Nitrided titanium alloy component enhances detection of small bone defects after total knee arthroplasty

This study compared the accuracy of various imaging modalities in detecting small bone defects simulating radiolucent lines (RLLs) around femoral components made of nitrided titanium alloy (Ti-6Al-4V) versus cobalt-chromium (Co-Cr) alloy.

Eight femoral components (four nitrided titanium alloy and four Co-Cr alloy) were implanted into pig femurs. Two total knee arthroplasty (TKA) models were fabricated for each component: normal and RLL TKA models. Fluoroscopically guided plain radiography, tomosynthesis, computed tomography (CT), and magnetic resonance imaging (MRI) were performed. Thirty orthopaedic surgeons independently assessed the images to determine the presence or absence of bone defects. Sensitivity, specificity, and accuracy were compared between materials and imaging modalities.

The accuracy of detecting bone defects was significantly higher in nitrided titanium alloy components than in Co-Cr alloy components using fluoroscopically guided plain radiography (66.7 % vs. 53.3 %, P = 0.048), tomosynthesis (87.5 % vs. 63.3 %, P < 0.001), and CT (100 % vs. 61.7 %, P < 0.001). MRI showed no significant difference (52.5 % vs. 55.8 %, P = 0.698). Furthermore, for nitrided titanium alloy components, the accuracy of detecting bone defects around the femoral components using CT was 100 %.

Small bone defects simulating RLLs were more easily detected around nitrided titanium alloy femoral components than around Co-Cr alloy components. Nitrided titanium alloy femoral components may offer an advantage by enabling earlier detection of loosening and potentially reducing the need for complex revision surgery. These findings may serve as one of several factors for surgeons to consider when selecting implant materials for TKA.