C2 pedicle screw insertion assisted by mobilization of the vertebral artery in cases with high-riding vertebral artery.

Objective: To describe the feasibility, safety and efficacy of mobilization of the vertebral artery for C2 pedicle screws in cases with the high-riding vertebral artery (HRVA).
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Methods: During the period January 2020 to September 2022, fifteen patients underwent posterior occipitocervical fixation in our department. All patients had unilateral HRVA on at least one side that prohibited the insertion of C2 pedicle screws. There were 2 males and 13 females aged 47 ± 11.9 years (range: 17-64 years). After the correction of the vertical dislocation during the operation, the C2 pedicle screw insertion and occipitocervical fixation and fusion were performed using the vertebral artery mobilization technique. A routine three-dimensional reconstructed CT examination was executed to confirm the trajectory of C2 pedicle screws post-operation, and a CT angiography examination was performed when necessary. Neurological function was assessed using the Japanese Orthopedic Association (JOA) scale. The preoperative and postoperative JOA score and the main radiological measurements, including anterior atlantodental interval (ADI), the distance of odontoid tip above Chamberlain line, and clivus-canal angle (CCA), were collected and compared by paired -test.

Results: All 15 patients had atlas assimilation, among which 12 patients had C2-C3 fusion (Klippel-Feil syndrome). Mobilization of the HRVA was successfully completed, and C2 pedicle screws were then fulfilled after the vertebral artery was protected. There was no injury to the vertebral artery during the operation. Meanwhile, no severe surgical complications such as cerebral infarction or aggravated neurological dysfunction occurred during the perioperative period. Satisfactory C2 pedicle screw placement and reduction were reached in all 15 patients. All the patients achieved bone fusion 6 months after surgery. No looseness and shift of internal fixation or reduction loss was observed during the follow-up period. Compared to the preoperative, the postoperative JOA score and the main radiological measurements were remarkably improved and statistically significant.

Conclusions: C2 pedicle screw insertion assisted by mobilization of the vertebral artery is safe and considerably effective, providing a choice for internal fixation in cases with high-riding vertebral arteries.