Camomilla Valentina, Cereatti Andrea, Vannozzi Giuseppe, Cappozzo Aurelio
Department of Human Movement and Sport Sciences, Istituto Universitario di Scienze Motorie, Piazza Lauro de Bosis, 15, 00194 Roma, Italy.
J Biomech. 2006;39(6):1096-106. doi: 10.1016/j.jbiomech.2005.02.008.
The functional method identifies the hip joint centre (HJC) as the centre of rotation of the femur relative to the pelvis during an ad hoc movement normally recorded using stereophotogrammetry. This method may be used for the direct determination of subject-specific HJC coordinates or for creating a database from which regression equations may be derived that allow for the prediction of those coordinates. In order to contribute to the optimization of the functional method, the effects of the following factors were investigated: the algorithm used to estimate the HJC coordinates from marker coordinates, the type and amplitude of the movement of the femur relative to the pelvis, marker cluster location and dimensions, and the number of data samples. This was done using a simulation approach which, in turn, was validated using experiments made on a physical analogue of the pelvis and femur system. The algorithms used in the present context were classified and, in some instances, modified in order to optimize both accuracy and computation time, and submitted to a comparative evaluation. The type of movement that allowed for the most accurate results consisted of several flexion-extension/abduction-adduction movements performed on vertical planes of different orientations, followed by a circumduction movement. The accuracy of the HJC estimate improved, with an increasing rate, as a function of the amplitude of these movements. A sharp improvement was found as the number of the photogrammetric data samples used to describe the movement increased up to 500. For optimal performance with the recommended algorithms, markers were best located as far as possible from each other and with their centroid as close as possible to the HJC. By optimizing the analytical and experimental protocol, HJC location error not caused by soft tissue artefacts may be reduced by a factor of ten with a maximal expected value for such error of approximately 1mm.
功能法将髋关节中心（HJC）确定为在通常使用立体摄影测量法记录的特定运动过程中股骨相对于骨盆的旋转中心。该方法可用于直接确定特定个体的HJC坐标，或用于创建一个数据库，从中可以推导出回归方程，以预测这些坐标。为了有助于功能法的优化，研究了以下因素的影响：用于从标记坐标估计HJC坐标的算法、股骨相对于骨盆的运动类型和幅度、标记簇的位置和尺寸以及数据样本数量。这是通过模拟方法完成的，反过来，又使用在骨盆和股骨系统的物理模拟模型上进行的实验进行了验证。对本文中使用的算法进行了分类，并在某些情况下进行了修改，以优化准确性和计算时间，并进行了比较评估。能得出最准确结果的运动类型包括在不同方向的垂直平面上进行几次屈伸/外展内收运动，然后进行环转运动。HJC估计的准确性随着这些运动幅度的增加而以递增的速率提高。当用于描述运动的摄影测量数据样本数量增加到500时，发现有显著改善。为了使用推荐算法获得最佳性能，标记最好彼此尽可能远离，并且它们的质心尽可能靠近HJC。通过优化分析和实验方案，由软组织伪影以外的因素导致的HJC定位误差可以减少到十分之一，这种误差的最大预期值约为1毫米。
