Long-term outcomes of single-radius total knee arthroplasty in an Asian population: a comparison of cruciate-retaining and posterior-stabilized designs

BACKGROUND: Single-radius total knee arthroplasty (TKA) has demonstrated favorable clinical outcomes and survivorship; however, long-term comparative data between cruciate-retaining (CR) and posterior-stabilized (PS) designs within a single-radius system remain limited, particularly in Asian populations. This study aimed to evaluate the long-term clinical and radiologic outcomes and survivorship of single-radius TKA and to compare CR and PS designs in an Asian population. METHODS: This retrospective study included 222 knees (152 patients) that underwent primary TKA using a single-radius prosthesis between 2006 and 2015, with a minimum follow-up of 10 years. There were 112 CR knees and 110 PS knees. Clinical outcomes were assessed using the Knee Society Score, Western Ontario and McMaster Universities Osteoarthritis Index, and Forgotten Joint Score. Radiologic outcomes were also evaluated. Kaplan-Meier survivorship analysis was performed using revision for all causes and aseptic revision as endpoints. Inverse probability of treatment weighting (IPTW) was applied to adjust for baseline differences between groups. RESULTS: At a mean follow-up of 13.2 ± 2.8 years, significant improvements were observed in all clinical outcomes compared with preoperative values (all p < 0.001). At the final follow-up, clinical outcomes did not differ significantly between the CR and PS groups, and IPTW-adjusted analyses also showed no statistically significant between-group differences. Revision surgery was performed in 6 of 222 knees (2.7%), with no difference between groups (p = 0.44). In the overall cohort, the 15-year Kaplan-Meier survivorship free from revision for all causes was 96.2% (95% CI 93.2-99.4). The estimated 15-year aseptic revision-free survivorship was 98.9% (95% CI 96.9-100) in the CR group and 95.6% (95% CI 91.4-100) in the PS group. Survivorship did not differ significantly between the CR and PS groups for either all-cause or aseptic revision (log-rank p = 0.99 and p = 0.99, respectively). However, only six revision events occurred, limiting the statistical power to exclude a clinically meaningful between-group difference. CONCLUSIONS: Single-radius TKA demonstrated favorable long-term clinical outcomes and high survivorship in an Asian population. No significant between-group differences were identified in clinical outcomes or survivorship between the CR and PS groups.