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Journal of the American Academy of Orthopaedic Surgeons
198
Hip disorders are common in chil-
dren with cerebral palsy and cover a
wide spectrum—from the hip at
risk to subluxation, dislocation, and
dislocation with severe degenera-
tion and pain. Three principles
guide the management of these dis-
orders. First, the pathophysiology
of spastic hip dysplasia differs from
that of developmental dysplasia of
the hip (Table 1). In children with
cerebral palsy, the hips are usually
normal at birth; with growth, how-
ever, a combination of muscle im-
balance and bony deformity leads to
progressive dysplasia. Second, the
natural history of hip dysplasia is
marked by increasing dysfunction.
With progression of hip subluxation
or dislocation, there is an increas-
ingly adverse effect on hygiene, sit-
ting, and gait, as well as pain by
early adulthood for many of those
affected.
1,2
Third, salvage options
for the skeletally mature patient
with a neglected hip are limited.
The care of hip disorders in patients

with cerebral palsy has incorporated
early detection and comprehensive
treatment. This has resulted in
greatly improved outcomes, al-
though certain aspects of the patho-
physiology and management remain
controversial.
Epidemiology and
Natural History
The reported incidence of hip dys-
plasia in patients with cerebral palsy
varies widely, ranging from 2% to
75%.
3
The children with the most
severe neurologic involvement tend
to have the worst hips,
4
and patients
who never achieve the ability to sit
independently have the highest
risk.
5
Lonstein and Beck
6
found
hip subluxation or dislocation in
7% of independent ambulators but
in 60% of dependent sitters. Chil-
dren who can pull themselves to a

standing position by age 3 years
have a better prognosis, with a
lower incidence of hip problems.
5
The natural history of spastic hip
dysplasia varies, but many of the
children who progress to disloca-
tion develop a chronically painful
hip by early adulthood.
1-3
This pro-
gression of dysplasia is gradual,
generally occurring over a period of
several years. Once a hip begins to
subluxate, it rarely improves with-
out treatment. Exceptions include a
hip that becomes the abducted side
in a windblown deformity or a hip
on the low side of the pelvic obliquity
caused by scoliosis. Hips with a
Dr. Flynn is Assistant Professor of Ortho-
paedics, Division of Orthopaedic Surgery, The
Children’s Hospital of Philadelphia, Phila-
delphia, PA. Dr. Miller is Associate Professor
of Orthopaedics, Department of Orthopaedic
Surgery, Alfred I. duPont Institute,
Wilmington, DE.
Reprint requests: Dr. Flynn, The Children’s
Hospital of Philadelphia, 34th and Civic Center
Boulevard, Philadelphia, PA 19104-4399.

Copyright 2002 by the American Academy of
Orthopaedic Surgeons.
Abstract
Hip disorders are common in patients with cerebral palsy and cover a wide clin-
ical spectrum, from the hip at risk to subluxation, dislocation, and dislocation
with degeneration and pain. Although the hip is normal at birth, a combination
of muscle imbalance and bony deformity leads to progressive dysplasia. The
spasticity or contracture usually involves the adductor and iliopsoas muscles;
thus, the majority of hips subluxate in a posterosuperior direction. Many
patients with untreated dislocations develop pain by early adulthood. Because
physical examination alone is unreliable, an anteroposterior radiograph of the
pelvis is required for diagnosis. Soft-tissue lengthening is recommended for
children as soon as discernable hip subluxation (hip abduction <30°, migration
index >25%) is recognized. One-stage comprehensive hip reconstruction is
effective treatment for children 4 years of age or older who have a migration
index >60% but who have not yet developed advanced degenerative changes of
the femoral head. Salvage options for the skeletally mature patient with a
neglected hip are limited.
J Am Acad Orthop Surg 2002;10:198-209
Management of Hip Disorders in
Patients With Cerebral Palsy
John M. Flynn, MD, and Freeman Miller, MD
John M. Flynn, MD, and Freeman Miller, MD
Vol 10, No 3, May/June 2002
199
migration index (MI) >50% do not
reduce spontaneously; approxi-
mately one third will progress to
dislocation.
3

The greatest risk of
dislocation occurs during middle
childhood ages (4 to 12 years). Later
dislocation may be due to unrecog-
nized hydrocephalus or shunt dys-
function.
7
As the hip progresses
from subluxation to dislocation, the
articular cartilage of the femoral
head is subjected to enormous pres-
sure from the surrounding soft tis-
sues and rapidly degenerates.
Dislocated hips are more painful
than hips that remain subluxated or
reduced; subluxated hips are only
slightly more painful than reduced
hips.
3
Anatomy and
Pathophysiology
In children with spastic hip dyspla-
sia, the hip joint is normal at birth.
8
With growth, excessive muscle tone
exerts a constant force on the devel-
oping hip, leading to deformation of
both the proximal femur and acetab-
ulum. Because the spasticity or con-
tracture usually involves the adduc-

tor and iliopsoas muscles, most hips
subluxate in a posterosuperior direc-
tion. The hip’s center of rotation
gradually shifts from the center of the
femoral head to the lesser trochanter.
Femur
The abnormalities of the proxi-
mal femur, including dysplastic and
degenerative changes, persistence of
fetal anteversion, and coxa valga,
have been characterized both radio-
graphically and pathologically. The
spastic hip adductors and flexors
drive the femoral head into the pos-
terolateral acetabular labrum. The
capsule and superior rim of the ace-
tabulum cause focal deformation of
the femoral head. This indentation
locks the femoral head at the lateral
acetabular margin, leading to pain
from cartilage erosion (Fig. 1). The
epiphysis becomes wedge-shaped
and displaces superolaterally. In
one study of three-dimensional
computed tomography (CT) scans,
all nonambulatory patients had
deformities of the femoral head that
ranged from mild medial flattening
to wedge-shaped defects.
9

In most
hips, the lesser trochanter is en-
larged while the greater trochanter
maintains its normal proportions.
Most evidence suggests that in
spastic hip dysplasia, femoral ante-
version is increased. The neck-shaft
angle also may be somewhat higher
in certain children, although most of
the coxa valga seen on radiographs
is caused by the anteversion. Chil-
dren with spastic hip dysplasia
have normal anteversion at birth,
but the normal decrease in antever-
sion does not occur during early
childhood.
Acetabulum
Great progress has been made in
understanding the acetabular ab-
normalities in spastic hip dysplasia.
Computerized mathematical mod-
els demonstrate that a child with
spastic hip disease has a sixfold
increase in hip-force magnitude.
10
This constant abnormal force causes
changes quite early. The acetabular
index (AI) in affected children is
normal until 30 months of age, then
becomes notably higher.

11
Studying
arthrograms, Heinrich et al
12
found
that the bony maturation of the
acetabulum is retarded by deforma-
Table 1
Comparison of Spastic Hip Dysplasia and Developmental
Dysplasia of the Hip
Developmental Dysplasia
Factor Spastic Hip Dysplasia of the Hip
Findings at birth Hip usually normal Hip usually abnormal
Age at risk Usually normal in the first Most often recognized in
year of life; recognized the first year of life
after age 2 yr
Detection Radiographs needed in Physical examination in
most cases most cases
Etiology Spastic muscles drive femoral Mechanical factors
head out of an otherwise (eg, breech), ligamen-
normal acetabulum, pelvic tous laxity, abnormal
obliquity acetabular growth
Childhood Progressive subluxation Progressive subluxation
progression common rare
Natural history Pain in many subluxated or Pain in many subluxated
dislocated hips by second hips by fourth or
or third decade fifth decade
Acetabular Usually posterosuperior Usually anterior
deficiency
Early measures Muscle lengthening Pavlik harness or closed

reduction
Missed or failed Hip osteotomies, often Closed or open reduction,
early measures without open reduction often without osteoto-
mies (before age 18 mo)
Salvage Castle procedure osteotomy, Usually total hip
interposition arthroplasty replacement
Management of Hip Disorders in Patients With Cerebral Palsy
Journal of the American Academy of Orthopaedic Surgeons
200
tion of the lateral pelvic cartilagi-
nous anlage that occurs before or
during the subluxation. The great-
est increase in the deformation of
the acetabulum occurred in hips
with an MI of 52% to 68%.
In most cases, the acetabular defi-
ciency is posterosuperior.
13
Insta-
bility is usually unidirectional, fol-
lowing a trough created by pressure
of the femoral head (Fig. 2). In the
rare cases of extension posturing,
the dislocation and associated ace-
tabular deficiency is anterior. After
analyzing three-dimensional CT
scans, Kim and Wenger
14
confirmed
that the major acetabular deficiency

normally coincided with the direc-
tion of the subluxation or disloca-
tion but stressed that exceptions
occur. There is no agreement as to
whether the acetabulum is actually
shallow
9
or normal in depth.
13
Special Cases
Windblown Hip
Windblown hip describes an
adduction deformity of one hip and
an abduction deformity of the other,
resulting in pelvic obliquity and
pelvic rotation. Windblown hips
are caused by asymmetric activity
of the adductors, abductors, and
internal and external rotator mus-
cles, usually affecting totally in-
volved nonambulatory children
with severe spasticity. Electromyo-
graphic studies have shown that the
adductors are overactive on both
sides, while the abductor is overac-
tive only on the abducted side.
15
The relationship of scoliosis to wind-
blown hips remains controversial.
Black and Griffin

16
studied 80 pa-
tients and concluded that in-
frapelvic obliquity (caused by the
asymmetric muscle forces around
the hip) is more important than
suprapelvic obliquity caused by sco-
liosis. Infrapelvic obliquity occurs
first, and the hip on the infrapelvic
high side is almost always the one
that dislocates.
Anterior Dislocation
Subluxation or dislocation occurs
anteriorly in only 1.5% of cases.
Most of these occur in severe quad-
riplegia with extension posturing or
hypotonia. Three clinical scenarios
have been identified: (1) patients
with hip extension, external rota-
tion, and adduction with knee ex-
tension contractures; (2) patients
with hip extension, external rota-
tion, and abduction with knee flex-
ion contractures; and (3) patients
with severe hypotonia with no con-
tractures.
17
Seating children with
anterior dislocations and contrac-
tures is very difficult. Because of an

associated thoracolumbar kyphosis,
a semirecumbent position is re-
quired. About 50% of children with
anterior dislocations have pain.
17
Physical Examination
During the physical examination of
the hips, abduction should be tested
with the hip and knee extended.
The child with a windblown hip
may have a “pseudo-Galeazzi” sign
due to the one-sided adduction con-
tracture that creates the appearance
of a leg-length discrepancy.
15
Knees
and ankles also should be tested for
range of motion, and the spine
examined for evidence of scoliosis.
If the child is nonambulatory, the
spine and pelvis should be evalu-
ated in the sitting position to assess
pelvic obliquity and its effect on
seating. Physical examination alone
is unreliable to diagnose most pos-
terosuperior spastic hip subluxa-
tions or dislocations. In patients
with anterior dislocations, the fem-
A B
Figure 1 A, Anteroposterior pelvic radiograph of a 17-year-old boy with quadriplegic

cerebral palsy. Constant severe pain in the left, adducted hip worsened after his pelvic
obliquity was corrected with spinal fusion. A Castle femoral resection was done to allow
him to sit comfortably. B, The resected femoral head has a triangular shape and evidence
of advanced degenerative changes, including complete loss of articular cartilage on the
medial, lateral, and superior surfaces.
Figure 2 A three-dimensional reconstruc-
tion of a preoperative CT scan showing
typical posterosuperior dislocation. The
acetabulum is severely dysplastic in the
area of dislocation but normal anteriorly.
John M. Flynn, MD, and Freeman Miller, MD
Vol 10, No 3, May/June 2002
201
oral head may be palpable as a prom-
inent, hard mass in the groin.
Radiologic Evaluation
The supine anteroposterior radio-
graph of the pelvis is used to screen
and follow children at risk for spastic
hip dysplasia. Both the MI and AI
should be measured (Fig. 3). Be-
cause the MI depends on the posi-
tion of the legs, imaging should be
done in neutral adduction/abduction.
The upper limit of normal for the MI
is 25% at age 4 years;
18
however, the
measurement error of the MI is
±10%. Rotation of the pelvis will

decrease the AI on the lower side.
11
Forward pelvic tilt (eg, with a fixed
flexion deformity of the hip) will de-
crease the AI and can make the
femoral/acetabular relationship dif-
ficult to interpret (Fig. 4). To get an
accurate assessment of the acetabu-
lum, the technician should maximal-
ly flex the contralateral hip and knee
to eliminate the lumbar lordosis.
A direct relationship exists be-
tween the MI and AI. The AI stead-
ily increases as the MI increases,
measuring about 40° when the MI is
50%.
8
The shape of the sourcil has
been classified as of two types.
19
In
type 1, the lateral corner is sharp
and below the weight-bearing dome
of the acetabulum (Fig. 3). In type 2,
the lateral corner is blunted, turned
upward, and above the weight-
bearing dome.
In some cases, additional preop-
erative imaging studies may add
valuable information. CT with

three-dimensional reconstruction
allows the surgeon to assess defor-
mities of the femoral head and the
location of the area of greatest
acetabular deficiency (posterosupe-
rior in most, but not all, patients).
Adding a cut through the distal
femur allows calculation of femoral
anteversion. CT with three-dimen-
sional reconstruction is also useful
for accurate analysis of anterior hip
dislocation; the MI may be normal
because these hips do not dislocate
laterally.
17
Real-time ultrasound is
a quick, accurate, and less expen-
sive alternative to measure femoral
anteversion without radiation.
Ultrasound is particularly good in
cases of coxa valga, where CT may
be inaccurate.
Preoperative arthrography does
not help with decision-making in
spastic hip dysplasia. In the child
with spastic hip disease, the hip is
typically normal for the first few
years and the femoral head at the
time of surgery is much more ossi-
fied than it is in a child with devel-

opmental dysplasia. Adequacy of
reduction is easily evaluated without
an arthrogram. By comparison, the
child with developmental dysplasia
of the hip is usually less than 2 years
old with a minimally ossified femoral
head that has been abnormal since in-
fancy. Arthrography in developmen-
tal dysplasia of the hip will outline
the cartilage and show interposed tis-
sue that is blocking reduction.
Nonsurgical Management
Several nonsurgical measures have
been used to prevent or slow the
progression of spastic hip dysplasia.
Physical therapy has traditionally
been used to help preschool-age
children with cerebral palsy reach
their maximum potential. A therapy
program should include activities
designed to maintain hip motion
and promote weight bearing. How-
ever, there is no convincing evi-
dence that therapy alone prevents
hip subluxation. Abduction bracing
does not prevent hip dislocation
20
and, if used aggressively, actually
may cause windblown hips or
hyperabduction deformity.

21
Botu-
linum toxin A can be injected into
the adductors to temporarily de-
crease tone for 4 to 6 months, but no
long-term studies have compared
its efficacy to that of no treatment or
therapy alone. The iliopsoas, a
major factor in spastic hip disease, is
difficult to inject reliably.
The most important facet of non-
surgical management is careful
monitoring. During the preschool
years, hip abduction, with the hips
and knees extended, should be test-
ed and recorded. The MI and AI
Figure 3 Subluxated hip (right side of
illustration). The migration index (MI) is
calculated by dividing the width of the
uncovered femoral head (A) by the total
width of the femoral head (B). The acetab-
ulum is dysplastic (type 2 sourcil), with the
lateral corner of the acetabulum above the
weight-bearing dome. Normal hip (left
side of illustration) with the acetabular
index (AI) indicated. There is a normal
(type 1) sourcil; the lateral corner is sharp
and below the weight-bearing dome. H =
horizontal axis.
Type 1

AI
H
A
B
Type 2
Figure 4 Anteroposterior pelvic radio-
graph of a child with bilateral spastic hip
dislocation shows the difficulty of measur-
ing the AI and MI, or interpreting the rela-
tionship between the femur and the acetab-
ulum, with a severe hip flexion contracture
that tilts the pelvis.
Management of Hip Disorders in Patients With Cerebral Palsy
Journal of the American Academy of Orthopaedic Surgeons
202
should be measured on the antero-
posterior pelvic radiograph. Cere-
bral palsy patients aged 2 through
8 years should have an orthopaedic
examination twice a year. If abduc-
tion of either hip drops below 45°
or the MI is >25%, the hips are at
risk and an anteroposterior pelvic
radiograph should be obtained at
each examination. The physician
should not be lulled into a false
sense of security by a normal radio-
graph of an infant; this may repre-
sent a hypotonic phase before the
pathologic forces have begun to do

their damage.
5
Hip subluxation
typically begins between the ages
of 2 and 6 years.
Caretakers of infants or toddlers
with cerebral palsy often press the
orthopaedic surgeon to estimate the
probability that surgical treatment
of the hips will be needed. Because
so many factors contribute to the
risk of spastic hip dysplasia, there is
sparse evidence to support precise
predictions. Cooke et al
22
retrospec-
tively measured the radiographs of
462 patients with cerebral palsy,
studying the predictive effects of the
AI, MI, and neck-shaft angle. They
found that a high AI was the most
powerful predictor of hip disloca-
tion. All patients with dislocation
had an AI >30° at age 4 years; the
AI was <30° in all patients without
dislocation. However, these data
should be interpreted with caution.
Acetabular dysplasia and pelvic tilt
and rotation complicate the accurate
measurement of AI. Prospective

studies are needed to establish reli-
able guidelines.
Surgical Management
Indications for Surgery
Spastic muscles should be length-
ened early to prevent the devel-
opment of deformity. Early com-
prehensive reconstruction may be
considered if the hip cannot be man-
aged with muscle lengthening. The
natural history of spastic hips sug-
gests that untreated dislocations
may become painful. Reconstruc-
tion or salvage options for a painful
degenerated hip are limited and
generally disappointing.
Soft-Tissue Lengthening
Soft-tissue lengthening should be
done as soon as progressive hip
subluxation is recognized. Damage
to the acetabulum by the pathologic
forces through the femoral head
may be greatest before age 4 years.
5
Soft-tissue lengthening is indicated
in a child less than 8 years of age
who is found to have hip abduction
of <30° and an MI of 25% to 60%
(Fig. 5). Lengthening is contraindi-
cated in a child with no contractures

or spasticity or in a child 4 years of
age or older with subluxation so
advanced that bony reconstruction is
indicated (MI >60% to 100%). How-
ever, lengthening may be appropri-
ate in some cases of severe subluxa-
tion if the child is very young (<4
years of age) or has multiple medical
problems. Although one study
showed that the failure rate in this
age group was 44%, more than half
were successfully treated; in the
remainder, major bony surgery
could be postponed until the bone
stock was more substantial and the
risk of recurrence lower.
23
Soft-tissue lengthening around
the hip is done through a transverse
skin incision made 1 to 3 cm distal
to the inguinal crease. The fascia
over the adductor longus tendon is
opened longitudinally and the ten-
don is transected, taking care to
avoid injury to the anterior branch
of the obturator nerve below. A
myotomy of the gracilis is done
next. If hip abduction has not
improved to 45°, the anterior branch
of the obturator nerve is retracted

and the adductor brevis muscle is
lengthened until 45° of abduction is
obtained. Using the interval be-
tween the adductor brevis and the
pectineus, the iliopsoas tendon is
Figure 5 A, Anteroposterior pelvic radiograph of a 2+6 year-old child with spastic quadriplegia who presented with advanced subluxa-
tion bilaterally. Too young for reconstruction, the child underwent bilateral soft-tissue lengthening. B, Six years after surgery, the hips
are located and the child needed no further hip surgery.
A B
50% 45%
John M. Flynn, MD, and Freeman Miller, MD
Vol 10, No 3, May/June 2002
203
isolated. In nonambulatory patients,
the tendon is divided near the lesser
trochanter. In ambulatory patients,
the iliopsoas tendon is retracted as
far proximally as possible and only
the psoas tendon is divided, leaving
the iliacus fibers intact. A proximal
hamstring lengthening can be
added in nonambulatory patients if
the knee cannot be extended
beyond 45° (popliteal angle >45°).
Neurectomy of the anterior
branch of the obturator nerve
should not be done in ambulatory
patients. The risk of obturator neu-
rectomy is an abduction contrac-
ture—a marked disability for both

walkers and sitters. However, it is
unclear whether the abduction con-
tractures noted in the past were due
to the neurectomy or to the spica
casting and abduction bracing com-
monly used after muscle lengthen-
ing. Obturator neurectomy may be
appropriate in severely involved,
nonambulatory children, but guide-
lines are not yet well established.
Patients are maintained on diaz-
epam (0.1 to 0.2 mg/kg per dose)
every 6 hours to treat the substantial
muscle spasms of the early postop-
erative period. Morphine or co-
deine can be given for pain control.
Although many surgeons still use
spica or abduction casting after
muscle lengthening, our postopera-
tive protocol is designed to allow
immediate therapy. Knee immobi-
lizers and an abduction pillow can
be used for 1 month. On the second
day after surgery, therapy for hip
and knee range of motion is begun.
Prone lying is encouraged to pro-
mote hip extension. Radiographs
are obtained every 6 months. Be-
cause most of the improvement
after soft-tissue lengthening occurs

within 6 months, the radiograph
taken 6 months after surgery is an
excellent indication of eventual suc-
cess or failure.
23
The success of soft-tissue length-
ening is closely related to the degree
of subluxation at the time of the
surgery. Cornell et al
24
found that if
the MI was <40%, soft-tissue length-
ening had an 83% success rate.
With an MI ≥ 40%, soft-tissue sur-
gery alone was successful in only
23% of children. All of the hips with
an MI >60% failed. An AI >27° was
also highly predictive of failure.
Age at the time of surgery did not
have a significant predictive effect.
In a study of 147 hips treated with a
protocol of soft-tissue lengthening
and immediate mobilization with
no abduction bracing, Miller et al
23
found that 88% had a good or fair
result (MI <40%) at final follow-up.
Hip Reconstruction
Indications and Planning
Patient age and severity of sub-

luxation are the two most important
factors to consider in hip recon-
struction. Ideally, hip reconstruc-
tion should be done in patients 4
years of age or older but before per-
manent, advanced degenerative
changes occur. Analyzing the 11- to
18-year follow-up of their hip recon-
structions, Brunner and Baumann
25
found that children less than 4 years
of age had a 96% loss of correction
of the neck-shaft angle. They rec-
ommended that surgery be post-
poned until the child is 8 to 10 years
old, if possible. Furthermore, from
a practical standpoint, older chil-
dren have better bone stock for
plate fixation. The upper age limit
depends on the degree of degenera-
tive changes that develop. Once the
femoral head begins to flatten medi-
ally and laterally, loss of articular
cartilage is probable and pain relief
after reconstruction is unlikely.
Another factor to consider is
severity of subluxation. The capital
femoral epiphysis begins to lose the
support of the bony pelvis at an MI
of approximately 50%.

12
There is a
low probability that soft-tissue
lengthening alone can successfully
reverse the severely compromised
anatomy and mechanics of a hip
with such advanced subluxation.
Thus, hip reconstruction is indicated
for children 4 years of age or older
who have severe subluxation (MI
>60%) or dislocation but who have
not yet developed advanced degener-
ative changes of the femoral head that
are unlikely to remodel. Hip recon-
struction is recommended for chil-
dren less than 8 years old who have
failed soft-tissue lengthening (MI
>40% 1 year postoperative) and for
children more than 8 years old with
an MI >40% but no signs of advanced
degenerative change on radiographs.
Evidence is increasing that the
most effective treatment for the
severely subluxated or dislocated
hip is a one-stage comprehensive
approach that includes soft-tissue
lengthening; a shortening varus
derotation osteotomy of the femur
(VDRO); a capsulotomy when nec-
essary; and a peri-ilial acetabu-

loplasty.
1,19,25,26
The soft-tissue
lengthening is done initially to
achieve at least 45° of hip abduction;
otherwise, the varus osteotomy
would result in adduction. Shorten-
ing may be the most important com-
ponent of the VDRO. Computer-
ized mathematical models show
that to normalize the mechanical
forces of the spastic hip, one must
lengthen the psoas, iliacus, gracilis,
and adductor longus and brevis
muscles, which can reduce the force
on the joint to near normal. The
benefit of VDRO comes not from
the redirection of force but from the
bone shortening that acts like a
muscle release or lengthening. De-
creasing femoral anteversion, neck-
shaft angle, or both have little effect
on the forces.
10
The indications for a
capsulotomy are not well estab-
lished. McNerney et al
26
recom-
mended an open reduction and cap-

sulorrhaphy on every hip with an
MI >70%; they found that only 3%
of such hips resubluxated after open
reduction and capsulorrhaphy,
while 60% resubluxated when the
procedure was not done. Miller et
Management of Hip Disorders in Patients With Cerebral Palsy
Journal of the American Academy of Orthopaedic Surgeons
204
al
19
recommended medial capsulot-
omy when abduction is <20° and
the whole femoral head does not
reduce under the acetabulum after
the pelvic osteotomy.
The acetabulum has a very limited
ability to remodel once advanced
dysplasia has developed.
11
Al-
though the surgeon can choose from
several different pelvic osteotomies
to address such dysplasia, varia-
tions of the Dega acetabuloplasty
have proved to be best.
1,19,26
The
acetabuloplasty should be done in
all dislocated hips. In subluxated

hips, the surgeon should consider
both the AI and the shape of the
sourcil. When the AI is ≥ 25°
26
or
when there is a type 2 sourcil,
19
an
acetabuloplasty should be done
(Fig. 6). Acetabuloplasty is relatively
contraindicated if the triradiate car-
tilage is closed or if advanced de-
generative changes have developed
in the femoral head.
Technique
When hip abduction is <45°, a
soft-tissue lengthening is done first.
The femoral osteotomy is designed
to achieve a neck-shaft angle of
approximately 100° in nonambulato-
ry and 120° in ambulatory patients.
19
Because the protocol includes imme-
diate mobilization and therapy, the
femur must be rigidly fixed (eg, a 90°
blade plate). In nonambulators or
household ambulators, the level of
the osteotomy is planned so that the
entire lesser trochanter is removed,
effecting a release of the iliopsoas. In

community ambulators, the lesser
trochanter is kept with the proximal
fragment and the iliopsoas is pre-
served by a more proximal lengthen-
ing. With the chisel for the blade
plate in place, the proximal femur is
abducted. If the femoral head does
not reduce into the acetabulum, a
medial and anterior capsulotomy is
done and any other blocks to reduc-
tion are addressed.
The acetabular osteotomy is done
through an anterior approach in the
interval between the sartorius and
tensor fascia lata. The edge of the
hip capsule is cleared, beginning
anteriorly near the anteroinferior
iliac spine and working all the way
posterior to the triradiate cartilage,
taking care to avoid exposing or
entering the sciatic notch. Under
fluoroscopic guidance, a straight
osteotome is used to create a peri-
capsular cut in the ilium 5 mm
above the joint. This osteotomy
extends from the anterior-inferior
iliac spine to the triradiate cartilage
but does not extend into the sciatic
notch. The osteotome, placed as
posteriorly as possible in the oste-

otomy, is used to lever open the os-
teotomy (Fig. 7, A). In most cases,
the maximum acetabular deficiency
is posterosuperior, so the triangular
piece of iliac crest allograft is tapped
into the osteotomy as posteriorly as
possible, thus making the maximum
coverage in the area of greatest dys-
plasia (Fig. 7, B).
With the acetabular osteotomy
complete, the femur can be fixed. To
judge the amount of femoral short-
ening needed, the popliteal angle is
a good gauge. With the hip flexed
90° and the knee fully extended
(popliteal angle = 0°), the amount of
femoral overlap is marked. Usually
between 1 and 3 cm is removed, and
the femoral shaft is fixed to the blade
plate. The shortening decreases the
remaining force on the joint caused
by contracted muscles, including the
hamstrings. In ambulatory patients,
a distal hamstring lengthening can
be done prior to the femoral osteoto-
my to reduce the amount of femoral
shortening needed. If both hips are
being reconstructed, leg lengths can
be equalized when the second side is
shortened. Anteversion should be

corrected to between 0° and 15°.
Overzealous derotation will leave
the hip retroverted, increasing the
risk of posterior dislocation.
The postoperative regimen in-
cludes the use of diazepam and
narcotics, similar to the muscle-
lengthening procedure. With stable
fixation, no cast or orthotic is needed.
When a cast is used (eg, if fixation
seems inadequate or regular post-
operative therapy is not available),
the surgeon should be vigilant for
skin problems, pulmonary compli-
cations (eg, pneumonia), and insuf-
ficiency fractures after cast removal.
Sitting and therapy for range of
Figure 6 A, Anteroposterior pelvic radiograph of advanced hip subluxation (65%) in a 7-
year-old child. The acetabulum is dysplastic with a type 2 sourcil. B, The same patient
after one-stage reconstruction with adductor lengthening, a shortening VDRO with blade
plate fixation, and acetabuloplasty.
A B
John M. Flynn, MD, and Freeman Miller, MD
Vol 10, No 3, May/June 2002
205
motion can begin on the second
postoperative day, and standing can
begin as early as 1 week as comfort
permits. Several months of therapy
for range of motion and gait training

is recommended. Symptomatic plates
can be removed once the osteotomy
heals.
The one-stage comprehensive
approach (Fig. 8) has yielded excel-
lent results. Using the comprehen-
sive technique, 95% of hips were
stable more than 2 years after sur-
gery, 82% were pain free, 14% had
partial relief, and 4% had persistent
pain.
19
Others
1,26,27
have reported
similar excellent results. Persistent
pain is more likely when preopera-
tive radiographs show lateral fem-
oral head flattening.
19
Special Cases
Windblown Hip
The windblown hip remains a
difficult clinical problem. Unilateral
adductor lengthening is recom-
mended for windblown hips to
avoid unilateral abduction and a
pelvis that is impossible to con-
trol;
5,15

however, the failure rate is
high. Abel et al
28
reported failure in
one third of patients, noting that
hyperabduction may occur after an
ipsilateral adductor release unmasks
the abduction tone. Bilateral recon-
struction with varus shortening
osteotomies (VDRO) gives symme-
try of appearance and motion. Al-
though recurrence can be seen with
growth, bilateral reconstruction is
much more likely to give lasting
improvement than soft-tissue proce-
dures.
28
Anterior Dislocation
For an anterior hip dislocation,
the indications for reconstruction
are pain and difficulty with sitting.
The knee flexion or extension con-
tractures should be addressed with
muscle lengthening. The hip recon-
struction includes a varus shorten-
ing femoral osteotomy (VDRO) and
a Pemberton-type osteotomy to cre-
ate good anterior coverage.
17
Selva

et al
17
reported a good outcome in
11 of 13 patients. The authors felt
that results in posterior dislocations
were better because anterior dislo-
cations are so rare and the affected
children have severe neurologic in-
volvement.
Hip Subluxation After Selective
Dorsal Rhizotomy
Children may develop progres-
sive hip subluxation after selective
dorsal rhizotomy. Generally, there
is no adduction contracture. Non-
ambulatory children with preexist-
ing dysplasia are most at risk and
should be followed after rhizotomy
with a radiograph of the hip each
year for several years. When pro-
gressive subluxation is noted, a hip
reconstruction should be done;
however, lengthening of the adduc-
tors usually is not needed.
Salvage Procedures
If muscle lengthening does not
succeed in treating subluxation,
one-stage comprehensive hip recon-
struction has achieved a reported
success rate >90%. Thus, with an-

nual monitoring and appropriately
timed surgery, few hips should
need a salvage procedure. How-
ever, many adolescents with cere-
bral palsy still present with a pain-
ful dislocated hip and advanced
degenerative changes. They are
often unable to sit comfortably and
may have skin breakdown and poor
perineal hygiene. The basic types of
femoral salvage options are re-
section, redirection, interposition-
replacement, and arthrodesis. Some
surgeons have successfully used a
Chiari osteotomy or shelf arthro-
plasty for late treatment of hips not
amenable to a peri-ileal osteotomy.
Among the various types of fem-
oral resection, the Castle procedure
has produced the best results for a
painful spastic hip dislocation with
degenerative changes in the femoral
head.
29
Using an extraperiosteal
dissection, the femoral head is re-
sected distal to the lesser trochanter.
The rectus and vastus lateralis mus-
cles are sewn over the remaining
femoral shaft, and the gluteal mus-

Sciatic
notch
Anterior-
inferior
iliac spine
Ischium
Pubis
Bone
grafts
Figure 7 Acetabuloplasty technique. A, The osteotome is used to open the osteotomy at
the site of maximum deformity (usually posterosuperior), and the largest piece of graft is
placed in this position. B, Completed acetabuloplasty, with the graft in place.
A B
Management of Hip Disorders in Patients With Cerebral Palsy
Journal of the American Academy of Orthopaedic Surgeons
206
cles are interposed between the fe-
mur and the acetabulum. Although
the original recommendations in-
cluded 6 weeks of postoperative
skeletal traction, no evidence sup-
ports the necessity of 6 weeks. A
few days in traction, with or with-
out a few weeks of abduction cast-
ing or bracing, may be as successful
and more practical. Postoperative
pain often persists for 9 to 12 months
before resolving. Some surgeons
recommend measures to prevent
heterotopic ossification (HO). In a

series reported by McCarthy et al,
4
12 of 56 hips had HO, but all pa-
tients were able to sit. The Castle
procedure is contraindicated in
patients who have not reached
skeletal maturity; younger patients
can have excessive proximal migra-
tion of the femoral shaft and persis-
tent pain.
4
Another salvage option for non-
ambulatory patients is a redirection-
al osteotomy. In a child with severe
adduction but no pain, a valgus
osteotomy (at least 60°) can put the
legs in a more abducted position,
allowing for improved perineal care.
McHale et al
30
described a procedure
in which the femoral head is resect-
ed and a subtrochanteric valgus
osteotomy is used to direct the lesser
trochanter into the acetabulum and
the remaining femoral shaft away
from the pelvis. There was good
pain relief in six hips.
Other salvage options include
arthrodesis and arthroplasty. In

patients who might be candidates
for a Castle procedure but who are
skeletally immature, a total shoul-
der prosthesis has been used as an
interposition arthroplasty
31
(Fig. 9).
In one series of eight arthrodeses,
six were considered successful, yet
seven patients had complications,
including pseudarthrosis in two.
32
Root et al
32
had 13 successful total
hip replacements in a series of 15
but noted problems with recurrent
dislocations, loosening, bending of
the prosthesis, and proximal migra-
tion of the greater trochanter. More
recently, Buly et al
33
reported long-
term pain relief and an 86% 10-year
survival rate of total hip replace-
ments in 18 patients ranging from
16 to 52 years old. They used selec-
tive tendon releases and spica casts
to reduce the risk of dislocation.
HO occurred in 58% of patients but

did not seem to have a major clini-
cal impact. Total hip replacement
should be reserved for skeletally
mature, highly functional ambula-
tors whose hips have advanced
degenerative changes precluding
reconstruction.
Complications
While hip reconstruction or sal-
vage carry the attendant risks of any
major surgery, additional complica-
tions are associated with the severe-
ly involved child. Stasikelis et al
34
found complications in 68% of pa-
tients with gastrostomy or trache-
ostomy tubes but in only 12% of
those without; complications oc-
curred in 29% of nonambulators but
in only 8% of ambulators. Compli-
cations after hip osteotomy oc-
A
C
B
Figure 8 A, Preoperative anteroposterior radiograph of a 9-year-
old patient who had a complete left hip dislocation and pain. B,
Both hips were reconstructed (left—comprehensive reconstruc-
tion, right—VDRO to balance rotation, adduction, and leg
lengths). C, Ten years postoperatively, both hips remained well
reduced and the patient was pain free.

John M. Flynn, MD, and Freeman Miller, MD
Vol 10, No 3, May/June 2002
207
curred in 25% of the 79 patients
studied, with postoperative death in
3 patients. Most of these complica-
tions were fractures or decubitus
ulcers, which may be attributable to
postoperative casting. In our expe-
rience with more than 400 hip
reconstructions without postopera-
tive casting, there have been no
deaths, and fractures and skin
breakdown are rare even in the
most seriously involved children.
Complications after hip surgery
in cerebral palsy can result from the
procedure or the aftercare. Matsuo
et al
35
studied the effect of obturator
neurectomy and found hyperabduc-
tion in the group that had under-
gone neurectomy. They and other
investigators stress the importance
of preserving the adductor brevis
muscle and its nerve supply, espe-
cially in ambulatory patients.
The reported incidence of osteo-
necrosis of the femoral head in chil-

dren after hip reconstruction ranges
from 0% to 11%.
1,19,26
The blood
supply might be compromised
either by the femoral osteotomy, as
a result of increased pressure on the
femoral head, or during psoas tenot-
omy.
1
An adequate femoral short-
ening may play a key role in pre-
vention,
1
just as in reconstruction
for developmental dysplasia of the
hip in older children. Fortunately,
osteonecrosis rarely has a notably
adverse effect on results; in most
cases, the hips are still mobile and
pain free.
HO is commonly seen in radio-
graphs within a few months of hip
surgery. In a review of 192 patients
with cerebral palsy, Krum and
Miller
36
noted that HO was particu-
larly severe in the few patients who
had both hip and spine surgery

within a short period of time. In the
group who had hip adductor length-
ening, mild to moderate HO was
noted in 21 of 61 patients; however,
2 of 5 patients who had both a spine
fusion and hip soft-tissue lengthen-
ing had severe, painful HO that
required surgical treatment. Unex-
plained irritability or motion loss
several weeks after surgery may be
the first indication of its occurrence.
Many protocols have been suggested
to prevent HO. Anti-inflammatory
medications, such as aspirin and in-
domethacin, have not been reliable
in preventing HO in patients with
cerebral palsy. Radiation therapy to
the area at risk on the second or
third postoperative day (either a sin-
gle dose or a divided dose on se-
quential days) has been more suc-
cessful. Occasionally, it can be so
debilitating that surgical interven-
tion is necessary.
Many children with cerebral
palsy, particularly nonambulators,
have decreased bone density. They
are at a particularly high risk for
insufficiency fractures if their post-
operative regimen includes spica

casting. In the few weeks after cast
removal, fractures may occur with
transfers or in physical therapy. The
most common fracture site is the dis-
tal femur. To decrease the risk of
postimmobilization fractures and to
minimize stiffness and prolonged
loss of function, many centers have
abandoned the use of postoperative
spica casting altogether. Miller et al
used immediate mobilization after
hip reconstruction and had a 4%
fracture rate, much lower than the
10% to 29% noted in patients treated
with spica casts.
19
Improved nutri-
tion, careful therapy, and limited
immobilization will help minimize
fracture risk in this vulnerable popu-
lation.
Summary
Managing spastic hip dysplasia is
an important part of caring for chil-
dren with cerebral palsy. Because
the natural history of dislocations is
often pain by young adulthood, and
because the salvage options at that
stage are limited, the goal is careful
screening and early treatment. Hip

A B
Figure 9 A, Anteroposterior radiograph of a 19-year-old man who had severe pain after
an unsuccessful Girdlestone femoral resection. Note the extent of the proximal migration
of the femur. B, The same patient 3 years after a total shoulder prosthesis was used as an
interposition arthroplasty. The patient remained pain free.
Management of Hip Disorders in Patients With Cerebral Palsy
Journal of the American Academy of Orthopaedic Surgeons
208
subluxation typically begins be-
tween the ages of 2 and 6 years and
is most common in children with
the most severe cerebral palsy. Hip
abduction, with the hips and knees
extended, should be tested and
recorded, and the MI and AI should
be measured on the anteroposterior
pelvic radiograph. Nonsurgical
measures have not been successful in
preventing progression. Soft-tissue
lengthening should be done early,
as soon as hip subluxation is recog-
nized.
Early comprehensive recon-
struction is indicated if the hip can-
not be adequately treated with
muscle lengthening. Increasing
evidence supports the efficacy of
one-stage comprehensive treatment
for the severely subluxated or dis-
located hip. The approach includes

soft-tissue lengthening; a shorten-
ing VDRO of the femur; and a peri-
ilial acetabuloplasty. A capsuloto-
my may be needed to adequately
reduce the hip. Ideally, hip recon-
struction should be done in patients
4 years of age or older but before
permanent, advanced degenerative
changes develop. A postoperative
protocol that emphasizes immedi-
ate mobilization and therapy, as tol-
erated, lowers the incidence of
insufficiency fractures and other
complications.
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