Posterior-stabilized (PS) total knee arthroplasty: a matched pair analysis of a classic and its evolutional design

Background: Total knee arthroplasty (TKA) designs continue to be modified to optimize patient's outcome. This study was designed to compare clinical and radiological results of classic worldwide used TKA posterior-stabilized (PS) design to those of its recent evolution. Methods: A consecutive group of 100 patients undergoing TKA using a classic cemented fixed-bearing PS TKA system was matched by age, gender, body max index to 100 patients having the newer cemented fixed-bearing PS design, both by the same manufacturer. Patients were assessed preoperatively, at 12 months and at 24 months minimum follow-up (range, 24-46) in a standard prospective fashion. The outcome assessments used were the Oxford Knee Score, the Knee Society Score, range of motion, and a satisfaction survey. A 2-sample t test comparing the 2 groups was performed. Results: No patients were lost at follow-up. At 2-year follow-up, differences in clinical and radiological Knee Society Score (P ¼ .09), Oxford Score (P ¼ .08), and overall satisfaction rate did not reach statistical significance. Implant group 2 showed a statistically significant decrease in postoperative anterior knee pain (P ¼ .006). At final follow-up, 16% of group 1 knees achieved > 130 flexion compared with 37% in group 2 (P ¼ .0009). There were 2 revisions for any reason in group 1 and none in group 2. Conclusions: Design modifications applied to the newer TKA system allowed greater flexion and lower patellofemoral complications but did not appear to achieve better overall clinical scores.