TELD — Foraminal Disc Herniation

Between each pair of vertebrae, the nerve leaves the spinal canal through a bony doorway called the foramen. A foraminal disc herniation is a fragment of disc that bulges into that doorway and presses on the nerve as it exits — the exiting nerve root. Because that nerve is already in a tight space, even a modest fragment can cause severe, sharply localised leg pain, and these herniations are sometimes missed on a quick look at a scan because they sit off to the side rather than in the centre of the canal. When the pain does not settle with time and non-operative care, surgery to remove the fragment and free the nerve is offered.

This is where the transforaminal approach shows its elegance, and it is the reason I favour it here. Traditional open surgery reaches the disc from the back, and to get at a foraminal fragment it often has to remove part of the facet joint to see around the nerve — which can, in turn, risk destabilising the segment. The transforaminal endoscopic route instead travels from the side of the body, through a corridor a few millimetres wide, and arrives at the disc through a natural anatomical window described by the surgeon Kambin — Kambin's triangle — bounded by the exiting and travelling nerves. It brings me to the front of the foramen, exactly where the fragment sits, without having to sacrifice the facet joint or pull the nerve out of the way. The whole operation is carried out under continuous saline irrigation and magnified endoscopic vision. For a foraminal disc, it is a direct line to the target with minimal collateral damage.

The operation is planned carefully from the MRI, because the entry point on the skin — typically some distance out from the midline, and further out at lower levels — determines whether the scope can reach the fragment cleanly. Under x-ray guidance, a fine needle is passed to Kambin's triangle, the position confirmed, and the disc is often stained with a dye so the herniated fragment shows up clearly. A working sleeve and the endoscope are then docked onto the foramen. Where the bony doorway needs enlarging to reach the fragment safely, a small burr is used to trim the front edge of the facet joint — a controlled foraminoplasty — always keeping the exiting nerve identified and protected. The fragment is then removed under direct vision, and the decompression is confirmed when the nerve returns to its normal position and the dural sac is seen to pulse freely. Much of this can be done under local anaesthetic and sedation, so the nerve can be monitored by talking to the patient during the most delicate steps.

I go into this detail deliberately, because a foraminal disc is not a beginner's endoscopic case. The exiting nerve is right at the working zone, and safe surgery depends on identifying and protecting it before any disc is touched, on judging exactly how much of the facet edge to trim without weakening the segment, and on controlling bleeding within the foramen. These are matters of training, mentorship and experience rather than equipment, and they are precisely the judgements I have spent my career refining and teaching. The reward, when the approach is right for the pathology and executed well, is complete relief of the nerve with very little disturbance to everything around it.

The evidence base for transforaminal endoscopic discectomy is strong. A landmark randomised trial by Ruetten and colleagues, and a large multicentre randomised trial published 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 confirm this. For foraminal and far-lateral herniations specifically, series show high rates of good and excellent outcomes with the transforaminal route, which reaches these lateral fragments without the facet resection an open approach would require. 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 exactly why careful technique and case selection matter.

Because the muscles and bone of the back are almost entirely spared, recovery is usually quick. Most people are up and walking soon afterwards, go home the same day or the next with a small dressing, 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 to recover 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)
• —Jang JS, et al. Transforaminal percutaneous endoscopic discectomy for foraminal and extraforaminal herniation. (PMID 16826005)
• —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)