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Journal of the American Academy of Orthopaedic Surgeons 198 Hip disorders are common in children with cerebral palsy and cover a wide spectrum—from the hip at risk to subluxation, dislocation, and dislocation with severe degeneration and pain. Three principles guide the management of these disorders. 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, however, a combination of muscle imbalance 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, sitting, 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, although certain aspects of the pathophysiology and management remain controversial. Epidemiology and Natural History The reported incidence of hip dysplasia 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 dislocation develop a chronically painful hip by early adulthood. 1-3 This progression of dysplasia is gradual, generally occurring over a period of several years. Once a hip begins to subluxate, it rarely improves without 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 clinical 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; approximately 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 dysfunction. 7 As the hip progresses from subluxation to dislocation, the articular cartilage of the femoral head is subjected to enormous pressure 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 dysplasia, 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 acetabulum. Because the spasticity or contracture usually involves the adductor and iliopsoas muscles, most hips subluxate in a posterosuperior direction. The hip’s center of rotation gradually shifts from the center of the femoral head to the lesser trochanter. Femur The abnormalities of the proximal 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 acetabulum 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 anteversion 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 anteversion does not occur during early childhood. Acetabulum Great progress has been made in understanding the acetabular abnormalities in spastic hip dysplasia. Computerized mathematical models 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 osteotomies (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 greatest increase in the deformation of the acetabulum occurred in hips with an MI of 52% to 68%. In most cases, the acetabular deficiency 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 acetabular deficiency is anterior. After analyzing three-dimensional CT scans, Kim and Wenger 14 confirmed that the major acetabular deficiency normally coincided with the direction of the subluxation or dislocation 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 muscles, usually affecting totally involved nonambulatory children with severe spasticity. Electromyo- graphic studies have shown that the adductors are overactive on both sides, while the abductor is overactive only on the abducted side. 15 The relationship of scoliosis to windblown hips remains controversial. Black and Griffin 16 studied 80 patients and concluded that infrapelvic obliquity (caused by the asymmetric muscle forces around the hip) is more important than suprapelvic obliquity caused by scoliosis. 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 quadriplegia with extension posturing or hypotonia. Three clinical scenarios have been identified: (1) patients with hip extension, external rotation, and adduction with knee extension contractures; (2) patients with hip extension, external rotation, and abduction with knee flexion contractures; and (3) patients with severe hypotonia with no contractures. 17 Seating children with anterior dislocations and contractures is very difficult. Because of an associated thoracolumbar kyphosis, a semirecumbent position is required. 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 contracture 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 evaluated in the sitting position to assess pelvic obliquity and its effect on seating. Physical examination alone is unreliable to diagnose most posterosuperior 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 reconstruction 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 radiograph 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 position 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 decrease the AI and can make the femoral/acetabular relationship difficult to interpret (Fig. 4). To get an accurate assessment of the acetabulum, the technician should maximal- ly flex the contralateral hip and knee to eliminate the lumbar lordosis. A direct relationship exists between 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 preoperative imaging studies may add valuable information. CT with three-dimensional reconstruction allows the surgeon to assess deformities of the femoral head and the location of the area of greatest acetabular deficiency (posterosuperior in most, but not all, patients). Adding a cut through the distal femur allows calculation of femoral anteversion. CT with three-dimensional 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 ossified than it is in a child with developmental 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 developmental dysplasia of the hip will outline the cartilage and show interposed tissue 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 evidence 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 decrease 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 nonsurgical management is careful monitoring. During the preschool years, hip abduction, with the hips and knees extended, should be tested 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 acetabulum 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 radiograph of a child with bilateral spastic hip dislocation shows the difficulty of measuring the AI and MI, or interpreting the relationship between the femur and the acetabulum, 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 anteroposterior pelvic radiograph. Cere- bral palsy patients aged 2 through 8 years should have an orthopaedic examination twice a year. If abduction 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 radiograph 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 dislocation. 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 reliable guidelines. Surgical Management Indications for Surgery Spastic muscles should be lengthened early to prevent the devel- opment of deformity. Early comprehensive reconstruction may be considered if the hip cannot be man- aged with muscle lengthening. The natural history of spastic hips suggests 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 contraindicated 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 appropriate in some cases of severe subluxation 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 tendon 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 between 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 subluxation 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 neurectomy is an abduction contracture—a marked disability for both walkers and sitters. However, it is unclear whether the abduction contractures noted in the past were due to the neurectomy or to the spica casting and abduction bracing commonly used after muscle lengthening. Obturator neurectomy may be appropriate in severely involved, nonambulatory children, but guidelines are not yet well established. Patients are maintained on diazepam (0.1 to 0.2 mg/kg per dose) every 6 hours to treat the substantial muscle spasms of the early postoperative period. Morphine or co- deine can be given for pain control. Although many surgeons still use spica or abduction casting after muscle lengthening, our postoperative 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 promote 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 success or failure. 23 The success of soft-tissue lengthening 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 lengthening had an 83% success rate. With an MI ≥ 40%, soft-tissue surgery 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 subluxation are the two most important factors to consider in hip reconstruction. Ideally, hip reconstruction 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 reconstructions, 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 recommended that surgery be postponed until the child is 8 to 10 years old, if possible. Furthermore, from a practical standpoint, older children have better bone stock for plate fixation. The upper age limit depends on the degree of degenerative 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 degenerative changes of the femoral head that are unlikely to remodel. Hip reconstruction is recommended for children 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 necessary; and a peri-ilial acetabuloplasty. 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 established. McNerney et al 26 recommended an open reduction and capsulorrhaphy 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 capsulotomy 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 cartilage is closed or if advanced degenerative 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 nonambulatory and 120° in ambulatory patients. 19 Because the protocol includes immediate 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 lengthening. 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 reduction 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 osteotomy, is used to lever open the osteotomy (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 dysplasia (Fig. 7, B). With the acetabular osteotomy complete, the femur can be fixed. To judge the amount of femoral shortening 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 osteotomy 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 includes 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 postoperative therapy is not available), the surgeon should be vigilant for skin problems, pulmonary complications (eg, pneumonia), and insufficiency 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 excellent results. Using the comprehensive technique, 95% of hips were stable more than 2 years after surgery, 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 preoperative radiographs show lateral femoral head flattening. 19 Special Cases Windblown Hip The windblown hip remains a difficult clinical problem. Unilateral adductor lengthening is recommended for windblown hips to avoid unilateral abduction and a pelvis that is impossible to control; 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 reconstruction 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 procedures. 28 Anterior Dislocation For an anterior hip dislocation, the indications for reconstruction are pain and difficulty with sitting. The knee flexion or extension contractures should be addressed with muscle lengthening. The hip reconstruction includes a varus shortening femoral osteotomy (VDRO) and a Pemberton-type osteotomy to create 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 dislocations are so rare and the affected children have severe neurologic involvement. Hip Subluxation After Selective Dorsal Rhizotomy Children may develop progressive 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 progressive subluxation is noted, a hip reconstruction should be done; however, lengthening of the adductors usually is not needed. Salvage Procedures If muscle lengthening does not succeed in treating subluxation, one-stage comprehensive hip reconstruction 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 cerebral palsy still present with a painful 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 resection, redirection, interposition- replacement, and arthrodesis. Some surgeons have successfully used a Chiari osteotomy or shelf arthroplasty for late treatment of hips not amenable to a peri-ileal osteotomy. Among the various types of femoral 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 resected distal to the lesser trochanter. The rectus and vastus lateralis muscles 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 femur 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 without a few weeks of abduction casting 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 patients were able to sit. The Castle procedure is contraindicated in patients who have not reached skeletal maturity; younger patients can have excessive proximal migration of the femoral shaft and persistent pain. 4 Another salvage option for nonambulatory 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 resected 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 shoulder 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 migration 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 replacements in 18 patients ranging from 16 to 52 years old. They used selective 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 clinical impact. Total hip replacement should be reserved for skeletally mature, highly functional ambulators whose hips have advanced degenerative changes precluding reconstruction. Complications While hip reconstruction or salvage carry the attendant risks of any major surgery, additional complications are associated with the severely involved child. Stasikelis et al 34 found complications in 68% of patients with gastrostomy or trache- ostomy tubes but in only 12% of those without; complications occurred 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 reconstruction, 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 complications were fractures or decubitus ulcers, which may be attributable to postoperative casting. In our expe- rience with more than 400 hip reconstructions without postoperative 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 hyperabduction 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 osteonecrosis of the femoral head in children 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 shortening 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 radiographs within a few months of hip surgery. In a review of 192 patients with cerebral palsy, Krum and Miller 36 noted that HO was particularly 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 lengthening, 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 lengthening 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 successful. 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 postoperative 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 distal 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 children 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.

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