Pyrolite carbon implants in the metacarpophalangeal joint of baboons

A nonconstrained uncémented Pyrolite carbon prosthesis was evaluated for replacement of the metacarpophalangeal joint. Six prostheses were inserted into the long finger metacarpophalangeal joint of four baboons. Nine months after insertion, the prostheses and surrounding tissues were removed enbioc and evaluated radiographrca/ly, utilizing histologic and microradiographic analyses. The four Pyrolite carbon implants inserted without cement were well tolerated. Histological evidence of direct appositional bone fixation along the medullary stem was observed in one specimen, and a combination of bone fixation with an interposing fibrous tissue membrane was observed in another. There was no evidence of bone resorption around the implant stems, and functional fixation was obtained with all of the uncemented Pyrolite carbon implants. No foreign body reaction was observed in the soft tissues, and no evidence of intracellular particles was present. Two cemented implants (one Pyrolite carbon and one polyethylene and metal) were also evaluated; both showed evidence of bone resorption and/or gross implant loosening.This study has demonstrated the potential for biological fixation with Pyrolite carbon-stem med implants for prosthetic replacement of the metacarpophalangeal joint, which thus offers significant improvement as a material for joint reconstruction.