The association between unilateral high-riding vertebral artery and atlantoaxial joint morphology: a multi-slice spiral computed tomography study of 396 patients and a finite element analysis

•Unilateral high-riding vertebral artery may cause the nonuniform settlement of lateral mass.•Unilateral high-riding vertebral artery is associated with morphological changes of atlantoaxial joint.•We first propose the settlement phenomenon of C2 lateral mass and measurement method.•Expanding the understanding of effect of high-riding vertebral artery on atlantoaxial joint. A high-riding vertebral artery (HRVA) can deviate too medially, too posteriorly, or too superiorly to allow the safe insertion of screws. However, it is unknown whether the presence of a HRVA is associated with morphological changes of the atlantoaxial joint. To investigate the association between HRVA and atlantoaxial joint morphology in patients with and without HRVA. A retrospective case–control study and finite element (FE) analysis. A total of 396 patients with cervical spondylosis underwent multi-slice spiral computed tomography (MSCT) of cervical spine at our institutions from 2020 to 2022. A series of atlantoaxial joint morphological parameters, including C2 lateral mass settlement (C2 LMS), C1–2 sagittal joint inclination (C1–2 SI), C1–2 coronal joint inclination (C1–2 CI), atlanto-dental interval (ADI), lateral atlanto-dental interval (LADI), and C1–2 relative rotation angle (C1–2 RRA) were measured, and lateral atlantoaxial joints osteoarthritis (LAJs-OA) was recorded. The stress distribution on the C2 facet surface under different torques of flexion-extension, lateral bending, and axial rotation was analyzed by FE models. A 2-Nm moment was applied to all models to determine the range of motion (ROM). A total of 132 consecutive cervical spondylosis patients with unilateral HRVA were enrolled in the HRVA group, and 264 patients without HRVA matched for age and sex were enrolled in the normal (NL) group. Atlantoaxial joint morphological parameters were compared between two sides of C2 lateral mass within HRVA or NL group, and between HRVA and NL groups. A 48-year-old woman with cervical spondylosis without HRVA was selected for cervical MSCT. A three-dimensional (3D) FE intact model of the normal upper cervical spine (C0-C2) was created. We established the HRVA model by simulating atlantoaxial morphological changes of unilateral HRVA with FE method. The C2 LMS was significantly smaller on the HRVA side than that on the non-HRVA side in the HRVA group, but C1–2 SI, C1–2 CI, and LADI on HRVA side were significantly larger than those on non-HRVA side. There was no significant diff