Comparative Wear Behavior of Titanium Nitride-Coated Titanium and Cobalt Chromium Femoral Components in Cementless Total Knee Arthroplasty

Abstract

Femoral component surface roughness is a critical determinant of polyethylene wear in total knee arthroplasty (TKA). Titanium nitride (TiN) ceramic surface coatings have been developed to improve wear resistance and address concerns related to metal hypersensitivity; however, comprehensive wear data remain limited. This knee simulator study evaluated the performance of TiN-coated titanium alloy (6 wt% aluminum, 4 wt% vanadium, balance titanium, Ti-6Al-4V) substrate femoral components compared with cobalt chromium (CoCr) femoral components. Mode I wear testing was conducted for 5.0 million cycles (mc) using highly crosslinked polyethylene tibial inserts, with wear rates and polyethylene debris morphology quantified. Mode III third-body abrasive wear testing was performed on TiN-coated femoral components using embedded 500 µm TiN-coated particles for 3.0 mc. Surface roughness was measured using White Light Interferometry (arithmetic mean height, Sa), and surface integrity was assessed using scanning electron microscopy. Following 5.0 mc of Mode I wear, volumetric wear rates were equivalent between TiN-coated and CoCr femoral components (1.03 vs 1.04 mm³/million cycles; p = 0.001), with no notable differences in polyethylene particle size (p = 0.114) or morphology. During third-body testing, surface scratching of the TiN coating was observed without evidence of gross surface failure. As anticipated, the mean Sa of TiN-coated femoral components increased through 3.0 mc of Mode III third-body testing, while remaining lower than literature-reported retrieved CoCr values (p = 0.001). In conclusion, TiN-coated femoral components demonstrated comparable in vitro adhesive wear performance to CoCr and provided improved resistance to abrasive conditions, where long-term resistance to abrasion is expected to govern reduced wear.