Dislocation of the Shoulder

A joint dislocates when the two parts of the joint, usually sitting in close contact with each other, are torn apart and then remain apart without being in the close relationship they were anymore. Surrounding a joint is a bag of ligamentous tissue called the joint capsule which is torn when the joint surfaces are forcibly moved past each other. The joint surfaces can be injured as their hard edges move against each other during the process. Typical other damage can be nerve, further joint and ligament injury.

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.

Posterior shoulder dislocation is not frequent and occurs with the arm turned inwards and across the body, most often caused by muscle spasm in the large back and chest muscles from an epileptic fit or an electrocution event. A downward joint dislocation can occur if the arm is moved outwards and rotated outwardly with significant force, the arm bone levering against the underside of the shoulder blade and so pushing the joint out of place. The posterior dislocation is more commonly associated with side effects such as damage to the nerves and blood vessels or an injury to the shoulder rotator cuff muscles.

Dislocation can occur without trauma and in these cases the shoulder instability is often in all directions and more likely to occur in people who are hypermobile in their joints. This is known as multidirectional instability and is more common in younger people under thirty years old, occurring in both shoulders and tending to run in families. The joint problems may start with a subluxation which is a partial dislocation where the joint surface moves off the other one to some degree then snaps back again. Some people can dislocate their joint voluntarily and this may be connected with psychiatric difficulties in these patients.

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.

Pain is a major presentation problem in shoulder dislocation and there are many alternatives that the medical staff can apply to give good pain relief and ease the process of reduction. A recent reduction can be moderately easily relocated in the absence of strong painkillers or muscle relaxants. The most useful sedative drug will have a quick onset of action, be able to supply good muscular relaxation and with an action which goes off quickly to allow rapid recovery. After the joint is back in place a sling is used for up to three weeks to allow the capsular damage to heal.

Jonathan Blood Smyth is the Superintendent of Physiotherapists 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 Sheffield visit his website.