Polyethylene wear from femoral bipolar neck-cup impingement as a cause of femoral prosthetic loosening.

A 33-year-old woman underwent an uncemented bipolar hip arthroplasty for osteoarthrosis of the left hip in 1985. Because of painful aseptic loosening, the bipolar implant was revised to a total hip prosthesis in 1994. Membranous tissues around the implant histologically presented foreign-body reaction against polyethylene debris. The retrieved implant showed polyethylene wear of the rim of the bipolar cup. Three-dimensional measurement of the surface configuration of the polyethylene of the cup indicated that wear debris had been generated almost exclusively from femoral bipolar neck-cup impingement. Volumetric wear in the articulating dome portion of the polyethylene was negligible. This report clearly illustrates how impingement of a bipolar cup on the femoral neck can be a major source of polyethylene wear debris which induces femoral osteolysis and subsequent stem loosening.