A Point Cluster Method for In Vivo Motion Analysis: Applied to a Study of Knee Kinematics
A Point Cluster Method for In Vivo Motion Analysis: Applied to a Study of Knee Kinematics
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DOI：
10.1115/1.2834888
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发表时间：
1998-12-01
影响因子：
1.7
通讯作者：
Dyrby, C
中科院分区：
文献类型：
--
作者：
Andriacchi, TP;Alexander, EJ;Dyrby, C
描述了一种从皮肤上放置的标记提取肢体节段运动的新方法。该方法为确定与放置在皮肤上的点的非刚体运动相关联的伪影提供了基础。该方法基于均匀分布在肢体节段上的一组点。每个点都被分配了一个任意质量。计算了该点群的质心和惯性张量，利用惯性张量的特征值和特征向量定义了该点群中的坐标系，为评价非刚体运动提供了依据。如果节段表现为刚体，则惯性张量的特征值保持不变，从而为确定非刚体运动的变化提供了基础。该方法在一个仿真模型中进行了测试，在该模型中，系统和随机误差仅被引入到固定的点群中。仿真结果表明，非刚体运动引起的误差可以大大减小。该方法还在10名正常受试者的步行过程中进行了评估。从点群方法获得的膝关节旋转和平移的结果与之前在股骨和胫骨放置皮质内钉的正常受试者相比是有利的。本文描述的方法为使用基于皮肤的标记系统测量活体运动提供了一种独特的方法。
A new method for deriving limb segment motion from markers placed on the skin is described. The method provides a basis for determining the artifact associated with nonrigid body movement of points placed on the skin. The method is based on a cluster of points uniformly distributed on the limb segment. Each point is assigned an arbitrary mass. The center of mass and the inertia tensor of this cluster of points are calculated The eigenvalues and eigenvectors of the inertia tensor are used to define a coordinate system in the cluster as well as to provide a basis for evaluating non-rigid body movement. The eigenvalues of the inertia tensor remain invariant if the segment is behaving as a rigid body, thereby providing a basis for determining variations for nonrigid body movement. The method was tested in a simulation model where systematic and random errors Mere introduced into a fixed cluster of points. The simulation demonstrated that the error due to nonrigid body movement could be substantially reduced. The method was also evaluated in a group of ten normal subjects during walking. The results for knee rotation and translation obtained from the point cluster method compared favorably to results previously obtained from normal subjects with intra-cortical pins placed into the femur and tibia. The resulting methodology described in this paper provides a unique approach to the measurement of in vivo motion using skin-based marker systems.