The rotator cuff is perforated anterosuperiorly by the coracoid process, which separates the anterior border of the supraspinatus tendon from the superior border of the subscapularis tendon, creating the triangular rotator interval, which is bridged by capsule. The base of the interval is the coracoid process, from which capsular tissue (the coracohumeral ligament) originates. The transverse humeral ligament at the biceps intertubercular sulcus forms the apex of the rotator interval. The coracohumeral and superior glenohumeral ligaments are considered to be structural contents of the rotator interval capsule, but each have separate origins and insertions. These ligaments are considered to be the most constant structures of the fibrous joint capsule.
Arai et al performed cadaver dissections to describe the anatomy as it relates to reconstructing the biceps sling as it exits the interval in cases of biceps subluxation. They note that an intact superior border of subscapularis is needed as well as tension in the SGHL.
Yang et al reported a descriptive anatomy study on the CHL. All were located in the rotator interval, originated from the lateral aspect of the base of the coracoid process, and had histology more consistent with capsule than ligament.
Illustrations A & B show a schematic drawing and a corresponding MRI image of the shoulder that depicts the rotator interval. Boundaries of the rotator interval include the coracoid process (COR) at its base, superiorly by anterior margin of supraspinatus tendon (SST) and inferiorly by superior margin of subscapularis tendon (SSC). Contents of rotator interval include long head of biceps tendon (BT), coracohumeral ligament (CHL), superior glenohumeral ligament (SGHL), and rotator interval capsule. Rotator interval capsule (RIC) is the anterosuperior aspect of glenohumeral joint capsule, which merges with CHL and SGHL insertions medial and lateral to bicipital groove.
Illustration C demonstrates a cadaveric image with the subscapularis tendon (black star), supraspinatus tendon (white star), and rotator interval capsule (asterisk).
Illustration D is an image of a right shoulder in the beachchair position viewed from a posterior portal showing a rotator interval closure for a patient with multidirectional instability of the shoulder.
Yang HF, Tang KL, Chen W, Dong SW, Jin T, Gong JC, Li JQ, Wang HQ, Wang J, Xu JZ.. An anatomic and histologic study of the coracohumeral ligament. J Shoulder Elbow Surg. 2009 Mar-Apr;18(2):305-10. Epub 2008 Dec 18.
PMID:19095467 (Link to Abstract)
Arai R, Mochizuki T, Yamaguchi K, Sugaya H, Kobayashi M, Nakamura T, Akita K.. Functional anatomy of the superior glenohumeral and coracohumeral ligaments and the subscapularis tendon in view of stabilization of the long head of the biceps tendon. J Shoulder Elbow Surg. 2010 Jan-Feb;19(1):58-64. Epub .
PMID:19535271 (Link to Abstract)
Netter's Concise Atlas of Orthopaedic Anatomy, Frank H. Netter, John A. Craig.