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Key Features

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  • Occurs when the vascular supply to the proximal femur is interrupted

  • Highest incidence occurs between ages 4 and 8 years

  • Prognosis for complete replacement of the necrotic femoral head in a child is excellent, but the functional result depends on the amount of deformity that has developed

  • Better outcomes are observed for patients with an onset of symptoms before the age of 6

  • Generally, a poorer prognosis is expected for

    • Patients in whom the disease develops late in childhood

    • Those with more completed involvement of the epiphysial center

    • Those with metaphysial defects

    • Those who have more complete involvement of the femoral head

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Clinical Findings

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  • Persistent pain is the most common symptom

  • Limp or limitation of motion may be present

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Diagnosis

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  • Radiographic findings correlate with progression of the disease and the extent of necrosis

  • Effusion of the joint associated with slight widening of the joint space and periarticular swelling are the early findings

  • Decreased bone density in and around the joint is apparent after a few weeks

  • The necrotic ossification center appears denser than the surrounding viable structures, and the femoral head is collapsed or narrowed

  • As replacement of the necrotic ossification center occurs, rarefaction of the bone begins in a patchwork fashion, producing alternating areas of rarefaction and relative density, referred to as "fragmentation" of the epiphysis

  • Widening of the femoral head may be associated with flattening, or coxa plana

  • If infarction has extended across the growth plate, a radiolucent lesion will be evident within the metaphysis

  • If the growth center of the femoral head has been damaged and normal growth arrested, shortening of the femoral neck results

  • Eventually, complete replacement of the epiphysis develops as living bone replaces necrotic bone by creeping substitution

  • Serial radiographs help to distinguish this disease from transient synovitis of the hip

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Treatment

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  • Protection of the joint by minimizing impact is the principal treatment

  • If the joint is deeply seated within the acetabulum and normal joint motion is maintained, a reasonably good hip can result

  • Little benefit has been shown from bracing

  • Surgical treatment is controversial

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