What is an AC joint separation (Shoulder Separation)?

An AC joint separation occurs when the ligaments that stabilize the clavicle to the acromion process are injured or torn. As a result the clavicle can be displaced (moved) upwards. This condition is commonly known as a shoulder separation.

There are different severities of AC joint separation. Classification of the different severities depends on the ligaments that are torn. One classification is as follows:

Type I: A sprain (without a complete tear) of either of the ligaments holding the joint together. The clavicle is not displaced.

Type II: A complete tear of the acromioclavicular ligament and a partial tear of the coracoclavicular ligaments. The clavicle is slightly displaced.

Type III: A complete tear of both the acromioclavicular ligament and the coracoclavicular ligaments. When this occurs the clavicle is severely displaced (dislocated).

Types IV, V, VI: A complete tear of the acromioclavicular ligament and the coracoclavicular ligaments. The clavicle is severely dislocated and usually requires surgical intervention.

What can cause an AC joint separation?

Injuries to the AC joint are usually caused by a direct blow to the shoulder. Traumatic contact from the side or from above the shoulder can tear the AC ligaments. Hockey players and football players commonly injure this joint when they make contact with the boards, ground or an opponent with their shoulder striking first.

Injuries to the AC joint can also be caused by overstressing the joint with heavy weightlifting (i.e. deep bench-press techniques). This mechanism of injury is rare.

What does an AC joint separation feel like (Signs and Symptoms)?

Immediately following an AC joint separation there is usually pain and swelling on the top of the shoulder. Depending on the severity of the injury, there may be some visible displacement of the clavicle. An obvious upward pointing lump on the top of the shoulder is seen in more serious separations. This is the end of the displaced collarbone (the clavicle bone) and it moves up if the affected arm is pulled toward the ground.

Activities such as pushing and pulling, reaching overhead and across the body will usually create pain in an acutely (recently) separated AC joint. Tenderness is felt at the junction, or joint, between the collarbone and shoulder. This is the site of the AC (acromioclavicular) joint. Over time (usually 6 - 8 weeks or more) there may be little pain associated with an AC joint separation. If nerve damage occurs, numbness or muscle weakness may be present in the shoulder or affected arm. If you have this symptom, seek immediate medical attention.

What is the treatment for an AC joint separation?

The treatment of AC joint separations depends on the severity of the injury.

Treatment immediately following Type I and Type II AC joint separations may include an arm sling, icing, taping, pain medications and rest. As the symptoms improve a range of motion and strengthening program, as recommended by a physician and/or physical therapist, may begin. Individuals returning to sport can benefit from padding (a doughnut pad) over the AC joint to help protect the joint.

Type IV, V, and VI shoulder separations almost always require surgery, but these are very uncommon injuries. The difficult decisions arise with patients with a type III shoulder separation. There is controversy among orthopedic surgeons as to how to best manage patients with a type III shoulder separation. In the end, there is no 'right answer,' but there are some factors to consider when making this decision.

• Non-surgical treatment for type III shoulder separations - Most evidence suggests that patients with type III shoulder separations do just as well without surgery, and avoid the potential risks of surgical treatment. These patients return to sports and work faster than patients who have surgery for this type of injury.

• Surgery for type III shoulder separations - Recent studies have suggested that some athletes and heavy laborers may benefit from early surgical treatment of type III shoulder separations. These include athletes who participate in sports that require overhead throwing such as baseball. The potential benefit of early surgical treatment for type III shoulder separations remains unproven.

Treatment following a Type III, IV, V and VI AC joint separation is more involved. In some cases surgery may be required to re-locate the clavicle. In other cases a non-operative approach may be chosen.

Is a shoulder separation the same as a shoulder dislocation? 
No! These two injuries are commonly confused, but they are very different conditions. As described above, the shoulder joint is located at the junction of three different bones: the clavicle, the scapula, and the humerus. In a shoulder separation, the junction of the clavicle and scapula is disrupted. In a shoulder dislocation, the humerus (arm bone) is displaced from the socket. Not only are the injuries different in anatomic terms, but the implications for treatment, recovery, and complications are also different.