Assessment of failure risks during C2 vertebra pedicle screw insertion using three-dimensional computed tomography angiography analysis: the role of high-riding vertebral artery and narrow pedicles.

BACKGROUND

Cervical fixation is a common treatment for conditions like vertebral fractures, osteosarcoma, osteomyelitis, arthritis, and congenital disorders. The study was designed to assess the occurrence of high-riding vertebral artery (HRVA), narrow C2 pedicles (NC2P) and ponticulus posticus (PP), which pose risks of injuring vertebral artery (VA) during screw placement in cervical fixation procedures.

METHODS

The study examined the prevalence of HRVA, NC2P and PP in 382 pedicle sides of the C2 vertebra using computed tomographic angiography scans. Specific measurements were taken, including the internal height (C2InH), and isthmus height (C2IsH) of C2, as well as NC2P width.

RESULTS

HRVA was identified by specific measurements: C2IsH of ≤ 5 mm and/or C2InHof ≤ 2 mm. NC2P was defined as NC2P width ≤ 4 mm. The reliability between observers and within the same observer, along with the consistency across different software, was assessed. At least one HRVA was found in 9.6% of patients and at least one NC2P in 13% of patients. Females demonstrated higher rates of HRVA and NC2Ps on the left side, with right-side figures at 10.5% and 11.7% for HRVA and NC2Ps respectively, and left side figures at 14.1% for both. Males exhibited a reserve pattern, with higher rates on the right side, marked by 10.3% HRVA and 15% NC2Ps, compared to 5.6% and 11.3% on the left. Furthermore, males showed a significantly higher occurrence of NC2Ps over HRVA on both sides. The presence of PP with NC2Ps detected in 44% of cases, and with HRVA in 16% of cases, a difference found to be statistically significant.

CONCLUSIONS

The digital models incorporating HRVA, NC2P, and PP facilitated a comprehensive analysis of the VA pattern, assessment of the virtual screw trajectory line for VA pedicles, and the designation of specific regions during the procedure, ensuring increased safety planning instrumentation.