Friday, May 29, 2009

Pain threshold

In a technical and medical literature the term pain threshold indicates the least stimulus which elicits pain (as reported by the subject) and is clearly differentiated from the term pain acceptance which indicates the degree of pain which a topic can tolerate before experiencing physical or emotional impairment and involves a measurement of a subject's response to pain. Compare this to absolute threshold, which is the lowest level of stimulus that is physiologically measurable.



Increased and decreased pain threshold

Pain threshold is frequently a function of how healthy the pain nerves and central pain processing pathways are, and of the chemical milieu in the tissues which the nociceptors innervate. It is commonly reduced by inflammation in the vicinity of nociceptors, such that normal touch becomes painful in the area of inflammation (allodynia). In such circumstances, the use of anti-inflammatory medications or physical therapies such as cooling or mild heat may return the nerve sensitivity or threshold to normal - it does not increase the threshold to above normal.

The use of morphine-like drugs does elevate the pain threshold (as well as pain tolerance). The same is true of a diverse number of other centrally acting analgesic drugs affecting pain relay neurons. Local physical techniques such as electrical stimulation, cooling or heat may temporarily increase the pain threshold.

However, short of damaging pain nerves - such as may occur in nerve injuries or neuropathies - the effects of interventions (pharmacological or physical) used to increase the pain threshold do not last much longer than the duration of their use. Additionally, in normal healthy persons, it is not significantly changed by any mental or physical practice or training. In contrast, pain tolerance may be increased by medications as well as by physical, cognitive and affective interventions and training.

Sunday, May 3, 2009

Joint dislocation


Joint dislocation, or luxation (Latin: luxatio), occurs when bones in a joint become displaced or misaligned. It is often caused by a sudden impact to the joint. The ligaments always become damaged as a result of a dislocation. A subluxation is a partial dislocation.A dislocated joint can only be successfully 'reduced' into its normal position by a trained medical professional. Trying to reduce a joint without any training could result in making the injury substantially worse. X-rays are usually taken to confirm a diagnosis and detect any fractures which may also have occurred at the time of dislocation. A dislocation is easily seen on an X-ray. Once a diagnosis is confirmed, the joint is usually manipulated back into position.

This can be a very painful process, therefore this is typically done either in A&E under sedation or in an Operating Room under a General anaesthetic.
It is important the joint is reduced as soon as possible, as in the state of dislocation, the blood supply to the joint (or distal anatomy) may be compromised. This is especially true in the case of a dislocated ankle, due to the anatomy of the blood supply to the foot. Shoulder injuries can also be surgically stabilized, depending on the severity, using arthroscopic surgery. Some joints are more at risk of becoming dislocated again after an initial injury. This is due to the weakening of the muscles and ligaments which hold the joint in place. The shoulder is a prime example of this. Any shoulder dislocation should be followed up with thorough physiotherapy. There are some medical conditions by where joint dislocations are frequent and spontaneous, such as Ehlers-Danlos Syndrome and Congenital Hip Dysplasia.