The contribution of the glenohumeral ligaments to anterior stability of the shoulder joint

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Abstract
The purpose of this study was to investigate the liga mentous stabilizing mechanisms preventing anterior instability in the glenohumeral joint. Six freshly thawed, unembalmed cadaveric shoulders were dissected, preserving the joint capsule and gle nohumeral ligaments, the coracohumeral ligament, and the subscapularis tendon. Hall-effect strain transducers were placed on the superior, middle, and inferior gle nohumeral ligaments. The humerus and scapula were fixed in a specifically designed mounting apparatus that allowed the glenohumeral joint to be placed in 0°, 45°, or 90° of abduction. The mounting apparatus was placed in a model TTC Instron Universal Testing Instru ment, which applied an external rotation torque to the humerus. Strain produced in the three glenohumeral ligaments was recorded on a three-channel X-Y chart recorder. At 0° of abduction, the superior and middle gleno humeral ligaments developed the most strain. At 45° of abduction, the inferior and middle glenohumeral lig aments developed the most strain, with considerable strain also being developed in the superior glenohu meral ligament. At 90° of abduction, the inferior gleno humeral ligament developed the most strain, with strain also seen in the middle glenohumeral ligament.