Locating the center of rotation of the hip

In prosthetic surgery of the hip joint it is essential to recenter the hip to recreate the leverage of the gluteus medius muscle. Determination of the center of rotation of the hip is difficult if both hip joints have been de stroyed. On the basis of 70 frontal radiographs of the hip in the standing position, the authors measured the position of the center of the femoral he ad in relation to Kohler's line and the TD line joining the two radiologica l Us ("tear-drops"), On the same radiograph they defined the horizontal aci d vertical indices. The descriptive analysis of these parameters stresses t he influence of sex on the coordinates of the center of rotation of the hip . The authors demonstrated the statistical correlations between the coordin ates of this center of rotation of the joint and certain horizontal and ver tical indices. It emerged that knowledge of these indices suffices to defin e the theoretic position of the center of rotation. The method is compared with other principles set out in the literature. The procedure has a clinic al application in the context of preoperative planning of prosthetic recons truction of the acetabulum, whenever it is destroyed bilaterally (after tra uma, in congenital dislocation or acetabular loosening, etc).