preoperative
levels. There was no significant difference in the amount of lordosis
lost among those with a preop Cobb > -10 o versus those with < -10 o
at one year (-6.5 o vs. -5.7 o , p=0.65). There was no difference in the
preoperative Cobb angle between those with lower versus higher
forward pitch (p=0.52). However, those with less forward pitch
(FP <1 cm; n=14) lost 4.5o of lordosis at one year, whereas those
with greater forward pitch (FP > 1cm; n=17) lost 7.3 o (p=0.072)
Preop
Cobb
6 wks
(change)
3 mo
(change)
6 mo
(change)
1 yr
(change)
All (n=31)
-9.6 o
+1.8 o (11.4
o)
-1.1 o
(8.5o)
-4.4 o (5.2
o)
-3.6 o (6.0
o)
Preop cobb >
-10 o (n=13)
-19.3 o
-8.6 o (10.7
o)
-12.5 o
(6.8 o)
-11.9 o
(7.4 o)
-12.8 o
(6.5 o)
Preop cobb <
-10 o (n=18)
-2.6 o
+9.1 o (11.7
o)
+10.4 o
(13 o)
+1.1 o
(3.7 o)
+3.0 o
(5.6 o)
FP < 1cm
(n=14)
-9.5 o
-1.2 o (8.3
o)
-5.4 o
(4.1 o)
-4.8o (4.7
o)
-5.0 o
(4.5 o)
FP > 1cm
(n=17)
-9.7 o
+4.6 o
(14.3 o)
+1.3o
(11 o)
-4.0o (5.7
o)
-2.5 o (7.2
o)
lordosis. These data provide potentially important considerations
in preoperative preparation and patient counseling of patients
requiring surgery for multilevel myelopathy.
POSTER NO. P384
ALTERNATE PAPER: SPINE III
The Relation Between Pulmonary Function and
Selection of Upper Instrumented Vertebra in AIS
John Schlechter, DO, Irvine, CA
INTRODUCTION: There seems to be increasing concern that a
more proximal extent of posterior thoracic spinal instrumentation
and fusion (PSF) reduces postoperative pulmonary function.
However, there are few reports to analyze the relation
between the selection of upper instrumented vertebra (UIV)
and pulmonary function in adolescent idiopathic scoliosis
(AIS). The objective of this study was to evaluate pulmonary
function to determine whether a more proximal UIV negatively
impacts pulmonary function in surgically treated AIS patients.
METHODS: Pulmonary function testing (PFT) and radiographic
examination of 154 patients with major thoracic AIS (Lenke type 1 to 4)
undergoing PSF without thoracoplasty were completed prospectively.
Patients were divided into groups based on UIV (T1 to T3 vs.
T4 to T5) and Lenke curve type (2 & 4 vs. 1 & 3) and analyzed
respectively. Demographic, radiographic measurements, and PFT
data from preoperative and two year time points were analyzed.
RESULTS: Patients with a structural upper thoracic curve (Lenke
2 and 4) had significantly lower preoperative PFT values than
those without a structural upper thoracic curve (Lenke 1 and 3).
Lenke 2 and 4 patients were also more likely to be fused proximally
(82% T1-T3) than those in the Lenke 1 and 3 group (42% T1-T3,
p<0.05). Pre-operatively, those with UIV from T1 to T3 had lower
PFT values than those with UIV from T4-T5; however, only %TLC
was statistically significant (p<0.05). Both UIV groups showed
significant increases in all absolute values (FVC, FEV1, TLC) at twoyear follow up (p<0.05), and the percent predicted values (%FVC,
%FEV1, %TLC) reMEd stable. DISCUSSION AND CONCLUSION:
Although patients with UIV: T1 - T3 showed slightly lower PFT
values compared with UIV: T4 - T5, the presence of a double
thoracic curve was the primary cause of PFT reduction in these
patients. Including the upper thoracic spine in the fusion had no
significant effect on pulmonary function two years after surgical
correction of AIS. In the AIS population, there does not appear to
be a pulmonary function consequence to fusing into the upper
thoracic spine.
DISCUSSION AND CONCLUSION: Patients lose on average 6 o of
lordosis at one year after open door cervical laminoplasty, with
the greatest loss occurring at six weeks postop and then partially
recovering over time. The changes at six weeks may reflect pain and
splinting, whereas those at one year may reflect chronic muscle
denervation or atrophy. There was no significant difference in loss
of lordosis at one year between those who had more or less than
-10o of preoperative lordosis. However, those with greater forward
pitch of more than 1 cm demonstrated greater ultimate loss of
1015
POSTER NO. P385
POSTER NO. P386
Anterior vs. Posterior Surgery for Lenke 5 Adolescent
Idiopathic Scoliosis: Clinical and Radiographic
Outcomes
Cervical Spine Disease in Surgeons Performing
Arthroscopy or Laparoscopy
Darren R. Lebl, MD, New York, NY
Behrooz A. Akbarnia, MD, La Jolla, CA
Jaspaul S. Gogia, MD, Fair Oaks, CA
J. I. Krajbich, MD, Portland, OR
Raymund Woo, MD, Orlando, FL
Mark D. Rahm, MD, Temple, TX
Akilah B. King, BA, New York, NY
Matthew E. Cunningham, MD, PhD, New York, NY
INTRODUCTION: Lenke 5 adolescent idiopathic scoliosis (AIS)
that fails conservative management has traditionally been treated
by anterior spinal fusion (ASF). Recent advances in segmental
instrumentation have made posterior spinal fusion (PSF) an
attractive alternative utilizing the more common posterior
approach. Our multicenter database review showed similar fusion
rates and curve correction for ASF and PSF at a minimum two-year
follow up. PSF was associated with shorter operative times and
improved lumbar lordosis. The traditional approach for Lenke 5 AIS
has been ASF. Advances in segmental instrumentation have made
PSF an alternative. The optimal approach has yet to be determined.
METHODS: A multicenter database was searched for Lenke 5 AIS
patients undergoing ASF or PSF with a minimum two-year follow up.
Clinical charts, operative records and radiographs were reviewed.
RESULTS: Lenke 5 AIS patients (n=34: 31F, 3M) at a mean follow
up of 44(+/-)4 months underwent ASF (n=25) with both large
diameter single rods (n=11), small diameter dual rods (n=14), or
PSF (n=9). Patients undergoing ASF were younger (ASF 14.3(+/).4yrs vs. PSF 15.8(+/-).3yrs) (p<.05) and had fewer motion
segments fused (ASF 3.9(+/-)0.1 levels vs. PSF 4.8(+/-)0.3 levels)
(p=.001). Hospital LOS was lower in the PSF than the ASF group
(ASF 7.1(+/-)0.3 days vs. PSF 6.0(+/-)0.6 days) but was not
significant (p=0.09). Operative times trended toward being longer
in the ASF (239(+/-)10 min) group compared to the PSF group
(199(+/-)24 min)(p=.07). There was no significant difference in
EBL (p=.37). Coronal curve correction was: thoracolumbar (ASF
75(+/-)2% vs. PSF 67(+/-)7%; p=.23) and thoracic (31(+/-)5% ASF
vs. 58(+/-)13%; PSF) (p=.08). There was no significant difference
in increase in lumbar lordosis between groups (PSF 14(+/-)11 deg
vs. ASF 1(+/-)2 deg) (p=.09). There was no difference in preop
(p=.73), postop (p=.13), and change in kyphosis (p=.78), preop
(p=.46), postop (p=.50), and change in SVA (p=.69). There was no
difference in LIV Tilt correction (p=.64), CSVL correction (p=.14),
and PJK increase (p=.77). SRS22 scores were similar between groups
and there were no nonunions at most recent follow up. One major
complication occurred in the PSF that required revision surgery.
DISCUSSION AND CONCLUSION: Both ASF and PSF remain
options for Lenke 5 AIS. Fusion rates, blood loss, and curve
correction were similar between groups. PSF patients trended
towards shorter operative times and hospital stays. Patients selected
for ASF were younger and had fewer motion segments fused than
PSF patients. ASF involves an extensive surgical approach; however
it allows fusion of fewer segments with similar curve correction.
The more familiar posterior approach for Lenke 5 AIS curves may
be a better option for shorter operative times and hospital lengths
of stay.
1016
Elizabeth P. Norheim, MD, Torrance, CA
Miwa Takayanagi, MS, Pasadena, CA
MaryHelen Black, MS, PhD, Pasadena, CA
Marc Safran, MD, Redwood City, CA
Ronald A. Navarro, MD, Rolling Hills, CA
INTRODUCTION: There appears to be anecdotal evidence
of increased neck problems among arthroscopists. Surgeons
who perform arthroscopy or laparoscopy typically carry out
these surgical techniques with the cervical spine extended.
This posture places strain on the cervical spine which may lead
to chronic neck pain and cervical radiculopathy/myelopathy.
METHODS: A questionnaire assessing neck pain (NP), spine
disease (SD), and radiculopathy/myelopathy (R/M) was
administered to surgeons performing endoscopy at Kaiser
Permanente Southern CA. The sample was comprised of 722
surgeons from the disciplines of orthopaedic surgery (n=163),
general surgery (n=173), obstetrics and gynecology (n=301), and
urology (n=85). We examined whether surgeons who routinely
perform arthroscopy and laparoscopy are at increased risk of neck
pain and cervical radiculopathy/myelopathy compared to their
colleagues without significant endoscopic experience. Among
surgeons with endoscopic experience, we explored demographic
and clinical risk factor associations with NP, SD and R/M.
RESULTS: A total of 392 (54%) surgeons completed the
questionnaire. The majority of participants were over 40 years
of age (74%); 260 (66%) male and 132 (34%) female. A total of
361 (92%) had experience in endoscopy, of which 211 (58%)
reported having ever had NP, 75 (21%) had SD, and 25 (7%)
had R/M. The prevalence of current neck pain was 26.7% in this
surgeon population, which was significantly higher than the
4.4% reported in recent a U.S.-based general population study
(p<0.0001) [Strine 2007]. Female sex [Odds Ratio (OR) 1.62; 95%
CI: 1.02, 2.59] and elevated job stress level [OR 1.39; 95% CI: 1.10,
1.76] were significantly associated with NP, while moderate [OR
0.87; 95% CI: 0.77, 0.98] and vigorous [0.89; 95% CI: 0.79,1.00]
physical activity had a protective effect. Increasing age [OR 1.40;
95% CI: 1.09, 1.81] and elevated job stress level [OR 1.38; 95%
CI: 1.04, 1.84] were associated with SD. Increasing age was also
associated with R/M [OR 1.59; 95% CI: 1.06, 2.39]. After adjusting
for demographic and clinical covariates, there was a marginally
significant association between number of years of endoscopic
experience and SD (p=0.07***). In adjusted models, surgeons
who used a digital operating room for > 4 years were less likely
to have R/M compared to those who used < 4 years (p=0.06**).
No significant associations were observed between increasing
endoscopy experience and NP after adjusting for covariates.
DISCUSSION AND CONCLUSION: The point prevalence of neck
pain in our surgeon population was significantly higher than
a U.S. based general population study. Surgeons with greater
endoscopy experience were more likely to have spine disease,
while those with > 4 years of using a boom monitor were less likely
to have radiculopathy/myelopathy. Increasing age, female sex, and
elevated stress level significantly increased risk for these outcomes,
whereas physical activity had protective effect.
Table 2: Adjusted Odds Ratio for factors that are related to each
outcome in Table 1
Neck Pain
vs. No Pain
Among endo
(211 vs.
surgeons
135) Mean
(n=361):
(SD) or
Risk Factors
Number (%)
of Pain
Duration,
years
17.1 (9.36)
(continuous)
% of
surgeries
with
Endoscopy, 4.1 (2.89)
10%
increment
(continuous)
Frequency/
week
3.2 (3.28)
(continuous)
Digital OR
user (Boom
85 (63%)
monitor): No
(reference)
Digital OR
user (Boom 107 (60.1%)
monitor): Yes
Years of
digital OR
use: 3 or
48 (64%)
less years
(reference)
Years of
digital OR
58 (57.4%)
use: 4 or
more years
Neck Pain
vs. No
Pain (211
vs. 135)
Odds Ratio
(95% CI)
Spine
Disease vs.
No SD (75
vs. 286)
Mean (SD)
or Number
(%) of SD
1.01
(0.99,
1.04)
1.03 (1.00,
20.5 (8.82)
21.0 (8.81)
1.07)***
Spine
Disease
vs. No SD
(75 vs.
286) Odds
Ratio
(95% CI)
Radiculopathy/
Myelopathy vs.
No RP/MP (25
vs. 314) Mean
(SD) or Number
(%) of R/M
Radiculopathy/
Myelopathy vs.
No RP/MP
(25 vs. 314)
Odds Ratio
(95% CI)
1.01 (0.96,
1.07)
Age, less
than 30,
10 year
Mode=41increment, 50
greater than
70
Gender:
129 (57.1%)
Male
4.0 (2.88)
1.01
(0.93,
1.10)
3.1 (3.49)
1
20 (26.3%) 1
0.98
(0.57,
1.67)
45 (24.9%)
1
20 (26.3%) 1
0.70
(0.34,
1.44)
25 (24.5%)
0.98
(0.90,
1.08)
4.8 (2.44)
0.97 (0.89,
2.9 (3.32)
1.06)
9 (12%)
1.30 (0.74,
14 (8%)
2.27)
9 (12%)
0.79 (0.39,
5 (5.1%)
1.62)
1.09 (0.93,
1.27)
0.99 (0.85,
1.15)
1
0.88 (0.37,
2.10)
1
0.32 (0.10,
1.07)**
Pain vs.
No Pain
Odds
Ratio
(95% CI)
Spine
Disease vs.
No SD
Mean (sd) or
Frequency
(%)
Spine
Disease
vs. No SD
Odds
Ratio
(95% CI)
Radiculopathy/
Myelopathy vs.
No RP/MP
Mean (sd) or
Frequency (%)
Radiculopathy/
Myelopathy vs.
No RP/MP
Odds Ratio
(95% CI)
0.97
(0.77,
1.21)
Mode=4150
1.40
(1.09,
1.81)*
Mode=41-50
1.59 (1.06,
2.39)*
1
46 (19.4%)
1
12 (5.5%)
1
13 (10.9%)
2.13 (0.94,
4.82)***
3.6 (0.96)
1.31 (0.84,
2.04)
1.62
Gender:
82 (68.3%) (1.02,
Female
2.59)*
Stress On
1.39
Job: Scale 1 3.5 (0.97) (1.10,
to 5 (trend)
1.76)*
Physical
Activity:
0.99
Days/wk
3.6 (2.47) (0.88,
with Mild
1.10)
activity (1
to 7)
Physical
Activity:
0.87
Days with
2.6 (1.87)
(0.77,
Moderate
0.98)*
activity (1
to 7)
1017
2.2 (2.01)
0.89
(0.79,
1.00)
112 (39.9%) 1
0.83
Smoking:
16 (44.4%) (0.41,
Ever/Current
1.67)
2.7 (2.13)
1.08
(0.94,
1.24)
61 (21.6%) 1
7 (18.9%)
0.85
(0.35,
2.02)
1.8 (1.94)
0.85 (0.65,
1.11)
264 (93.6%)
1
33 (89.2%)
1.78 (0.57,
5.57)
POSTER NO. P387
1.01
(0.92,
1.10)
Table 1: Univariate analysis of risk factors associated with outcomes
Pain vs. No
Among endo
Pain
surgeons
Mean (sd) or
(n=361):
Frequency
Risk Factors
(%)
Physical
Activity:
Days with
Strenuous
activity (1
to 7)
Smoking:
Never
(reference)
1.27
29 (23.4%) (0.75,
2.14)
1.38
3.6 (1.00)
(1.04,
1.84)*
3.7 (2.35)
1.00
(0.88,
1.14)
2.9 (2.11)
0.87 (0.70,
1.08)
3.2 (1.89)
1.12
(0.97,
1.30)
3.1 (2.02)
1.07 (0.86,
1.33)
Anterior L5-S1 Fusion Does Not Improve Sagittal
Alignment Following Pedicle Subtraction Osteotomy
Munish C. Gupta, MD, Sacramento, CA
Eric O. Klineberg, MD, Sacramento, CA
Kirkham B. Wood, MD, Boston, MA
Behrooz A. Akbarnia, MD, La Jolla, CA
INTRODUCTION: Lumbar pedicle subtraction osteotomy (LPSO)
improves lumbar lordosis (LL), sagittal vertical axis (SVA), and spinopelvic alignment (SPA). Reports have indicated that interbody fusion
at the L5-S1 improves arthrodesis rates at the lumbosacral junction;
however, the contribution of L5-S1 interbody procedure toward
sagittal alignment correction when performing LPSO is unknown.
METHODS: Multi-center, retrospective, radiographic analysis
of adult spinal deformity (ASD) patients undergoing LPSO with
fusion to the sacro-pelvis for sagittal spinal malalignment (SSM)
using a prospective collected database. Inclusion criteria: age >18
years, pre and postoperative spine radiographs permitting spinopelvic parameter measurement. Exclusion criteria: post-traumatic,
infectious, neuromuscular or tumor associated spinal deformities.
Patients evaluated according to type of interbody fusion performed
at L5-S1 (anterior approach= ALIF, posterior approach=T/PLIF,
no interbody= NONE). ALIF patients divided into timing of the
ALIF procedure: prior to (ALIFpre) or after (ALIFpost) the LPSO
procedure. Radiographic analysis included coronal and sagittal
spino-pelvic parameters and degree of focal PSO correction.
RESULTS: A total of 105 patients were treated with LPSO with
fusion to the sacro-pelvis, of which 77 patients met inclusion
criteria. Interbody procedures included: NONE, n=32; T/PLIF,
n=15; ALIFpre, n=19; ALIFpost, n=11. Mean preoperative
radiographic parameters, correction of and postoperative values
for SVA, L5-S1 angle, lumbar lordosis and PSO angle were similar
for all treatment groups (ANOVA<0.05). T/PILF had greater
postoperative pelvic tilt (PT) than ALIFpost (29.4° vs. 17.1° and
p=0.014), however PT correction was similar for all groups.
DISCUSSION AND CONCLUSION: Anterior interbody graft at
L5-S1 has been reported to enhance fusion rates at the lumbosacral
junction despite higher reported complication rates. There was,
however, no added benefit of ALIF vs. TLIF with respect to sagittal
SPA correction when performing LPSO and fusion to the sacropelvis. Further research is needed to evaluate long-term outcomes
to determine the ideal interbody approach at L5-S1 when
performing LPSO.
postop measures of T1 tilt or SHD. Increased changes in CA were
seen in Group 1. This study indicates that there is no benefit to
incorporating the PT curve in the surgical Lenke 1 AIS patients.
This can potentially avoid the increased implant cost, neurologic
risk, and operative time required to extend instrumentation
proximally.
POSTER NO. P389
Anatomy of Lamina in the Thoracolumbar Spine with
the Special Reference to Translaminar Screws
POSTER NO. P388
Lenke 1 AIS Curves: Where to Stop and How does it
Affect Shoulder Balance? Selective vs Non-Selective
Thoracic Fusions
Jaspaul S. Gogia, MD, Fair Oaks, CA
Akilah B. King, BA, New York, NY
Matthew E. Cunningham, MD, PhD, New York, NY
John S. Blanco, MD, Pelham, NY
Roger F. Widmann, MD, New York, NY
INTRODUCTION: A retrospective radiographic evaluation of Lenke
1 adolescent idiopathic scoliosis (AIS) patients treated with fusion
and pedicle screw fixation demonstrated no differences in proximal
thoracic (PT) curve correction or shoulder symmetry when the
fusion did not include the flexible non-structural proximal thoracic
curve. Instrumentation of proximal thoracic curves in the treatment
of Lenke 1 AIS patients may not be indicated. Shoulder symmetry
is an important factor to consider in surgery for AIS. Many surgeons
currently fuse flexible PT curves in an effort to obtain improve
shoulder balance. This study investigated the need to include or
exclude the PT curve in Lenke 1 patients with the hypothesis that
no difference would be present with respect to shoulder symmetry.
METHODS: A retrospective review of 148 consecutive AIS patients
treated with fusion was performed. Twenty-two patients met
inclusion criteria of Lenke 1 curve type, posterior pedicle screw
fixation, and two-year follow up (f/u). The 22 patients were divided
into two groups: Group 1 (n=9) included those who were fused to
the upper end vertebra or one level higher. Group 2 (n=13) included
those fused two or three levels proximal to the upper end vertebra.
Radiographic measurements including PT, main thoracic (MT),
T1 tilt, clavicle angle (CA) and shoulder height difference (SHD)
were performed for each patient at preop, six week and final f/u.
RESULTS: The average age in both groups was 14 years (10-17yrs).
The avg f/u in Group 1 was 28 mos (24-36mos) and 30 mos (2447mos) in Group 2. There was no difference between the two groups
in preop angles for MT (p=0.77), T1 tilt (p=0.25), CA (p=0.54),
and SHD (p=0.22). Preop PT curves averaged 19.6 deg (12-28deg)
in Group 1 and 28.3 deg (14-41deg) in Group 2 (p=0.02). Preop
PT curve flexibility averaged 35% (range 21-61) in Group 1 and
50% (range 14-73) in Group 2 (p=0.04). Postop, no significant
differences were seen in PT (p=0.21) or MT (p=0.06) curve
correction or changes in T1 tilt (p=0.44) or SHD (p=0.19). Changes
in CA averaged 4.1 deg in Group 1 and 2.1 deg in Group 2 (p=0.02).
DISCUSSION AND CONCLUSION: While Group 2 had larger
preop PT curves, these curves were also much more flexible. No
significant differences were seen in either group with respect to
1018
INTRODUCTION: The original development of translaminar
screws was for fixation of C2. Over the years, the use of
translaminar screws has grown to almost all parts of the spine,
including the subaxial cervical, thoracic, and lumbar spine.
In terms of examining the specific anatomy important for
thoracic and lumbar spine insertion of translaminar screws,
to our understanding, there has not been a study to do so.
METHODS: T1 to L5 were harvested from 17 cadaveric spines
and 3D reconstructions were acquired using 1-mm CT scans.
One manufacturer’s platform was used to simulate translaminar
screw insertion points and trajectories bilaterally from T1 to
L5. These translaminar screw simulations were created with the
goal of obtaining optimal bony purchase with the first screw (1°
screw) and the best allowable diameter with the second screw
(2° screw) taking into account the trajectory of the 1° screw. For
the 2° screw, it was important to prevent cortical breakage even
if the theoretical best diameter for purchase was not obtained.
Figure shows the screws’ simulated trajectories. A previous study
(Xu et al. Spine 1999) was used as a reference for the diameter of
the simulated translaminar screws to be utilized. For T1-6, L1-2,
the screw diameters selected were 4mm; however, for T7-12, L35, a 3.5mm diameter screw was utilized instead. The length of
the midlaminar line was measured, and the diameter of the 1°
screw was subtracted from it to determine if the same screw size
could be used as the 2° screw. From the CT 3D reconstructions,
anatomical measurements were made based on the simulated 1°
and 2° screw trajectories. These measurements included the screw
length, vertical angle, horizontal angle, thickness of the narrowest
section of lamina, and the cancellous and cortical thickness of that
thinnest lamina section. From the individually sectioned cadaveric
thoracolumbar spine segments (11 out of 17), caliper measurements
were obtained that mirrored those from CT, nevertheless, the 3D
characteristics of the specimens limited the ability to acquire the
measurements of the exact same portions that were done on CT.
RESULTS: There were no specimens that did not allow the use of
the same size 2° screw as was used for the 1° screw. The lengths
and the angles of the 1° and the 2° screws are illustrated in Table.
DISCUSSION AND CONCLUSION: This study represents a
description of the lamina anatomy in the thoracolumbar spine in
terms of translaminar screws. This special reference to translaminar
screws in the thoracolumbar spine takes into account the simulated
trajectories of 1° and 2° screws using cadaveric and CT analysis.
Future studies into the indications for clinical use and effectiveness
of inserting translaminar screws into actual thoracolumbar spines
would be valuable.
POSTER NO. P390
A Retrospective Review of Cases of Osteomyelitis of
the Cervical Spine Requiring Surgical Intervention
Drew Lansdown, MD, San Francisco, CA
Robert McClellan, MD, San Francisco, CA
Christopher Ames, MD, San Francisco, CA
Dean Chou, MD, San Francisco, CA
Vedat Deviren, MD, San Francisco, CA
INTRODUCTION: Osteomyelitis of the spine is a condition
that must be diagnosed quickly and treated appropriately, as the
potential consequences can be devastating. The cervical spine
is the least likely region in the spine to have an infection. This
disease has not been well documented in the literature, and it
is important for clinicians to understand the salient features
so these patients can receive treatment in a timely fashion. The
purpose of this study is to evaluate patients with osteomyelitis of
the cervical spine that had surgical treatment in two institutions.
METHODS: Following an Institutional Review Board approval, a
retrospective database review was performed in two institutions
from January 2000 to November 2010. The inclusion criteria
were age>18, surgical treatment for primary osteomyelitis of
the cervical spine. A chart review was performed to document
demographic characteristics; medical comorbidities, initial
presentation, infectious organism, surgical procedure, postoperative
antibiotics,
perioperative
complications
and
neurological function on follow up were recorded. A radiographic
review was performed to assess initial presentation, levels
involved and for any signs of loosening or failure on follow up.
RESULTS: A total of 21 cases (17 male, four female) of osteomyelitis
of the cervical spine that were treated surgically were identified.
The average age of affected patients was 48 years (range 20-81).
The most frequent presenting symptom was a neurological deficit
(12/21). Pain was also frequently documented on presentation
(9/21), and bacteremia (4/21), chronic infection (3/21) or
structural changes (2/21) were other symptoms on presentation.
The infection was attributed to IV drug abuse in nine patients.
Four patients had known HIV. On average, there was involvement
of 2.4 vertebral bodies (range 1-4), and the most commonly
affected vertebral segment was C6, seen in 19/21 cases. The
majority of patients underwent anterior and posterior procedures
(15/21) with instrumentation. Surgical complications included
an epidural hematoma in two patients and a wound infection in
one patient. Four patients developed pneumonia post-operatively.
Staphylococcus aureus was the most frequently implicated
primary organism, seen in 12 cases, with six cases of MRSA, six
cases of MSSA. Two patients had a polymicrobial infection, and
both had a concomitant fungal infection. All patients received
long-term IV antibiotics following surgical intervention. Clinical
follow up was available for an average of 17.0 months (1-38
months). Of 11 patients with preoperative neurologic deficit, nine
had persistent neurologic dysfunction at the final follow up. Two
patients died during the follow-up period from unrelated causes.
DISCUSSION AND CONCLUSION: Osteomyelitis of the cervical
spine is a rare condition that often presents with a neurological
deficit, and despite surgical intervention majority of the patients
are left with residual neurologic dysfunction. Therefore, timely
surgical intervention is vital in management of these patients. This
study also showed that despite significant comorbidities, aggressive
debridement with circumferential instrumented fusion provided a
high rate of union without an increased morbidity secondary to
using implants in an infected surgical field.
1019
POSTER NO. P391
Can Monitoring Spinal Cord Blood Flow Identify Preinjury State During Surgery?
Seth Grossman, MD, Bronx, NY
Farzin Kabaei, MD, Los Angeles, CA
Etan Sugarman, MD, Bronx, NY
Chistian E. Keller, MD, Bronx, NY
Alan Legatt, MD, PhD, Bronx, NY
INTRODUCTION: Spinal cord injuries during spinal surgery most
commonly occur during cord manipulation or from iatrogenic
compression due to misplaced hardware. Ischemia and reperfusion
of the spinal cord play a significant role in both pathogenesis and
functional outcome. Measuring spinal cord blood flow in real
time may detect impending spinal cord injury. The objective of
this study was to determine the effect of compressive spinal cord
injury on spinal cord blood flow and to correlate circulatory
disturbances with trans-cranial motor evoked potential signals.
METHODS: Seven farm-raised pigs were studied. An inflatable,
balloon catheter with pressure monitor was used in the midthoracic spine to apply gradual compression to the spinal cord. Dual
channel LASER doppler leads were placed posteriorly and laterally
on the dura, immediately caudal to the level of compression. The
balloon was inflated in 0.55 cc increments at five-minute intervals
until MEPs decreased to less than 90%. Continuous TcMEP,
SCBF, and ABP monitoring was carried out. Thirty minutes after
the MEP changes were seen, a wake-up test was performed, the
animal was sacrificed, and a spinal cord biopsy was obtained.
RESULTS: Two animals died during intubation. Between 6 to 9
psi, a 30% increase in the spinal cord blood flow was seen on the
posterior leads while MEP reMEd at baseline. Significant decrease
in MEPs occurred around 11 psi and corresponded to a 50%
decrease in spinal cord blood flow on both posterior and lateral
leads. MEPs did not return and the wake-up test was unsuccessful
in all five pigs. Spinal cord histopathology showed eosinophillic
infiltrates and microhemorrhages consistent with acute ischemia.
DISCUSSION AND CONCLUSION: Real time SCBF measurement
corresponds well with changes in MEPs. In the presence of cord
compression, the LASER Doppler can detect spinal cord injury
earlier than MEPs. This pre-injury, hyperemic state can provide
the operating surgeon with an opportunity to intervene before
complete spinal cord injury occurs. Significance: Real time SCBF
monitoring with LASER doppler allows for detection of a preinjury state. Awareness of this time period has the potential to
significantly impact the safety of complex spine surgery.
POSTER NO. P392
The Anchor Type in Spinal Deformity Surgery
Significantly Impact the Incidence of Proximal
Junctional Kyphosis
Richard L. Skolansky, Jr, Prof., Baltimore, MD
INTRODUCTION: Proximal junctional kyphosis (PJK) develops
as a result of stresses on the proximal mobile segment by the stiff
instrumented vertebrae; ligamentous disruption and fractures are
1020
among the factors implicated. We hypothesize that using transverse
process hooks (TPH) as an anchor at the most cephalad vertebra
lowers the incidence of PJK compared to pedicle screws (PS).
METHODS: We prospectively collected and retrospectively
reviewed clinical and radiographic data and functional outcome of
52 consecutive patients who underwent long posterior spinal fusion
using TPH or PS at the UIV between 2004 -09. We compared the results
of TPH vs. PS at the UIV. PJK was defined as sagittal Cobb angle ≥10°
between the lower endplate of UIV and the upper endplate of the
two superior vertebrae and ≥10° increase from prior measurement.
RESULTS: Forty-seven patients completed two years follow up, 20
had TPH at the UIV (group I) average age 45 ys (22-78) (17F, 3M).
Twenty-seven (22F, 5M) had PS at the UIV (group II) age 57 years
(20-78) . There were 13 levels fused in group I and group II (9-17) and
(9-18) respectively. Pre- and post-op radiographic characteristics
were similar in both groups (Table 1). Comparing post-op to final
follow up, 0/20 (0%) of patients in TPH group compared to 8/27
(29.6%) of PS group developed PJK (p=0.023). Comparing pre-op
and final follow up, 2/22 (9.1%) in TPH group and 13/27 (48.1%)
in PS group developed PJK (p=0.008). Of the eight patients in
PS group who developed PJK, three required additional surgery.
Complication rate was higher in group II than group I; five major
and 13 minor vs. nine major and 13 minor respectively. The SRS-24
and ODI at final follow up were significantly better in the TP hook
group compared to those in the pedicle screw group (Table 2).
DISCUSSION AND CONCLUSION: The use of TP hooks at UIV in
long spinal fusion appears to reduce the risk of PJK. Several reasons
may contribute to that; the surgical approach for TPH placement is
less extensive, preserving the soft tissues and joint capsule, TPHs
provide a less rigid proximal segment, exerting less mechanical
stress on the level above. TPH do not weaken the anterior vertebral
body potentially preventing compression fracture at UIV. TP
hooks should be strongly considered in the choice of the posterior
anchors at the UIV in long spinal fusions to the upper thoracic
spine in adult deformity surgery.
POSTER NO. P393
Protective Changes in Lumbar Anatomy Occur with Age
in Adulthood: An Anatomic Study of 1,072 Cadaveric
Specimens
INTRODUCTION: Prior studies have demonstrated that changes
in lumbar vertebral parameters such as vertebral body diameter
(VBD), sagittal diameter and interpedicular distance (IPD) occur
with age. However, most of these prior anatomic studies have
studied the alterations which occur with growth in the pediatric
population. However no studies have studied the changes in
lumbar morphology which occur in adult specimens with age. This
study was performed to determine changes in lumbar morphology
which occur with age, and to determine if these changes may have
an impact on development of lumbar stenosis with advancing age.
METHODS: A total of 1,072 cadaveric specimens from HamannTodd Osteological Collection in Cleveland, OH were examined
by a single examiner. Baseline data including age, sex, and race of
subjects were collected. The lumbar vertebrae (L1-L5) were measured
subjectively with digital caliper. The vertebral body diameter (VBD)
was measured as the anteroposterior distance of each vertebral
body, while the interpedicular distance (IPD) was measured from
the superior aspect as the minimum distance between the medial
aspects of the pedicles on either side. Linear regression analyses
were then used to determine the relationship between vertebral
body diameter (VBD) and age, and interpedicular distance (IPD)
and age, correcting for confounding factors of sex and race.
RESULTS: A significant positive association was found between
VBD and age at all lumbar levels L1-L5 (p<0.02). A significant
positive association was found between IPD and age at lumbar
levels L1, L2, and L3 (p<0.02). The average body diameter for
specimens over 50 years of age was 34.2 mm as compared to
32.5 mm for specimens under the age of 50, while the average
interpedicular distance for specimens over 50 years of age was 34.2
mm, compared to 32.5 mm for specimens under the age of 50.
VBD and IPD increase with age. The axial stresses which occur over
the course of years may cause the vertebral bodies to expand with
age. However, while VBD increases with age at all lumbar levels,
the IPD only increases with age in the upper lumbar spine. The
lumbar spine is more lordotic at L4 and L5, and as a result the axial
stress on the lower lumbar levels is more anteriorly located. This
would place the axis of the stress away from the posterior half of
the vertebral bodies, which is where the pedicles are located, and
may explain why the IPD does not increase with age at these levels.
Alternately, the L1, L2, and L3 vertebrae are not lordotic in position,
and the axial forces exerted across these levels may be more evenly
distributed, causing the IPD at the upper lumbar levels to expand
with age. This expansion of the IPD in the upper lumbar spine may
protect the aging individual from stenosis at these levels. The fact
that the canal widens in the upper lumbar spine with age, while
it does not in the lower lumbar spine may explain, in part, why
lumbar stenosis occurs so frequently at the lower lumbar levels
while it is relatively uncommon in the upper lumbar spine.
POSTER NO. P394
Spinal Deformity Correction in Marfan Syndrome
versus Adolescent Idiopathic Scoliosis
Joseph P. Gjolaj, MD, Miami, FL
Paul D. Sponseller, MD, Baltimore, MD
Jack M. Flynn, MD, Philadelphia, PA
Michelle MAK, NMD, Tucson, AZ
Philip R. Neubauer, MD, White Hall, MD
INTRODUCTION:
Patients
with
Marfan
syndrome
commonly require spinal deformity surgery, but practice
guidelines and results are not as established as those
for patients with adolescent idiopathic scoliosis (AIS).
METHODS: We matched 34 adolescents with Marfan syndrome 1:2
with AIS patients for age, gender, and degree of major deformity. Mean
age was 14 ± 2 years. Mean curves were 51° thoracic and 46° lumbar
for both groups. Mean follow up was 5.3 and 3. 6 years, respectively.
RESULTS: The Marfan group had significantly more thoracolumbar
1021
kyphosis correction (9.5° vs. 0.1°, P = 0.05), significantly more
levels fused (12 ± 2 vs. 9 ± 3, P = 0.01), significantly more
fusions to the pelvis (6 vs. 0, P = 0.01), and significantly more
correction of preoperative sagittal imbalance (2.4 vs. -0.6 cm,
P = 0.035) than did the AIS group. The Marfan group also had
more intraoperative cerebrospinal fluid leaks (3 vs. 0, P = 0.01),
more instrumentation complications (3 vs. 1, P = 0.007), more
reoperations for indications such as fixation failure, spine fracture,
curve decompensation, add-on deformity, distal degeneration
and pseudoarthrosis (8 vs. 0, P = 0.01) and lower SRS-22 total
(3.9 vs. 4.5, P = 0.01) and partial (P < 0.015) subscores. There
were no significant differences between the groups in progression
of unfused proximal thoracic curves, blood loss, neurologic
deficit, hospital stay, percent correction, or infection rate.
DISCUSSION AND CONCLUSION: Marfan patients differ in
several ways from those with AIS: they require more levels of
surgical correction, more distal fusion, greater correction of
sagittal balance, more reoperations, and have more intraoperative
CSF leaks and instrumentation-related complications. Knowledge
of these differences is important for successful surgery planning.
POSTER NO. P395
ALTERNATE PAPER: SPINE II
Preoperative Methicillin-resistant Staphylococcus
aureus (MRSA) Screening and Treatment in Elective
Spine Cases
Antonia Chen, MD, Pittsburgh, PA
Srinivas Chivukula, BS, Pittsburgh, PA
Lloydine Jacobs, MD, Pittsburgh, PA
Matthew Tetreault, BA, Chicago, IL
Joon Y. Lee, MD, Pittsburgh, PA
INTRODUCTION: The prevalence of methicillin-resistant
Staphylococcus aureus (MRSA) is increasing. Screening for MRSA
and treating MRSA colonized patients with intranasal mupirocin
and topical chlorhexidine has been shown to be effective for
reducing surgical site infections (SSIs) in arthroplasty patients.
However, there have been no studies conducted characterizing
the rates of MRSA colonization among spine surgery patients.
The purposes of this study was to determine the incidence
of MRSA colonization in an elective spine population and
to evaluate if MRSA screening and treatment reduced SSIs.
METHODS: A retrospective analysis of 1,160 consecutive elective
spine patients was conducted in 2010. Thirty-three were lost to
follow up, and 578 were screened for MRSA and 549 were not.
For those patients who underwent screening, a pre-operative
treatment protocol with muprocin and cholorohexidine was
performed if they were colonized with MRSA. A SSI was defined
as an infection that was irrigated and debrided in the operating
room. Data was collected for patient demographics (age, gender,
BMI), surgical data (location of surgery, primary versus revision
surgery, instrumentation, harvesting of autologous iliac crest bone
graft - ICBG), and clinical data (follow up, SSI, cultures). Statistical
analysis of continuous variables was performed by Mann-Whitney
U tests and nominal variables were analyzed by chi-squared
tests. Statistical significance was defined as a p-value <0.05.
RESULTS: In the study population, there were 570 males (50.6%)
and 557 females (49.4%). The average age was 54.2 years±17.2 and
average BMI was 29.8 kg/m2±6.3. Surgery was performed in the
cervical (398, 35.3%), thoracic (26, 2.3%) and lumbar (703, 62.4%)
regions. There were 840 (74.5%) primary and 287 (25.5%) revision
surgeries. Instrumentation was used in 849 (75.3%) cases and
ICBG was taken in 773 (68.6%). The average follow up was 171.7
days (3-481). Patients who were screened for MRSA had similar
demographics compared to the group not screened for MRSA (see
Table 1). Of the patients screened for MRSA, 16/578 (2.8%) tested
MRSA positive. There were 36 SSIs for the entire study population
(3.1%), with 25 (2.2%) from the surgical site, nine (0.8%) from
the ICBG, and two (0.2%) from both. The rates of SSIs were similar
for patients who were screened then pre-treated for MRSA (18/578,
3.1%) compared to those who were not (18/549, 3.3%) (p=0.874).
DISCUSSION AND CONCLUSION: The colonization rate for
MRSA in an elective spine population has not yet been determined.
The results of our study indicate that 2.8% of elective spine
patients in our population were colonized with MRSA. This rate
is comparable to orthopaedic arthroplasty literature. Although
MRSA decolonization has been shown to reduce SSIs, our study
did not demonstrate this finding. Although patients were provided
prescriptions for mupirocin and chlorhexidine, there was no
method of measuring compliance with treatment. Further studies
must be conducted to evaluate the screening of both MRSA and
methicillin-sensitive Staphylococcus aureus (MSSA) to determine
if treatment can reduce the rate of SSIs.
treatment for adult spinal deformity (ASD). Inclusion criteria: age
>18 years and radiographic diagnosis of ASD (scoliosis >20°, or SVA
> 5cm, or pelvic tilt > 25°, or thoracic kyphosis > 60°). Radiographic
evaluation: frontal and lateral spino-pelvic measurements.
HRQOL questionnaires: Oswestry Disability Index (ODI),
Scoliosis Research Society Questionnaire (SRS-22r). Radiographic
parameters were correlated with HRQOL values. Radiographic
parameters demonstrating highest correlation with HRQOL values
were evaluated to determine a disability threshold of ODI≥40.
RESULTS: Between 10/2008 to 12/2010, 492 consecutive ASD
patients (mean age 51.9 years, SD 16.8) were enrolled. Patients
treated OP (n=178) were older (55 vs. 50.1 years, p<0.05), had
greater SVA (5.5 vs. 1.7cm, p<0.05), greater pelvic tilt (PT; 22°
vs. 11°, p<0.05) and greater pelvic incidence/ lumbar lordosis
mismatch (PI-LL; 12.2 vs. 4.3; p<0.05) than NON (n=314). OP
demonstrated greater disability on all HRQOL measures compared
to NON (ODI =41.4 vs. 23.9, p<0.05; SRS total=2.9 vs. 3.5, p<0.05).
Pearson analysis demonstrated PT, SVA, and PI-LL correlated
most strongly with disability for both OP and NON patients
(p<0.001). Linear regression models demonstrated threshold
radiographic spino-pelvic parameters for ODI≥40 included:
PT≥22° (r=0.38), SVA ≥46 mm (r=0.47), PI-LL≥11 (r=0.45).
DISCUSSION AND CONCLUSION: SSM is a disabling condition.
Prospective analysis of consecutively enrolled ASD patients
demonstrated PT and PI-LL combined with SVA predict patient
disability and provide a guide for patient assessment. Threshold
values for severe disability included: PT≥22°, SVA ≥46mm, and PILL≥11°.
POSTER NO. P397
Asymmetric Pedicle Subtraction Osteotomy: A Useful
Tool for Severe Scoliotic Deformities
POSTER NO. P396
Pelvic Tilt, Pelvic Incidence/Lumbar Lordosis Mismatch
and Sagittal Alignment Predict Spinal Disability
Richard A. Hostin, MD, Plano, TX
Douglas C. Burton, MD, Kansas City, KS
Robert A. Hart, MD, Portland, OR
INTRODUCTION: Sagittal spinal malalignment (SSM) is
commonly defined by increased sagittal vertical axis (SVA), however,
SVA alone may underestimate the severity of SSM. Spino-pelvic
parameters provide a more complete assessment of SSM. Little data
has correlated spino-pelvic parameters with disability. The purpose
of this study is to evaluate correlations between sagittal spino-pelvic
parameters and health related quality of life (HRQOL) scores.
METHODS: Demographic, radiographic, and HRQOL data were
obtained from patients consecutively enrolled into a multi-center,
prospective study evaluating operative (OP) vs. nonoperative (NON)
1022
Mohammad M. El-Sharkawi, MD, Assiut, Egypt
Wael Koptan, MD, Cairo, Egypt
Yasser H. El Miligui, MD, FRCS, Cairo, Egypt
INTRODUCTION: Different spinal osteotomies have been
described to improve the correction power and to eliminate the need
for anterior release, application of traction as well as staged surgeries
in severe spinal deformities. Pedicle subtraction osteotomy (PSO)
has been extensively applied for correcting kyphosis of various
etiologies. However, the use of asymmetric PSO for correcting
coronal plane deformities has been inadequately reported in the
literature. The aim of this work is therefore to study the outcome and
safety of using asymmetric PSO in treating severe scoliotic deformity.
METHODS: Twenty-two patients (14 females and eight males,
age range 15-27 years) with severe rigid scoliosis that does not
correct on bending to less than 50° were treated by asymmetric
PSO and were prospectively followed for a minimum of two
years. This group was compared to a historical group of 25
patients treated earlier by the same surgeons by staged anterior
release and posterior fixation and fusion two weeks later.
Preoperative Cobb angle ranged between 75°-145° in the
asymmetric PSO and between 70°-150° in the staged group.
Both groups were stabilized posteriorly with pedicle screws only.
RESULTS: The total operative time and the duration of hospital
stay were significantly shorter in the asymmetric PSO group. The
amount of blood loss was also significantly less in the asymmetric
PSO group. The average preoperative Cobb angle improved from
110° to 38° postoperatively in the asymmetric PSO group (65%),
and from 102° to 50° in the staged group (50%). The difference
between the two groups was statistically significant in favor of
the PSO group. Complications were minimal in both groups.
DISCUSSION AND CONCLUSION: Asymmetric PSO appears to
be a very effective tool to correct severe coronal plane deformities.
It also minimizes blood loss, operative time and the duration of
hospitalization when compared to two-stage procedures.
The mean Pearson’s correlation coefficients for intraobserver
and interobserver reliabilities were 0.912 and 0.899, respectively.
DISCUSSION AND CONCLUSION: Our data suggests that
steroids are not effective in reducing postoperative prevertebral
soft tissue swelling but steroid could reduce symptom of dyspnea
during initial postoperative two days. A higher dosage is not more
effective in reducing postoperative edema.
POSTER NO. P398
Effect of Intravenous Steroid on Soft Tissue Swelling
after Anterior Cervical Discectomy and Fusion
Jung S. Lee, MD, Pusan, Republic of Korea
Kuen-Tak Suh, MD, Yangsan, Republic of Korea
Jeung Il Kim, MD, Pusan, Republic of Korea
Il Soo Eun, Pusan, Republic of Korea
Jong Min Lim, MD, Busan, Republic of Korea
INTRODUCTION: There were few clinical trials for reducing
prevertebral soft tissue swelling after anterior cervical discectomy and
fusion (ACDF). Therefore, we compared the effect of postoperative
administration of corticosteroids (dexamethasone) with that of
a placebo in ACDF for reducing prevertebral soft tissue swelling.
METHODS: Sixty-two consecutive patients with degenerative disc
disease of the cervical spine, who were treated by one level ACDF,
were examined prospectively. Subjects were assigned randomly
to three treatment groups. Group 1 received total of 40 mg
dexamethasone, group 2 received total of 80 mg dexamethasone,
and group 3 received placebo (normal saline); the first dose was
given immediately postoperatively, with subsequent doses given 24
hours and 48 hours after the operation. Plain cervical spine lateral
radiographs in the supine position were taken preoperatively,
immediately postoperatively, and then daily for five days after
operation. The area of the prevertebral soft tissue was measured from
lower border of C1 to upper end plate of C7 on the cervical spine
lateral radiographs using a PACS digital measuring instrument. The
patients were also examined to evaluate dyspnea and dysphagia
using 10-point visual analog scale (VAS). The area of prevertebral
soft tissue, dysphagia VAS and dyspnea VAS were peak on the
third day, first day and second day in all three groups, respectively.
RESULTS: There were 20 patients who received 40 mg
dexamethasone (group 1) immediately postoperatively, 24 hours
and 48 hours after operation, 20 patients who received 80 mg and
22 received placebo (group 3). The three groups did not differ
statistically with regard to age, gender, weight, height, smoking
status, length of surgery and fusion level. No patient needed
reintubation due to acute airway obstruction caused by soft tissue
swelling. The area of prevertebral soft tissue, dysphagia VAS and
dyspnea VAS were peak on the third day, first day and second day
in all three groups, respectively. The three groups did not differ
statistically with regard to the area of prevertebral soft tissue and
dysphagia VAS immediately postoperatively and daily for five
days after operation. However, group 1 and 2 showed significant
reductions in dyspnea VAS compared to group 3 on immediate
postoperative day, first and second day. There wasno significant
difference of dyspnea VAS on the third, fourth and fifth days among
the three groups. Group 1 and 2 showed no significant difference of
dyspnea VAS on each postoperative day. There was no correlation
between gender, operative time, fusion level, or smoking status
and degree of soft tissue swelling immediately postoperatively
and daily for five days after operation in all three groups. There
was no correlation among soft tissue swelling, dysphagia VAS
and dyspnea VAS on each postoperative day in all three groups.
1023
POSTER NO. P399
Can the Potential for Recovery of Upper Extremity
Function be Predictable Following Cervical Spinal Cord
Injury?
Tetsuo Hayashi, MD, Fukuoka, Japan
Osamu Kawano, MD
Takeshi Maeda, Iizuka, Japan
Yuichiro Morishita, MD, PhD, Iizuka, Japan
Tsuneaki Takao, MD, Iizuka, Japan
Hiroaki Sakai, MD
Keiichiro Shiba, MD, Iizuka, Japan
INTRODUCTION: Spinal cord injuries without radiographic
abnormality (SCIWORA) have been dramatically increased
with aging society. We have been treating all of these injuries
conservatively even if spinal cord compression may exist. It is well
known that the patient with incomplete tetraplegia due to spinal
cord injury may have the potential for neural recovery, however,
the prognostic factors of upper extremity functional recovery
still remain unclear. The purpose of this study is to detect the
prognostic factors of upper extremity functional recovery following
cervical cord injury. METHODS: A total of 526 patients with acute
spinal injuries were treated in our facility from 2005. Of these, 60
patients were selected retrospectively based on following criteria;
1) admission within three days following trauma, 2) more than six
months for observation, 3) evidence of C3-4 cord injury with T2
weighted MR images. The following subjects were excluded from
the study; patients who were with dementia, severe complications
in general, or demonstrated cervical myelopathy before trauma.
The American Spinal Injury Association (ASIA) impairment
scale, ASIA motor score for upper (ranged 0-50) and lower
extremities (ranged 0-50), and modified Zancolli classification
were documented. The functional evaluation of upper extremity
was made based on the ability to have meal by oneself: The upper
extremity function scale: (I) unable to bring hand to mouth (fullsupport), (II) unable to use spoon without brace, (III) able to use
reformed spoon, (IV) able to use normal spoon, (V) normal. 60
patients were evaluated at the time of admission, three days, two
weeks, one month, three months, six months following trauma.
RESULTS: Sixty patients included 54 men and six women, and the
average age was 63.2 years when they injured. Complete paralysis
(grade A in the ASIA impairment scale) at six months following
trauma was observed only in three out of 60 cases. One out of five
cases (20%) of C4 in modified Zancolli classification at three days
after trauma, seven out of 29 cases (29%) of C5, none out of two
cases (0%) of C6, six out of seven cases (86%) of C7, 18 out of 19
cases (95%) of C8, and all three cases (100%) of T1 demonstrated
greater than scale III, which was usable finger function, at six months
following trauma (Table). When compared the subjects with
useless function of upper extremity (the upper extremity function
scale I and II) and useful function (the upper extremity function
scale III, IV, and V) at six months following trauma, significant
differences were observed in ASIA motor score, both in upper (17.7
and 39.8, respectively) and lower (15.6 and 41.2, respectively)
extremities, at three days following trauma (p<0.05, p<0.05).
DISCUSSION AND CONCLUSION: Our results suggested that
reMEd motor neurological level evaluated with modified Zancolli
classification and ASIA motor score, both in upper and lower
extremities, might predict the future improvement of upper
extremity function.
POSTER NO. P400
ALTERNATE PAPER: SPINE V
Hypertrophy of Ligamentum Flavum in Lumbar Spinal
Stenosis is Associated with Increased bFGF Expression
Sittisak Honsawek, MD, PhD, Bangkok, Thailand
Chookiet Chalermpanpipat, MD, Bangkok, Thailand
Wicharn Yingsakmongkol, MD, Bangkok, Thailand
INTRODUCTION: Lumbar spinal canal stenosis is the most
common spinal disorder in elderly patients, causing low back and leg
pain, radiculopathy, and cauda equina syndrome. Canal narrowing
partly results from hyperthrophy of ligamentum flavum (LF), which
mechanically compresses nerve roots. Basic fibroblast growth factor
(bFGF) is a potent regulator of many cellular functions including
proliferation, differentiation, wound healing, and angiogenesis.
METHODS: The purpose of this study was to investigate the
pattern of bFGF expression in the ligamentum flavum of patients
with lumbar spinal stenosis. We quantified and localized bFGF
expression in LF tissues obtained during surgery from 19 patients
with lumbar spinal stenosis. bFGF expression was determined
with in situ using immunohistochemistry, reverse transcriptasepolymerase chain reaction (RT-PCR), and quantitative real-time
PCR. The values of bFGF in the surgically obtained LF specimens
were analyzed by enzyme-linked immunosorbent assay.
RESULTS: The bFGF expression was significantly higher in
hypertrophic LF of spinal stenosis than that in nonpathologic LF
of controls. bFGF was detected in the cytoplasm of LF fibroblasts.
The mean concentration of bFGF in the hypertrophic LF was
1024
remarkably greater in the pathologic LF of spinal stenosis when
compared to the nonpathologic LF of controls (P=0.003). In RTPCR, the mean optical density of bFGF was substantially higher
in the hypertrophic LF than controls (P=0.006). There was greater
bFGF expression in lumbar spinal stenosis patients as quantified
by real-time PCR (P=0.001). Moreover, there was a positive
correlation between the tissue bFGF expression of the pathologic
LF and patient age in spinal stenosis patients (r = 0.63, P < 0.001).
DISCUSSION AND CONCLUSION: This data demonstrated that
increased bFGF expression was associated with the degenerative
changes of hypertrophic LF, suggesting that bFGF could play a
potential role in pathogenesis of hypertrophic ligamentum flavum
in lumbar spinal stenosis patients.
POSTER NO. P401
ALTERNATE PAPER: SPINE IV
Radiological Risk Factors of Curve Progression in
Degenerative Lumbar Scoliosis
Hideki Murakami, Morioka, Japan
Ken Yamazaki, MD,PhD, Morioka, Japan
Endo Hirooki, Morioka City, Japan
Daisuke Yamabe, Morioka City, Japan
INTRODUCTION: Surgery could be selected for lumbar degenerative
scoliosis cases with disabling symptoms and progressive deformity.
However, there is lack of consensus for surgical treatment because
natural history of lumbar curve progression is still unknown.
It is important to find objective risks of curve progression in
especially patients with low magnitude degenerative lumbar
curve are more common in our clinical practice. Therefore we
analyzed radiological findings in a patient with de novo low
magnitude but measurable degenerative coronal curvature of the
lumbar spine and documented potential associated risk factors.
METHODS: A total 53 de novo degenerative scoliosis patients
(age ≥50 years) were followed non-operatively for a minimum
of 24 months and measured curve magnitude at presentation
and latest follow up. They were classified patients with curve
progression of less than 5° and 5° as non-progression group (31
patients: 9 males and 22 females) and those of more than 5° as
progression group (22 patients: 6 males and 16 females). Tilt of
vertebral body, wedging angle of disc space, wedging angle of
vertebral body, lateral listhesis, vertebral rotation, and lateral
translation of apical vertebra were measured at presentation
and latest follow up and compared between progression
group and non-progression group. Furthermore, correlations
between curve progression and changes of each parameter were
analyzed using Spearman’s correlation coefficient by rank test.
RESULTS: Tilt of L4 vertebral body was 9.50±5.98° in progression
group and 6.39±4.78° in non-progression group. L2 vertebral
rotation was 0.95±0.80° in progression group and 0.52±0.51°
in non-progression group. Lateral translation of apical vertebra
was 17.90±8.0 mm in progression group and 13.43±7.47 mm
in non-progression group. There were significant differences
between two groups, respectively. There existed a correlation
between curve progression and change of lateral listhesis at
L3-4 with 0.57 (P=0.007) of correlation coefficient. There was
no correlation between curve progression and other parameters.
DISCUSSION AND CONCLUSION: We should attend to curve
progression in degenerative lumbar scoliosis with large tilt of L4,
L2 vertebral rotation and lateral translation of apical vertebra.
Patients with degenerative lumbar scoliosis might be at increased
risk for curve progression if they have progressive lateral listhesis
at L3-4.
POSTER NO. P402
POSTER NO. P403
Instrumented Lumbar Surgery in Patients with Liver
Cirrhosis - A Gender, Age, Diagnosis Matched Cohort
Analysis
Revision Surgery after Instrumentation and Fusion in
Adolescent Idiopathic Scoliosis
Jen-Chung Liao, MD, Kweishian, Taoyuan, Taiwan
INTRODUCTION: Liver cirrhosis means an irreversible, diffused
fibrosis, and nodule formation after hepatic necrosis. Malnutrition,
impaired immunity, coagulopathy, and encephalopathy often
develop in patients with liver cirrhosis; which means liver cirrhotic
patients carry high surgical risks. However, there is no information
in English literature about the results of liver cirrhotic patients
who underwent instrumented lumbar surgery. The purposes
of the present study were to review the results of instrumented
lumbar surgery in patients with liver cirrhosis and determine the
surgical risk factor in these patients. METHODS: After obtaining
IRB approval, we retrospectively reviewed patients with liver
cirrhosis who underwent spine surgery between 1997 and 2009.
Twenty-nine patients with liver cirrhosis who had undergone
instrumented lumbar surgeries for degenerative lumbar disease
were studied. The hepatic function reserve of the patients was
recorded according to the Child-Turcotte-Pugh scoring system.
The medical records and laboratory data were collected. We
documented every complication during admission. Any event
causing reoperation, requirement of intensive cage, prolonged
hospital stay (over 14 days), or admission after discharge within
30 days of surgery was also defined as perioperative complication.
The clinical outcomes were assessed by a 5-grade patient-centered
general outcome assessment questionnaire. All data were
compared with those for matched patients without liver cirrhosis.
RESULTS: Liver cirrhotic patients had significantly lower
preoperative hemoglobin, white blood cell count, platelet, albumin
level; higher prothrombin time and bilirubin level. Instrumented
lumbar surgery was associated with significantly more blood loss,
a longer hospital stay, more complication in patients with liver
cirrhosis as compared with control patients (Table I). Although
the final satisfactory rate was higher in the control group, it
was not statistically different (85% vs. 65%, p= 0.240). In the
cirrhotic group, 22 patients (76%) were Child class A and seven
patients (24%) belonged to Child class B; 12 patients developed
one or more complications (Table II). Patients with Child class
B carried a significantly higher incidence of complications
than those with Child class A (p=0.006). Inside patients with
Child class A, those with 6-point also had a significantly higher
incidence of complications than those with 5-point (p<0.001)
(Table III). Female (p=0.035), a low level of albumin (p=0.002),
presence of ascites (p=0.029), and an increased blood loss
(p=0.044) were associated with a higher risk of complications.
DISCUSSION AND CONCLUSION: The rate of complications
after instrumented lumbar surgery was significantly higher in
cirrhotic patients than in control patients (P= 0.007), especially in
those with a 6 or higher Child-Turcotte-Pugh point. Perioperative
complications might result in unsatisfactory clinical outcomes.
The surgeon should counsel these patients on the possibility of
development of early complications. Several factors were associated
with surgical complications; spine surgeons should correct these
factors before or when they perform these elective instrumented
lumbar surgeries.
1025
Kelley E. Banagan, MD, Baltimore, MD
Peter F. Sturm, MD, Cincinnati, OH
Jessica Day, Chicago, IL
Anne Riordan, BA, Chicago, IL
Melanie Bland, BS, Chicago, IL
Kim W. Hammerberg, MD, Chicago, IL
INTRODUCTION: Spine fusion is expected to be the definitive
treatment for adolescent idiopathic scoliosis; however
recent studies have shown that reoperation rates for revision
surgery may be as high as 12%. The purpose of this study
was to examine the rates and long term outcomes of patients
who have undergone revision surgery for complications
after a primary instrumentation and fusion for adolescent
idiopathic scoliosis at single institution over a 20-year period.
METHODS: After study approval from the Institutional Review
Board, the billing code databases at our institution were searched
to identify those patients with the diagnosis of adolescent
idiopathic scoliosis from 1986 to 2006. A retrospective chart review
was then performed on the patients identified by the databases
to identify those patients that had a diagnosis of adolescent
idiopathic scoliosis and underwent a primary fusion procedure
at the Shriners Hospital for Children in Chicago. Patients were
followed for a minimum of five years, and return visits to the
operating room for a secondary, unplanned surgery were recorded.
RESULTS: There were 1,136 patients identified by the database
query. Of those, 327 patients met the inclusion criteria; they carried
a diagnosis of adolescent idiopathic scoliosis, and underwent a
fusion procedure at the Shriners Hospital for Children between 1986
and 2006. There were 282 female, and 45 male patients. Average
Cobb angle at time of surgery was 59.9, and average age at initial
surgery was 14.6 years. There were 223 posterior only procedures,
60 anterior only surgeries and 44 combined procedures. There were
a total of 16 revision procedures in 13 patients (3.97%); nine of the
patients were female and four were male. There were four return
visits for irrigation and debridement secondary to infection. Two
of the procedures were in the same patient. There were five revision
procedures for progression of the curve, or junctional deformity,
three procedures for symptomatic hardware, two procedures for
scar revision, and two revision surgeries for pseudoarthroses.
DISCUSSION AND CONCLUSION: Instrumentation and fusion
for the treatment of adolescent idiopathic scoliosis is not always
the definitive surgical intervention. However, based on our
findings at a single institution over a 20-year time period, we feel
that the operation is successful, with an acceptably low revision
rate of 3.97%.
POSTER NO. P404
Proteonomic Analysis of CSF Biomarkers in Cervical
Myelopathy
Louis G. Jenis, MD, Newton, MA
Robert J. Banco, MD, Newton Corner, MA
INTRODUCTION: Cervical spondylotic myelopathy (CSM) is
a common condition leading to dysfunction of the upper and
lower extremities. Natural history studies suggest progression
of symptoms and the mainstay of treatment for neurological
deterioration remains surgical intervention. Prognostic factors
have been long sought for including examination findings,
characteristics on MRI including myelomalacia, and duration of
symptoms among others. While numerous studies have evaluated
altered cerebrospinal fluid (CSF) protein levels in CNS pathologies,
including acute spinal cord injury (SCI) secondary to trauma or
ischemia during surgery, multiple sclerosis and amyotrophic lateral
sclerosis, there is very limited research specifically addressing the
role of proteonomic biomarkers in CSF as a means of establishing
prognosis in CSM. The purpose of this study is to prospectively
evaluate patients with CSM and correlate protein biomarkers
within the CSF compared to a normal control population.
METHODS: Twenty patients were prospectively enrolled into
the study. Institutional Review Board approval was obtained.
Five patients (control) scheduled for a total knee replacement
and undergoing a spinal anesthetic with lumbar puncture were
enrolled. Each of these patients provided a screening evaluation
to rule out the presence of neck pain or potential neurological
symptoms. Fifteen patients with CSM were identified and also
entered into the study. Each of these patients underwent a lumbar
puncture at the time of their surgery. 1-2ml of CSF was obtained
from both the control and CSM patients. Twenty CSF candidate
protein biomarkers were analyzed and total protein concentration
calculated. No patient sustained complications related to the lumbar
puncture. Demographic data was collected from the CSM patients.
RESULTS: CSM patients - average age was 56.5+/-8.7 years (41 - 68)
and duration of their symptoms were 9.9+/-12.9 months (1 - 48).
Average levels of cord compression were 2.0+/-1.1 (1-4) and modified
Japanese Orthopedic Association preoperative score was 13+/-2.6
(6-16). When comparing control versus patients with CSM, four
proteonomic analyses revealed differences. Human Brain-Derived
Neurotropic Factor (BDNF) and Pigment Epithelium Derived
Factor (PEDF) were significantly decreased in myelopathy patients
whereas Apolipoprotein A-1 (ApoA1) and Vascular Endothelial
Growth Factor (VEGF) were significantly elevated. Within the CSM
patient group, no significant difference was noted in CSF protein
concentration when comparing age or the presence of intrinsic
cord changes. However, symptom duration of greater than six
months resulted in significant elevation of Platelet Derived Growth
Factor (PDGF) and Transforming Growth Factor beta (TGFβ).
DISCUSSION AND CONCLUSION: The results from this pilot
study confirm significant differences in protein biomarkers within
the CSF in patients with and without CSM. Protein levels may
reflect structural or functional degenerative change, repair or
regeneration within the central nervous system. The differences
noted may allow for clinical prognostication in terms of surgical
timing and eventual outcome and, more importantly, may provide
for a better understanding of the pathological process of CSM.
While small numbers of patients were enrolled in this pilot study,
the results suggest that further research within this area may be
beneficial.
POSTER NO. P405
uHydrogel Safety and Effectiveness in Reducing Risk
of Posterior Spinal Revision Surgery Neural Tissue
Damage
randomly assigned to the treatment group and the laminectomy
defect was overlaid with the permanent hydrogel film, which
was secured by one suture to an adjacent spinous process. The
remaining surgical site was assigned to the control group, for
which the laminectomy defect was left uncovered. During the
in-life phase, the animals were subjected to clinical pathology
evaluations as well as multiple neurological assessments to
monitor any deficit. Three sheep were evaluated at 30 and 93 days
and two at 184 days to assess the presence and quality of a plane
of dissection by performing a revision surgery at the same levels.
Tissues surrounding the surgical sites as well as main organs were
histologically processed to assess biological response to the material.
RESULTS: All animals reMEd healthy and had blood hematology
and chemistry results within normal limit throughout the study
and survived their respective time point. While minor neurological
deficits were reported immediately after surgery, those observations
resolved within few days post-implant and there was no subsequent
abnormal finding until termination. At the time of the revision
surgery, normal cytology was reported at all sites (impression
smears), the structural properties and appearance of the device
reMEd intact (flexible, hydrophilic, no visible decomposition) even
though some damages were induced while removing prominent
bone growth in one animal of the 180-day time point. The plane
of dissection assessments demonstrated that the PVA hydrogel film
provided significantly reduced levels of adhesions (scores of 1-2)
compared to the control group (scores of 2-4) using scoring system
in table below and allowed easy localization of the prior surgical
site by the surgeons conducting the revision surgery. The material
was well tolerated by the animals, with minimal histological
signs of inflammation or rejection locally and in main organs.
DISCUSSION AND CONCLUSION: The PVA hydogel film was
proven to be safe and provided a clear plane of dissection during
revision surgery, allowing for facilitated access to the initial
laminectomy defect while reducing the risks of neural tissue
damage that may occur with high level of tissue adhesions at the
surgical site, as seen in the control group, where the device was not
used.
Score scheme for the presence and quality of a plane of dissection
Score
Description
1
Separates with no adhesion – applicable tissues can be safely separated
from the study site without the use of surgical tools
2
Easily detachable – applicable tissues can be safely separated from
the study site with minimal use of blunt surgical tools to overcome light
adhesion
3
Dissection required – applicable tissues can be safely separated from the
study site while using blunt surgical tools to overcome moderate adhesion
4
Sharp dissection required – applicable tissues cannot be separated from
the study site without risk of damage as the use of sharp surgical tools is
required to overcome tenacious adhesion
Paul Jeffords, MD, Atlanta, GA
Guilhem Denoziere, Kennesaw, GA
INTRODUCTION: The development of scar tissue and adhesions
following posterior spinal surgery presents a significant problem
when revision surgery is required. Adhesion involvement of
overlying structures can present a difficult surgical environment
and significantly increase the risk of major neural tissue injury.
METHODS: Bilateral laminectomies and discectomies were
completed at the L2/3 and L4/5 lumbar intervertebral discs in eight
sheep using a standard posterior approach. One surgical site was
1026
SCIENTIFIC EXHIBITS
SCIENTIFIC EXHIBIT NO. SE66
The Performance of a Lumbar Total Disc Replacement
In Vivo: A Retrieval Analysis of Wear Properties and
Fixation
Timothy M. Wright, PhD, New York, NY
Celeste Abjornson, PhD, New York, NY
Introduction: To understand the performance of lumbar total disc
replacement(LTDR) devices in vivo, we performed a prospective
analysis of retrieved devices. We hypothesized that resection of
the anterior longitudinal ligament necessary for implantation
results in evidence of posterior component impingement.
Methods: Twenty ProDisc-L devices from 19 patients (age 44.7±2.9
years) were studied after a mean implantation time of 1.0±.31yrs
(range 2days-5.8 years). Polyethylene(PE) and metallic(CoCrMo)
components were examined using light stereo-microscopy(6X31X) for wear, surface damage, and ongrowth. Areas of interest
were evaluated using scanning electron microscopy(SEM) and
3rd body debris using energy dispersive x-ray analysis (EDAX).
Results: The operative level was L4-L5 in 30%(n=6), L5-S1
in 60%(n=12), and unknown in 10%(n=2). Indications for
explantation were pain 45%(9/20), prosthesis subluxation/
migration 20%(4/20), endplate collapse/prosthesis subsidence
15%(3/20), PE dislodgement 15%(3/20), and unknown
10%(2/20). Areas of ongrowth were present on the Ti plasma
sprayed coating on both components in 75%(15/20), one
component in 5%(1/20), and neither component in 20%(4/20).
Burnishing consistent with component impingement was present
most commonly in the posterior quadrant in 60%(12/20)
(p<.001). Anterior (40%), and lateral (15%) patterns were also
seen. Circumferential burnishing patterns were not observed.
Backside wear was observed in 75%(12/16) of the implants that
were disassembled and 3rd body wear was observed in 30%(6/20).
Discussion and Conclusion: Burnishing consistent with posterior
impingement was seen in the majority of retrieved LTDR devices.
The high loads in the lumbar spine predispose to backside wear
at early time points. Long-term follow-up studies will determine
the clinical sequelae of backside wear and posterior impingement.
disc positioning on surface and subsurface stresses as well as
polymeric wear volumes using a finite element model and how they
corroborate with clinical wear patterns observed in retrieved devices.
Methods: Finite element (FE) model of an artificial ball-on-socket
cervical disc (metal-on-polymer similar to Prodisc-C) was created in
AbaqusTM software (Dassault Systems, Providence RI). The disc was
then placed in an experimentally validated ligamentous C5-C6 FE
model simulating appropriate surgery and subjected to boundary/
loading conditions of flexion/extension= ±7.5°, lateral bending =
±6° and rotation= ±4° via time-dependent amplitudes within a
single loading step as per ISO18192 . This model was subjected to a
follower load to emulate the effect of muscles. An adaptive meshing
technique was utilized to compute the wear depth on the surface of
the polymeric core. These models were further modified by moving
the device by 0.5 mm in anterior and posterior directions from
the neutral position. The positional wear data were compared.
Results: The wear patterns for the implanted cases were lopsided
irrespective of their position. Lift-off/separation was also
observed at the device interface for all cases during extension
and bending. An increase in surface and subsurface stresses
was observed for both the anterior and posterior test cases in
comparison to the neutral position. The maximum linear wear
was computed for the posterior test case while the minimum
wear was observed for the neutral case (Fig 1.a). The posterior
case also reported the maximum cumulative volumetric wear of
1.14 mm3 compared to the neutral value of 0.6 mm3 (Fig 1.b).
This study demonstrates that wear is not only dependent on stress
but also on device placement. The maximum wear, both linear and
volumetric, resulting from posterior positioning of cervical disc
replacements is attributed to an increase in the sliding distance
between the interacting implant surfaces. This finding strongly
suggests that accurate device placement is requisite for achieving
optimal clinical outcome. Comparison with retrievals supports
this finding. Posterior placement of cervical disc replacements
should be avoided.
Cervical Artificial Disc Wear: The Influence of Surgical
Placement
Sanghita Bhattacharya, PhD, Cleveland, OH
Vijay Goel, PhD, Toledo, OH
A. S. Greenwald, DPhil Oxon, Cleveland Heights, OH
Introduction: Relative motion at interacting implant surfaces
generates wear debris over time leading to periprosthetic osteolysis
and device failure. Factors related to implant design, patient
habitus and surgical approach will impact the generation of wear
debris and influence the clinical longevity of artificial spinal disc
devices. Further, surgeons play an important role in selecting the
appropriate implant size as well as its placement within the disc
space to optimize soft tissue balance and alignment. Current wear
testing standards for artificial discs do not account for the influence
of anatomic structures or variations in disc placement. This exhibit
describes the influence of neutral, anterior and posterior cervical
1027
Algorithm for Decision Making Process of Spine
Metastatic Diseases
Alessandro Gasbarrini, MD, Bologna, Italy
Simone Colangeli, MD, Bologna, Italy
Riccardo Ghermandi, MD, Bologna, Italy
Cesare Faldini, MD, Bologna, Italy
Sandro Giannini, MD, Bologna, Italy
Stefano Boriani, MD, Bologna, Italy
Introduction: The target of treatment of spine metastatic disease
should be to improve quality of life, but there is no consensus on
the treatment selection. Since 2004 an algorithm was proposed.
The decision making process includes: anesthesiological
evaluation, sensitivity to medical and radiation oncology
treatments, neurological conditions, pathological fractures,
systemic spread of the disease and possible treatment. The
treatment options are: decompression and fixation, debulking, en
bloc excision, non surgical treatment. Methods: 43 consecutive
patients (20 male, 23 female), average age 56,2 (min 32-max 81)
affected by spine metastasis from carcinoma were treated and
retrospectively evaluated. To evaluate the results the concept of
“target achievement” was introduced; the target is achieved when
the following findings are present: survival rate not inferior to the
average, calculated on epidemiological data for each histotypes;
improvement or maintenance of neurological condition;
achievement of local control, no local recurrences and no increase
of tumor size. Results: The algorithm was followed in 26 cases
and the target was achieved in 20 cases (77%). The algorithm was
not followed in 17 cases: 14 cases were defined as overtreatment
(target achievement: 36%), 3 cases as undertreatment (target
achievement: 67%). Discussion and Conclusion:: The algorithm
is a series of logical sequences, patient centered and based on
multidisciplinary approach. The results demonstrate that the
majority of the patients have a good residual quality of life. Worse
results are obtained when a more aggressive treatment is selected.
uImpingement Characterization of Total Disc
Replacements
Ryan Siskey, MS, Philadelphia, PA
Genevieve A. Hill, Silver Spring, MD
Jonathan Peck, ME, Silver Spring, MD
Steven A. Rundell, PhD, Farmingtn Hls, MI
Steven M. Kurtz, PhD, Philadelphia, PA
Methods: Impingement of TDRs occurs when the device
reaches the limits of its functional range of motion causing
peripheral regions of the device to contact. Depending on the
design, impingement regions can be bearing surfaces or nonbearing surfaces and can be associated with increased wear
and mechanical damage. Impingement, Mode IV wear, is not
accounted for in the current pre-clinical test methods, rather they
only focus on intended bearing wear, Mode I wear. Therefore,
results from bench testing do not accurately mimic some of the
more worst-case wear and damage observed in vivo. Using wear
and damage maps collected from 55 mobile bearing Charité
retrievals, in combination with finite element analyses of a
subset of these clinical cases, the in vivo boundary conditions
associated with TDR impingement were developed. Therefore, a
set of fixtures, intended to mimic facet contact during extension
were developed. A mode I and mode IV wear tests were completed
to establish the baseline wear performance and impinged wear
performance of a mobile bearing lumbar disc design. The resulting
wear morphology under Mode I and Mode IV conditions for
the in vitro tested samples were compared to in vivo retrieved
devices to assess the validity of the impingement test protocol.
Results: All samples demonstrated multidirectional scratching
on both the inferior and superior domes under standard Mode I
conditions. For all samples, under impingements conditions, the
wear shifted to posterior rim of the cores. The wear morphology
was consistent between both the aged and non-aged samples
and consistent with the wear observed on the retrieved devices.
Using a protocol, which mimics in vivo facet contact, posterior
impingement can be replicated on the bench. In this scientific
exhibit we will present the methods used to characterized the
retrieved and in vitro devices. We will also present the finds
from the validation study and explain how the protocol can be
used to evaluate other device designs and bearing combinations.
Discussion: The end goal of the FDA critical path project is
to developing an international standard, through ASTM, for
impingement characterization of total disc devices. This scientific
exhibit will demonstrate the design, implementation and
validation of an impingement procedure. It will then extrapolate
its application to other designs and material bearing combinations.
All of this will be presented in the context of retrieval analysis as
a basis for procedure verification and validation and the use of
retrievals as a feedback mechanism to the device design process.
Introduction: Total disc arthroplasty is an alternative treatment
to spinal fusion in the treatment of neck or low back pain, as it is
thought to reduce the risk of disease progression in the adjacent
spinal levels. To date, five Total Disc Replacements (TDRs) have
been PMA-approved and approximately fifty TDR designs are
in development. In light of the ongoing development of new
designs, validated in vitro test methods for TDRs are crucially
needed. Ongoing retrieval analyses of approved TDRs of varying
device designs show evidence of impingement damage in
regions other than the primary, intended bearing surface. These
finding have lead the FDA to begin requesting impingement
testing as part of the preclinical testing package for total disc
devices. Through its critical path initiative, the FDA has funded
research to investigate and develop an internal standard for
impingement characterization of total disc devices. The objective
of this effort is to develop and validate an impingement test
methodology that mimics the clinical impingement scenario.
1028

SPINE - AAOS

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