The shoulder is a ball and socket comprised of the head of the humerus (ball) and the glenoid (socket). The shoulder is stabilised by the labrum, ligaments and the muscles.
Shoulder dislocation occurs when the head of the humerus comes out completely from the socket. Partial separation is called a subluxation.
Shoulder instability refers to instability at the glenohumeral joint predisposing to shoulder dislocation.
The shoulder joint is the most commonly dislocated joint – comprising approximately 50% of all dislocations.
In 95% of cases, the dislocation is anterior where the ball comes out of the front of the socket. Other types include posterior, where the head comes out behind the socket and multidirectional.
Shoulder dislocations classically cause a tear of the labrum. It may also cause:
- Fracture of the glenoid.
- Hill Sachs lesion – Impaction / Depression of the humeral head.
- Rotator cuff tears – This is more common in the older age group.
- Biceps tendon injury.
Shoulder dislocation typically occurs during sports. Particularly contact and overhead sports. For example:
- Rugby league.
- Rugby union.
Shoulder dislocations may also occur as a result of accidents at work or at home such as falls from heights, motor vehicle accident or assaults.
There are a number of factors which predispose to a person having repeated episodes of shoulder dislocation.
This is the most important risk factor. The younger the patient is when they have their first dislocation, the greater the chance they will have repeat dislocations. An 18-year-old with a first-time dislocation, has an 80-90% of repeat dislocations.
Having ‘loose ligament’ will increase the risk of future dislocations.
Patients who have bone erosion or large fracture of the glenoid socket have a more unstable joint.
Contact athletes and athletes involved in overhead or throwing sports are at increased risk.
Signs and symptoms
Diagnosis is based on patient symptoms, examination findings and imaging.
The shoulder will dislocate with a painful mechanism. The pain will be relieved once the shoulder is placed back in joint. This may require manipulation by a physio / paramedic / doctor or may rarely ‘pop’ back in place itself.
Restriction of movement
Due to the shoulder joint being ‘out of place’, movement will be painful and restricted.
Some weakness may occur.
Some shoulder dislocations may cause nerve stretch / damage, and this will cause some loss of feeling, normally on the side of the shoulder.
Patients with recurrent dislocations may have multiple episodes of shoulder dislocating in their lifetime. These may be pain free and may start occurring even with a relatively minor injury.
X-ray and CT Scan
These can demonstrate if the shoulder is relocated back in place and if there is an associated fracture or erosion of bone (in patients with multiple dislocations).
These will show a tear in the labrum occurring as a result of shoulder dislocation. It may also show other soft tissue injury (e.g.: ligaments, capsule or tendons of shoulder).
The shoulder will require relocation back into place. There are different techniques, but this can be performed by:
- Somebody who has experience.
Immediate treatment then involves:
- Period of rest and immobilisation and rest in sling.
- Physiotherapy aimed at strengthening, education and stabilisation.
- Gradual return to sport.