Perthes Lesion

In the setting of anterior dislocation of the shoulder, Bankart lesions are the hallmark imaging feature. Non-osseous Barnkart lesions are characterized by

1. Anterior-inferior labral tear

2. Capsular injury in the area where the anterior-inferior glenohumeral ligament originates

3. Periosteal avulsion and tearing.

In some cases, these criteria are not fulfilled; instead, either one of the components is absent, or there are additional traits with potential clinical significance. Hence, an array of variants have been described, and acronyms or initialisms used as mnemonics: the alphabet soup of labral pathology. Perthes, ALPSA, GLOM are among these Bankart variants. GLAD lesions - in which a chondral lesion is present in the anterior inferior glenoid - is sometimes lumped into the same category. However, the etiology of GLAD lesions differs in that it is usually the result of a direct shear injury after a fall on the outstretched hand.

The difference between an ALPSA and a Perthes lesion pivots around the presence of retraction of the torn labrum medially and inferiorly in ALPSA lesions, whereas the labrum stays in situ in Perthes lesions. Common to these two lesions is the presence of a tear through the base of the labrum visualized as contrast undercutting the anterior-inferior labrum; as well as the identification of a detached, but intrinsically intact periosteum, which remains attached to the labrum.


Direct MRAr. though the five o'clock area appears falsely reassuring, and the labral tear is not clearly identified.	On the same patient, the ABER sequence is able to bring out contrast material undercutting the base of the labrum, and insinuating under the periosteum. However, there is no breach in the periosteum.

An associated SLAP lesion is also visualized as a sequela of the anterior dislocation.	Notice the the Hill-Sachs deformity in the humeral head from the anterior dislocation.