The effect of a novel CoCr electropolishing technique on CoCr-UHMWPE bearing frictional performance for total joint replacements

This study quantified the effect of a novel electropolishing treatment (Ultra Polish™) on CoCr surface morphology and coefficients of friction (CoF) when slid against UHMWPE pins. Standard and Ultra Polish CoCr samples were characterized using non-contact surface profilometry and SEM. The Ultra Polish process showed aggressive surface carbide removal, leaving behind large randomized pitted areas on CoCr. The trading of carbide peaks for pitted valleys, resulted no statistical change in surface roughness average (Ra) or dynamic CoF between Standard and Ultra Polish Treated groups. Mean Valley Roughness (Rvm) was better able to quantify changes in surface morphology seen in this study.

▶ A Novel electropolishing treatment (Ultra Polish™) on cobalt chromium alloy removed carbides from the surface leaving behind localized pitted areas. ▶ No statistical differences were found in dynamic coefficient of friction between the Ultra Polish and Standard CoCr slid against UHMWPE after 1 km of pin on disk testing. ▶ Surface roughness average (Ra) showed no significant differences between groups. ▶ Mean valley roughness (Rvm) accurately distinguished the significant localized pitting as a result of the Ultra Polish treatment. ▶ This innovative polishing process could be used for future applications in metal on metal joints or resurfacing techniques.