Acromioclavicular Separation
What is it: An Acromioclavicular (AC) or "shoulder separation" is an injury to the AC joint. It can involve the AC ligament alone, or in combination with, the coracoclavicular ligament. Severe injuries may also have associated injuries to the surrounding musculature. How does it present: AC separations most often present after a fall directly onto the shoulder. Patients typically present with pain over the AC region and may have pain with ongoing activities that require range of motion of the shoulder, especially motions involving a reach across the body.
Common exam findings: On visual inspection, you may notice a prominence of the tip of the clavicle in the AC region, or swelling. On examination, you may also detect tenderness on palpation of the AC joint. The Cross Arm Test may be positive as well.
Tests and treatment: X-rays may be helpful in diagnosing and classifying AC joint injuries. A Type I injury is a partial or complete disruption to the AC ligament. Since it only involves this ligament, you usually do not see the elevation of the tip of the clavicle. You may see a widening of the space between the acromion and clavicle on x-ray. Type II injuries are regarded as injuries to both to the AC ligament and a partial tear of the coracoclavicular ligament. An elevation of the clavicle may be seen on x-ray, and this may be accentuated by doing weighted views. Type III injuries include the disruption of the AC ligaments plus a full disruption of the coracoclavicular ligament. X-rays will show an elevated distal clavicle and an increase in the coracoclavicular space (up to 100%). Type IV injuries include the injury as in Type III, but the clavicle as also posteriorly displaced. Type V injuries have the characteristics noted in Type III, but the coracoclavicular space is greater than 100% wider than normal. Type VI injuries show an inferiorly displaced distal clavicle and are rare. Type I and II injuries may be treated with rest in a sling until pain is reduced, then working on range of motion and strengthening to return to function. Type III injuries and above should be seen by an orthopedic surgeon, as most will require surgery. Some Type III injuries occasionally respond to more conservative treatment, however.