Percutaneous Endoscopic Interlaminar Lumbar Discectomy for a Far Inferiorly Migrated Massive Lumbosacral Disc Fragment (8.5 cm) Causing Near-Complete Canal Occupancy: A Case Report with 3-Month Follow-up and Technical Review

High-grade inferiorly migrated disc herniations at the lumbosacral junction are technically challenging for endoscopic surgery because of anatomical constraints, transitional vertebrae, and the steep caudal trajectory needed to reach far-migrated fragments while protecting neural elements. These challenges are amplified when the fragment is unusually large and occupies most of the spinal canal. A 40-year-old male presented with 12 months of low back pain radiating to the left leg, numbness, weakness, and perineal sensory symptoms without bowel or bladder dysfunction. Magnetic resonance imaging (MRI) demonstrated a far inferiorly migrated massive extruded fragment at the lumbosacral junction in the setting of sacralization of L5. The fragment extended beyond the inferior boundary of the commonly used far-down migration zone and caused near-complete canal occupancy with severe thecal sac compression on axial imaging. Percutaneous endoscopic interlaminar lumbar discectomy was performed under epidural analgesia with conscious sedation through an approximately 8 mm incision using an interlaminar endoscope and 8 mm working cannula. Selective flavectomy and limited bony undercutting were used to optimize the steep caudal trajectory. The extracted specimen measured 8.5 cm × 2.0 cm × 1.0 cm ex vivo on ruler-based specimen photography; this value reflects the greatest dimension of the photographed extracted specimen rather than an aggregate summed length. Immediate postoperative MRI confirmed complete decompression. Pain improved from Visual Analog Scale (VAS) 8-2 and brief pain inventory (BPI) 9-2 on postoperative day 1, motor strength improved from 4/5 to 5/5, and there were no perioperative complications. At 3-month follow-up (telephonic at 6 weeks and clinical review at 3 months), VAS was 1, BPI was 1, Oswestry disability index improved from 78 to 12, the patient had returned to normal daily activities and desk work, and there was no clinical evidence of recurrence. This case supports the technical feasibility of standard interlaminar endoscopic systems for selected exceptionally large, far-migrated lumbosacral disc fragments when careful neural protection and limited corridor optimization are used by experienced surgeons. The findings should be interpreted cautiously because this is a single case with short-term follow-up.