Acromioclavicular Joint Separation (AC Dislocation)

Anatomy/Pathophysiology

A “shoulder separation” is a fairly common injury, especially in an athletic population. A shoulder separation is actually a dislocation of the acromioclavicular joint, the joint between the scapula and the clavicle. The AC joint can be injured in varying degrees. The simplest type injury is a simple sprain of the ligaments around the joint (grade 1). A more severe injury can result when the ligaments around the joint are actually torn (grade 2). If the ligaments around the joint are torn and the ligaments that attach the clavicle to the coracoid process, the injury results in a obvious bump on the shoulder (grade 3).

Symptoms

The symptoms may range from simply tenderness over the joint, to the deformity as seen in the grade 3 separation. There may be a considerable amount of swelling if the separation is grade 2-3. A bluish discoloration of the skin due to bruising may occur several days after the injury. In the grade three separation you may feel a “popping” sensation due to the loose joint shifting.

Diagnosis

shoulder-xrayDiagnosis is usually made on physical examination. Xrays may show the AC joint to be dislocated, and may be necessary to rule out a fracture of the clavicle. In some cases, xrays are taken while holding a weight in each hand to stress the joint and determine how much instability is present.

Treatment

Treatment for a Grade 1 or Grade 2 shoulder separation usually consists of a sling and pain medication until the sprain, or tearing, of the ligaments heals. In most cases, the shoulder becomes relatively pain free within 3 weeks. Since there is not a danger of making the condition worse, activity can be determined by the symptoms. You can usually do whatever you can tolerate.

The treatment of Grade 3 AC separations is somewhat controversial. Many studies show no difference in the outcomes for surgically treated separations versus doing nothing. A significant portion of people who undergo surgery will need another operation later as the injury causes the joint to degenerate and become painful. Other physicians feel that some patients benefit from surgical repair. One case where repairing the ligaments may be best is in the case of the highly functioning throwing athlete. Some would argue that these athletes perform better following repair than without the repair.

In some grade 3 shoulder separations, surgery may be suggested. Surgery involves relocating the joint and repairing the torn ligaments. A screw, or some other fixation may be used to hold the joint reduced while the ligaments heal.

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