ULBD — Unilateral Laminotomy for Bilateral Decompression

Over years of wear, the spinal canal can narrow from a combination of thickened ligament, enlarged facet joints and bulging discs, crowding the nerves that run through it. This produces the classic pattern of neurogenic claudication — heavy, aching, tired legs on walking or standing that ease on sitting or bending forward. A decompression relieves this by removing the thickened ligament and trimming the overgrown bone to reopen the canal. In a ULBD, all of this is done from one side only: the endoscope enters through a single small portal, and from that one side I work across beneath the bony roof of the canal to reach and free the nerves on both the near and the far side.

This is the heart of the technique, and it reflects a principle I apply throughout my endoscopic practice: achieve the full decompression while doing the least possible damage to the structures that keep the spine stable. A traditional wide laminectomy removes the whole bony roof and both sets of muscles, which relieves the nerves but can leave the segment less stable and the muscles weakened. The ULBD, by contrast, tilts the endoscope across the midline — "over the top" of the dural sac — so that the ligament and bone crowding the far-side nerve can be removed through the same single opening. The spinous process, the interspinous ligament and the entire muscle attachment on the opposite side are preserved. The result is a complete decompression of both sides through a corridor a few millimetres wide, with the stabilising anatomy left largely intact.

Working through the interlaminar window under continuous saline irrigation and magnified vision, the ligamentum flavum is released from the lamina above and carefully detached, kept for a time as a protective barrier over the nerves. The near-side lateral recess is decompressed first; then the endoscope is angled across under the midline to detach the ligament from the far side and free the opposite nerve root. Fine burrs and punches are used to trim the undersurface of the bone precisely. Decompression is confirmed when both nerve roots and the dural sac lie free and the sac is seen to pulse normally. Because so little bone and muscle is disturbed, most people recover quickly.

The skill in a ULBD lies in the "over-the-top" manoeuvre — safely tilting the working angle across the midline to reach the far side without over-retracting or injuring the dura, and judging exactly how much of the undersurface of the facet joint to remove to free the nerve while protecting the joint and the pars, so that stability is preserved. Reading each patient's anatomy from the MRI and CT, and knowing when a straightforward endoscopic ULBD is appropriate versus when instability means a fusion is needed, are judgements built through subspecialty experience. This is precisely the kind of decision-making that I have concentrated my practice and teaching on.

The evidence supports endoscopic ULBD. Meta-analyses and systematic reviews comparing full-endoscopic and biportal endoscopic ULBD with microscopic decompression find equivalent clinical improvement in pain and disability, with less blood loss, shorter hospital stays and, in several series, fewer complications. Imaging studies confirm that the canal is genuinely reopened and that the preserved midline and contralateral muscles remodel favourably. Series specifically in elderly patients and in those with a mild degenerative slip show that endoscopic ULBD gives good, durable relief. Reported dural-tear rates are low, and the tissue-preserving nature of the approach is its consistent advantage across the literature — which is exactly why I favour it for the right patient.

Because the muscles and midline are spared, recovery from an endoscopic ULBD is usually quick and comfortable. Many people go home the same day or the next, walking, with only a small dressing, and notice the leg heaviness and claudication easing early. Numbness and long-standing weakness can 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.

• —Uniportal endoscopic versus microscopic unilateral laminotomy for bilateral decompression: meta-analysis. (PMID 41817060)
• —Endoscopic ULBD compared with other decompression approaches for lumbar stenosis: systematic review. (PMID 36527216)
• —Microscopic versus biportal endoscopic ULBD for lumbar canal stenosis: meta-analysis. (PMID 36211279 / PMC9537863)
• —Outcome analysis of lumbar endoscopic ULBD in degenerative central canal stenosis. (PMID 32871276)
• —Lumbar endoscopic ULBD with and without degenerative spondylolisthesis: comparable outcomes. (PMID 33722714)
• —Full-endoscopic versus microscopic ULBD in elderly lumbar stenosis (12-month follow-up). (PMC7295456)
• —Canal remodeling after uniportal endoscopic ULBD: 1-year MRI follow-up. (PMC9030158)
• —Thomé C, et al. Unilateral laminotomy versus laminectomy for lumbar stenosis (RCT). (PMID 16370302)