Tissue reactions to wear products from polyacetal (Delrin) and UHMW polyethylene in total hip replacement.

The tissue reaction to implanted materials and their wear products is important for the long-term fixation of a total hip replacement (THR). Recent reports indicate a relatively high incidence of aseptic loosening with Christiansen total hip prostheses. We examined tissue reactions to wear products in two groups of prostheses: 16 Christiansen prostheses with polyacetal (Delrin) sockets, and 18 Charnley-Müller total hip prostheses with ultrahigh-molecular-weight polyethylene (UHMWP) sockets. Specimens from these 34 patients were compared in a combined qualitative and semiquantitative morphological study. We saw similar histological changes in specimens of both groups, but specimens from the bone-cement interfaces of the acetabulum and femur shaft in the polyacetal group showed more inflammation and necrosis.