Quantitative ultrahigh-molecular-weight polyethylene wear in total elbow retrievals

Abstract

The purpose of this study was to evaluate ultrahigh-molecular-weight polyethylene (UHMWPE) wear and damage from retrieved total elbow arthroplasty components and compare invivo wear with wear produced invitro. Explanted total elbow components were collected at revision surgery. UHMWPE damage was characterized visually, whereas penetration and wear were quantified using micro-computed tomography and gas pycnometry. Volumetric wear rates were compared with historical hip data, and wear data were compared with reported invitro wear test data. Humeral bushing damage primarily occurred in the form of burnishing, scratching, and pitting at the articular face in the region of contact with the ulnar component. Wear of the ulnar bushings was concentrated on the edge of the component at the point of contact with the axis pin. Pitting and embedded debris were dominant damage modes, in addition to burnishing and delamination. Backside wear was negligible. The median linear penetration rates of the lateral, medial, and ulnar bushings were 0.14 mm/yr (range, 0.01-0.78 mm/yr), 0.12mm/yr (range, 0.03-0.55 mm/yr), and 0.11 mm/yr (range, 0.01-0.69 mm/yr), respectively. The volumetric wear rates of the lateral, medial, and ulnar bushings were 5.5 mm3/yr (range, 0.7-37.2 mm3/yr), 5.9 mm3/yr (range, 0.6-25.5 mm3/yr), and 5.5 mm3/yr (range, 1.2-51.2 mm3/yr), respectively. The observed wear rates were similar to those reported in well-functioning total hip replacement patients with conventional UHMWPE bearings. We found limitations in reported invitro testing resulting in wear that was not consistent with our retrieval data. We recommend further investigation to clinically validate invitro simulation to provide appropriate loading protocols for elbow wear simulation.