OS ACROMIALE SHOULDER MRI RADIOLOGY (VIDEO)

An os acromiale is a persistent accessory ossification centre of the lateral acromion.

• It's normal to see the accessory ossification centre until around 15 years of age.
• But there should be complete fuse by 25.
• If there is non fusion and a persistent os after 25, it's termed an os acromiale.

It may be completely asymptomatic but there are two potential complications.  

1. Impingement on the Rotator Cuff tendons.  
2. Acromial apophysiolysis.

• There can be abnormal movement between the acromion and the OS Acromiale.
• This results in the OS moving inferiorly & impinging on the RCT.
• Additionally, if there is malalignment between the OS and the Clavicle, this can lead to narrowing of the subacromial space.
• For acromial apophysiolysis, we will look at this specifically in the next post.

• So how do you best recognise an Os Acromiale on Shoulder MRI.

• Its easy to miss if you don’t look for it specifically and the key is to look at the axial scans where it is most obvious.

• You can see it on coronal images but it's much harder and sagittals are not much help.

• See the video below which demonstrates how to find an os acromiale on MRI Shoulder.