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Long term results of spinal fusion: good news and bad?

The results of the long-term Swedish lumbar spine study seemed mixed at first, but are probably just negative

Paul Ingraham • 5m read

An important long-term experiment compared spinal fusion to physiotherapy over more than a decade seemed to produce a contradictory result that “prevents a strong conclusion.” But the waffling wasn’t necessary. The good-news-bad-news conclusion was a bit of an illusion. The authors cherry-picked the best possible sounding news from their own data, creating the appearance of uncertainty about spinal fusion where in fact there was none.

Spinal fusion mostly doesn’t help people. That was the actual result.

The Swedish lumbar spine study

The study in question, by Hedlund et al, was published in 2016.1 They followed the cases of 294 patients with chronic low back pain for many years, comparing patients who had spinal fusion surgery to those who received only non-specific physiotherapy.

There was no important difference between the two groups in many ways — such as work status, disability, and the amount of medication taken.

Spinal fusion seemed to be a clear winner measured in terms of the patient’s own opinion of how bad their back pain was (“global assessment”). That was the primary outcome.

Surprising good news for a spinal surgery, right?

But, despite the fact that spinal fusion patients felt like they were better off, they weren’t acting like it, according to various indirect objective measurements. The authors concluded that the discrepancy “prevents a strong conclusion.”

But it shouldn’t have. There’s not nearly as much of a discrepancy as it seems.

Manufacturing uncertainty

That clash between primary and secondary outcomes is quite interesting, but it’s also a bit of illusion created by a disingenuous abstract. In the same issue of The Spine Journal, Mannion, Brox, and Fairbank politely call bullshit.2 They declare that the focus on one slice of good news in the data is “highly biased and selective.” Being too dismissive of a clearly positive primary outcome is treading on thin ice, but they do it right. I’ll quote their comments in full below, but here’s the problem in a nutshell:

And so Mannion et al. draw a much stronger negative conclusion from the same data (and other similar recent studies): spinal fusion mostly does not work.

“Consensus at last!” they declare in their title. “Long-term results of all randomized controlled trials show that fusion is no better than non-operative care in improving pain and disability in chronic low back pain.” Such as their own review in 2013.3 Their comments in full:

We encourage the reader to consider carefully the use of the only statistically significant primary outcome as the focus of the long-term results in the Swedish study. Comprehensive analyses and detailed results for the serial measures of pain and disability are found in the tables of their paper. We believe that the long-term results for all primary outcome measures have been under-communicated, particularly in the abstract. The abstract should have summarized the results for all the (original) primary outcomes, and for “global assessment” also using the ITT analysis. We disagree with the conclusion that “from the patient’s perspective, reflected by the GA, lumbar fusion surgery is a valid treatment option in CLBP”. This is a highly biased and selective interpretation; the ODI, pain, and quality of life measures also represent the patient’s perspective. The abstract should have stated “on the other hand, the other primary outcome measures suggested no differences,” not simply that “secondary outcome measures suggested that there was still substantial disability at long-term after both treatments.”

It is normal practice to look at a range of outcome measures to ensure that the overall data tell a consistent story. In all analyses other than the ITT (which did indeed deliver consistent findings with all outcome measures), the prospectively rated measures of pain, disability, and quality of life told the same story, with only the global assessment delivering different findings. Normally, one might go with the majority, but the Swedish group instead decided to focus on the global assessment. We consider this highly biased reporting and hope that there was no conflict of interest in this group of surgeon investigators (see Mannion et al.).

We welcome the publication of the Swedish group’s longterm outcomes, with a commendable follow-up rate. Their data were originally analyzed in combination with those from the Norwegian and United Kingdom RCTs, but were then unexpectedly withdrawn, just before publication. It should now be possible to pool the findings in a mixed model analysis of the original data, or in a meta-analysis, to deliver an even stronger, evidence-based message to the spine community.

About Paul Ingraham

Headshot of Paul Ingraham, short hair, neat beard, suit jacket.

I am a science writer in Vancouver, Canada. I was a Registered Massage Therapist for a decade and the assistant editor of ScienceBasedMedicine.org for several years. I’ve had many injuries as a runner and ultimate player, and I’ve been a chronic pain patient myself since 2015. Full bio. See you on Facebook or Twitter, or subscribe:

Notes

  1. Hedlund R, Johansson C, Hägg O, et al. The long-term outcome of lumbar fusion in the Swedish lumbar spine study. The Spine Journal. 2016 May;16(5):579–87. PubMed #26363250 ❐
  2. Mannion AF, Brox JI, Fairbank JC. Consensus at last! Long-term results of all randomized controlled trials show that fusion is no better than non-operative care in improving pain and disability in chronic low back pain. Spine J. 2016 May;16(5):588–90. PubMed #27261844 ❐
  3. Mannion AF, Brox JI, Fairbank JC. Comparison of spinal fusion and nonoperative treatment in patients with chronic low back pain: long-term follow-up of three randomized controlled trials. Spine J. 2013 Nov;13(11):1438–48. PubMed #24200413 ❐

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