Hamai Satoshi, Miura Hiromasa, Higaki Hidehiko, Shimoto Takeshi, Nakanishi Yoshitaka, Iwamoto Yukihide
Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
J Orthop Sci. 2008 Nov;13(6):543-9. doi: 10.1007/s00776-008-1277-8. Epub 2008 Dec 17.
The purpose of this study was to investigate the kinematics of the polyethylene insert in two designs of mobilebearing total knee arthroplasty, using a six-degrees-of-freedom knee simulator. It was consequently not clear whether the motion of the polyethylene bearing in mobile-bearing total knee arthroplasty could be demonstrated during the gait cycle or more rapid movement.
A mobile-bearing knee (Zimmer) and a low contact stress rotating-platform design (Depuy) were mounted on a simulator which was regulated by the kinematic data of gait. The simulating test was conducted under a static condition as well as under dynamic conditions of 0.5 Hz and 1.0 Hz. We recorded the motions of the implants with two charge-coupled device (CCD) cameras, and the positions of the insert were calculated.
In spite of the same relative motion between the femoral component and the tibial tray, the polyethylene insert showed unique relative motion according to the given condition. The motion of the insert during the dynamic conditions was considerably decreased in comparison to the static condition in both mobile-bearing designs. In addition, the insert showed a smaller amplitude and frequency of rotations under increasing speed in the low contact stress rotating-platform design. The low contact stress rotating-platform design showed a larger amplitude and frequency of rotations than the mobilebearing knee.
Despite the mobility of the insert in the mobilebearing total knee arthroplasty, the motion of the insert was decreased during dynamic conditions because of the disruption of full contact between the femoral component and the polyethylene insert. Differences in the rotation between the mobile-bearing knee and the low contact stress rotatingplatform design were due to the fixed axis of the internalexternal rotation in the low contact stress rotating-platform design. The theoretical advantages for the mobile-bearing design over the fixed-bearing design were not demonstrated in this study.
本研究的目的是使用六自由度膝关节模拟器，研究活动平台全膝关节置换术两种设计中聚乙烯垫片的运动学。因此，尚不清楚在步态周期或更快运动过程中，活动平台全膝关节置换术中聚乙烯垫片的运动是否能够得到证实。
将一个活动平台膝关节（Zimmer）和一个低接触应力旋转平台设计（Depuy）安装在一个由步态运动学数据调节的模拟器上。模拟测试在静态条件以及0.5Hz和1.0Hz的动态条件下进行。我们用两台电荷耦合器件（CCD）相机记录植入物的运动，并计算垫片的位置。
尽管股骨部件和胫骨托之间的相对运动相同，但聚乙烯垫片根据给定条件显示出独特的相对运动。在两种活动平台设计中，动态条件下垫片的运动与静态条件相比均显著降低。此外，在低接触应力旋转平台设计中，随着速度增加，垫片的旋转幅度和频率变小。低接触应力旋转平台设计显示出比活动平台膝关节更大的旋转幅度和频率。
尽管在活动平台全膝关节置换术中垫片具有可动性，但由于股骨部件与聚乙烯垫片之间的完全接触受到破坏，动态条件下垫片的运动减少。活动平台膝关节和低接触应力旋转平台设计之间旋转的差异是由于低接触应力旋转平台设计中外旋内旋的固定轴。本研究未证明活动平台设计相对于固定平台设计的理论优势。
