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Long term results of spinal fusion are … well, there’s good news and bad news

PainSci » bibliography » Hedlund et al 2016
Tags: surgery, bad news, back pain, treatment, pain problems, spine

One article on PainSci cites Hedlund 2016: Complete Guide to Low Back Pain

PainSci commentary on Hedlund 2016: ?This page is one of thousands in the bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided wherever possible.

This valuable study 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 work status, disability, and the amount of medication taken. And yet 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.

Put another way, spinal fusion patients felt like they were better off … but they weren’t acting like it, according to various indirect objective measurements.

Surprising good news for a spinal surgery, right?

This clash between primary and secondary outcomes is quite interesting, but it’s also an illusion created by a disingenous abstract. In the same issue of Spine J, Mannion, Brox, and Faribank politely call bullshit (see Mannion). 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. This is also backed up by other recent long-term trials of spinal fusion (reviewed by Mannion in 2013):

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” [3]. 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. [17]).

We welcome the publication of the Swedish group’s longterm outcomes, with a commendable follow-up rate [3]. 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.

And so, ironically, I believe this paper is actually the nail-in-coffin paper for spinal fusion … despite the seemingly inconclusive and encouraging abstract.

~ Paul Ingraham

original abstract Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

BACKGROUND CONTEXT: Current literature suggests that in the long-term, fusion of the lumbar spine in chronic low back pain (CLBP) does not result in an outcome clearly better than structured conservative treatment modes.

PURPOSE: This study aimed to assess the long-term outcome of lumbar fusion in CLBP, and also to assess methodological problems in long-term randomized controlled trials (RCTs).

STUDY DESIGN: A prospective randomized study was carried out.

PATIENT SAMPLE: A total of 294 patients (144 women and 150 men) with CLBP of at least 2 years' duration were randomized to lumbar fusion or non-specific physiotherapy. The mean follow-up time was 12.8 years (range 9-22). The follow up rate was 85%; exclusion of deceased patients resulted in a follow-up rate of 92%.

OUTCOME MEASURES: Global Assessment (GA) of back pain, Oswestry Disability Index (ODI), visual analogue scale (VAS) for back and leg pain, Zung depression scale were determined. Work status, pain medication, and pain frequency were also documented.

METHODS: Standardized outcome questionnaires were obtained before treatment and at long-term follow-up. To optimize control for group changers, four models of data analysis were used according to (1) intention to treat (ITT), (2) "as treated" (AT), (3) per protocol (PP), and (4) if the conservative group automatically classify group changers as unchanged or worse in GA (GCAC). The initial study was sponsored by Acromed (US$50,000-US$100,000).

RESULTS: Except for the ITT model, the GA, the primary outcome measure, was significantly better for fusion. The proportion of patients much better or better in the fusion group was 66%, 65%, and 65% in the AT, PP, and GCAC models, respectively. In the conservative group, the same proportions were 31%, 37%, and 22%, respectively. However, the ODI, VAS back pain, work status, pain medication, and pain frequency were similar between the two groups.

CONCLUSIONS: One can conclude that from the patient's perspective, reflected by the GA, lumbar fusion surgery is a valid treatment option in CLBP. On the other hand, secondary outcome measures such as ODI and work status, best analyzed by the PP model, indicated that substantial disability remained at long-term after fusion as well as after conservative treatment. The lack of objective outcome measures in CLBP and the cross-over problem transforms an RCT to an observational study, that is, Level 2 evidence. The discrepancy between the primary and secondary outcome measures prevents a strong conclusion on whether to recommend fusion in non-specific low back pain.

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Specifically regarding Hedlund 2016:

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