Spinemathema podcast · Episode 6 · About 8 minutes · October 2026

Episodes are narrated using an AI model of Mr Sadek’s own voice, from scripts he has written and approved.

Read the full article with references: Do You Need a Fusion With Your Decompression? The Swedish Spinal Stenosis Study

Transcript

Hello and welcome to the Spinemathema podcast. I’m Ahmed Sadek, a neurosurgeon. In this episode I want to talk about a landmark trial from Sweden that asked a very practical question. If you need an operation for spinal stenosis in your lower back, do you also need a fusion?

Let me start with the condition. Lumbar spinal stenosis means the spinal canal in the lower back has become narrow. That usually happens because the discs bulge and the joints and ligaments thicken with age. The nerves running down to the legs get squeezed. People typically describe heaviness, aching or numbness in the legs when they walk, which eases when they sit down or lean forward, for example on a shopping trolley.

When this doesn’t settle and surgery is needed, the standard operation is called a decompression. The surgeon removes some bone and thickened ligament from the back of the spine to give the nerves more room.

Sometimes, though, one vertebra has also slipped forward on the one below. That’s called a degenerative spondylolisthesis. For many years, a lot of surgeons would add a fusion in that situation. A fusion means joining two vertebrae together, usually with screws and rods and some bone graft, so that the slip can’t get worse. The trouble is that a fusion makes the operation bigger. And when this Swedish trial was planned, nobody had properly tested whether adding the fusion actually made people better.

So, how did the trial work? It’s called the Swedish Spinal Stenosis Study. Between two thousand and six and two thousand and twelve, seven hospitals in Sweden recruited two hundred and forty seven people aged between fifty and eighty. All of them had stenosis at one or two levels of the lower spine, with leg symptoms on walking and back pain for more than six months. One hundred and thirty five of them, so just over half, also had a degenerative slip.

Each person was randomly assigned to one of two operations. One group had a decompression alone. The other group had the same decompression plus a fusion, most often with screws and rods. The main measure was a questionnaire called the Oswestry Disability Index, which scores how much back trouble gets in the way of daily life, on a scale from nought to one hundred. Higher scores mean more disability. The team also timed how far people could walk in six minutes.

What did they find? At two years, there was no meaningful difference. The average disability score was twenty four after decompression alone and twenty seven after fusion. Walking was much the same too: about four hundred and five metres in six minutes after decompression alone, and three hundred and ninety seven metres after fusion. And here’s the important part. The results were similar whether or not people had a slip.

The fusion operation did come with some costs. It took longer, there was more bleeding, and it was more expensive. The average hospital stay was seven point four days after fusion, compared with four point one days after decompression alone.

You might expect a fusion to at least reduce the chance of needing another operation later. It didn’t. Over an average of six and a half years, about one in five people in each group needed further surgery on the lower spine: twenty two percent after fusion and twenty one percent after decompression alone.

The researchers then followed people up to five years, and published those results in two thousand and twenty four. Ninety five percent of the eligible patients took part, which is very good. The disability scores were still similar: twenty five after decompression alone and twenty eight after fusion. Quality of life scores were actually a little better in the decompression alone group. Further surgery had been needed by twenty two percent of the decompression alone group and twenty four percent of the fusion group.

What I find interesting is that the reasons for the second operations were different. After a decompression alone, the usual reason was that the same level had narrowed again. After a fusion, the usual reason was narrowing at the level just above the fusion. A separate scan study from the same trial looked at this on magnetic resonance imaging scans, or MRI, at two years, and found new narrowing at or above the operated level in forty seven percent of the fusion group and twenty nine percent of the decompression alone group.

Now, no trial is perfect, and I want to be honest about the limitations. Nobody was blinded, so patients and surgeons knew which operation had been done. The main analysis only included people who actually had the operation they were assigned to. The slips were measured on X-rays taken lying down, which was normal practice when the trial started, but today many surgeons also look at standing and bending X-rays to see how much a slip moves. People with a sideways curve of the spine, a stress fracture of the vertebra, or previous surgery for stenosis were not included. And the trial was designed to pick up a fairly large difference in disability, so it can’t rule out a small benefit either way.

There’s one more twist. This trial was published in April two thousand and sixteen in the New England Journal of Medicine, in exactly the same issue as an American trial called SLIP. SLIP was smaller, with sixty six patients who all had a stable, mild slip, and it found a modest extra benefit from fusion in a general physical health score. The two trials used different main measures and included different patients. I’ve covered SLIP in a separate episode, and it’s worth listening to both.

So what does this mean for you? If you have lumbar spinal stenosis, even with a mild degenerative slip, this trial suggests that a decompression alone gives similar results to a decompression plus fusion over five years, with a smaller operation and a shorter stay in hospital. The Swedish authors concluded that decompression alone should be the preferred operation.

That doesn’t mean a fusion is never the right choice. Some people have features this trial didn’t include. Good questions to ask your surgeon would be whether your slip moves on standing or bending X-rays, what each operation would involve, and what the chances are of needing another operation with either approach.

And please remember: if you ever develop numbness around your bottom or genitals, new trouble passing urine or controlling your bowels, or rapidly worsening weakness in your legs, seek urgent medical help, because these can be signs of cauda equina syndrome.

This podcast is general information only and isn’t a substitute for advice about your own situation, so please speak to your own doctor. You’ll find the full article, with diagrams and all the references, at spinemathema dot com. And if you found this useful, please subscribe to our channel on YouTube. Thank you for listening.

This podcast is general information and is not a substitute for advice about your own situation. Please speak to your GP or specialist.