Vergleich der knöchernen und knorpeligen Kongruenz des Hüftgelenkes nach abgelaufenem Morbus Perthes

Legg-Calve-Perthes disease is a prearthrotic deformity for a secondary osteoarthrosis of the hip. Sphericity of the femoral head and the congruency of the hip joint are the most decisive prognostic indicators for the outcome of Legg-Calve-Perthes disease. In his long-term follow-up study Stulberg refers to this criteria in his rating of radiographics. A clear definition of joint congruency is missing. Our aim was to determine and compare the congruency of the articular cartilage and the osseous structures of the hip joint with an objective method. Twenty hips (18 patients) with Legg-Calve-Perthes disease treated at the Philipps-University Marburg were retrospectively reviewed. Radiographics in the a.p. view (Becken a.p.), in the lateral view (Faux-Profil) and MR imaging in the corresponding planes (coronar and sagittal projection) by distracting the joint using 15kg of longitudinal traction were obtained. The congruency of the osseous and cartilaginous structures of the hip joint was evaluated by a geometric-mathematical system. The data in the present study showed incongruency for the osseous articular surfaces of the hip joint in conventional radiographics and in MR imaging with the direction of deviation predominate latero-caudal and antero-caudal. There was a larger deviation seen in the conventional radiographics. In contrast to the osseous incongruency the cartilaginous structures of the hip joint were congruent to each other. The evaluation of the hips by using the Stulberg-classification showed 15 hips with a spherical congruency and 5 hips with an aspherical congruency. This observation is contrary to our objectively measured degree of incongruency. The articular cartilage seems to compensate the measured roentgenographically osseous incongruency after Legg-Calve-Perthes disease. This compensation also seems to be responsible for the relatively late onset of secondary osteoarthrosis after Legg-Calve-Perthes disease and seems to ensure the function of the hip joint.