Mid-term results of total knee replacement with single-radius versus multi-radius posterior-stabilized implants

Objective: Single-radius femoral total knee endoprosthesis designs were introduced with the promise of better clinical and functional results by means of superior biomechanical characteristics. The aim of this study was to compare the mid-term clinical, functional, radiologic, and survivorship outcomes of 2 types of posterior-stabilized knee replacement systems: the single-radius Scorpio (R) (Stryker (R), Mahwah, NJ, USA) and the multi-radius NexGen (R) (Zimmer (R), Warsaw, IN, USA). Methods: This retrospective observational study included 139 patients (164 knees) that underwent total knee replacement (TKR) between October 2004 and December 2010: 94 knees (75 patients) with Scorpio (R) and 70 knees (64 patients) with NexGen (R). The 2 patient groups were similar in terms of age, gender ratio, diagnosis, disease stage, and knee joint alignment. Mean follow-up times were 35 (range: 12-112) months and 32 (range: 13-75) months, respectively. Evaluation was based on the Knee Society scores (KSS) and the Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System, with survival data compiled using Kaplan-Meier survival analysis. Results: Clinical and functional improvements were recorded in all cases, with no statistically significant differences between the 2 patient groups. Survivorship was 95.8% (95% confidence interval [CI]: 91.8-99.8%) for the multi-radius implant at 60 months and 92.7% (95% CI: 87.7-97.7%) for the single-radius implant at 84 months, with no significant difference (p=0.31). Conclusion: This study demonstrates that both single-radius and multi-radius posterior-stabilized knee endoprostheses can significantly reduce pain and improve knee joint function in patients if used with a proper technique, with the additional benefit of good mid-term survivorship.