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Researchers study the causes of low back pain, use of imaging to identify herniated disks, and cancer in back pain patients

About two-thirds of adults suffer from low back pain at some time. Doctors differ widely in how they care for patients with low back pain, with evidence of excessive imaging and surgery for the problem. In most cases of low back pain, patients recover within a few weeks of the onset of symptoms. Although the more worried among us may fear cancer with back pain, less than 1 percent of primary care patients with low back pain have spinal cancer. Three studies supported by the Agency for Healthcare Research and Quality recently examined approaches to the diagnosis and treatment of various causes of back pain, ranging from disk herniation to spinal cancer.

The first study (AHRQ grant HS09804) provides a general overview of the causes, diagnosis, and treatment of low back pain. The second study (AHRQ grants HS08194 and HS09499) suggests imaging approaches that can distinguish age-related from more problematic intervertebral disk changes. In the third study (AHRQ grants HS06664, HS06344, and HS08194) the authors recommend a strategy for finding cancer in primary care outpatients with low back pain.

Deyo, R.A., and Weinstein, J.N. (2001, February). "Low back pain." New England Journal of Medicine 344(5), pp. 363-370.

These researchers review the causes, diagnosis, and treatment of low back pain. They point out that for patients with nonspecific low back pain, a precise anatomically based diagnosis is often impossible, which leads to various imprecise diagnoses. The fact that low back pain often resolves on its own may partially explain the proliferation of unproved treatments that may seem to be effective. X-rays are useful in only a minority of patients, and use of more advanced imaging should be reserved for potential candidates for surgery. Computed tomography and magnetic resonance imaging are more sensitive than plain x-rays for the detection of early spinal infections, cancer, herniated disks, and spinal stenosis. The role of imaging in other situations is limited because of the poor association between low back pain symptoms and anatomic findings.

Bed rest is not recommended for the treatment of low back pain or sciatica, and a rapid return to normal activities is usually the best course. Back exercises are not useful for the acute phase, but they do help to prevent recurrences and treat chronic pain. Spinal manipulation and physical therapy are alternative treatments for symptomatic relief among patients with acute or subacute low back pain, but their effects are limited. Surgery is appropriate for a small proportion of patients with low back symptoms, such as those with sciatica.

Patients with suspected disk herniation should be treated nonsurgically for at least a month. Narcotic analgesics may be needed for pain relief, but they should be used only for limited periods. Bed rest does not accelerate recovery, but epidural corticosteroid injections offer temporary symptomatic relief for some patients. Diskectomy has produced better pain relief than nonsurgical treatment over a period of 4 years, but it's not clear whether there is any advantage after 10 years. Evidence regarding nonsurgical therapy for spinal stenosis is sparse. Use of an exercise bicycle or walking is recommended, with brief rest when pain occurs. Analgesics, nonsteroidal antiinflammatory drugs, physical therapy, and epidural corticosteroids may be useful, but there are no data from clinical trials. Even with successful surgery, symptoms often recur after several years.

Jarvik, J.G., and Deyo, R.A. (2000, January). "Imaging of lumbar intervertebral disk degeneration and aging, excluding disk herniations." Radiologic Clinics of North America 38(6), pp. 1255-1266.

These authors review imaging studies of the normal intervertebral disk, how it degenerates with aging, and the relationship of various aspects of disk degeneration to low back pain. They conclude that most degenerative disk changes are age-related, and only rarely are these disk changes helpful in the diagnosis of low back pain. Several studies showed that as the disk ages, it becomes less hydrated, prone to different types of tears, and progressively loses the capacity to absorb and transmit compressive loads to the vertebral column. With tear-related loss of integrity, the disk begins to expand outward into bulges.

Computerized tomography (CT) can reliably and accurately depict disk bulging, herniation, calcification, and vertebral endplate sclerosis. However, CT cannot distinguish soft tissue structures and has a limited field of view. Magnetic resonance imaging (MRI) has superior contrast discrimination that facilitates the evaluation of the internal disk structure. One study used MRI to examine the natural history of anatomic changes of the lumbar spine. It showed that common imaging findings—such as disk dehydration, disk narrowing, and disk bulges—were all strongly associated with age and nearly ubiquitous by the fifth and sixth decades of life.

Findings not significantly associated with age but linked to past pain occurred uncommonly in the sample. Such findings include disk extrusions, nerve root compromise, and moderate or severe stenosis. When these less common findings fit with the clinical picture, doctors can be more confident that they are related to the patient's symptoms. The researchers conclude that in isolation an imaging finding of disk degeneration may represent part of the aging process and in the absence of extrusion is of only modest value in diagnosis or treatment decisions.

Joines, J.D., McNutt, R.A., Carey, T.S., and others. (2001, January). "Finding cancer in primary care outpatients with low back pain." Journal of General Internal Medicine 16, pp. 14-23.

These researchers recommend a specific imaging strategy for low back pain patients who have a history of cancer or are otherwise at greater risk for spinal cancer. Early diagnosis and treatment of spinal metastasis are needed to prevent complications, which may include pain, pathologic fracture, weakness, sensory loss, paralysis, and bowel or bladder dysfunction. The researchers compared strategies that differed in the use of clinical findings, erythrocyte sedimentation rate (ESR), and plain x-rays prior to imaging and biopsy. They used estimates of disease prevalence and test characteristics taken from the literature. Costs reflected Medicare reimbursement for the tests and procedures employed.

The researchers recommend a strategy using MRI—or bone scan followed by MRI—for patients who have a clinical finding that raises the risk of spinal cancer (history of cancer, age 50 years or older, weight loss, or failure to improve with conservative therapy) in combination with either an elevated ESR (50 mm or more per hour) or a positive x-ray. As an alternative, they recommend imaging directly without additional tests for those patients with a history of cancer.

In the baseline analysis, using MRI as the imaging procedure prior to a single biopsy and an ESR cutoff point of 20 mm/hr, strategies ranged in sensitivity from 0.40 to 0.73, with corresponding diagnostic costs of $14 to $241 per patient and average cost-effectiveness ratios of $5,283 to $49,814 per case of cancer found. Use of a higher ESR cutoff point (50 mm per hour) resulted in lower costs and fewer unnecessary biopsies for strategies that used ESR. Imaging with MRI or bone scan followed by MRI resulted in fewer unnecessary biopsies than imaging with bone scan alone. Cancer prevalence was an important determinant of cost-effectiveness.

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