It is possible that spine fusion surgery for back pain achieves its effectiveness through the placebo effect. I would like to make the case that it is not only possible, but also probable.
Spine fusion can be done for many reasons, but the most common reason is degenerative conditions in the lumbar spine (here). Yet there is very little evidence that spine fusion surgery for back pain is effective. It is very expensive (the implants alone are often in the tens of thousands per case), often leads to complications, often requires further surgery, is associated with increased mortality (here, are, some, good, links), and often does not even result in the spine being fused. That last one is not a big deal, because the results of the surgery are not well correlated with whether or not the spine fuses. Nor are the results related to how you fuse the spine, or whether or not you use implants (screws, rods and cages), except that “instrumented” fusions (using implants, which is now routine) are associated with more complications (Cochrane review).
The rate of spine fusion surgery is increasing and has been increasing for many years (here). The most recent data shows that in the USA, the rate has gone a long way past the rate of 1 spine fusion per 1,000 population per year. The rate has already overtaken hip replacement surgery and continues to rise. The rates of surgery vary widely across the USA, where back fusion is associated with the highest degree of practice variation (here). In my state, back fusion just beat prostatectomy as the procedure with the most regional variation (here). The US rates are far higher than most other countries, but the rates in many of those countries (like Australia) are increasing too.
Three randomised clinical trials have been published comparing surgery to non-operative treatment for back pain. There have been no sham surgery trials, but the evidence from these three trials indicate that this surgery might achieve its results through the placebo effect.
Two of the studies put spine fusion surgery up against structured non-operative treatment alternatives: cognitive behavioural therapy in one study, and intensive rehabilitation in another. These studies found no significant differences in the outcomes between the operative and non-operative groups (except that the complication rate in the surgical group was higher). As usual (and from my other blogs about placebo surgery, you will guess), both groups showed improvement. The point is that about the same proportion of patients in each group improved, by roughly the same amount.
The third study concluded that the surgical group did better. Interestingly, the surgical group didn’t do any better than in the other studies; the difference was that the non-operative group didn’t get better at all. This is because the non-operative treatment was not dressed up as something that might work (i.e., it wasn't a good placebo). The authors state that the non-operative treatment "could vary within broad but commonly used limits reﬂecting the nonsurgical treatment policy in the society”. Patients were basically given more of the treatment that they had received before (the treatment that had previously failed and that led them into the study). Faced with more of the treatment that had already failed, this group was never going to get better – there is no placebo effect in doing nothing.
Interestingly, in the rare cases that physical therapies have been compared to sham treatments, there is no difference in the results (two examples here and here)
The bottom line
My conclusion from the three trials is that if you do something that looks like it might work, is structured and has plausibility, about 2/3 of the patients will get better. Much like many of the placebo treatments already discussed in my blog. In fact, my review of spine injections showed that many patients improve with injections, but when compared to placebo injections, the results are no better.
Surgery has the exact effect I would expect it to have if it was a placebo. If it was a placebo, it would also explain why it doesn’t matter what surgical approach you use, whether or not you put any implants in, and whether or not the spine fuses.
I once attended a lecture by an internationally renowned spine surgeon who explained that nearly all treatments for back pain result in improvements in about 2/3 of the patients. I asked him why he did spine fusions for back pain, if it was no more effective than the alternatives. He said, “Because it works in about 2/3 of the patients”.
Spine surgery is not just a sugar pill; it is a much more elaborate placebo than that, and it is much more dangerous. The onus is on doctors to prove that spine fusion surgery for back pain is better than placebo before subjecting so many people to the risks of such major surgery.
Spine fusion surgery for other indications is not that clear either.
Earlier this year, a review of the indications for spine fusion surgery for the most common type of spine fracture (thoraco-lumbar burst fracture) showed that spine surgery led to similar clinical results compared to non-operative treatment, but was more expensive and associated with more complications.
Spine fusion surgery is a multi-billion dollar per year industry rife with conflicts of interest and industry influence.
I can’t possibly cover that side of it in one blog post. Many others have written extensively on this aspect of the topic. Try Shannon Brownlee from her book Overtreated, or Nortin Hadler’s cleverly titled book Stabbed in the Back for starters.
Why do surgeons still perform this operation?
The next blog post will cover this topic.