TELD — Transforaminal Endoscopic Lumbar Discectomy

TELD reaches a herniated lumbar disc from the side of the body, through a corridor only a few millimetres wide, entering the spine through a natural anatomical window rather than cutting through the muscles of the back. The disc fragment is removed under continuous saline irrigation and magnified endoscopic vision, and the nerve is freed — all without the muscle stripping, bone removal or facet resection that an open approach requires. It can be performed under local anaesthetic and sedation, so the nerve can be monitored by talking to the patient during the most delicate steps.

I set out the history because it explains why the technique is what it is today. The transforaminal route began with Kambin's percutaneous work in the 1970s and his description of the safe working zone that now bears his name — Kambin's triangle, bounded by the exiting and travelling nerves. Yeung then developed a working endoscope with continuous irrigation and popularised the "outside-in" approach; Hoogland advanced it with reamers that open the foramen to reach both soft disc and bony pathology; and Sang-Ho Lee refined the "half-in, half-out" technique that made it possible to address migrated, foraminal and extraforaminal fragments. I stand on that lineage, and part of subspecialising in this field is understanding not just how to perform the technique but why each refinement exists — because it tells you which variation to reach for in a given case.

Whatever the specific herniation, the same principles govern the operation. The entry point on the skin is planned precisely from the MRI, because it determines whether the scope can reach the fragment cleanly — further out for lower levels, adjusted for a patient's build and the height of the pelvis. Access is made through Kambin's triangle, confirmed on x-ray, and the disc is often stained with a dye so the fragment stands out. Where the bony doorway needs enlarging, a controlled foraminoplasty with a small burr opens the way while the exiting nerve is identified and protected. The fragment is then removed under direct vision, and decompression is confirmed when the nerve returns to its natural position and the dural sac pulses freely. The unifying rule is simple: identify and protect the exiting nerve before any disc is touched.

The real craft of TELD lies in selecting the right variation for the problem in front of you, and in matching the difficulty of the case to the level of experience. A contained lateral-recess disc in the upper lumbar spine is a more approachable case; a migrated fragment, a foraminal or extraforaminal herniation, or a case with a high pelvis and a collapsed disc space is considerably more demanding and calls for adapted manoeuvres. This is exactly the judgement I have built my practice around, and it is why the transforaminal technique is best thought of not as a single operation but as a family of related approaches, each suited to a particular pattern of disc herniation.

The evidence base is strong. A landmark randomised trial by Ruetten and colleagues, and a large multicentre randomised trial in the BMJ, both found full-endoscopic discectomy at least as effective as open microdiscectomy for relieving sciatica, with less tissue trauma and quicker recovery; multiple systematic reviews and meta-analyses agree. The literature also documents the specific considerations of the technique — most notably a transient dysaesthesia, a temporary irritability of the nerve, that can follow work near the dorsal root ganglion — which is precisely why careful technique, case selection and training matter so much.

Because the muscles and bone of the back are almost entirely spared, recovery is usually quick — most people walk soon afterwards, go home the same day or the next, and notice the leg pain settling early. Some temporary tingling or nerve sensitivity in the leg can occur in the first weeks and usually settles; numbness and long-standing weakness may take longer and do not always resolve fully. Heavy lifting and repeated bending are limited for a period while the disc settles, and the spine is followed up over the longer term.

• —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 for sciatica: multicentre RCT. (PMID 35190388)
• —Gadjradj PS, et al. Full-endoscopic transforaminal versus open microdiscectomy: systematic review and meta-analysis. (PMID 35867477)
• —Ruan W, et al. Percutaneous transforaminal endoscopic versus open lumbar discectomy: meta-analysis. (PMID 36439526 / PMC9691761)
• —Ahn Y. Transforaminal endoscopic surgery for lumbar disc herniation: systematic review. (PMID 19756781)
• —Kim JY, Choi SY, Kim HS, Jang IT. Full endoscopic transforaminal approach for disc migrated to four corners. Acta Neurochir 2021. (PMID 33598721)
• —Lewandrowski KU, et al. Dysaesthesia after transforaminal endoscopic decompression: risk-factor analysis. (PMID 32683194)
• —Transforaminal endoscopic lumbar discectomy: learning curve of a single surgeon. (PMID 37435320 / PMC10331491)