Abstract:Objective To analyze and compare the effects of transverse ligament injury on the stability and stress distribution of atlantoaxial complex fractures using 3D finite element method. Methods A male volunteer with a normal cervical spine was selected. The cranio-cervical region (C0-C3) was scanned using a 64-slice spiral CT scanner. Software such as Simpleware 3.0, Geomagic 12.0, and Hypermesh 12.0 were used to create a three-dimensional finite element model (FEM/Intact) of the C0-C3 segment. On the validated model, the anterior and posterior arches of C1 and the base of the odontoid process were fractured to create a composite fracture model (FEM/Fracture) simulating Jefferson/Type Ⅱ odontoid fracture. Two additional models were created: one with a ruptured transverse ligament of the atlas (FEM/RTL) and another with an intact transverse ligament (FEM/TL). The models were subjected to loading conditions of flexion, extension, lateral bending, and rotation, and the Von Mises stress distribution and vertebral segment motion were analyzed for each model under different loading conditions. Results The three-dimensional nonlinear finite element model of the atlantoaxial complex created in this study had a realistic appearance and good geometric similarity. The motion of each vertebral segment in the model was consistent with the results of Panjabi's in vitro experimental analysis. The composite fracture model of Jefferson/Type Ⅱ odontoid fracture with or without transverse ligament injury also had a realistic appearance and good geometric similarity. After combining the transverse ligament injury with the Jefferson/Type Ⅱ odontoid fracture, the instability of the upper cervical spine primarily concentrated at the atlantoaxial joint, with varying degrees of increased motion in flexion, extension, lateral bending, and axial rotation compared to the normal group.Conclusion Transverse ligament injury significantly affects the stability and stress distribution of atlantoaxial complex fractures. The finite element models established in this study can be used for biomechanical analysis of Jefferson/Type Ⅱ odontoid fracture combined with transverse ligament injury, and provide strong theoretical support for the selection of fixation methods in atlantoaxial complex fractures.