Retrieval Analysis of Total, Unicompartmental and Patellofemoral Knee Prostheses

Abstract

Knee replacement is an effective intervention in reducing pain and increasing the function of a debilitated knee. However, the rise in revision knee procedures calls for better understanding of the working of different knee designs in vivo. This thesis investigated 84 retrieved knee prostheses which included 22 Total Knee Replacement (TKR), 38 Unicompartmental Knee Replacement (UKR) and 24 Patellofemoral Knee Replacement (PKR) protheses. Roughness analysis of the metal component and semiquantitative damage scoring of the polyethylene (PE) components was undertaken for: TKR designs with 3 different types of PE inserts (Conventional PE (CPE), Crosslinked PE (XLPE), Antioxidant doped PE (AOXPE)); 2 UKR designs (fixed and mobile bearings); and 2 PKR designs (Cobalt-chromium (CoCr) and Oxidised Zirconium (OxZr)). The femoral components of all the 3 TKR designs were observed to have significantly roughened in vivo, however, the damage score of CPE, XLPE, AOXPE were not significantly different (p = 0.57). Only the femoral component of the fixed UKRs significantly roughened in vivo (p = 0.00), however, the PE inserts of mobile UKRs had significantly higher damage score (p = 0.04). In PKRs, both CoCr and OxZr trochlear components significantly roughened in vivo, however, there was no statistical difference observed between them. Two OxZr trochlear components had undergone substantial abrasion and scratch damage. With AOXPE being introduced relatively recently, understanding in vivo surface changes and comparison with XLPE and CPE inserts gives valuable insights about its performance. Few roughness studies have investigated in vivo surface changes of UKRs; therefore, this study adds to the limited literature available. This is the first report on the in vivo surface changes of retrieved PKRs.