Acetabular development in Legg-Calvé-Perthes disease.

The normal development of the proximal femur epiphysis and the acetabulum of 50 children with unilateral Perthes disease were analyzed on the unaffected side with serial x-rays using the epiphysis and the acetabular index. The same factors were studied on the affected side. A pathological process has been established in the affected hip. However, while these pathological processes run parallel up to 9 to 10 years of age on the femur epiphysis and in the acetabulum, the elastic ability of the acetabulum ceases over 9 years of age. This smaller plastic ability is the probable cause of unfavorable results in older children.