Friday, May 29, 2009

Low Back Segmental Stiffness

By Andrew Mitchell

As children we have the great gift of a mobile, strong, well designed and painless spine and it is unusual for stiffness to be an issue as the lumbar spine has evolved to do the job of weight bearing and providing movement. Intervertebral discs separate the spinal vertebrae, allowing more movement in areas where they are thicker and also coping with variable loads. The posterior spinal facet joints limit and control segmental movement, preventing the spine from displacing inappropriately under the shear forces. Strong, balanced and coordinated muscle actions complete the picture.

An acute episode of low back pain inhibits the core stabilising muscles from working well and can cause wasting of them with time. Segmental loss of stability control can make the occurrence of further low back pain episodes at the same level more likely. As time and injuries change the spine, degenerative changes can occur in the facet joints and discs, leading to segmental stiffness and chronic back pain. The force of gravity pushes fluid from the discs by compression and is opposed by a chemical absorption of fluid which is more powerful in lying.

If over time the compressive force gets the upper hand, the disc loses some of its hydration and eventually narrows. Narrowing can be seen on x-ray but the disc can start to become troublesome before it is changed enough to show up on the x-ray. In the spine two vertebrae and the intervening disc are known as a segment and it is the segments with altered discs which become stiff, preventing normal movement and forcing anatomical structures to take abnormal loads in abnormal positions. The vertebra above a stiff segment is unable to participate in normal movement and this stiffness can be felt by a physiotherapist.

After an acute back pain injury the surrounding musculature tends to go into muscle spasms to splint and protect the injured segment until inflammation reduction and healing have had a chance to begin. Steady reduction in pain and progress in healing is usually accompanied by lessening of the back spasms and a restoration of normal spinal movement. However, this does not always occur as muscles may remain contracted and overprotective, causing a shortened tissue area which keeps the local joints and other tissues in a permanently shortened position.

Sitting for extended periods can increase the likelihood of suffering from increased compression of the lumbar discs with consequent fluid loss. Repeated flexion maintains the regular cycle of fluid uptake and avoidance of this movement interferes with this important process for disc health. The maintenance of abnormal posture and lack of strength in the abdominal muscles are also important factors.

Chronic segmental stiffness is usually indicated by a history of back pain and general backache with some leg referral also possible. Since many and variable areas of the spine can be stiff or mobile, the stiffness which contributes towards the painful problem might have been present for some time. The pain is worse on sitting for long periods or doing bent over activities, anything which stresses the stiff segment towards the end of its available range of motion. The facet joints become stuck in an extended position and the segment tightens up by adaptive shortening, losing its ability to flex or maintain flexion comfortably. My back problems are like this and can be quite troublesome on stressing, leading me to avoid heavy work such as lifting objects of any weight.

Sarah Key, a physiotherapist who is well known in the UK, has produced the Sarah Key's Back Sufferers Bible, a book in which she sets out her views of what is going on in this most common of musculoskeletal syndromes. She does acknowledge that it is hard to bring solid evidence for many of her interpretations but seems to have many good and practical therapy ideas to approach the back pain problem with. She covers the main syndromes which typically occur, giving treatment routines for self management of each one, all of which I have found very useful for my own lower back pain. Now I have something I can do about it rather than accept it as a fact of life. - 14130

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