ACROMION / ACROMIAL SPURS ON MRI: WHERE TO LOOK AND WHAT TO LOOK FOR

Beak like spurs form on the lateral tip of the acromion. They can project either:

• Laterally and parallel to the acromion
• Or project inferiorly from the tip of the acromion.

Image Above: Beak like spur (blue arrows). 

• The rounded appearance of the lateral margin of the acromion is lost.
• The cortex and marrow of the acromion are continuous around and into the spur.

These are seen on sagittal scans as they project anteriorly from the acromion and occur at the attachment site of the coraco acromial ligament.

Image Above: 

• Normal rounded appearance of anterior acromion margin (Pink arrow) at the attachment of the coraco acromial ligament (Blue arrow).

• Anterior beak like spur (yellow arrow) with loss of round anterior acromial margin.

• These spurs are more broad based and arise from the under-surface of the lateral acromion (blue arrows below).

• The Coraco Acromial ligament attaches to the under-surface and a broad traction enthesophyte arises at the insertion site.

• The normal under surface is smooth and continuous with the tip without a step in the cortex.

• When a spur forms there is a step in the cortex (Pink arrows below) giving it a broad shelf like appearance.

• The cortex is continuous around and the spur and marrow extends into the spur.