The acromioclavicular joint.
Acute injuries of the AC joint have a limited differential diagnosis. A thorough examination and appropriate radiographs can identify nearly all problems while ruling out tumors as a causal factor. AC injury frequently occurs with other fractures, dislocations, or soft tissue injury around the shoulder. The single unifying diagnosis one searches for in medical conditions is frequently absent in musculoskeletal injury. For effective management of AC separations, the primary care physician need only distinguish type I, II, and III injuries from surgically treated type IV, V, and VI injuries. Types I, II, and III injuries should be treated with pain control and progressive rehabilitation as described previously. Patients who have types IV, V, and VI injuries should be referred to an orthopedic surgeon. Chronic injuries of the AC joint are also clearly diagnosed by appropriate physical examination and radiographs. Steroid injections can aid in the diagnosis and management of these conditions. Injury to one shoulder component predisposes to other shoulder injuries. A thorough examination will reveal these other associated abnormalities that may not be part of the presenting complaint. With practice in the examination of the shoulder and intra-articular injections, the primary care physician can effectively treat most common AC conditions. Only after conservative measures fail is it necessary to refer the patient for surgical management.