Acromioclavicular (Shoulder) Separation

Presentation

After a direct blow to or a fall onto the lateral shoulder with the arm adducted, the patient complains of shoulder pain increased by motion of the arm ( Fig. 95.1A ). An indirect mechanism of injury commonly involves a fall onto an outstretched arm or falling back onto an elbow ( Fig. 95.1B ). Patients are generally able to localize their pain to the acromioclavicular (AC) joint.

Inspection may reveal no deformity (type I), a small step-off between the acromion process of the scapula and the distal end of the clavicle (type II) ( Fig. 95.3 ), or significant superior displacement of the distal end of the clavicle with respect to the acromion process (type III) ( Figs. 95.2 and 95.4 ).

Signs such as swelling, abrasions, or bruising may be evident, either on the superior shoulder, implying a direct mechanism, or on the elbow or forearm, implying an indirect mechanism. The AC joint, which is superficial and easily palpated, is tender to palpation.

Patients with a type I or II AC sprain often present with pain. Patients with a type III injury may present noting a deformity, with or without pain ( Fig. 95.4 ). There is a 5-to-1 male-to-female injury rate.