MR Imaging of Rotator Interval, Long Biceps, and Associated Injuries in the Overhead-throwing Athlete

The rotator interval between supraspinatus and subscapularis is proving to be an important anatomic and functional region of the shoulder. Appreciation of the anatomic structures, functional importance, and mechanisms of injury are invaluable in appropriate assessment, both by physical examination and diagnostic MR imaging. The long biceps tendon; the superior labrum and labral-biceps anchor; the coracohumeral ligament merging with the rotator interval capsule and the superior glenohumeral ligament; the ligamentous reflection pulley for the long biceps tendon at the far lateral margin of the interval extending to the lesser tuberosity and proximal bicipital groove, bounded by the distal superior margin of the subscapularis and anterior margin of the supraspinatus tendons; and the transverse humeral ligament extending between the lesser and greater tuberosities along the proximal bicipital groove all are intimately associated in this region and may be injured together. Understanding of the anatomy and function of the rotator interval continues to evolve. Rotator interval injury may be better understood as a complex or spectrum rather than an isolated lesion. When any one of the spectrum of associated injuries is suspected or found, all of the other possible associated injuries should be considered and evaluated, both on clinical and MR imaging evaluations.