THE ROLE OF THE ACROMIOCLAVICULAR LIGAMENTS AND THE EFFECT OF DISTAL CLAVICLE RESECTION

To determine the role of the acromioclavicular ligaments in controllin g scapular rotation about the distal clavicle and the effects of dista l clavicle resection, we used 13 fresh shoulders consisting of the cla vicle, acromioclavicular ligaments, coracoclavicular ligaments, and sc apula. The range of motion was measured using a specially designed gon iometer for each of the three orthogonal axes of rotation of the scapu la with reference to the clavicle: anterior-posterior axial rotation, protraction-retraction, and abduction-adduction. We did two experiment s involving sequential sectioning. Range of motion was measured in the intact shoulder and after each sectioning cut. The order of sectionin g in Experiment 1 (six shoulders) was 1) the inferior acromioclavicula r ligament, 2) removal of 5 mm of the distal clavicle, and 3) the supe rior acromioclavicular ligament. In Experiment 2 (seven shoulders) the order was 1) the superior acromioclavicular ligament, 2) removal of 5 mm of the distal clavicle, and 3) the inferior acromioclavicular liga ment. The most important results were 1) only 5 mm of the distal clavi cle needs to be resected to ensure that no bone-to-bone contact occurs in rotation postoperatively and 2) there was no difference in the end result (for range of motion in any of the three axes) whether the inf erior acromioclavicular ligament or the superior acromioclavicular lig ament was cut before removal of 5 mm of the distal clavicle.