Primary press fit and secondary osteointegration is a precondition for component anchoring in articular surface replacements, also in the case of proximal interphalangeal (PIP) joint. Nevertheless, many existing prostheses for the PIP joint have failed to show sufficient osteointegration. CapFlex-PIP(©) implant is a modular metal-polyethylene surface replacement for the PIP joint consisting of a proximal and distal component each having a titanium pore backside, which allows secondary osteointegration at the bone-implant interface. To evaluate osseous integration of this implant, we report a histological analysis of an explantation of a CapFlex-PIP(©) finger implant.
We present a case of a removed CapFlex-PIP(©) implant due to a soft tissue complication in an 84-year-old woman. The patient received bisphosphonate medication as treatment for osteoporosis. For the histological analysis, the bone-implant contact (BIC) was measured on all stained sections using a Zeiss Axioplan microscope. The summated BIC was 40.7 % for the proximal component and 46.5 % for the distal component of the implant. Histology showed that the implant was in direct contact with the bone at various locations, with no signs of wear or degradation.
This case demonstrates successful osteointegration of the CapFlex-PIP(©) implant. Both components of the investigated implant show osseous integration to an extent which is comparable to that of other load-bearing and articulating implants at different locations in the human body.