Clinical relevance of roll-back replacement of ultra congruent total knee arthroplasty: comparison of mid-term outcomes with posterior stabilizing design

IntroductionThe outcomes of total knee arthroplasty (TKA) remain controversial, and we do not know which factors are important for successful outcomes. This study aimed to compare the mid-term outcomes of different conceptual designs by evaluating the radiological and clinical outcomes.Materials and methodsA total of 478 total knee arthroplasties (TKAs) were enrolled and allocated into groups I [posterior stabilizing (PS) with anterior referencing (AR)], II [PS with posterior referencing (PR), and III [ultra-congruent (UC) TKA)]. Preoperative findings, last follow-up clinical outcomes, and final follow-up radiological and indirect assessments of the femoral rollback were compared between the groups.ResultsThe mean follow-up period was 72.6 & PLUSMN; 12.9 months. The tourniquet was used samely applied to every group. Flexion contracture was significantly larger in group III than in groups I and II (3.3 & PLUSMN; 2.7, p < 0.001), and further flexion was significantly smaller in group III (130.0 & DEG; & PLUSMN; 2.7 & DEG;, p < 0.001). Among the radiological parameters, posterior osteophyte formation was the most common in group III (67.8%). The rollback distance was significantly smaller in group III than in groups I and II (p < 0.001). The active deep flexion angle was affected by the posterior condylar offset (PCO) ratio, and the contact point changed the distance (p < 0.05).ConclusionPS TKAs showed better ROMs than UC TKAs; however, no differences were noted in the clinical outcome scales. The flexion angle was affected by the PCOR and rollback at both PS and UC TKAs. However, rollback negatively affected the flexion angle during UC TKAs. An inappropriate femoral rollback was identified, and femoral osteophyte formation was determined to be the most prominent in UC TKAs.