Construction Of Ankle And Foot Three-Dimensional Numerical Model And Analysis Of Finite Element Of Talus In Ectocondyle Unstable Situation

Purpose:To Create three-dimensional numerical model of ankle-foot joint(Finite element model).Based on this to analysis the rule of redistribution of talus's Von Mises stress when lateral ankle is in unstable situations,and to study the critical range of risk in talus.Methods:One normal healthy volunteers was performed ankle scan using GE light speed 16.The scanning range included whole ankle and distal tibiofibula.Using MATLAB and ANSYS software,to establish normal human ankle-foot three-dimensional numerical model.The applicability of the model was tested by applying load and boundary condition,and the data was compared with the other relative articles and clinical treatment study,to verify its validity.Based on the Finite element model of the normal people,adapt different restriction and loading regime,to construct different conditions of chronic extramalleolus unstablitied(53 in the unstable condition in the combination of the internal rotation ankle-foot and the varus).Result:1.Foot ankle orthogonal anisotropic three-dimensional numerical model was set(total node:96748.unit sum:488482).2.The major talus Von Mises stress mainly located in under normal walking condition on articulatio talonavicularis,neck of talus,evagination and processus aborolis of the talus,articulatio subtalaris and posterior articular facet of the tibial astragaloid joint,the maximum Von Mises stress is mainly on the evagination and processus aborolis of the talus.3.Comparing to the normal situation,the internal and rearward Von Mises stress decrease.The outside and the head and neck part was bigger.The bigger stress centers on the articulatio talonavicularis,neck of talus,evagination and processus aborolis of the talus.The range of the bigger stress become narrow,which leads to increases of the local stress. 4.Compared to the varus,the talus Von Mises stress is mainly affected by internal rotation.5.The talus fracture's risk value is within 60 mm internal rotation,the stress on the extramalleolus and the neck of talus will be over 80 MPa,(which was close to or above the bone eortex's yield limit(83 MPa)),when internal rotation larger than 60 mm and easily caused bone destruction. Conclusion:1.Establishment of a normal orthotropic finite element model of ankle-foot,with a high degree of geometric and physical similarity.2.Definition of the normal stress distribution of ankle-foot.3.When Chronic lateral ankle is instabe, the posterior talus has less stress than normal,head and neck and Lateral of talus has more stress and increased local stress,which was easy to cause Micro-fractures in intra-auricular and injury of surrounding cartilage.4.Internal rotation has a greater impact on the talus than Varus.Internal rotation should be mainly corrected when correcting clinically chronic lateral ankle instability,when internal rotation was more than 60 mm,lateral malleolus and talar neck was most common location to fracture.5. The model had provided a biomechanical basis for clinical treatment of chronic ankle instability.