Long-term evaluation of polyethylene wear in total hip replacement : a statistical analysis of the association between the degree of wear versus pain, interface change, osteopysis and implant failure

Abstract

With over 3.5 decades dedicated exclusively to total joint replacement, our arthroplasty unit has repeatedly identified and reported a clear correlation between cup wear on the one hand, and pain, interface widening and osteolytic failure on the other1. However, in view of the fact that this statement has sparked some controversy, clarification of this correlation became imperative, particularly in view of important clinical consequences. Materials and methods were provided by a potentially long-lasting gamma crosslinked cup. The arthroplasty follow- up ranged from 10-33 years. Objective clinical, radiographic and pathological evaluations were backed by computer analysis through the Department of Statistics at the University of Pretoria. We are able to conclude that the statistical correlation between wear, on the one hand, versus pain, interface effects and osteolysis on the other, was no coincidence but instead proved to be clearly conclusive. Of great importance is the fact that this study allowed us to set new objective criteria for true failure as well as impending failure, thus guiding us towards sensible decision-making in terms of revision surgery in these complex issues. Cup wear was thus clearly identified as the overwhelming leading variable in long-term prognosis in this type of total hip replacement.