The use of metal-backed patellar prostheses in total knee arthroplasty.

Metal backing of polyethylene prosthesis components decreases deformity of the overlying polyethylene and enhances fixation to the underlying bone. Previous metal-backed patellar designs have often failed, primarily because of implant design and implantation technique. In 451 total knee arthroplasties using metal-backed patellar prostheses, there were no implant failures. The implants were dome shaped and did not have a metal endoskeleton. The component was inset into the patellar bone so that the base plate was below the superficial surface of the bone. These factors maximized polyethylene thickness and prevented wearing through to the metal base plate. The advantage of metal backing is that it strengthens the component and allows for possible biologic ingrowth. In this series, the combination of implant design and implantation technique may have eliminated serious problems seen with other metal-backed patellar implants.