Sanchis-Sales Enrique, Sancho-Bru Joaquin L, Roda-Sales Alba, Pascual-Huerta Javier
J Am Podiatr Med Assoc. 2016 Jan-Feb;106(1):37-46. doi: 10.7547/14-141.
Dynamic stiffness can be used for studying foot pathologic abnormalities and for developing prostheses and orthoses. Although previous works have studied the role of ankle joint stiffness during gait, other foot joints have not yet been analyzed. We sought to characterize the dynamic stiffness of the ankle, midtarsal, and metatarsophalangeal joints during normal walking.
Kinematics and contact data from four healthy individuals during walking were registered with a three-dimensional motion analysis system and a pressure platform. Stance phases with flexion moment-angle linear relationships were identified, and dynamic stiffnesses were calculated from the slope of their linear regressions. Intraparticipant repeatability was analyzed using analyses of variance, and interparticipant variability was checked through the SD of averaged participant stiffnesses.
Flexion moment-angle linear relationships were identified (R(2) > 0.98) during the early and late midstance phases and the propulsion phase at the ankle (2.76, 5.23, and 3.42 N·m/kg/rad, respectively) and midtarsal (15.88, 3.90, and 4.64 N·m/kg/rad, respectively) joints. At the metatarsophalangeal joint, a linear relationship (R(2) > 0.96) occurred only during the propulsion phase (0.11 N·m/kg/rad). High dynamic stiffness variability was observed during the late and early midstance phases at the ankle and midtarsal joints, respectively.
These results may serve as a basis for future studies aimed at investigating the role of dynamic stiffness identified herein in different foot disorders. The importance of properly controlling the samples in such studies is highlighted. Study of the dynamic stiffnesses identified might be used in the design of prostheses, orthoses, and other assistive devices.
动态刚度可用于研究足部病理异常以及开发假肢和矫形器。尽管先前的研究已经探讨了踝关节刚度在步态中的作用，但尚未对其他足部关节进行分析。我们旨在描述正常行走过程中踝关节、中跗关节和跖趾关节的动态刚度特征。
使用三维运动分析系统和压力平台记录四名健康个体行走时的运动学和接触数据。识别出具有屈曲力矩 - 角度线性关系的站立阶段，并根据其线性回归的斜率计算动态刚度。使用方差分析分析个体内重复性，并通过平均参与者刚度的标准差检查个体间变异性。
在踝关节（分别为2.76、5.23和3.42 N·m/kg/rad）和中跗关节（分别为15.88、3.90和4.64 N·m/kg/rad）的站立中期早期、站立中期后期和推进阶段，均识别出屈曲力矩 - 角度线性关系（R²>0.98）。在跖趾关节，仅在推进阶段出现线性关系（R²>0.96，0.11 N·m/kg/rad）。分别在踝关节和中跗关节的站立中期后期和早期观察到较高的动态刚度变异性。
这些结果可为未来旨在研究本文确定的动态刚度在不同足部疾病中的作用的研究提供基础。强调了在此类研究中正确控制样本的重要性。对所确定的动态刚度的研究可用于假肢、矫形器和其他辅助装置的设计。
