Preliminary evaluation and prognosis in Legg-Calvé-Perthes disease.

Children younger than 4 years of age suffering from Legg-Calvé-Perthes' disease (LCPD) do not necessarily have a good prognosis. Girls generally have a poorer prognosis than boys. Clinical examination is not contributory to specific diagnosis or prognosis. Roentgenographic evaluation may reveal metaphyseal cysts and early physeal closure, both of which indicate a poor prognosis. Increased radiodensity cannot always be equated with osteonecrosis and therefore classification of extent and stage of the disease process on first examination is problematic and may vary as the condition progresses. Bilateral hip arthrography helps in determining which affected hip requires treatment because it detects protrusion of the osteochondral femoral head beyond the coverage of the lateral acetabular lip. This protrusion is the most important "risk factor." Scintiscanning may be valuable for diagnosis and to follow progress but interpretation of the examination is difficult. The differential diagnosis of LCPD from transient synovitis and other conditions presenting with femoral capital epiphyseal changes is mandatory.