Pain in the lumbar spine and referred pain to the legs are symptoms that often fall to acupuncturists to treat, which is not surprising in view of how widespread they are. The incidence seems to be increasing; in Britain during the ten years up to 1993, outpatient attendances for this reason rose fivefold and the number of days for which social security was paid more than doubled. However, this may be due to a greater willingness on the part of patients to report symptoms rather than to a true increase in the number of patients suffering in this way, since the incidence of disabling back pain has not changed; the increase has been in back disorders that don’t significantly impair spinal flexion. This suggests that there is a cultural element in people’s attitudes to back pain.
Acute or chronic?
Acute back pain is defined as pain of less than 3 months’ duration, although in practice most patients in the ‘acute’ category recover considerably sooner than 3 months. Full recovery can be expected in 85 per cent of patients whose back pain is not accompanied by leg pain.
The thoracic and lumbar spine 115
Acupuncture can certainly be used in the acute phase, but there is no firm evidence to show that it shortens the duration of pain and disability. (The same is true of other forms of treatment.) Acupuncture is more often used for chronic pain, here defined as pain lasting more than 12 weeks.
Chronic back pain is of great economic importance: 50 per cent of the costs related to back pain are incurred for chronic pain. The cause is often unknown. Much time may be spent looking for abnormalities such as a herniated disk, an annular tear, spinal stenosis, or spondylolisthesis, but these are seldom found; abnormalities detected on MRI scans are frequently unrelated to the symptoms. Factors which correlate with pain are cardiorespiratory disease, smoking, psychological morbidity, and adverse social conditions.
The association with smoking is probably due to atherosclerosis. There is now evidence that vascular damage is important in chronic backache. Degenerative disk disease is associated with atherosclerosis and spinal artery stenosis which leads to damage to the annulus fibrosus. Pressure on veins due to disk degeneration and protrusion leads to nerve root damage.
Sympathetically maintained pain is also important and recent work suggests that such pain may arise from altered central modulation within the spinal cord. Peripheral nerve injury increases the excitability of the central nervous system. The dorsal horn receptor fields may expand so that pain is felt over a much wider area than would be expected. Changes within the brain itself may also occur in back pain, with abnormal activation of the cingulate region. Similar changes are found in atypical facial pain, which helps to explain why there is a connection between physical and psychological factors in the causation of both kinds of pain. This suggests that, for many patients, chronic back pain is not the same as acute back pain lasting longer but is a different clinical entity (Jayson, 1997). It may also partly explain the effectiveness of acupuncture in chronic low back pain. Acupuncture, in other words, may act by modulating the way in which central pain mechanisms operate. Psychological and neurological influences are so closely interwoven in these circumstances that it becomes almost meaningless to ask whether the response is due to the ‘placebo effect’.
Types of low back pain
There are several different types of low back pain, not all of which are suitable for acupuncture. It is important to take a full history and to carry out a physical examination before considering acupuncture.
1. Local back pain is due to compression or irritation of sensitive tissues; the causes include fractures, tears, or stretching of pain-sensitive tissues. This type of pain is accurately localized, often to the tips of the vertebral spines or the interspinous ligament. Acupuncture can be
useful in these cases. Pain that doesn’t vary with changes in position may be due to tumour or infection. This is type B pain (Chapter 8). 2. Spinal origin pain (type A) is dull, diffuse, and aching in quality. It is
poorly localized and its distribution does not correspond with that of a particular spinal segment. It may be felt in the spine itself or may radiate to the buttock, groin, anterior thigh, or anywhere down the leg, occasionally as far as the foot. The cause of this kind of pain is unknown. It is suitable for acupuncture treatment.
3. True radicular pain (type C) is different from the pain just discussed; it is sharp and ‘electric’ in quality and tends to follow a spinal segmental pattern. There may be areas of altered sensation and loss of reflexes. Coughing, sneezing, and straining at stool often make the pain worse. Changes in position that stretch the nerve roots may cause pain. If the sciatic nerve is affected (L5, S1), sitting may be painful and so may the straight leg raising test; if there is femoral nerve involvement (L2, L3, L4) sitting is not troublesome but the patient may be unable to straighten up. Since radicular pain is due to anatomical compression of nerve roots it isn’t to be expected that acupuncture will be of much direct benefit in this case.
4. Muscle spasm is often cited as a cause of pain but the mechanism is unclear, and some people think that it isn’t the spasm itself that is painful but rather the underlying lesion that is causing the spasm. The pain is dull in character and the patient’s posture is altered by the spasm.
5. Pain may be referred to the spine from abdominal and pelvic viscera, but usually the pain is felt in the abdomen or pelvis as well as the back. Occasionally, however, it is confined to the back. It is often unaffected by position.
Acupuncture is worth considering for pain types 1, 2, and 4. It is unlikely to help in the others and is positively contraindicated in 5, because of its masking effect, unless a definite diagnosis has been made and the acupuncture is being applied as a palliative treatment, for example in malignancy.