Acromioclavicular (AC) Joint Separation

An acromioclavicular (AC) joint separation is the formal name for a separation of the collar bone from the shoulder blade. The collar bone (clavicle) and the shoulder blade (scapula) together form the socket that holds the ball of the upper arm bone.

An AC joint separation is most typically caused by falling or being hit on the point of the shoulder blade or an outstretched arm. It can happen from a fall on ice, playing a contact sport such as football or falling over the handlebars of a bike.

  • Biochemical or hormone imbalances
  • Changes in the immune system
  • Diabetes. People with diabetes have a three times greater chance of developing frozen shoulder than the general population
  • Immobilization for long time
  • Injury to the shoulder
  • Previous surgery

Symptoms of Acromioclavicular Joint Separation

The dislocation of the joint makes the shoulder unstable and painful. The pain is particularly bad when trying to make overhead movements or to sleep on the affected side. There may be some bruising.

Depending on how severe the joint separation is, there may also be swelling. The collar bone may move when pressed. There may be a bump or deformity on top of the shoulder. The injured person may instinctively support his or her elbow and hold the arm in close to the body. There may be a popping sound when the joint moves.

Diagnosing an Acromioclavicular Joint Separation

A doctor typically takes a medical history and do a physical examination. An X-ray will show the separated joint. An X-ray will help the doctor decide if it is a joint dislocation or a broken bone.

The doctor may also do some tests to evaluate the patient's range of motion and to identify specific areas of pain and weakness.

The shoulder joint is surrounded by ligaments, tendons and muscles that hold the bones of the shoulder joint in place and stable. During an injury, these soft tissues may get torn.

Because there can be varying amount of damage in the process of an AC joint separation, these injuries are given ratings. There a total of six grades. The most common are:

  • Grade 1 AC joint separation is a slight displacement of the joint. The AC ligament may be badly stretched or partly torn.
  • Grade 2 AC joint separation involves a partial dislocation of the joint. This may not be easy to see. The AC ligament is completely torn. The nearby coracoclavicular ligaments are not, however.
  • Grade 3 AC joint separation is a complete separation of the joint, which is clear to see. Both sets of ligaments are torn as well as the capsule that surrounds the joint. Because there's no support to the joint left, the shoulder falls with the weight of the arm. The shoulder blade is pushed up making a bump on the shoulder.

Treating Acromioclavicular Joint Separation

Most AC joint injuries don't need surgery. Depending on the nature of the injury, a person may recover anywhere from a few days to 12 weeks after the injury. In some situations, however, surgery is essential.

Conservative Medical Treatment

People with Grade 1 and 2 AC joint separations and most people with Grade 3 separations will be started on conservative medical treatment. This includes ice to reduce pain and swelling, rest and keeping the arm in a sling for up to two weeks. Nonsteroidal anti-inflammatory drugs may be helpful for reducing pain and swelling. Physical therapy or a rehabilitation program will begin as soon as healing permits.

Surgery to Treat Acromioclavicular Joint Separation

Anyone who has a Grade 4 through 6 separation and some people with Grade 3 separations mostly likely will need surgery. Surgery is also an option if conservative medical care doesn't bring significant improvement.

Several techniques for treating an AC joint separation with surgery exist. Most of them involve reconstructing the ligaments. Pins or plates may be used to improve stability.

After surgery, the patient will need to wear a sling for about four weeks. (If the surgery has to be done using traditional, open techniques instead of minimally invasive, the patient may have to keep the arm immobilized for two to three weeks after surgery.

As soon as healing permits, lower arm exercises can be started. Actions like lifting or reaching above waist level may be prohibited for a time after surgery. Six to eight weeks of physical therapy may also be needed to regain full motion. People who enjoy activities that involve shoulder strength or speed may not be able to do these things for up to six months.