What is the AC Joint in the shoulder?

The top of the wing bone or scapula is the acromion. The joint formed where the acromion connects to the collar bone or clavicle is the AC joint. Usually there is a protuberance or bump in this area, which can be quite large in some people. This joint, like most joints in the body, has a cartilage disk or meniscus inside and the ends of the bones are covered with cartilage. The joint is held together by a capsule, and the clavicle is held in the proper position by two heavy ligaments called coracoclavicular ligaments.

How is the AC Joint injured?

The AC joint is injured most often when one falls directly on the point of the shoulder. The trauma will separate the acromion away from the clavicle, causing a sprain or a true AC joint dislocation. In a mild injury, the ligaments which supports the AC joint are simply stretched (Grade I), but with more severe injury, the ligaments can partially tear (Grade II) or completely tear (Grade III). In the most severe injury, the end of the clavicle protrudes beneath the skin and is visible as a prominent bump.

How is an AC joint separation diagnosed?

Most often patients will have tenderness or bruising around the top of the shoulder near the AC joint, and the suspected diagnosis can be confirmed using an x-ray, which compares the injured side with the patient's other uninjured AC joint.

What is the treatment for a sprained AC joint?

When a joint is first sprained, conservative treatment is best. Applying ice directly to the point of the shoulder is helpful to inhibit swelling and relieve pain. The are can be supported with a sling which also relieves some of the weight from the shoulder.

Gentle motion of the arm can be allowed to prevent stiffness, and we encourage use of the elbow, wrist, and hand. However, any attempt at more vigorous shoulder mobilization early on will probably lead to more swelling and pain.

How long does it take for a shoulder separation to heal?

Depending on how severe the injury is, it may heal adequately in two to three weeks. In severe cases, the shoulder may not heal without surgery.

When and why is surgery necessary for AC joint separation?

Usually surgery is reserved for those cases where there is residual pain or unacceptable deformity in the joint after several months of conservative treatment. The pain can occur with direct pressure on the joint, such as with straps for underwear or work clothing. Sometimes there will be catching, clicking, or pain with overhead activities. Finally, in some people with very thin and very little muscular and soft tissue padding above their shoulders, in the prominent clavicle after the separation may be considered unattractive since the shoulder can appear to be unbalanced.

Are there other causes of AC joint pain and disability?

Arthritis can occur as an isolated events in the AC joint, causing stiffness, aching, and sometimes swelling. Another condition called distal clavicle osteolysis (DCO) gives a similar clinical picture, usually in young people who lift heavy weights. This is called "Weightlifter's Shoulder." Sometimes a bone scan or MRI scan is necessary to demonstrate the inflammation that is present in the end of the clavicle.

What type of surgery can repair AC joint problems?

The simplest type of surgery for AC joint injury involves resection or removal of the end of the clavicle using arthroscopic techniques (called a Mumford procedure). If the joint becomes painful because of DCO (weightlifter's shoulder) or arthritis, or the separation is only minor, this technique can give very good results. When the joint is severely displaced or separated a more complex procedure is needed to restore the position of the clavicle. Usually this operation, called a Weaver-Dunn procedure, is done using a two inch incision over the joint. The end of the clavicle is removed, and a ligament is transferred from the underside of the acromion to the top of the clavicle to replace the ligaments torn during dislocation. The initial portion of this procedure is an arthroscopic evaluation of the shoulder joint to confirm that there is no other injury to the shoulder. The ligament that will be transferred to the top of the clavicle is then harvested using arthroscopic techniques from the undersurface of the acromion. The arthroscopic portion of the surgery is video recorded both for the medical record and for patient education. Patients are encouraged to look at their videotapes so they better understand their surgery.

What is the postoperative treatment and rehabilitation?

Postoperatively, treatment depends on the type of surgery performed. Usually, when the Mumford procedure is performed using arthroscopic techniques, the arm is treated with an arm sling.

Bathing is allowed in three days, and elbow, wrist, and hand motion are begun immediately. Lifting is limited for three weeks, but following that, progressive exercise and range motion activities proceed as the symptoms allow. There can be some mild soreness over the top of the shoulder for up to three months after an arthroscopic Mumford procedure.

When a Weaver-Dunn procedure (rebuilding the torn ligaments) is needed, approximately two or three weeks is added to the immobilization time before motion exercises are started. This extra time allows the ligament to heal. Otherwise, the exercise program is the same as that for the Mumford procedure described above.

Who can I call for more information?

Please feel free to contact us and ask one of our physicians for a referral. We will be happy to answer your questions and evaluate your shoulder in the Clinic.

Don Buford, M.D. © 2010