Abstract
BACKGROUND: Implant malalignment in total knee arthroplasty (TKA) correlates with poor outcomes, and robotic-assisted systems aim to improve precision. While closed-platform robotic systems dominate the market, their restriction to proprietary implants limits surgical flexibility. This study evaluates the radiological accuracy of an open-platform robotic system (Yuanhua KUNWU) across four TKA implant designs. METHODS: A multi-centre retrospective analysis of 129 robotic-assisted TKAs (Zhengtian Irene, n = 60; DePuy Synthes Attune, n = 32; Zimmer Biomet Persona, n = 20; Smith & Nephew Legion, n = 17) was conducted. Patients with end-stage osteoarthritis (Kellgren-Lawrence grade 3-4) were included, while those with prior knee surgery or complex anatomy were excluded (n = 15). A total of 114 pre-operative and post-operative alignment (hip-knee-ankle angle [HKA], femoral and tibial component coronal angles [FCCA, TCCA], posterior tibial slope [PTS]) were measured on radiographs by two independent reviewers. Interobserver reliability (intra-class correlation [ICC], Cronbach's α) and deviations from planned alignment (paired t-tests) were analysed. Acceptability was defined as ≤ 3° deviation. RESULTS: Interobserver reliability was excellent (ICC > 0.77, Cronbach's α > 0.87 for all parameters). Mean post-operative deviations from planned alignment were clinically small: HKA (+1.32°, P < 0.001), FCCA (-0.55°, P < 0.001), TCCA (+0.19°, P = 0.097), and PTS (-0.42°, P = 0.018). All mean differences were within the 3° acceptability threshold. Subgroup analysis of pre- and post-operative alignment between implant types also showed deviations of < 3°. CONCLUSIONS: The KUNWU open-platform robotic system achieved high radiological accuracy across four implant designs, with alignment deviations < 1.5°. This suggests open-platform robotics can provide implant versatility without compromising precision. Further studies regarding the assessment of long-term clinical and patient-reported outcomes and comparison with closed-platform systems are warranted.