Functional outcomes of patient-specific instrumentation versus conventional instrumentation for unicompartmental knee replacement: A systematic review and meta-analysis.

BACKGROUND: Patient-specific instrumentation (PSI) has been introduced in unicompartmental knee arthroplasty (UKA) to improve implant positioning and potentially post-operative function. However, its clinical advantage over conventional instrumentation (cUKA) remains uncertain. This study aimed to evaluate current evidence comparing functional outcomes and implant survival following UKA performed with PSI versus conventional instrumentation. METHODS: A systematic review and meta-analysis was conducted in accordance with PRISMA guidelines. Embase, MEDLINE and the Cochrane Library were searched for studies comparing PSI and cUKA in primary UKA. The primary outcomes were 1-year Oxford Knee Score (OKS) and change in OKS from preoperative to post-operative assessment. Secondary outcomes included Knee Society Score (KSS), Knee injury and Osteoarthritis Outcome Score (KOOS), WOMAC and revision rates. Risk of bias was assessed using RoB 2 and ROBINS-I. RESULTS: Fourteen studies including 1680 knees in 1670 patients were included: five randomised controlled trials and nine retrospective comparative studies. All randomised studies had low overall risk of bias, while several non-randomised studies had moderate or high risk. No significant difference was found between PSI and conventional UKA for 1-year post-operative OKS (mean difference 0.90, 95% confidence interval -2.65 to 4.45; I2 = 0%). KSS and KOOS outcomes at 3 months and at ≥12 months also showed no significant between-group differences. WOMAC data were insufficient for meta-analysis. Revision data was heterogeneous and unsuitable for pooling. CONCLUSIONS: PSI does not demonstrate superior post-operative functional outcomes compared with conventional instrumentation in UKA. Its effect on revision risk remains uncertain owing to limited and heterogeneous evidence.