• PDFS axial demonstrates increased fluid type signal at the Subscapularis Tendon insertion in keeping with a deep surface partial tear.

• Deep surface is where the tears commonly begin.

• Look for discontinuity of tendon fibres and increased fluid type signal intensity on T2 or PD Fat Sat (T2FS/ PDFS) images.

• T2FS sagittal demonstrates increased fluid type signal at the Subscapularis Tendon insertion in keeping with a deep surface tear.

• I find the sagittal scans much better to spot tears before I look at the axial scans.

• Look for discontinuity of tendon fibres and increased fluid type signal intensity on T2 or PD Fat Sat (T2FS/ PDFS) images.

Muscle atrophy and fatty infiltration are two important findings to look for in any rotator cuff tendon tear.

• MUSCLE ATROPHY,
  1. Look for reduction in size of the muscle and reduction in muscle fibres.
  2. For subscapularis this is best assessed on Sagittal T1 pr PD scans.
  3. Do not assess on axial or Fat saturated images as its harder.
  4. Extent of muscle atrophy important to report as it affects prognosis of tendon repairs.

• FATTY INFILTRATION,
  1. Occurs after atrophy commences
  2. Fat cells infiltrate the muscle belly.
  3. Look for increased T1 or PD signal in the muscle.
  4. For subscapularis this is best assessed on Sagittal scans.
  5. Do not assess on axial or Fat saturated images. Fat saturation will remove the fat signal and you cant assess the amount of fatty infiltration.
  6. Extent of fatty infiltration important to report as it affects prognosis of tendon repairs.

• Axial scan. Biceps tendon (Both pink arrows) medially subluxed and perched on top of the medial margin of the bicipital groove (Green arrow).
  
  

• This was a result of a subscapularis tear (not shown). See the next tab that explains how a subscapularis tear and biceps subluxation/dislocation are connected.
  
  

• Increased intermediate signal in the biceps tendon from tendonosis.

• Wonderful histological image of the relationship of subscapularis attachment to the biceps tendon in the bicipital groove where subscapularis forms a medial wall and prevents medial movement of biceps.
  
  
• This explains why a tear of subscap can result in medial subluxation/dislocation of the biceps tendon.

Image from: Tamborrini G et al. The Rotator Interval Ultrasound Int Open 2017; 3: E107–E116.