[Lateralization of the femur head--its significance for the pathogenesis, diagnosis, therapy and course of Perthes' disease].

Lateral displacement of the femoral head was measured by the radiographs of 71 patients suffering from Perthes' disease. It is reported to be an early sign of the disease. Also it represents subluxation of the head of the femur, which is well accepted for a not favourable outcome. At the time of diagnosis average widening of the medial joint space was 1.9 mm. During the course of the disease the joint space was at its maximum width during fragmentation stage. A relation between lateral displacement and the extent of the disease could be shown, what suggests an importance in pathogenesis. Swelling of the soft tissues within the fossa acetabuli has been related to lateral displacement. On abduction films the femoral head could be demonstrated to migrate deeper into the acetabulum in those cases, when flattening of the femoral head was present. The consequences for the course and therapy of the disease is discussed.