Os Acromiale

Description

Radiographic (A) and Illustration (B) of Os Acromiale

The types of os acromiale: (A) the space between the os pre-acromiale and the acromion; (B) the space between the os meso-acromiale and the acromion (note there is a communication with the acromioclavicular joint, found in all our patients); and (C) the space between the os meta-acromiale and the acromion

Name

• Os Acromiale
• Bipartite Acromion
• Unfused acromial apophysis
• Unfused acromion
• Persistent acromial ossicle
• Accessory acromial ossicle

General

• Anatomical variant representing an unfused accessory ossification center of the acromion
• Often an incidental finding, it may become symptomatic

Epidemiology

• Relatively common
• Seen in 8% of the population
• Bilateral in 60% of individuals

Subtypes

• Classified on their pattern of articulation with the acromion from proximal to distal
  • Basiacromial
  • Meta-acromial
  • Mesoacromial
  • Preacromial
• Meta- and mesoacromial are the most common

Radiographic Features

• Best seen on axial views

Ultrasound

• Can be identified, especially in patients with pathology

MRI

• Best seen in the superior axial plane
• Can easily be mistaken for a normal acromioclavicular joint

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Clinical Significance

• Symptomatic Os Acromiale

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See Also

• Accessory Bones Main
• Radiology Main
• Shoulder Anatomy Main

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