Influence of the Different Prosthesis Designs on Subjective Functional Evaluation after TKA: Medium-Term Outcome Using the 2011 Knee Society Score

Background: Patient-reported outcome (PRO) has become the focus of increased attention in the assessment of total knee arthroplasty (TKA). The purpose of this study was to investigate whether different prosthesis designs affected postoperative patient-reported performance. Materials and Methods: We reviewed 216 patients (234 knees) implanted with the Press-Fit Condylar Sigma prosthesis at our institution between January 2009 and December 2011. This study included 76 knees with fixed-bearing cruciate-retaining (FB-CR), 78 knees with fixed-bearing posterior-stabilized (FB-PS), and 80 knees with mobile-bearing posterior-stabilized (MB-PS) designs. The mean follow-up was 8.0 ± 0.74 years. Preoperative and follow-up ratings according to the 2011 Knee Society Score (2011 KSS), range of motion (ROM), and standing femoro-tibial angle (FTA) were obtained for all patients. Additionally, Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores were collected at last follow-up. Results: Three separate subscales of the 2011 KSS of the three cohorts were significantly improved post-operatively compared to the pre-operative values (p < 0.05), except for expectation scores. At the time of follow-up, significantly higher the 2011 Knee Society Functional Scores <2011 KSFS> (P = 0.016) were found in the PS group. In particular, there were significant differences in advanced activities of the 2011 KSFS among the three groups (P = 0.017). Satisfaction scores showed no difference among the three groups (P = 0.251). On the other hand, WOMAC and expectation scores were significantly better in the PS groups. (P = 0.003, P = 0.004). ROM in the MB-PS group (124.0°) was better than that in FB-PS (119.4°) and FB-CR (118.9°) (P = 0.005). On the other hand, additional surgery was needed in five PS knees. Conclusion: The PS prostheses had superior 2011 KSFS, expectation scores, WOMAC scores and ROM than the CR prostheses. In contrast, the postoperative prosthesis-related complication rates were lower with CR prostheses. Further detailed evaluation is necessary to determine whether the characteristics of the different prostheses affect PRO.