Rethinking Knee Arthroplasty: Bicompartmental Unicompartmental Knee Arthroplasty as a Biomechanically Personalized, Function-Preserving Solution for Knee Osteoarthritis.

AIMS: Although total knee arthroplasty (TKA) remains the standard treatment for advanced knee osteoarthritis (OA), it often compromises joint proprioception and natural kinematics. Bicompartmental unicompartmental knee arthroplasty (bi-UKA), which preserves both the cruciate ligaments and patellofemoral joint, offers a joint-preserving alternative for selected patients with bicompartmental OA. This study aimed to compare the early- and mid-term outcomes of bi-UKA and TKA. METHODS: This single-center, prospective, real-world observational study included patients with knee osteoarthritis who were treated between January and October 2022. Eligible patients underwent either bi-UKA or TKA according to routine clinical decision-making and patient preference. Functional outcomes were assessed using the Knee Society Score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), range of motion (ROM), timed up and go test (TUG), and 2-min walk test over a 2-year follow-up period. Preference-related selection bias was reduced using inverse probability of treatment weighting (IPTW) based on a five-item preoperative preference assessment tool, and longitudinal outcomes were analyzed using IPTW-weighted mixed-effects models. RESULTS: Eighty patients were included in this study (bi-UKA: n = 35, TKA: n = 45). After inverse probability of treatment weighting (IPTW) adjustment, the bi-UKA group showed more favorable early outcomes: higher 1-month KSS functional scores (p = 0.001); better WOMAC scores at 1, 6, and 12 months (p < 0.05); greater ROM throughout follow-up (p < 0.0001); shorter TUG times; and longer 2MWT distances at early time points. The Forgotten Joint Score (FJS) scores at 1 and 2 years also favored bi-UKA, indicating greater satisfaction. CONCLUSION: Bi-UKA was associated with more favorable early functional recovery. By preserving the key anatomical structures and enabling more physiological motion, bi-UKA may be a feasible alternative in selected patients.