Lumbar spine fusion: what is the evidence?

Ian Harris is an orthopaedic surgeon and academic based in Sydney. His work examines the true effectiveness of surgery as opposed to the perceived effectiveness. He is author of the book Surgery, the Ultimate Placebo. He wrote a piece for us on a recent paper he wrote on lumbar fusion.


Recently, a group of us reviewed the literature on lumbar spine fusion, which we published in the Internal Medicine Journal. The initial brief was to talk about the evidence for spine surgery in general, but thinking that was too broad, we decided to focus on fusion and the lumbar spine. We chose this topic for several reasons. Lumbar spine fusion is one of the costliest operations performed, with direct total costs (theatres, bed stay, medical, implant etc) measured in the tens or even hundreds of thousands of dollars. It is also a procedure with significant risks including blood loss, nerve injury and infection. Perhaps the greatest risk is the failure to resolve (or the exacerbation of) symptoms, and this is a common reason for the high rate of re-operation for this procedure. Furthermore, despite the complexity, risk and cost associated with this procedure, it continues to evolve (newer techniques, implants and mechanical theories) and increase in frequency.

For a procedure associated with such cost and risk, and for one performed so frequently, supporting evidence should be strong, so we aimed to review that evidence. This task was not easy, as lumbar spine fusion is performed for many different reasons. We broke down the indications and then started searching for the evidence.

The indications we covered were degenerative intervertebral disease, degenerative scoliosis, spinal canal stenosis, acute trauma and tumours. We did not cover paediatric / idiopathic scoliosis and did not look at disc replacement (another can of worms) as the comparator. We covered all systematic reviews and randomised trials.

In general, the quality of reviews and trials was poor, making it difficult to provide much certainty around our conclusions. And while the quantity of reviews was high, the number of trials on which they drew was small. For example, we found 33 reviews of fusion compared to non-operative care for low back pain, but these reviews largely drew from only 4 or 5 trials. It should be noted, however, that although the quality of trials was not high, mostly the evidence was not in favour of fusion compared to non-operative alternatives; nor was fusion clearly superior to simpler surgical alternatives (e.g. combining decompression with fusion versus decompression alone for spinal canal stenosis). For most conditions, fusions add cost and risk to treatment without providing much benefit.

While I must point out that the uncertainty around the effectiveness of spine fusion does not mean that it is not effective for some conditions in some people (for example, there was some evidence that it might be beneficial for those with spinal tumours), we should not fall into the trap of assuming that it IS effective, that we know when and for whom it will be effective. We don’t know it until someone shows it. The burden of proof is on the proponents of surgery and currently they are doing a lot of surgery and very little to generate the evidence to justify it.

The lack of high quality evidence is partly due to the lack of any incentives to generate such evidence. Surgery continues regardless of the quality or quantity of any objective experimental evidence, driven by surgeon opinion and observational evidence. But while some call for governments and insurers to demand such evidence, it is also the surgeons and other proponents themselves that should be demanding the evidence, just as they would demand similar evidence for any competing therapies.

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