Axial and oblique C2 pedicle diameters and feasibility of C2 pedicle screw placement: Technical note

BACKGROUND: For C2 pedicle screw placement/instrumentation, it is critical to adequately measure the axial and oblique C2 pedicle diameters utilizing the intraoperative O-arm. METHODS: Thirty-three patients who underwent C2 pedicle screw placement (2013–2016) utilizing the O-arm with tri-planar reconstruction. As O-arm software does not allow calibrated measurements with the application's measurement tool, we directly measured axial and oblique widths of the C2 pedicles on the screen with a regular ruler (e.g., “screen width of C2 pedicle”). RESULTS: The axial width of the C2 pedicles ranged from 6 to 15 mm on the right (mean 10.44 ± 2.15 mm) to 7 to 14 mm (10.29 ± 1.72 mm) on the left. The oblique width of C2 pedicles ranged from 10 to 19 mm on the right (mean, 14.73 ± 1.85 mm) and from 12 to 19 mm on the left (mean, of 15.33 ± 1.67 mm). These measurements indicated that oblique screen widths of the C2 pedicles were 1.4 and 1.5 times higher than their axial screen widths on the right and left sides, respectively. CONCLUSIONS: The oblique screen widths of the C2 pedicles better predict the feasibility of C2 pedicle screw placement vs. their axial screen width as measured with a regular ruler.