Fracture of a cross-linked polyethylene liner due to impingement.

We report a case of fracture at 2 years after implantation of a 50-kGy moderately cross-linked ultrahigh molecular weight polyethylene liner with an extended lip (Marathon, DePuy, Warsaw, IN). The extended lip section had fractured. The liner showed no oxidation. The articular surface was grossly deformed, likely due to wear, creep, and/or plastic deformation, and the liner showed no recovery of machining marks upon melting, indicating that some wear had occurred. Electron microscopy revealed fatigue striations on the fracture surface. The likely cause of failure was femoral neck impingement-induced wear and fatigue on the liner.