Fig. 3

The first step foraminoplasty and fragmentectomy in very-highly upward-migrated herniation. *, the responsible disc level, #, the upward-migrated disc fragments. (a): Schematic representation of the first-step foraminoplasty for upward-migrated herniation at L3/4, the dotted red line indicates the margin of bony resection; (b): Lateral intraoperative radiography, the working cannula is cranially shifted for exploring the sequestered fragment; (c): Under endoscopic view, the migrated fragments hidden behind the inflamed exiting nerve root is explored; (d): After the initial fragmentectomy, very-highly upward-migrated fragments in the “hidden zone” is beyond the reach, a second fragmentectomy is needed