Acromio Clavicular Joint Dislocation

What is an Acromioclavicular joint injury?

Otherwise known as a shoulder separation, is a traumatic injury to the acromioclavicular (AC) joint with disruption of the acromioclavicular ligaments and/or coracoclavicular (CC) ligaments.

  • Diagnosis is made with bilateral focused shoulder radiographs to assess for AC and CC interval widening.
  • Treatment is immobilization or surgical reconstruction depending on patient activity levels, degree of separation, and degree of ligament injury.

Acromioclavicular joint injuries, commonly shortened to ACJ injuries, are characterized by damage to the acromioclavicular joint and surrounding structures. Almost invariably traumatic in etiology, they range in severity from a mild sprain to complete disruption.

Epidemiology

  • Acromioclavicular joint injuries can occur at any age but most frequently occur in the 20-40-year age group, being 5x more common in males than females. They are a common contact sports injury in young male athletes.

Clinical presentation

  • Patients can present with non-specific shoulder pain and swelling. A visible deformity is uncommon. Low-grade injuries can often be overlooked both clinically and radiologically. Pain may be provoked with the cross-body and/or O’Brien active compression test.

Treatment and prognosis

  • Treatment largely depends on the age and lifestyle of the patient as well as the type of injury. ~80% (range 70-90%) of acromioclavicular joint injuries are “low grade”. In general types I and II are treated conservatively, types IV, V, and VI are treated surgically, and type III injuries are variably treated.
  • Type I and II (+/- III): conservative management consists of ice, analgesics, and shoulder rest in a sling.
  • Type III: The current evidence does not support surgical intervention on type III injuries as a general rule. The selection of patients with type III injuries for surgical intervention is difficult, but patients who are particularly thin, require a great range of motion, or do heavy lifting may benefit from operative repair.
  • Types IV-VI (+/- III): Surgical internal fixation is typically achieved with a hook plate, which in most cases needs to be eventually removed. K-wires have also been used, although rare cases of wire migration into vital organs have dissuaded many surgeons from using them.  

Complications

Just as an injury to other joints, prior acromioclavicular dislocation predisposes the joint to osteoarthritis. Surgical complications include the migration of hardware and infection.