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Pediatric Hip Disorders: Slipped Capital Femoral Epiphysis and Legg-Calvé-Perthes Disease

2018; American Academy of Pediatrics; Volume: 39; Issue: 9 Linguagem: Inglês

10.1542/pir.2017-0197

1529-7233

Alexa J. Karkenny, Brandon M. Tauberg, Norman Y. Otsuka,

Neurogenetic and Muscular Disorders Research

After completing this article, readers should be able to:Pediatric hip pathology can lead to devastating complications, such as hip instability, early arthritis, and growth abnormalities. Two of the most common pathologies in this age group include slipped capital femoral epiphysis (SCFE) and Legg-Calvé-Perthes disease (LCPD). The importance of early diagnosis is paramount in both of these disorders, to allow for early treatment and attempt to limit the potentially morbid outcomes. Because many of these children will initially present to their pediatrician, recognition and early referral to an orthopedic specialist can drastically change their outcomes.Slipped capital femoral epiphysis is the most common hip pathology affecting adolescents. (1) Although a common diagnosis, up to 20% of patients are delayed in diagnosis, with short- and long-term consequences. (2) Contradictory to its name, the pathologic process occurs when the femoral head (epiphysis) of the proximal femur displaces on the femoral neck due to weakness in the hypertrophic zone of the growth plate (physis). Figure 1 illustrates the anatomy of the physis and epiphysis. Factors that may contribute to this slippage either predispose an individual to increased stress across the physis, such as obesity, or decrease its resistance to shear forces, such as metabolic derangements (ie, hypothyroidism) that inherently weaken the physis. (1) The pathogenesis of SCFE is likely multifactorial, with anatomical, genetic, and temporal factors.Increased shear forces across the physis may predispose individuals to slippage. (1)(3) Obese children tend to have higher mechanical loads across the physis and of the proximal femur, with increased retroversion. (1)(4) As childhood obesity continues to rise, so too does the prevalence of SCFE. (4) Obesity and puberty may be risk factors for SCFE due to changes in the metabolic activity of the physis. (5) The natural history of SCFE is affected by the acuity at presentation (ie, acute versus chronic SCFE), degree of displacement of the femoral neck in relation to the epiphysis, stability of the physis, and the resulting relation of the proximal femoral metaphysis to the femoral head. (1)Slipped capital femoral epiphysis is the most common hip pathology affecting adolescents, and the incidence continues to rise. (1)(3)(4)(6) The average age at onset is 12.7 years (13.5 years in boys and 12.0 years in girls). Unfortunately, recent evidence has shown that the average age at presentation has been dropping, which has been correlated with the rise in pediatric obesity. (4)(7)(8)(9) The overall prevalence of the disorder varies from 0.71 to 10.8 per 100,000 children, with boys more often affected than girls at a ratio of approximately 1.5:1. (1)(10) Typically, SCFE presents during puberty due to the relative weakness of the physis during rapid growth. (5)Loder et al (11) demonstrated that slip severity was significantly correlated with the age of the patient and the duration of symptoms. There is a weakly positive correlation between slip severity and duration of symptoms. (11) Factors that increase physeal stress or decrease resistance to shear forces are associated with SCFE, including obesity and metabolic abnormalities such as hypothyroidism. (5) Compared with white individuals, there is a higher prevalence in black, Hispanic, Polynesian, and Native American individuals. (12)The presentation of SCFE may vary, depending on the severity and stability of the slip. Often, a child will be 10 to 14 years old, will be obese, and will present with a chief complaint of groin/hip or knee pain. The duration of pain may be chronic (>3 weeks) or acute (<3 weeks) in presentation and may be related to a specific event. The pain may be an acute or chronic exacerbation. (13) The average duration of pain before diagnosis with SCFE is 4 to 5 months. (8) Pain may be constant or occur only when weightbearing, and the severity of the pain may differ. Typical pain is unilateral, although bilateral pain/SCFE may be possible and should be evaluated, especially in a younger child (<10 years old) or a child with metabolic abnormalities. (9)(14) Of the 18% to 63% of SCFE cases that are bilateral, only 50% to 60% will present with pain bilaterally. Those with bilateral SCFE presenting with unilateral pain often develop bilateral symptoms within 18 months. (3) Patients may present with painless limp and external rotation of the affected leg. Typically, patients have limited hip range of motion with decreased internal rotation, flexion, and abduction; they may also exhibit obligatory external rotation with passive flexion of the hip (Fig 2). (15) Limited internal rotation is the most commonly seen abnormality on examination. (6)Patients with stable SCFE will present with the ability to bear weight on the affected extremity, with or without crutches. Patients with an unstable SCFE are unable to bear weight on the affected extremity. Unstable SCFE is associated with a high risk of osteonecrosis, with the literature showing 10% to 60% risk. (16)(17)(18) Sankar et al (16) reported that younger patients with a shorter period of prodromal symptoms and unstable SCFE have a higher rate of avascular necrosis. However, another study by Loder et al showed that slip severity may be correlated with older age and longer duration of symptoms. (11) The increased risk of avascular necrosis with SCFE is directly correlated with the risk of development of early osteoarthrosis. (1) Table 1 summarizes key features that pediatricians should recognize in patients with SCFE.The average time from the onset of symptoms to diagnosis is approximately 8 weeks. This is due to delay in seeking medical care, initial complaint of knee pain, and insurance status. (19) The average time for a patient to see an orthopedist versus a general provider is 91 days versus 27 days, respectively. (19)Anteroposterior (AP) and frog-leg lateral radiographs of both hips are of utmost importance when evaluating a patient for SCFE. Knee pain in the immature patient demands critical evaluation of hip motion to rule out hip pathology. The Klein line, the metaphyseal blanch sign of Steel, and epiphysiolysis are helpful radiographic findings to aid diagnosis. (20) Other radiographic measurements may be beyond the scope of this review. The Klein line is evaluated on the AP pelvic radiograph and is a line extended from the lateral cortex of the femoral neck, which should intersect the femoral epiphysis. Epiphyseal location medial to the Klein line is a sign of SCFE. The blanch sign of Steel arises from the overlapping of the posteriorly positioned femoral head in relation to the metaphysis. Epiphysiolysis, which is widening of the growth plate, may be seen compared with the opposite uninvolved hip. (20) Figure 3 shows these measurements and radiologic signs.Magnetic resonance imaging (MRI) is typically not indicated unless findings are not obvious on radiography and SCFE is still suspected or there is a need to evaluate the contralateral hip in a patient at risk for another slip. (18) In early cases of SCFE, MRI is more sensitive than plain radiographs. (20) Also, MRI may be used to assess bone quality/blood supply of the femoral head in an unstable slip. Computed tomography is typically not needed except for presurgical planning in patients who may require surgical dislocation or osteotomy. (18)Laboratory values in patients with SCFE should be obtained for children younger than 10 years, children whose weight is less than the 50th percentile, or those with other suspected endocrine abnormalities. Included in the evaluation should be triiodothyronine, thyroxine, and thyrotropin levels to evaluate thyroid function and blood urea nitrogen and creatinine levels to evaluate for osteodystrophy of chronic renal failure. (21)(22)Treatment for SCFE typically involves stabilization of the physis to prevent worsening slippage. Stabilization is primarily performed via percutaneous in situ fixation (Fig 4), with a single screw being placed through the growth plate from the metaphysis into the epiphysis. (3)(13)(18)(23)(24) The decision whether to prophylactically fix the contralateral side has been largely debated. Bilateral slips occur in as many as 63% of patients. (3) The current indications for contralateral fixation are for patients at high risk for slippage, which includes age younger than 10 years, metabolic abnormality, extreme obesity, or unreliable follow-up. (14)(25) Figure 5 shows a child with hypothyroidism who required bilateral SCFE fixation.Approximately 61% to 95% of children with endocrine abnormalities had a contralateral slip, which should suggest the need for prophylactic fixation at the time of initial presentation. (21)(26) Severe, chronic slips may also be treated with hip capsule decompression, proximal femoral osteotomies, or epiphyseal reduction/pinning. (23)(27) Despite pinning, there remains a risk of leg length discrepancy, osteonecrosis of the femoral head, osteoarthrosis, and slip progression, although rare. (3)(28)(29) In addition, residual proximal femur deformity may occur, causing impingement due to failure of remodeling. (30)Patients with SCFE are at increased risk for arthritis; approximately 45% of children with a SCFE are estimated to require a total hip arthroplasty by 50 years after their slip. (31) The femoral neck may deform and cause impingement on the acetabulum, contributing to arthritis. (32) Patients with SCFE may present with progressive loss of hip motion due to chondrolysis, or cartilage breakdown. The diagnosis can be confirmed with radiographs showing decreased joint space, and up to 7% of patients may develop this condition, although they tend to do better than patients with SCFE who develop osteonecrosis. (3) Studies have shown that patients who are diagnosed and treated with pinning more than 2 months after initiation of pain tend to have developed more severe slips and thus are at higher risk for complications in the future. (19)Legg-Calvé-Perthes disease (LCPD) was first described in 1910 by several independent physicians, including Arthur Thornton Legg, Jacques Calvé, Georg Perthes, and Henning Waldenström. (33)(34) This disease constitutes idiopathic osteonecrosis of the femoral capital (head) epiphysis occurring in otherwise healthy young children. (35)(36) Disruption to the femoral head blood supply first results in growth arrest and later a pattern of healing that includes bone resorption, femoral head weakening and flattening (coxa plana), reossification, and, finally, growth resumption. (34) The cause of the initial vascular insult is unknown and the subject of debate; proposed mechanisms include genetic mutations in type II collagen, coagulation abnormalities, repetitive hip loading and extreme flexion as seen with gymnasts, second-hand smoke exposure, venous congestion, and hyperactive behavior. (37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)The incidence of LCPD is lowest in East Asian populations, ranging from as low as 0.9 per 100,000 up to 21.1 per 100,000 in Liverpool. (34)(48) Patients classically present with symptoms between 4 and 8 years of age but can present from 18 months of age to skeletal maturity. (34)(49) Male to female ratios of 3:1 up to 5:1 have been reported, and bilateral disease occurs in 10% to 15% of patients. (34)(50)Patients usually present with a painless limp for a few weeks to months. Patients may or may not report pain from antecedent trauma. However, pain may or may not be present, and when present, the location can be variable. Due to the innervation of multiple nerves about the hip, pain may be referred to the knee (femoral nerve), medial thigh (obturator nerve), or buttock (sciatic nerve). (33) The diagnosis may, in fact, be delayed when a patient with LCPD notes persistent pain referred to the knee. On physical examination, limited hip abduction and internal rotation (which is best tested with the hip extended) are the most consistent signs of LCPD. (33) Patients may appear to have shortening of the affected extremity in unilateral cases. Patients often have weak quadriceps and hip abductors, with muscle atrophy.Presentation will vary depending on the age of the patient and stage of LCPD. For example, a young child in an early stage of LCPD may present with a subtle limp and hip pain only during mildly limited range of motion, whereas an older child with a later stage of LCPD or a younger child with severe LCPD may present with a notable limp and inability to bear weight unassisted. The LCPD presentation may be atypical in females, with later age at onset and increased severity of involvement, especially in gymnasts and dancers subject to repetitive microtrauma at the hip. (37) There has been some discrepancy, with other authors reporting similar presentations to males. (51) Table 2 summarizes key features of LCPD that pediatricians can recognize.An evaluation for LCPD should start with a detailed history and physical examination, as well as radiographs of the pelvis and hips. If the pediatrician is ordering initial imaging, an AP pelvic radiograph with bilateral frog-leg lateral views (hips flexed and abducted) should be obtained. A single hip radiograph is not adequate because comparison with the contralateral hip cannot be made and bilateral disease may be missed. (52) Early radiographic signs include flattening of the femoral head and subchondral sclerosis (Fig 6). (52) Later signs include extrusion of the femoral head laterally such that it is not contained, or covered, by the acetabulum (Fig 7). In most cases, changes in the shape of the femoral head are accompanied by acetabular remodeling. (34)The classification systems for LCPD are based on radiographic findings. Waldenström described 4 stages characterizing the appearance of the femoral head: initial, fragmentation (Fig 8), reossification, and healed. (34)(50) In another classification described by Stulberg et al, (53) the severity of femoral head deformity at skeletal maturity correlates with the risk of osteoarthritis at mean follow-up of 40 years.The role of MRI in LCPD diagnosis, management, and prognostication is still evolving. (50) Magnetic resonance imaging has been shown to be more accurate in the early diagnosis of LCPD and to provide earlier and more reliable detail on the extent of femoral head necrosis and proximal femoral physeal involvement as well as the configuration of femoral head and acetabular deformities. (34)(54) More recently, perfusion (Fig 9), diffusion, and delayed gadolinium-enhanced MRI have been used to better understand the pathophysiology and prognosis of this disease. (55)(56)Legg-Calvé-Perthes disease is a diagnosis of exclusion. Other diseases causing osteonecrosis of the femoral head must first be ruled out before assigning a diagnosis of LCPD. A detailed medical history and family history, as well as medication list, facilitates that. Sickle cell disease, chronic systemic disease such as lupus, chemotherapy, and long-term corticosteroid use can result in osteonecrosis of the femoral head. In addition, radiographic mimickers of LCPD include multiple epiphyseal dysplasia and Gaucher disease, both of which typically affect both hips. (50)(57)The best strategy for treating and managing LCPD is early referral to a pediatric orthopedist when there is a suspicion for LCPD. It is important for pediatricians to have a general understanding of the treatment of LCPD to counsel patients and families both when referring patients for suspected LCPD and when following patients long-term who are known to have the disease.Our knowledge of the etiology and optimal treatment of LCPD continues to evolve, and currently there is no cure. (36) Treatment options vary based on age at presentation, deformity present during active disease, and residual deformity. The goal of treatment is to maintain a spherical femoral head and a concentrically reduced hip through the reossification stage of the disease to prevent eventual degenerative changes while preserving hip range of motion.The treatment of early disease includes the use of nonsteroidal anti-inflammatory medications, protected weightbearing, limited physical activity, and physical therapy for range of motion. For the patient who does not improve with these initial conservative measures, surgery to contain the femoral head is the next option, to position the femoral head deeper in the acetabulum (Fig 10), and to improve the coverage on the femoral head. (36)Multicenter cohort studies out of Norway and the Perthes Study Group have provided the highest level of evidence to date to guide treatment and have shown a difference in outcome depending on patient age at disease onset. (58)(59) A large retrospective study of patients younger than 6 years old indicated that 80% of hips have good results with symptomatic or nonsurgical management only. (60) In children younger than 6 years old with greater than 50% femoral head involvement, no significant differences have been seen among treatment with physical therapy, an orthosis, or proximal femur varus osteotomy, whereas children older than 6 years with greater than 50% femoral head involvement showed significantly better results with surgery. (58) Long-term follow-up suggests that more than 50% of patients with LCPD develop disabling arthritis by the sixth decade of life. (61) A 2012 prospective cohort series documenting pain and function in 56 adults who were treated nonoperatively for LCPD reported a 5% rate of total hip replacement at 20-year follow-up. (62)Table 3 lists the distinguishing features of SCFE and LCPD.To view teaching slides that accompany this article, visit http://pedsinreview.aappublications.org/content/39/9/454.supplemental.