The Insertional Footprint of the Rotator Cuff: An Anatomic Study

Abstract

PURPOSE: The purpose of this study was to define the entire rotator cuff footprint and relate it to known, easily identifiable landmarks as a guide for both open and arthroscopic rotator cuff repair. Anatomic: Gross and microscopic. METHODS: The myotendinous units of the rotator cuff and their insertions onto the humerus were dissected in 20 fresh-frozen cadavers. The separate tendon insertions were identified, and their length and width measured. The character and exact anatomy of the tendons were also noted. The entire insertion was measured and referenced to the articular surface, biceps groove, and bare area of the humerus. In a separate part of the study, 6 cadavers were decalcified and thin-sliced through the supraspinatus tendon insertion. This insertion was evaluated via scanning electron microscopy (SEM). RESULTS: Our findings demonstrated a consistent pattern at the insertion of the rotator cuff. The horseshoe-shaped insertion tapers away from the articular surface in a superior-to-inferior direction. Interdigitation of the muscle units may be noted, particularly between the supraspinatus and the infraspinatus. Average maximum insertional lengths and widths were as follows: subscapularis (SC): 40 x 20 mm; infraspinatus (IS): 29 x 19 mm; supraspinatus (SS): 23 x 16 mm; and teres minor (TM): 29 x 21 mm. The SC inserted on the lesser tuberosity adjacent to the biceps groove at the edge of the articular surface. It tapered away 18 mm at its inferior border. The SS inserted at the articular surface along its entire insertion from the bicipital groove to the top of the bare area. The IS wrapped the posterior border of the SS superiorly at the articular surface and tapered away inferiorly, framing the bare area. SEM microscopy showed the SS to be adherent to the edge of the articular surface medially. As it filled the sulcus, its lateral edge extended over the edge of the greater tuberosity. CONCLUSIONS: A consistent pattern was noted at the insertional anatomy of the rotator cuff. This anatomy was related to known, easily identifiable landmarks and may serve as a guide for evaluation of size, location, and propagation patterns of rotator cuff tears, as well as for their repair. CLINICAL RELEVANCE: Knowledge of the insertional anatomy of the rotator cuff can facilitate grading and repair of rotator cuff tears.