Fig. 4

Intraoperative X-ray and endoscopic images of the surgery. a Posteroanterior X-ray image of the puncture procedure. b Lateral X-ray image of the puncture procedure. c Drill the trephine until the distal end reaches the medial border of the pedicle on posteroanterior view. d, e Press down the trephine further and keep drilling until the distal end exceeds the midpoint between medial border of the pedicle and the spinous process on posteroanterior (d) and lateral (e) view. f Endoscopic view after removing the herniation