Histologic and microradiographic analysis of a revised porous-coated anatomic (PCA) patellar component. A case report.

A retrieved uncemented, porous-coated human patellar component was evaluated histologically and microradiographically. The metal portion of the component and porous coating were made of cobalt--chromium-based alloy. Because of adhesive capsulitis and inadequate knee flexion, the patient had revision surgery 11 months after the original total knee arthroplasty. Clinically, the device was not grossly loose. Contact microradiography of the porous material showed no calcified tissue ingrowth. Undecalcified histologic sections demonstrated only fibrous tissue ingrowth, with obvious bone-resorptive activity as well as numerous multinucleated giant cells adjacent to the porous metal.