Department of Biomechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, the Netherlands.
J Biomech. 2010 Jul 20;43(10):1983-8. doi: 10.1016/j.jbiomech.2010.03.007. Epub 2010 Apr 10.
Inertial Magnetic Measurement Systems (IMMS) are becoming increasingly popular by allowing for measurements outside the motion laboratory. The latest models enable long term, accurate measurement of segment motion in terms of joint angles, if initial segment orientations can accurately be determined. The standard procedure for definition of segmental orientation is based on the measurement of positions of bony landmarks (BLM). However, IMMS do not deliver position information, so an alternative method to establish IMMS based, anatomically understandable segment orientations is proposed.
For five subjects, IMMS recordings were collected in a standard anatomical position for definition of static axes, and during a series of standardized motions for the estimation of kinematic axes of rotation. For all axes, the intra- and inter-individual dispersion was estimated. Subsequently, local coordinate systems (LCS) were constructed on the basis of the combination of IMMS axes with the lowest dispersion and compared with BLM based LCS.
The repeatability of the method appeared to be high; for every segment at least two axes could be determined with a dispersion of at most 3.8 degrees. Comparison of IMMS based with BLM based LCS yielded compatible results for the thorax, but less compatible results for the humerus, forearm and hand, where differences in orientation rose to 17.2 degrees.
Although different from the 'gold standard' BLM based LCS, IMMS based LCS can be constructed repeatable, enabling the estimation of segment orientations outside the laboratory.
A procedure for the definition of local reference frames using IMMS is proposed.
惯性磁测量系统（IMMS）越来越受欢迎，因为它允许在运动实验室之外进行测量。如果能够准确确定初始节段方向，最新的模型能够长期、准确地测量关节角度的节段运动。定义节段方向的标准程序基于骨骼标志点（BLM）的测量。然而，IMMS 不提供位置信息，因此提出了一种替代方法来建立基于 IMMS 的、解剖上可理解的节段方向。
对于 5 名受试者，在标准解剖位置收集 IMMS 记录，用于定义静态轴，并在一系列标准化运动中估计旋转运动轴的运动学轴。对于所有轴，估计了个体内和个体间的分散度。随后，基于 IMMS 轴与分散度最低的组合构建局部坐标系（LCS），并与基于 BLM 的 LCS 进行比较。
该方法的重复性似乎很高；对于每个节段，至少可以确定两个分散度最大为 3.8 度的轴。基于 IMMS 与基于 BLM 的 LCS 的比较结果对于胸部是一致的，但对于肱骨、前臂和手的结果则不一致，其方向差异高达 17.2 度。
尽管与基于 BLM 的“黄金标准”LCS 不同，但基于 IMMS 的 LCS 可以重复构建，从而能够在实验室外估计节段方向。
提出了一种使用 IMMS 定义局部参考框架的程序。
