State Key Laboratory of Advanced Design and Manufacture for Vehicle Body, Hunan University, Changsha, 410082, Hunan, China.
Aix-Marseille University, IFSTTAR, LBA UMRT24, Marseille, France.
Ann Biomed Eng. 2019 Dec;47(12):2356-2371. doi: 10.1007/s10439-019-02314-0. Epub 2019 Jul 1.
Plantar heel pain is one of the most common musculoskeletal disorders and generally causing long term discomfort of the patients. The objective of the present study is to combine in vivo experimental measurements and finite element modelling of the foot to investigate the influences of stiffness and thickness variation of individual plantar tissues especially the heel pad on deformation behaviours of the human foot. The stiffness and thickness variance of individuals were measured through supersonic shear wave elastography considering detailed heel pad layers refered to in literature as: dermis, stiffer micro-chamber layer, softer macro-chamber layer. A corresponding foot model with separated heel pad layers was established and used to a sensitivity analysis related to the variance of above-mentioned tissue characteristics. The experimental results show that the average stiffness of the micro-chamber layer ranged from 24.7 (SD 2.4) kPa to 18.8 (SD 3.5) kPa with the age group increasing from 20-29 years old to 60-69 years old, while the average macro-chamber stiffness is 10.6 (SD 1.5) kPa that appears to slightly decrease with the increasing age. Both plantar soft tissue stiffness and thickness of male were generally larger than that of female. The numerical simulation results show that the variance of heel pad strain level can reach 27.5% due to the effects of stiffness and thickness change of the plantar tissues. Their influences on the calcaneus stress and plantar pressure were also significant. This indicates that the most appreciate way to establish a personalized foot model needs to consider the difference of both individual foot anatomic geometry and plantar soft tissue material properties.
足底跟痛是最常见的骨骼肌肉疾病之一，通常会给患者带来长期的不适。本研究的目的是将体内实验测量和足部有限元模型相结合，研究个体足底组织（尤其是足跟垫）的刚度和厚度变化对人脚变形行为的影响。通过超声剪切波弹性成像测量个体的刚度和厚度变化，考虑到文献中提到的详细足跟垫层，即：真皮、较硬的微室层、较软的宏室层。建立了一个具有分离足跟垫层的相应足部模型，并用于与上述组织特征变化相关的灵敏度分析。实验结果表明，随着年龄组从 20-29 岁增加到 60-69 岁，微室层的平均刚度从 24.7（SD 2.4）kPa 增加到 18.8（SD 3.5）kPa，而平均宏室刚度为 10.6（SD 1.5）kPa，似乎随着年龄的增长而略有下降。男性足底软组织的刚度和厚度一般大于女性。数值模拟结果表明，由于足底组织的刚度和厚度变化的影响，足跟垫应变水平的变化幅度可达 27.5%。它们对跟骨应力和足底压力的影响也很显著。这表明，建立个性化足部模型最有效的方法需要考虑个体足部解剖几何形状和足底软组织材料特性的差异。
