KidsMD Health Topics

AC Joint Injuries

  • Overview

    The AC (acromioclavicular) joint is a joint in the shoulder where the collarbone (clavicle) meets the shoulder blade (scapula). The specific part of the scapula, adjacent to the clavicle, is called the acromion, hence the name AC joint.

    The most common problems that occur at the AC joint are:

    • fractures
    • separations
    • arthritis

    How Boston Children's Hospital approaches AC joint injuries

    Depending on the severity of your child's AC joint injury, treatment may be surgical or non-surgical. At Children's, doctors are committed to repairing your child's AC joint in the least invasive manner possible, including pain medication and physical therapy. Surgery is only used in the most severe cases of arthritis or separations.

    Contact Us

    Boston Children's Hospital
    300 Longwood Avenue  
    Fegan 2
    Boston MA 02115

    Boston Children's at Waltham
    9 Hope Avenue
    Waltham MA 02453

    Boston Children's at Lexington
    482 Bedford Street
    Lexington MA 02420

    Boston Children's at Peabody
    10 Centennial Drive
    Peabody MA 01960

    Boston Children's Physicians Weymouth
    Stetson Medical Center
    541 Main Street
    Weymouth MA 02190

    Boston Children's Physicians Brockton 
    830 Oak Street
    Brockton MA 02301

  • In-Depth

    How does arthritis affect the AC joint?

    Arthritis is a condition characterized by loss of cartilage in the joint.

    • Like arthritis at other joints in the body, it is characterized by pain and swelling, especially with activity.
    • Arthritis can lead to formation of spurs around the joint. These spurs are a symptom of the arthritis and not the primary cause of the pain.
    • Motions that aggravate arthritis at the AC joint include reaching across the body toward the other arm.
    • AC joint arthritis is common in weight lifters, especially with the bench press, and to a lesser extent military press.
    • AC joint arthritis may also be present when there are rotator cuff problems.

    What is an AC joint separation

    When the AC joint is separated, the ligaments connecting the acromion and collarbone are damaged, and the two structures no longer line up correctly. AC separations are graded depending upon which ligaments are torn and how badly they are torn. 

    • Grade I Injury –  the least damage is done, and the AC joint still lines up.
    • Grade II Injury – damage to the ligaments that reinforce the AC joint. These ligaments are only stretched but not entirely torn. When stressed, the AC joint becomes painful and unstable.
    • Grade III Injury – AC and secondary ligaments are completely torn and the collarbone is no longer tethered to the shoulder blade, resulting in a visible deformity.

    What causes arthritis of the AC joint?

    Arthritis of the AC joint mainly affects older adults. Your child may be at risk for arthritis of the AC joint due to:

  • Tests

    How does a doctor know my child has an AC joint injury?

    Your child's doctor may need a complete medical history in addition to a physical exam, which may include

    • X-rays – A diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film
    • Magnetic Resonance Imaging (MRI) – A diagnostic procedure that uses a combination of large magnets, radio frequencies and a computer to produce detailed images of organs and structures within the body. This test is done to rule out any associated abnormalities of the spinal cord and nerves.
  • How does a doctor care for arthritis of the AC joint?

    • There is currently no way to replace the cartilage damaged by arthritis.
    • The primary way to control the symptoms of arthritis is to modify your activities so as not to aggravate the condition.
    • Application of ice to the joint helps decrease pain and inflammation.
    • Medication including aspirin, Tylenol, and non-steroidal drugs anti-inflammatory drugs (NSAIDs) are also used commonly.
    • A shot of cortisone in some serious cases.

    How does a doctor care for an AC joint separation?

    An AC separation can be a very painful injury, so the initial treatment decreases pain.

    • Immobilizing the arm in a sling and placing an ice pack to the shoulder for 20-30 minutes every two hours, as needed.
    • NSAIDs can also help the pain.

    As the pain starts to subside, it is important to begin moving the fingers, wrist, elbow, and eventually the shoulder in order to prevent a stiff or frozen shoulder.

    • Instruction on when and how much to move the shoulder should be provided by your physician, physical therapist, or trainer.
    • The length of time needed to regain full motion and function depends on the severity or grade of the injury.
    • Recovery from a Grade I AC separation usually takes 10 to 14 days.
    • A Grade III may take six to eight weeks.

    When is surgery needed?

    When it comes to arthritis, surgery may be indicated if nonsurgical measures fail.

    • Since the pain is due to the ends of the bones making contact with each other, the treatment is removal of a portion of the end of the clavicle.
    • This outpatient surgery can be performed through a small incision about one inch long or arthroscopically using several small incisions.
    • Regardless of the technique used, most patients have full motion by six weeks and return to sports by 12 weeks.

    Grade I and II separations rarely require surgery. Even Grade III injuries usually allow return to full activity with few restrictions. In some cases, a painful lump may persist, necessitating partial clavicle excision in selected individuals (such as high caliber throwing athletes). Surgery can be very successful in these cases, but as always, benefits must be weighed against potential risks.

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