The comma sign of subscapularis tear was first described on arthroscopy but recognised later on MRI. The comma sign represents a full thickness partial width superior subscapularis tear along with torn superior glenohumeral and coracohumeral ligament insertional fibres vertically retracted via adherent fibres to a medially-displaced anterior supraspinatus tear 1,2. Two series have shown a sensitivity of ~75% (range 63-91%) and specificity of ~97% (range 94-99%) 1,2.
Radiographic features
MRI
The comma sign can be identified on any plane but best assessed in the coronal plane 2, where it is described as a low T1/T2 signal comma-shaped fibrous band anteromedial to the anterior glenoid extending vertically from the subscapularis tendon lateral to the coracoid process to the superior glenohumeral capsule 1,2.
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