This 15-year-old male has alleged recurrent dislocation in his right shoulder after a slip and fall in the shower five months earlier. The joint is dry. There is no effusion. No substantive Hill-Sachs or bone lesion is identified.
Q1 – Which of the following diagnosis options is the most likely:
(c) Abnormal glenoid avulsion of the glenohumeral ligament (GAGL)
(d) Abnormal anterior inferior glenohumeral ligament (AIGL)
(e) Abnormal humeral avulsion of the glenohumeral ligament (HAGL)
A1 – (b) “abnormal”
This is a flap tear of the inferior labrum. The labrum and inferior glenohumeral ligament are separated from the bony glenoid and its cortex by a thin hyperintense sliver (green arrows). The findings are illustrated both on the T1 image (image 1) and the T2 image (image 2). In no way should a fold in the inferoaxillary labral ligamentous complex exit the medial surface of this complex. That has occurred here, and we refer to this as a “medial exit sign” (green arrow). For this reason, the option of (a) “normal” is an incorrect choice.
A glenoid avulsion of the glenohumeral ligament (GAGL) leaves the labrum behind attached to the glenoid cup, and is usually a severe injury. In other words, the ligament separates from the labrum, and that has not occurred here.
An anterior inferior glenohumeral ligament (AIGL) detachment occurs when both the humeral end of the inferior glenohumeral ligament and the glenoid end of the glenohumeral ligament detach. This is also known as the floating inferior glenohumeral ligament. This is a major injury associated with capsular disruption, effusion, edema and a floppy corrugated ligament. No such supportive findings are present.
If this were a humeral avulsion of the glenohumeral ligament (HAGL), then you would be shown a floppy ligament that is separated from the humeral neck where it detaches (image 2, pink arrow). If a small fragment of bone is detached with it, this is known as a B-HAGL, often affectionately referred to as a “bagel.” Another variant of this injury is the reversed HAGL (R-HAGL) in which the detachment from the humeral neck is only posterior.
In summary, this patient has a flap tear of the labrum and ligamentous complex in the axillary region separating it from the glenoid, which explains the patient’s recurrent instability.
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