Endoscopic Facet Cyst Excision

The facet joints are the small paired joints at the back of the spine that guide its movement. As a facet joint wears and becomes arthritic, it can produce excess fluid, and that fluid can collect in a small sac — a cyst — that pushes into the spinal canal or the lateral recess where the nerves run. When the cyst presses on a nerve root, it causes leg pain, pins and needles or numbness, much like a disc herniation or lateral recess stenosis; when larger, it can contribute to canal narrowing. Facet cysts are often associated with a degree of instability or a small slip at that level, because it is the abnormal movement of the worn joint that drives the cyst to form — an important point when planning treatment.

Where a symptomatic facet cyst has not settled with non-operative measures such as injections, the operation removes it — excising the cyst and freeing the nerve. Done endoscopically, the endoscope is passed through the interlaminar window to the level of the cyst, under continuous irrigation and magnified vision. The cyst, which sits between the facet joint and the nerve, is carefully separated from the nerve and the dura and removed, and the nerve is confirmed to be decompressed and free. Because the endoscopic approach is a targeted keyhole, only the small amount of bone and joint needed to reach and remove the cyst is disturbed, which helps preserve the stability of the segment.

This is the central decision in facet cyst surgery, and I make it individually. Because a facet cyst usually reflects a worn, sometimes slightly unstable joint, there is a recognised chance that a cyst can recur, or that the underlying instability can cause ongoing symptoms, if the cyst is simply removed. For a stable level, endoscopic excision alone gives excellent relief of the nerve with minimal disturbance and spares the patient a fusion. Where there is a genuine, mobile slip at the level, adding a fusion removes the abnormal movement that drove the cyst in the first place and lowers the chance of recurrence. Weighing the person's stability, symptoms and imaging to make that call is exactly the kind of judgement that careful practice requires, and I discuss it openly.

The skill in endoscopic cyst excision lies in separating the cyst cleanly from the nerve and the dura — to which it can be adherent — through a small window, without tearing the dural lining, and in removing enough of the cyst and the offending part of the joint to free the nerve while preserving stability. Recognising when a level's instability means a fusion should be added, rather than a simple excision, is equally important. These are the anatomy-led, individualised decisions that subspecialty endoscopic practice is built on.

The evidence supports minimally invasive and endoscopic excision of facet and synovial cysts as effective and safe. Systematic reviews of minimally invasive cyst excision report good relief of symptoms with low complication rates, and endoscopic series — including uniportal procedures under local anaesthesia and biportal contralateral approaches — describe successful cyst removal with the tissue-sparing benefits of a keyhole and, in most cases, no need for a fusion. The literature also documents the recurrence question honestly: recurrence after decompression-only is low but not zero and is higher where there is instability, whereas adding fusion essentially removes recurrence at the cost of a bigger operation. This balanced picture is exactly how I counsel patients.

Because the operation is a targeted keyhole that spares the muscles and most of the joint, recovery is usually quick — many people go home the same day or the next, walking, with early relief of the leg pain as the nerve is freed. Some temporary nerve sensitivity can occur early and usually settles; numbness may take longer to recover. Where a fusion has been added for instability, recovery follows that of a fusion. The spine is followed up over the longer term.

• —Outcomes and complications following minimally invasive excision of synovial cysts of the lumbar spine: systematic review and meta-analysis. (PMID 33984755)
• —Decompression with or without fusion for lumbar synovial cysts: systematic review and meta-analysis. (PMC10095101)
• —Variability of lumbar facet joint synovial cyst recurrence after decompression-only versus decompression/fusion. (PMID 31453836)
• —Contralateral sublaminar biportal endoscopic removal of lumbar juxtafacet cysts: technical report. (PMID 30458327)
• —Percutaneous uniportal full-endoscopic surgery for symptomatic lumbar facet joint cysts under local anaesthesia. (PMC10748478)
• —Clinical outcomes with endoscopic resection of lumbar extradural cysts. (PMC7063300)