Causes / typical injury mechanism: As is the case with all scapular fractures, acromion fractures are uncommon injuries that are typically associated with high-energy trauma. Specifically, patients frequently suffer these injuries after an anteriorly directed force to the shoulder.

Classic history and presentation: Patients present with a history of major trauma, such as a motor vehicle or motorcycle crash, and pain in the superolateral aspect of the shoulder. They typically have associated injuries as a result of blunt trauma.

Prevalence:

• Very rare
• Acromion fractures account for 9% of all scapular fractures, which make up 3% of shoulder fractures

Risk factors:

• High risk of severe trauma
• Osteoporosis

Pathophysiology: Direct trauma to the acromion process of the scapula.

Grade / classification system: Kuhn et al classification.

• Type I – nondisplaced
• Type II – displaced, but no narrowing of subacromial space
• Type III – displaced and narrowing of subacromial space