The shoulder is a ball (head of the humerus) and socket (glenoid cavity of the scapula) joint. There is a space between the acromion (which is part of the scapula) and the top surface of the humeral head, which is called the subacromial space (its height is 1-1.5 cm). This space is outlined by the acromion, coraco-acromial ligament and the coracoid process (which are parts of the scapula), which makes up the roof of the shoulder, and by the humeral head which makes up the floor of the shoulder. In this space are located tendons called the rotator cuff.
When the rotator cuff tendons, mainly the supraspinatus tendon, rubs against the roof of the shoulder repeatedly, at one point it will get inflamed and irritated, as a result it will cause pain. This is a common disorder of the shoulder, called Subacromial Impingement Syndrome (SAIS).
The SAIS can start suddenly or come on gradually. The symptoms are: pain in the top and outer side of your shoulder, which is worse when you lift your arm, especially when you lift it above your head; pain or aching at night, which can affect your sleep; weakness in your arm.
Normally people with the SAIS try first the conservative treatment (nonsteroidal antiinflammatory drugs, physiotherapy, steroid injections, etc…) and if it doesn’t work they go for surgery, Arthroscopic Subacromial Decompression (ASD). The operation aims to increase the size of the subacromial area and reduce the pressure on the tendons. It involves cutting the coraco-acromial ligament and shaving away the bone spur on the acromion bone. This allows the tendons to heal.
Does arthroscopic subacromial decompression (ASD) really work?
A study carried out in 2018 assessed the efficacy of arthroscopic subacromial decompression (ASD) by comparing it with diagnostic arthroscopy (a placebo surgical intervention), and with a non-operative alternative, exercise therapy.
122 patients with subacromial pain and unresponsive to conventional treatment; Age 35-65; Pain for 3 or more months.
59 patients ASD (arthroscopic subacromial decompression)
63 patients DA (diagnostic arthroscopy placebo)
Conclusions: Arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy at 24 months in terms of pain and functional outcomes.
It is important to know that with the advent of arthroscopy, the number of subacromial decompression procedures has increased many times between the 1980s and the 2010s. A study reported that the incidence of anterior acromioplasty increased over time with the crude rate of 3.3 per 100,000 in 1980 to 1985 to 19.0 per 100,000 in 2000 to 2005 in the US. The overall incidence was higher in men than women, with the highest incidence in patients age 41 to 64 years.
Another study compared ASD with conservative treatment (physical therapy, exercise programmes, NSAIDs, and steroid injections) in adults with atraumatic shoulder pain for more than 3 months diagnosed as subacromial pain syndrome (SAPS), also labelled as rotator cuff disease.
Results: Surgery did not provide important improvements in pain, function, or quality of life compared with placebo surgery or other options (after 1 year). Frozen shoulder may be more common with surgery.
Practical issues with surgery:
After surgery, 2 weeks off work are typically needed;
Avoid heavy lifting for one to three weeks, overhead activities for 3 months.
- Subacromial decompression versus diagnostic arthroscopy for shoulder impingement: randomised, placebo surgery controlled clinical trial – BMJ 2018;
- Arthroscopy and the dramatic increase in frequency of anterior acromioplasty from 1980 to 2005: an epidemiologic study – 2010;
- Subacromial decompression surgery for adults with shoulder pain: a clinical practice guideline -BMJ 2019;