Technical Note: Intraoperative Injection of Indigo Carmine for Differentiating Neural Tissue During Unilateral Biportal Endoscopic Surgery

Unilateral biportal endoscopy offers substantial advantages in spinal surgery but continues to carry a risk of neural injury due to the difficulty of distinguishing neural structures from surrounding tissues. This video article demonstrates the intraoperative use of indigo carmine to mitigate this risk. Indigo carmine selectively stains fibrous tissue and disc material while sparing nerve roots, owing to its impermeability to intact cellular membranes. This property enhances visual differentiation and promotes surgical safety. We present 2 cases involving 64-year-old female patients who underwent discectomy for ruptured L5–S1 discs. In both cases, intraoperative injection of indigo carmine into the working field or disc space effectively delineated neural elements from adhesive tissues and disc material. Postoperative imaging confirmed successful decompression. Indigo carmine represents a useful, surgeon-friendly, cost-effective, and time-efficient adjunct that improves visualization and helps prevent iatrogenic neural injury. Its use is particularly recommended for revision surgery, complex degenerative conditions, and for endoscopic spine surgeons in training.