Histologic analysis of a retrieved microporous-coated femoral prosthesis. A seven-year case report.

A microporous-coated femoral prosthesis with an average pore size of 80 to 100 microns was retrieved after seven years in a revision operation on a failed cemented acetabular component. The proximal anterior and lateral aspects of the implant were encrusted with bone. The bone was attached to the porous coating in regions of ingrowth. The implant was stable within the femur although most of the porous coating was not bone ingrown. There was progressive bone resorption in the proximal femur, suggestive of a reactive biologic mechanism. There was also a sizable posterior pocket of granulation tissue containing chronic inflammatory round cells associated with numerous birefringent polymeric particles. Polyethylene wear debris and acrylic cement were engulfed by multinucleated giant cells enveloping the loose cup.