What is an AC Joint Injury?

Acromioclavicular (AC) joint injuries are commonly caused by a forceful impact to the shoulder. The acromioclavicular joint connects the scapula (posteriorly) to the clavicle (anteriorly) with stabilizing tendons, ligaments, and muscles. These stabilizers facilitate a wide range of movement. A blow to the shoulder–most frequently a fall with impact to the shoulder or a fall on an outstretched arm–may cause an injury ranging from a strain to the supporting soft tissues, to an AC joint separation or shoulder dislocation. Dr. Cunningham is a shoulder specialist at Vail Summit Orthopaedics and Neurosurgery. He is an expert at diagnosing and treating AC joint injuries and shoulder separations for patients in Vail, Aspen, and Denver, CO.

What are the Different Types of AC Joint Injuries?

The severity of an AC joint injury depends on the severity of the damage to the supporting structures of the shoulder. There are six different types of AC joint injuries, the most common being types one, two, and three. In AC joint injuries, there is some level of separation of the shoulder blade (the acromion portion of the scapula) from the collarbone (clavicle). There are six types of AC joint separations:

  • Type I: There is a partial tear of the acromioclavicular joint ligaments, but there is no tearing of the neighboring coracoclavicular ligaments. There is no displacement of the clavicle in relationship to the adjacent acromion bone. No deformity is visible on physical examination or on an x-ray.
  • Type II: The acromioclavicular ligaments are completely torn, and the end of the clavicle sits slightly upward in relationship to the acromion. This displacement is visible on physical exam. The displacement is less than 100% on an xray. There is no significant tearing of the nearby coracoclavicular joint ligaments.
  • Type III: Both the acromioclavicular joint ligaments and the coracoclavicular ligaments are completely torn. There is an obvious deformity of the AC joint that is visible on physical exam. On an xray, the end of the clavicle is 100% displaced in relationship to the acromion.
  • Type V: Both the acromioclavicular joint and coracoclavicular ligaments are completely torn. There is an obvious and severe deformity of the AC joint that is visible on physical exam. On an xray, the end of the clavicle is 200% or more displaced in relationship to the acromion.
  • Type IV and VI: The acromioclavicular joint ligaments and coracoclavicular ligaments are completely torn. There is an obvious and severe deformity of the AC joint that is visible on physical exam. In Type IV AC joint separations, the end of the clavicle is displaced posteriorly, not upwardly. Type VI AC joint separations are very rare. In this type, the clavicle is displaced down underneath the coracoid bone.

What are Shoulder Separation Symptoms?

The symptoms of shoulder separation vary based on the type of the injury. With a Type I AC joint separation, patients may experience bruising, tenderness and minor pain in the area of the AC joint. There is slight swelling, but no obvious deformity over the AC joint. Patients typically report minor pain with shoulder movement.

Type 2 AC joint separations cause more pain directly over the AC joint, and there is increased pain with shoulder movement. Swelling is present. A small bump at the outer end of the clavicle may be visible. The clavicle is slightly unstable, giving way with gentle pushing.

Type 3, 4, and 5 AC joint separation cause immediate pain, swelling, and an obvious deformity or bump over the AC joint. Any shoulder movement increases pain. The shoulder sits lower if one were looking in a mirror. Patients commonly report a popping sound with any shoulder movement. The clavicle is unstable, giving way with gentle pushing.

What are Separated Shoulder Tests?

A physical exam is performed of the separated AC joint to evaluate the severity of the AC joint injury. Peripheral nerve and vascular function is assessed. Shoulder range of motion is checked. A muscle strength test may be performed. An xray is ordered to determine the type of the AC joint injury as well as to rule out any associated fracture of the scapula or clavicle.

Do you Need Surgery for AC Joint Sprain?

Type 1 and 2 AC joint separations are treated non-surgically. A sling is prescribed for comfort, but patients are encouraged to come out of the sling for gentle range of motion exercises. Patients are encouraged to ice the shoulder. Over the counter pain medications may be needed. Physical therapy is prescribed. The physical therapist may try certain taping techniques which can help decrease pain.

For Type 4,5, and 6 AC joint separations, surgery is recommended as the results of non-surgical management are poor. Surgery typically consists of arthroscopic or open AC joint reconstruction in which the AC joint is re-aligned and held in the proper position with strong suture material and the torn ligaments may be reinforced with a donor tendon. Patients go home the same day as surgery, are placed in a sling for up to 8 weeks, but easy range of motion exercises and physical therapy is started immediately after surgery.

The Treatment of Grade 3 AC joint separations is somewhat controversial amongst shoulder surgeons. Dr Cunningham prefers a more conservative, non-surgical approach when managing these acutely as most patients do well without surgery. However, patients will always have a visible bump over the AC joint if managed without surgery.  If after several months, a patient is still having pain, weakness and disability, then AC joint reconstructive surgery can still be performed with good results. For some overhead athletes or for patients that do a lot of overhead work, Dr. Cunningham may recommend immediate surgical treatment for acute, Type 3 AC joint separations.

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Do I Need AC Joint Surgery?

Less severe AC joint injuries can be effectively managed without surgery, but more severely displaced AC joint separations do better with surgical correction. If surgery is required, it is better to have it done soon after the injury rather than waiting as then there is more scarring and shoulder mechanics are often already altered to compensate for the injury the longer one waits. The goals of AC joint reconstructive surgery is to realign and stabilize the separated AC joint, manage pain, and facilitate normal ligament healing.

Surgery can often be performed arthroscopically, leading to a quicker healing time. If a plate is used to assist in healing, it is likely removed after the injury has fully healed. Whether surgical or non-surgical treatment is prescribed, most patients will heal well and regain full motion, flexibility, and strength and be able to resume all normal activities. For patients who have suffered an AC joint injury or shoulder separation, Dr. Cunningham specializes in the treatment of AC joint injuries. Contact Dr. Cunningham today.

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Dr. Cunningham specializes in the treatment of knee, shoulder, and sports injuries.