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Shoulder Joint Dislocation
Dislocation of a joint means that the joint surfaces, which are normally closely applied to each other, are completely disrupted and do not touch each other any longer. The joint capsule surrounds the joint and supports it and is often damaged as the joint surfaces move apart from their normal position. Dislocations may also result in damage to the joint surfaces themselves as they move across each other in their journey to the dislocated position. Joint, ligament and nerve injuries can occur during dislocations.
Of all joint dislocations, shoulder dislocations are the most common, making up almost half the total number of this kind of joint injury. An anterior dislocation, with the head of humerus coming off the shoulder socket to the front, is the most common form of this condition. The most usual position for the shoulder to dislocate in is when there is a force applied to the back of the arm with the arm in an outwardly rotated, extended and abducted position. Less commonly a blow to the back of the arm might do it, or a fall on the hand or just moving the arm forcefully outwards and rotating it externally.
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.
There may be no trauma in some cases of shoulder dislocation and instability of the shoulder may occur in all joint directions, typical presenting in patients who have hypermobile joints. This condition is called multidirectional instability and tends to happen in both shoulders, run in the family and be in younger people under thirty. A joint subluxation is often the start of these problems, where the joint slips partly off its partner to an amount and then clicks back into place. An ability to voluntarily dislocate the shoulder can occur, perhaps related to psychiatric difficulties in this group of people.
The presentation of anterior dislocation of the shoulder is for the patient to hold their arm rotated outwards and slightly to the side, the arm bone head easily felt at the front of the joint. The shoulder muscles may be in a powerful spasm and trying to move the shoulder results in high levels of pain. A dislocation of the shoulder posteriorly shows itself by the patient keeping the arm close to the body and turned inwards, the head of the humerus being palpable at the rear of the joint, although this condition has been misdiagnosed as frozen shoulder.
Reduction of a shoulder dislocation can be performed in a large number of techniques but it is the time from dislocation to when the shoulder is relocated which is important. As the time increases the muscle spasm becomes more severe, making reduction more difficult. An old technique is to place the foot in the armpit to provide stability and pull the arm lengthways until the joint goes back into place. Less traumatically the upper arm can be moved away from the body and the head of the humerus pushed forwards. Once the shoulder reaches 90 degrees the arm is turned outwards and traction applied.
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, editor of the Physiotherapy Site, writes articles about Physiotherapist, back pain, orthopaedic conditions, neck pain, injury management and physiotherapists in Brighton. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK
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Filed under back pain by on Dec 28th, 2009. 
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