Friday, July 31, 2009

The Change from Acute to Chronic Back Pain

By Jonathan Blood Smyth

Chronic back pain is a very important and costly condition in advanced industrial societies which is the chief cause of limitation of physical function in younger people under 45. The definition of chronic is variable and can be taken to be a pain persisting beyond the expected healing time of the tissues which may have been damaged in the acute back pain event. This is often taken to be beyond twelve weeks as much of the soft tissue healing will have occurred at that point. Acute pain serves a biological purpose to warn us to stop doing the aggravating activity and to take care of the injured part, however chronic pain appears to have no useful function.

Back pain is a very widespread condition in the population and up to twenty percent may suffer from recurring or long term problems which are not greatly disabling. A smaller number of those people who get back pain, around five to seven percent, develop a long term pain problem which interferes with work and activity. Surgical procedures are moderately common for these problems and due to the poor blood supply of the inter-vertebral discs this may contribute to the slow resolution.

Most back pain appears to be caused by traumatic events to the back or is secondary to degenerative changes which occur in the spinal discs and joints. The connection between the spinal pathology and the pain with which a patient is suffering is not completely clear as many disc prolapses and protrusions seen on MRI scanning are not symptomatic. There may be neurological and inflammatory reasons for back pain but these factors are not clear and so the pathology of low back pain overall is not well understood.

If imaging and other diagnostic studies do not reveal a plausible pathological reason for a person's back pain then it is very easy to question whether psychological factors are responsible. Although psychological factors combine in a complex way in the progress from acute back pain towards a disabling condition there is no good evidence that psychological factors can produce pain. The cause of the pain may just not be amenable to the forms of investigation now prevalent. Once the condition is present or developing however, and arguably even in the acute stage, it is vital to identify and deal with all the non-physical factors to attain the best outcome.

The highest levels of low back pain claims occur in construction, heavy equipment operators and lorry drivers being high risk groups. In heavy workers such as in the construction of roads the levels of back pain and sciatica throughout their working lives appears to be very high. True sciatica occurs in only five percent of back pain cases and is a common reason for surgical intervention with L4/5 being the most commonly affected level, followed closely by L5/S1. Surgery for sciatica is rarely performed in the United Kingdom, with much elevated rates in other countries as in the US.

It is in western industrialised countries that the levels of disability from chronic low back pain have become very high with typical social and economic consequences. No genetic factors have been distinguished between different races to explain the variation in causative mechanisms. The split between male and female sufferers is about equal and people report low back pain mostly in middle age when the large majority have evidence of spinal degenerative changes. Sciatica, closely related to disc changes, occurs mostly in the 30s and 40s with age 42 being the average age for lumbar discectomy.

The lumbar spine is the last part of the flexible spinal column and is meant to support the upper body weight as it is passed through to the legs in gait. Compared to its size the lumbar spine is able to cope with heavy loads which are passed via the sacroiliac joints to the pelvis and to the hips. The lumbar bones are relatively mobile whilst still managing to transmit significant loads by means of their internal bony architecture where the cancellous strut formations align in strengthened areas to fit the applied forces. The lumbar vertebrae have to transmit greater and greater forces as they go down and for this purpose the vertebral bodies become larger the lower they are. - 14130

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