From: Dr Ryan Chau

There is a disruption to the acromioclavicular joint.
Grade 1 injuries are due to stretching of the ligaments only with no radiological abnormality. In Grade 2 injuries there is subluxation of the joint and tear in the acromio-clavicular(AC) ligament in. There is complete dislocation of the joint in Grade 3 injuries with tears in both the AC and coraco-clavicular(CC) ligaments

What injury is shown here?
How is this classified?

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(See below for further details)

The superior and inferior borders of the distal clavicle should be in alignment with the corresponding borders of the acromion. In this film there is a dislocation of the joint with the inferior border of the clavicle aligning with the superior border of the acromion, suggesting a Grade 3 injury.

The stability of the acromio-clavicular joint is dependent upon the ligaments that surround it. Horizontal stability is provided by the four AC ligaments (anterior, posterior, superior, and inferior), with the superior ligament being the strongest. Vertical stability is provided by the CC ligament, which comprises of the conoid and trapezoid ligaments.

Treatment revolves round symptom control, including analgesia and broad arm sling support. Further treatment is rarely needed though internal fixation may be of benefit in extreme cases.