A 51 yo male presents with right shoulder pain.  He tripped off a curb and landed on his right shoulder just prior to arrival.  On exam there are no palpable deformities, but the patient has limited abduction of right shoulder and he has tenderness to palpation of anterior shoulder.  An x-ray is shown.  What's the diagnosis?  Scroll down for answer.

Answer: Acromioclavicular (AC) joint separation

• AC joint is composed of the acromion process and the clavicle and supported by the superior AC ligament (superior, inferior, anterior and posterior components) and the coracoclavicular (CC) ligament complex (the cornoid and trapazoid ligaments)
• Mechanism of injury is fall directly on shoulder or FOOSH
• AC joint injuries range from sprain of ligaments to complete rupture of all supporting ligamentsand complete separation of clabicle and acromion

       Type I: normal x-ray, sprain

       Type II (x-ray as shown above): widened AC joint, clavicle is displaced <50% due to rupture of AC ligaments

       Type III: clavicle displaced >50% due to rupture of AC and CC ligaments

       Type IV: clavicle is dislocated posteriorly

       Type V: clavicle is displaced >200% superiorly

       Type VI: clavicle is dislocated inferiorly

• Treatment with sling immobilization Types I-III, and surgical repair for Types IV-VI

References:

Bjoernsen, Lars Petter, and Alexander Ebinger.. "Shoulder and Humerus Injuries." Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8eEds. Judith E. Tintinalli, et al. New York, NY: McGraw-Hill, 2016