Preoperative magnetic resonance imaging diagnosis of the floating anterior inferior glenohumeral ligament.

Approximately a century ago, labral avulsion from the glenoid was described as a source of recurrent anterior shoulder dislocation. Since then, the significance of other origins of shoulder instability has been a controversial issue. Cadaveric dissection, biomechanical evaluation, and surgical observation have led to the discovery of additional pathologic conditions associated with glenohumeral instability that must be properly identified and addressed for operative success. Recently, several authors have emphasized the importance of lesions of the glenohumeral ligament as a cause of post-traumatic shoulder instability. One such condition is bipolar avulsion of the anterior inferior glenohumeral ligament (AIGHL), or floating AIGHL. In previous reports, this finding has only been identified during surgery. We present a case of traumatic anterior shoulder dislocation in which a preoperative diagnosis of floating AIGHL was made by magnetic resonance imaging. Recognition of this rare lesion before surgical intervention is advantageous for appropriate preoperative planning and management of patients with posttraumatic anterior glenohumeral instability.