Radiographic analysis of C2 pedicle screw placement guided by the transverse foramen in patients with a high-riding vertebral artery

Background

C2 pedicle screws (C2 PS) offer superior fixation but pose vertebral artery injury risks, accentuated by a high-riding vertebral artery (HRVA) and narrow C2 pedicle, prompting alternative approaches for safety. This study evaluated the safety and feasibility of an alternative technique.

Methods

This retrospective analysis focused on C2 PS placement for atlantoaxial instability and was conducted at Taichung Veterans General Hospital from April 2020 to December 2022. The alternative technique involved a high-speed burr that determined the C2 PS entry point. Tactile palpation-guided screw placement was confirmed using intraoperative fluoroscopy. Preoperative and postoperative computed tomography scans were used to assess pedicle dimensions, screw angles, and breaches. A HRVA and narrow pedicle classification were established. Postoperative scans were used to identify breaches by using a grading system. Radiographic data were assessed independently.

Results

A HRVA was present in 18 out of 39 patients in whom C2 PS placement was performed. Significant differences in the pedicle dimensions and screw angles were observed between the HRVA and non-HRVA groups. The overall breach rate was 15.4 %, with higher rates in the HRVA cases than in the non-HRVA cases (27.8 %). Lateral-inferior breaches were predominant, and all breaches were on the right side. No symptomatic complications were noted.

Conclusions

This alternative technique appears safe and feasible, especially in patients with a HRVA. Shorter pedicle screws may be considered for HRVAs with narrow pedicles. An alternative technique for C2 PS placement appears to be beneficial for reducing breach rates, especially in challenging cases.