The clavicle, or collar bone, is normally attached to part of the shoulder blade known as the acromion, forming the acromioclavicular joint. Strong bands of tissue called ligaments bind the acromioclavicular joint and make it stable. An accident such as a fall can tear the ligaments, leading to what is known as acromioclavicular separation, or AC separation. AC joint separation varies in severity and treatment ranges accordingly. A simple sling may be all that is required in mild cases, but surgery is usually necessary for more serious injuries.
Acromioclavicular separation most commonly occurs in men in their twenties, and players of competitive sports, such as hockey, are most at risk. Typically, a fall on to the shoulder forces the acromion down, tearing the ligaments which attach it to the collar bone. Symptoms of acromioclavicular separation include pain and a decreased ability to move the shoulder. Sometimes there are visible signs of injury. The clavicle may protrude more than usual and the shoulder could appear deformed.
Different types of AC injury are classified according to their severity into one of six groups. In a type I acromioclavicular separation, the ligaments are sprained but not torn, while in type II only one ligament is ruptured. Type III injuries involve tears in all the ligaments. In types IV to VI, all the ligaments are torn and, in each case, the clavicle is pushed progressively farther out of position. Although a type VI acromioclavicular separation is rare, in this injury the collar bone moves so far out of place that it is pushed underneath the shoulder bone.
The treatment of acromioclavicular separation frequently involves the use of painkilling drugs. Ice may be applied to the injury site, and it is important to rest the joint. For type I and II separations, this may be the only treatment that is required. Patients may need to wear a sling for up to two weeks until their pain subsides and joint mobility improves. It is usually necessary to avoid strenuous activities for a number of weeks to allow the damaged joint to heal fully.
While type III injuries may be managed with or without an operation, type IV to type VI acromioclavicular separations are usually treated surgically. The surgeon exposes the joint and repairs the torn ligaments. Following surgery, the arm rests in a sling for the first two weeks. Patients then practice a supervised program of exercises to increase the strength and flexibility of the acromioclavicular joint.