Biomechanics of Calcaneus Impacted by Talus: A Dynamic Finite Element Analysis

Abstract BackgroundThe biomechanics of calcaneus impacted by the talus are unclear. We aimed to evaluate the biomechanical effect of the talus impacting on the calcaneus at different falling speed, and analyze the factors affecting calcaneal fracture.Methods A finite element model including the talus, calcaneus and ligaments was built using a variety of three-dimensional reconstruction software. The method of explicit dynamics was used to analyze the process of the talus impacting the calcaneus. Stress values of the posterior, middle, and anterior subtalar articular surface(PSAS, ISAS, ASAS), the calcaneocubic articular surface(CAS), the bottom of the calcaneus(BC), the medial wall (MW)and lateral wall (LW) of the calcaneus were extracted. Stress quantity and distribution changes in various parts of the calcaneus changed with speed were analyzed.ResultsPosterior subtalar articular surface reached the peak stress first during the process of talus impacting the calcaneus. The stress was mainly concentrated on the PSAS, ASAS, MW and GA. Comparing with the speed of 5m/s, the average maximum stress increased in each region of the calcaneus were: PSAS 73.81%, ISAS 7.11%, ASAS 63.57%, GA 89.10%, LW 140.16%, CAS 140.58%, BC 137.67%, MW 135.99% at a speed of 10m/s. The regions where the stress were concentrated changed, and the magnitude and sequence of stress peaks of calcaneus changed with speed also during the impact.Conclusion The falling speed affected the value and distribution of stress of the calcaneus, which was the most important factor leading to a calcaneal fracture. The magnitude and sequence of stress peaks might be important factors in determining the beginning and direction of fracture lines.