[Late prognosis of Perthes' disease: which factors determine arthritis risk?].

In 55 patients with Perthes' Disease the radiographic and clinical results were reviewed at the Orthopedic Clinic Balgrist of the University of Zurich (Switzerland) an average of 42 years (range: 28-56) after onset of the disease. Radiographs were available from the onset of disease to maturity. They were systematically evaluated utilizing the following criteria: Catterall grouping, "head at risk" signs, Mose's criteria and various indices and quotients for the measurement of femoral head deformity. The late results of the affected hips in adult life based upon clinical and radiological examination, and especially the development of arthrosis, were correlated with the earlier evaluations using statistical methods. Our results support the therapeutic concept of "femoral head containment" which means a better prognosis for those hips in which the femoral head is well contained without lateral subluxation or extrusion. In contrast to the negative prognostic significance of lateral calcification, which was found more frequently in the older children with poor end results, the amount of femoral head involvement according to the Catterall grouping was not found to have any influence upon the late outcome. A very important predictor of the prognosis was found to be the sphericity of the femoral head evaluated according to Mose's criteria, followed by the head-acetabulum quotient, the acetabulum quotient and the radius quotient. When severe residual deformity persisted after the healing phase arthritis developed in many cases. Age was also a significant factor. Fewer good results were found in children who were more than 8 years old at the onset of symptoms. The last assessment, based on clinical and radiological criteria, showed that 46% of patients had an excellent and 33% a good late result. Disabling arthritis requiring surgery developed in only 9 cases. We found, as have other authors of long term follow-up studies, that many patients, especially those with no or only mild femoral head deformity, do not develop significant coxarthrosis in early or middle adult life. More than 50% of the patients showed only mild or even no arthrosis an average of four decades after the onset of Perthes' Disease.