Does Neck/Liner Impingement Increase Wear of UHMWPE Liners?

Abstract

Although impingement damage, backside wear, and damage to the femoral bearing surface are common observations of acetabular liners, they have traditionally been studied independently. In this study, we explore the hypotheses that repetitive impingement increases wear of UHMWPE inserts at both the articular surface and the backside surface, potentially compromising the durability and function of the hip replacement. One hundred thirteen acetabular components were retrieved during revision total hip arthroplasty after an average time in situ of 84 months. Each acetabular liner was examined with incident light and inspected for presence, location, and severity of signs of impingement and backside wear. The depth of penetration of the femoral head into the acetabular liner was also measured to calculate articular wear. Sixty percent (68/113) of acetabular liners examined showed evidence of prosthetic impingement, with moderate or severe damage to the rim in 32% (36/113) of components. Significant backside damage was present in 31% (34/109) of components. Moderate or greater backside wear was found in 61% (22/36) of liners exhibiting significant impingement damage vs 16% (12/73) of liners without impingement (P < .0001). The average wear rate of liners with moderate or severe impingement damage was 0.33 ± 0.07 mm/y, compared with 0.19 ± 0.04 mm/y for liners with mild or no impingement damage (P = .03). Repetitive impingement frequently occurs after THR and leads to a multitude of adverse events, including motion between the liner and the acetabular shell leading to backside wear and accelerated wear of the articular surface.