The clinical and roentgenographic results of cementless porous-coated patellar fixation.

From May 1980 to July 1988, 522 porous-coated, metal-backed patellar components were implanted without cement in conjunction with the Porous Coated Anatomic (PCA) knee system during primary total knee arthroplasty (TKA). Four different designs were evaluated clinically and roentgenographically. Fixation failure at the bone-prosthesis interface was the most common cause of failure. The addition of a third peg to the metal backing led to a dramatic decrease in the rate of revision for loosening (from 6.1% to 0.6%). Two patellar implants, one two-pegged and one three-pegged (central dome), were revised because of polyethylene wear. The low incidence of polyethylene wear is attributed to careful attention to technique and the high degree of congruency at the femoral articulation. Porous-coated metal-backing offers a viable means of patellar fixation during primary TKA. Design modifications have led to enhanced fixation and improvements in short-term clinical and roentgenographic results.