Shoulder Joint Dislocation

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.

Dislocations backwards are not common and due to force applied to the arm when it is over the body and turned inwards, with epileptic seizures and electrocution being possible causes as the big chest and back muscles pull the joint out due to spasms. The joint can also dislocate downwards if the arm is moved outwards and sideways with excessive force, levering the joint out against the part of the shoulder blade above it. This type of injury needs careful monitoring as it is more likely to be associated with other soft tissue injuries such as nerve injury, damage to the blood vessels and tears to the rotator cuff muscles.

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.

A significant part of a shoulder dislocation is pain and doctors have many ways of ensure the best pain relief and make the reduction process as easy as it can be. If the dislocation is recent then the joint may be relocated without much in the way of analgesics or muscle relaxing drugs. The best sedatives used have a fast mode of action, good muscular relaxation properties and short duration of action so the patient recovers quickly. Once relocated the arm should be placed in a sling which may be retained for up to three weeks to allow the capsular tear to heal.

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.