The role of friction in the loosening process of total endoprosthesis of the hip

Discussing the causes of aseptic loosening mechanism of total hip replacement shear forces resulting from friction between cup and head are often mentioned. Therefore measurements of friction torque in explanted endoprostheses were performed in a new hip simulator to evaluate the influence of friction on the loosening. Differing from other simulators the physiological deformation of the hip bones was imitated by a bending beam. The measured values were compared with mathematically and experimentally found limit loads of the cup fixation. It was shown that the only influence of the shear forces transferred by friction was no significantly dangerous factor for the interface between bone and bone cement of a primarily fixed cup.