Precision and Accuracy of Polyethylene Thickness in Total Knee Arthroplasty: A Comparison of Conventional Measured Resection and Robotic-Assisted Techniques.

BACKGROUND: Total knee arthroplasty (TKA) aims to restore native knee kinematics through accurate bone resection and balanced flexion and extension gaps. Polyethylene thickness is a critical determinant of joint line preservation and stability. This study compared polyethylene implant accuracy and precision relative to the preoperative plan in robotic-assisted (RA) and conventional (C) TKA. METHODS: A retrospective review was performed of all patients who underwent TKA by a single surgeon at a single institution between March 1, 2018, and July 31, 2022. Patients were classified as having undergone either RA-TKA or C-TKA. A 9-mm polyethylene thickness was planned in all cases to achieve balanced flexion and extension gaps. Patient demographics and final polyethylene thickness were recorded. Mean differences from the planned thickness, deviation from the plan, and variance were compared. RESULTS: A total of 815 patients were included, with 404 (49.6%) undergoing C-TKA and 411 (50.4%) undergoing RA-TKA. Sex distribution did not differ between groups, though patients in the RA-TKA group were significantly older (70.46 ± 8.52 years vs 69.14 ± 8.34 years, P = .027). Mean polyethylene thickness was greater in C-TKA than RA-TKA (10.67 mm ± 1.18 mm vs 9.34 mm ± 0.61 mm, P < .001) with mean differences of 1.67 mm and 0.34 mm, respectively. Adherence to the planned thickness was higher in RA-TKA (72.26% vs 16.09%) and variance was significantly lower (0.37 vs 1.39, P < .001). CONCLUSIONS: RA-TKA demonstrated greater accuracy and precision in achieving planned polyethylene thickness, suggesting improved execution of the surgical plan and more consistent gap balancing. Prospective studies should determine whether these differences translate to superior clinical outcomes.