The Study On The Mechanisms Of Ankle Injuries Based On The Finite Element Methods And THUMS Model

Objective:Ankle injuries are common injuries in forensic examinations,which are mainly caused by falling and traffic accidents.Determining the mechanisms and manners of ankle injuries is a critical and challenging problem for forensic experts due to complexity of anatomical structure and injury conditions.In this study,numerical simulation was employed to reconstruct the ankle joint injury process in the case of fall and impact.By analyzing the changes of biomechanical indexes and reproducing the injury process in the form of pictures and animations,we explored the main mechanism and morphology of ankle joint injury from the perspective of biomechanics.Systematic studies will be helpful in reconstructing the ankle injury processes and analyzing the mechanisms in forensic practice,providing a deeper understanding of ankle injury mechanisms for forensic experts.Methods:This study based on THUMS 4.0 finite element human model,which has been validated comprehensively.LS-DYNA,an explicit dynamic analysis system,and a pre and post processing module called LS-PrePost was employed to calculated the stress,strain and others mechanical indicators of different parts on ankle joint under various loading conditions.In this way,we can reconstruct biomechanical response when ankle injuries occurs.Finally,we will show the injury morphologies and mechanisms under different injury conditions in the form of image,animation and biomechanical indicators.Result:The results show that vertical falling causes a specific compression fracture of the distal tibia after falling in a natural position,which is caused by being hit by the talus.However,with a lower fall height or larger angle of the ankle postures,the foot will slide relative to the ground,causing insufficient interaction between the talus and the tibia.Simultaneously,foot sliding will cause a large bending moment and torsion in the middle and lower segments of the tibia and fibula diaphysis,leading to diaphysis fractures.The ankle ligament injuries caused by falling are widely,while ligament injuries caused by impact is limited.Inclination positions is more likely to result in Pilon fractures than leaning forward and backward.The ankle impacts cannot form compression fractures in the distal tibia,which is one of the main differences from typical ankle injuries caused by falling.The mechanism of ankle injuries caused by impacts mainly contains fractures on direct impact sites,ankle ligament ruptures and avulsion fractures on the medial or lateral malleolus caused by over flexion,extension or eversion of the ankle.Moreover,the further the impact is from the ankle joint,the more slight ankle injuries.In forensic practice,according to the fracture morphologies of lower limb and soft tissue injuries,it is not difficult to distinguish the ankle injuries caused by impact from that caused by falling.Conclusion:Human finite elements model and explicit dynamic analysis can help to reproduce ankle injuries truly and intuitively.Furthermore,the injury methods and mechanism can be judged accurately.Our results provide a reference for explaining the mechanism and methods of ankle joint injuries in forensic practice.