Impingement contributes to backside wear and screw-metallic shell fretting in modular acetabular cups.

Eighty-six polyethylene liners and 56 metallic shells of acetabular components were evaluated by visual and stereomicroscopic examination for impingement, backside polyethylene wear, creep, and fretting at the screw-metallic shell interface using a subjective scoring system. Medical records and radiological data were available in 65 and 46 patients, respectively. Impingement was found in 62 components (75%). Backside polyethylene wear and screw-metallic shell corrosion and fretting were significantly correlated (P < .001) with impingement. Polyethylene creep was significantly correlated to backside wear and tended to be higher for the cups that had impingement (P = .06). No correlation was found between backside polyethylene wear and implant design or cup position. Our results suggest that impingement in a modular acetabular component correlated with increased backside wear and screw-metallic shell corrosion and fretting.