Subacromial impingement
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Subacromial impingement is by far the most common form of shoulder impingement, and occurs secondary to attrition between the coracoacromial arch and the supraspinatus tendon or subacromial bursa.
Pathology
Aetiology
- os acromiale
- type III acromion
- acromioclavicular degenerative disease
- thickening of the coracoacromial ligament
- coracoacromial ligament ossification
- shoulder instability
- post traumatic deformity
- supraspinatus over development
- low lying acromion
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 sequelaes of impingement.
- static imaging modalities such as MRI and radiographs occasionally depict reduced subacromial distance as an indirect evidence:
- type III acromion
- os acromiale
- osteophytes extruding from
ACAC joint inferiorly - subacromial/subdeltoid bursitis
-
laterallateral acromial tilt -
anecdotal experience also suggests that slight contact between the coracoacromial arch and the subacromial bursa can occur in healthy individuals
.Yet; yet, significant contact or snapping between these two structures are not common in the absence of symptoms and suggest clinically relevant impingement 5
-
dynamic ultrasound
may-
may depict abnormal contact between the coracoacromial arch and peritendinous tissue during shoulder abduction; however, dynamic diagnosis at
USultrasound 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 recent investigation found no significant difference in the degree of bursal gathering in impingement patients compared with healthy volunteers 4
-
may depict abnormal contact between the coracoacromial arch and peritendinous tissue during shoulder abduction; however, dynamic diagnosis at
ComplicationComplications
Related pathology
Less common types of shoulder impingement include:
- subcoracoid impingement: affects subscapularis
- posterosuperior impingement: involves infraspinatus
-<li><a title="Acromial types" href="/articles/acromial-types">type III acromion </a></li>-<li><a title="Os acromiale" href="/articles/os-acromiale">Os acromiale</a></li>-<li>osteophytes extruding from <span style="line-height:13.8666658401489px">AC joint inferiorly</span>-</li>-<li><a title="" href="/articles/">Subacromial/subdeltoid bursitis</a></li>-<li> lateral acromial tilt</li>-<li>-<span style="line-height:13.8666658401489px">anecdotal experience also suggests that slight contact between the coracoacromial arch and the subacromial bursa can occur in healthy individuals.</span><span style="line-height:13.8666658401489px"> Yet, significant contact or snapping between these two structures are not common in the absence of symptoms and suggest clinically relevant impingement </span><sup>5</sup><span style="line-height:13.8666658401489px"> </span>-</li>- +<li><a href="/articles/acromial-types">type III acromion </a></li>
- +<li><a href="/articles/os-acromiale">os acromiale</a></li>
- +<li>osteophytes extruding from AC joint inferiorly</li>
- +<li><a href="/articles/">subacromial/subdeltoid bursitis</a></li>
- +<li>lateral acromial tilt</li>
- +<li>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> </li>
-<li>dynamic ultrasound may depict abnormal contact between the coracoacromial arch and peritendinous tissue during shoulder abduction; however, dynamic diagnosis at US 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>- +<li>
- +<strong>dynamic ultrasound</strong> <ul><li>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,<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>
- +</li></ul>
-</ul><h4>Complication</h4><ul>-<li><a title="rotator cuff tear" href="/articles/rotator-cuff-tear">rotator cuff tear</a></li>-<li><a title="" href="/articles/">subacromial bursitis</a></li>- +</ul><h4>Complications</h4><ul>
- +<li><a href="/articles/rotator-cuff-tear">rotator cuff tear</a></li>
- +<li><a href="/articles/">subacromial bursitis</a></li>
-<a title="" href="/articles/">bicipital tendinitis</a> <sup>6</sup> </li>- +<a href="/articles/">bicipital tendinitis</a> <sup>6</sup> </li>
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