Novel Coordinate Measuring Technique for Quantifying Femoral Condyle Wear in Total Knee Arthroplasty: Surface Deviation Mapping and Limitations of Profilometry

Abstract As the demand for total knee arthroplasty (TKA) increases, especially among younger patients, implant durability and wear quantification have become critical concerns. The primary objective of this study was to evaluate wear on cobalt-chromium alloy (CoCr) femoral components using both contact and non-contact profilometry and to introduce a novel method of wear mapping via coordinate measuring. Surface roughness was measured across predefined wear zones using contact stylus-based profilometry and a high-resolution digital microscope. Additionally, a coordinate measuring machine (CMM) was used to generate point clouds of new and retrieved implants to quantify material loss and create surface wear maps. Results showed that non-contact profilometry yielded significantly higher average roughness (Ra) values in several zones compared to contact methods, although the differences were small (<1.0 µm). The CMM-based wear mapping revealed concentrated areas of metal loss, particularly on the lateral condyle, that were not apparent from profilometry data alone. Notably, wear depth on femoral components exceeded values previously reported in other metal-on-polyethylene (MoP) systems. These findings suggest that profilometry may underestimate femoral wear, and that sub-micron surface changes which are more sensitively detected by non-contact profilometry could be clinically relevant, particularly for patients with metal sensitivity. This study provides new insight into TKA component degradation and highlights the potential utility of coordinate mapping in orthopaedic wear analysis.