Analysis of failed Van Straten LPM proximal interphalangeal prostheses

The two-piece Van Straten Leuwen Poeschmann Metal (LPM) prosthesis was intended for the proximal interphalangeal (PIP) joints. However, revision rates of 29% after 19 months were reported alongside massive osteolysis. Five failed and retrieved LPM titanium niobium (TiNb) coated cobalt chromium components were obtained, three distal and two proximal, and subject to a forensic retrieval analysis. Components were analysed using a Talysurf contacting profilometer, a ZYGO non-contacting profilometer and an environmental scanning electron microscope (ESEM). All components were heavily worn. In some regions the TiNb coating had been scratched and penetrated. Elsewhere the TiNb coating had been removed where there was minimal scratching. Therefore here coating removal may have been due to corrosion between the coating and substrate. The osteolysis reported clinically was likely linked to the wear debris from the failed TiNb coating and substrate. Retrieval analysis has a vital role to play in understanding failures in finger prostheses.