The Finite Element Analysis Of Odontoid Fracture Of The Axis

Objective(1)To establish and validate the finite element model of the axis.(2)select different nodes on the odontoid, and give force/moment to the nodes, carried out the analysis and predict type of the odontoid fracture.MethodSelect an emergency case from Shengjing hospital,scan the cervical vertebrae using the Philip's 64-slice CT scan machine, and save as DICOM format. View the patient's CT images in the PACS system first, then export DICOM format of the stored data. Reconstruct the axis surface model in use of mimics software, meshing and optimizing, and import the surface model of the axis to the finite elements analysis software ansys in ansys element lis format. Set element type, real constants, and material props, then tet mesh from area, and the finite element model of axis was built. Give load to the model, containing displacement on the lower surface of the vertebrae body, on the lower surface of the spinous process and on the surface of the bilateral inferior articular process, we also give 50N pressure to the surface of the bilateral superior articular process. We use 4 type of Force/moment give to the odontoid.(1)Force/moment apply to nodes on the middle of the odontoid to verify the model.(2) Force/moment apply to nodes on the tip of the odontoid to simulate hyperextention injury of the neck and to predict the tendency ofâ…¡orâ…¢odontoid fracture type.(3) Force/moment apply to nodes on the bottom of the odontoid to simulate flexor injury of the neck and to predict the tendency of theâ…¡orâ…¢odontoid fracture type.(4) Force/moment apply to nodes on the side of the odontoid to simulate violence act on the neck when it is rotated and to predict the tendency ofâ…¡orâ…¢ odontoid fracture type.ResultsIn the first step of analysis, we see that stress is concentrated in the lower part and the bottom of the odontoid, theâ…¡type of fracture tend to occur. The maximum stress value is 135.934MPa, and reference value is 138Mpa.The model is verified. In the second,third and forth step of analysis, we see that the maximum stress value is 143.411MPa in the flexor state, and in the extensor state, the value is 137.610MPa.They both greater than the value in the neutral state(135.934MPa).In the rotation state, the maximum stress value is 148.499MPa,it is the greatest in the four state.Conclusion(1)The biomechanics behavior of the axis finite element model conform with the references, the model can be used for further analysis.(2)In the rotation state, fracture of the odontoid tend to occur. Stress concentrated in the bottom of the odontoid and result in theâ…¡type of fracture.(3)Hyperextention injury lead toâ…¢type of fracture because the stress concentrated in the lower part and bottom of the Odontoid.(4)In the flexor state, stress concentrated in the bottom of the odontoid and the bilateral superior articular process of the axis and result inâ…¢type of fracture.