Arthroscopic surgery - the siren song of an ineffective procedure

I do spend quite a bit of time banging on about evidence, plausibility and the like, but it’s nice to know I’m not the only one.

Dr Rachelle Buchbinder is Professor of Clinical Epidemiology at my old medical school. She has developed a formidable reputation for asking obvious and uncomfortable questions about various new and much-vaunted treatments. As she is Joint Coordinating Editor of the Cochrane Musculoskeletal Group I frequently read papers she has contributed to and I think she is one of the giants of critical thinking in musculoskeletal practice. Her most recent editorial in a big time journal returns to one of my pet bugbears - the lack of rigorous evidence for many surgical interventions which could be safely studied in randomised control tials (RCTs).

The trial under discussion was a meticulously done comparison between people with a torn meniscus cartilage in their knee and early signs of osteoarthritis who were randomly assigned to have arthroscopic surgery on it, or appropriate physiotherapy. The surgical procedure studied was meniscectomy, whereby the surgeon uses keyhole surgery to trim the torn meniscus cartilage, and ‘tidy up’ the cracked and worn lining cartilage. Most people would agree that it sounds like a reasonable thing to do in the circumstances. Certainly it is a frequently done procedure, with the study quoting a figure of more than 460,000 being done a year in the USA alone.

To cut to the important bit, the study showed that there seemed to be no additional benefit to the patient by 12 months following surgery. Even the people who were assigned to the physio group who then crossed over and had surgery (which was about 30% of them) did not fare any better.

The importance of establishing efficacy of treatments before they are offered widely is well understood for new drugs. Love it or hate it, Big Pharma spends elephant dollars on testing efficacy before releasing drugs onto the market. There are a few fairly common operations (including the one in the study) which would not see the light of a pharmacy shelf if they were assessed like medications, with benefits being weighed against risks.

So why do surgeons keep doing these procedures?

I will resist the troll’s answer that it’s just for the money. Orthopaedic surgeons can make a perfectly good living doing nothing but strongly-evidenced procedures. Really, they don’t need the money.

My guess is that studies like the above one don’t map very accurately to the real world because of the Hawthorne effect. Surgery provides a compelling reason to adhere to a physiotherapy regimen, and the social experience of surgery is well-demonstrated to have huge placebo effects. In the real world, if someone is in crippling pain, their motivation to stick with a physio program wanes easily. The siren song of a procedure with a nice rationale (‘get in, have a look and tidy up’) and fairly routine risks looks irresistable compared to slogging out the weeks and months of exercises with the sneaking suspicion that you are missing out on a short cut.

More subtly, the surgeon wishes to help, and is likely to be convinced by the patient’s sworn protestations of strict adherence to the physio program. Certainly this tendency is evident in the study, with fully a third of the group randomised to intensive physiotherapy crossing over the have surgery. The study population probably had a much better adherence to their exercises than a similar group of real-world patients. There is nothing left to do, it seems, but operate.

I wish to emphasise at this point that I’m not trying to say that people in this situation are foolish or weak for having surgery. More that the belief on everyone’s part that surgery will help is so overwhelming that even this very convincing evidence of lack of effectiveness will seem counterintuitive and somehow really hard to believe.

It demonstrates yet again the value of having organisations like Cochrane and academic clinicians like Prof Buchbinder to ensure that every risk patients take on is likely to be met with a reward.