ICLEF — Interlaminar Contralateral Lumbar Endoscopic Foraminotomy

Foraminal and extraforaminal stenosis — narrowing of the nerve's exit tunnel and the region just beyond it — can be genuinely awkward to reach. From the side, a transforaminal approach must sometimes contend with a high pelvis (at L4/5 and L5/S1) or must work close to the exiting nerve's ganglion, a relay station that is easily irritated. Approaching the foramen directly can therefore risk a temporary but unpleasant nerve sensitivity. The contralateral approach was developed precisely to get around these limitations — to reach the foramen from an angle that avoids both the pelvis and the need to pull on the nerve.

This is the elegant part, and it draws on the same over-the-top principle as a central decompression. The endoscope enters through the interlaminar window on the opposite side to the trapped nerve, and is angled across underneath the midline — over the top of the dural sac — to arrive at the far-side foramen from within the canal. Because it comes from this contralateral angle, it reaches the front of the foramen and the extraforaminal zone without having to retract the exiting nerve or its ganglion out of the way. A smaller endoscope, used in a "channel-in-channel" fashion, allows the compressive structures — an overgrown facet, a bone spur, thickened ligament or a foraminal disc — to be removed while the exiting nerve is protected. And because the approach is interlaminar, it can be combined in the same sitting with a central and lateral-recess decompression when stenosis is present at several points. Decompression is confirmed when both the travelling and exiting nerves lie free and pulse normally.

I emphasise this because it is the technique's signature advantage, and it is well supported by evidence. The dorsal root ganglion is exquisitely sensitive, and pulling on it — as some direct approaches to the foramen must — is a recognised cause of postoperative dysaesthesia, that temporary burning or irritable sensation in the leg. By reaching the foramen from the contralateral side and from within the canal, this approach largely avoids disturbing the ganglion at all. Studies comparing it directly with the transforaminal route for foraminal pathology have shown lower rates of this nerve irritation, which is a meaningful advantage for patients. This is exactly the kind of nuanced, evidence-led technical choice that subspecialty practice in endoscopic surgery is about.

This is an advanced technique and I say so plainly. It demands a confident command of the over-the-top manoeuvre, precise control of a fine burr near the nerve, careful avoidance of thinning the pars and creating instability, and reliable identification of the exiting nerve at the tip of the facet before any compression is addressed. It should be avoided where the spine is unstable, and thorough planning from CT and MRI is essential. These are the judgements I have concentrated my practice and my writing on, and they are what make an approach like this safe and effective in the right hands and the right case.

The evidence for the contralateral approach is growing and favourable. Comparative studies show that reaching foraminal pathology contralaterally, from within the canal, avoids retraction of the dorsal root ganglion and is associated with lower rates of postoperative dysaesthesia than the transforaminal route, while achieving good decompression and clinical improvement; reported rates of significant postoperative nerve irritation are low. A systematic review of the technique has drawn together its outcomes for foraminal stenosis, and series describe its particular value for combined lateral-recess, foraminal and extraforaminal stenosis at difficult levels such as L5/S1. This body of work is exactly what I draw on in selecting it for the right patient.

Because the approach spares the muscles and much of the bone and avoids pulling on the nerve, recovery is usually quick and the risk of that irritable nerve sensitivity is reduced compared with some alternatives. Many people go home the same day or the next, walking, with early relief of the leg pain. Numbness and long-standing weakness may take longer to recover and do not always resolve fully. Activity is built back up over the following weeks, and the spine is followed up over the longer term.

• —Kim HS, Kim JY, Wu PH, Jang IT. Effect of dorsal root ganglion retraction: interlaminar contralateral endoscopic foraminotomy versus transforaminal endoscopic foraminotomy. World Neurosurg 2021. (PMID 33444831)
• —Kim HS, Wu PH, Jie Chin BZ, Jang IT. Uniportal interlaminar contralateral endoscopic lumbar foraminotomy for foraminal stenosis: systematic review. World Neurosurg 2022;168:392-397.
• —Early outcomes of endoscopic contralateral foraminal and lateral recess decompression via an interlaminar approach. (PMID 28919229)
• —Uniportal endoscopic interlaminar contralateral approach for L5-S1 lateral recess, foraminal and extraforaminal stenosis: outcomes. (PMC8037803)
• —Percutaneous endoscopic contralateral lumbar foraminal decompression via an interlaminar approach: operative technique. (PMID 31232437)
• —Ruetten S, et al. Full-endoscopic versus microsurgical decompression for lateral recess stenosis (RCT). (PMID 19929343)