Subacromial decompression – Does it work?

The shoulder

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 tensons, mainly the supraspinatus tendon, rubs against the roof of the shoulder over and over, at one point it will get inflamed and irritated and 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 (Subacromial decompression versus diagnostic arthroscopy for shoulder impingement: randomised, placebo surgery controlled clinical trial – BMJ 2018 ;I need to set up external and internal links, maybe I need business account) 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)


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. This studyArthroscopy and the Dramatic Increase in Frequency of Anterior Acromioplasty from 1980 to 2005: An Epidemiologic Study -2010(I need to put an external link) 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 (external link) – Subacromial decompression surgery for adults with shoulder pain: a clinical practice guideline – BMJ 2019 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

(Double check with Baby)


Unilateral shoulder pain and bilateral MRI findings

Magnetic resonance imaging (MRI) is commonly used to diagnose structural abnormalities in the shoulder. However, clinical findings may not be the source of symptoms

In this study were evaluated over 100 individuals who reported unilateral shoulder pain, with no signs of adhesive capsulitis, no substantial range-of-motion deficit, no history of upper-limb fractures, no repeated shoulder dislocations, and no neck-related pain. All partecipants had MRI (interpreted by an orthopedic shoulder surgeon and a musculoskeletal radiologist) of both symptomatic and asymptomatic shoulders.


Abnormal MRI findings were observed in both shoulders.

Rotator cuff tendinopathy, partial-thickness tear, full-thickness tear, labrum alterations, acromial morphology (Type I, II, III), long head of biceps alterations, AC joint alterations, subacromial fluid, fatty infiltration, glenohumeral osteoarthritis.

Only the frequencies of full-thickness supraspinatus tendon tears and glonohumeral osteoarthritis (OA) were higher (about 10%) in the symptomatic shoulder according to the surgeon’s findings only.

Agreement between the musculoskeletal radiologist and shoulder surgeon ranged from slight to moderate.


Most abnormal MRI findings were not different in frequency between symptomatic and asymptomatic shoulders.

Consider additional factors to help explain patients pain – Todd Hargrove