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

For C2 pedicle screw placement/instrumentation, it is critical to adequately measure the axial and oblique C2 pedicle diameters utilizing the intraoperative O-arm.

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").

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.

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.