Fixed-bearing unicompartmental vs. total knee arthroplasty in elderly patients with medial osteoarthritis and anterior cruciate ligament deficiency: a retrospective comparative study.

BACKGROUND: To compare fixed-bearing unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) in elderly patients with medial compartment osteoarthritis and anterior cruciate ligament (ACL) deficiency. METHODS: A retrospective case-control study with 1:1 propensity score matching was performed, enrolling 85 UKA and 85 TKA patients. Baseline covariates were well balanced (all standardized mean differences <0.1). Perioperative data, knee range of motion (ROM), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores, Tegner scores, patient satisfaction, and complications were analyzed over 5-year follow-up. RESULTS: UKA was associated with significantly lower postoperative pain (VAS: 3.65 ± 1.11 vs. 5.03 ± 0.78; MD -1.38, 95% CI -1.67 to -1.09; P < 0.0001), hemoglobin loss (8.15 ± 4.32 vs. 10.29 ± 5.88 g/L; MD -2.14, 95% CI -3.69 to -0.59; P = 0.0076), and tramadol consumption (774.10 ± 139.90 vs. 1,114.00 ± 308.70 mg; MD -339.90, 95% CI -412.0 to -267.8; P < 0.0001), with similar complication rates (2.35% vs. 4.71%; P = 0.6819). Postoperative ROM was greater in the UKA group at all time points (1 year: 125.30 ± 9.30° vs. 119.00 ± 10.85°; MD 6.30°, 95% CI 3.26-9.34; P < 0.0001). WOMAC scores were lower at 1 year (29.61 ± 12.88 vs. 34.74 ± 12.56; MD -5.13, 95% CI -8.95 to -1.31; P = 0.0094) but comparable from 2 to 5 years. At 5 years, instability rates were similar (1.18% vs. 3.53%; P = 0.6205), while UKA achieved higher Tegner (4.46 ± 1.14 vs. 3.99 ± 0.78; MD 0.47, 95% CI 0.18-0.76; P = 0.0020) and satisfaction scores (7.74 ± 1.10 vs. 6.94 ± 1.44; MD 0.80, 95% CI 0.41-1.19; P < 0.0001). CONCLUSION: Fixed-bearing UKA may represent a suitable alternative in carefully selected elderly patients with ACL-deficient medial osteoarthritis, yielding favorable perioperative recovery and comparable 5-year safety to TKA. Prospective multicenter studies are required to validate these findings.