Shoulder Separation / AC Separation

Shoulder separations and AC separations are different expressions for the same injury. Shoulder / AC separations are very common, especially among athletes involved in contact sports. However, shoulder / AC separations are not the same thing as a shoulder dislocation, though they are commonly confused.

The shoulder is a complex joint made up of three bones:

• the HUMERUS – the upper arm bone
• the SCAPULA – the shoulder blade
• the CLAVICLE – the collar bone

The scapula has a shallow socket called the glenoid, which the ball of the humerus fits into. The union of these bones is referred to as the glenohumeral joint or shoulder-joint. (To see a very good animation – click here)

Shoulder Dislocation

When the glenohumeral joint is disrupted, the humerus loses contact with the glenoid and results in the condition known as shoulder dislocation.

Shoulder Separation

The uppermost part of the scapula (shoulder blade) is known as the acromion. The union of the clavicle (collar bone) and the acromion is called the acromioclavicular joint or AC joint. When this joint is disrupted, a shoulder separation / AC separation results.

Shoulder separations classified by severity of injury

Shoulder separations are classified according to the severity of the injury. You may hear it described as different levels, grades, types or degrees of separation.

All joints are held in place by ligaments (extremely tough, tissue structures that connect bone to bone). In the AC joint, one set of ligaments forms the joint capsule around the AC joint (this is known as the acromioclavicular ligament). Two other ligaments connect the clavicle to a bony protrusion of the scapula, called the coracoid process. These are called the coracoclavicular ligaments.

• TYPE I – there is a partial tear of the acromioclavicular ligament (AC ligament), with no change of the position of the clavicle (collar bone).
• TYPE II – there is the rupture of the AC ligament and partial tearing of the coracoclavicular ligament with some change of the position of the clavicle (collar bone).
• TYPE III – there is the rupture of the AC ligament and coracoclavicular ligament, definite upwardly displaced clavicle.
• TYPE IV – there is posterior (rearward) displacement of the clavicle, behind the AC joint.
• TYPE V – there is an upward displacement of the clavicle, puncturing muscle tissue.
• TYPE VI – there is a downward displacement of the clavicle, which becomes lodged beneath the acromion or coracoid process.

TYPE I and TYPE II separations are the most common types of AC separations and rarely require surgery.

TYPES IV, V and VI are rare injuries and commonly result in surgical repair.

TYPE III separations are the most controversial. They are fairly common, but there is still some debate as to whether surgery is the “right” treatment, though surgery may be recommended for high level throwing athletes. Some feel that the joint will heal without surgery if the injury is managed properly.

Surgery for a TYPE III separation usually involves relocating the AC joint and repairing the torn ligaments. The clavicle will also be secured, either by screw or possibly goretex tape, until the ligaments have had sufficient time to heal. If a screw is used to secure the clavicle, then it is normally removed within eight weeks of surgery.

In the event that you are faced with a TYPE III AC separation, consult with your physician about the pros and cons of surgical and non-surgical treatment. Ask about:

• possible physical restrictions you may face
• mobility issues
• the strength of your shoulder
• possible future complications
• your rehabilitation time
• any possible risks