Shoulder Separation (Acromioclavicular Joint Injury)

Shoulder separation is not an injury to the main shoulder joint itself.The injury actually involves the acromioclavicular joint (ACJ). The ACJ is where the collarbone (clavicle) meets the highest point of the shoulder blade (acromion). It is not the same as a shoulder dislocation. A dislocated shoulder occurs when the arm bone comes out of the main shoulder joint.

In a mild separated shoulder, the ligaments may just be stretched. In severe injuries, ligaments may be completely ruptured.

Cause

Acromio-clavicular joint injuries tend to occur in contact sports such as rugby and football as well as falls from the bicycle or motorcycle. The usual mechanism of injury is a fall onto the tip of the shoulder under significant force or momentum.

The trauma of the fall onto the point of the shoulder may tear the acromioclavicular ligaments as well as result in apparent superior subluxation of the clavicle (in-fact downwards displacement of the acromion).

The forces from the fall can lead to rupture of the coracoclavicular ligaments leading to complete dislocation of the joint. The latter injuries may be classified by severity with a view to guiding treatment, both operative and non-operative.

The patient will experience pain in the shoulder region together with difficulty in lifting up the arm of the affected shoulder. There may be a swelling of the ACJ due to the injury.

Signs & Symptoms

This injury can make the shoulder look abnormal from the end of a bone sticking up or the shoulder hanging lower than normal.

Pain is usually at the very top of the shoulder.

The attending physician may have the patient hold onto a weight while examining to see if your collarbone sticks out. An x-ray of the shoulder may help diagnose a shoulder separation.

Treatment

Treatment depends on the severity of the acromio-clavicular joint dislocation.

Doctors classify the dislocation based on the x-ray appearances and grade them accordingly (using the Rockwood’s classification):

The main concern is the integrity of the coraco-clavicular ligaments.

In a nutshell, once the coraco-clavicular ligament (labelled as “ligament torn” in the above diagram) is disrupted, the distal end of the collar bone will tend to lift up with respect to the acromion. In fact, the real situation is that the acromion sags downwards with respect to the distal end of the collar bone. This produces the swelling and prominence seen in patients.

Types I and II Injuries

Referring to the Rockwood’s classification, Types I to II have intact coraco-clavicular ligaments. In these patients, the prominence or deformity of the bony bump is minimal – can generally be managed without surgery (physiotherapy).

However, these injuries may result in persistent shoulder pain, swelling and/or dysfunction in the future – and may progress to develop symptomatic degenerative disease – even though x-rays showed Type I or II injuries. It could be due to the cartilage injury to the joint which occurred at the time of the accident. Surgical treatment using arthroscopic resection of the distal clavicle can be offered in these patients.

Types III to VI Injuries

In Types III to VI, the coraco-clavicular ligaments are disrupted and hence the distal end of the collar bone (clavicle) tends to appear elevated.

Type III
Type III can be treated with or without surgery. In most patients, non-surgical treatment leads to reasonably good results. However, in some of these Type III patients, the joint can become painful or sore. The upper limb may become weaker as well. Hence some patients opt for surgery in Type III separations. Many surgeons believe that this degree of displacement leads to muscle-fatigue discomfort and difficulty manipulating heavy loads. As a result, operative intervention should be considered in heavy labourers and younger patients who are athletic.

Patients who are not keen for surgery can have a trial of non-surgical treatment via physiotherapy. If they become symptomatic later on, delayed surgery can still be done. It should be noted that without surgery, Type III bony prominence will be permanent. The joint does not reduce on its own when treated conservatively.

Types IV to VI
Types IV to VI injuries generally require surgical treatment for a good outcome. As the clavicle is so far displaced from the acromial process in the posterior, superior, or inferior direction, respectively, conservative management is inadequate. The patient continues to experience pain and dysfunction if the articulation is not reduced and stabilized.