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Separation of the Acromioclavicular Joint

Separation of the acromioclavicular joint is a relatively common injury in contact sports, riding, cycling, skiing, and wrestling. The joint is surrounded by ligaments running between the clavicle and the acromion
process of the scapula (the acromioclavicular ligament), and is further stabilized by other ligaments running between the clavicle and the coracoid process of the scapula (the coracoclavicular ligaments). The joint sometimes contains a cartilaginous meniscus or disk.

The vast majority of acromioclavicular injuries are due to direct force produced by the athlete falling on the point of the shoulder with the arm in the adducted position (close to the body) or when an ice-hockey
player is tackled against the board. Force is transferred up the arm through the humeral head and the acromion process. Acromioclavicular joint injuries occur less commonly as a result of indirect force, for
instance when the athlete falls on an outstretched arm.


These injuries may be classified according to the extent of ligamentous disruption to the acromioclavicular joint and coracoclavicular ligaments.
The most common injury types in athletes are grades I–III; grades IV–VI are very rare. They can be characterized as follows:
– Grade I: a sprain of the acromioclavicular ligament, causing pain over the acromioclavicular joint and minimal pain with shoulder motion. There is mild tenderness.
– Grade II: disruption and widening of the acromioclavicular joint with some elevation of the distal end of the clavicle. There is moderate to severe pain near the acromioclavicular joint and shoulder motion is
restricted. The athlete will usually withdraw from competition.
– Grade III: disruption and dislocation of the acromioclavicular joint with superior displacement of the clavicle. The coracoclavicular ligaments are disrupted and the coracoclavicular space is greater than in the normal shoulder. The upper extremity is seen to be depressed and the clavicle can be free-floating, possibly lifting the skin. Moderate to severe pain is present. There is tenderness over the joint. The
athlete is usually unable to continue sports. The lateral end of the clavicle is reducible.
– Grade IV: the acromioclavicular joint is dislocated, with the clavicle displacing posteriorly into or through the trapezius muscle. The coracoclavicular ligaments are completely disrupted. The clinical
findings are similar to type III injury, except that more pain is usually present and the clavicle is dislocated posteriorly and not reducible.
– Grade V: disruption of the acromioclavicular ligament as well as the coracoclavicular ligaments. The acromioclavicular joint is displaced with gross disparity between the clavicle and the scapula. The clinical findings are similar to type III, but there is more pain and displacement between the distal clavicle and acromion. The skin may be tented so much that there is a threat it will be penetrated. This injury is rarely seen in athletes.
– Grade VI: The acromioclavicular and coracoclavicular ligaments are disrupted and the joint is dislocated with the clavicle being displaced inferior to the acromion or the coracoid. The shoulder has a flatter
appearance superiorly. This injury is rare in athletes owing to the great trauma necessary to produce the subcoracoid dislocation. There is a high incidence of associated fractures.

Symptoms and diagnosis

A complete history will often secure the diagnosis.
– Pain is localized to the anterior superior aspect of the shoulder. The pain does not radiate and the severity is often proportionate to the degree of injury.
– Physical examination shows swelling, abrasion, skin color changes (ecchymoses), and sometimes deformity of the joint. The involved arm is usually held at the side and all shoulder motions are restricted
because of pain.
– There is localized tenderness over the joint.
– Passive adduction at shoulder level is often painful.
– Injection of local anesthetic solution may relieve pain.
– Depending on the degree of separation, the lateral end of the distal clavicle may be displaced upward. A partial separation (grade I and II) involves tearing of the acromioclavicular capsule and ligaments, and a
complete separation (grade III) will also have a complete tear of the coracoclavicular ligament.
– The diagnosis is confirmed by X-ray, which is more likely to reveal the abnormality if it is carried out with the joint loaded. In grade III separation, there is no contact between the articular surfaces.


The doctor may:
– prescribe early mobility exercises, especially in grade I-III injuries;
– use a bandage to reduce the clavicle back into position. The results of this technique are limited;
– recommend surgery in grade IV–VI lesions. The treatment of grade III injuries remains controversial, but there is a definite trend toward nonoperative management with early mobilization. A surgical approach should be considered in young athletes (15–25 years) in sports with overhead activities. With nonoperative management the athlete may have a residual displacement but the end result and function are largely the same. In most cases, therefore, early symptomatic treatment is recommended with progression to resistance exercises as soon as tolerated. The athlete can return to sports when there is pain-free range of motion, which usually occurs in 4–8 weeks.

Healing and complications

In grade I and II injuries degenerative changes and arthritis occur in the joint in 8–9% of cases. If this injury continues to cause pain, an excision of 1 cm (0.4 in) of the distal end of the clavicle is indicated. This usually results in early pain-free return to sports. If there is residual pain or disability interfering with performance after a grade III injury, an excision of the distal clavicle may be indicated, with restoration of the coracoclavicular ligaments. Return to sports is usually possible within 2–3 months.

Chronic acromioclavicular joint injury

Persistent pain after acromioclavicular joint injury may necessitate surgery, which includes removal of the lateral end of the clavicular bone.

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