Narrowing of the subacromial space with impingement on supraspinatus or infraspinatus can result from a number of causes. The most common are
- Hypertrophic changes at the Acromio Clavicular Joint
- Downward sloping acromion and
- Sub Acromial spurs. ( See the next post for this)
Image above: Normal Sub Acromial Space. 1. Acromion horizontal ( yellow arrow) 2 .ACJ no hypertrophic bony changes or synovitis ( blue arrow) 3. Clavicle ( red arrow) no spurs and 4. SST ( pink arrow) not indented and fat present over its superior surface.
Image Above: Bony hypertrophic changes ( Blue Arrow)at the ACJ narrow the subacromial space.
Image Above: ACJ Synovitis ( blue arrows) narrowing the subacromial space.
This is usually the most common pattern where there a combination of findings that result in subacromial space narrowing. 1. Acromion downward sloping ( yellow arrow) 2 .ACJ hypertrophic bony changes ( red arrow) 3. Acromial spur ( blue arrow)
See next post for Subacromial spurs