Subacromial bursitis is inflammation of the subacromial bursa, a bursa that separates the superior surface of the supraspinatus tendon from the overlying coracoacromial ligament, acromion, coracoid (the acromial arch) and from the deep surface of the deltoid muscle. The subacromial bursa helps the movement of the supraspinatus tendon of the rotator cuff in activities such as overhead work.
The subacromial bursa is also called subacromial-subdeltoid bursa.
This bursa is deep to the deltoid muscle and the coracoacromial arch and extends laterally beyond the humeral attachment of the rotator cuff. Anteriorly, it overlies the intertubercular groove, medially to the acromioclavicular joint, and posteriorly over the rotator cuff.
The main function of the subacromial bursa is to decrease friction and allow smooth motion of the rotator cuff in relation to coracoacromial arch and the deltoid muscle.
Subacromial bursitis may be present concomitantly with shoulder arthritis, rotator cuff tendinitis, rotator cuff tears, and cervical radiculopathy may be present.
Causes of Subacromial Bursitis
Subacromial bursa facilitates the motion of the rotator cuff beneath the coracoacromial arch. Any disturbance of the relationship of the subacromial structures can lead to impingement.
Known causes that cause subacromial bursitis are
- Rheumatoid arthritis
- Calcific loose bodies
- Acute Trauma
- Shoulder Overuse with overhead activities
- Throwing sports
- Professions – painting, carpentry, or plumbing
- Muscle weakness around shoulder
- Rotator cuff degeneration
- Shoulder Pathologies
- Shoulder impingement syndrome
Presentation of Subacromial Bursitis
The presentation of subacromial bursitis is similar to shoulder impingement syndrome.
The patient complains of pain in the shoulder on anterior and lateral aspects and may be associated with weakness and stiffness. Weakness without pain may suggest rotator cuff tear or suprascapular nerve compression.
The symptoms develop gradually and nighttime pain may be present at some point.
A visible swelling, redness with or without fever should alert for infection.
Overhead activities or pressure on the shoulder such as inactivity like leaning on an elbow may increase pain.
On examination, there would be tenderness located in the anterior-superior aspects of the shoulder.
On active abduction, the arc of motion may be painful between 80 and 120 degrees.
On lowering from full abduction there is often a painful catch at midrange.
The examiner performs maximal passive abduction in the scapular plane, with internal rotation, while scapula is stabilized.
This causes impingement of supraspinatus tendon against anterior inferior acromion.
It is often difficult to distinguish between pain caused by bursitis or that caused by a rotator cuff injury
- Rotator cuff tear, partial or complete
- Rotator cuff tendinosis
- Subacromial impingement
- Rheumatoid arthritis
- Calcific tendonitis
X-rays help to visualize bone spurs, acromial shape, and arthritis. Further, calcification in the subacromial space and rotator cuff may be revealed
MRI can reveal fluid in the bursa and mark the affection of adjoining structures.
Ultrasound may reveal fluid distension, synovial proliferation, and/or thickening of the bursal walls.
In case of suspected infection, aspiration of the fluid under imaging and its lab analysis should be done.
CBC, ESR, CRP may be done to rule out infection. In suspected rheumatoid arthritis cases RF or anti-CCP should be done.
Treatment of Subacromial Bursitis
Initial management of subacromial bursitis involves immobilization with a sling and NSAIDs like naproxen or ibuprofen. For pain that remains disabling after 72 hours, steroid injection of the bursa may be indicated but infection should be ruled out.
Intrabursal steroids may also be considered as primary treatment in patients who cannot tolerate NSAIDs.
Physical therapy modalities heat, ice, ultrasound, stretching and strengthening exercises help to improve mobility and relieve pain.
Bursectomy, open or arthroscopic, is reserved for patients who fail to respond to non-operative measures.
Younger patients (< 20 years) and patients between 41- 60 years of age perform better than those who were in the 21- 40 years age group. Patients > 60 years of age had the poorest results.