retrospective saetia

3962
Chin Med J 2013;126 (20)
Meta analysis
Comparing minimally invasive and open transforaminal lumbar
interbody fusion for treatment of degenerative lumbar disease: a
meta-analysis
SUN Zhi-jian, LI Wen-jing, ZHAO Yu and QIU Gui-xing
Keywords: transforaminal lumbar interbody fusion; degenerative lumbar disease; minimally invasive surgery;
mini-open surgery; meta-analysis
Background Transforaminal lumbar interbody fusion (TLIF) through a minimally invasive approach (mTLIF) was
introduced to reduce soft tissue injury and speed recovery. Studies with small numbers of patients have been carried out,
comparing mTLIF with traditional open TLIF (oTLIF), but inconsistent outcomes were reported.
Methods We conducted a meta-analysis to evaluate the effectiveness of mTLIF and oTLIF in the treatment of
degenerative lumbar disease. We searched PubMed, Embase and Cochrane Database of Systematic Reviews in March
2013 for studies directly comparing mTLIF and oTLIF. Patient characteristics, interventions, surgical-related messages,
early recovery parameters, long-term clinical outcomes, and complications were extracted and relevant results were
pooled.
Results Twelve cohort studies with a total of 830 patients were identified. No significant difference regarding average
operating time was observed when comparing mTLIF group with oTLIF group (−0.35 minute, 95% confidence interval
(CI): −20.82 to 20.13 minutes). Intraoperative blood loss (−232.91 ml, 95% CI: −322.48 to −143.33 ml) and postoperative
drainage (−111.24.ml, 95% CI: −177.43 to −45.05 ml) were significantly lower in the mTLIF group. A shorter hospital stay
by about two days was observed in patients who underwent mTLIF (−2.11 days, 95% CI: −2.76 to −1.45 days). With
regard to long-term clinical outcomes, no significant difference in visual analog scale score (−0.25, 95% CI: −0.63 to 0.13)
was observed; however, there was a slight improvement in Oswestry Disability Index (−1.42, 95% CI: −2.79 to −0.04)
during a minimum of 1-year follow-up between the two groups. The incidence of complications did not differ significantly
between the procedures (RR=1.06, 95% CI: 0.7 to 1.59). Reoperation was more common in patients in mTLIF group than
in oTLIF group (5% vs. 2.9%), but this difference was not significant (RR=1.62, 95% CI: 0.75 to 3.51).
Conclusion Current evidence suggests that, compared with traditional open surgery, mTLIF reduces blood loss and
allows early postoperative recovery, while achieving comparable or slightly better long-term outcomes, and with a
comparable risk of complications.
Chin Med J 2013;126 (20): 3962-3971
S
ince first described by Harms and Rolinger in 1982,1
transforaminal lumbar interbody fusion (TLIF) has
gained popularity for treatment of degenerative lumbar
diseases. 2-5 This procedure allows for circumferential
fusion via a single posterolateral approach. Compared
with posterior lumbar interbody fusion (PLIF), TLIF
has advantages including decreased dural sac retraction,
lower risk of postoperative radiculitis, and preservation of
posterior column integrity.6 Moreover, TLIF also shows
advantages for revision surgery and upper lumbar surgery.7-9
The open TLIF (oTLIF) approach requires extensive
tissue dissection and retraction to expose the anatomical
landmarks for pedicle screw insertion and resection of
the facet complex. Numerous authors have reported the
destructive effects of muscle dissection and retraction.10-13
To minimize approach-related morbidity, multiple
minimally invasive approaches to the lumbar spine have
been developed in recent years. The minimally invasive
TLIF (mTLIF) procedure was first described by Foley et al.
in 2003.14 This minimally invasive procedure is performed
via a muscle-dilating approach, which significantly
diminishes the amount of iatrogenic tissue injury.
Subsequently, mini-open TLIF via a paraspinal muscle
splitting (Wiltse) approach was introduced15 and numerous
clinical studies of these minimally access surgeries have
since been published.4,16-62
MTLIF and mini-open TLIF were designed with the aim
of reducing iatrogenic soft tissue injury while gaining
comparable or better clinical outcomes compared with
the traditional open approaches. This is reflected in the
shorter operating time, less intraoperative blood loss,
shorter hospital stay, and comparable or better clinical
DOI: 10.3760/cma.j.issn.0366-6999.20131539
Department of Orthopedics, Peking Union Medical College Hospital,
Chinese Academy of Medical Sciences and Peking Union Medical
College, Beijing 100730, China (Sun ZJ, Li WJ, Zhao Y and Qiu GX)
Correspondence to: Dr. ZHAO Yu, Department of Orthopedics,
Peking Union Medical College Hospital, Chinese Academy
of Medical Sciences and Peking Union Medical College,
Beijing 100730, China (Tel & Fax: 86-10-69152809. Email:
[email protected])
Chinese Medical Journal 2013;126 (20)
symptom improvement and complication rate. However,
studies directly comparing mTLIF with oTLIF usually
contain a small number of patients, and some of the
results reported by different institutions are inconsistent.4,26,28,30-33,37,38,44,46,49,52,57,59 In order to evaluate mTLIF, we
searched PubMed, Embase, and the Cochrane Database of
Systematic Reviews for published trials and performed a
meta-analysis to identify the effectiveness of mTLIF and
oTLIF for patients with lumbar degenerative diseases, and
to determine whether mTLIF is superior compared with
traditional procedures.
METHODS
Search strategy
PubMed, Embase, and the Cochrane Database of
Systematic Reviews were searched on March 19, 2013,
using the keywords “minimally invasive”, “mini-open”,
“open” and “transforaminal lumbar interbody fusion”. A
hand search of bibliographies of pertinent articles was also
performed for additional studies.
Inclusion and exclusion criteria
Only studies directly comparing mTLIF and oTLIF
for the treatment of degenerative lumbar disease and
providing surgical-related messages (including average
operating times, intraoperative blood loss, postoperative
drainage, and the amount of blood transfused), clinical
assessments, and complications were included. The
population number and follow-up period were not limited.
Randomized controlled trials (RCTs) were preferentially
enrolled; however, owing to the specificity of surgical
intervention, all comparative studies were included.63
mTLIF included mTLIF using a nonexpandable tubular
retractor combined with percutaneous screw fixation and
mTLIF using an expandable tubular retractor through a
Wiltse approach.64,65 The following types of articles were
excluded; (1) mTLIF compared with other open lumbar
interbody fusion techniques, such as open PLIF, (2) studies
that did not provide surgical-related messages or clinical
outcomes, (3) case reports, (4) case series, (5) reviews and
comments, (6) biomechanical studies, (7) cadaveric studies,
and (8) languages other than English. When more than one
study from the same group or institution met the inclusion
criteria, only the study with the largest number of patients
or the latest report was included.
Selection of studies
Two of the authors (SUN Zhi-jian and LI Wen-jing)
independently assessed potentially eligible studies, applying
the inclusion/exclusion criteria, with any disagreement
being resolved through discussion. Reviewers were not
blinded to titles of journals, names of authors or financial
support.
Data extraction
Data were extracted independently by the aforementioned
two authors. We documented the authors, journal, and
year of publication for each included study. Outcomes
3963
were categorized into primary and secondary outcomes.
The primary outcomes included surgical-related messages
and early recovery parameters, and secondary outcomes
were long-term clinical results and complications. The
following data were then extracted; (1) study type, (2)
number of male and female patients, (3) mean age, (4)
diagnosis, (5) surgical approach, (6) surgical level, (7) bone
graft sources, (8) follow-up period, (9) operating time,
(10) blood loss, including intraoperative blood loss and
postoperative drainage, (11) amount of transfusion, (12)
time to ambulation, (13) dose and duration of narcotic use,
(14) hospital stay, (15) time to return to work, (16) pre- and
post-operative and follow-up clinical assessment measures,
such as visual analog scale (VAS) for back and leg pain,
Oswestry Disability Index (ODI) for disability, and short
form-36 (SF-36), and (17) complications (including number
of reoperations). Complications were not predefined and
were defined by each study. There were no standards
defining major and minor complications; therefore, the
reoperation rate was analyzed further, which suggested
serious surgical-related complications occurred. This was
thought to be an objective indicator.
Methodological quality assessment
Only non-randomized studies were included in this metaanalysis. Therefore, the Newcastle-Ottawa Scale (NOS)
(http://www.ohri.ca/programs/clinical_epidemiology/
oxford.htm), which is one of the most useful for assessing
methodological quality of non-randomized studies
described by the Cochrane Handbook for Systematic
Reviews of Interventions Version 5.1.0 (http://handbook.
cochrane.org), was used to assess the risk of bias in the
included studies. “Selection” (4 items), “comparability” (1
item), “exposure/outcome” (3 items) were evaluated, and
each “high” quality choice was awarded a “star”.
Data synthesis and statistical analysis
Mean difference and 95% confidence intervals (CIs) were
calculated for continuous outcomes, including operation
time, intraoperative blood loss, postoperative drainage,
hospital stay, preoperative and last follow-up VAS and
ODI scores. In studies that failed to provide standard
deviations (SDs), SDs were estimated from mean and P
values,26,28,32,44,57 assuming two-sample t tests. If SD and
P values were both absent, the data were excluded.28 For
studies reporting VAS of back pain and leg pain, the VAS
scores were combined.44,52 The odds ratio (OR) and 95%
CI were calculated for dichotomous outcomes, including
total complications and reoperations. RevMan 5.0 software
(Cochrane IMS) was used to perform the meta-analysis.
The test for heterogeneity revealed by the forest plot was
used to test for statistical heterogeneity, and I2 was used
to estimate the size of the heterogeneity.66,67 An I2 value
no more than 50% was considered as low heterogeneity.67
Owing to the differences in the designs of the included
studies, random effects were assumed for all outcome
measures.68 Publication bias was estimated by funnel plot,
and asymmetry in the funnel was present if publication bias
existed.
Chin Med J 2013;126 (20)
3964
RESULTS
Search results
From the search strategy, 139, 148, and one article were
identified in PubMed, Embase and Cochrane Database
of Systematic Reviews, respectively. By screening the
titles and abstracts, 264 articles were excluded according
to the inclusion/exclusion criteria. The full articles of the
24 remaining studies were obtained for more detailed
evaluation. Two studies comparing mTLIF with open
PLIF and one study comparing mTLIF with mini-open
TLIF were excluded. 19,24,58 One study evaluated back
muscle degeneration using magnetic resonance imaging
between mTLIF and oTLIF and one focused on superior
facet violation of pedicle screw placement in mTLIF and
oTLIF.62,69 Two articles from the same institution evaluated
cost-effectiveness of mTLIF versus oTLIF.60,70 One article
only reported surgical site infection after minimally
invasive versus open TLIF/PLIF.71 Sixteen articles met the
inclusion criteria: two studies from the Singapore General
Hospital,30,52 two from Boulder Neurosurgical Associates,4,32
and three from Xinqiao Hospital31,37,46 were limited to one
study from each institution in order to avoid repetitive
patient data. Twelve comparative studies were eventually
included in the meta-analysis.26,28,31-33,38,44,49,52,57,59,72 However,
no RCTs were retrieved. The process of identifying relevant
studies is illustrated in Figure 1.
Description of studies
Descriptive information for the included studies is given
in Table 2. Overall, the current study included 829 patients
(412 in the mTLIF group and 417 in the oTLIF group),
with an overall mean age of 52.4 and 52.8 years old in
the mTLIF group and oTLIF group, respectively. In the
mTLIF and oTLIF groups, 56% and 56.6% of patients were
female, respectively, although two studies did not provide
sex distribution.26,28 The preoperative diagnosis included
degenerative disc disease and spondylolisthesis, but two
studies did not provide these details. Three studies involved
patients with more than one level of TLIF procedure.32,59,72
The other articles only included single level TLIF patients.
Multiple bone graft materials were used for interbody
fusion, including allograft, local autograft, recombinant
human bone morphogenetic protein-2 (rhBMP-2), iliac
crest bone graft, demineralized bone matrix, and biphasic
calcium phosphate. However, local autograft was preferred
by most surgeons. Minimum follow-up period ranged from
a minimum of 6 months49 to a maximum of 26 months.32
Operation-related parameters
The average operating times of 11 of the 12 included
studies were pooled. There was no significant difference
Methodological quality assessment of included studies
The study types and NOS assessments are provided in
Table 1. Of the 12 included studies, five were prospective
cohort studies and seven were retrospective cohort studies.
A range of 5–9 stars was gained evaluating by NOS,
indicating median to high methodological quality of the
included studies. The notable methodological shortcomings
included: (1) outcome measure assessment was not
processed by an independent investigator not involved with
clinical care, (2) study controls of potential factors between
two groups were insufficient, (3) the minimum follow-up
period was <24 months, and (4) patients in the two groups
might not have come from the same population.
Figure 1. Process of identifying eligible studies.
Table 1. Methodological quality assessment of included studies
Studies
Adogwa et al, 2011
Dhall et al, 2008
Fan et al, 2010
Lau et al, 2011
Lee et al, 2012
Pelton et al, 2012
Saetia et al, 2013
Schizas et al, 2009
Villavicencio et al, 2010
Wang et al, 2010
Wang et al, 2011
Zairi et al, 2013
*
Country
Research type
USA
USA
China
USA
Singapore
USA
Thailand
Switzerland
USA
China
China
France
Retrospective cohort study
Retrospective cohort study
Prospective cohort study
Retrospective cohort study
Prospective cohort study
Retrospective cohort study
Retrospective cohort study
Prospective cohort study
Retrospective cohort study
Prospective cohort study
Prospective cohort study
Retrospective cohort study
Selection‡
★★★★
★★★★
★★★★
★☆★★
★★★★
★★★★
★★★★
★☆★★
★☆★★
★★★★
★★★★
★★★★
Newcastle-Ottawa Scale
Comparability*
★★
☆☆
★★
☆☆
★☆
★☆
☆☆
☆☆
★☆
☆★
★★
★☆
Outcome†
★★★
☆★★
★★★
☆★★
★★★
☆☆★
☆★★
☆★★
☆★★
☆★★
☆★★
☆★★
The most important factors for study control were defined as the number of surgical levels and patients with previous lumbar surgery; other additional factors were
defined as patients’ age, sex, diagnosis and surgical level (L3-4, L4-5 or L5-S1). †The minimum follow-up period was defined as 12 months.‡ “ ★ ” indicates that the
assessed study met our inclusion criteria, whereas “ ☆ ” indicates that it did not.
Chinese Medical Journal 2013;126 (20)
3965
Table 2. Characteristics of patients in mTLIF and oTLIF groups
Studies
Adogwa 2011
mTLIF
oTLIF
Dhall 2008
mTLIF
oTLIF
Fan 2010
mTLIF
oTLIF
Lau 2011
mTLIF
oTLIF
Lee 2012
mTLIF
oTLIF
Pelton 2012
mTLIF
oTLIF
Saetia 2013
mTLIF
oTLIF
Schizas 2009
mTLIF
oTLIF
Villavicencio 2010
mTLIF
oTLIF
Wang 2010
mTLIF
oTLIF
Wang 2011
mTLIF
oTLIF
Zairi 2013
mTLIF
oTLIF
No. of Mean age
Sex ratio
patients (years)
(male/female)
DDD
Diagnosis
Spondylolisthesis
No. of Surgical
level
Graft material
Minimum follow-up
period (months)
15
15
50.8
49.7
7/8
5/10
0
0
15
15
Single level
Single level
Allograft
Local autograft
24
24
21
21
53
53
NA
NA*
14
10
7
11
Single level
Single level
rhBMP-2 (6), local autograft (15)
rhBMP-2 (7), ICBG(11), both (3)
12
12
32
30
51.4
52
18/14
14/16
27
22
5
8
Single level
Single level
ICBG
NA
24
24
10
12
46.9
56.9
4/6
5/7
6
6
4
6
Multi-levels*
Multi-levels*
NA
NA
12
12
72
72
52.2
56.6
20/52
22/50
NA
NA
NA
NA
Single level
Single level
Local autograft and DBM
Local autograft, DBM and rhbmp-2
24
24
33
33
51.7
49.9
23/10
21/12
13
14
20
19
Single level
Single level
NA
NA
6
6
12
12
63.1
67.4
1/11
6/6
0
0
12
12
Single level
Multi-levels†
Local autograft
Local autograft
24
24
18
18
45.5
48.1
NA
NA
3
12
15
6
NA
NA
Local autograft and ICBG
Local autograft and ICBG
12
12
76
63
58.9
50.5
34/42
24/39
NA
NA
NA
NA
Multi-levels‡
Multi-levels‡
rhBMP-2 (43), local autograft (20)
rhBMP-2 (61), local autograft (15)
26
26
42
43
47.9
53.2
13/29
16/27
0
0
42
43
Single level
Single level
Local autograft
NA
13
13
41
38
51.4
57.3
24/17
23/15
30
24
11
14
Single level
Single level
Local autograft
Local autograft
24
24
40
60
49
48
20/20
28/32
18
25
22
35
Single level
Single level
BCP
Local autograft(30), BCP(30)
24
24
Nine and seven received single level surgery in the mTLIF and oTLIF groups, and one and five patients had two-level surgery in the mTLIF and oTLIF groups,
respectively. †Eleven patients received single level surgery, whereas one patient had two-level surgery in the oTLIF group. ‡Forty-seven and 57 patients received single
level surgery in the mTLIF and oTLIF groups, and 16 and 19 patients had two-level surgery in the mTLIF and oTLIF groups, respectively. BCP: biphasic calcium
phosphate; DBM: demineralized bone matrix; DDD: degenerative disc disease; ICBG: iliac crest bone graft; NA: not available; rhBMP-2: recombinant human bone
morphogenetic protein-2.
*
between the two groups (−0.35 minute, 95% CI: −20.82
to 20.13 minutes). However, operating time showed
significant heterogeneity between the studies (I2=92%, P
<0.01). Intraoperative blood loss was significantly lower
in the mTLIF group (−232.91 ml, 95% CI: −322.48 to
−143.33 ml). Statistical heterogeneity was also significant
among the studies (I2=93%, P <0.01). Five studies reported
postoperative drainage, and one did not use postoperative
drains in the mTLIF group, with no adverse outcomes.52
Postoperative drainage in the remaining four studies was
pooled for meta-analysis, and a significantly smaller
amount of postoperative drainage was identified in the
mTLIF group (−111.24 ml, 95% CI: −177.43 to −45.05 ml).
Significant heterogeneity was also observed (I2=91%, P
<0.01). The pooled results for operation-related parameters
are illustrated in Figure 2. Less intraoperative blood loss
and less postoperative drainage resulted in a reduced
rate and amount of blood transfusion. Only three studies
gave details of the amount of blood transfusion in the two
groups. Two of these found that the need for allogenic
blood transfusion was significantly reduced in the mTLIF
group compared with oTLIF group.31,33 Lau et al72 also
reported less blood transfused, although the difference was
not significant.
Early recovery assessment
The overall results showed that the length of hospital stay
was about two days shorter for patients who underwent
mTLIF (−2.11 days, 95% CI: −2.76 to −1.45 days).
Statistical heterogeneity was significant among the studies
(I 2=77%, P <0.01) (Figure 3). Other early recovery
parameters were seldom evaluated. Three studies compared
time to ambulation after surgery; all of which found that
ambulation time was significantly shorter in the mTLIF
group.33,52,72 Two studies evaluated time to return to work
(or normal life) and both found a shorter time to return
to work for the mTLIF patients. 38,44 To evaluate early
postoperative wound pain, three studies reported narcotic
usage. Lee et al52 found that the mTLIF patients required
only about 10% of the amount of intravenous morphine that
was required by the oTLIF patients. Nevertheless, Schizas
et al28 suggested that there was no difference in the average
morphine sulfate intake between the two groups. Adogwa
et al44 reported that mTLIF patients needed two weeks less
narcotic analgesic treatment than oTLIF patients needed.
Chin Med J 2013;126 (20)
3966
heterogeneity was not significant among the
studies for postoperative VAS scores (I2=26%,
P=0.24) (Figure 4).
Figure 2. Forest plots of operation-related parameters. A: Operating time. B:
Intraoperative blood loss. C: Postoperative drainage.
Figure 3. Forest plots of hospital stay.
Long-term outcomes
VAS and ODI were most commonly used for evaluating
clinical outcomes. VAS was used in 10 of 12 studies to
assess back and leg pain relief after surgery. However, one
study only reported 6-month postoperative VAS scores
for low back pain and statistical significance was reached
in comparison of mTLIF versus oTLIF patients.49 Three
studies did not provide enough data for pooled analysis and
no significant differences of preoperative and last follow-up
VAS scores were found between the two techniques.28,38,57
Meta-analysis was performed in the remaining six studies.
There was no significant difference in preoperative VAS
scores between the two groups (VAS score=0.08, 95% CI:
0.29–0.46). Postoperatively, a substantial decrease in the
VAS score with a minimum of one year follow-up was
observed in both groups. However, there was no difference
in VAS scores at last follow-up between the two groups
(VAS score=−0.25, 95% CI: −0.63 to 0.13). Statistical
Four studies did not use ODI to evaluate
clinical outcomes.26,32,49,72 Of the remaining
eight studies, three did not provide enough
messages for meta-analysis, of which Schizas
et al28 and Zairi et al57 found no significant
differences in changes in ODI between the
two groups during one and two years followup, respectively. However, Wang et al 38
showed that ODI was significantly better in
the mTLIF group at three and six months
after surgery, but this difference diminished
at 12 and 24 months. ODI scores reported by
five studies were included for meta-analysis.
Preoperative ODI indicated no significant
difference between the two procedures
(ODI=2.14, 95% CI: −0.10 to 4.38). A
substantial decrease in ODI with a minimum
of one-year follow-up was also observed in
both groups. A slightly greater improvement
in ODI was seen in the mTLIF group during
at least one-year follow-up (ODI=−1.42,
95% CI: −2.79 to −0.04). There was no
statistical heterogeneity among the studies for
postoperative ODI (I2=0, P=0.95) (Figure 4).
Other clinical outcome measures reported
by the included studies were EuroQol-5D,
modified Prolo Scale (mPS), pain outcome
scores, SF-36, North American Spine Society
scores for neurogenic symptoms (NASS),
returning to full function, patient rating of the
overall result of surgery, MacNab’s criteria,
and Patient Satisfaction with Results Survey
(PhDx Systems, Albuquerque, NM).26,32,44,52,72
No significant differences in any of these
measures was seen between the mTLIF and
oTLIF groups.
Complications
All reported complications were as follows: wound
hematoma, durotomy or cerebrospinal fluid leakage, screw
malposition, cage migration, rod migration, pseudarthrosis,
wound infection, deep venous thrombosis, ileus,
myocardial infarction, pulmonary infection, radiculopathy,
subcutaneous collection, neurological deficit, brachial
plexus palsy, cage rupture, nonunion, allograft malposition,
switch from minimally invasive to open approach, anemia,
fat liquefaction, and ventricular tachycardia. One study did
not report complications.49 Comparable total complications
occurred in the mTLIF (16.9%) and oTLIF (15.1%) groups
(RR=1.06, 95% CI: 0.7 to 1.59), and heterogeneity was
not significant (I2=0, P=0.65). The reoperation rate did not
differ significantly in the two groups (5% in the mTLIF
group and 2.9% in the oTLIF group; RR=1.62, 95% CI:
0.75 to 3.51). Heterogeneity among studies was also not
Chinese Medical Journal 2013;126 (20)
3967
studies have not agreed in their entire
ty,4,26,28,30–33,37,38,44,46,49,52,57,59 we performed this
meta-analysis using all possible studies that
directly compared these two procedures to
give more objective evidence to surgeons.
Figure 4. Forest plots of VAS and ODI at least 1 year after surgery. A:
Postoperative VAS scores at a minimum of one year follow-up. B: Postoperative
ODI at minimum of one-year follow-up.
No difference in operating time was found
in our meta-analysis. Mean operating time
ranged from 113 to 348 minutes in the
included studies. Many factors could have
caused such a wide difference, such as number
of surgical levels,32,59 revision surgery,32 and
surgeons’ experience. Notably, the steep
learning curve for mTLIF procedure could
significantly influence operating time.53,74,75
Three studies reported the learning effect and
all observed that a longer operating time was
needed for the initial cases.26,28,32 Schizas et
al28 found that the average duration of surgery
fell by 1.8 hours from the first third to the
last third of the 18 consecutive operations
performed. Villavicencio et al32 observed that
the mean operating time decreased from 238.5
minutes for the first 26 cases to 231.5 and
193.2 minutes for the middle 25 and the last
25 cases, respectively. Neal et al75 reported
28 mTLIF procedures performed by a single
resident/attending team and found that the
operating time decreased by about 20 minutes
from the first to the last 13 cases (two cases
excluded). In addition, mTLIF and oTLIF
were performed by different surgeons in
some studies.26,31,44,52 Nevertheless, the overall
operating time for these two procedures was
comparable in the pooled results, although
there were many potential impact factors.
mTLIF is supposed to reduce blood loss due
to less soft-tissue dissection. The pooled
results showed intra- and postoperative
blood loss was 232.91 ml and 111.24 ml less
Figure 5. Forest plots of total complications and reoperations. A: Total
complications. B: Reoperations.
following mTLIF surgery than oLTIF surgery.
The amount of transfused fluids was also reduced in the
mTLIF group reported by Fan et al33 and Wang et al.31
significant (I2=0, P=0.90) (Figure 5).
Although postoperative transfusion did not differ between
mTLIF and oTLIF when reported by Lau et al, fewer in
Publication bias
the mTLIF group received intraoperative transfusion.72
Publication bias was detected for all of the parameters that
The reduced blood loss for mTLIF probably makes it more
were pooled using a funnel plot.
suitable for special populations, such as elderly patients
who have greater comorbidity.18,41,45 However, minimally
DISCUSSION
invasive procedures would better be carried out in elderly
patients after the initial learning curve.
As minimally invasive lumbar surgery has emerged,
mTLIF is more frequently chosen by surgeons. The
Aiding early recovery is another supposed advantage of
fundamental advantage of mTLIF comes from its decrease
the mTLIF procedure. In the current systematic review,
of soft tissue dissection and retraction, which reduces
time to ambulation, length of hospital stay, and time to
blood loss and helps with early recovery.73 Other than
return to work were all shorter in the mTLIF group. Length
that, mTLIF can achieve comparable, if not better, longof hospital stay was reported by all the included studies
term clinical outcomes compared with traditional open
and the pooled result showed that hospital stay was two
procedures. Given that the results of recent comparative
3968
days shorter for mTLIF patients. Early time to ambulation
reduces the risk of perioperative complications, such as
venous thromboembolism.76 Reduced hospital stay and
accelerated return to work may confer an economic benefit
from the societal and hospital perspective. 60,70,77
Owing to the use of muscle-splitting, tubular retraction
systems that limited the amount of soft tissue injury, less
postoperative pain was expected, which would be reflected
by the duration and dose of narcotic use. Most studies
confirmed reduced narcotic usage following mTLIF.19,44,52
Wang et al31 also identified that the VAS scores for back
pain were lower in mTLIF versus oTLIF patients on the
third day after surgery. However, Schizas et al28 did not
find this effect. Results of narcotic use were not pooled for
meta-analysis owing to lack of reports and more evidence
is needed for further evaluation.
Many different measures were used to assess long-term
clinical outcomes. VAS scores quantifying back and leg
pain and ODI for disability were most commonly used.
Both minimally invasive and traditional open approaches
achieved dramatic improvement in long-term outcomes.
Similar outcomes of VAS scores were seen in both mTLIF
and oTLIF groups in our meta-analysis. A slight superiority
was observed for ODI in the pooled results for the mTLIF
group, yet not in each independent study.28,31,33,38,44,52,57,59
Apart from the postoperative recovery period, the
advantage of mTLIF may not be seen in long-term followup outcomes.77 Nevertheless, comparable long-term clinical
outcomes were promising between mTLIF and oTLIF
procedures.
Complications were not analyzed by different types,
considering their low incidence. mTLIF is technically
more challenging because it involves a smaller operative
field, manipulation through tubular retractors, and requires
more radiological assistance in the placement of screws
and cages.26,52 In particular for initial learners, neurological
injuries, inadequate decompression, and pedicle screw/
cage malposition are more likely to happen. Villavicencio
and colleagues32 reported the total rate of neurological
deficit was 10.5% in the mTLIF group compared with 1.6%
in the oTLIF group. Thus, they suggested the potential
benefit of the mTLIF procedure must be weighed against
the increased rate of neural-injury-related complications
associated with the learning curve.
Although initial cases were included in the pooled results
(five studies declared initial cases were included,26,28,32,52,72
six not, 33,38,44,49,57,59 and one stated that mTLIF was
performed by one experienced surgeon31), there was no
difference in the total number of complications between the
mTLIF and oTLIF groups. In order to determine whether
more major complications were more likely to happen
during mTLIF surgery, complications that needed revision
surgery were pooled. Even though the reoperation rate
was higher in the mTLIF group, the difference was not
significant.
Chin Med J 2013;126 (20)
Some limitations of this meta-analysis should be considered
when interpreting our results. The first one was the low
quality of the included studies, considering no RCTs were
carried out. Heterogeneity was frequently observed and
publication bias was seen in all the pooled parameters;
all of which might have influenced our results. Another
limitation was that these studies were carried out in
different countries under different medical care systems,
thus, some of the evaluation of the results differed, such as
hospital stay, and time to return to work. Also, there was a
steep learning curve associated with the mTLIF procedure,
which is reported to be correlated with shorter operating
time, less estimated blood loss, and fewer complications.
However, it was difficult to adjust for this important
confounder, because none of the studies provided initial
and subsequent data separately. Additionally, not all the
studies used the same technique for mTLIF and oTLIF, but
the different minimally invasive and open techniques were
treated equally.
From the pooled result of 12 cohort studies, we suggest
that mTLIF reduces blood loss and aids early postoperative
recovery, while achieving comparable or slightly better
long-term outcomes with a comparable risk of total
complications, compared with traditional open surgery.
High-quality RCTs are needed for further validation of our
results.
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(Received June 13, 2013)
Edited by LIU Huan