subacromial bursitis

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Subacromial-subdeltoid bursitis refers to the inflammation of the subacromial-subdeltoid bursa and is a common cause of shoulder pain.

Epidemiology

It is quite common and one of the main causes of shoulder pain . Incidence increases with age. It is frequently seen in people with overhead activities.

Risk factors

baseball pitcher, spear thrower
tennis
factory workers / manual laborers
unstable os acromiale

Associations

subacromial impingement
rotator cuff injury
rheumatoid arthritis
crystal deposition
persisting pain in operated patients

Clinical presentation

Patients usually complain of localized pain and tenderness in the anterolateral part of the shoulder just underneath the acromion and acromioclavicular joint.

Complications

Chronic subacromial-subdeltoid bursitis can result in rotator cuff injury.

Pathology

The pathological correlate of subacromial-subdeltoid bursitis is an inflammatory change of the bursa consistent with an increased amount of fluid and collagen formation e.g. as a result of excessive friction. Like other sorts of inflammatory conditions, subacromial-subdeltoid bursitis can be subdivided into "acute", "chronic" and "recurrent". The fluid can become hemorrhagic. In chronic bursitis, the wall becomes thicker due to the formation of collagen and might even calcify and in a rare case scenario, rice bodies might be found . In case of an associated full-thickness rotator cuff tear, there will be a communication to the glenohumeral joint.

Etiology

Subacromial bursitis may have the following causes .

excessive friction due to repetitive stress, overuse activity and/or subacromial impingement
acute trauma
rotator cuff injury
crystal deposition disease
rheumatoid arthritis
infection
pigmented villonodular synovitis (rare)

Location

The subacromial-subdeltoid bursa is proximally located deep to the overlying deltoid muscle and coracoacromial arch and superficial to the rotator cuff tendons and the rotator interval. Distally it can be seen between the deltoid muscle and the humeral shaft .

Radiographic features

Subacromial-subdeltoid bursitis will be mostly imaged on ultrasound and MRI and is then seen as fluid accumulation within the distended bursa.

Plain radiograph

X-rays are usually done to exclude other causes of shoulder pain e.g. calcific tendinitis.

CT

Subacromial-subdeltoid bursitis is hypodense with an enhancing wall after contrast but will be mostly an incidental finding on CT . Air inclusions might be found in case of septic subacromial-subdeltoid bursitis . Calcium deposits might be found in concomitant calcific tendinitis .

Ultrasound

On ultrasound, the bursa is seen as an anechoic fluid-filled distended structure, with a hyperechoic wall and sometimes synovial hypertrophy. In the case of hemorrhage, there might be hyperechoic blood .

MRI

On MRI subacromial-subdeltoid bursitis will be seen as a distended fluid-filled structure between the deltoid muscle and the acromion and the supraspinatus/infraspinatus tendons. In case of an associated full-thickness rotator cuff tear, there will be a communication to the glenohumeral joint.

Signal characteristics

T2: hyperintense
T1: hypointense
T1 C+ (Gd): hypointense with contrast enhancement of the synovial lining

Radiology report

The radiological report should include a description of the following:

signs of bursitis that is distension of the bursa and possible rim enhancement
communications with the glenohumeral or acromioclavicular joint
comment on associated findings in particular rotator cuff injury
risk factors and signs of subacromial impingement e.g. hooked acromion, anterior and/or lateral downslope, acromioclavicular joint arthrosis, os acromiale

Treatment and prognosis

Subacromial-subdeltoid bursitis is usually managed conservatively with activity modification, physical therapy, nonsteroidal anti-inflammatory drugs and corticosteroid injections and most patients respond to conservative therapy. Surgical management can be done arthroscopically or with an open approach is reserved for conservative treatment failure in defiant cases.

Treatment complications

infection after steroid injection (rarely)