The effects of gastrocnemius-soleus muscle forces on ankle biomechanics during triple arthrodesis

This paper presents a finite element model of the ankle, taking into account the effects of muscle forces, determined by a musculoskeletal analysis, to investigate the contact stress distribution in the tibio-talar joint in patients with triple arthrodesis and in normal subjects. Forces of major ankle muscles were simulated and corresponded well with the trend of ‎their EMG signals. These forces were applied to the finite element model to obtain stress distributions for patients with triple arthrodesis and normal subjects in three stages of the gait cycle, i.e. heel strike, midstance and heel rise. The results demonstrated that the stress distribution patterns of the tibio-talar joint in patients with triple arthrodesis differ from those of normal subjects in investigated gait cycle stages. The results also indicate that, in patients with triple arthrodesis, increasing gastrocnemius-soleus muscle force reduces the stress on the medial malleolus compared with normal subjects.