Wear Comparison of Fixed vs. Mobile Bearing Total Knee Replacements

INTRODUCTION: The debate between fixed-bearing and mobile-bearing systems continues due to the lack of clinical evidence showing survivorship of one to be superior to the other [1,2]. Delport et al report similar tibiofemoral kinematic patterns with respect to axial rotation during flexion and also femorotibial translation [3]. Conversely, Huang et al show a significant difference between the two systems in terms of the prevalence of osteolysis. His work showed that 47% of the mobilebearing knees had osteolysis, while only 13% of the fixed-bearing knees showed signs of osteolysis [4]. Literature states theoretical benefits to mobile-bearing systems in terms of wear because of the decoupling of motion onto two articulating surfaces [5]. However, Haider et al, using a force-controlled simulator, shows no difference in wear between fixed-bearing and mobile-bearing designs of the same knee system [5]. Additionally, a recent comparison of several commercially available systems using a displacement controlled simulator also showed no significant difference in wear rate between fixed-bearing and mobile-bearing systems [6]. The purpose of this study was to directly compare additional commercially available fixed-bearing and mobile-bearing systems on a displacement controlled knee simulator using normal walking kinematics.