Three-Dimensional Finite Element Analysis And Clinical Significance Of Calcaneus

Objective:To establish the model of calcaneus by the method of the three-dimensional finite element,and calculate the various nodes stress of models under different loaded condition.To discuss the biomechanics and fracture mechanism of calcaneus,then select different internal fixations totest and compare their performance,for providing guides to the treating of calcaneus fracture.Method:To scan the calcaneum screw CT of normal person,simulate the boundary conditions accurately and establish the model of calcaneus by the SAP-93 software.To discuss the calcaneus' force condition under the force condition of achilles tendon,talus and cuboid bone when the ankle joint in neutral position and back stretches 20°position,and discuss which kind of fracture be occured under the two conditions.To use the three internal fixations—calcaneal plateⅠ,calcaneal plateⅡ,calcaneal plateⅢrespectively to fix the calcaneus and compare their performance.Results:Model of calcaneus in neutral position were as follows:node stress of 206,217,529,544,884,902,1538,1549 and 1764 were bigger than nodes' aroud them;While in dorsal extension 20°position,node stress of 206,217,529,543,546,1009,1013,1398,1486 and 1806 were bigger than nodes' around them.(1)The stress distribution of plateⅠ,plateⅡand plateⅢin neutral position was not even.Front stress distribution of plate was all higher than posterior.The stress distribution of plateⅡwas not most uniform,and the mean stress distribution was 16.12MPa.The maximum stress distribution was 127.90Mpa.The stress distribution of plateⅠwas more uniform than plateⅡand plateⅢ.The mean stress distribution was 10.58MPa.The maximum stress distribution was 31.40Mpa.The stress distribution of plateⅢwas between plateⅡand plateⅢ.The mean stress distribution of plateⅢwas 14.24MPa.The maximum stress distribution of plateⅢwas 102.60Mpa.The stress distribution of plates at anterior fracture fragments were basically identical using plateⅠ,plateⅡor plateⅢ. While there was a great discrepancy between plateⅢand normal calcaneus';there was no difference among plateⅠ,plateⅡand normal calcaneus'.(2)The stress distribution of plateⅠ,plateⅡand plateⅢunder dorsal extension 20°position was not even.Front stress distribution of plate was all higher than posterior.The stress distribution of plateⅡwas not most uniform.The mean stress distribution was 9.77MPa.The maximum stress distribution was 60.67Mpa.The stress distribution of plateⅠwas more uniform than plateⅡand plateⅢ. The mean stress distribution was 3.56MPa.The maximum stress distribution was 12.41Mpa. The stress distribution of plateⅢwas between plateⅡand plateⅢ.The mean stress distribution of plateⅢwas 2.90MPa.The maximum stress distribution of plateⅢwas 16.46Mpa.The stress distribution of plates at post section of near calcaneocuboidal joint and front section of middle fracture fragments were basically identical using plateⅠ,plateⅡor plateⅢ.Conclusion:The line passed by outboard articular facet of talocalcaneal joint when the ankle joint was in neutral position,and the stress distribution was maximal at calcaneus from internal post to forward outside.In addition,the stress distribution was very great from calcaneus to position between post spur joint and calcaneal tendon when back stretches 20°.The stress distribution of plateⅠwas even,which corresponds with the principle of biomechanics.