The Anomalous Insertion of Pectoralis Minor (Le Double Type III): A Case Report

Introduction: The pectoralis minor muscle originates from the third to fifth ribs of the chest wall and inserts at the medial side of the coracoid process of the scapula. It contributes to the abduction of the scapulothoracic joint and the downward movement of the shoulder. The anomalous insertion of pectoralis minor beyond the coracoid process is recognized since the 19th century. This study aimed to report the curious case of the anomalous insertion of pectoralis minor at greater tuberosity via rotator interval. Case Report: A unilateral anomalous insertion of pectoralis minor muscle was found on the right side during the routine dissection of the upper limb in a sixty-year-old male cadaver. The anomalous attachment was present beyond the coracoid process which extended to the underneath of the coracoacromial ligament. After cutting the coracoacromial ligament, the tendon was located in the rotator interval, i.e., followed by its final insertion at greater tuberosity along with the tendon of the supraspinatus muscle. Three variations of anomalous tendon insertion were identified based on the classification of Le Double. In this case, type IIIM of Le Double classification was found; muscle belly (not tendon) crossed the coracoid process and attached at greater tuberosity. The muscle was separated from the coracoid process by a very thin bursa. Conclusion: The pectoralis minor tendon may be found in the rotator interval, and surgeons should be careful during rotator cuff repairs.