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THREE TYPES OF ACROMIAL SPURS ON MRI: WHERE TO LOOK AND WHAT TO LOOK FOR

ACROMIAL SPURS ON MRI : 3 APPEARANCES ON MRI

Acromial spurs can be quite small and difficult to visualise on MRI.

They are enthesophytes that arise from traction at the attachment sites of the Coraco Acromial Ligament and Deltoid.

This post looks at the three locations and most common appearances of spurs arising from the lateral aspect of the acromion.

WHAT’S THE NORMAL APPEARANCE OF THE LATERAL ACROMION?

  1. The normal lateral tip of the acromion has a smooth, ovoid contour (blue arrow).
  2. The undersurface of the acromion is also smooth and continuous (pink arrow) with no step or ledge.

subacromial spur mri shoulder normal acromion radiology education asia 1

 

1. LATERAL BEAK LIKE SPURS

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

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

subacromial spur mri shoulder radiology education asia 4

Image Above: Beak like spur ( blue arrows). 

1. The rounded appearance of the lateral margin of the acromion is lost.

2. The cortex and marrow of the acromion are continuous around and into the spur.

sub acromial spur mri shoulder radiology education asia

 

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

acromial spur anterior beak like mri shoulder anterior radiology education asia

Image Above: 

  1. Normal rounded appearance of anterior acromion margin ( pink arrow) at the attachment of the coraco acromial ligament ( blue arrow).
  2. Anterior beak like spur ( yellow arrow) with loss of round anterior acromial margin.

 

3. BROADBASED UNDERSURFACE SPURS:
      1. These spurs are more broad based and arise from the undersurface of the lateral acromion ( blue arrows below).
      2. The Coraco Acromial ligament attaches to the undersurface and a broad traction enthesophyte arises at the insertion site.
      3. The normal under surface is smooth and continuous with the tip without a step in the cortex.
      4. When a spur forms there is a step in the cortex ( pink arrows below) giving it a broad shelf like appearance.
      5. The cortex is continuous around and the spur and marrow extends into the spur.

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May 5, 2019