Acromial apohysiolysis is a finding on shoulder MRI that may be encountered in patients with an unfused acromial apophysis. It is associated with athletes in throwing sports.
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Clinical presentation
Presents with superior shoulder tenderness in a patient <25 years old, often in a young throwing athlete (~100 pitches/week in American baseball). May clinically mimic a shoulder labral tear.
Pathology
Repetitive stress across a meta-acromion-meso-acromion type unfused acromion. The injury is analogous to epiphysiolysis at incompletely fused growth plates.
Radiographic features
MRI
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STIR / PD FS
increased signal intensity across an unfused acromion
STIR sequence is useful to avoid inhomogeneous fat suppression
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T1
decreased signal intensity across an unfused acromion
Treatment and prognosis
Patients are usually treated conservatively, with rest and NSAIDs.
It is associated with an eventual os acromiale formation (86% vs. 4% control) and rotator cuff tear (after age >25 years) if the cause of the shoulder stress is not discontinued.
Practical points
in a throwing athlete with shoulder pain, edema signal intensity across an unfused acromial apophysis, and no other cause for shoulder pain consider acromial apophysiolysis
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