The ROSA knee robotic system demonstrates superior precision in restoring joint line height and posterior condylar offset compared to conventional manual TKA: a retrospective case–control study

Abstract Purpose Variations in total knee arthroplasty (TKA) joint line height may lead to complications such as pain and altered joint mechanics, while posterior condylar offset (PCO) can influence knee stability. Methods Single-centre, single-surgeon retrospective analysis from December 2019 to May 2023 investigated primary unilateral TKA (Nexgen Legacy, Zimmer Biomet) in patients with knee osteoarthritis, using ROSA robotic system (raTKA) or conventional manual technique (mTKA). Joint line height and PCO were measured and compared in 182 raTKA and 144 mTKA patients. Results The groups were matched in age ( p = 0.847) and sex distribution ( p = 0.2). Excellent interobserver agreement (ICC ≥ 0.9). RaTKA mean joint line height difference was − 0.0001 mm (± 3.48, 95% CI − 0.509, 0.509) ( p = 0.523), − 0.951 mm for mTKA (± 4.33, 95% CI − 1.664, − 0.237) ( p = 0.009). RaTKA mean PCO difference was 0.52 mm (± 2.45, 95% CI 0.160, 0.880) ( p = 0.005), 1.15 mm for mTKA (± 4.01, 95% CI – 1.496, 1.818) ( p < 0.001). Mean difference in joint line height of 0.95 mm between groups was significant ( p = 0.027), and for PCO, it was 0.63 mm, demonstrating tendency towards significance ( p = 0.08). Mean absolute value in joint line height difference between groups was not significant ( p = 0.235) but highly significant for PCO ( p < 0.001). Conclusion The ROSA knee robotic system can more accurately restore joint line height and PCO compared to conventional manual TKA. The improved degree of precision raTKA offers may be a vehicle for better Patient-Reported Outcome Measures, but further correlational studies are required.