Prevalence and factors associated with os acromiale: a multicenter study

Area of Science:

• Orthopedics
• Radiology
• Anatomy

Background:

• Os acromiale is an accessory bone resulting from the nonunion of the acromial ossification center, with a reported prevalence of approximately 2%.
• While often asymptomatic, symptomatic os acromiale is strongly associated with rotator cuff injuries.
• This study investigated the prevalence and associated factors of os acromiale in the Japanese population.

Purpose of the Study:

• To determine the prevalence of os acromiale in the Japanese population.
• To identify factors associated with os acromiale, including its location, size, and acromial shape.
• To investigate the association between os acromiale and rotator cuff injuries.

Main Methods:

• Analysis of 6,842 shoulder magnetic resonance imaging (MRI) scans from 10 facilities (April 2018 - March 2023).
• Assessment of os acromiale prevalence, location (pre-, meso-, meta-acromion), size, and acromion shape.
• Statistical analysis using Fisher's exact test to determine associations, with significance set at P < .05.

Main Results:

• Os acromiale was identified in 76 cases (1.1% prevalence).
• Prevalence by location: 58 pre-acromion, 18 meso-acromion. No meta-acromion cases were found.
• Significant association found between the presence of os acromiale and rotator cuff injury (P < .001).

Conclusions:

• The study confirms the association between os acromiale and rotator cuff injuries.
• Prevalence of os acromiale in the Japanese population (1.1%) is lower than in non-Asian populations.
• Os acromiale size in the Japanese population tended to be smaller than in European populations.