Fig. 2

Preoperative plan for TARP position and optimal trajectories. a After virtual reduction of C1 and C2, the TARP was moved to a proper position to simulate C1/2 fixation, in which the entrance point of the vertebral body was determined. b The optimal trajectory was determined by the entrance point of the vertebral body and the centroid at the midpoint of the pedicle. c Four additional holes were set. D1 was a 2.5-mm-diameter hole for a temporary reduction screw (TRS) that was as high as the inferior border of the TARP. D2 was a 2.0-mm-diameter hole for a setscrew that was 5 mm higher. D3 and D4 were 2.0-mm-diameter holes for the entry points of the trajectory for C2TOPI, which were located at the center of the pedicle screw holes of the TARP