For people of forty-five or younger low back pain syndromes are the major cause of activity limitation in the industrialised societies of the west. Defining what a chronic syndrome has been agreed that any condition lasting longer than the expected time of healing of the soft tissues could be classed as chronic, a period of approximately three months. The soft tissues of the body should heal in this time and pain has a useful survival function for us in these cases, making us remove the injuring forces and look after the damaged part as it heals. There appears to be no useful biological function for the chronic pain syndromes.
Overall back pain is very common and up to 20 percent of the population may have long term and recurring problems but they are not continually severe. A small group of 5-7 percent of back pain suffers develop a chronic pain problem which is disabling and prevents work. It is a relatively common cause of undergoing a surgical procedure and because much of the structure of the intervertebral discs is avascular this may slow the healing period significantly and make resolution of the problem less likely.
Injuries occurring to the spine and the onset of degenerative changes in the joints and the discs may explain many of the back pain problems which arise but there is a poor relationship between the amount of pathological changes in the spine and the level of pain suffered by a patient. MRI scanning reveals many disc changes such as protrusions or prolapses in individuals who are not complaining of significant pain. The causes are not well understood but may include inflammatory and neurological influences.
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.
