Education And Debate

ABC of Rheumatology: LOW BACK PAIN

BMJ 1995; 310 doi: https://doi.org/10.1136/bmj.310.6984.929 (Published 08 April 1995) Cite this as: BMJ 1995;310:929
  1. J R Jenner,
  2. M Barry

    Low back pain is a major and increasing cause of disability in the United Kingdom. In 1993, 11% of the population reported that their activities had been restricted by back pain within the past four weeks. Satisfactory treatment of low back pain depends on an accurate diagnosis, but finding the cause for low back pain is often not possible because of difficulties in localising the source of the pain.

    In 1938 it was shown that many structures in the lumbar spine, when irritated, give rise to pain with very similar distributions. Despite technological advances the identification of an exact source of pain or an exact pathological diagnosis often remains elusive. It is important for doctors and patients to understand that the diagnosis of low back pain therefore depends on identifying some clinical syndromes on the basis of a patient's history and examination, with appropriate investigations to exclude serious pathology and support the clinical diagnosis. If this principle is misunderstood the result can be a misleading diagnosis and inappropriate treatment.

    Figure1

    Radiation of pain after injection of 0.1-0.3 ml 6% hypertronic saline into sacrospinal muscle (yellow) and multifidus muscle (red). Note similarity to distribution of sciatic pain.

    Back pain syndromes

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    Mechanical back pain or prolapsed lumbar disc

    It is vital to distinguish mechanical causes of back pain from other causes as patients with mechanical causes are likely to respond to physical forms of treatment. The symptoms and signs of mechanical back pain differ considerably from those associated with back pain caused by underlying systemic disease.

    Most acute episodes of low back pain arise in the triad of joints that allow one vertebra to articulate with another (that is, the intervertebral disc anteriorly and the two facet joints posteriorly). The commonest primary pathology is degeneration of the nucleus pulposus in the lumbar disc. The disc itself is often not the source of pain; this may arise in other structures, such as the facet joints or the many surrounding ligaments, that come under stress as a result of the disc pathology. It is important that doctors explain this to patients so that they understand why just removing their disc will not always cure the pain.

    True sciatica, with pain and numbness in the distribution of a single lumbar nerve root, may be accompanied by sensory, motor, or reflex changes and is most commonly caused by a posterolateral protrusion of a disc impinging on the nerve root.

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    Systemic back pain

    As well as back pain, there may be associated systemic features such as weight loss, pyrexia, and general malaise. Examination should include the testicles and prostate in male patients and the breasts in female patients as tumours in the sex organs metastasise preferentially to the skeleton.

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    Ankylosing spondylitis

    This can be difficult to distinguish from mechanical pain, especially in the early stages. However, morning stiffness for more than 30 minutes, pain that alternates from side to side of the lumbar spine (a symptom rarely reported in any other cause of back pain), sternocostal pain, and chest expansion of less than 5 cm suggest ankylosing spondylitis. Education, anti-inflammatory drugs, and exercise are the mainstays of treatment.

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    Special and lateral recess stenosis

    Spinal stenosis is common in people aged over 60 and is often not considered in the diagnosis of back and leg pain. It is caused by a narrowing of the spinal canal or intervertebral foramen resulting from degenerative disease. The symptoms should be compared with those of peripheral vascular disease (in this condition the pain eases when a patient stands still and upright). Computed tomography is the investigation of choice. In severe cases surgery may be required to decompress the stenotic area.

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    Postural pain

    Bad posture is probably the commonest cause of persistent back pain. The spine depends for its strength on maintaining a series of arches. Sitting and leaning forward tend to flatten the arch or lordosis, while wearing high heels tends to exaggerate the arch (hydcerlordosis or sway back).

    Unequal leg length is easily overlooked; 2% of the normal adult population have differences in leg length of at least 2 cm, and such people are more prone to back pain. This can be diagnosed in the surgery by placing wooden blocks of different thicknesses under the short leg and checking the pelvic level visually. Up to a third of patients with back pain and differences in leg length of more than 2 cm will gain relief with a heel raise.

    Advice on correcting bad postural habits may be difficult for a patient to accept and may need to be reinforced through programmes such as a back school.

    Referred pain

    Pathology in organs in the posterior part of the abdominal cavity may refer pain to the back—for example, aortic aneurysm or enlarged lymph nodes. Examination of the abdomen is vital for exclusion of these diagnoses.

    Figure2

    Ideal posture for working at a computer terminal.

    Psychological aspects

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    Some patients' symptoms seem to be exaggerated and disproportionate to the physical signs. A history of involvement in medicolegal proceedings may be obtained. While the possibility of missed pathology must always be borne in mind, examination may reveal inappropriate physical signs.

    If a patient has been off work for many months the prognosis is poor; the longer people are off work with low back pain the less likely they are to work again. The reasons for this are unclear but have as much to do with psychological processes as organic pathology. The concept of learned illness behaviour is popular and may explain the persistence of symptoms of chronic unremitting back pain in patients in whom an organic cause cannot be found. This syndrome probably has links with other syndromes such as fibromyalgia and chronic fatigue syndrome.

    Figure3

    Return to work as a function of time away from work because of back pain.

    Investigations

    Radiographic evidence of disc infection or vertebral collapse occurs late in the course of a disease, and blood tests are probably a better initial screen for systemic disease

    Blood tests

    A blood count, erythrocyte, sedimentation rate, and biochemical screen (calcium, phosphate, and alkaline phosphate) should be performed when a systemic cause for back pain is suspected. Testing for prostate specific antigen is useful if prostatic malignancy is suspected.

    Radiological investigation

    Plain radiographs of the lumbar spine are rarely helpful, particularly when taken early in the course of an episode of back pain, and should be performed only if systemic disease is suspected.

    Bone scans are helpful in cases of suspected malignancy and may be abnormal in metabolic bone disease and ankylosing spondylitis.

    Other imaging techniques

    These should be performed only when initial conservative treatment has failed and surgery is being considered.

    Computed tomography is the method of choice for showing bony abnormalities such as bone destruction due to malignancy, infection, or spinal canal stenosis. It can also help in revealing lesions of discs and other soft tissue.

    Magnetic resonance imaging is still not widely available but is the investigation of choice for showing lesions of soft tissues, including lumbar disc lesions and tumours.

    Radiculography was until recently the standard method for investigating lumbar disc lesions. It is now used only when the level of the lesion is uncertain and magnetic resonance imaging is not available.

    Discography is a specialist investigation and may help to identify patients who would benefit from surgical fusion of the spine.

    Electromyography

    A segmental electromyograph may help to confirm the presence of nerve root degeneration if radiological evidence of abnormal anatomy is not conclusive.

    Figure4

    Computed tomogram showing malignant infiltration of lower thoracic vertebra.

    Treatment

    Treatment should be given early, with the aim of stopping the problem from becoming chronic.

    Bed rest should be kept to a minimum,and early mobilisation should be encouraged

    Bed rest

    Bed rest has been the main treatment for all forms of acute back pain for many years, with recommendations varying from a few days to over six weeks. The few satisfactory trials that have been published suggest that bed rest for two or three days has the same or greater benefit than longer periods of rest and that shorter bed rest leads to an earlier return to work. Slightly longer periods of rest may be justified for sciatica.

    Elements of a back school

    Session 1—Principles of anatomy of the spine

    Session 2—Applied body mechanics and posture

    Session 3—Ergonomics

    Session 4—Relaxation techniques and exercises

    Treatment of low back pain

    Patient education and exercise—Reassuring patients, giving them appropriate information, and advising them on posture and exercise programmes are important. These measures are most effective when given as part of a structured programme such as a back school.

    Back schools are effective for treating acute back pain. The concept of back schools was developed in Sweden and is based on a series of four sessions, each lasting an hour. Treatment is in groups so that several patients may be treated in one session by a single therapist with no need for specialist facilities. Patients can also benefit from talking with fellow sufferers.

    Manipulation has been the subject of many studies, with conflicting results. Manipulation seems to be effective in the first three weeks after the start of acute back pain and gives quicker relief of pain, but after three weeks it may have little advantage over natural recovery. The most effective method is unknown, but physiotherapists, chiropractors, and osteopaths, who use a variety of techniques, all seem effective. Manipulation should not be used with patients with sciatica and evidence of nerve root entrapment as it may make the root lesion worse.

    Figure5

    Effect of manipulation on recovery from acute back pain.

    Treatment of sciatica

    Traction—Continuous or intermittent traction remains a popular treatment for patients suffering from sciatica, though recent studies have not consistently confirmed its benefit.

    Epidural injections of local anaesthetic and depot preparations of corticosteroid may speed recovery from sciatica. Both the caudal and lumbar routes ae used. Depot corticosteroid preparations are not licensed for use in the epidural space, but serious adverse reactions are rare.

    Interventional treatments—For patients with symptoms of sciatica lasting more than six weeks despite conservative treatment and in whom the prescence of a disc protrusion is confirmed, surgical or chemical removal of the nucleus of the disc should be considered. The success rates for these techniques are 70-80% at one year after treatment, but the rates tend to fall with time, particularly for some surgical techniques.

    Interventional techniques for treating sciatica

    Chemonucleolysis—intradiscal injection of proteolytic enzyme

    Percutaneous discectomy—by automated nucleotome or laser

    Microdiscectomy

    Conventional discectomy

    Chronic low back pain

    Once back pain has been established for more than a year the prognosis is poor. Lesions that might be amenable to surgery, such as disc protrusion or spondylolysis, must be excluded. Patients may be referred to a pain clinic for local injections of corticosteroid or cryotherapy to facet joints or sclerosant injections into ligaments, but the success of these procedures for chronic pain is low.

    The main aim of treatment should be to help patients to come to terms with their pain and to accept that they can do much themselves to relieve their symptoms. This can be achieved with help from intensive rehabilitation programmes or “schools for bravery,” which are available in specialist centres. Treatment, carried out either on a day case basis or as an intensive three to four week inpatient programme, combined physical and psychological approaches to managing back pain.

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