Construction Of The Finite Element Model Of Human Foot And Its Individualized Research

Human biomechanical model is an important common foundation for research on human injury mechanism,pathology and design of corresponding prevention and treatment equipment.At present,the finite element models of the human foot have been widely used in the design of foot injury and patient mechanism,injury protection and rehabilitation medical equipments.The establishment and application of existing foot finite element models still have some deficiencies and limitations.For example,most of the tissue material parameters are obtained based on cadaver experiments,and the foot analysis is mostly based on quasi-static process and a common foot model.Therefore,this research aims at the deficiencies of the current modeling method and application,by combining medical ultrasound imaging to develop the foot model and its static,dynamic application,in order to lay the foundation for impact injury analysis,diabetic foot pathological mechanism and rehabilitation strategy research.The purpose of this article is to obtain the soft tissue material parameters of the in vivo foot,and to establish a individual foot finite element model that gives consideration to the differences in material and geometry,and to explore the mechanism of human foot injury through static station and gait simulation.First,based on the MRI image data of the foot and the HALL lower limb finite element model,the detailed foot model was estalished,and the model was validated with reference to the cavader foot compression experiment and the plantar pressure experiment.The results show that the RMS_errorof plantar deformation between the simulation and the experimental results is 0.22mm;the peak pressures predicted by the model are all within the range of the experimental results,the model has a high biological fidelity.Then,based on ultrasonic elastography（SWE）,50 volunteers’heel pad soft tissue characteristics measurement and related statistical analysis were completed.Then divided the soft tissue thickness and stiffness data into 6 levels,and run the static station simulation combined with the foot model.The numerical simulation results show that the variance of heel pad strain level can reach 16.7%due to the effects of stiffness change of the plantar tissues,and the change also causes a large gap in the results of plantar peak pressure.So,the variance in plantar soft tissue material characteristics have important influences on the biomechanical response of foot.Therefore,it is necessary to consider the individuation of soft tissue material characteristics in the establishment of individual foot model.Finally,based on the dual Kriging algorithm,two types of individual foot models were established refering to volunteer MRI images and optical scanning geometric data,respectively,and use the corresponding individual soft tissue characteristic data obtained by SWE experiment to complete the model gait validation.Further,the foot models of the five volunteers were analyzed by gait simulation.Then,compare the biomechanical response results of the two models,and evaluated the difference between the optical scan method and the MRI image method.The results show that the optical scan individual model can achieve the same biological fidelity level compare with the MRI scan model.Therefore,in the indiviadual model establishment process of the foot,the optical scan method can replace the MRI,thereby shortening the modeling period and achieving rapid establishment of.individual foot model.In this study,in-vivo foot experiments and individual geometric modeling were coupled to realize the individuation of the foot model both in materials and geometry,and the accuracy and feasibility of the optical scann method for individual modeling were evaluated.Finally,we established an accurate and efficient foot individuation method.This research will lay a theoretical foundation for the application of individual foot modeling,the analysis of foot sports injuries,and the design of foot medical equipment.