Analysis Of Typeâ…¡ Odontoid Process Fracture Fixed With Anterior Odontoid Screw On A Finite Element Model

Objective:To establish the finite element model of typeâ…¡odontoid process fracture fixed with anterior odontoid screw,to observe the condition of atlanto-axisal biomechanics and the stress of the screw.Methods:(1)The coordinate data was got by SCT.Then the picture data was converted to ASCII cloudy point.The point data was deal with GEOMAGIC STUDIO software.(2) UG were used to establish geometry model.The pre-post was carried out by HYPERMESH and LS-DYNA.In UG software,the odontoid of geometry model of normal atlanto-axis was broken so that the pathology model was established, meanwhile,the geometry model of the screw was also created,then two were imported in HYPERMESH and LS-DYNA,the final postoperative finite element model had finished.(3) The force condition of each part of postoperative atlanto-axis was investigated by observing the stress nephogram,and the stability of postoperative model was analyzed by comparing rigidity and strength of two.Results:The finite element model of typeâ…¡odontoid process fracture fixed with anterior odontoid screw was established,including 13661 shell elements,22315 solid elements and 196 spring elements.The maximum stress concentration area of postoperative model was the part of the screw which connected the fracture odontoid.Applied the same load,displacement cloud pictures of two models had no significant differences,it proved that stability of postoperative atlanto-axial complex was good.With load increasing,the deformation of the screw occurred without displacement of fracture odontoid.Rigidity and strength of postoperative odontoid was one third to half times as much as normal one.Conclusion:This three-dimensional atlanto-axisal finite element model has similar appearance with reality and can be used for biomechanical study.Odontoid process fracture can be fixed firmly by anterior odontoid screw and the active degree of cervical vertebrate is extremely retained.