Analysis of two bone-prosthesis interfaces and membranes from non-cemented trapeziometacarpal prostheses.

The non-cemented Ledoux trapeziometacarpal prosthesis has a high failure rate. In order to better understand the mechanism responsible for pain and loosening, we thoroughly analysed the membranes surrounding the prosthesis and the bone-prosthesis interface in two trapezia, each containing a Ledoux cup, which were resected after unsuccessful implantation. Serial sections, perpendicular to the longitudinal axis of the implanted cup, allowed histological examination of the interface and were used to quantify bone apposition. The tissues surrounding the prosthesis showed a foreign-body reaction to particles identified as titanium. The interface showed bony integration of the cup, mainly on the radial side and on the proximal part of the cup, with an appositional index of 28%. Our findings suggest that bony apposition might not be sufficient to ensure successful anchoring of the Ledoux cup in the trapezium in the presence of an intense foreign body reaction to titanium. Moreover, the presence of metal might be secondary to micromotion of the wings of the metallic part of the cup, induced by axial movement of the underlying polyethylene during pinch grip. The combination of polyethylene as an expander and titanium may need to be reviewed.