Incidence

Low back pain (LBP) is one of the most frequent symptoms evaluated in the practitioner's office. In fact, LBP is one of the top ten reasons for outpatient visits in the United States (1). Over 60% of adults suffer from at least one episode of LBP during their lifetime (2). Approximately 85% of those who experience LBP for more than two weeks will seek medical care (3).

The direct and indirect cost for the management and treatment of LBP ranges from $20 billion to $100 billion annually (4). Ten percent of patients suffering from LBP are responsible for 80% of its economic costs (5). It is the most common reason cited for disability for people under the age of 45 (6). Nevertheless, symptoms of lower back pain resolve spontaneously in 90% of the sufferers within two months, regardless of treatment, although symptoms may recur in approximately 50% within a year (7). The key to the appropriate management of LBP lies in identifying patients at risk for a serious underlying disorder, while maintaining a cost-effective approach to the workup and treatment of the majority of LBP sufferers.

Clinical Evaluation

For most patients presenting with LBP, physicians can exclude serious underlying 
systemic illness, rule out the need for surgery, and initiate therapy based on a careful history and physical exam (8).

Four key questions will help to guide the initial evaluation:

1. Is there a serious systemic disease causing the pain?
2. Has the patient had a significant trauma?
3. Is there neurologic compromise that might require surgical evaluation?
4. Is there social or psychological distress that may amplify or prolong pain?
   

Acute back pain is rarely the result of systemic causes. For example, malignant neoplasm is the most common systemic disease that affects the spine, yet it accounts for less than one percent of all episodes of LBP (9). Nevertheless, certain "red flag" findings on the history or physical examination point to the possibility of underlying malignancy, infection, fracture or inflammatory disease (Table I).

TABLE I

Cauda equina syndrome (bowel or bladder changes, saddle anesthesia, bilateral lower extremity motor deficits) is a rare neurologic finding that may require immediate surgery. Its prevalence among patients with LBP is 0.0004 (9). Neurologic findings, such as diminished reflexes and sensory changes, may not warrant immediate surgical intervention and often improve with conservative management. Surgery is necessary only if these symptoms persist or progress (3).

Management of Low Back Pain

Approximately 90% of patients with low back pain will improve within one month, regardless of how they are managed (10,11). Although 85% of the time the cause of back pain is never determined (5), the physician can provide reassurance as to the benign and self-limited nature of LBP. He/she can also explain the likely pain mechanisms, rule out serious disease, and reassure the patient that the prognosis is positive. The most appropriate way to manage non-emergent LBP is conservatively.

At one time, the pervasive standard of LBP care was to use extended bed rest, but not any longer. According to the Agency for Health Care Policy and Research (AHCPR) guidelines, in lieu of bed rest, a carefully chosen exercise program will generally improve an individual's function (10). This is particularly effective for a patient without neurologic deficit. Typically, after two to three days of bed rest, patients should be encouraged to walk regularly. Once the acute episode subsides, patients can begin a program of aerobic conditioning. More rigorous conditioning improves muscle endurance, thus minimizing the likelihood of subsequent back strain and pain. Spinal manipulation can be useful in patients with acute low back pain and no progressive or severe neurologic deficits or radiculopathy, if used within the first month of symptoms (10,12).

Chronic pain is defined as pain lasting more than three months. Patients with chronic pain can often regain function by participating in a specialized program that includes stretching, flexion, or extension exercises. A formal, structured pain management program may also be beneficial.

Medications used in a conservative treatment plan may include analgesics, muscle relaxants, and nonsteroidal anti-inflammatory medications. Narcotic analgesics may be appropriate for acute severe pain, but not for chronic pain. Chronic pain or depression may benefit from antidepressants. In addition, psychological evaluation may be indicated in patients with symptoms that are inconsistent or not compatible with normal physiology.

Use of Diagnostic Imaging

Diagnostic imaging studies should not be ordered as part of a routine workup of LBP. Initial management of uncomplicated LBP generally consists of a trial of conservative therapy as noted above. When therapy fails or a serious underlying condition is suspected based on medical history and physical exam, diagnostic imaging may provide useful information and referral to a subspecialist may be indicated. Patients with a history of prior spine surgery may warrant early referral to an orthopedic or neurosurgical spine specialist. 

For the majority of patients with uncomplicated LBP, imaging studies are not indicated in the first 4-6 weeks (8). Imaging studies are indicated only when the results of such studies will result in a change in patient management (13). In most instances, only one imaging study is needed for an accurate diagnosis. By choosing the best test initially, physicians can develop and implement an appropriate treatment plan more effectively. 

Diagnostic Imaging Pearls

Because the results of imaging studies can be misleading, they must always be interpreted in the context of the clinical picture. Consider these facts prior to ordering diagnostic imaging studies as part of a workup for low back pain:

• 90% of patients with low back pain will become asymptomatic within two months, regardless of treatment (although symptoms may recur at a later time) (2,5).
• Over 50% of patients with sciatica recover within 6 weeks (14).
• Only one in 2,700 lumbosacral (LS) spine films will reveal a finding not suspected on clinical evaluation (10).
• 90% of plain films performed on patients over the age of 50 with LBP will show abnormalities that are attributable to aging and have no bearing on treatment (2).
• 35% of CT scans of the LS spine in asymptomatic patients reveal abnormal findings (including herniated disks) (15).
• In asymptomatic patients > 40 years old, 50% of CT scans show abnormalities, most frequently herniated disks, spinal stenosis and facet arthropathies; and in those < 40, 19% show herniated disks (15).
• In asymptomatic patients > 60 years old, 90% of lumbar MRIs show disc degeneration and 57% show disc herniations or spinal stenosis; in asymptomatic patients < 60 years old, almost 25% show disc herniations or spinal stenosis (8,13). 

Lumbar Roentgenography

Lumbosacral spine x-rays are not routinely indicated in the evaluation of acute low back pain. Routine films may generate unnecessary costs, while failing to significantly impact patient management. In addition, there is a high incidence of abnormal findings on plain films in asymptomatic individuals and the films are subject to significant intra- and interobserver interpretive variability (16,17,18,19, 20). Lumbar spine roentgenography is also estimated to be the largest source of gonadal irradiation in the United States (5). Lumbosacral x-rays are, therefore, indicated in selected cases and to confirm suspicion of a bony lesion when findings are likely to impact patient management (5,17) (Table II).

Table II

*Sl joint X-rays

Spine films may also be indicated in patients who fail to improve with conservative therapy. Since 80% to 90% of episodes of acute mechanical pain improve within weeks, those that do not are more likely due to infection, neoplasm, or inflammatory spondylitis. When appropriate, further workup such as laboratory testing or other imaging techniques may reveal systemic disease, such as abdominal aortic aneurysm, gastrointestinal or renal disease, which may manifest as lower back pain.

Diagnostic imaging costs can be significantly reduced by decreasing the number of views obtained with each lumbar spine examination. Studies have shown that oblique views and the coned lateral view of L5-S1 are unnecessary for routine purposes and that antero-posterior and lateral views are sufficient (10,13). Oblique films may be useful to look for active spondylolisthesis in an athlete with low back pain and nondiagnostic AP-lateral films.

MRI and CT Scan

In general, MRI is the study of choice to evaluate the nerve roots and bone marrow (10,11,20,21,22) (Table III).

Table III

In general, CT scans are the preferred study for imaging the spine when looking for bony abnormalities (11,20,21,23) (Table IV).

Table IV

The false positive rate for both computerized tomography (CT) and magnetic resonance imaging (MRI) is high, and neither study is indicated if the results of the study will not have an immediate impact on patient management (9,10,11,15,20,24). Spinal imaging may actually be misleading; therefore, cross-sectional imaging should be reserved for patients with persistent neurologic abnormalities, despite conservative therapy, who are potential surgical candidates on clinical grounds (3).

Radionucleotide Bone Scan

Bone scanning is a nonspecific yet sensitive study that may be useful in evaluating patients with suspected infectious or neoplastic disease of the spine. It may detect such lesions earlier than plain films and may be indicated if plain films are nondiagnostic and the patient has symptoms such as weight loss, fever, elevated ESR and/or a prior malignancy (5). The AHCPR guidelines indicate that a positive bone scan suggesting one of these conditions or an occult fracture will usually need to be confirmed by using other diagnostic procedures (10). If the physician plans to perform more specific diagnostic imaging procedures such as CT scanning or MRI anyway, radionucleotide bone scanning may not be necessary.

There are several indications for bone scan in patients with low back pain (10,11,21,23) (Table V):

Table V

*Consider SPECT

Myelogram/CT Myelogram

These tests are invasive and place the patient at risk for complications (25). They are reserved for special situations for preoperative planning (2,13,20,25) (Table VI).

Table VI

Summary

Low back pain is a common presenting complaint seen in practitioner offices. A conservative approach to management, including limited bed rest, appropriate use of pain medications or muscle relaxants, and a progressive exercise program, will provide relief in the vast majority of patients. The use of diagnostic imaging may have a role in patients with a specific history, selected signs and symptoms, or in those who do not respond to conservative management.

We would like to acknowledge the editorial assistance of:

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