The anterior band of the inferior glenohumeral ligament: biomechanical properties from tensile testing in the position of apprehension.

The shoulder is the most commonly dislocated joint in the body. The primary restraint to anterior instability is the anterior band of the inferior glenohumeral ligament, where lesions are found after dislocation. The amount of surgical plication required to eliminate instability and maintain full range of shoulder motion remains unclear. We performed tensile testing with the shoulder in abduction and external rotation in 11 human, fresh-frozen, cadaveric glenohumeral joints to improve understanding of the glenoid origin of the anterior band of the inferior glenohumeral ligament and to quantify midsubstance irrecoverable elongation. After measuring the length, width, and thickness of the anterior bands with digital micrometry, biomechanical properties were obtained on bone-ligament-labrum-bone (b-l-l-b) complexes. The complexes were aligned for tensile testing with the humerus abducted 60 degrees and externally rotated. The b-l-l-b complexes were then loaded to failure at a strain rate of 100%/sec. Seven of the complexes failed at the glenoid insertion site (representing the Bankart lesion), 2 at the humeral insertion site, and 2 at the anterior band midsubstance. The ultimate load for the b-l-l-b complexes was 353+/-32 N (mean+/-SE), and tensile stress at failure of the glenoid insertion site averaged 9.6+/-2.1 MPa. When the complex failed at the glenoid insertion site, total elongation of the b-l-l-b complex was 9.1+/-0.5 mm, and the ligament midsubstance strain was 13.0%+/-1.8%. Irrecoverable elongation was only 0.8 mm when failure occurred at the glenoid insertion site. Our results indicate patients with initial anterior glenohumeral instability have small irrecoverable capsuloligamentous elongation so that meaningful plication in addition to repair of the Bankart lesion may be unnecessary.