Full thickness tear

Full thickness tear: A full-thickness tendon tear appears as a focal, well-defined area of increased signal intensity on both T1- and T2-weighted images, that traverses the whole thickness of the tendon from the bursal to the articular surface.

Full-thickness supraspinatus tendon tears in two different patients. A: Coronal oblique fat-sat T2-weighted image shows full-thickness supraspinatus tendon tear without significant tendinous retraction (arrow); B: Coronal oblique fat-sat T2-weighted image in another patient shows torn retracted supraspinatus tendon (arrow).

Full-thickness tendon tears are classified according to the tear dimensions as small (less than 1 cm), medium (between 1 and 3 cm), large (between 3 and 5 cm) or massive (exceeding 5 cm). The dimensions are measured on coronal and sagittal T2 fat-suppressed images.

The degree of retraction of the torn supraspinatus tendon is typically assessed on coronal oblique images. When the tendon stump is still close to the insertion site, it is classified as stage 1. A stump retracted to the level of the humeral head is classified as stage 2, while stage 3 denotes retraction of the stump to the level of the glenoid.

Supraspinatus tendon: The most common site for rotator cuff tears is the supraspinatus tendon, especially at its distal part 1 to 2 cm from its insertion, the so called “critical zone”, where the vascularity is low and the effect of subacromial space narrowing or subacromial impingement is maximized.

Subacromial impingement. A: Coronal oblique fat-sat T2-weighted image; B: Coronal oblique fat-sat proton-density-weighted image. Both images show findings associated with subacromial impingement in the form of osteoarthritis of the acromio-clavicular joint, distended subacromial subdeltoid bursa by fluid signal (arrowhead) and focal thickening of the distal supraspinatus tendon with partial irregularity of the bursal surface reported as partial tear (arrow).

The supraspinatus tendon is best evaluated on the coronal oblique images. A potential pitfall is the magic angle artefact; that may occur whenever parallel collagen fibres are oriented at 55 degrees relative to the magnetic field. This effect is common at the distal end of the supraspinatus tendon and appears as high signal mimicking tendinitis or partial tear on short time of echo (TE) MR sequences. However, the high signal intensity disappears on using long TE sequences; for example T2 fat-suppressed sequence.

Magic angle artifact. A: Coronal oblique T1-weighted image. B: Coronal oblique fat-sat proton-density image. Images (A) and (B) show focal high signal intensity within the distal supraspinatus tendon (arrow); C: Coronal oblique fat-sat T2-weighted image shows normal signal of the supraspinatus tendon (arrow). Final diagnosis was magic angle artifact with normal tendon.