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 inter nal and external rotation of the humerus and the lengths of the anteri or and posterior components of the glenohumeral capsuloligamentous com plex. Six cadaveric shoulders (with intact ligaments and humeri) were stripped of all muscles. Each shoulder was mounted in its correct anat omic position. The extent of internal and external rotation of the hum erus was then measured 36 times (at 10 degrees intervals in a 360 degr ees humeral cone of motion). One component of the glenohumeral capsulo ligamentous 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 acr oss the joint, The process of lengthening each component was repeated in 12 combinations, each with a different anterior and posterior compo nent length. Humeral rotation was measured 36 times using a specially designed goniometer. The length of the anterior component of the gleno humeral capsuloligamentous complex most affected external humeral rota tion, and the length of the posterior component most affected internal humeral rotation. However, the lengths of both the anterior and poste rior components shared in limiting rotation at a number of positions.