Legg-Calvé-Perthes Disease (LCPD) is a femoral head disorder of unknown etiology that involves temporary interruption of the blood supply to the bony nucleus of the proximal femoral epiphysis, leading to impairment of the epiphyseal growth and femoral head deformity.
ETIOLOGYThe etiology of LCPD remains unknown: Infection, trauma, and transient synovitis have been proposed but unsubstantiated. Factors leading to thrombophilia, an increased tendency to develop thrombosis and hypofibrinolysis, and a reduced tendency to lyse thrombi have been identified. Factor V Leiden mutation, protein C and S deficiency, lupus anticoagulant, anticardiolipin antibodies, antitrypsin, an
d plasminogen activator may play a role in the abnormal clotting mechanism.
Children with LCPD have delayed skeletal maturation and are shorter than normal. Abnormalities of thyroid hormone and insulin-like growth factors have been reported. Other associated factors include hyperactivity or attention-deficit disorder, hereditary influences, and environmental influences (including nutrition). Histologic findings in the CFE reveal various stages of bone necrosis and repair. Two possible pathways for the bone necrosis have been proposed; the vascular changes may be the primary event or events or there may be a primary disorder of epiphyseal cartilage, with resulting collapse and necrosis.
Avascular necrosis of the femoral head, unrelated to LCPD, may be sporadic but occasionally occurs as an autosomal dominant disorder. Most present as adults, but 10–20% may begin when younger than 20 yr of age. Familial cases may be due to a mutation of the type II collagen gene.
PATHOGENESIS OF DEFORMITYThe deformity can occur by four mechanisms in LCPD:The second mechanism for deformity involves the repair process itself; the deformity can occur related to the asymmetric repair process and the applied stresses on the femoral head.
The third mechanism for deformity is related to the disease process. The superficial layers of articular cartilage continue to “overgrow” as they are nourished by the synovial fluid. The deeper layers are, however, devitalized by the disease process, leading to epiphyseal trabecular collapse and deformity.
The fourth mechanism is iatrogenic and is caused by trying to contain, either nonsurgically or surgically, a noncontainable femoral head.
EPIDEMIOLOGYThe overall incidence of LCPD in the United States is about 1/1,200 children. LCPD is more common in boys than in girls by a ratio of 4 or 5 to 1. The peak incidence of the disease is between the ages 4 and 8 yr; LCPD has been reported in patients of ages 2–12 yr. Bilateral involvement may be seen in about 10% of the patients, but the CFEs are usually in different stages of collapse.
CLINICAL PRESENTATIONThe most common presenting symptom is a limp of varying duration. Pain, if present, is usually activity related and may be localized in the groin or referred to the anteromedial thigh or knee region. Failure to recognize that thigh or knee pain in the child may be secondary to hip pathology may cause further delay in the di
agnosis. Less commonly, the onset of the disease may be much more acute and may be associated with a failure to ambulate. Parents often report that symptoms were initiated by a traumatic event.
PHYSICAL EXAMINATIONAntalgic gait may be particularly prominent after strenuous activity at the end of the day. Hip motion, primarily internal rotation and abduction, is limited. Early in the course of the disease, the limited abduction is secondary to synovitis and muscle spasm in the adductor group; however, with time and the subsequent deformities that may develop, the limitation of abduction may become permanent. A mild hip flexion contracture of 10–20 degrees may be present. Atrophy of the muscles of the thigh, calf, or buttock from disuse secondary to pain may be evident. There might be an apparent lower extremity length inequality because of an adduction contracture or true shortening on the involved site because of femoral head collapse or growth inhibition. The classic portrait of a child with LCPD is a small, thin, extremely active child who is always running and jumping.
RADIOGRAPHIC FINDINGSRoutine plain radiographs are the primary imaging tool for LCPD. Anteroposterior and Lauenstein (frog) lateral views are used to diagnose, stage, provide prognosis, follow the course of the disease, and assess results ( Fig. 677-12A and B ). It is most important in following the course of the disease that all radiographs be viewed sequentially and compared with previous radiographs to assess the stage of the reparative process and to determine the constancy of the extent of epiphyseal involvement. In the absence of changes on plain radiographs, particularly in the early stages of the disease, radionuclide bone scanning with technetium-99m may reveal the avascularity of the CFE. MRI is sensitive in detecting infarction but cannot accurately portray the stages of healing. Its role in the management of LCPD is not defined. Arthrography may demonstrate any flattening of the femoral head and the hinge abduction phenomenon with abduction of the leg.
RADIOGRAPHIC STAGES.LCPD has been divided into four radiographic stages: initial, fragmentation, reossification (or repair), and residual (or healed). In the initial stage, the radiographic changes include a decreased size of the ossification center, lateralization of the femoral head with widening of the medial joint space, a subchondral fracture, and physeal irregularity. In the fragmentation stage, the epiphysis appears fragmented, and there are areas of increased radiolucency and radiodensity. During the reossification stage, the bone density returns to normal by new (woven) bone formation. The residual stage is marked by the reossification of the femoral head, gradual remodeling of head shape until skeletal maturity, and remodeling of the acetabulum.
CLASSIFICATION SYSTEMS.Catterall proposed a four-group classification, based on the amount of CFE involvement and a set of radiographic “head at-risk” signs, with a high degree of interobserver variability. Group I hips have anterior CFE involvement of 25%, no sequestrum, and no metaphyseal abnormalities. Group II hips have up to 50% involvement, with a clear demarcation between involved and uninvolved segments. Metaphyseal cysts may be present. Group III hips display up to 75% involvement with a large sequestrum. In group IV, the entire femoral head is involved.A two-group classification is based on the extent of the subchondral fracture, which corresponds to the amount of subsequent resorption. In Salter-Thompson group A, less than half of the femoral head is involved (Catterall groups I and II), and in group B, more than half of the femoral head is involved (Catterall groups III and III). The major determining factor between groups A and B is the presence or absence of a viable lateral column of the epiphysis. This intact lateral column (Catterall group II, group A) may shield the epiphysis from collapse and subsequent deformity.
A disadvantage of this classification is that not all patients are diagnosed early during the phase of the subchondral fracture.
The Herring lateral pillar classification is the most widely used radiographic classification system for helping to determine treatment and prognosis during the active stage of the disease ( Fig. 677-13 ). Classification is based on several radiographs taken during the early fragmentation stage. The lateral pillar classification system for LCPD evaluates the shape of the femoral head epiphysis on anteroposterior radiograph of the hip. The head is divided into three sections or pillars. The lateral pillar occupies the lateral 15–30% of the head width, the central pillar about 50% of the head width, and the medial pillar 20–35% of the head width. The degree of involvement of the lateral pillar can be subdivided into three groups. In group A, the lateral pillar is radiographically normal. In group B, the lateral pillar has some lucency but >50% of the lateral pillar height is maintained. In g
roup C, the lateral pillar is more lucent than in group B and <50% of the pillar height remains.
Certain radiographic signs, known as “at-risk signs,” are associated with poor results. These include the Gage sign, a radiolucency in the lateral epiphysis and metaphysis, calcification lateral to the epiphysis, lateral CFE subluxation, and a horizontal physis.
NATURAL HISTORY AND PROGNOSISFrom a prognostic standpoint, long-term follow-up studies of patients with LCPD show that most hips do well until 5th decade of life. Majority of the patients are active and pain free and have a good range of motion. The deformity and congruency at maturity and age at onset are the main prognostic factors for LCPD. Children who develop signs and symptoms before the age of 5 yr tend to recover without residual problems. Patients older than 9 yr of age at presentation usually have a poor prognosis. The remodeling potential is higher in younger children; the shape of the femoral head can improve significantly until maturity. The extent of CFE involvement and duration of the disease process are additional factors associated with a poor prognosis. Hips classified as Catterall groups III and IV, Salter-Thompson group B, and lateral pillar group C are at risk of a poor prognosis.
TREATMENTThe goal of treatment in LCPD is to create a spherical, well-covered femoral head with hip range of motion that is close to normal. The two main principles of treatment are maintenance of range of motion and acetabular containment of the femoral head during the active period of the process.
The methods of treatment include observation or no treatment, intermittent symptomatic treatment, containment, late surgery for deformity, and late surgery for osteoarthritis.
NONOPERATIVE TREATMENT.The mainstay of treatment is nonoperative, specifically activity limitation and physical therapy to maintain hip range of motion. Patients with severe pain may benefit from a short trial of bed rest and traction. Abduction devices have been used to keep the femoral head contained in the acetabulum. The most widely used abduction orthosis is the Atlanta Scottish Rite orthosis. These devices were thought to provide for containment solely by abduction without fixed internal rotation. The devices are considered ineffective and are not commonly used.
OPERATIVE TREATMENT.Surgical containment may be approached from the femoral side, the acetabular side, or both sides of the hip joint. A varus osteotomy of the proximal femur is the most common procedure. Pelvic osteotomies in LCPD are divided into three categories: acetabular rotational osteotomies, shelf procedures, and medial displacement or Chiari osteotomies. Any of these procedures can be combined with a proximal femoral varus osteotomy when severe deformity of the femoral head cannot be contained by a pelvic or proximal femoral varus osteotomy alone.
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