Previous studies reported a presumably unusual bony attachment of the pectoralis minor muscle. However, less attention has been given to the insertion of the continuation to the glenohumeral joint. The purpose of this study was to evaluate the frequency of this abnormal insertion of the pectoralis minor muscle, and also to investigate the relation between this continuation and the capsule. 81 anatomic specimen shoulders from 41 cadavers were dissected. The insertion of the pectoralis minor tendon to the glenohumeral joint was carefully investigated. The pectoralis minor tendon ran beyond the coracoid process and extended to the superior portion of the glenohumeral joint in 28 out of 81 specimens (34.6%). The continuing insertion divided the coracoacrominal ligaments into two limbs. The continuation was more variable, and consisted of the whole tendon in 6, the middle part in 5, the lateral part in 15, and the medial part in 2 specimens. Furthermore, the pectoralis minor tendon inserted to the posterosuperior border of the glenoid in 6, to the greater tuberosity in 7, and both to the glenoid and the greater tuberosity in 15 specimens. The prevalence of the anomalous insertion of the pectoralis minor tendon revealed to be as high as 34.6% in the present study. This may suggest that the pectoralis minor tendon plays an important role in the stability of the glenohumeral joint.
