Fig. 4

The second-step foraminoplasty and fragmentectomy in very-highly upward-migrated herniation. *, the responsible disc level, #, the upward-migrated disc fragments. (a): Schematic representation of the second-step foraminoplasty for upward-migrated herniation at L3/4, the dotted red line indicates the margin of bony resection; (b): An endoscopic trephine or round diamond burr was used during the second foraminoplasty, the endoscope was cranially inclined to explore the medial pedicle; (c), (d): After a partial pediculectomy and a caudal shift of the endoscope, the highly migrated fragments hidden in the medial pedicle were exposed and retrieved