Experiences with Spherical Acetabular Osteotomy for the Correction of the Dysplastic Acetabulum

Abstract

Dysplasia of the acetabulum consists of reduction of the depth of the acetabulum and shortening of its roof, a diminution of the superior and anterior articular surface, and also of a tilted position of the acetabulum. This leads to a reduction of that part of the articular surface which bears weight effectively. A thickening of the acetabular fossa develops during the growth period through insufficient centering of the forces of pressure acting on the dysplastic hip joint and can be detected quite frequently. It results in a lateralization of the pivoting point of the hip and thus elongates the lever arm of the body weight. The abnormal position of the proximal end of the femur in an increased valgus, and anteversion which generally occurs simultaneously, has a crucial and negative influence on pathologic stress conditions which occur in the hip joint due to the flattening and tilting of the dysplastic acetabulum. The characteristic malposition of the femoral neck shortens the effective lever arm of the pelvitrochanteric musculature and causes an eccentric orientation of the pressure forces in the hip joint. The shortening of the power arm increases the pressure in the joint, since the musculature of the shorter lever arm has to develop an increased tension in order to stabilize the hip joint while standing. The lateralization of the acetabular fossa with the elongated leverage of load increases in its turn the muscle tension necessary for the stabilization of the joint, This further increases the pressure in the joint.

Orthopädische Klinik des Wichernhauses Nuremberg/Altdorf (Chief: Prof. Dr. H. Wagner), Federal Republic of Germany