Capsular ligaments of the shoulder. Anatomical and functional study of the anterior superior capsule.

One hundred shoulders of 50 cadavers were dissected using the anterior approach. The normal appearance of the capsule, particularly the anterior superior, and the functions of the structures during passive motion were noted. There was a distinct capsular pattern with a Z formation which included the coracohumeral ligament and the superior, middle, and inferior glenohumeral ligaments. The middle and proximal capsular structures appeared to restrain external rotation. The coracohumeral ligament aided in restraint of external rotation at the lower range of abduction. The middle glenohumeral ligament was critical in restraining external rotation between 60 degrees and 90 degrees of abduction. It was readily identifiable except in a small percentage of individuals, who had a weak or absent ligament. The large capsular opening sometimes seen in shoulder repairs is due to an absent or attenuated middle glenohumeral ligament. Both the coracohumeral and middle glenohumeral ligaments were found to support the dependent arm.