Lewis Gregory S, Cohen Tamara L, Seisler Andrea R, Kirby Kevin A, Sheehan Frances T, Piazza Stephen J
Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802, USA.
J Biomech. 2009 Jan 19;42(2):146-51. doi: 10.1016/j.jbiomech.2008.10.010. Epub 2008 Nov 17.
The subtalar joint is important in frontal plane movement and posture of the hindfoot. Abnormal subtalar joint moments caused by muscle forces and the ground reaction force acting on the foot are thought to play a role in various foot deformities. Calculating joint moments typically requires knowledge of the location of the joint axis; however, location of the subtalar axis from measured movement is difficult because the talus cannot be tracked using skin-mounted markers. The accuracy of a novel technique for locating the subtalar axis was assessed in vivo using magnetic resonance imaging. The method was also tested with skin-mounted markers and video motion analysis. The technique involves applying forces to the foot that cause pure subtalar joint motion (with negligible talocrural joint motion), and then using helical axis decomposition of the resulting tibiocalcaneal motion. The resulting subtalar axis estimates differed by 6 degrees on average from the true best-fit subtalar axes in the MRI tests. Motion was found to have been applied primarily about the subtalar joint with an average of only 3 degrees of talocrural joint motion. The proposed method provides a potential means for obtaining subject-specific subtalar axis estimates which can then be used in inverse dynamic analyses and subject-specific musculoskeletal models.
距下关节在足后段的额状面运动和姿势中起着重要作用。由作用于足部的肌肉力量和地面反作用力引起的异常距下关节力矩被认为在各种足部畸形中起作用。计算关节力矩通常需要了解关节轴的位置；然而，通过测量运动来确定距下轴的位置很困难，因为无法使用贴在皮肤上的标记追踪距骨。使用磁共振成像在体内评估了一种用于定位距下轴的新技术的准确性。该方法还通过贴在皮肤上的标记和视频运动分析进行了测试。该技术包括对足部施加力，使距下关节产生纯运动（胫距关节运动可忽略不计），然后对由此产生的胫跟运动进行螺旋轴分解。在MRI测试中，得到的距下轴估计值与真正的最佳拟合距下轴平均相差6度。结果发现运动主要围绕距下关节进行，胫距关节平均仅有3度的运动。所提出的方法为获得特定个体的距下轴估计值提供了一种潜在手段，然后可用于逆动力学分析和特定个体的肌肉骨骼模型。
