Establishment Of A Foot-shoe Finite Element Model And Application In The Study Of The Plantar Fascia

Objective: To establish a complete foot-shoe three-dimensional finite element model and verify its validity;Then,by using the valid model,to simulate and analyze the mechanical response characteristics of plantar fascia to the hardness of the middle sole of running shoes,and to investigate the effect of midsole hardness on the mechanical response of plantar fascia.Methods: The experimental method,the finite element method and the comparative analysis method are mainly used for the study.The kinematics and dynamics parameters of the foot will be obtained by biomechanical experiments,which will be used to verify the validity of the foot-shoe finite element model and input the boundary conditions in the simulation of foot push action in running.Finite element method will be used to establish the foot-shoe model and to simulate the foot push action in running.Then,using the comparative analysis method,to explore the validity of foot-shoe finite element model and the effect of midsole hardness on the mechanical response characteristics of plantar fascia.Results:(1)A three-dimensional finite element model including foot soft tissue,bone,main ligaments,cartilage,five plantar fascia,running shoes model and ground support plate was established,which consisted of 344636 nodes and 442512 elements.(2)In the validation experiment of the foot-shoe finite element model,the measured peak value of sole pressure is 221 KPa,which mainly distributes in the sole part corresponding to the inner part of heel;the peak value of simulated sole pressure is 231 KPa,which is 10 Kpa larger than the measured result,and the error percentage is 4.33%,the peak pressure distribution area is basically consistent with the measured result;the total contact area of the simulated and measured sole pressure is similar,and the measured result is about 72 cm2 and the simulated result is about 70 cm2,which is 2 cm2 smaller than the measured result.The error percentage is 2.8%.The peak value of measured plantar pressure was 80 KPa,mainly located at the heel and the first metatarsophalangeal joint;the simulation results are 64 KPa,which is 16 KPa smaller than the measured results,and the error percentage is 20%;the distribution is the same as the measured results;the total contact area measured is about 111cm2 and the simulation result is about 131cm2 which is 20cm2 larger than the actual measurement,and the error percentage is about 18%.(3)In the instantaneous simulation experiment of the foot push action in running,the stress of plantar fascia decreases with the increase of midsole hardness.The maximum total stress of the five plantar fascia is about 6.881 Mpa when the midsole hardness is 10 degrees,and the minimum stress is about 6.769 Mpa when the midsole hardness is 50 degrees,with a difference of 0.112 Mpa.Overall,the medial sole hardness ranged from 10 degrees to 50 degrees,and the total stress of the five plantar fascia decreased by only about 1.62%.Conclusion:(1)The foot-shoe finite element model established in this study is highly similar to the actual foot-shoe geometry,and can achieve a more realistic response to the internal biomechanical characteristics between the foot and the “soleshoe full contact” running shoes.(2)At the moment of the foot push action in running,with the increase of the midsole hardness,the angle of metatarsophalangeal joint,the descending height of the arch of foot and the stress of the plantar fascia decrease,while the plantar pressure increases.(3)At the moment of the foot push action in running,the mechanical mechanism of the effect of midsole hardness on plantar fascia is related to the angle of metatarsophalangeal joint,the descending height of the arch of foot and the force exerted on the foot.