Abstract
A case of metallosis caused by alumina ceramic screw fixation of grafted bone in a Bateman UPF is reported. A 51-year-old woman underwent bone grafting acetabuloplasty with alumina ceramic screws in a Bateman UPF in September, 1983. She did well for a few years and then began having pain. Radiographs showed that the screws had broken, resulting in migration of the outer head. At revision in January, 1991, the capsule and bone adjacent to the component were seen to be densely and diffusely stained with a black material. Whereas the outer surface of the outer head in contact with the screws showed little sign of wear, the inner head was worn to a Rugby ball shape. SEM revealed many fragments of smashed alumina ceramic, whose rough edges were embedded in the inner surface of the HDP bearing insert. Furthermore, small metallic particles were seen adhering to hollow areas between the rough edges. EDX revealed peaks for Co, Cr and Mo, which were the constituents of the prosthesis alloy. The concentration of Co in the serum decreased markedly just after the operation. We therefore concluded that the smashed screw fragments had entered the joint space and penetrated the HDP, thereafter causing continuous abrasion of the metal head. Since alumina ceramic screws tend to fragment when they break, the outer head of a UPF should be removed as soon as possible if it comes into contact with the screws.
