Acromioclavicular (AC) joint injuries are frequently diagnosed following an acute shoulder injury. Approximately 9% of shoulder girdle injuries involve various damages of AC joint. These injuries occur commonly in active young adults with a direct fall onto the top of the shoulder while the arm is adducted, or with a direct blow over the shoulder.
For the classification of ACJ dislocations, Rockwood and Green classification is used mainly. But lately, there is a subdivision of type III injuries suggested by the ISAKOS Terminology Project because of the unpredictability of treatment results.Patients commonly complain of pain around the anterosuperior part of the AC joint after a trauma. Physical examination must consist inspection of both shoulders; a simple comparative inspection may lead to diagnosis. In types I and II; some swelling, dermabrasion, and bruising can be visualized, and in other types a prominent clavicle is generally obvious.