[Significance of the position of the endoprosthesis acetabular cup from the biomechanical and clinical viewpoint--recommendations for a classification].

The success of an artificial joint replacement over the long term depends, for the most part, on the optimal positioning of the acetabular cup. We investigated this thought in terms of biomechanical and clinical considerations, and, on the basis of a proposed classification, attempted to ascertain the best possible position. On the basis of our analysis we determined that the ideal position is an angle of 35 degrees, with a tolerance range of 25 degrees to 45 degrees. Here, the load on the polyethylene is low, so that wear and the formation of particles are minimized. This position can readily be achieved surgically with the aid of an auxiliary device and clinically provides the best results in terms of muscular stability, endurance and optimal scoring.