Anatomy and functional aspects of the rotator interval.

The anatomy of the region between the supraspinatus and subscapularis tendons, called the rotator interval, was studied in 22 shoulders of 12 cadavers. Its function was then examined by sequential cutting of tendon or rotator interval structures. The rotator interval was found to be composed of parts of the supraspinatus, subscapularis, coracohumeral ligament, superior glenohumeral ligament, and glenohumeral joint capsule. A medial part composed of 2 layers was defined and distinguished from a more lateral part composed of 4 layers. The most superior 3 layers of the lateral part formed a fibrous plate. The medial part was found to primarily limit inferior translation and, to a lesser extent, external rotation. The fibrous plate of the lateral part of the rotator interval mainly limited external rotation of the adducted arm. The coracohumeral ligament played a key role in external rotation as well as in inferior translation.