Glenoid avulsion of the glenohumeral ligament (GAGL): a case report and review of the anatomy

Shoulder dislocations are frequently seen in the general population and can be a cause of instability. Instability can lead to debilitating symptoms and morbidity as a result of progressive damage to the shoulder. Anterior shoulder dislocations are the most frequent type of dislocations and have been studied extensively with MRI. The soft tissue Bankart lesion is the most well-known entity associated with anterior instability; however, additional structural lesions arising from traumatic events have been described in recent literature which also predispose to anterior shoulder instability. One of these lesions, the glenoid avulsion of the glenohumeral ligament (GAGL), involves avulsion of the inferior glenohumeral ligament from the glenoid and involves separation from an intact labrum. In contrast to the Bankart lesion, there has been limited discussion of the GAGL lesion in the literature and very few imaging examples. We report a case of a GAGL diagnosed on MRI and confirmed with arthroscopy. It is discussed in the context of the anatomy of the inferior glenohumeral ligament and the imaging findings.