PROGRESSIVE BILATERAL PELVIC OSTEOLYSIS IN A PATIENT WITH MCKEE-FARRAR METAL-METAL TOTAL HIP PROSTHESES

As accumulating evidence indicates that polyethylene plays a central r ole in periprosthetic osteolysis, there is a renewed interest in alter natives 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 pathogenes is of osteolysis in metal-metal bearing total hip arthroplasties. This study presents a patient who had progressive bilateral pelvic osteoly sis associated with his McKee-Farrar metal-metal total hip prostheses. His left hip was revised after 13.5 years of service. The tissues rev ealed 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 aceta bular component was loose by that point. An arthrogram of this hip dem onstrated communication of the joint with the iliac osteolysis. The de velopment of osteolysis in both hips followed a pattern similar to tha t seen in metal-polyethylene total hip arthroplasties. Bearing wear co uld not be detected in either of the hips. Accumulating evidence indic ates that particulate debris of appropriate size and number is capable of fueling periprosthetic inflammation. Specific to this study, consi deration should be given to particles of cobalt-chromium alloy, polyme thyl methacrylate bone-cement, and barium sulfate. Other factors that should be considered are increased joint fluid pressure, soluble infla mmatory mediators, and the effective joint space. When bone becomes pa rt of the effective joint space, it is exposed to particulate debris, soluble factors, and potentially increased joint fluid pressures, whic h may promote localized bone resorption. It must be kept in mind that the development of osteolysis is multifactorial. Although bearings wit h better wear characteristics are desirable, the elimination of polyet hylene will not eliminate osteolysis.