van Duren B H, Pandit H, Beard D J, Zavatsky A B, Gallagher J A, Thomas N P, Shakespeare D T, Murray D W, Gill H S
Nuffield Department of Orthopaedic Surgery, Botnar Research Centre, Nuffield Orthopaedic Ctr, University of Oxford, Oxford, OX3 7LD, UK; Department of Engineering Science, University of Oxford, UK.
J Biomech. 2007;40 Suppl 1:S31-7. doi: 10.1016/j.jbiomech.2007.02.016. Epub 2007 Apr 12.
Newer designs of total knee arthroplasty (TKA), through the use of added degrees of constraint, attempt to provide a "guided motion" to restore more normal and predictable kinematics. Two such design philosophies are the posterior stabilised (PS) using a cam-post and the medial pivot (MP) concepts. Knee kinematics of 12 patients with a PS TKA, 13 subjects with a MP TKA and 10 normal subjects were compared. For kinematic assessment, patients underwent fluoroscopic assessment of the knee during a step-up exercise and deep knee bend. Fluoroscopic images were corrected for distortion and assessed using 3D model fitting to determine relative 3D motion, and a 2D method to measure the patellar tendon angle (PTA) as function of knee flexion. For the PS design the cam-post mechanism engaged between 70 degrees and 100 degrees flexion. Between extension and 50 degrees there was forward motion of the contact points. Beyond 60 degrees both condyles rolled moved posteriorly. The majority of the external rotation of the femur occurred between 50 degrees and 80 degrees . The PTA was lower than normal in extension and higher than normal in flexion. The MP exhibited no anterior movement throughout the rage of motion. The medial condyle moved minimally. The lateral contact point moved posteriorly from extension to flexion. The femur rotated externally throughout the range of flexion analysed. The PTA was similar to normal from extension to mid flexion and then higher than normal beyond to high flexion. The PS design fails to fully restrain paradoxical anterior movement and although the cam engages, it does not contribute significantly to overall rollback. The MP knee does not show significant anterior movement, the medial pivot concept appears to achieve near normal kinematics from extension to 50 degrees of knee flexion. However, the results show that at high flexion this design does not achieve normal knee kinematics.
全膝关节置换术（TKA）的新型设计通过增加约束程度，试图提供一种“引导运动”，以恢复更正常和可预测的运动学。两种这样的设计理念是使用凸轮 - 柱的后稳定型（PS）和内侧旋转型（MP）概念。比较了12例接受PS TKA的患者、13例接受MP TKA的受试者和10例正常受试者的膝关节运动学。为了进行运动学评估，患者在进行上台阶运动和深屈膝时接受膝关节的荧光透视评估。对荧光透视图像进行失真校正，并使用三维模型拟合进行评估，以确定相对三维运动，并采用二维方法测量髌腱角（PTA）作为膝关节屈曲的函数。对于PS设计，凸轮 - 柱机制在屈曲70度至100度之间起作用。在伸展和50度之间，接触点向前移动。超过60度时，两个髁均向后滚动移动。股骨的大部分外旋发生在50度至80度之间。PTA在伸展时低于正常，在屈曲时高于正常。MP在整个运动范围内均未表现出向前运动。内侧髁移动最小。外侧接触点从伸展到屈曲向后移动。在分析的整个屈曲范围内，股骨均向外旋转。PTA从伸展到中度屈曲时与正常相似，然后在超过中度屈曲到高度屈曲时高于正常。PS设计未能完全抑制反常的向前运动，尽管凸轮起作用，但对整体后滚的贡献不大。MP膝关节未显示明显的向前运动，内侧旋转概念似乎在膝关节从伸展到50度屈曲时实现了接近正常的运动学。然而，结果表明，在高度屈曲时，这种设计并未实现正常的膝关节运动学。
