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Am Fam Physician. 2000;61(6):1779-1786

See related patient information handout on acute low back pain, prepared by Courtney Brooks, a medical editing clerkship student at Georgetown University Medical Center.

Acute low back pain is commonly encountered in primary care practice but the specific cause often cannot be identified. This ailment has a benign course in 90 percent of patients. Recurrences and functional limitations can be minimized with appropriate conservative management, including medications, physical therapy modalities, exercise and patient education. Radiographs and laboratory tests are generally unnecessary, except in the few patients in whom a serious cause is suspected based on a comprehensive history and physical examination. Serious causes that need to be considered include infection, malignancy, rheumatologic diseases and neurologic disorders. Patients with suspected cauda equina lesions should undergo immediate surgical investigation. Surgical evaluation is also indicated in patients with worsening neurologic deficits or intractable pain that is resistant to conservative treatment. The current recommendation is two or three days of bed rest for patients with acute radiculopathy. The treatment plan should be reassessed in patients who do not return to normal activity within four to six weeks.

Acute low back pain is the fifth most common reason for all physician visits.1 Even though this ailment usually has a benign course, it is responsible for direct health care expenditures of more than $20 billion annually and as much as $50 billion per year when indirect costs are included.2

In the United States, approximately 90 percent of adults experience back pain at some time in life,3 and 50 percent of persons in the working population have back pain every year.4 As many as 90 percent of patients with acute back pain return to work within three months, but many experience symptom recurrence and functional limitations.5

Evaluation of Low Back Pain

In primary care practice, the specific anatomic cause of back pain is often impossible to define, and only a small percentage of patients have an identifiable underlying cause. Fewer than 2 percent of patients have disc herniation.3 Even fewer have a life-threatening disease. Most patients with acute low back pain improve with conservative management and do not require immediate diagnostic studies.

A comprehensive history and physical examination can identify the small percentage of patients with serious conditions that require immediate further evaluation (Table 1). These conditions include infection, malignancy, rheumatologic diseases and neurologic disorders. The possibility of referred pain from other organ systems should also be considered.

Disease or conditionPatient age (years)Location of painQuality of painAggravating or relieving factorsSigns
Back strain20 to 40Low back, buttock, posterior thighAche, spasmIncreased with activity or bendingLocal tenderness, limited spinal motion
Acute disc herniation30 to 50Low back to lower legSharp, shooting or burning pain, paresthesia in legDecreased with standing; increased with bending or sittingPositive straight leg raise test, weakness, asymmetric reflexes
Osteoarthritis or spinal stenosis>50Low back to lower leg; often bilateralAche, shooting pain, “pins and needles” sensationIncreased with walking, especially up an incline; decreased with sittingMild decrease in extension of spine; may have weakness or asymmetric reflexes
SpondylolisthesisAny ageBack, posterior thighAcheIncreased with activity or bendingExaggeration of the lumbar curve, palpable “step off” (defect between spinous processes), tight hamstrings
Ankylosing spondylitis15 to 40Sacroiliac joints, lumbar spineAcheMorning stiffnessDecreased back motion, tenderness over sacroiliac joints
InfectionAny ageLumbar spine, sacrumSharp pain, acheVariesFever, percussive tenderness; may have neurologic abnormalities or decreased motion
Malignancy>50Affected bone(s)Dull ache, throbbing pain; slowly progressiveIncreased with recumbency or coughMay have localized tenderness, neurologic signs or fever

HISTORY

The history and review of systems include patient age, constitutional symptoms and the presence of night pain, bone pain or morning stiffness (Table 2). The patient should be asked about the occurrence of visceral pain, symptoms of claudication and neurologic symptoms such as numbness, weakness, radiating pain, and bowel and bladder dysfunction.

History
Onset of pain (e.g., time of day, activity)
Location of pain (e.g., specific site, radiation of pain)
Type and character of pain (sharp, dull, etc.)
Aggravating and relieving factors
Medical history, including previous injuries
Psychosocial stressors at home or work
“Red flags”: age greater than 50 years, fever, weight loss
Physical examination
Informal observation (e.g., patient's posture, expressions, pain behavior)
Comprehensive general physical examination, with attention to specific areas as indicated by the history
Neurologic evaluation
Back examination
Palpation
Range of motion or painful arc
Stance
Gait
Mobility (test by having the patient sit, lie down and stand up)
Straight leg raise test

It is also important to inquire about the specific characteristics and severity of the pain, a history of trauma, previous therapy and its efficacy, and the functional impact of the pain on the patient's work and activities of daily living. An assessment of social and psychologic factors (e.g., depression) may yield information that affects the treatment plan.

PHYSICAL EXAMINATION

As part of the initial evaluation, the physician should perform a thorough neurologic examination to assess deep tendon reflexes, sensation and muscle strength (Table 2). Peripheral pulses should also be assessed, and the abdomen should be palpated to search for organomegaly. The physician should assess joint and muscle flexibility in the lower extremities, examine the entire spine and assess stance, posture, gait and straight leg raising.

At subsequent visits, further assessment and a comprehensive evaluation can be carried out based on the history and persistence of symptoms. Functional overlay, or signs of excessive pain behavior, should be assessed. Physiologic plausibility and consistency of physical findings should be addressed. “Non-organic” signs of physical impairment have been described (Table 3).68 The presence of three or more of these signs is thought to suggest a nonphysiologic element of the patient's presentation. In this situation, further psychologic testing and/or behavioral intervention may be warranted.

Superficial, nonanatomic tenderness
Pain with simulated testing (e.g., axial loading or pelvic rotation)
Inconsistent responses with distraction (e.g., straight leg raises while the patient is sitting)
Nonorganic regional disturbances (e.g., nondermatomal sensory loss)
Overreaction

LABORATORY TESTS

The comprehensive evaluation may include a complete blood count, determination of erythrocyte sedimentation rate and other specific tests as indicated by the clinical evaluation. In particular, these tests are useful when infection or malignancy is considered a possible cause of a patient's back pain.

RADIOGRAPHIC EVALUATION

Plain-film radiography is rarely useful in the initial evaluation of patients with acute-onset low back pain. At least two large retrospective studies have demonstrated the low yield of lumbar spine radiographs.9,10 In one of these studies, plain-film radiographs were normal or demonstrated changes of equivocal clinical significance in more than 75 percent of patients with low back pain.9 The other study found that oblique views of the spine uncovered useful information in fewer than 3 percent of patients.10

At the first visit, anteroposterior and lateral radiographs should be considered in patients who meet any of the criteria listed in Table 4.

History of significant trauma
Neurologic deficits
Systemic symptoms
Temperature greater than 38°C (100.4°F)
Unexplained weight loss
Medical history
Cancer
Corticosteroid use
Drug or alcohol abuse
Ankylosing spondylitis suspected

MAGNETIC RESONANCE IMAGING AND COMPUTED TOMOGRAPHIC SCANNING

Magnetic resonance imaging (MRI) and computed tomographic (CT) scanning have been found to demonstrate abnormalities in “normal” asymptomatic people.1113 Thus, positive findings in patients with back pain are frequently of questionable clinical significance. In one study, MRI scans revealed herniated discs in approximately 25 percent of asymptomatic persons less than 60 years of age and in 33 percent of those more than 60 years of age.12 Clearly, the presence of abnormalities does not correlate well with clinical symptoms.

MRI uses no ionizing radiation and is better at imaging soft tissue (e.g., herniated discs, tumors). CT scanning provides better imaging of cortical bone (e.g., osteoarthritis). Compared with MRI, CT scanning is less sensitive to patient movement and is also less expensive.

MRI or CT studies should be considered in patients with worsening neurologic deficits or a suspected systemic cause of back pain such as infection or neoplasm. These imaging studies may also be appropriate when referral for surgery is a possibility.

BONE SCINTIGRAPHY

Bone scintigraphy, or bone scanning, can be useful when radiographs of the spine are normal but the clinical findings are suspicious for osteomyelitis, bony neoplasm or occult fracture. However, this technique is unlikely to demonstrate bone changes when radiographs and the erythrocyte sedimentation rates are normal.

PHYSIOLOGIC ASSESSMENT

Electrodiagnostic assessments such as needle electromyography and nerve conduction studies are useful in differentiating peripheral neuropathy from radiculopathy or myopathy. If timed appropriately, these studies are helpful in confirming the working diagnosis and identifying the presence or absence of previous injury. They are also useful in localizing a lesion, determining the extent of injury, predicting the course of recovery and determining whether structural abnormalities (as seen on radiographic studies) are of functional significance.

The physician needs to be aware of the limitations of electrodiagnostic studies. Because the tests depend on patient cooperation, only a limited number of muscles and nerves can be studied. In addition, the timing of the studies is important, because electromyographic findings may not be present until two to four weeks after the onset of symptoms. Hence, electrodiagnostic studies have only a limited role in the evaluation of acute low back pain.

Electrodiagnostic studies may not add much if the clinical findings are not suggestive of radiculopathy or peripheral neuropathy. These tests should not be considered if they will have no effect on the patient's medical or surgical management.

Because electrodiagnostic studies are examiner-dependent, they should ideally be performed by physicians who are specialists in electrodiagnostic medicine.14,15

Management of Acute Low Back Pain

Laboratory and imaging studies, performed as indicated, provide information that can be useful in establishing a diagnosis and developing a treatment plan in the patient with acute back pain (Table 5).

Disease or conditionLaboratory testsRadiographs
Back strainNo abnormalitiesUsually negative
Radiographs may show incidental spondylotic changes.
Acute disc herniationIf testing is timed properly, positive findings for electrodiagnostic studies in the presence of root entrapmentPossibly, narrowed intervertebral disc spaces on radiographs
CT and MRI can reveal level and degree of herniation.
Myelography localizes site of disc herniation and the presence of root entrapment.
OsteoarthritisESR and WBC count plus differential typically normalAsymmetric narrowing of joint space
Sclerotic subchondral bone
Marginal osteophyte formation
SpondylolisthesisNo abnormalitiesAbnormal intervertebral movement on radiographs obtained with spine in flexion and extension
Radiographs may reveal pars defect.
Bone scans can reveal pars defect not visible on radiographs.
Ankylosing spondylitisESR may be elevatedRadiographs of pelvis are positive for sacroiliac joint sclerosis and narrowing.
Mild anemia possible
Positive human leukocyte antigen-B27 assay in 90 percent of affected patientsBone scans are useful for demonstrating increased activity in sacroiliac joints, facets or costovertebral joints.
InfectionElevated ESR; WBC count may be normalRadiographs may show vertebral end-plate erosion, decreased intervertebral disc height, changes indicative of bony erosion and reactive bone formation.
Blood culture or tuberculin test may be positive
Gallium citrate scanning or indium-labeled leukocyte imaging may be positive.
MalignancyAnemiaRadiographs may show bony erosion or blastic lesions.
Increased ESRBone scans are useful for early demonstration of blastic lesions.
Prostate-specific antigen or alkaline phosphatase level may be elevatedCT localizes cortical lesions earlier than radiographs.
MRI is useful for demonstrating soft tissue tumors involving the spinal cord.

If no significant improvement in symptoms is noted after four to six weeks of treatment, the physician should reassess the treatment plan. To avoid misdiagnosis and unnecessary or inappropriate treatments, the physician may then want to refer the patient to a spine specialist.

PHARMACOLOGIC THERAPY

The mainstay of pharmacologic therapy for acute low back pain is acetaminophen or a non-steroidal anti-inflammatory drug (NSAID).16 If no medical contraindications are present, a two- to four-week course of medication at anti-inflammatory levels is suggested.

Adequate gastrointestinal prophylaxis, using a histamine H2 antagonist or misoprostol (Cytotec), should be prescribed for patients who are at risk for peptic ulcer disease.17,18 Two new NSAIDs with selective cyclooxygenase–2 inhibition—rofecoxib (Vioxx) and celecoxib (Celebrex)—recently have been labeled by the U.S. Food and Drug Administration. These agents have fewer gastrointestinal side effects, but they still should be used with caution in patients at risk for peptic ulcer disease.

For relief of acute pain, short-term use of a narcotic may be considered. The need for prolonged narcotic therapy should prompt a reevaluation of the etiology of a patient's back pain.

REST

Previously, bed rest was frequently prescribed for patients with back pain. However, several studies have shown that this measure has an adverse effect on the course and outcome of treatment. One randomized clinical trial found that patients with two days of bed rest had clinical outcomes similar to those in patients with seven days of bed rest.19 The group with a shorter rest period missed 45 percent fewer days of work and presumably avoided the effects of deconditioning and the fostering of a dependent sick role.

The current recommendation is two to three days of bed rest in a supine position for patients with acute radiculopathy. Sitting, even in a reclined position, actually raises intradiscal pressures20 and can theoretically worsen disc herniation and pain.

Activity modification is now the preferred recommendation for patients with nonneurogenic pain. With activity restriction, the patient avoids painful arcs of motion and tasks that exacerbate the back pain.

PHYSICAL THERAPY MODALITIES

Superficial heat (hydrocolloid packs), ultrasound (deep heat), cold packs and massage are useful for relieving symptoms in the acute phase after the onset of low back pain. These modalities provide analgesia and muscle relaxation (Table 6). However, their use should be limited to the first two to four weeks after the injury. The use of deep heat may be subject to a number of restrictions.21

TherapyIndicationsContraindicationsPrescription
Superficial heat (hydrocolloid packs)Analgesia
Reduction in muscle spasm
Increased tolerance for exercise
Impaired sensation, circulation, cognition
Edema
Bleeding diatheses
Apply to affected area for 20 to 30 minutes; inspect skin frequently during therapy; repeat application every 2 hours as needed.
Ultrasound (deep heat)Analgesia
Increased length of periarticular ligaments and tendons
Same as for superficial heat
Never use deep heat near cardiac pacemaker or fluid-filled cavities (e.g., eyes, uterus, testes, laminectomy sites).21
Avoid use of deep heat near open epiphyses, malignancies or joint arthroplasties.21
Apply 0.5 to 2.0 W per cm2 to affected area for 10 to 15 minutes before range-of-motion exercises are performed.
Cold packsAnalgesia
Limitation of edema formation in acute musculoskeletal injury
Impaired sensation, circulation, cognition
History of cold intolerance
Apply to affected area for 20 to 30 minutes; inspect skin frequently during therapy; repeat application every 2 hours for 48 hours after injury as needed.

No convincing evidence has demonstrated the long-term effectiveness of lumbar traction22 and transcutaneous electrical stimulation23 in relieving symptoms or improving functional outcome in patients with acute low back pain. Therapy should emphasize the patient's responsibility for spine care and injury prevention.

CORSETS

The role of corsets (lumbosacral orthoses, braces, back supports and abdominal binders) in the treatment of patients with low back pain is controversial at best.24 Use of a corset for a short period (a few weeks) may be indicated in patients with osteoporotic compression fractures.

EXERCISE

Aerobic exercise has been reported to improve or prevent back pain.25 The mechanism of action is unclear, and the relationship between cardiovascular conditioning and rate of recovery is not universally accepted. Excess weight, however, has a direct effect on the likelihood of developing low back pain, as well as an adverse effect on recovery.26

In general, exercise programs that facilitate weight loss, trunk strengthening and the stretching of musculotendinous structures appear to be most helpful in alleviating low back pain. Exercises that promote the strengthening of muscles that support the spine (i.e., the oblique abdominal and spinal extensor muscles) should be included in the physical therapy regimen. Aggressive exercise programs have been shown to reduce the need for surgical intervention.27

CHIROPRACTIC

Patients with acute or chronic back pain frequently seek chiropractic intervention. The Agency for Healthcare Research and Quality (AHRQ), previously the Agency for Health Care Policy and Research (AHCPR),28 and the Clinical Standards Advisory Group29 acknowledge the potential value of a short course of spinal manipulation in patients with acute low back pain. However, further research is needed to clarify the subgroup of patients most likely to benefit from this intervention.30

PATIENT EDUCATION

It is critical to solicit the active participation of patients in spine care. Successful treatment depends on the patient's understanding of the disorder and his or her role in avoiding re-injury. Many hospitals and large businesses offer programs on back protection. These programs emphasize measures for avoiding spinal injury and review appropriate postures for sitting, driving and lifting. Weight loss and healthy lifestyle classes are also widely available.

PSYCHOLOGIC EVALUATION

Psychosocial obstacles to recovery may exist and must be explored. Studies have shown that workers with lower job satisfaction are more likely to report back pain and to have a protracted recovery.31 Patients with an affective disorder (e.g., depression) or a history of substance abuse are more likely to have difficulties with pain resolution. It is important for the physician to find out whether litigation is pending, because this can often adversely affect the outcome of therapy.32

INDICATIONS FOR SURGICAL EVALUATION

Of all industrialized nations, the United States has the highest rate of spinal surgery (e.g., five times that of Great Britain).33 Studies examining the outcomes of conservative and surgical treatment of back pain have revealed no clear advantage for surgery. In one prospective study of 280 patients with herniated nucleus pulposus diagnosed by myelography,34 the surgical group demonstrated more rapid initial recovery than the medical treatment group. However, after approximately four years, outcomes appeared to be roughly equivalent in both groups; by 10 years, no appreciable differences in outcome were found.

Select groups of patients with acute low back pain should undergo immediate surgical evaluation. Patients with suspected cauda equina lesions (characterized by saddle anesthesia, sensorimotor changes in the legs and urinary retention) require immediate surgical investigation. Surgical evaluation is also indicated in patients with worsening neurologic deficits or intractable pain that is resistant to conservative treatment.

Final Comment

Few randomized, controlled studies or objective unbiased articles are available to help guide the management of patients with acute low back pain. In 1994, the AHCPR published a guideline on acute low back pain management in adults.28 This guideline was severely criticized, especially by physicians who favored a more surgical approach. Further research is clearly needed to better define the optimal approach to this common but vexing problem.

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