STATIC CAPSULOLIGAMENTOUS RESTRAINTS TO SUPERIOR-INFERIOR TRANSLATION OF THE GLENOHUMERAL JOINT

The purpose of this study was to determine the contributions of specific capsuloligamentous structures to restraining superior-inferior translation of the glenohumeral joint. Eleven cadaveric shoulders were tested using a four degrees-of-freedom test apparatus. The humerus was free to translate in three planes and free to flex and extend when a superior and inferior force of 50 N was applied. Testing was performed in three positions of abduction (0-degrees, 45-degrees, and 90-degrees) and three positions of rotation (neutral, maximum internal, and external). Shoulders were tested intact, vented, and after division of specific capsuloligamentous structures. The primary restraint to inferior translation of the adducted shoulder was the superior glenohumeral ligament. The coracohumeral ligament appeared to have no significant suspensory role. With progressive abduction, the anterior and posterior portions of the glenohumeral ligament become the main static stabilizers resisting inferior translation: the anterior portion was the primary capsular restraint at 45-degrees of abduction, while the posterior portion was the primary restraint at 90-degrees of abduction, neutral rotation. Our results indicate that clinical assessment of glenohumeral translation in the superior-inferior plane should be performed in multiple positions of abduction and rotation.