Got your diagnosis? Good. Now look at the following image- taken a few weeks before the ultrasound above

There are all kinds of Bankart variations. Here's what a GLOM (glenolabral ovoid mass) looks like. It's the displaced anterior labrum which has balled up unto itself. Note Hill Sachs lesion. (scanned on the 3T Siemens Verio)

Coronal and sagittal T2-weighted fat sat images of the shoulder reveal fluid collection tracking from the posterosuperior paralabral location, into the spinoglenoid notch and anterior to the supraspinatus muscle. This is a paralabral cyst (not to be mistaken for intramuscular cyst from tendon delamination). Site of origin is likely from a tear of the posterosuperior labrum (see axial proton density image below).

Axial proton density image of the shoulder through posterosuperior labrum shows relative increased signal and loss of normal triangular morphology of the labrum in this location. The fluid collection can be seen tracking posterior to the labrum. No rotator cuff atrophy nor oedema was present in this case.

Drs Kassarjian, Torriani, Ouellette and Palmer at MGH published a review of intramuscular cysts (available here).

A surgical discussion of spinoglenoid notch cysts causing suprascapular entrapment was published by Singaporean orthopaedic surgeons (available here pdf file ).

Radiologists can aspirate these cysts with ultrasound guidance (see abstract below)- but it's important to have prior imaging as dilated veins can also cause suprascapular nerve entrapment.

J Bone Joint Surg Am. 2008 Mar;90(3):523-30.

Treatment of labral tears with associated spinoglenoid cysts without cyst
decompression.

Schroder CP, Skare O, Stiris M, Gjengedal E, Uppheim G, Brox JI.

BACKGROUND: The treatment of symptomatic spinoglenoid cysts has varied from
observation, needle aspiration, and open excision to arthroscopic decompression.
The purpose of the present study was to prospectively assess whether labral
repair alone would lead to cyst resolution and pain relief.

METHODS: Forty-two patients with a posterosuperior labral tear and a ganglion cyst at the spinoglenoid notch were treated with arthroscopic débridement of the glenoid rim and labral repair, either with a resorbable tack or a suture anchor. Patients ranged in age from twenty-three to sixty-eight years. Seven patients had clinical and/or radiographic evidence of atrophy of the infraspinatus muscle; one had atrophy of both the infraspinatus and the teres minor muscles, while two had atrophy of the teres minor muscle. All patients had postoperative magnetic resonance imaging performed twice, at an average of fifteen months and again at
an average of forty-three months postoperatively. The clinical outcome, including the Rowe score, was assessed for all patients at a median of forty-three months postoperatively.

RESULTS: In thirty-seven (88%) of the forty-two patients, the
cysts had resolved completely. In five patients, a cyst was still present but
with a clear reduction in size. These five patients had remission of pain and were satisfied with the shoulder function. Three patients with preoperative muscular atrophy without fatty infiltration regained normal appearing muscle, while the seven with preoperative fatty changes continued to demonstrate those changes postoperatively. The median Rowe score improved from 61.5 points preoperatively to 98.0 points at the time of follow-up. Thirty-one patients assessed the result of treatment as excellent; nine, as good; and two, as fair.

CONCLUSIONS: Most spinoglenoid cysts resolve, and patient satisfaction can be expected to be high after labral fixation without cyst decompression.