Fig. 2.

All perforations were measured in mm. If the perforated part of the pedicle was not visible due to interferences caused by the screw, the diameter of the nonperforated side was measured, serving as reference (A and B). Assuming a similar pedicle size on the perforated side, these distances were used to define the invisible pedicle wall on the perforated side (A* and B* = A and B). Then the magnitude of the perforation was determined (C). (Red line: midline of the pedicle; dashed white line: assumed pedicle wall; dotted red line: exactly definable bony margins).