A 7-Year-Old Boy With Left Hip and Knee Pain

Derik L. Davis, MD; Ogechukwu R. Menkiti, MD; Brighita Weinberg, MD

Disclosures

August 31, 2016

Discussion

Figure 1

Figure 2

The frontal radiograph of the hips (Figure 1) shows loss of the normal spherical shape of the left capital femoral epiphysis in comparison with the contralateral lower extremity. The contour is flattened; the flattening is most severe along the lateral aspect. The left femoral ossification center is sclerotic, small in size, and presents with slight subluxation laterally. Radiolucent fissures are present superiorly. A large irregular cystic lucency occupies the left proximal femoral metaphysis. The frog-leg radiograph of the hips (Figure 2) demonstrates prominent widening of the physis on the left.

Legg-Calvé-Perthes disease is a pediatric disorder that affects children between the ages of 3 and 12 years. The peak incidence for this condition occurs between the ages of 4 and 8 years. Males are affected more frequently than females, by about a 5:1 ratio. Legg-Calvé-Perthes disease occurs most often in white children.[1,2,3,4] About 90% of cases are unilateral in presentation. The remaining 10% of cases often present with apparent unilateral symptoms, only to develop disease of the contralateral hip at a later date. Involvement of both hips at the same time is uncommon, and this sequence of bilateral hip findings can help differentiate Legg-Calvé-Perthes disease from other disorders.[1,2,4]

Osteonecrosis of the capital femoral epiphysis is the eventual outcome of this disease process. A vascular insult to the blood supply of the epiphysis leads to infarction of the trabecular bone, flattening, and structural collapse of the proximal femur, with associated overgrowth of the articular cartilage. The cause of the ensuing vascular compromise is not well understood.[1,3,4] Several hypotheses relating to the etiology of Legg-Calvé-Perthes disease have been postulated, including exposure to passive smoking, low socioeconomic status, trauma, genetic factors, and dietary deficiencies. Despite extensive research, however, no proven cause has been described, and the disease remains idiopathic in nature.[5]

Generally, Legg-Calvé-Perthes disease progresses in three successive phases: a period of destruction, followed by a stable phase, and finally a healing phase. Each phase may occur over a period of months to years. The chondral surface of the hip joint is not usually directly involved, but it may be secondarily affected at later stages by joint incongruity. The magnitude of the abnormal structural changes to the proximal femur is variable and depends on the extent of osteonecrosis and the amount of mechanical pressure exerted on the joint.[1,2,4] Dead bone is reabsorbed, and revascularization and restoration of the epiphysis occur. The shape of the femoral head reflects the severity of the original vascular insult and the influence of treatment. The femoral head can be restored to a normal appearance similar to that of the unaffected contralateral hip, or it can become flattened (coxa plana) and widened (coxa magna), with the development of coxa vara. As a result of these changes, leg-length discrepancy and degenerative joint disease can develop.

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