Adamczyk Peter G, Roland Michelle, Hahn Michael E
J Biomech Eng. 2013 Oct 1;135(10):104502-5. doi: 10.1115/1.4025104.
Lower limb amputee gait during stance phase is related to the angular stiffness of the prosthetic foot, which describes the dependence of ankle torque on angular progression of the shank. However, there is little data on angular stiffness of prosthetic feet, and no method to directly measure it has been described. The objective of this study was to derive and evaluate a method to estimate the angular stiffness of prosthetic feet using a simple linear compression test. Linear vertical compression tests were performed on nine configurations of an experimental multicomponent foot (with known component stiffness properties and geometry), which allowed for parametric adjustment of hindfoot and forefoot stiffness properties and geometries. Each configuration was loaded under displacement control at distinct pylon test angles. Angular stiffness was calculated as a function of the pylon angle, normal force, and center of pressure (COP) rate of change with respect to linear displacement. Population root mean square error (RMSE) between the measured and predicted angular stiffness values for each configuration of the multicomponent foot was calculated to be 4.1 N-m/deg, dominated by a bias of the estimated values above the predicted values of 3.8 ± 1.6 N-m/deg. The best-fit line to estimated values was approximately parallel to the prediction, with R2 = 0.95. This method should be accessible for a variety of laboratories to estimate angular stiffness of experimental and commercially available prosthetic feet with minimal equipment.
下肢截肢者在站立期的步态与假肢足部的角刚度有关，角刚度描述了踝关节扭矩与小腿角位移的关系。然而，关于假肢足部角刚度的数据很少，且尚未描述直接测量它的方法。本研究的目的是推导并评估一种使用简单线性压缩试验来估计假肢足部角刚度的方法。对一种实验性多部件足部的九种配置进行了线性垂直压缩试验（该足部具有已知的部件刚度特性和几何形状），这允许对后足和前足的刚度特性及几何形状进行参数调整。每种配置在不同的塔架测试角度下进行位移控制加载。角刚度根据塔架角度、法向力以及相对于线性位移的压力中心（COP）变化率来计算。计算出多部件足部每种配置的测量角刚度值与预测角刚度值之间的总体均方根误差（RMSE）为4.1 N·m/°，主要是由于估计值高于预测值，偏差为3.8±1.6 N·m/°。估计值的最佳拟合线与预测线大致平行，R² = 0.95。这种方法对于各种实验室来说应该都可以采用，只需最少的设备就能估计实验性和市售假肢足部的角刚度。
