Anatomy of the Shoulder

The shoulder is a complex, ball-and-socket joint made up of three bones: the upper arm bone (humerus), shoulder blade (scapula), and collarbone (clavicle). The ball, or head, of the upper arm bone fits into a rounded socket (glenoid) in the shoulder blade. The arm bone is kept centered in the shoulder socket by a combination of muscles and tendons (rotator cuff). The rotator cuff covers the head of the upper arm bone and attaches it to the shoulder blade.

The AC (acromioclavicular) joint is formed where a portion of the scapula (acromion) and the clavicle meet and are held together by tough tissues (ligaments) that act like tethers to keep the bones in place.

What is a Shoulder Separation, or AC Joint Sprain?

A shoulder separation is actually an injury to the AC joint, not the shoulder joint. It is commonly the result of a direct fall onto the shoulder that injures the ligaments that surround and stabilize the AC joint. If the force is severe enough, the ligaments attaching to the underside of the clavicle are torn, causing separation of the collarbone (clavicle) and wingbone (scapula). The scapula moves downward from the weight of the arm, creating a bump or bulge above the shoulder.

Severity can range from a small change in shoulder configuration with mild pain, to a more deforming and painful injury. Even in severe cases, good, pain-free function often returns, however, the greater the deformity the longer it requires to recover.

Diagnosing a Separated Sholder

A shoulder separation, or AC sprain, often causes a deformity that makes it easy to identify. Where there is less deformity, X-rays and the location of pain can aid in diagnosis. In some cases, asking the patient to hold a weight can increase the deformity so it becomes more obvious on X-rays.

Like other types of ligament injuries, shoulder separations (AC joint sprains) are classified by the degree of severity of the injury.

  • Grade 1—Involves stretching/spraining of the joint covering (capsule), with no damage to ligaments connecting the shoulder blade (scapula) and collar bone (clavicle). There may be swelling over the joint but the bump is not permanent. Pain typically lasts for 2-4 weeks, but can be easily reaggravated. Surgery is usually not required.
  • Grade 2—Involves tearing of the joint covering (capsule) and stretching (but not tearing) of ligaments connecting the shoulder blade (scapula) and collar bone (clavicle). Frequently results in a small, permanent bump over the top of the shoulder at the AC joint. Initial pain typically lasts 4-6 weeks, however, chronic discomfort at the joint may be experienced when lifting weights or performing other overhead or lifting activities. Surgery is usually not required.
  • Grade 3—Involves tearing of the joint covering (capsule) and ligaments connecting the shoulder blade (scapula) and collar bone (clavicle). Causes a mild to moderate permanent bump over the top of the shoulder at the AC joint. Pain typically lasts 4-8 weeks. Surgery is usually not required.
  • Grade 4—Defined as a significant posterior displacement, occuring when the clavicle is severely displaced backwards.
  • Grade 5—Involves tearing of the joint covering (capsule) and ligaments connecting the shoulder blade (scapula) and collar bone (clavicle), and the end of the collar bone (clavicle) tears through the muscle covering (fascia) above it. Results in a large, permanent bump over the top of the shoulder at the AC joint. Pain typically lasts 4-8 weeks, however chronic discomfort is common. Surgery is frequently recommended.

Nonsurgical Treatment

It is often worthwhile to wait and see if reasonable function will return without requiring surgical treatment. Placing the arm in a sling to hold the shoulder in place as it heals, application of cold packs, and medications are among the most common nonsurgical treatments used to help manage pain. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen or aspirin may provide some relief from symptoms. However, whether using over-the-counter or prescription strength, they must be taken carefully. Using these medications for more than one month should be reviewed with your primary care physician. If you develop acid reflux or stomach pains while taking an anti-inflammatory, be sure to talk to your doctor.

Surgery

If pain persists after nonsurgical treatment, or if the deformity is severe, your orthopaedic surgeon may recommend trimming back the end of the collarbone so that it does not rub against the acromion. Where there is significant deformity, reconstructing the ligaments that attach to the underside of the collarbone is helpful. This type of surgery works well, even if it is done long after the problem started.

With any surgery, there are some risks, and these vary from person to person. Complications are typically minor, treatable and unlikely to affect your final outcome. Your orthopaedic surgeon will speak to you prior to surgery to explain any potential risks and complications that may be associated with your procedure.

Recovery

Whether treated conservatively or with surgery, the shoulder will require rehabilitation to restore and rebuild motion, strength and flexibility. Most people are able to return to near full function after this injury, even if there is a persistent, significant deformity. Some experience continued pain in the area of the AC joint, even with only a mild deformity. This may be due to the development of arthritis, abnormal contact between bone ends when the joint is in motion, or injury to the cartilage found between the bone ends of the joint.