Dislocation of the Shoulder

December 26, 2009 by Jonathan Blood Smyth
Filed under Fitness

A joint dislocation occurs when the two joint surfaces, which normally sit in intimate contact with each other, are wrenched away from each other to lie apart without any relationship. Joints have a surrounding ligamentous bag called a joint capsule and this can be typically injured as the surfaces force their way past each other. The surfaces of the joints themselves can be damaged as they hit each other on the way to becoming dislocated. Other injuries which can occur include damage to the local nerves and ligaments.

Dislocations of the shoulder are the most common form of dislocation of a joint, making up almost half of all of this type of injury. The commonest form of dislocation is for the humeral head to be displaced forwards, known as an anterior dislocation. This occurs most often when the arm is out to the side, rotated externally and moved backwards and there is a forwards force on the upper arm, pushing the joint out in its position of vulnerability. A blow to the rear of the arm, a fall on an outstretched hand (FOOSH) and a strong outward rotation plus shoulder abduction can all result in a dislocation.

A posterior dislocation is uncommon and secondary to a stress on the arm when it is inwards across the body and inwardly rotated, with the large back and chest muscles sometimes pulling the joint out of its socket. This can occur if someone is electrocuted or if they have epileptic seizures, both of which can cause muscle spasms. The shoulder can dislocate downwards if there is a very forceful movement of the shoulder outwards and sideways, with the joint being levered out over part of the scapula above. This sort of dislocation should be closely monitored as complications of the injury are common with nerve damage, blood vessels injury and rotator cuff tears.

An atraumatic shoulder dislocation can occur with a tendency for the joint to be unstable in every direction, often present in patients with joint hypermobility. Multidirectional instability is the medical term given to this syndrome which presents in families, in younger people of less than 30 years and occurs in both shoulders. Subluxation of the joint can occur initially which involves one side of the joint coming off its opposite number to a degree and then relocating suddenly into position. Shoulders can be dislocated voluntarily in some cases, although this may normally be connected with psychiatric disorders.

Anterior shoulder dislocation typically shows by a patient holding their arm slightly to the side and turned outwards, with a palpable anterior bulge due to the humeral head sitting to the front of the shoulder. Muscle spasm around the shoulder can be powerful and severe pain results from attempting to move the joint. A backwards shoulder dislocation forces patients to hold their arm in close to the body and rotated inwards, with the head of the arm bone felt at the back. Misdiagnosis as frozen shoulder has been recorded.

The relocation of a shoulder dislocation is performed by surgeons in many different ways and the time from the incident to when the joint is finally relocated is the important matter. If the time is too long the muscle spasm increases and interferes with fixing the dislocation. An original way was to put a foot in the person\’s axilla to make one end secure and traction the arm lengthways until the reduction is effected. Techniques have developed and an effective modern way is to abduct the shoulder whilst pushing the humeral head anteriorly, then rotate the arm externally and traction the arm, leading very often to success.

Shoulder dislocations are usually extremely painful and the medical management of pain relief has many options to optimise the ease of reducing the joint dislocation. If the dislocation has been present for a shorter time it is easier to relocate without the help of narcotic drugs or stronger muscle relaxation medication. Sedatives are useful and best if they act quickly, provide good relaxation of the muscles and lose their effect quickly to facilitate recovery. On reduction the aftercare for the joint is to use a sling for up to three weeks to allow the healing of the capsule.

Jonathan Blood Smyth is the Superintendent of Physiotherapy at an NHS hospital in the South-West of the UK. He writes articles about back pain, neck pain, and injury management. If you are looking for physiotherapists in Manchester visit his website.