Accuracy of Axis Drill Guides in the Cases of Atlantoaxial Instabilities Associated With High-Riding Vertebral Arteries, Narrow Pedicles, and Complex Deformities: Comparison of 3 Fixation Methods.

Objective: To contrast the accuracy of C2 navigation template-assisted versus freehand pedicle and/or pars screw fixation in high-risk cases where a high-riding vertebral artery (VA) or narrow pedicle and complex deformities were associated.

Methods: In our hospital, computed tomography (CT) data of 30 patients with pathology on C, who had risk factors for VA injury, that were complex cervical deformities, atlantoaxial instabilities with narrow C2 pedicle and/or HRVA variations were retrospectively reviewed. Using computer-aided design software and desktop printer we printed 3 sets of high cervical models per case. We divided them into 3 groups using 3 different C2 screw fixation techniques: the freehand pars screw fixation group, the freehand pedicle screw fixation group, and the navigation template-assisted pedicle screw fixation group. After 180 screw placements were finished, the parts underwent a CT scan. Then the breach rates on postoperative scans were measured.

Results: Our results showed that the accurate placement rate is not noticeably different between navigation template-assisted and freehand pedicle screws, where the high-riding vertebral artery and narrow pedicles were associated, but was better in the navigational template group with complex deformities. Pars screws were found to be superior in terms of accuracy.

Conclusions: The current study suggests that navigational template-assisted pedicle screws are risky for high-risk individuals with abnormal anatomy, such as those with a high-riding vertebral artery, a narrow pedicle, and complex abnormalities, and alternative C2 pars screws may be a reliable option for such individuals.