Creating Abrasive Conditions in Knee Simulator Tests of Oxidized Zirconium and Cobalt-Chrome Femorals

Previous knee simulator testing without intentional addition of abrasives demonstrated that the ultra-high molecular weight polyethylene wear of tibial inserts was less against Oxidized Zirconium than against cobalt-chrome femoral components. Because femoral components roughen clinically in a way that can increase wear of the insert, a means of conducting knee simulator testing under abrasive conditions was desired. A technique was developed to roughen the surface of the femorals by tumbling them with alumina powder before simulator testing. The resulting roughness on the cobalt-chrome components was within the range observed on femoral components retrieved clinically. Roughening femoral components in this way increased simulated wear rates of the polyethylene inserts about ten-fold, and Oxidized Zirconium maintained its advantage in insert wear rate over cobalt-chrome.