What is a shoulder dislocation?
The shoulder consists of the clavicle (collarbone), the scapula (shoulder blade) and the humerus (upper arm bone). The humerus inserts inside the glenoid cavity (socket) of the scapula. It is the joint with the highest range of movement, due to the high number of surrounding muscles. Shoulder dislocations are a common injury in sports and occur when the head of the humerus comes out of the glenoid cavity. This causes a lot of pain and hinders movement of the arm.
After first occurrence of a shoulder dislocation, the probability of a second occurrence decreases with age: it is greater than 80% in people aged under 20 years and below 20% in people aged over 40 years.
There are different types of shoulder dislocation:
- Subcoracoid dislocation: the most common anterior dislocation of the shoulder. In this type, the humeral head moves to below the coracoid process of the scapula. The most common causes are falls onto a hand or onto an elbow while it is extended, slightly separated from the trunk and pointing backwards.
- Subglenoid dislocation or extracoracoid dislocation: The humeral head is positioned on the glenoid cavity rim. Usually occurs with falls, when the arm is in a forced internal rotation position, which is why it is not very common.
- Subclavicular or intracoracoid dislocation: The humeral head is positioned on the ribs. It occurs with falls with flexion, adduction and internal rotation.
Although shoulder dislocations are not very serious injuries, one of the major considerations, apart from pain, is the potential for damage to the ligaments, blood vessels and nerves of the shoulder capsule. An orthopaedic specialist and a physiotherapist evaluate whether these structures have been compromised and also whether the nerves that innervate the various structures have been damaged, given that capsule retractions are very common if not managed early.
Shoulder dislocations are very painful, to the extent that the patient cannot move their arm.
Due to the fact that many nerves insert in the shoulder joint, the injury may be complicated by neurological damage that makes the arm numb and prevents movement.
However, the main damage occurs in the cartilaginous ring located at the end of the joint. Its function is to ensure that the humeral head inserts into the glenoid cavity. Normally, the glenoid cavity and ligaments are damaged. With recurrences of shoulder dislocation, the ligaments gradually become more lax.
Testing for shoulder dislocation
First, the specialist takes a full medical history to diagnose every type of injury or dislocation. These data are used to determine the appropriate treatment and the prognosis. In addition, X-ray and CT scans must be done to better observe the injury and any possible effects on vessels or nerves.
In parallel, the specialist must analyse and evaluate the shoulder’s instability. To this end, an orthopaedic assessment may be done. The more orthopaedic tests give a positive result, the lower the probability of a wrong diagnosis.
What are the causes of shoulder dislocations?
The usual cause of shoulder dislocations is a traumatic injury, i.e. a forceful impact on the joint that forces it beyond its limits.
Recurrence of shoulder dislocation does not require a forceful impact; rather, a minor movement of the joint may cause muscles holding the joint in place to become more lax.
Can it be prevented?
Shoulder dislocations cannot be prevented. Patients who suffer from repeated shoulder dislocations can however take preventive measures, by being more careful with movements they make and following the specialist’s advice.
Treatments for shoulder dislocation
Shoulder dislocations are extremely painful, and therefore require prompt attention to reposition the humeral head in its correct position. This requires specific mechanical manipulations that can only be performed by an orthopaedic specialist or a physiotherapist.
In parallel, the patient will receive medication to relieve pain. The specialist places the shoulder in its correct position – as this procedure may be painful, it is sometimes performed in the operating theatre under anaesthesia. Next, the arm is immobilized with a sling. An X-ray and MRI scan must be done to evaluate possible damage to other structures and ligaments.
People who do intense physical activities are more likely to suffer from repeated dislocations. In such cases, surgery with arthroscopy may be recommended to repair the ligaments. This is a minimally invasive intervention, so postoperative recovery will be shorter. Rehabilitation is necessary to restore mobility and strengthen muscles.
Which specialist treats it?
Shoulder dislocations are primarily managed by two types of specialists. An orthopaedic specialist determines the diagnosis and the most appropriate treatment for the shoulder dislocation. He determines the injury type and which structures have been damaged, and decides whether an orthopaedic or surgical approach should be used.
A physiotherapist provides non-pharmacological therapy. They contribute to symptom relief via a series of manual exercises and techniques, and the application of hot, cold, light or water.