Extensive metallosis and necrosis in failed prostheses with cemented titanium-alloy stems and ceramic heads

We describe three prostheses with cemented titanium-alloy stems and Al2O3 c eramic femoral heads which had to be revised after a mean period of implant ation of 78 months. In each case, the neck of the prosthesis had been so se verely worn that the profile was elliptical rather than circular, There was severe metallosis of the periprosthetic tissues. Metal particles isolated from the tissues were approximately one nanometre in size and the ratios of titanium, aluminium and vanadium in the particles were the same as in the original alloy. Histologically, the high concentration of metal particles m asked the presence of high-density polyethylene (HDP) debris, but again par ticles about one nanometre in size were isolated from the tissues. The seve re necrobiosis and necrosis noted were consistent with other reports of the presence of extensive wear particles in periprosthetic tissues. Wear is pr esumed to have occurred as a result of mismatch between the shape or size o f the taper cone and the femoral head, or to changes in the geometry of loa ding due to migration of the cup. To facilitate early intervention, patient s with this design of prosthesis should be monitored radiologically.