Objective:Toestablish the three dimensional(3D)finite elementmodel(FEM)ofatlantoaxialvertebra(AAV)in order to provide the biomechanical base for the stability of atlantoaxial reconstruction.Methods:After the occipitocervical specimen(C0～3)was scanned on a spiral computed tomography

the scanning data were collected

and then inputted into software Mimics 10.0 to extract the 3D model of C0～3 bone and ligament by gray scale more than-250 Hu

and then was remodeled.Subsequently

it was imported with the finite element analysis(FEA)software Patran2005 by the OUT format to produce tetrahedron grid(TG)model.Then the TG model was inputted into software Mimics10.0 again and the material parameter was distributed.So 3D FEM of AAV was completed

which included cortical bone

cancellous bone and ligament.It highly simulated the integrated structure and material property of AAV.The node and element number of this model was 9 178 and 40 356 respectively.The C3s’ inferior boarder of the model was restrained(six-freedom-degree was zero).The 3D range of motion(3DM)C1 relative to C2 was measureda

nd the stress of various sections of AAV was analysed by loading 1.5 Nm at C0 under the conditions of flexion/extension

left/right lateral bending

and left/right axial rotation by Patran2005.3DM C1 relative to C2 was measured under similar loading method in laboratory.Then data in the two groups were collected and statistically analysed.Results:The lateral facets of atlantoaxial joint and the anterior part of C2 body were the stress concentration regions and also high bone mineral density regions.3DM C1 relative to C2 on FEA(flexion/extension

5.48°/9.85°

left/right lateral bending

4.69°/4.93°

and left/right axial rotation

31.28°/30.56°)was similar to the experiment(flexion/extension

8.10°/8.49°l

eft/right lateral bending

4.79°/4.93°l

eft/right axial rotation

28.2° /29.3°).Conclusion:The 3D FEM of AAV

constructed by combined usage of Mimics and Patran2005i

s valid and accurate

and can mimic the biomechanical studies of AAV.