AC (i.e., acromioclavicular) joint separation, or a shoulder separation, is defined as a dislocation of the clavicle (collarbone) from the acromion (part of the scapula). The shoulder joint is formed at the junction of three bones, the clavicle (collarbone), the scapula (shoulder blade) and the humerus (arm bone). The scapula and clavicle for the socket of the joint and the humerus has a round head that fits into this socket. A shoulder separation occurs where the scapula and clavicle come together. This should not be confused with a shoulder dislocation, which is when the humerus (arm bone) is displaced from the socket, a very different injury with contrasting treatment options.

Risk Factors
Risk factors for AC joint separation are fairly minimal in the general population, but increase in certain sports such as football and hockey. These types of injuries are usually attributable to a specific occurrence and are almost always due to a sudden, traumatic event. Normally, there is a direct blow to the shoulder, or a fall onto an outstretched hand that causes the injury.

Common symptoms of an AC joint separation are:
  •     pain, usually severe at the time of the injury
  •     swelling
  •     bruising

Diagnosis & Treatment
Doctors are often able to diagnose an AC joint separation based upon a description of how the injury occurred (i.e., history). A fairly simple physical examination is performed and an x-ray is taken to ensure there is no fracture of the bones. If the x-ray is unclear, doctors will often perform a second x-ray with the patient holding a weight. The weight accentuates any shoulder instability and will better show the effects of the separated shoulder.

The doctor then determines the grade of the separation. Shoulder separations are graded from type I to type VI, with types I, II and III being the most common. Additionally, types IV, V and VI are rare and often involve more severe trauma such as motor vehicle accidents.
  • Type I – a slight displacement of the joint. The acromioclavicular ligament may be stretched or partially torn. This is the most common type of injury to the AC joint. The bones are not out of position and the primary symptom is pain.
  • Type II – a partial dislocation of the joint in which there may be some displacement that is often hard to diagnose during a physical examination. The acromioclavicular ligament is completely torn, while the coracoclavicular ligaments remain in tact.
  • Type III – a complete separation of the joint. The acromioclavicular ligament, the coracoclavicular ligaments and the capsule surrounding the joint are torn. Usually there is a prevalent bump over the AC joint.
  • Type IV – an injury where the clavicle is pushed behind the AC joint.
  • Type V – the muscle above the AC joint is punctured by the end of the clavicle causing a significant bump over the injury, frequently thought of as an exaggerated Type III injury.
  • Type VI – an injury where the clavicle is pushed downwards and becomes lodged below the corocoid (part of the scapula).

Treatments vary depending on the grade of the injury. Types I and II are normally treated with pain medications and a short period of rest utilizing a shoulder sling. The treatment of a type III injury sometimes requires more medical judgment, as the difference in result between those injuries treated surgically and those treated through a more conservative approach is less clear. With surgery, the bump that appears due to an injury may still be present following surgery. In contrast, when surgery is not performed there may be more significant degeneration of the shoulder, which ends up requiring surgery to repair later. Also, there can be a marked increase in arthritis pain following an injury of this magnitude. Types IV, V and VI all typically require surgical intervention to correct.

If you or a loved one is suffering from a shoulder injury due to the negligence of another, you can find answers to many of your questions on this website. You can also use our “just ask” section to send us your question or our live chat for immediate response. For more information, download our FREE book, 10 Essential Steps You Must Take to Protect Your Personal Injury Claim.

For more information on these topics please contact Kansas City Accident Injury Attorneys by calling (816) 471-5111. Kansas City Accident Injury Attorneys has over 15 years of experience handling serious injury claims, including many shoulder injury cases, and any questions will gladly be answered.
James Roswold
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James Roswold is a Kansas & Missouri personal injury, workers comp, and medical malpractice attorney.