Wear debris from bipolar femoral neck-cup impingement. A cause of femoral stem loosening.

The source of wear debris in total hip arthroplasty may occur at various interfaces: metal-ultra-high molecular-weight polyethylene bearings, metal-cement micromotion, bone-cement interfaces, and implant coatings. Wear-induced osteolysis may result in a spectrum of radiographic changes from radiolucent lines to massive osteolysis. Subsequent loosening of the implant may occur and revision may be difficult because of bone deficiencies. Impingement of the femoral neck on the acetabular component may result in polyethylene and/or metal debris, leading to early femoral stem loosening. The five cases presented, involving six hips, illustrate how bipolar cup-stem impingement may result in significant wear-induced femoral osteolysis.