ROBOTIC-ARM ASSISTED BICOMPARTMENTAL KNEE ARTHROPLASTY DEMONSTRATES BETTER PHYSIOLOGICAL GAIT THAN TOTAL KNEE ARTHROPLASTY DESPITE SIMILAR PATIENT-REPORTED OUTCOMES

Aims Bicompartmental knee arthroplasty (BKA) preserves the anterior cruciate ligament and uninvolved compartmental anatomy and may therefore better restore physiological gait than total knee arthroplasty (TKA). Although robotic-arm assistance has improved the accuracy and reproducibility of BKA, its effect on postoperative gait remains unclear. The aim of this study was to compare gait biomechanics and clinical outcomes between robotic-arm assisted BKA and robotic-arm assisted cruciate-retaining TKA (CR-TKA). Methods A retrospective matched cohort study was performed including patients who underwent robotic-arm assisted BKA or CR-TKA between 2022 and 2025. Twenty-seven BKAs were matched 1:1 with 27 CR-TKAs according to age, body mass index, and preoperative hip-knee-ankle angle. Three-dimensional gait analysis was performed preoperatively and 1 year postoperatively. An additional cohort of 20 healthy volunteers was included for descriptive comparison of gait waveforms. Radiographic alignment and patient-reported outcome measures were also evaluated. Results Baseline characteristics were comparable between groups. At 1 year postoperatively, the BKA group demonstrated higher cadence (112.6 ± 11.9 vs. 105.2 ± 9.1 steps/min, p = 0.049), greater peak hip extension moment (2.55 ± 0.72 vs. 2.09 ± 0.69 Nm/kg, p = 0.031), and greater knee power generation during swing phase (0.27 ± 0.09 vs. 0.22 ± 0.07 W/kg, p = 0.049) than the CR-TKA group. Gait waveform analysis demonstrated knee extension and rotational moment patterns that more closely resembled those of healthy controls following BKA. Although overall postoperative limb alignment and patient-reported outcomes were comparable, BKA demonstrated greater preservation of constitutional joint geometry. Conclusion Robotic-arm assisted BKA demonstrated more physiological gait characteristics than robotic-arm assisted CR-TKA, including higher cadence, greater peak hip extension moment, and greater knee power generation during swing phase. Despite these biomechanical differences, patient-reported outcomes were comparable between procedures