TENSILE PROPERTIES OF THE INFERIOR GLENOHUMERAL LIGAMENT

The tensile properties of the inferior glenohumeral ligament have been determined in 16 freshly frozen cadaver shoulders. The inferior glenohumeral ligament was divided into three anatomical regions: a superior band, an anterior axillary pouch, and a posterior axillary pouch. This yielded 48 bone-ligament-bone specimens, which were tested to failure in uniaxial tension. The superior band was consistently the thickest region, averaging 2.79 mm. The thickness of the inferior glenohumeral ligament decreased from antero-superiorly to postero-inferiorly. The resting length of all three anatomical regions was not statistically different. Total specimen strain to failure for all bone-ligament-bone specimens averaged 27%. Variations occurred between the three regions, with the anterior pouch specimens failing at a higher strain (34%) than those from the superior band (24%) or the posterior pouch (23%). Strain to failure for the ligament midsubstance (11%) was found to be significantly less than that for the entire specimen (27%). Thus, larger strain must occur near the insertion sites of the inferior glenohumeral ligament. Stress at failure was found to be nearly identical for the three regions of the ligament, averaging 5.5 MPa. These values are lower than those reported for other soft tissues, such as the anterior cruciate ligament and patellar tendon. The anterior pouch was found to be less stiff than the other two regions, perhaps suggesting that it is composed of more highly crimped collagen fibers. Three failure sites were seen for the inferior glenohumeral ligament: the glenoid insertion (40%), the ligament substance (35%), and the humeral insertion (25%). In addition, significant capsular stretching occurred before failure, regardless of the failure mode.