Morphometric characteristics of the C2 vertebra and high-riding vertebral artery at the craniovertebral junction in rheumatoid arthritis.

Introduction: To compare axial and sagittal C2 pedicle-related morphometric parameters between patients with rheumatoid arthritis (RA) and healthy controls, with specific emphasis on the prevalence of a high-riding vertebral artery (HRVA). Materials and Methods: This retrospective cross-sectional study analyzed cervical computed tomography (CT) scans of 30 patients with RA and 194 healthy individuals. Bilateral axial and sagittal C2 pedicle-related parameters, including pedicle width, length, angulation, isthmus height, and internal height, were measured. HRVA was defined as an isthmus height of ≤ 5 mm and/or an internal height of ≤ 2 mm. Morphometric parameters and HRVA prevalence were compared between the groups. Results: No significant differences were observed between the groups regarding pedicle angles, lengths, or widths. However, patients with RA demonstrated significantly reduced right-sided isthmus height and internal height compared with controls. In addition, the prevalence of HRVA was significantly higher in the RA group on both sides. Conclusion: RA is associated with distinct C2 morphometric alterations, particularly reduced right-sided isthmus and internal heights and a higher prevalence of HRVA. These findings have important implications for posterior cervical fixation, underscoring the need for meticulous preoperative CT-based morphometric assessment to optimize surgical planning and enhance neurovascular safety.