Dislocation, Acromioclavicular Joint

© Reed Group

Risk: Individuals who participate in contact sports (football, soccer, rugby, hockey), cycling, or who do heavy, one-armed lifting are most at risk for this injury. Men are at greater risk than women for AC dislocations, which occur with a male-to-female ratio of about 5:1 (Prybyla).

Incidence and Prevalence: In the general population, AC dislocations are most common during the third decade of life. Among athletes, AC separations occur most often between ages 10 and 20 (Malone). Incomplete injuries to the AC joint are 2 to 3 times more common than complete dislocations. AC dislocations account for approximately 12% of all shoulder dislocations (Malone).

History: A thorough history will help establish the mechanism of injury and rule out other processes. In older individuals, it is important to distinguish AC separation from rotator cuff injuries, impingement syndrome (adhesive capsulitis), and glenohumeral arthritis. Individuals usually report a direct blow to the lateral shoulder area, either from a fall (e.g., landing on the side of the shoulder in a football tackle), or from a push or stumble (e.g., being checked into a wall when playing hockey). Individuals complain of pain, tenderness, swelling on the top of the shoulder, and decreased shoulder range-of-motion. Pain may be worse at night, particularly when rolling onto the injured shoulder. Athletes who do weight training may report difficulty with a specific exercise.

Physical exam: Observation may reveal asymmetry of the two shoulders with a noticeable deformity on the affected side. Deformity is most obvious with a Grade III injury or with a clavicle fracture. Loss of the normal shoulder contour and prominence of the clavicle can be accentuated in Grade I and II injuries by having the individual hold a 10 to 15 pound weight in the hand of the affected side. There may be an abrasion on the shoulder as well as swelling and bruising (ecchymosis) at the site of the injury. The individual may hold the arm across the chest and apply upward pressure to the elbow.

Gentle examination of the AC joint with the fingers (palpation) may reveal tenderness. There is limited active range of motion and painful assisted (passive) range of motion of the shoulder. The cross-body (or crossover) adduction test is the most reliable physical exam technique for AC joint pathology. In grade III injuries, the high riding end of the clavicle may be rocked front to back (anterior-posterior) if examined shortly after the injury. Pain can be elicited over the coracoclavicular space. In grades IV through VI, the end of the clavicle may be depressed, aimed behind (posterior), above (superior), or below (inferior) the normal position. Comparison to the opposite shoulder is important when determining position. The nerves to the arm and circulation to the extremity should be examined by testing reflexes, sensation, pulses, and capillary filling time.

Tests: X-rays of the AC joint help confirm the diagnosis. Stress radiographs may be used to assess degree of instability and distinguish Grade III separations. The individual holds a weight in the hand on the affected side to show the joint separation more clearly on x-ray (stress radiograph). In rare situations, a CT or MRI may be needed to evaluate injury to soft tissues surrounding the shoulder. A nerve conduction study (NCV) and electromyogram (EMG) study may be used to assess nerve damage.

Rehabilitation of acromioclavicular joint dislocation depends greatly on the severity of injury. The treatment of a minor acromioclavicular separation may consist of a sling for comfort for several days. Even if the acromioclavicular joint is not to be exercised, it becomes important to exercise the fingers, hands, and elbows to prevent stiffness. Once the initial pain and swelling subside, the rehabilitation process may warrant the observation and guidance of a physical therapist or occupational therapist until the individual progresses to an independent exercise program. The individual may be instructed in a home exercise program to continue daily in conjunction with supervised treatment. The progression of all exercise is based on the healing of the involved soft tissue.

The use of modalities such heat and cold can help in the control of pain and inflammation (Salter). Rehabilitation of an acromioclavicular dislocation begins with range of motion exercises to the shoulder in all pain-free movements. Individuals may progress to strengthening exercises, using pain as a guide, avoiding motions that may compromise the integrity of the joint (Buss). Care should be taken to strengthen all muscles surrounding the shoulder.

Heavy weight lifting activities should be avoided for approximately 8 to 12 weeks, until the ligaments heal. At this point, the strengthening program advances, as tolerated.

The therapist may need to modify the exercise program for individuals with arthritis or other joint irritations. If the acromioclavicular dislocation requires surgical repair, some restrictions may be placed on the progression of the range of motion and strengthening in certain movements. This varies depending on the degree of dislocation or type of surgery performed (Woodward).

Additional information may provide greater insight into the rehabilitation needs of these individuals (Clarke; Rockwood).