TELD — Migrated Disc Herniation

Usually a herniated fragment stays close to the disc it came from. Sometimes, though, a fragment breaks free and migrates — travelling upward or downward within the canal, coming to rest behind the vertebra above or below the disc space. Migration matters because the fragment is now some distance from the natural point of surgical access, often tucked into a corner where it is trapping a nerve. High-grade migration, where the fragment has travelled a long way, is one of the situations that most tests a surgeon's approach, whatever the technique.

This is where the transforaminal approach becomes genuinely sophisticated, and it is the part I find most rewarding. The direction the fragment has moved dictates how the corridor is planned and how the bone is prepared. For a fragment that has migrated downward, a little of the top of the pedicle below is carefully removed — a technique described as a suprapedicular circumferential opening — so the working sleeve can angle down to reach it. For a fragment that has migrated upward, the sleeve is directed cranially with great care, because the exiting nerve sits directly in that path and must be identified and protected first. In each case a controlled foraminoplasty with a small burr opens just enough room to steer the endoscope to the fragment, retrieve it under direct vision, and confirm that the nerve has returned to its natural position. Staining the disc with a dye beforehand helps the migrated fragment stand out clearly once the canal is entered.

The most demanding version of this problem is a broad herniation that has migrated in several directions at once — up and down, and to both sides — what the endoscopic literature calls migration to "all four corners." It is a pattern I learned to manage from my mentors in this field, whose published work describes reaching every corner through one small transforaminal portal. The keys are keeping the working cannula freely mobile within Kambin's triangle so it can be angled toward each fragment in turn, using the "mobile outside-in" technique, and performing a generous annular resection to open a path across to the opposite side so that a contralateral fragment can be retrieved without a second incision and without retracting the nerve. Being able to clear multiple fragments in multiple directions through a single few-millimetre corridor, while preserving the facet joint entirely, is one of the things that most distinguishes a mature transforaminal practice — and it is a technique I have both trained in and written about.

I set this out in detail because migrated discs are, frankly, not beginner cases, and I say so plainly to patients. The safe zone is smaller, the fragment is further from the point of entry, and the manoeuvres to reach it — angling under a pedicle, working cranially past the exiting nerve — demand precise control and a clear three-dimensional picture of where everything lies. This is exactly the territory I have concentrated my practice and my teaching on, and it is the kind of case where matching the right variation of the technique to the specific pattern of migration makes the difference between a clean result and a struggle. When the approach is chosen and executed well, even a far-travelled fragment can be removed through a corridor a few millimetres wide.

The endoscopic management of migrated discs is well described in the literature. The foraminoplastic technique for highly migrated fragments was established in a landmark series by Choi and colleagues, and classification systems relating the direction and grade of migration to the surgical approach have followed. Subsequent cohorts, including long-term follow-up beyond five years, report that full-endoscopic surgery achieves good outcomes even for high-grade migration, using adapted manoeuvres such as suprapedicular access and, for the most extreme cases, extended foraminoplasty. Across the broader evidence, full-endoscopic discectomy matches open microdiscectomy for relief of sciatica while sparing the tissues — the migrated disc simply asks more of the surgeon in reaching the target. The recognised consideration of temporary nerve irritability after work near the ganglion applies here too, and underlines the importance of careful technique.

When a migrated fragment is successfully retrieved, relief of the leg pain is often early and gratifying, and because the approach spares the muscles and bone of the back, recovery is usually quick — home the same day or the next, walking, with a small dressing. Some temporary tingling or nerve sensitivity can occur in the early weeks and generally settles. Numbness and long-standing weakness may take longer to recover and do not always resolve fully. It is honest to say that migrated cases are more technically demanding, and the approach is planned individually around the pattern of migration. The spine is followed up over the longer term.

• —Kim JY, Choi SY, Kim HS, Jang IT. Full endoscopic transforaminal approach for lumbar disc herniation migrated bilaterally to four corners. Acta Neurochir (Wien) 2021;163(4):1199-1203. (PMID 33598721)
• —Choi G, et al. Percutaneous endoscopic approach for highly migrated intracanal disc herniations by foraminoplastic technique. (PMID 18594449)
• —Lee S, et al. Percutaneous endoscopic lumbar discectomy for migrated disc herniation: classification and surgical approach. (PMID 16972067 / PMC2200706)
• —Kim CH, et al. Percutaneous endoscopic interlaminar discectomy for highly migrated disc herniation. (PMID 23073149)
• —Transforaminal endoscopic suprapedicular approach for high-grade inferiorly migrated disc herniation. (PMID 19274114)
• —Full-endoscopic surgery for high-grade migrated lumbar disc herniation: 5-year outcomes. (PMID 33422040)
• —Ruetten S, et al. Full-endoscopic interlaminar and transforaminal versus microsurgical lumbar discectomy (RCT). (PMID 18427312)
• —Gadjradj PS, et al. Full-endoscopic transforaminal versus open microdiscectomy: systematic review and meta-analysis. (PMID 35867477)
• —Lewandrowski KU, et al. Dysaesthesia after transforaminal endoscopic decompression: risk-factor analysis. (PMID 32683194)