The study of metal ion release and cytotoxicity in Co-Cr-Mo and Ti-Al-V alloy in total knee prosthesis - scanning electron microscopic observation.

We surgically retrieved two cobalt(Co)-chromium(Cr)-molybdenum(Mo) and five titanium(Ti)-aluminum(Al)-vanadium(V) alloy knee prostheses from patients because of mechanical failure and pain. We examined the distribution of the small particles which were released from the Co-Cr-Mo and Ti-Al-V alloys using a backscattered scanning electron microscopy (SEM). In addition we analyzed the metals in the artificial knee joints and the tissues adjacent to them using energy dispersive X-ray spectroscopy (EDS). We demonstrated that a myriad of fine particles, produced by the abrasion of both Co-Cr-Mo and Ti-Al-V alloys, accumulated in the synovial cells. As Co-Cr-Mo alloys disintegrate easily in the cells, Co dissolves from the peripheral areas of them, although Cr remains within the cells. In contrast Ti-Al-V alloys are very stable in the synovial cells. From these findings we conclude that the Co-Cr-Mo alloys are hazardous to the body as the alloys release Co which enters the body. In contrast the Ti-Al-V alloys are very stable and are patently safer. Artificial joints, however, are still in considerable need of improvement.