Abstract
Summary
UC TKA showed similar anteroposterior translation and more femoral external rotation of earlier onset when compared to PS TKA.
Introduction
Recently highly conforming ultracongruent TKA has been reintroduced with improved wear characteristics and lower complications. The purpose of the study was to assess kinematics and clinical outcome of posterior stabilized and ultracongruent rotating-platform mobile bearing TKA.
Methods
Ninety patients with primary osteoarthritis of the knee were randomized to undergo computer assisted TKA with PS(n = 45) or UC(n = 45) prostheses and were followed up for a minimum 2 years. The passive kinematic evaluation was performed before and after implantation with a navigation system. Three parameters of tibiofemoral relationship (anterior/posterior translation, varus/valgus alignment and rotation) were recorded from 0° to 120° of flexion. The patients were clinically and radiographically evaluated at final follow-up.
Results
Paradoxical anterior translation of the femur was observed from 0° to 70° of flexion in PS(8.7mm) and 0° to 85° in UC knees(10.4mm, p = 0.064). The distance of femoral roll-back was 6.7mm and 5.5mm, but never reached the starting point. Paradoxical internal rotation of the femur was found from 0° to 62° of flexion in PS(9.9°) and 0° to 47° in UC knees(5.6°, p = 0.002). UC knees showed more external rotation of the femur during flexion from 0° to 120°(5.7:11.0, p = 0.048). There was no significant difference in the maximal flexion(123.3°:125.5°, p = 0.366), AKS knee scores(95.9:92.0, p = 0.101), AKS function scores(86.2:82.9, p = 0.435) and WOMAC index scores(13.4:15.9, p = 0.268). There was no progressive radiolucent line or loosening in all knees.
Discussion and Conclusion
UC TKA showed similar anteroposterior translation and more femoral external rotation of earlier onset when compared to PS TKA. There was no difference in clinical outcome between two designs. UC TKA showed comparable kinematic and clinical results to PS TKA.
