The role of glenohumeral capsular ligaments in internal and external rotation of the humerus.

The purpose of this study was to define the relationship between internal and external rotation of the humerus and the lengths of the anterior and posterior components of the glenohumeral capsuloligamentous complex. Six cadaveric shoulders (with intact ligaments and humeri) were stripped of all muscles. Each shoulder was mounted in its correct anatomic position. The extent of internal and external rotation of the humerus was then measured 36 times (at 10 degrees intervals in a 360 degrees humeral cone of motion). One component of the glenohumeral capsuloligamentous complex was lengthened, and the humeral rotation was again measured 36 times. The process of lengthening was done by cutting the ligament and replacing it with a beaded chain and catches sutured across the joint. The process of lengthening each component was repeated in 12 combinations, each with a different anterior and posterior component length. Humeral rotation was measured 36 times using a specially designed goniometer. The length of the anterior component of the glenohumeral capsuloligamentous complex most affected external humeral rotation, and the length of the posterior component most affected internal humeral rotation. However, the lengths of both the anterior and posterior components shared in limiting rotation at a number of positions.