Metallosis due to abnormal abrasion of the femoral head in bipolar hip prosthesis. Implant retrieval and analysis in six cases.

We report on six cases of metallosis which developed in bipolar hip prosthesis due to ceramic screws used for fixation of bone grafts. Two patients experienced severe metallosis due to abnormal abrasion of the femoral head. At the revision surgery, proliferated black synovia was found. Analyses of the retrieved prostheses revealed numerous small particles of alumina ceramic on the inner surface of the bearing insert of UHMWPE. These particles came from the broken ceramic screws, and scraped away the metallic femoral head resulting in severe metallosis. In four patients, the outer head came into direct contact with ceramic screws and mild metallosis was observed at revision surgery.