Fig. 1

a Fluoroscopic pedicle axis view. The C-arm was rotated in the anterior-posterior (AP)/lateral direction (arrow) to ensure that the pedicle cortex wall could be clearly visualized. b Guide wires (1.5 mm) were placed in the pilot holes (arrows). c A cannulated tapping device. The arrow: the guide wire can be visualized in the cannulated tap to ensure that the wire does not penetrate the anterior wall