We have still not fully resolved the recurring question about physical dysfunction. To what extent is it loss of physical capacity and ability, and how much is it a matter of performance? There is no question that there are objective physical changes in the muscles and backs of patients with low back pain (certainly by the chronic stage and probably from a much earlier stage). But much of what we measure clinically and biomechanically is performance. (Loss of) physical ability and physical performance go together and we can never separate them completely.
In an award-winning study, Mannion and her colleagues looked at the biomechanical effects of rehabilitation (Mannion et al 1999, 2001a, b, Kaser et al 2001). This was a randomized controlled trial of 148 patients with chronic low back pain. It compared active physiotherapy, muscle reconditioning on training devices, and low-impact aerobics. Pain intensity, frequency, and disability improved after all three treatments and these effects were maintained on 6-month follow-up. However, there was little difference between the three treatments.
There was a small improvement in the range of lumbar motion following treatment, but this only correlated weakly with improved pain and disability. Isometric strength and EMG activity increased after treatment, though the correlation between them was weak. Fifty-five percent of patients had loss of the normal flexion-relaxation response at baseline, but this did not improve following treatment. Endurance in the Biering-Sorensen test improved after treatment, but there was no corresponding improvement in EMG measures of fatigability. At baseline, the cross-sectional area of the paraspinal muscles and the fiber types correlated with isometric strength. Following treatment, there was little change in muscle size or fiber type. Improvement in strength did not correlate with any changes in muscle size. Altogether, physical changes in the muscles were insufficient to account for the observed improvement in muscle performance.
Treatment was clearly effective, but treatment effects appeared to be non-specific. Mannion et al (1999, 2001b) concluded that active therapy could improve physical function, but this was not due to direct improvement in muscle deficiency. Instead, the undoubted clinical improvement was mainly a matter of improved performance. Improvement in pain and disability depended more on changed perceptions and behavior. We might add that persisting muscle deficiency could explain the high recurrence rate of back pain.
The reason why disk injuries are so popular is that the idea is easy to understand, plausible, and acceptable to patients. It is amazing how many people with ordinary backache believe they have a "disk out of place" or "worn disks," with or without "trapped nerves." These ideas carry all the implications about permanent damage, fear of reinjury, and the need to rest or get fixed. We desperately need an equally simple, plausible, and acceptable explanation that fits modern understanding of the physical basis of back pain. It must also support modern ideas of management. Let me try to use the ideas in this chapter to develop an alternative explanation suitable for patients.
First, back pain is a physical problem. Psychosocial factors may influence how we react to pain and how it affects us, but they do not cause the pain. Back pain is not a psychological problem. Back pain starts with a physical problem in the back.
Second, back pain is a mechanical problem. It is a movement disorder or an activity-related disorder of the musculoskeletal system.
Third, back pain is only a symptom, not a disease. The most important message is that most back pain is not a signal of any serious disease or damage to the back.
Fourth, most back pain is simply a symptom of physical dysfunction. Pain and disability are intimately related to each other. The back is not working as it should. It is out of condition, like a car engine that is out of tune. This involves all the elements of dysfunction that we have discussed. Posture may be poor. The back is not moving normally, but may be stiff or seized up. This leads to fear and guarded movements. The muscles are not working properly, but may be weak and wasted and tire easily. There may be loss of strength and endurance and coordination. Loss of fitness makes it harder to rehabilitate. Changes in the nervous system lead to increased sensitivity, which together with stress and tension leads to a vicious circle. This whole pattern of painful dysfunction is the core of the problem and becomes self-perpetuating. It is much more important that any original, long-gone trigger for the pain.
Finally, this has obvious implications for management. The original cause or site of the pain really does not matter much any more. Whatever the original trigger, pain will continue as long as there is dysfunction. Recovery and relief of pain depend on getting the back working again and restoring normal function. The answer is to get moving. This leads to a sports medicine analogy, and sports medicine principles of rehabilitation. It also depends very much on the patient taking responsibility for what he or she does, rather than depending on a doctor or therapist to "fix it."
An explanation for patients
• Back pain is a symptom, not a disease. Most back pain is not due to any serious disease or damage in your back
• Back pain is usually a symptom of physical dysfunction. Your back is simply not moving and working as it should. It is unfit or out of condition
• Recovery and relief of pain depend on getting your back moving and working again and restoring normal function
I am well aware that we have limited scientific evidence for many of the ideas in this chapter, but they are firmly based on clinical observation. Some are unproven hypotheses. In many areas the evidence is limited or conflicting. There are large gaps in the evidence. However, I have argued already that we must seek the basic science that helps to explain our clinical findings, instead of trying to force our patients to fit basic science.
It is encouraging that so many health professionals from such different backgrounds have reached so much common ground - and that it fits modern
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