Polyethylene wear in prosthetic hips with loose components.

We measured in vivo polyethylene wear of acetabular cups in 74 patients (83 hips) with Charnley total hip arthroplasties (THA), revised because of aseptic loosening of either the acetabular or femoral component. We analyzed conventional pelvic radiographs of 42 THAs before revision due to loose acetabular components alone and 41 THAs before revision due to loose femoral components alone. The THAs were revised after 10 to 26 years. The mean wear-rate in hips with a loose acetabular components was 0.3 mm/y, whereas in hips with a loose femoral components, it was 0.1 mm/y (P=.0001). The mean total linear wear, as measured on the last available radiographs before revision, was 3.4 mm and 1.5 mm, respectively (P=.0001). A significant difference in linear wear between hips with loose cups and loose stems was seen 1 year after surgery: 0.4 mm/y versus 0.3 mm/y, respectively (P=.05).