The Rotator Interval of the Shoulder: Implications in the Treatment of Shoulder Instability

Abstract

Biomechanical studies have shown that repair or plication of rotator interval (RI) ligamentous and capsular structures decreases glenohumeral joint laxity in various directions. Clinical outcomes studies have reported successful outcomes after repair or plication of these structures in patients undergoing shoulder stabilization procedures. Recent studies describing arthroscopic techniques to address these structures have intensified the debate over the potential benefit of these procedures as well as highlighted the differences between open and arthroscopic RI procedures. The purposes of this study were to review the structures of the RI and their contribution to shoulder instability, to discuss the biomechanical and clinical effects of repair or plication of rotator interval structures, and to describe the various surgical techniques used for these procedures and outcomes.

Keywords: coracohumeral ligament; rotator interval; rotator interval plication; shoulder instability.

Figure 1.

The right shoulder during diagnostic arthroscopy performed in the lateral decubitus position (viewing from posterior) demonstrating the anatomy of the rotator interval from 3 different views. HH, humeral head; LHBT, long head of the biceps tendon; SSc, subscapularis; *rotator interval capsule.

Figure 2.

Anatomy of the rotator interval, including illustrations in (A) coronal and (B) sagittal planes and (C) corresponding sagittal magnetic resonance proton density–weighted arthrogram show boundaries of the rotator interval, which are defined by the coracoid process (COR) at its base, superiorly by the anterior margin of supraspinatus tendon (SST), and inferiorly by the superior margin of the subscapularis tendon (SSc). Contents of the rotator interval include the long head of biceps tendon (BT), coracohumeral ligament (CHL), superior glenohumeral ligament (SGHL), and rotator interval capsule. The rotator interval capsule (RIC) is the anterosuperior aspect of the glenohumeral joint capsule, which merges with CHL and SGHL insertions medial and lateral to the bicipital groove. The CHL arises from the base of coracoid process, traverses through the subcoracoid fat, and inserts on the anterior humerus. IST, infraspinatus tendon. Reproduced with permission from Petchprapa et al.

Figure 3.

Schematic figures demonstrating the 2 described methods of rotator interval plication. (A) The coracohumeral ligament (CHL) is shown, originating at the base of the coracoid and inserting laterally on the humerus, outlined in ink (arrows). The CHL is made more visible with sulcus translation of the glenohumeral joint, placing the CHL under tension and isolating the structure as a consistent cord-like band of tissue. (B) Open rotator interval (RI) closure as described by Harryman et al. An open repair of the RI is performed, and the CHL is imbricated by 1 cm (C) in the medial-to-lateral direction, with the arm in 30° of external rotation. (D) Arthroscopic RI repair is performed using 2 no. 2 nonabsorbable sutures (1 medial and 1 lateral), with the arm in 30° of external rotation. Reproduced with permission from Provencher et al.

Figure 4.

Schematic representation of the 6 subtypes of variants of the rotator interval capsular opening (RICO) as described by DePalma et al based on their cadaveric dissection. Reproduced with permission from Wilson et al.