The Anomalous Insertion of Pectoralis Minor (Le Double Type III): A case report

The pectoralis minor muscle originates from third to fifth ribs of the chest wall and inserts at the medial side of the coracoid process of Scapula. It contributes to the abduction of the scapulothoracic joint and downward movement of the shoulder. The anomalous insertion of pectoralis minor beyond the coracoid process is known since the 19th century.

Aim of the study:

 To report the curious case of anomalous insertion of pectoralis minor at greater tuberosity via rotator interval.

The Case Report: 

A unilateral anomalous insertion of pectoralis minor muscle was found on the right side during routine dissection of the upper limb in a sixty-year male cadaver. The anomalous attachment was present beyond the coracoid process which extended, underneath of coracoacromial ligament. After cutting the coracoacromial ligament, the tendon was located in the rotator interval, which was followed to its final insertion at greater tuberosity along with the tendon of Supraspinatus muscle. Three types of variations of anomalous tendon insertion were known based on the classification of Le Double. In this case, type IIIM of Le Double classification was found in which muscle belly (not tendon) crossed the coracoid process and attached at greater tuberosity. The muscle was separated from coracoid process by very thin bursa.

The pectoralis minor tendon may be found in the rotator interval, and surgeons should be careful during rotator cuff repairs.