The effect of axis pedicle and intra-axial vertebral artery on C 2 pedicle screw placement

Abstract

To investigate the influence of axis pedicle and intra-axial vertebral artery (IAVA) alignment on C 2 pedicle screw placement by measuring the data of head and neck CT angiography. The axis pedicle diameter (D), isthmus height (H), isthmus thickness (T), and IAVA alignment types were measured in 116 patients (232 sides) who underwent head and neck CT angiography examinations between January 2020 and June 2020. Defined the IAVA offset direction by referencing the vertical line through the center of C 3 transverse foramen on the coronal scan, it was divided into lateral (L), neutral (N), and medial (M). Defined the IAVA high-riding degree by referencing the horizontal line through the outlet of the C 2 transverse foramen, it was divided into below (B), within (W), and above (A). The rate of pedicle stenosis, high-riding vertebral artery, and different IAVA types were calculated, and their relationships were analysed. Simulative C 2 pedicle screws were implanted by Mimics 19.0 software, and the interrelation among the rates of pedicle stenosis, high-riding vertebral artery, IAVA types, and vertebral artery injury were analyzed. The rate of C 2 pedicle stenosis was 33.6% (78/232), and the rate of high-riding vertebral artery was 35.3% (82/232). According to the offset direction and the degree of riding, IAVA was divided into 9 types, among which the N-W type (29.3%) was the most, followed by the L-W type (19.0%) and the L-B type (12.9%), accounting for 60.9%. The vertebral artery injury rate of simulative implanted C 2 pedicle screws was 35.3% (82/232). The vertebral artery injury rate in patients with pedicle stenosis and high-riding vertebral artery was significantly higher than that who were not ( P<0.001). The rate of pedicle stenosis, high-riding vertebral artery, and vertebral artery injury were significantly different among IAVA types ( P<0.001), and M-A type was the most common. Vertebral artery injury is more common in pedicle stenosis and/or high-riding vertebral artery and/or IAVA M-A type. Preoperative head and neck CT angiography examination has clinical guiding significance.