The Transverse Humeral Ligament

Background No study to date has isolated the anatomical nature of the transverse humeral ligament and its relationship to the biceps tendon and the anterosuperior portion of the rotator cuff. Hypothesis There is no separate identifiable transverse humeral ligament, but rather the fibers covering the intertubercular groove are composed of a sling formed by fibers from the subscapularis and supraspinatus tendons. Study Design Descriptive laboratory study. Methods A total of 14 shoulder examinations were performed on 7 matched pairs of fresh-frozen cadaveric shoulders. Magnetic resonance imaging scans were performed, followed by gross and microscopic anatomical dissection. Results In the location of the transverse humeral ligament, magnetic resonance imaging and gross dissection revealed the continuation of superficial fibers of the subscapularis tendon from the tendon body across the intertubercular groove to attach to the greater tuberosity, whereas deeper fibers of the subscapularis tendon inserted on the lesser tuberosity. Longitudinal fibers of the supraspinatus tendon and the coracohumeral ligament were also noted to travel the length of the groove, deep to the other interdigitating fibers but superficial to the biceps tendon. Histologic studies confirmed these gross dissection patterns of fiber attachment and also revealed the absence of elastin fibers, which are more commonly seen in ligamentous structures and are typically absent from tendinous structures. Conclusion There is no identifiable transverse humeral ligament, but rather the fibers covering the intertubercular groove are composed of a sling formed mainly by the fibers of the subscapularis tendon, with contributions from the supraspinatus tendon and the coracohumeral ligament. Clinical Relevance According to our findings, dislocations of the long head of the biceps must disrupt at least the deep fibers of the annular sling created mainly by the subscapularis tendon insertion. This finding provides anatomical support for the findings of a positive biceps tendon subluxation or dislocation and subscapularis tear during glenohumeral arthroscopy with a normal-appearing subscapularis during open surgery or subacromial arthroscopy.