A Conservative Approach to Acute Low Back Pain

Pointing out that 90% of patients with low back pain are suffering from a benign condition that will resolve in four to six weeks with conservative treatment, the author lays out an approach to history-taking and examination that he hopes will correct physicians' "tendency to overreact" to the complaint.

By Robert N. Schwendimann, MD

Dr. Schwendimann is associate professor of clinical neurology, Louisiana State University Health Sciences Center, Department of Neurology, Shreveport, Louisiana.

Acute low back pain is a symptom that many of us have experienced at one time or another. I have had recurrent problems with my lower back for the past 40 years, dating back to when I played football in high school. Though most of the pain I have experienced is musculoskeletal, I have also had episodes of radicular pain and sciatica associated with mild sensory symptoms from nerve root irritation. I have been able to manage every episode so far with conservative treatment, and I am free of pain most of the time. After one of the most severe flare-ups of pain, however, I underwent magnetic resonance imaging of my lower back that showed significant degenerative disease, although the findings did not correlate well with my clinical symptoms.

My personal experience with acute low back pain has led me to alter my approach to patients who have the same problem. I know from my own experience that most attacks of acute low back pain are caused by benign conditions and that symptoms will usually resolve with time and conservative treatment.

Acute low back pain is a problem that affects a large percentage of the population in the United States. There is a yearly prevalence of symptoms in 50% of working-age patients and a lifetime prevalence of 80% in the general population. Out of all these people, 15% to 20% seek medical attention, making acute low back pain one of the most common reasons for visits to a doctor's office. Fortunately, because benign conditions are the most frequent cause of most back problems, about 90% of affected patients recover in four to six weeks.

Despite these excellent odds for recovery, back pain is the most common cause of disability in patients under 45 years of age. About 1% of the working population is totally disabled because of problems related to low back pain. The monetary impact of caring for these patients is substantial in terms of lost working hours and the cost of medical treatment.

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Tendency to Overreact

There appears to me to be a tendency for physicians to overreact in evaluating the patient with acute low back pain. This may be related to a genuine concern about overlooking a serious underlying condition that could be causing the pain. There may also be concerns about litigation and disability claims that may arise in cases of accidental personal or work-related injuries. These concerns can lead to unnecessary and expensive x-rays and imaging procedures.

The Agency for Health Care Policy and Research (AHCPR) has established guidelines to help the clinician with the initial evaluation of the patient with acute low back pain. These guidelines advocate a focused medical history and physical examination that will help identify those patients with potentially serious spinal conditions, those patients with sciatica, and those patients with nonspecific back symptoms. The guidelines are based on available evidence about outcomes and are directed toward helping patients recover from their acute symptoms and educating them about prevention and treatment of future problems.

The benign conditions that are the most common cause of acute back pain include lumbar strains and sprains and degenerative disease of the intervertebral disks and facet joints. In many patients, a definitive anatomical diagnosis is not possible. During the initial evaluation, however, the examining physician should focus on the likelihood of the following serious conditions being present: compression fractures (4% of patients), spondylolisthesis (3%), malignancy (0.7%), ankylosing spondylitis (0.3%), and vertebral osteomyelitis (0.1%). It is also important to keep in mind that in 2% of patients, acute low back pain is related to disease of the pelvic and abdominal organs and vascular structures.

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Red Flags to Look For

The AHCPR guidelines identify "red flags" (see table at below) that are clues to the presence of one of these more serious conditions. These include a history of trauma, history of cancer, patients more than 50 years of age, history of symptoms suggesting infection, and history of back pain that worsens in the supine position or at night. Progressive muscular weakness, sensory loss, or loss of bladder and bowel function can be the result of various pathologic processes causing a cauda equina syndrome. Red flags such as major motor weakness in the legs may also be identified on physical examination.

The risk of compression fractures increases significantly with major trauma from a serious motor vehicle accident or a fall from a height. Even minor trauma or strenuous lifting can result in compression fractures in an older patient who is at increased risk because of osteoporosis.

Metastatic disease as the cause of low back pain should be given prime consideration in any patient with a history of cancer. About 90% of patients with metastatic disease involving the spine complain of back pain. Cancers of the lung, breast, prostate, kidney, and gastrointestinal tract, as well as lymphoma and melanoma, frequently metastasize to the spine. Multiple myeloma is the most common primary neoplasm involving the spine, though it occurs much less often than spinal metastatic disease. Patients who are more than 50 years of age, patients with unexplained weight loss, patients with back pain unrelieved by rest in the supine position, and patients with nocturnal back pain should all undergo further investigation for neoplastic disease.

Fever associated with tenderness over the spine is a red flag for infection as a possible cause of acute low back pain. Suspicion would be heightened if the patient has had a recent infection, particularly a urinary tract or skin infection. Intravenous drug users and immunosuppressed individuals are at higher risk of having infection as the cause of acute low back pain.

The patient with cauda equina syndrome often has evidence of bilateral radiculopathy with so-called saddle anesthesia in the perineum and perianal region. Urinary retention, urinary incontinence, and evidence of progressive neurologic deficits in the lower extremities, including weakness and sensory loss, are red flags that require further investigation.

As noted earlier, there may also be important non-spinal causes of acute low back pain. Diseases of the pelvic organs such as prostate cancer, pelvic inflammatory disease, and endometriosis, as well as renal pathology and gastrointestinal conditions like pancreatitis, often cause acute pain in the lower back. Back pain may also occur as a result of abdominal aortic aneurysm and aortic dissection.

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Open-Ended Questions

When taking a history from a patient with acute low back pain, the clinician should ask open-ended questions about the location and radiation of the pain, associated sensory changes, muscular weakness and stiffness, aggravating factors (such as standing, sitting, weight-bearing, coughing, or straining), as well as what limitations on activity are caused by the pain. Questions about bladder, bowel, and sexual function are essential.

The physical examination must include general observations of the patient and a regional back examination. Watching the patient walk is mandatory. Is there a limp? Is there loss of the normal lumbar lordosis? Is there a pelvic tilt or a reactive scoliosis? When the back is examined manually, is there point tenderness or evidence of paraspinous muscle spasm? These observations and findings are not specific for any diagnosis, but they may be helpful when considering the possible presence of a fracture or vertebral infection.

The neurologic exam should focus on any abnormality that might be secondary to pathology affecting the L5 and S1 nerve roots, since lumbar radiculopathy affects these nerve roots more than 90% of the time. Having the patient walk on his or her toes tests the S1 muscles primarily. Walking on the heels mainly tests the L5 muscles. Getting up from a sitting position mainly tests the L4 musculature.

Tests for muscle weakness include assessing the strength of thigh extension (quadriceps, L4 root), dorsiflexion of the great toe (extensor hallucis longus, L5 root), and plantar flexion of the great toe and foot (S1 root). A hypoactive or absent knee jerk suggests involvement of the L4 root. Similar changes of the ankle jerk point to S1 root pathology. There are no reflex tests that can help suggest L5 root involvement.

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Sensory Examination

The sensory examination is equally important because sensory complaints are common in radiculopathy. Assessment of pinprick sensation over the medial lower thigh (L4 root), over the lateral aspect of the calf (L5 root), and over the lateral aspect of the foot and posterior calf (S1 root) is particularly useful with localization. A chart of the dermatomes may be helpful during the sensory examination (see illustration below).

Patients with symptoms suggesting radiculopathy may also have positive findings on straight leg raising tests of sciatic tension (Lasègue's tests), performed with the patient in the supine position. The extended limb is first raised or flexed at the hip. Worsening of pain below the knee with flexion at the hip at an angle of 70 degrees or less is a positive test result. The pain may be aggravated further by dorsiflexion of the ankle.

A positive straight leg raising test result suggests involvement of the L5 and S1 nerve roots, most often from disk herniation. Crossover pain produced by raising the opposite, asymptomatic leg is an even stronger sign of radiculopathy.

The straight leg raising tests can also be performed with the patient in a sitting position by extending the leg. I find it helpful to perform these tests with the patient in both the supine and sitting positions to compare responses. Failure to elicit a similar type of pain with the patient sitting may be a sign of malingering.

A rectal examination and sensory examination of the perineum and perianal area are absolutely necessary, particularly when cauda equina syndrome is suspected. Assessment of anal sphincter tone during a digital rectal examination must be performed. A patient may have poor voluntary contraction of the anal sphincter and yet have no complaint about bowel function and control.

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Diagnostic Studies

Identifying any red flags on either the history or the neurologic exam will lead the examining physician to make informed decisions about further diagnostic studies. Plain x-rays of the lumbosacral spine are indicated when there is suspicion of fracture, tumor, or infection, and they may aid in identifying anatomic defects. Helpful laboratory studies include complete blood count with differential, urinalysis, and erythrocyte sedimentation rate. The latter test is a sensitive but nonspecific indicator of underlying disease caused by infection or neoplasm.

Positive findings on these screening examinations often lead to more sophisticated studies like radionuclide bone scans or computed tomography (CT) or magnetic resonance imaging (MRI) of the spine. These studies are more sensitive and specific in identifying pathology but are also more expensive. Referral to a surgical consultant for possible interventional surgery is necessary in cases of cauda equina syndrome or other evidence of spinal cord compromise.

In the absence of any red flags on the history or neurologic examination, initial care includes patient education about the findings and assurance that full recovery is quite possible. The patient with sciatica, however, may require more time to recover than the patient with pain localized to the lower back. Initial attempts at treatment include pain relief and appropriate supportive care. Changes in activity to help avoid continued back irritation could include a brief change in activity at work, but the patient should be encouraged to keep on working and to engage in his or her usual activities. Bed rest for more than a few days is not helpful; in fact, long periods of bed rest often contribute to further debility.

Adequate pain relief can be attained with the use of analgesic drugs. Acetaminophen is the safest analgesic, but aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), and the COX-II inhibitors are also effective in patients who can tolerate them. Various muscle relaxants are no more effective than these other drugs. Habit-forming analgesics should be avoided because they are no more effective than acetaminophen, aspirin, NSAIDs, and COX-II inhibitors. These drugs can also cause disorientation, decreased reaction times, and clouded judgment. They also have the potential for misuse and for causing drug dependence.

Treatment with corticosteroids, tricyclic antidepressants, epidural injections, nerve blocks, and stimulator devices have not been shown to be effective in the patient with acute low back pain. Generally, physical methods of treatment like traction, massage, and acupuncture have no proven benefit. There is evidence that short courses of treatment using manipulation may be helpful. The use of heat and cold therapy has no proven benefits, but I still use ice followed by a heating pad when my own back pain flares up because it alleviates the pain.

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Effective Treatments

Conservative management and time are effective treatments for the vast majority of patients with acute low back pain. Recovery usually occurs within four weeks of onset. The patient who does not respond in 6 to 12 weeks must be reevaluated using the same criteria employed in the initial evaluation. A review of the history may help in identifying symptoms that require further diagnostic tests. The neurologic examination should be repeated and the results compared to the results of the first examination. The physician may want to order laboratory tests and x-rays based on this new information.

Electrodiagnostic tests (such as nerve conduction studies and electromyelography) can be helpful two to three weeks post-injury in cases of suspected radiculopathy in which the level of involvement is not obvious. Both nerve conduction studies and needle electromyography are necessary for adequate evaluation of radiculopathy. Special tests like the H-reflex may provide additional information, particularly in patients with S1 root symptoms. If the level of nerve root irritation is obvious on examination, then an MRI or referral to an orthopedic surgeon or neurosurgeon for consideration of other diagnostic tests or surgical intervention is appropriate. Keep in mind that abnormalities on MRI examinations are common; it is always necessary to ensure that MRI findings correlate with the patient's signs and symptoms.

Decisions about surgery are, of course, best left to the surgeon and patient. Surgery may be an option for the patient with severe, disabling sciatic pain or progressive symptoms of sciatica, or when there is strong evidence of specific nerve root irritation and disk herniation at the corresponding level confirmed by an imaging study. There are many patients for whom surgery is indicated who may still recover without surgical intervention and with continued conservative treatment.

The older patient with spinal stenosis and symptoms of neurogenic claudication (pain or neurologic deficit in the legs induced by walking) may benefit from a posterior decompressive laminectomy. Surgical intervention is not usually necessary during the first three months of symptoms. If the patient with lumbar stenosis tolerates daily activity well and does not develop bowel or bladder dysfunction, surgical intervention is not usually necessary.

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Focus on Physical Conditioning

After the diagnostic or surgical procedures have been completed, the focus should shift to improving the patient's physical conditioning through exercise programs. Low-stress aerobic activities to improve stamina and exercises to strengthen specific trunk muscles as well as poorly conditioned back muscles are helpful. Courses in proper lifting techniques and improving biomechanics may be useful in avoiding future problems.

The patient who is unresponsive to an exercise program and other conservative treatments and who has no identifiable red flags may have psychosocial issues that should be investigated. These include job dissatisfaction, pending litigation or legal entanglements, claims for compensation and disability, depression, and substance abuse.

The guidelines referred to in this article are available via the Internet at the National Library of Medicine HSTAT site (http://text.nlm.nih.gov). These guidelines, which can be easily downloaded, contain helpful charts, further information regarding evidence-based treatment of acute low back pain, and algorithms for making decisions about proper management. Patient information is also available at this Web site.

Suggested Reading Anderson GBJ, et al.: A comparison of osteopathic spinal manipulation with standard care of patients with low back pain. N Engl J Med 341:1426, 1999. Bigos S, et al.: Acute Low Back Problems in Adults. Clinical Practice Guideline No. 14. AHCPR Publication No. 95-0642. Rockville, MD: Agency for Health Care Policy and Research, Public Health Service, U.S. Department of Health and Human Services. December 1994. Deyo RA, et al.: What can the history and physical examination tell us about low back pain? JAMA 268 (6):760, 1992. Deyo RA: Low back pain. Sci Am 279:44, 1998. Deyo RA and Weinstein J: Primary care: low back pain. N Engl J Med 344: 363, 2001. Malmivarra A, et al.: The treatment of acute low back pain: bed rest, exercises, or ordinary activity? N Engl J Med 332(6):351, 1995. Swenson R: Differential diagnosis: a reasonable clinical approach. Neurological Clinics 17(1):43, 1999. Wilbourn AJ and Aminoff M: AAEM Minimonograph #32: The electrodiagnostic examination in patients with radiculopathies. Muscle & Nerve 21:1612, 1998.