David A. Podeszwa
Developmental dysplasia of the hip (DDH) is a spectrum of disorders of the developing hip. DDH evolves over time and presents in different forms at different ages. DDH may not be detectable at birth, and hence, the preferred term developmental and not congenital. The American Academy of Pediatrics (AAP) defines DDH as a condition in which the femoral head has an abnormal relationship to the acetabulum.1 Dislocation is defined as complete displacement of a joint, with no contact between the original articular surfaces. Subluxation is defined as displacement of a joint with some contact remaining between the articular surfaces. Dysplasia refers to abnormal or deficient development of the acetabulum. A teratologic dislocation is a distinct condition that occurs before birth, is generally nonreducible on physical exam, and causes the hip to be stiff. Teratologic dislocations are frequently associated with neuromuscular conditions, particularly arthrogryposis and myelodysplasia, and treatment depends on the underlying condition.
The incidence of DDH varies based on the condition studied, method of study (clinical exam vs. radiologic exam), race, and geography. Classically, the overall incidence of some form of hip instability has been reported at 1 per 1000.2 The reported rate of hip dislocation ranges from 1 to 1.5 cases per 1000 live births. Clinical instability has been documented in approximately 2.3 cases per 100 live births, and an ultrasound abnormality has been documented in approximately 8 cases per 100 live births. Bilateral DDH occurs in 20% of all patients with this disorder.
As breech positioning can be considered a “packaging” issue (intrauterine crowding) predisposing to DDH, torticollis, metatarsus adductus, and oligohydramnios are other packaging-related conditions strongly associated with DDH. A child with torticollis has a 14% to 20% risk of also having DDH.3 Although clubfoot has not been strongly associated with DDH, up to 10% of children with metatarsus adductus will also have DDH.4 DDH is more common in females and first-born children, and most frequently affects the left hip. Family history also strongly influences the risk of DDH. The risk of a subsequent child having DDH is 6% if there are healthy parents and an affected child, 12% with an affected parent, and 35% with an affected parent and an affected child.
ETIOLOGY
The etiology of DDH is multifactorial, but a number of predisposing factors have been identified, including ligamentous laxity, breech positioning, and postnatal positioning. The maternal relaxin hormone, which allows the maternal pelvis to expand, crosses the placenta and can induce laxity in the child, an effect known to be stronger in females than in males. The footling breech presentation (both hips flexed) is associated with a 2% risk of DDH, and the frank breech position (one or both knees extended) is associated with a 20% risk of DDH.5 Newborn babies wrapped in a hip-extended position, common in the Native American culture, also have a higher incidence of DDH.
CLINICAL FEATURES
The clinical evaluation and diagnosis of DDH can be difficult and can change over time. Thus, close follow-up and documentation of the physical exam are critical. The American Academy of Pediatrics (AAP) recommends a hip exam at 2 weeks, 2 months, 4 months, 6 months, 9 months, and 1 year. The physical exam findings will vary depending on the age of the child and the severity of the condition. The stability of the hip in the neonate is clinically diagnosed by performing the Barlow and Ortolani maneuvers. In the neonatal period, these maneuvers are generally the only physical exam finding suggestive of DDH. These maneuvers are best performed with the child placed supine on a warm, firm surface. The child and examiner must be as relaxed as possible. Dimming the room lights or feeding the child a bottle will often help. If the child is fussy or the examiner is impatient, the exam will be inaccurate.
The examiner holds the child’s knees, one in each hand, with the fingers of the examiner over the greater trochanter and the thumb placed along the inner thigh. The hips are examined one at a time. The Barlow test (Fig. 215-1) is an attempt to dislocate the femoral head from within the acetabulum. With the hip flexed 90° with neutral rotation, the hip is adducted and pressure is applied in a posterior direction as an attempt to slide the hip posteriorly out of the acetabulum. With a positive test, the hip will slide posteriorly out of the acetabulum and will be felt to slip back as the posterior pressure is relaxed. The Ortolani test (Fig. 215-2) is an attempt to reduce a dislocated femoral head back into the acetabulum (the opposite of the Barlow maneuver). With the hip flexed 90° and in neutral rotation, the hip is abducted while simultaneously the ring and small fingers are used to gently lift the greater trochanter. When the test is positive, a “clunk” will be felt as the femoral head slides back into the acetabulum. Both of these maneuvers should be repeated multiple times as a smooth arc of motion before proceeding to the opposite hip.
FIGURE 215-1. The Barlow test for developmental dislocation of the hip in a neonate. A: With the infant supine, the examiner holds both of the child’s knees and gently adducts one hip and pushes posteriorly. B: When the examination is positive, the examiner will feel the femoral head make a small jump (arrow) out of the acetabulum (Barlow’s sign). When the pressure is released, the head is felt to slip back into place. (Reprinted with permission from Tachdjian’s Pediatric Orthopaedics, 4th Edition, edited by John A. Herring.)
FIGURE 215-2. The Ortolani test for developmental dislocation of the hip in a neonate. A: The examiner holds the infant’s knees and gently abducts the hip while lifting up on the greater trochanter with two fingers. B: When the test is positive, the dislocated femoral head will fall back into the acetabulum (arrow) with a palpable (but not audible) “clunk” as the hip is abducted (Ortolani’s sign). When the hip is adducted, the examiner will feel the head redislocate posteriorly. (Reprinted with permission from Tachdjian’s Pediatric Orthopaedics, 4th Edition, edited by John A. Herring.)
In the infant (greater than 3 months of age), more specific physical exam findings of the dislocated hip will appear, such as limited hip abduction and a more proximal location of the greater trochanter. The Galeazzi sign, highly suggestive of developmental dysplasia of the hip, is a relative shortening of the thigh when comparing the height of the knees with both hips flexed 90°. With a unilateral dislocation, the thigh will be foreshortened, resulting in additional thigh folds on the affected side. However, extra thigh folds are a normal variant and do not necessarily indicate a hip dislocation. Limitation of abduction, the most reliable sign of a dislocated hip, is best appreciated by abducting both hips simultaneously with the child on a firm surface. The dislocated side will have a distinct reduction in abduction as compared to the healthy side.
The evaluation of the infant with bilateral hip dislocations can be difficult. There may be symmetric abduction and similar thigh lengths with the Galeazzi test. The Klisic test is performed by placing the middle finger on the greater tro-chanter and the index finger on the anterior superior iliac spine. Normally, an imaginary line drawn between the two fingers will point at the umbilicus. If the hip is dislocated, the line will point between the umbilicus and the pubis.
The physical findings in a child of walking age with a unilateral dislocated hip may include decreased abduction of the affected hip, a positive Klisic test, a positive Galeazzi sign, a limp, and a leg length discrepancy. A walking patient with bilateral hip dislocations often presents only with a complaint of increased lumbar lordosis (sway back) secondary to bilateral hip flexion contractures but may also have a lurching gait on both sides.
The neonate’s femoral head and acetabulum are primarily cartilaginous, making conventional radiographs difficult to interpret. Ultra-sonography visualizes the soft tissue structures of the hip and the relationship of the femoral head and acetabulum very well.6 The AAP recommends ultrasonography for female infants either carried breech or with a positive family history for developmental dysplasia of the hip.1 An infant with a positive Ortolani or Barlow sign does not require an immediate ultrasound but should be referred to a pediatric orthopedic surgeon for treatment. Plain radiographs become useful at 3 to 6 months of age when the femoral head begins to ossify.
TREATMENT
The Pavlik harness (Fig. 215-3) is the first choice of treatment for patients less than 6 months with an unstable hip or hip dislocation.7 The harness should hold the hip in more than 90° of flexion. If the hip cannot be placed into this position, the treatment will fail. The hip, however, does not have to be reducible at the time of the examination to be successfully treated with the harness. The child should be evaluated weekly with clinical and ultrasound exams to document the reduction of the femoral head. If the femoral head is not reduced within 3 to 4 weeks, the harness is abandoned. If the hip successfully reduces, the harness is continued for an additional 6 to 12 weeks.
For the child between 6 months and 2 years of age who presents with a dislocated hip or who has failed initial harness treatment, the goal of treatment is to obtain and maintain a concentric reduction of the hip without damaging the femoral head. This is most often done with an adductor tenotomy, closed reduction and application of a spica cast in the “human position,” or by an open reduction of the hip. The child who presents over 2 years of age with a dislocated hip usually requires an open reduction, a femoral shortening osteotomy, and a pelvic osteotomy to correct the persistent femoral and acetabular bony deformities. Follow-up to skeletal maturity is essential as persistent acetabular dysplasia may be present despite the perfect execution of prior treatments at any age. Avascular necrosis of the femoral head is the most significant complication associated with the treatment of developmental dysplasia of the hip and can occur as the result of any nonoperative or operative treatments.
LEGG-CALVÉPERTHES DISEASE
Legg-Calvé-Perthes disease (LCPD), a common cause of avascular necrosis of the femoral head in children, is a condition in which the vascular supply to part or all of the femoral head is disrupted leading to the cessation of femoral head growth and increased femoral head density. The dense bone is subsequently resorbed and replaced by new bone. However, during this process the mechanical properties of the femoral head are altered, typically resulting in enlargement and flattening of the femoral head. Despite being recognized as a distinct entity a century ago, the exact etiology of LCPD is still unknown and is probably multifactorial. Factors that have been associated with the etiology of LCPD include coagulopathy, trauma, hereditary influences, hyperactivity or attention deficit disorder, and environmental factors, including exposure to cigarette smoke. These may work in combination in a “predisposed child” with certain growth and developmental abnormalities.8-12 Low birth weight, short stature for age, and delayed bone age relative to chronological age early in the disease process are common findings. However, how these findings relate to the pathogenesis of the disease is still uncertain.
LCPD can be diagnosed between 18 months of age and skeletal maturity but is most prevalent between 4 and 12 years of age. The disease is 4 to 5 times more likely to develop in boys than girls, more common in whites and those of Asian descent, and rare in African Americans and Native Americans. African Americans presenting with clinical and radiographic signs of LCPD should undergo evaluation for an underlying hemoglobinopathy. Bilateral disease occurs in 10% to 12% of patients but is typically not symmetric or concurrent. A patient with bilateral, symmetric avascular necrosis should be evaluated for other systemic conditions such as hypothyroidism, an epiphyseal dysplasia, Gaucher disease, sickle cell disease, and steroid medication use.
FIGURE 215-3. The Pavlik harness. The transverse chest strap should be placed just below the nipple line. The hips should be flexed to 120 degrees, and the posterior straps should not produce forced abduction. (Reprinted with permission from Tachdjian’s Pediatric Orthopaedics, 4th Edition, edited by John A. Herring.)
CLINICAL FEATURES
The most common presenting symptom is a painless limp, frequently first noticed by a parent. The limp is commonly exacerbated by physical activity and alleviated with rest. Pain is the second most common presenting symptom and may be located in the groin, anterior hip region, or laterally around the greater tro-chanter. There often is referred pain to the knee which, if unrecognized, can lead to a delay in diagnosis. The patient or parent may note an isolated traumatic event (fall or twisting injury) prior to the onset of the symptoms. These initial symptoms may completely resolve after a few days, followed by the waxing and waning of symptoms for some time.
On physical examination, the patient will have a limp in addition to limitation of abduction and internal rotation. During the early phase of the disorder, reduction of hip motion is common as a result of muscle spasm and synovitis within the hip joint. A hip flexion contracture may also be present, and there may be varying degrees of atrophy of the gluteus, quadriceps, and hamstring muscles.
Initial radiographic imaging should include a standing anteroposterior (AP) pelvic radiograph and a frog-lateral radiograph of both hips. Significant radiographic changes will be evident for 18 to 24 months as the femoral head goes through fragmentation and healing followed by remodeling of the femoral head and acetabulum that will last until skeletal maturity. The extent of radiographic changes is quite variable from patient to patient, and the radiographic appearance may not correlate with the patient’s symptoms or function. Magnetic resonance imaging (MRI) and technetium bone scanning are both effective means of diagnosing Legg-Calvé-Perthes disease (LCPD) in its earliest stages. MRI has been found to be more accurate in the early diagnosis than other imaging modalities but is typically not needed to make the diagnosis.
In the absence of radiographic changes, the differential diagnosis should include trauma and infection. In the presence of radiographic changes, the differential diagnosis should include other causes of avascular necrosis such as sickle cell disease (and other hemoglobinopathies), thalassemia, steroid medication use, the sequela of a traumatic hip dislocation, or treatment of developmental dysplasia of the hip. In addition, epiphyseal dysplasias, such as multiple epiphyseal dysplasia, spondyloepiphyseal dysplasia, mucopolysaccaridoses, and hypothyroidism should be ruled out.
The disease severity can range from very mild (minimal pain and limp) to severe (marked activity limitation). Most children experience moderate symptoms for 12 to 18 months followed by complete resolution of their symptoms and a return to normal physical activities. The patient’s age at onset of symptoms has been found to be the most consistent factor affecting the course of the disease. Usually, those with early onset (before 6 years of age) have mild disease, those with onset between 6 and 9 years of age have moderate symptoms, and those with onset at 9 years of age or later have the most severe course and worst outcome.13-15 The outcome is also affected by the duration from the onset of the disease to complete resolution: the shorter the duration, the better the final results. The most important predictor of long-term outcome of LCPD is the shape of the healed femoral head and its congruency with the acetabulum at maturity.
TREATMENT
Treatment is indicated for pain, limitation of motion, early hip subluxation (femoral head uncovering), and for those children with severe disease and a worse prognosis. The initial treatment for all symptomatic patients should include elimination of hip joint irritability (rest, crutches, and/or nonsteroidal anti-inflammatory medications) and the maintenance or restoration of a normal range of hip motion (physical therapy if needed). Bed rest with or without traction for short periods for major episodes of pain or loss of joint motion may be needed. Other nonoperative treatment methods that can be used for the early treatment of and prevention of subsequent hip subluxation include abduction casts (Petrie casts) and abduction bracing.
Surgical treatment for Legg-Calvé-Perthes disease is controversial. Surgical options include muscle–tendon lengthening and osteotomies of the femur and/or pelvis. A proximal femoral varus osteotomy and/or a pelvic osteotomy (Salter innominate osteotomy) are most commonly reserved for patients over the age of 8 years at the onset of symptoms. A recent long-term, multicenter study demonstrated that for certain patients over the age of 8 years at the onset of symptoms, these osteotomies are likely to improve outcome.
SLIPPED CAPITAL FEMORAL EPIPHYSIS
Slipped capital femoral epiphysis (SCFE) is a displacement of the femoral epiphysis off of the proximal femoral metaphysis (femoral neck). The femoral epiphysis actually maintains its normal relationship within the acetabulum, and it is the femoral neck and shaft that displace relative to the femoral epiphysis, most commonly slipping anteriorly and externally rotating.
The incidence of SCFE is estimated to be approximately 2 per 100,000 population, but this varies according to race, sex, and geographic location.16 SCFE typically occurs during adolescence (boys 13 to 15 years of age, girls 11 to 13 years of age), a period of maximal skeletal growth. African American males and adolescents residing in the eastern states appear to be at greatest risk. When SCFE occurs in a juvenile (10 years of age and younger) or in a patient with an open physis older than 16 years of age, careful assessment for an underlying endocrinopathy should be considered.
The exact etiology of a SCFE is still unclear, but mechanical and endocrine factors are believed to play a role. The mechanical factors that contribute to a SCFE include thinning of the perichondral ring complex (a fibrous band that encircles the physis at the cartilage–bone junction), relative or absolute retroversion of the femoral neck, and an increased obliquity of the adolescent proximal femoral physis relative to the femoral neck and shaft. The most common endocrine disorders associated with SCFE are hypothyroidism, growth hormone deficiency (SCFE will occur during hormone replacement), and chronic renal failure (due to uncontrolled secondary hyperparathyroidism).17
CLINICAL FEATURES
Bilateral involvement of the hips either on initial presentation or subsequently occurs in approximately 20% to 25% of patients. Of those with bilateral SCFE, 50% will present initially with both hips involved. In more than 80% of patients who present with unilateral involvement and subsequently develop a contralateral SCFE, the contralateral SCFE will develop within 18 months of presentation for treatment of the first hip. Younger patients and those with endocrine or metabolic abnormalities are at much higher risk for bilateral involvement.
The most common clinical presentation is that of a chronic, stable SCFE. The adolescent is commonly an obese male, often African American, with a few months of gradual onset groin pain, thigh pain, knee pain, or a limp. Pain referred to the knee may be the only presenting symptom; therefore, any adolescent who presents with knee pain must have the hips evaluated radiographically to rule out a SCFE. Clinically, patients with a SCFE have a shortened lower extremity with increased external rotation at rest and an obligate abduction and external rotation of the hip with passive or active hip flexion (Figure 215-4). An acute SCFE, one that occurs in a patient with minor prior symptoms for 3 weeks or less, often presents as a sudden, fracture-like episode with severe pain and an inability to bear weight after relatively trivial trauma. Avascular necrosis (AVN) is a significant complication associated with acute, unstable SCFE with an incidence of up to 47%.18
FIGURE 215-4. Clinical examination of a patient with stable slipped capital femoral epiphysis. Hip flexion and external rotation are limited. With flexion of the affected hip, the limb rotates externally. (Reprinted with permission from Tachdjian’s Pediatric Orthopaedics, 4th Edition, edited by John A. Herring.)
Anteroposterior (AP) and frog-lateral plain radiographs of the hip are the primary and often the only imaging studies needed to diagnose a SCFE. The earliest radiographic sign is widening and irregularity of the physis, and displacement may not be evident. In the normal hip, a line drawn tangential to the superior femoral neck (Klein’s line) on the AP radiograph should intersect a portion of the femoral head. With posterior displacement of the typical SCFE, this line will not intersect the head. The frog-lateral radiograph is the most helpful view for identifying the slip, because the posteriorly slipped head is easily seen.
TREATMENT
A patient with an acute, unstable slipped capital femoral epiphysis presents with a sudden onset of severe, fracture-like pain in the affected hip, usually the result of a minor fall or twisting injury. An acute, unstable slipped capital femoral epiphysis (SCFE) is generally treated urgently, because these patients are at significant risk for avascular necrosis. The patient is unable to bear weight and will seek immediate medical attention. These patients should be immobilized on a stretcher and provided appropriate analgesics. Any attempt at ambulation or transportation by wheelchair will cause severe pain and risk further slippage of the capital epiphysis.
Once the diagnosis of a chronic, stable slipped capital femoral epiphysis is confirmed, the patient should be made non-weight bearing and transported by wheelchair or stretcher. The patient should be admitted to the hospital and placed on bed rest until prompt, definitive treatment is undertaken. Acute displacement of the epiphysis after diagnosis of a mild, chronic slip has been well documented and can dramatically alter the patient’s prognosis.
The primary goal of definitive treatment for SCFE is to stabilize the capital femoral epiphysis to the femoral neck to prevent further slipping. Most orthopedic centers treat SCFE by single in situ percutaneous screw fixation with no attempt at reducing the deformity or using two screws for an acute, unstable SCFE. Postoperatively, patients will generally remain crutch assisted, foot-flat weight bearing for 6 weeks followed by full weight bearing with restricted running and jumping activities for an additional 6 weeks.
Diligent follow-up is required for these patients after treatment, because there is a risk of a slipped epiphysis of the contralateral hip. In addition, patients with unstable SCFE must be followed for the development of avascular necrosis (AVN) of the femoral head, the most severe complication associated with SCFE, which most often occurs within 6 to 12 months following treatment.18,19 Patients with AVN will present with increasing hip pain, decreased range of motion, and radiographic changes that may include increased femoral head density, fragmentation, and collapse. Before and after treatment, families must be reminded that in situ screw fixation will not change the deformity of the proximal femur and, thus, will not change the range of motion of the hip, the externally rotated position of the lower extremity, or the patient’s limp. If correction of the proximal femoral deformity is desired, a proximal femoral flexion, internal rotation osteotomy is performed after healing of the SCFE.20-22 Leg length inequality is also a common finding with longer-term follow-up as a result of shortening secondary to the slippage as well as early closure of the growth plate. In addition, early arthrosis of the hip joint secondary to residual femoral head deformity of SCFE or AVN is a leading cause of degenerative hip joint disease in adults.
TRANSIENT SYNOVITIS OF THE HIP
Transient (toxic) synovitis of the hip joint is one of the most common causes of lower extremity pain and limping due to an irritable joint. The condition is most commonly seen in children between 3 and 8 years of age who present with a history of acute onset hip pain, limited hip range of motion, and limping (or an inability to walk in more severe cases). Frequently, there is a history of a recent viral illness.
Clinically, at presentation, transient synovitis mimics septic arthritis (see Chapter 211). However, patients with transient synovitis rarely have a temperature above 38°C, evidence of systemic illness, or an elevation of the white blood cell count (WBC), C-reactive protein level, or erythrocyte sedimentation rate. Radiographs will show no abnormalities, and an ultrasound of the affected hip will show an effusion. Aspiration of the joint may be necessary to rule out septic arthritis. The joint aspirate will usually show a WBC count between 5000 and 15,000 cells/mL.
Treatment is aimed at eliminating the underlying inflammatory synovitis. A brief period of bed rest, progressive weight bearing with crutches if needed, and around-the-clock nonsteroidal anti-inflammatory medications for 3 to 5 days are usually all that is required. Clinical symptoms usually resolve gradually and completely over a period of several days to weeks (the average duration is 10 days). The long-term outcome is generally favorable, and recurrence is rare.