Outcome of metal-backed cementless patellar components: the effect of implant design.

Failure of metal-backed cementless patellar components frequently has been observed clinically. To determine the effect of component design on clinical outcome, the authors reviewed the results of total knee arthroplasty with metal-backed patellar components of two different designs. The results of 168 total knee arthroplasties (Miller-Galante) with dome-shaped metal-backed patellar components and 93 total knee arthroplasties Miller-Galante II with modified dome-shaped metal-backed patellar components were reviewed. Kaplan-Meier survivorship was determined for both groups. Revision for patellar wear or failure was done or recommended in 36 Miller-Galante total knee arthroplasties. The cumulative survival rates at 3, 5, 7, and 9 years postoperatively were 99%, 92%, 81%, and 73%, respectively for this group. In contrast, only three of 93 Miller-Galante II patellar components required revision. Catastrophic patellar component failure, typically seen with the Miller-Galante metal-backed patellar components, was not observed with the Miller-Galante II components. Cumulative survival of the Miller-Galante II patella at 3, 5, 7, and 9 years postoperatively was 100%, 100%, 98.7%, and 93.2% respectively. The results of the current study show a dramatic reduction in metal-backed component failure by design changes incorporated into the modified dome-shaped Miller-Galante II patellar component and highlights the importance of design on the survival of cementless metal-backed patellar components.