Comparison between Mid-Term Results of Total Knee Arthroplasty with Single-Radius versus Multiple-Radii Posterior-Stabilized Prostheses

Single-radius (SR) prostheses and multiple-radii (MR) prostheses have different theoretical advantages; however, few comparative studies have been reported. The aim of the study was to compare mid-term clinical, radiological, and survival outcomes of SR and MR posterior-stabilized prostheses in total knee arthroplasty (TKA). Two hundred consecutive patients who underwent TKA between January 2012 and July 2013 were enrolled in the SR group (100 patients) and an MR group (100 patients), with a minimum follow-up of 5 years. Functional, radiological, satisfaction, and survival rates were evaluated. There was a significantly higher range of motion (ROM) in the SR group than in the MR group (flexion, 123.65 +/- 10.12 degrees vs. 115.52 +/- 10.03 degrees, p < 0.001). Quadriceps strength (3.05 +/- 0.43 vs. 2.68 +/- 0.58 kg, p = 0.025) and chair test results (80 [93.02%] vs. 69 [83.13%], p = 0.027) were better in the SR group than in the MR group. The SR group also had significantly less anterior knee pain (6 [6.98%] vs. 15 [18.07%], p < 0.05) and a better satisfaction rate than those in the MR group. No significant differences were observed in clinical scale scores such as Hospital for Special Surgery (HSS), Knee Society Score (KSS), and Short-Form 12 (SF-12), radiological results in terms of component position and radiolucent lines. The Kaplan-Meier survival curve estimates at 5 years were not significantly different (96.91% [95% confidence interval [CI]: 93.5-99.5%] vs. 94.86% [95% CI: 90.6-98.6%], p = 0.4696). The SR prosthesis design was better than that of the MR in terms of ROM, reduced anterior knee pain, contributions to better recovery of the extension mechanism, and higher satisfaction rates. The SR had similar results in clinical scales such as HSS, KSS, SF-12, radiological, or survival results to MR prostheses. More accurate measurements and longer-term follow-up are required.