Progressive bilateral pelvic osteolysis in a patient with McKee-Farrar metal-metal total hip prostheses.

As accumulating evidence indicates that polyethylene plays a central role in periprosthetic osteolysis, there is a renewed interest in alternatives such as metal-metal bearings. Several long-term studies report encouraging results with the McKee-Farrar total hip arthroplasty, but there is a paucity of data on the incidence, severity, and pathogenesis of osteolysis in metal-metal bearing total hip arthroplasties. This study presents a patient who had progressive bilateral pelvic osteolysis associated with his McKee-Farrar metal-metal total hip prostheses. His left hip was revised after 13.5 years of service. The tissues revealed no gross metal staining and fewer inflammatory constituents than are typically found in metal-polyethylene bearing hips. His right hip was still functioning after 22.5 years of service, although the acetabular component was loose by that point. An arthrogram of this hip demonstrated communication of the joint with the iliac osteolysis. The development of osteolysis in both hips followed a pattern similar to that seen in metal-polyethylene total hip arthroplasties. Bearing wear could not be detected in either of the hips. Accumulating evidence indicates that particulate debris of appropriate size and number is capable of fueling periprosthetic inflammation. Specific to this study, consideration should be given to particles of cobalt-chromium alloy, polymethyl methacrylate bone-cement, and barium sulfate. Other factors that should be considered are increased joint fluid pressure, soluble inflammatory mediators, and the effective joint space. When bone becomes part of the effective joint space, it is exposed to particulate debris, soluble factors, and potentially increased joint fluid pressures, which may promote localized bone resorption. It must be kept in mind that the development of osteolysis is multifactorial. Although bearings with better wear characteristics are desirable, the elimination of polyethylene will not eliminate osteolysis.