According to the first placebo-controlled trial in shoulder surgery, decompression surgery does not reduce shoulder pain any more than placebo surgery for people with shoulder impingement that is when the tendon rubs and catches in the joint. The study was published in The Lancet.

Furthermore, although both types of surgery were slightly more effective at reducing subacromial shoulder pain compared to no treatment, the difference was small and not likely to result in a noticeable effect.

The study involved 32 hospitals and 51 surgeons across the UK. In the study, 90, 94 and 90 people who had suffered shoulder pain for at least three months despite having physiotherapy and steroid injections underwent decompression surgery, placebo surgery or no treatment, respectively. 

Both surgeries were completed as keyhole procedures to ensure that patients were not aware of which surgery they had. Surgery participants also had one to four physiotherapy sessions afterwards, while those having no treatment only had a check-up appointment three months after the start of the trial.      

Six and 12 months after they entered the trial, the participants completed questionnaires rating their symptoms, including pain (from 0-48, with a higher number meaning less pain). Overall, symptoms diminished in all three groups from the start of the trial.

At six months, people who had  decompression surgery and those who had had placebo surgery rated their pain and function at a similar level, with no statistical difference (32.7 points and 34.2 points, respectively).

Comparatively, both forms of surgery showed a small benefit over no treatment (rated at 29.4 points in the no treatment group), however, the difference is unlikely to result in a noticeable difference in symptoms.

The authors suggest that the difference could be attributable to a number of factors, including a placebo effect related to surgery, a nocebo effect related to having no treatment, other unintended effects of the placebo surgery, or because people undergoing surgery were given physiotherapy and told to rest.

The study findings call into question the value of shoulder decompression surgery for this group of patients, and should be communicated to patients and doctors considering this type of surgery. In light of our results, other ways to treat shoulder impingement could be considered, such as painkillers, physiotherapy and steroid injections.

During the trial, six participants had a frozen shoulder (two people in each treatment group) related to the study, and one person in the placebo surgery group underwent decompression surgery for pain.

Dr Berend Schreurs, Radboud University Medical Center, the Netherlands, said that the findings send a strong message that the burden of proof now rests on those who wish to defend the standpoint that shoulder arthroscopy is more effective than non-surgical interventions.

Hopefully, these findings from a well respected shoulder research group will change daily practice. The costs of surgery are high, and although the low occurrence of complications might suggest that the surgery is benign, there is no indication for surgery without possible gain