Shoulder Dislocation

The shoulder joint is a ball and socket joint but whereas the hip is a deep socket, the shoulder is very superficial. This gives the shoulder a much greater range of movement than the hip but in return it is much more unstable. The muscles around the shoulder are very important for protecting the joint and adding to stability.
Dislocation is usually anterior but can sometimes be posterior.

Mechanism

Dislocation of the shoulder is almost invariably traumatic. It is usually when people go down with a combination of abduction, extension, and a posteriorly directed force on the arm. The humeral head is driven anteriorly, tearing the shoulder capsule, detaching the labrum from the glenoid, and possibly producing a compression fracture of the humeral head.

Dislocated shoulders tend to affect males rather more than females but this is probably because of association with contact sports.
Posterior dislocation is much rarer. It may result from epileptic fits. Indeed, an unexplained posterior dislocation should suggest a history of convulsion. It can occasionally occur from trauma, usually associated with sport.

There is a history of trauma with pain in the shoulder and inability to move it. There may be multiple trauma as with a motor cycle accident and priorities may need to be established.

Anterior dislocation

• The patient with anterior dislocation keeps the arm at the side of body in external rotation.
• The shoulder looses its usual roundness and palpation of the anterior part will reveal a greater fullnes than usual.
• The axillary nerve and the circumflex humeral nerve and vessels can be damaged. It is probably easier to test for sensory rather than motor loss before reduction but after reduction the deltoid should be tested. Also check subscapularis.
• The rotator cuff is frequently damaged and should be examined after reduction.

Posterior dislocation

Posterior dislocation is much less obvious on examination and can easily be missed. Patients may sometimes present with a longstanding posterior dislocation. Instability may be in one direction only, it may be both inferior and posterior or it may be inferior, posterior and anterior.

• The patient usually presents with the arm adducted and internally rotated.
• Attempted abduction and external rotation are painful.
• The arm cannot be externally rotated to a neutral position.
• There is inability to supinate.
• The coracoid process appears prominant.
• Examination may resemble a frozen shoulder, especially with a chronic, unreduced dislocation.

• Is there a fracture too?
• Is it just a frozen shoulder? If in doubt x-ray.
• Is it recurrent dislocation? If so it will probably need stabilization

Even if the diagnosis of dislocation is clinically obvious, the shoulder should be x-rayed to exclude a fracture. The exception is a recurrent dislocation with minimal trauma. Some patients learn to reduce their own shoulders and do so before seeing a doctor.

A fracture dislocation will probably require surgery but without a fracture, closed reduction is usually adequate.
Many techniques have been described and for a description of a variety of them the reader is referred to the wheelessonline further reading listed at the end. After reduction x-rays should confirm a satisfactory result and the integrity of nerves and vessels must be checked.
The Hippocratic technique involves the surgeon placing his foot in the patient's axilla and considerable downwards traction. It is now regarded as of historical interest. (See picture)¹The patient may need to be managed before reaching hospital or before x-ray and reduction.

First aid management

Anterior dislocation is the only common shoulder injury that cannot be effectively immobilized with a simple sling and swathe as the arm is locked in moderate abduction and cannot be brought comfortably against the chest wall.

• The shoulder and arm must be splinted in the abducted position in which they are found.
• A pillow or rolled blanket is used to fill the space between the arm and chest wall.
• The elbow is flexed to 90° and a sling applied to support the arm.
• A pillow and sling are secured as a unit to the chest with one or two swathes.

Reduction

Immediate reduction

If the doctor witnesses an anterior dislocation of shoulder, perhaps during sport, if he is satisfied that there is no significant risk of fracture, there is much to commend rapid reduction.

• Local analgesia may be obtained by injecting 20ml of 1% lignocaine into the joint.
• The manoevre involves initial slight abduction and internal derotation of affected arm. This can be done without applying a great deal of traction.
• It is then immobilised in a sling.

There are several techniques for reduction of shoulders and a number can be found via the wheelessonline link at the end. They are generally slight variations of older techniques. Often sedation with an opiate and benzodiazepine are used in preference to general anaesthesia.

Stimson's technique

This is commonly used.

• The patient is placed in a prone position on the edge of the table while downward pressure is gently applied
• Weights may be taped to the wrist. It is usual to begin with about 2kg.
• Downward presure may be gently applied to aid reduction but this method may take 15 to 20 minutes.

A commonly used variation, whether by accident or design, is that the patient is left supine on a trolley in the A&E department with his arm dangling down whilst he waits in the queue for x-ray. By the time it is his turn, the shoulder may have reduced.
A technique with the patient seated is often employed for older patients.²
Posterior dislocation is usually amenable to closed reduction only if there is minimal displacement and it is of recent onset. Otherwise operative reduction is required, possibly with arthroplasty.
After reduction the shoulder is usually immobilized for 3 weeks although there is evidence that those who are mobilized sooner do no worse.³
Both types of dislocation may require surgery if a tear in the capsule prevents stable reduction or if soft tissue intervenes to prevent it.

Dislocation of the shoulder is often associated with damage to the capsule of the joint and this leads to instability and predisposes to recurrent dislocation. Eponynms include the Bankart lesion and the Hill-Sachs lesion. Figures that are sometimes quoted for the risk of further dislocation are 20% after 1 event, 50% after 2 events and 80% after 3 events but wheelessonline and other authorities give much more pessimistic figures. The risk is marked in young men who play contact sports. It is much less over the age of 40 or 50 but so is the urge to participate in contact sports.
A single dislocation in a young man who plays contact sport may well merit referral to an orthopaedic surgeon to assess stability of the joint with a view to a stabilization operation. Two dislocations in a young person certainly merits referral.
There are a number of procedures, dependent upon the nature of the lesion but most commonly used is a modified Putti-Platt operation. The results tend to be excellent⁴ and this includes the ability to return to top class contact sports.