Cedars-Sinai Medical Center, 8700 Beverly Blvd., DAV6006, Los Angeles, CA 90048, USA.
J Biomech. 2010 Oct 19;43(14):2822-9. doi: 10.1016/j.jbiomech.2010.05.034. Epub 2010 Jun 17.
One of the more common comparative tools used to quantify the motion of the vertebral joint is the orientation and position of the (finite) helical axis of motion as well as the amount of translation along, and rotation about, this axis. A survey of recent studies that utilize the helical axis of motion to compare motion before and after total disc replacement reveals a lack of concern for the relative errors associated with this metric. Indeed, intrinsic algorithmic and experimental errors that arise when interpreting motion tracking data can easily lead to a misinterpretation of the changes caused by replacement disc devices. While previous studies examining these errors exist, most have overlooked the errors associated with the determination of the location of the helical axis and its intersection with a chosen plane. The purpose of the study presented in this paper was to evaluate the sensitivity and reliability of the helical axis of motion as a comparative tool for kinematically evaluating spinal prostheses devices. To this end, we simulated a typical spine biomechanics testing experiment to investigate the accuracy of calculating the helical axis and its associated parameters using several popular algorithms. The resultant data motivated the development of a new algorithm that is a hybrid of two existing algorithms. The improved accuracy of this hybrid method made it possible to quantify some of the changes to the kinematics of a spinal unit that are induced by distinct placements of a total disc replacement.
一种常用于量化椎骨关节运动的更常见的比较工具是运动的（有限）螺旋轴的方向和位置，以及沿该轴的平移量和旋转量。对利用螺旋运动轴来比较全椎间盘置换前后运动的最新研究进行的调查显示，人们对该指标相关的相对误差缺乏关注。事实上，在解释运动跟踪数据时出现的内在算法和实验误差很容易导致对置换盘装置引起的变化的误解。虽然已经存在检查这些误差的先前研究，但大多数研究都忽略了与确定螺旋轴的位置及其与所选平面的交点相关的误差。本文介绍的研究旨在评估运动螺旋轴作为一种运动学评估脊柱假体装置的比较工具的灵敏度和可靠性。为此，我们模拟了一个典型的脊柱生物力学测试实验，以研究使用几种流行算法计算螺旋轴及其相关参数的准确性。所得数据促使开发了一种新算法，该算法是两种现有算法的混合算法。该混合方法的改进精度使得可以量化由全椎间盘置换的不同位置引起的脊柱单元运动学的一些变化。
