Investigation of hip joint prosthesis damage.

Following total hip arthroplasty the durability of a prosthetic implant depends on many factors but is generally limited by two types of damage: wearing of frictional surfaces of the acetabular and femoral component as well as the loosening and migration of the "rosthesis-cement-bone" system. Since it is possible to establish a cause-and-effect relationship between these two damage types, the aim of this research is to investigate the phenomena related to the contact surface and their influence on the prosthesis-bone relationship in general for various sizes and conditions of loading of the hip joint. The experimental study was conducted using a Timken testing device modified in such a way that simulation of relative movements of the joint elements was achieved using a mechanism that produces conditions similar to those in the human hip joint. The analysis of obtained measurements showed that actual radii of friction of the hip prosthesis did not correspond to the theoretical ones and that only a small portion of the total friction surface is realized. Variations of the radius of friction for the examined prosthesis type were very large, which changes the hypotheses on the ability of the prosthetic head and the "prosthesis-cement-bone" system to bear a certain amount of load. The construction and design of prosthetic implant components has a significant influence on both the amount of wear at the site of contact and the loosening of prosthesis.