Subacromial impingement

Changed by Arlene Campos, 7 May 2024
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Disclosures - updated 9 Jun 2023: Nothing to disclose

Updates to Article Attributes

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Subacromial impingement is the most common form of shoulder impingement and occurs secondary to attrition between the coracoacromial arch and the underlying supraspinatus tendon or subacromial bursa, leading to tendinopathy and bursitis respectively.

Pathology

Aetiology

Radiographic features

Primarily, subacromial impingement is a clinical diagnosis and one should not make a diagnosis or exclude it solely based on imaging. However, imaging has an important role in supporting the diagnosis, finding the possible cause as well as sequelae of impingement. 

Static imaging modalities such as MRI and radiographs occasionally depict reduced subacromial distance as indirect evidence: 

Anecdotal experience also suggests that slight contact between the coracoacromial arch and the subacromial bursa can occur in healthy individuals; yet, significant contact or snapping between these two structures are not common in the absence of symptoms and suggest clinically relevant impingement 5.

Ultrasound

Normally, during shoulder abduction there is depression of the humeral head to allow space for the supraspinatus and the subacromial subdeltoid bursa to slide under the acromion.

Dynamic ultrasound may depict abnormal contact between the coracoacromial arch and peritendinous tissue during shoulder abduction; however, dynamic diagnosis at ultrasound is not free of controversy: although earlier studies have demonstrated thickening of the subacromial bursa following shoulder abduction in symptomatic shoulders,1-3 a more recentan investigation found no significant difference in the degree of bursal gathering in impingement patients compared with healthy volunteers 4.

Treatment and prognosis

Complications

Related pathology

Less common types of shoulder impingement include:

  • -</ul><p>Anecdotal experience also suggests that slight contact between the coracoacromial arch and the subacromial bursa can occur in healthy individuals; yet, significant contact or snapping between these two structures are not common in the absence of symptoms and suggest clinically relevant impingement <sup>5</sup>.</p><h5>Ultrasound</h5><p>Normally, during shoulder abduction there is depression of the humeral head to allow space for the supraspinatus and the subacromial subdeltoid bursa to slide under the acromion.</p><p>Dynamic ultrasound may depict abnormal contact between the coracoacromial arch and peritendinous tissue during shoulder abduction; however,&nbsp;dynamic diagnosis at ultrasound is not free of controversy: although earlier studies have demonstrated thickening of the subacromial bursa following shoulder abduction in symptomatic shoulders,<sup>1-3</sup> a more recent investigation found no significant difference in the degree of bursal gathering in impingement patients compared with healthy volunteers <sup>4</sup>.</p><h4>Treatment and prognosis</h4><h5>Complications</h5><ul>
  • +</ul><p>Anecdotal experience also suggests that slight contact between the coracoacromial arch and the subacromial bursa can occur in healthy individuals; yet, significant contact or snapping between these two structures are not common in the absence of symptoms and suggest clinically relevant impingement <sup>5</sup>.</p><h5>Ultrasound</h5><p>Normally, during shoulder abduction there is depression of the humeral head to allow space for the supraspinatus and the subacromial subdeltoid bursa to slide under the acromion.</p><p>Dynamic ultrasound may depict abnormal contact between the coracoacromial arch and peritendinous tissue during shoulder abduction; however,&nbsp;dynamic diagnosis at ultrasound is not free of controversy: although earlier studies have demonstrated thickening of the subacromial bursa following shoulder abduction in symptomatic shoulders,<sup>1-3</sup> an investigation found no significant difference in the degree of bursal gathering in impingement patients compared with healthy volunteers <sup>4</sup>.</p><h4>Treatment and prognosis</h4><h5>Complications</h5><ul>

References changed:

  • 3. Read J & Perko M. Shoulder Ultrasound: Diagnostic Accuracy for Impingement Syndrome, Rotator Cuff Tear, and Biceps Tendon Pathology. J Shoulder Elbow Surg. 1998;7(3):264-71. <a href="https://doi.org/10.1016/s1058-2746(98)90055-6">doi:10.1016/s1058-2746(98)90055-6</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/9658352">Pubmed</a>
  • 6. Cone R, Resnick D, Danzig L. Shoulder Impingement Syndrome: Radiographic Evaluation. Radiology. 1984;150(1):29-33. <a href="https://doi.org/10.1148/radiology.150.1.6689783">doi:10.1148/radiology.150.1.6689783</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/6689783">Pubmed</a>
  • 9. Amit P, Paluch A, Baring T. Sharpened Lateral Acromion Morphology (SLAM Sign) as an Indicator of Rotator Cuff Tear: A Retrospective Matched Study. JSES Int. 2021;5(5):850-5. <a href="https://doi.org/10.1016/j.jseint.2021.05.013">doi:10.1016/j.jseint.2021.05.013</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/34505095">Pubmed</a>
  • 3. Read JW, Perko M. Shoulder ultrasound: diagnostic accuracy for impingement syndrome, rotator cuff tear, and biceps tendon pathology. J Shoulder Elbow Surg. 1998;7 (3): 264-71. <a href="http://www.ncbi.nlm.nih.gov/pubmed/9658352">Pubmed citation</a><span class="auto"></span>
  • 6. Cone RO, Resnick D, Danzig L. Shoulder impingement syndrome: radiographic evaluation. Radiology. 1984;150 (1): 29-33. <a href="http://dx.doi.org/10.1148/radiology.150.1.6689783">doi:10.1148/radiology.150.1.6689783</a> - <a href="http://www.ncbi.nlm.nih.gov/pubmed/6689783">Pubmed citation</a><span class="auto"></span>
  • 9. Amit P, Paluch A, Baring T. Sharpened Lateral Acromion Morphology (SLAM Sign) as an Indicator of Rotator Cuff Tear: A Retrospective Matched Study. JSES International. 2021;5(5):850-5. <a href="https://doi.org/10.1016/j.jseint.2021.05.013">doi:10.1016/j.jseint.2021.05.013</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/34505095">Pubmed</a>

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