Fig. 3

Large disc herniation at the L4–5 level. Intraoperative imaging during unilateral biportal endoscopic (UBE) discectomy of a 28-year-old man presenting with severe back and right leg radiating pain. The herniated disc triangle compressing the thecal sac and traversing nerve root star (a), thecal sac, traversing nerve root star, and the posterior ligament circle were freely movable after disc fragment removal (b). Magnetic resonance (MR) axial image shows paracentral disc herniation and compression in the thecal sac and L5 traversing nerve root (white arrow) (c). Sagittal MR image shows down migrated disc compressing the thecal sac (white arrow) (d). After UBE discectomy, postoperative axial MR image shows decompressed thecal sac and traversing L5 nerve root (white arrow) (e). Postoperative sagittal MR imaging shows removed herniated disc (white arrow) and minimally invasive instrumental pathway for discectomy (black arrow) (f)