A novel method to judge the safe position of C2 lamina screw with double holes

Use of the C2LS assisted by double holes was able to determine the safe position of the screw in operation. When D1 is greater than D2, the screw position can be considered relatively safe, with the intraoperative visual manifestation of a deep screw in hole 1 and a shallow screw in hole 2. If D1 is close to D2, it is necessary to ensure that the screws in both holes 1 and 2 are shallow, then the screw position is safe. If the screw in hole 1 is observed to be shallower than in hole 2 during surgery, regardless of the entry point position, there is a significant risk of ventral cortical perforation. Especially when the entry point is more anterior, even when inserting the screw parallel to the lamina, caution must be taken against the risk of ventral cortical perforation.