Editorial Commentary: Magnetic Resonance Imaging Identifies the Comma Sign Seen During Arthroscopy for Subscapularis Tears.

Subscapularis tears can sometimes be difficult to identify arthroscopically. Burkart recognized this and described the "comma sign," an arc formed by a portion of the superior glenohumeral ligament/coracohumeral ligament complex, to help identify the subscapularis when it is torn and retracted. The comma sign marks the superolateral corner of the torn subscapularis tendon. In the majority of cases, the comma sign can be identified on preoperative magnetic resonance imaging. Magnetic resonance imaging findings of a comma sign include a predominantly low T1 and T2 signal intensity band of soft tissue, situated anterior and medial to the anterior glenoid labrum, extending vertically immediately lateral to the base of the coracoid, and bridging the subscapularis and supraspinatus fossa. Knowing that a comma sign is present before an arthroscopic subscapularis repair should help surgeons identify and secure the leading edge of the subscapularis for repair.