Methods: We evaluated the trajectories of atlantoaxial transarticular and C2-pedicle screws in 3 dimensions using computerized tomography. Objective: To compare the anatomic risk for vertebral artery injury associated with C2-pedicle and atlantoaxial transarticular screws.

Background: The atlantoaxial fixation technique using C1-lateral mass screws combined with C2-pedicle screws is considered a safer technique for preventing vertebral artery injury than atlantoaxial transarticular fixation. However, few reports have compared the anatomic risk of vertebral artery injury associated with C2-pedicle screws with that of transarticular screws.

Methods: A total of 62 consecutive patients with cervical lesions were evaluated using 3-dimensional images reconstructed by a computer-assisted navigation system. We compared the maximum possible diameters of the atlantoaxial transarticular screw and C2-pedicle screw trajectories, and examined whether the maximum possible diameters were limited by the height or width of the bony structure in screw trajectories < or = 4 mm in diameter.

Results: Mean maximum possible diameters did not differ significantly between the trajectories of 124 atlantoaxial transarticular and 124 C2-pedicle screws. In screw trajectories < or = 4 mm in diameter, 57.1% of transarticular screw trajectories were limited by the height of the bony structure, and all pedicle screw trajectories were limited by the width.

Conclusions: C2-pedicle screw placement has nearly the same anatomic risk of vertebral artery injury as transarticular screw placement. Preoperative 3-dimensional evaluation may be useful for choosing the best surgical technique.