Department of Orthopedic Surgery, Huashan Hospital, Fudan University, No.12 Wulumuqi Middle Road, Shanghai, 200040, China.
Academy for Engineering & Technology, Fudan University, No.220 Handan Road, Shanghai, 200438, China.
BMC Musculoskelet Disord. 2022 Mar 15;23(1):254. doi: 10.1186/s12891-022-05197-w.
This study was aimed to develop a novel dynamic measurement technique for testing the material properties and investigating the effect of continuous compression load on the structural and mechanical properties of human heel pad during actual gait.
The dual fluoroscopic imaging system (DFIS) and dynamic foot-ground contact pressure-test plate were used for measuring the material properties, including primary thickness, peak strain, peak stress, elastic modulus, viscous modulus and energy dissipation rate (EDR), both at time zero and following continuous loading. Ten healthy pilot subjects, aged from 23 to 72 (average: 46.5 ± 17.6), were enrolled. A "three-step gait cycle" is performed for all subjects, with the second step striking at a marked position on the force plate with the heel to maintain the location of the tested foot to be in the view of fluoroscopes. The subjects were measured at both relaxed (time-zero group) and fatigue (continuous-loading group) statuses, and the left and right heels were measured using the identical procedures.
The peak strain, peak stress, elastic modulus, and EDR are similar before and after continuous load, while the viscous modulus was significantly decreased (median: 43.9 vs. 20.37 kPa•s; p < 0.001) as well as primary thicknesses (median: 15.99 vs. 15.72 mm; p < 0.001). Age is demonstrated to be moderately correlated with the primary thicknesses both at time zero (R = -0.507) and following continuous load (R = -0.607). The peak stress was significantly correlated with the elastic modulus before (R = 0.741) and after continuous load (R = 0.802). The peak strain was correlated with the elastic modulus before (R = -0.765) and after continuous load (R = -0.801). The correlations between the viscous modulus and peak stress/ peak strain are similar to above(R = 0.643, 0.577, - 0.586 and - 0.717 respectively). The viscous modulus is positively correlated with the elastic modulus before (R = 0.821) and after continuous load (R = 0.784).
By using dynamic fluoroscopy combined with the plantar pressure plate, the in vivo viscoelastic properties and other data of the heel pad in the actual gait can be obtained. Age was negatively correlated with the primary thickness of heel pad and peak strain, and was positively correlated with viscous modulus. Repetitive loading could decrease the primary thickness of heel pad and viscous modulus.
本研究旨在开发一种新的动态测量技术，用于测试人体足跟垫在实际步态中的材料特性，并研究连续压缩载荷对其结构和力学性能的影响。
采用双荧光透视成像系统（DFIS）和动态足底接触压力测试板测量材料特性，包括足跟垫的初始厚度、峰值应变、峰值应力、弹性模量、粘性模量和能量耗散率（EDR），分别在零时刻和连续加载后进行测量。共纳入 10 名年龄 23-72 岁（平均 46.5±17.6 岁）的健康飞行员。所有受试者均进行“三步步态周期”，第二步以脚跟撞击测力板上的标记位置，以保持受试脚的位置在荧光镜下可见。在放松（零时刻组）和疲劳（连续加载组）状态下对受试者进行测量，使用相同的程序测量左右足跟。
连续载荷前后峰值应变、峰值应力、弹性模量和 EDR 相似，而粘性模量显著降低（中位数：43.9 对 20.37 kPa•s；p<0.001），初始厚度也降低（中位数：15.99 对 15.72 mm；p<0.001）。年龄与零时刻（R=-0.507）和连续加载后（R=-0.607）的初始厚度呈中度相关。峰值应力与连续加载前（R=0.741）和后（R=0.802）的弹性模量显著相关。峰值应变与连续加载前（R=-0.765）和后（R=-0.801）的弹性模量相关。粘性模量与峰值应力/峰值应变的相关性与上述结果相似（R=0.643、0.577、-0.586 和-0.717）。粘性模量与连续加载前（R=0.821）和后（R=0.784）的弹性模量呈正相关。
通过使用动态荧光透视术结合足底压力板，可以在实际步态中获得足跟垫的粘弹性特性和其他数据。年龄与足跟垫的初始厚度和峰值应变呈负相关，与粘性模量呈正相关。重复加载会降低足跟垫的初始厚度和粘性模量。
