Abstract
The subscapularis is a very important anatomic structure that is essential for maintaining proper glenohumeral joint mechanics and shoulder function. It establishes a force couple with the infraspinatus and teres minor to stabilize the glenohumeral joint in the transverse plane. The subscapularis muscle also opposes the deltoid with humerus abduction and elevation. Recent advances in imaging and arthroscopy techniques have led to greater detection of subscapularis tendon tears. Furthermore, there have been detailed descriptions of the subscapularis insertional anatomy showing that the subscapularis tendon has 4 different facets of insertion to the lesser tuberosity. The tear patterns of the subscapularis are also different from that of the supraspinatus tendon where the complete isolated subscapularis tendon tear is not common. However, the subscapularis partial tear combined with supraspinatus or 3 tendon tears is more common, with most being first-facet tears. Clinically, upper-portion subscapularis partial tendon tears may be considered relatively benign, but biomechanically these tears result in increased external rotation and altered glenohumeral kinematics. Therefore, in my opinion, it is very important to precisely repair these partial subscapularis tendon tears for anatomic, structural, and functional restoration of the shoulder. © 2019