Adductor Surgery to Prevent Hip Displacement in Children with

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C OPYRIGHT ! 2012
BY
T HE J OURNAL
OF
B ONE
AND J OINT
S URGERY, I NCORPORATED
Adductor Surgery to Prevent Hip Displacement in
Children with Cerebral Palsy: The Predictive Role of
the Gross Motor Function Classification System
Benjamin J. Shore, MD, FRCSC, Xavier Yu, MBBS, BA, Sameer Desai, MS, MRCS(Ed), Paulo Selber, MD, FRACS,
Rory Wolfe, BSc, PhD, and H. Kerr Graham, MD, FRCS(Ed), FRACS
Investigation performed at the Royal Children’s Hospital, Parkville, Australia
Background: The purpose of this study was to evaluate the relationship between walking ability, as determined with use
of the Gross Motor Function Classification System (GMFCS), and the outcome of hip adductor surgery used to prevent hip
displacement in children with cerebral palsy.
Methods: We performed a retrospective review of the records of all children with cerebral palsy whose index surgery,
performed between January 1994 and December 2004 at one tertiary-level pediatric hospital, was bilateral hip adductor
releases. All children had a hip migration percentage of >30% in at least one hip prior to the adductor surgery, and the
minimum duration of follow-up was twenty-four months. Kaplan-Meier survivorship curves were generated by determining
the time from the index surgery to ‘‘failure,’’ defined as either the need for subsequent surgical procedures or a migration
percentage of ‡50% in either hip. Hazard ratios were calculated for sex, migration percentage at the time of the index
surgery, age at the time of the index surgery, and GMFCS level.
Results: Three hundred and thirty children were included in the study; 73% (242) were nonambulatory (GMFCS level IV or
V). The mean age at the time of the index surgery was 4.2 years, the mean migration percentage was 43%, and the mean
duration of postoperative follow-up was 7.1 years. Surgery consisted of open lengthening of the adductor longus and
gracilis muscles in all children, with additional procedures as deemed necessary. ‘‘Success’’ was defined as the absence
of subsequent surgical procedures during the study period and a migration percentage of <50% in both hips at the time
of follow-up. One hundred and six children (32%) met these criteria for success. The success rate was 94% (thirty-one of
thirty-three) in children at a GMFCS level of II, 49% (twenty-seven of fifty-five) in children at a level of III, 27% (twenty-eight of
103) in children at a level of IV, and 14% (twenty of 139) in children at a level of V.
Conclusions: Walking ability, as defined with use of the GMFCS level, is a strong predictor of success or failure after
hip adductor surgery in children with cerebral palsy. The paradox of hip adductor surgery for children with cerebral palsy is
that the children who are most severely affected and need the surgery the most have the poorest results.
Level of Evidence: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third
party in support of any aspect of this work. One or more of the
authors, or his or her institution, has had a financial relationship, in
the thirty-six months prior to submission of this work, with an entity in
the biomedical arena that could be perceived to influence or have the
potential to influence what is written in this work. Also, one or more of
the authors has had another relationship, or has engaged in another
activity, that could be perceived to influence or have the potential to
influence what is written in this work. The complete Disclosures of
Potential Conflicts of Interest submitted by authors are always
provided with the online version of the article.
J Bone Joint Surg Am. 2012;94:326-34
d
http://dx.doi.org/10.2106/JBJS.J.02003
A commentary by Robert J. Bielski, MD, is
linked to the online version of this article at
jbjs.org.
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ip displacement, defined as a migration percentage of
>30%1, affects 35% of children with cerebral palsy. The
incidence is directly related to the functional level as
determined with use of the Gross Motor Function Classification
System (GMFCS) but not to the type of movement disorder2. The
GMFCS is a five-level ordinal grading system that has been confirmed in a number of studies to be a valid, reliable, stable, and
clinically relevant method for the classification and prediction of
motor function of children with cerebral palsy who are between
two and twelve years of age3. Hip displacement in children with
cerebral palsy may result in pain and diminished function, including difficulties with simple tasks such as standing for transfers or with higher functions such as standing and walking4-11.
Nonoperative interventions, including bracing and injections of botulinum toxin A, do not demonstrate a clinically
important treatment effect12. Surgical approaches to the management of hip displacement in children with cerebral palsy have
been classified as preventive, reconstructive, or salvage13. Preventive surgery is the term applied to various approaches designed
to treat or prevent early hip displacement in younger children
whose hip is still in joint but shows signs of being ‘‘at risk.’’14,15
Miller and Bagg16 demonstrated that the migration percentage
affects the risk of progression of hip displacement and concluded
that children with a migration percentage of between 30% and
60% would have a continued risk (25%) of further displacement
as they aged. Preventive surgery applies to surgical procedures that
involve lengthening of some of the hip adductors and may also
involve lengthening of the hip flexors and occasionally phenolization of the obturator nerve or anterior-branch obturator neurectomy17-19. However, there has been disagreement about the
timing and indications for these procedures, the specific muscles to
release, and postoperative management20. Reconstructive surgery
for hip displacement in patients with cerebral palsy includes osteotomy of the proximal aspect of the femur, the pelvis, or both
that can be used to treat residual hip subluxation and early dislocation13. The typical outcome of one-stage reconstruction for a
subluxated or dislocated hip in children with cerebral palsy has
been described as successful in several large studies21-23.
Given the heterogeneity of the cerebral palsy population
and the variability in treatment protocols, including the multi-
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plicity of hip adductor surgical procedures that have been employed, it is difficult to draw firm conclusions from the many
studies regarding the success of adductor procedures in preventing hip displacement. Soft-tissue releases (muscle recessions and
tenotomies) have been reported to be helpful in the prevention of
hip displacement1,24. It has been suggested that if early detection
and screening programs are used, 80% of children with spastic
hip disease should have a ‘‘good’’ or ‘‘fair’’ outcome, defined as a
migration percentage of <40%, following one simple operation25.
However, in an extensive review of adductor releases for hip
displacement in patients with cerebral palsy, Stott and Piedrahita26
concluded that the current evidence base was poor and that it was
difficult to draw definitive conclusions. Weaknesses in the evidence base include the lack of clinical trials, the heterogeneity of
the patient populations studied, variability in the surgical procedures performed, and short-term and incomplete follow-up26.
The primary goal of the present study was to examine the
long-term success of hip adductor surgery in a large group of
children with cerebral palsy who had been managed by a small
group of surgeons according to standardized protocols. The
secondary goal was to investigate the relationship between
walking ability, as determined with use of the GMFCS, hip
displacement, and the success of adductor surgery.
Materials and Methods
W
e performed a retrospective, population-based cohort study of children
with cerebral palsy identified with use of the Victorian Cerebral Palsy
27
Register (VCPR), which has a high degree of accuracy and case capture . This
study was approved under the clinical audit provisions of our institution’s
Human Research Ethics Committee.
28
Inclusion criteria were (1) a diagnosis of cerebral palsy , bilateral involvement (diplegia or quadriplegia), and registration in a statewide Cerebral
27
Palsy Register ; (2) index surgery consisting of bilateral hip adductor releases
performed at our tertiary-level pediatric hospital between January 1994 and
December 2004; (3) a minimum clinical and radiographic follow-up duration
of twenty-four months from the time of the index surgery; and (4) adequate
medical records and hip radiographs to determine the outcome. Exclusion
criteria were (1) a diagnosis other than cerebral palsy that did not satisfy the
requirements for registration in the statewide Cerebral Palsy Register; (2) index
surgery on the hip adductors that was performed elsewhere; (3) a diagnosis of
monoplegia or hemiplegia and unilateral adductor surgery; and (4) inadequate
case records or radiographs.
TABLE I Patient Characteristics According to GMFCS Level at the Time of Adductor Surgery*
GMFCS Level
No. (%)
II
33 (10)
III
55 (17)
IV
V
All
Mean Age at
Surgery (mo)
Initial Migration
Percentage at Surgery†
Mean Duration
of Follow-up (mo)
R
L
41
36 (28-47)
34 (21-42)
84
46
39 (24-52)
39 (28-55)
85
103 (31)
49
42 (21-60)
42 (28-64)
87
139 (42)
55
47 (31-60)
48 (28-64)
85
330
50.2
43 (21-64)
85.5
*GMFCS = Gross Motor Function Classification System. †The values are given as the mean percentage, with the range in parentheses.
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TABLE II Surgical Characteristics According to GMFCS Level*
Surgery Type† (no.)
GMFCS Level
1
2
3
4
Total
II
33
0
0
0
33
III
38
15
2
0
55
IV
11
57
30
5
103
V
All
0
25
65
49
139
82
97
97
54
330
*GMFCS = Gross Motor Function Classification System. †1 =
lengthening of adductor longus and gracilis, 2 = type 1 plus
lengthening of the iliopsoas at the lesser trochanter, 3 = type 2
plus phenolization of the anterior branch of the obturator nerve,
and 4 = type 2 plus anterior obturator neurectomy.
The management of hip displacement in children with cerebral palsy at
our institution includes early detection by means of systematic screening, early
preventive surgery, reconstructive surgery when preventive surgery fails, and efforts to avoid salvage surgery. Long-term follow-up is offered to all children with
cerebral palsy from the time of diagnosis until the transition to adult services at an
age of eighteen to twenty years. Indications for adductor surgery were clinical and
radiographic, including an abduction range of <40" in one or both of the hips and
a migration percentage of >30% in one or both of the hips. Indications for
reconstructive surgery were a persistently high migration percentage (>50%) for
more than two years after initial adductor surgery in one or both of the hips.
Indications for salvage surgery were severe pain that was refractory to medical and
tone management combined with severe osseous deformity that was considered
to not be amenable to reconstructive surgery.
Every patient underwent bilateral adductor longus and gracilis muscle
releases. The anterior fibers of the adductor brevis muscle were released in a
small number of hips with more severe contractures to achieve abduction of
>50" in both hips. Lengthening of the iliopsoas tendon at the lesser trochanter
was added in nonambulatory children if the hip flexion contracture was >20".
Phenolization (with use of a 6% aqueous solution) or neurectomy of the
anterior branch of the obturator nerve was performed in severely affected
(GMFCS level IV or V) patients with preoperative scissoring. In patients with
asymmetric hip displacement, the final surgical prescription differed between
sides, with the aim being symmetric abduction of >50" in both hips. Specific
details of the surgical protocol for adductor release and phenolization can be
29
found in the Appendix and have been previously published elsewhere .
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After meticulous hemostasis, the groin incisions were irrigated with
normal saline solution containing cephalosporin antibiotic, closed with absorbable sutures, and sealed with an adhesive, waterproof dressing (Tegaderm, 3M, St.
Paul, Minnesota). Abduction ‘‘A-frame’’ casts, consisting of above-the-knee cylinder plaster casts joined by an abduction bar just above the ankles, were applied
with the hips abducted 30" to 40" and the knees extended. The casts were routinely removed after three weeks. In ambulatory children, no additional bracing
was used. In children at GMFCS level IV or V, a fixed-angle abduction brace was
fitted after cast removal and used for twenty-three hours per day for three months
and then at night only until twelve months postoperatively.
The migration percentage was measured on the initial radiograph made
1,30
at the time of the index surgery by a method with good reliability . Gross
motor function and walking ability were classified with use of the GMFCS,
31
using age-appropriate descriptors . The GMFCS level was determined from
hip surveillance records (if the child was ambulatory), gait laboratory assessments (if the child was ambulatory), or standardized assessments by develop31
mental pediatricians and physical therapists .
Surgical ‘‘success’’ was defined as the absence of subsequent hip surgery
during the study period and a migration percentage of <50% in both hips at the
time of the most recent follow-up. Surgical ‘‘failure’’ was defined as either the
need for any subsequent surgery to treat hip displacement or a migration
percentage of ‡50% in either hip. The numbers of children who were lost to
follow-up, children who were deemed medically unfit for further surgery,
parents who were unwilling to consent to further surgery, and hips that subsequently dislocated (migration percentage >100%) and/or needed salvage
surgery were also recorded.
Statistical Methods
Means and standard deviations were used to summarize continuous variables
(age at the time of the index surgery and index migration percentage) that were
symmetrically distributed. Kaplan-Meier curves for the time to failure according to GMFCS level were used to graphically display surgical success. Cox
proportional-hazards regression analysis was used to calculate hazard ratios to
compare the failure risk between subgroups of children and with regard to
continuous variables. Stata statistical software was used for all analyses (version
10; StataCorp, College Station, Texas).
Source of Funding
There was no external funding source for this study.
Results
etween January 1994 and December 2004, 342 children
underwent bilateral hip adductor surgery, and 330 were
eligible for this study. Four of the twelve children who were
B
TABLE III Surgical Success According to GMFCS Level*
Treatment Following Failure† (no.)
GMFCS Level
Success Rate
Osseous Rec.
Rev. STS
M1
M2
Salvage
II
31/33, 94%
2
III
27/55, 49%
27
0
IV
28/103, 27%
57
6
V
20/139, 14%
75
15
All
106/330, 32%
161
21
Total
0
0
0
0
2
1
0
0
28
10
1
1
75
12
11
6
119
23
12
7
224
*GMFCS = Gross Motor Function Classification System. †Osseous Rec. = osseous reconstructive surgery; Rev. STS = revision soft-tissue surgery;
M1 = subluxation (migration percentage >50%), not yet treated; M2 = dislocation (migration percentage >100%), not yet treated; and salvage =
salvage surgery (5 Castle, 2 McHale).
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TABLE IV Surgical Success According to Patient and Surgical Characteristics*
Univariate Analysis
Characteristic
HR
95% CI
Sex
Female
Male
1
1.0
0.8 to 1.3
Initial MP
1.09†
1.07 to 1.11
Age in months
at index surgery
1.02‡
1.01 to 1.03
1
3.6
4.0
4.5
Surgery type§
1
2
3
4
GMFCS
II
III
IV
V
1
10.9
17.0
25.9
Multivariate Analysis
P Value
HR
95% CI
P Value
1
1.0
0.7 to 1.3
<0.001
1.08†
1.06 to 1.11
<0.001
<0.001
0.99‡
0.98 to 1.00
0.20
2.1 to 5.3
2.5 to 6.3
2.8 to 7.3
<0.001
<0.001
<0.001
1
1.7
1.3
1.6
1.0 to 3.0
0.7 to 2.4
0.8 to 3.1
0.07
0.42
0.20
2.6 to 45.8
4.2 to 69.3
6.4 to 105.0
0.001
<0.001
<0.001
1
8.5
8.1
8.7
2.0 to 36.3
1.8 to 36.6
1.9 to 40.3
0.004
0.006
0.006
0.86
0.84
*Calculated by Cox proportional-hazards regression analysis of time to failure. HR = hazard ratio, CI = confidence interval, MP = migration
percentage, and GMFCS = Gross Motor Function Classification System. †Increase in hazard for a 1% increase in MP. ‡Increase in hazard for a onemonth increase in age. §1 = lengthening of adductor longus and gracilis, 2 = type 1 plus lengthening of the iliopsoas at the lesser trochanter, 3 =
type 2 plus phenolization of the anterior branch of the obturator nerve, and 4 = type 2 plus anterior obturator neurectomy.
excluded were lost to follow-up within twenty-four months of
surgery, and the other eight had missing or incomplete clinical
and radiographic records. The mean duration of follow-up was
eighty-five months (standard deviation, twenty-five months;
range, twenty-four to 161 months).
Thirty-three (10%) of the children were at GMFCS level II,
fifty-five (17%) were at level III, 103 (31%) were at level IV, and
139 (42%) were at level V (Table I). The overall rate of success
was 32% (106 of 330), with the remaining 68% (224) of the
procedures being classified as ‘‘failures’’ because the children
Fig. 1
Kaplan-Meier plot of surgical success (i.e., survival until failure according to the study definition) according to the Gross Motor Function Classification
System (GMFCS) level.
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Fig. 2
An illustrative case of hip adductor surgical failure. Hip radiographs of a child with spastic quadriplegia cerebral palsy (GMFCS level V) from eleven months to
four years and four months of age are shown. In each radiograph, the age in years and months is indicated in the bottom left and the number in the
chronological sequence in the top right. Panel 1 (age, eleven months) shows early ossification of the proximal femoral epiphysis and mild acetabular
dysplasia in the right hip. The position of the ventriculoperitoneal shunt is also visible. Panel 2 (age, two years and two months) shows hip displacement with
a migration percentage of 52% in the right hip and 18% in the left. Panel 3 (age, two years and five months) shows bilateral hip dislocations. Surgery had been
delayed because of unstable epilepsy and feeding difficulties. Panel 4 (age, two years and seven months) shows concentric reduction of both hips after
bilateral adductor and psoas releases, including phenolization of the anterior obturator nerve. Panel 5 (age, two years and nine months) shows
redisplacement of the hips. Panel 6 (age, four years and four months) shows bilateral hip redislocation, which required osseous reconstructive surgery.
either required a subsequent surgical procedure involving the
hip or had persistent hip displacement. The success rate was 94%
(thirty-one of thirty-three) in children at a GMFCS level of II,
49% (twenty-seven of fifty-five) in children at a level of III, 27%
(twenty-eight of 103) in children at a level of IV, and 14% (twenty
of 139) in children at a level of V.
Eighty-two children underwent isolated lengthening of
the adductor longus and gracilis, and ninety-seven children
underwent lengthening of the adductor longus, gracilis, and
iliopsoas. An additional ninety-seven patients underwent phenolization of the anterior branch of the obturator nerve and fiftyfour patients underwent obturator neurectomy of the anterior
branch in addition to the above-mentioned muscle lengthening
(Table II).
Of the 106 successes, the mean initial hip migration percentage (and standard deviation) was 21% ± 11% in the right
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Fig. 3
An illustrative case of hip adductor surgical success. Sequential anteroposterior radiographs of the hips of a child with spastic diplegia (GMFCS level II) are
shown. In each radiograph, the age in years and months is indicated in the bottom left and the number in the chronological sequence in the top right. Panel
1 (age, two years and eight months) shows bilateral hip displacement with a migration percentage of 58% in the left hip and 22% in the right. Bilateral hip
adductor releases were performed. Panel 2 (age, five years and five months) shows some improvement in the migration percentage in both hips, and the
patient had progressed to independent walking. Panel 3 (age, seven years and two months) shows that hip development has continued but bilateral
dysplasia is evident. Panel 4 (age, twelve years and four months) shows that the right hip is considered to be within normal limits but the left remains mildly
dysplastic with a migration percentage of 22%.
hip and 20% ± 10% in the left. In the 224 failures, the mean
initial hip migration percentage was 45% ± 8% in the right hip
and 46% ± 9% in the left. The mean age at the time of the index
surgery was 4.4 years in patients in whom the outcome was
classified as a failure and 3.7 years in the patients in whom it was
a success. For the 224 failures, the mean age at the time of failure
was 8.4 ± 2.2 years and the mean time from surgery to failure
was 4.0 ± 2.2 years. An association among higher GMFCS level,
increased initial migration percentage, and increased age at the
time of the index surgery was noted (Table I).
The majority of failures (161 of 224, 72%) were treated
with osseous reconstructive surgery (Table III). In addition,
thirty-five of the failures (twenty-three with subluxation
[migration percentage of >50%] and twelve with dislocation
[migration percentage of >100%]) had not been treated with
definitive surgery at the time of the last review; the reasons
included poor general health, parental wishes, and lack of
symptoms. No abduction contractures occurred after obturator nerve neurectomy; however, two extension contractures occurred after phenolization of the obturator nerve
combined with iliopsoas release, and these were managed
uneventfully with chair modification and proximal hamstring release.
Nineteen deaths (6%) were recorded in the study cohort; all were in children at a GMFCS level of V, resulting in a
death rate of 14% in this group. The cause of death was respiratory failure in thirteen of the patients, complications
following epileptic seizures in two, and acute renal failure, a
complication of an existing hematological disorder, complications of a fundoplication procedure, and septicemia in one
patient each. At the time of death, the index surgery had been
classified as a failure in nine (47%) of these patients and was
still classified as a success in ten. None of the deaths were
recorded within the first two years following the adductor
surgery.
The surgical success rate decreased with increasing
GMFCS level (Fig. 1). At thirty-six months, the success curve
for the GMFCS II group diverged slightly from those of the
GMFCS III, IV, and V groups. However, at eighty-four months
(seven years) the success curves diverged markedly, with the
failure rate in the GMFCS II group remaining stable over time
but all other GMFCS groups experiencing increasing failure
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rates. Univariate analysis revealed that, compared with the
GMFCS III group, the GMFCS IV group had a higher risk of
failure (hazard ratio [HR], 1.6; 95% confidence interval [CI],
1.0 to 2.4; p = 0.05). Similarly, the GMFCS V group had a
higher risk of failure than the GMFCS IV group (HR, 1.5; 95%
CI, 1.1 to 2.0; p = 0.005) (Table IV).
Only the GMFCS level and the initial migration percentage remained important predictors of the failure risk in the
multivariate analysis; when adjusted for the GMFCS level and
the initial migration percentage, the failure risk was not related
to the age at surgery or to the surgery type. Furthermore, when
adjusted for the initial migration percentage, the GMFCS III,
IV, and V groups had a similar failure risk and the risk in each
group was greatly increased compared with the GMFCS II
group. (See Figures 2 and 3 for representative examples of
success and failure.)
Discussion
revious studies have investigated the influence of walking
ability on the outcome of hip adductor surgery in children
with cerebral palsy13,20,25 but, to our knowledge, this is the first
study to analyze adductor surgery outcome according to the
GMFCS level. In our study, the success rate of hip adductor
surgery decreased with increasing baseline migration percentage once this percentage exceeded a threshold of 50%. After
seven years of follow-up, the surgical success rate for children at
GMFCS level II was 94% (thirty-one of thirty-three) compared
with 14% (twenty of 139) for children at level V. Sex and the
type of hip adductor release were not found to have a significant effect on the outcome of the surgery.
Previous studies have shown that the success of adductor surgery may be linked to the migration percentage at
the time of the index surgery19,22,26,30,32,33. In our study, the
success of hip adductor surgery decreased with increasing
baseline migration percentage (>50%). In a recent systematic
review of hip adductor surgery in children with cerebral palsy,
a preoperative migration percentage of <40% was associated
with a successful outcome in 75% to 90% of hips26. Conversely, hips with a migration percentage of >50% had a
poorer outcome, with 75% to 77% of hips remaining subluxated or dislocated26. Only 5% (eleven of 242) of children in
our study had a severe initial migration percentage (‡60%) at
the time of the index surgery, which is similar to the findings
of Presedo et al.20. Whether differences in the initial migration
percentage reflect differences in the natural history or merely
a different stage in the development of hip displacement is
unknown.
The reported percentage of good results of hip adductor
release in children with cerebral palsy ranges from 33%27 to
90%32. This variation in the rate of surgical success is due to
differences among the series with regard to age at the time of
surgery, hip migration percentage, surgical technique, definitions of success and failure, duration of follow-up, and population heterogeneity. Given that preventive surgery, by its
nature, is performed for asymptomatic hip displacement in
order to prevent both later symptoms and the need for more
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invasive surgery, it is appropriate to have a stringent definition
of failure. In our study, the need for additional hip surgery, including revision of soft-tissue releases, was defined as failure.
Patients who demonstrated hip displacement (migration percentage of >50%) or dislocation (migration percentage of >100%)
and had not yet undergone secondary procedures were also included in the failure group. Our overall success rate of 32% (106 of
330) for hip adductor surgery was lower than previously reported
rates for medium to long-term follow-up19,20,33. However, in most
of the previous studies the result for each hip was reported separately18,32,35, and better results will be obtained if each hip is reported as a separate entity. We agree with Turker and Lee19 and
Terjesen et al.33 that a hip that progresses to unilateral subluxation
or dislocation and requires repeat surgery would be considered a
failure by the patient and family.
The duration of follow-up is intimately related to the
surgical success rate. High surgical success rates of approximately 70% have been found in studies with less than five years
of follow-up18,24,25,32,33,35,36. The number of long-term follow-up
studies in the literature is small, and the success rates in these
studies are lower than those in the shorter-term studies. Turker
and Lee19 reported eight-year results for forty-five children with
quadriplegic cerebral palsy treated with soft-tissue surgery for
hip subluxation. They observed a 58% rate of failure, defined as
progressive subluxation or dislocation that eventually resulted
in the need for revision surgery. In comparison, Presedo et al.20
reported the results of soft-tissue surgery in sixty-five patients
with a mean duration of follow-up of 10.8 years. These sixtyfive patients came from an original series of seventy-four patients previously described by Miller et al.25. Presedo et al.20
reported an overall success rate of 67% for adductor surgery;
however, the success rate was 89% for ambulatory subjects and
60% for nonambulatory subjects. In their study, revision softtissue release was not considered a surgical failure; if such revision surgery had been considered a failure, the success rate for
nonambulatory subjects would have been 49%, which is lower
than the 80% success rate after shorter-term follow-up reported by Miller et al.25.
In the present study, the seven-year outcome of soft-tissue
surgery for the treatment of hip displacement was successful in
32% of children. To compare these results with previous studies,
it is necessary to consider differences in GMFCS level and duration of follow-up, which might explain the variability in
reported outcomes. The majority of our patient population
was at GMFCS level IV or V (242 of 330, 73%) (Table I). Soo
et al.2 demonstrated that patients at a higher GMFCS level
have a greater incidence of hip displacement, and our study
suggests that hip displacement is both more severe and more
refractory to surgery in this patient group. Since our study
was population-based, it contained all of the most severely
involved children, who would be classified as being at very
high risk for hip displacement regardless of the intervention.
In the study by Presedo et al.20, forty-seven (72%) of the sixtyfive patients were described as ‘‘spastic quadriplegics,’’ although only one patient died during the ten-year follow-up
period. During our study, nineteen patients died because of
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nonsurgical problems during the seven-year follow-up period. Since there is a strong correlation between the GMFCS
level and the incidence and severity of medical comorbidities,
this again suggests differences in the severity of cerebral palsy
involvement between studies, which provide a potential explanation for the variability in the reported success rate.
The relationship between the success of hip adductor
surgery and the GMFCS level in our study corresponds well with
recent literature on the relationship of GMFCS level to the
prevalence of hip displacement and changes in proximal femoral
geometry in children with cerebral palsy2,37. In nonambulatory
patients with cerebral palsy (GMFCS level IV or V), spastic
muscle imbalance and lack of weight-bearing leads to the development of progressive structural changes around the hip
joint, including retained femoral anteversion, coxa valga, posterolateral acetabular dysplasia, and flexion-adduction hip contractures1,37-44. Likewise, the present study indicated that hips
with severe osseous deformity (GMFCS IV and V) are less likely
to stabilize following soft-tissue surgery alone.
The differences between GMFCS levels III, IV, and V did
not emerge until after approximately thirty-six months postoperatively, and many previous studies with success rates of between 70% to 80% had a duration of follow-up of approximately
thirty-six months18,25,32. Turker and Lee19 stated that a follow-up
duration of at least six years was necessary to determine the
outcome of soft-tissue releases. The Kaplan-Meier plot in Figure
1 illustrates both the value of assessing the success rate according
to the GMFCS level and the need for extended follow-up.
In our study, age at the time of the index surgery was related to surgical success in the univariate analysis but the migration percentage and the GMFCS level completely explained
the surgical success rate in the multivariate analysis. The risk of
hip displacement in children with spastic cerebral palsy is considered to be at its greatest between four and twelve years of age13.
However, previous studies on the importance of age on the
outcome of soft-tissue releases in patients with spastic cerebral
palsy are contradictory. Three studies found better results when
soft-tissue releases were performed in younger children (under
the age of five)1,18,32. In a systematic review of soft-tissue surgery
for hip subluxation in cerebral palsy, Stott and Piedrahita26 found
eleven studies that analyzed age as a variable. Eight of these
studies could not demonstrate a difference related to age at the
time of the surgery19,34,35,38,42,45-47. An association among increased
age at the time of the index surgery, higher GMFCS level, and
surgical failure was noted in our study.
The strengths of this study include the large number of
children with cerebral palsy who were selected from a statewide
Cerebral Palsy Register, their management by a small group of
surgeons with use of standardized protocols, and the reason-
A D D U C T O R S U R G E RY T O P R E V E N T H I P D I S P L A C E M E N T
C H I L D R E N W I T H C E R E B R A L PA L S Y
IN
ably long mean duration of follow-up. The weaknesses of this
study include the four different combinations of adductor releases and the incomplete follow-up of some children.
In conclusion, the success of adductor surgery in children
with cerebral palsy was significantly influenced by the GMFCS
level, in conjunction with the initial migration percentage. Active
GMFCS level-II patients achieved a high rate of success from
isolated hip adductor surgery, whereas GMFCS level-IV and V
patients had higher rates of failure and warrant careful surveillance with long-term follow-up. Classifying children according
to GMFCS level prior to hip adductor surgery provides the
surgeon with more child-specific information with regard to
long-term prognosis and likely surgical outcomes.
On the basis of the results of this study, we now explain to
the families of children at GMFCS level IV or V that although
hip adductor surgery remains our index procedure, it functions
as a temporizing measure and is associated with a higher rate of
failure in such children. Lack of awareness of the high failure
rate of preventive surgery in children who are at GMFCS level
IV or V may lead to an inadequate duration of follow-up, late
presentation for reconstructive surgery, and dissatisfaction
with preventive surgery.
Appendix
An appendix describing the adductor release surgical
protocol is available with the online version of this article
as a data supplement at jbjs.org. n
Benjamin J. Shore, MD, FRCSC
Department of Orthopaedic Surgery,
Children’s Hospital Boston,
Hunnewell 221, 300 Longwood Avenue,
Boston, MA 02115
Xavier Yu, MBBS, BA
Sameer Desai, MS, MRCS(Ed)
Paulo Selber, MD, FRACS
H. Kerr Graham, MD, FRCS(Ed), FRACS
Department of Orthopaedic Surgery (X.Y., S.D., and H.K.G.),
The Hugh Williamson Gait Laboratory (P.S.),
The Royal Children’s Hospital,
Flemington Road, Parkville,
Victoria 3052, Australia
Rory Wolfe, BSc, PhD
Department of Epidemiology and Preventive Medicine,
Monash University, Alfred Hospital,
99 Commercial Road, Melbourne,
Victoria 3004, Australia
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