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Online ISSN 1827-1707
Li G., Kozanek M., Varadarajan K. M., Rubash H. E.
Bioengineering Lab, Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, MA, USA
Aim. The aim of this study was to summarize the knowledge regarding total knee arthroplasty (TKA) biomechanics generated over the last decade in our laboratory through the use of in vitro robotic and in vivo imaging approaches.
Methods. The in vitro approach involves the use of a robotic system to measure changes in knee biomechanics following TKA under simulated muscle forces. A non-invasive dual fluoroscopic imaging technique was also developed to study TKA biomechanics in vivo.
Results. Native knees showed posterior femoral translation with flexion, and “screw home” tibial rotation between 0-30° flexion. In contrast, both Cruciate-retaining (CR) and Posterior-substituting (PS) TKAs showed anterior femoral translation at low flexion, reduced posterior femoral translation, and loss of “screw home” rotation. The high-flexion TKA designs facilitated more congruent contact but did not provide greater range of flexion or more normal kinematics. Mobile and Fixed bearing TKAs showed similar kinematics. A competent PCL was important for CR TKA, although PCL force in CR TKA was lower than in intact knees. In PS TKA, anterior tibial post contact was observed during hyper-extension. Additionally, cam-post engagement occurred during 70 - 100° flexion and disengagement occurred beyond 130° flexion.
Conclusion. The in-vitro robotic and in-vivo fluoroscopic techniques have helped develop a better understanding of various aspects of TKA biomechanics.