Arthroscopic subacromial decompression for subacromial shoulder pain (the CSAW trial)

Probably the biggest paper out this week, it’s the first study to compare a shoulder surgery with a placebo intervention (in this case an investigational arthroscopy). It’s also the largest study to compare surgery with no treatment.  313 patients randomised to 3 groups: decompression (n=106), arthroscopy only (n=103), no treatment (n=104).

Open access: YES

Published online: 20 Nov 2017, The Lancet

CSAW is short for ‘Can Shoulder Arthroscopy Work?’. It’s a group set up to for this particular trial and other research work as well, funded by Arthritis Research UK.

Added value of this study

“To our knowledge, this is the largest study to compare surgery with no treatment and is the first published trial of shoulder surgery to include a placebo comparison. Both types of surgery were better than no treatment, but the differences were not clinically significant, which questions the value of this type of surgery to patients. There were also no differences in outcomes between decompression surgery and placebo surgery (arthroscopy only) for these indications. The mechanism of the treatment effect in the patients who received surgery might be the result of placebo, postoperative physiotherapy, or other factors. Removal of bone spurs and soft tissue conferred no clear added benefit.”

Implications of all the available evidence

During the past three decades, clinicians and patients with subacromial shoulder pain have accepted minimally invasive arthroscopic subacromial decompression surgery in the belief that it provides reliable relief of symptoms at low risk of adverse events and complications. However, the findings from our study suggest that surgery might not provide clinically significant benefit over no treatment, and that there is no benefit of decompression over arthroscopy only. These results should be shared with patients considering surgery.


Following similar studies directed at knee arthroscopic procedures, shoulder surgeries are coming under similar scrutiny over their effectiveness. We must remember that many of these procedures have been carried out without high level evidence in the first place. After decades the evidence is finally catching up and casting serious question on the clinical significance of these procedures. I suspect this study will cause some reactions from the medical community as the knee studies did when they were published.

As mentioned earlier, this study is the largest to compare surgery to no treatment, which is a new finding. There have been several studies in recent years comparing shoulder surgeries to exercise which you can refer to in this excellent infographic created by Jeremy Lewis:

Jeremy Lewis SIS inforgraphics

The surprising thing I guess from this study is how small an effect both decompression and arthroscopy only  had on these patients. And to add to that, some of the effects in these two intervention groups may also be due to post-operative physiotherapy, this means that technically the effects may have even been lower without the post-op physio, but we cannot assume unless it’s proven. From the other studies above, exercise seems to match surgical intervention in terms of outcomes, that is great, but again from this study it seems that that is not a whole lot of difference when compared to no treatment at all. That’s a bit disappointing, but I guess what this study shows us is that many patients probably don’t need to undergo a decompression surgery for subacromial shoulder pain. Of course the decision is still up to the patient, but surgeons should lay out all the evidence in an accurate manner so that patients can make an informed decision.

This is an open access paper so please click on the link below to read the full article for more details:

Beard, D. et al (2017) Arthroscopic subacromial decompression for subacromial shoulder pain (CSAW): a multicentre, pragmatic, parallel group, placebo-controlled, three-group, randomised surgical trial. The Lancet.


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