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Legacy Spinal Technologies
Interspinous Devices
An honest overview of interspinous "spacer" implants (such as X-STOP and Coflex) used for lumbar stenosis — and why independent evidence points to high reoperation rates and limited benefit. I do not implant these devices; this page explains the concept and the evidence.
Interspinous process devices are small implants placed between the bony spinous processes at the back of the lower spine. They are best known by brand names such as X-STOP, Coflex, Aperius and DIAM, and were designed mainly to treat the leg symptoms of lumbar spinal stenosis — a narrowing of the spinal canal — by holding the segment in slight flexion and so opening up the space for the nerves, without formal decompression or fusion. I do not implant interspinous devices. I have written this overview because patients sometimes encounter them and deserve a candid account: while the idea is simple and appealing, the independent evidence has been disappointing, with notably high reoperation rates and questions over whether the devices add anything to established treatments.
For information only — not medical advice. The content on this page is patient education to help you understand a condition or treatment. It is not a substitute for personalised assessment by a qualified clinician. Always consult your doctor or specialist about your own symptoms, diagnosis, and treatment decisions.
The idea behind interspinous spacers
In lumbar spinal stenosis, the space around the nerves narrows, and the symptoms — typically leg pain and heaviness on walking that eases on bending forward or sitting — are often worse when the spine is extended and better when it is flexed. Interspinous devices exploit this: by sitting between the spinous processes, they gently limit extension at that level and hold it slightly flexed, aiming to keep the canal more open. Their appeal was that they could be inserted through a small approach, sometimes under local anaesthetic, without removing bone or fusing the spine. On the surface this looks like a minimal, low-risk solution.
What the evidence actually shows
The early manufacturer-sponsored trials of X-STOP reported benefit over non-operative care, and later trials of Coflex compared it with decompression and fusion. But the independent and longer-term evidence has been much less favourable. An independent randomised trial comparing X-STOP with straightforward surgical decompression found similar symptom relief but a much higher reoperation rate in the device group. Systematic reviews and meta-analyses have repeatedly concluded that interspinous spacers carry higher reoperation rates and higher costs than decompression, with weak overall evidence. Complication reports include fracture of the spinous process on which the device rests — particularly in patients with degenerative slippage — and device-specific failures. Several devices have effectively left the market: the Aperius spacer was withdrawn by its manufacturer, and X-STOP was subsequently discontinued. Cochrane reviews of surgery for stenosis more broadly have found the evidence too weak to favour these devices. The honest summary is that interspinous spacers have not shown a convincing advantage over standard decompression and are associated with a high rate of further surgery.
Why patient selection and the fracture risk matter
Because these devices bear load through the spinous processes, they are vulnerable to bony fracture, and this risk is higher in older patients with weaker bone and in those with degenerative spondylolisthesis (a small forward slip of one vertebra on another). Analyses of complications have proposed anatomical selection criteria precisely because outcomes were so dependent on choosing the right patient. When a technology needs careful selection simply to avoid a high failure rate, and still does not clearly outperform the standard operation, its role becomes hard to justify.
Why I do not implant these devices
I do not implant interspinous process devices. My reasons follow directly from the evidence: independent studies have shown high reoperation rates, several of the devices have been withdrawn or discontinued, and the spacers have not demonstrated a clear advantage over well-performed decompression, which remains the established treatment for symptomatic stenosis. This page is not intended to alarm anyone who already has such a device and is doing well; it is intended to give an honest account of why the enthusiasm for these implants has faded and why I do not use them.
This page is for general education only and is not a substitute for personal medical advice. It does not describe a procedure I offer. Decisions about surgery for lumbar stenosis should be made with your treating surgeon after discussion of the evidence and the established alternatives.
Evidence & further reading
- —Zucherman JF, et al. Spine. 2005. X-STOP FDA multicentre RCT vs non-operative care, 2-year. PMID 15959362
- —Strömqvist BH, et al. Spine. 2013. Independent RCT: X-STOP vs decompression — much higher reoperation with device. PMID 23403549
- —Davis RJ, et al. Spine. 2013. Coflex FDA IDE RCT vs decompression and fusion, 2-year. PMID 23680830
- —Bae HW, et al. Neurosurgery. 2016. Coflex RCT vs instrumented fusion, 3-year. PMID 27050538
- —Tuschel A, et al. Spine. 2013. X-STOP implant survival: high failure rate. PMID 21311406
- —Kim DH, et al. Spine J. 2012. Spinous-process fracture after interspinous spacer. PMID 22622239
- —Barbagallo GM, et al. Neurosurgery. 2009. X-STOP complications and anatomical selection score. PMID 19574832
- —Postacchini R, et al. Spine J. 2011. Aperius vs open decompression: open surgery better, more reoperation with device. PMID 22005077
- —Wu AM, et al. PLoS One. 2014. Meta-analysis: higher reoperation with spacer vs decompression. PMID 24809680
- —Poetscher AW, et al. PLoS One. 2018. Systematic review/meta-analysis: weak evidence, higher reoperation and cost. PMID 29979691
- —Zaina F, et al. Cochrane Database Syst Rev. 2016. Surgical vs non-surgical for stenosis: low-quality evidence. PMID 26824399
- —Ramesh A, et al. Neurosurg Rev. 2016. Review of the Aperius device (subsequently withdrawn). PMID 26324829
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