COMPONENT POSITION AND POLYETHYLENE WEAR IN TOTAL HIP REPLACEMENT

Abstract

Introduction and Objectives: Our aim is to determine the influence that the orientation and position of the components has on polyethylene wear in a non-cemented total hip replacement (THR) model.

Materials and Methods: We studied a series of 50 THRs in which both components were coated with hydroxyapatite and polyethylene that had been sterilized by gamma radiation in an atmosphere of oxygen. Polyethylene wear was checked regularly throughout the study (mean 128 months, minimum 120 and maximum 139) using a computer program. We studied the relationship of wear with version and abduction of the acetabular component and the location of the center of rotation in the pre and postoperative periods as determined by X-rays of the teardrop and the tip of the greater trochanter.

Results: The mean annual rate of wear was 0.17 mm (SD: 9.75). A statistically significant correlation was seen between the vertical angle of inclination of the acetabular component and a greater annual rate of polyethylene wear (Pearson correlation = 0.451, p = 0.001). No relationship was found between wear and the other variables studied.

Discussion and Conclusions: Studies carried out over more than 10 years make it possible to assess the effect of the position of the components on polyethylene wear in THR. Although these results cannot be extrapolated to other types of friction or other surface pairs that undergo friction, the vertical position of the acetabular component favors wear of polyethylene sterilized in an atmosphere of air and should be avoided.