[Anomalous insertion of the pectoralis minor muscle: ultrasound findings].

PURPOSE With anomalous insertion of the pectoralis minor muscle, its distal fibers pass over the coracoid process instead of inserting on it, following sometimes a trajectory very similar to that of the coracohumeral ligament. The aim of this prospective study was to evaluate the frequency of detection of this anomalous insertion by ultrasonography. MATERIALS AND METHODS Ultrasound demonstrated the abnormal insertion of the pectoralis minor muscle by directly visualizing its fibers slipping over the coracoid process during external and internal rotation of the humerus. Three hundred and three individuals underwent ultrasound of the shoulders (64,7% female, mean age of 45 years), for a total of six hundred and six shoulders; 30% (183/606) were symptomatic. RESULTS An abnormal insertion was demonstrated in 9,57% of the examined shoulders (58/606), with a statistically significant predominance on the left side (12,2%) compared to the right side (6,9%), and of women (12,2%) compared to men (4,7%). CONCLUSION Ultrasound demonstrated an abnormal insertion of the pectoralis minor muscle in 9,57% of 606 examined shoulders. There was a female and left side predominance and no significant correlation with symptoms.