Residual deformities related to arthrotic change after Perthes' disease. A long-term follow-up of fifty-one cases.

In order to clarify the long-term results of Perthes' disease and to elucidate the residual deformities, including those of the acetabulum, related to coxarthrosis, 51 patients who had had Perthes' disease were studied clinically and radiologically. Altogether there were 56 affected hips and radiographs taken from onset of disease to maturity were available in all cases. They were followed up for an average of 18 years. Thirteen hips (23%) revealed coxarthrosis. Head deformity, steepness of the lateral edge of the acetabulum, and insufficient acetabular coverage of the femoral head were noted in them both in adulthood and in the active phase of disease. Among these deformities, steepness of the lateral edge of the acetabulum was found to be the most significant prognostic factor and led to coxarthrosis of the affected hip even in the younger adult. Acetabular roof angle, which is a newly designed radiographic measurement, is a good indicator of the prognosis in Perthes' disease.