Photoelastic investigation of mechanical problems in applying acetabulum cups to hip prosthesis

Acetabulum cups are the counterparts of endoprostheses, which are mounted in the pelvis. There are different designs of such cups. They differ in their form and in the way of mounting. This paper deals with the threaded acetabulum cups with conical shape mounted in the pelvis. In general, one has to distinguish between stresses caused by the mounting process and lifetime stresses of the mounted cup. Stresses remaining of the mounting must ensure the so-called primary stability; however, they will disappear to some degree due to rheological properties of bone. The question arises whether the mounting stresses are responsible for local plastic deformations and the corresponding residual stresses or not. In this paper, mostly loading stresses and their dependence on the contact properties between pelvis and cup or between cup and polyurethane inlay are considered.