A Finite Element Study of the Stress on Metatarsals during Forefoot Strike at Different Angles

Objective: This paper studied the stress distribution on metatarsals during different forefoot strike angles on sagittal plane. Method: finite element model of human foot was built by hex elements and validated bybiomechanical test. The amplitude of boundary condition applied on foot FE model was from kinematic data of 3 D motion capture system. Result: lateral metatarsals had significant higher stress than medial at each loading stage. Same stress concentration was observed during different loading angles when the load is over body weight. The stress increasing rate on the 4 th metatarsal was more than 100% when the load increased from one bodyweight to two bodyweights. Unevenly distributed stress on metatarsals would be seen while forefoot strike angle at 5°or less, in which the average stress on 1 st metatarsal was lower than one third of the average value on the other four metatarsals. Stress concentration could happen at high forefoot strike angle (15°) even the loading was lower than half bodyweight. Conclusion: Forefoot strike angle should be controlled in a reasonable range in order to avoidstress fracture due to repetitive loading on the same high stress area which is beyond the functional adaptation of foot bones.