Low Back Pain

Stephen Davis

Approach

Low back pain is a common problem with many causes. The differential diagnosis can be grouped into three over-lapping categories: urgent (“red flag”) diagnoses, structural (musculoskeletal) problems, and medical causes (Table 12.5).

History

 The history should include evaluation for “red flag” conditions.

A. Pain characteristics. Assess the nature of the pain, along with the onset and duration of the symptom. Is there any radiating pain, leg weakness, or paresthesia? Pseudoclaudication is suggestive of spinal stenosis. Pain radiating below the knee is more likely to be a true radiculopathy (1). Nerve root compression is highly unlikely without sciatic pain (1). Was the onset after a traumatic event? A seemingly insignificant episode (e.g., a minor fall) may be a “red flag” for fracture in an elderly patient. Are there alleviating or exacerbating factors? Does the pain limit the patient physically or socially? Is there a history of previous back problems or back surgery?

B. Review of systems. Look for associated symptoms that can indicate a “red flag” condition or an underlying medical cause. Gastrointestinal and genitourinary symptoms are particularly important, especially incontinence (Chapter 10.10).

 C. Psychosocial information. Has the patient initiated any new activities? If work-related, assess typical job tasks. Investigate whether the back pain could have any relationship, sexual, or mood implications. Sexual activity can be severely affected simply because of pain, but sexual dysfunction can also result from neurologic abnormalities associated with the cause of the back pain. Back pain is associated with depression and poor sleep patterns. Drug-seeking behavior may be exhibited along with a complaint of back pain. Addiction may have resulted from former or on-going treatment of the pain. Legal issues can complicate the diagnosis and treatment of back pain. Ask the patient whether litigation involving the back pain is under consideration.

Physical examination

Evaluation should be both general and specific. It is prudent to leave the potentially most painful parts of the examination to the end.

 A. General. Examination includes auscultation of the heart and assessment of peripheral pulses and blood pressure. Abdominal examination should focus on possible causes of back pain (Table 12.5). Assess gait.

 B. Neurologic. The lower extremity examination includes motor strength, deep tendon reflexes, sensation, proprioception, and certain functional maneuvers (Table 12.6). Romberg and Babinski reflexes should also be assessed. Rectal examination should assess sphincter tone, which can be compromised in sacral root dysfunction. In the primary care setting, most clinically significant disc herniations will be detected by the following limited examination: dorsiflexion of the great toe and ankle, Achilles reflex, light touch sensation of the medial (L ₄), dorsal (L₅), and lateral (S₁) aspect of the foot, and the straight leg raise (SLR) test (1).

 C. Musculoskeletal. Assess range of motion of the spine and lower extremities. Perform the SLR test passively with the patient supine. Note the angle of leg elevation precipitating pain. A positive test for sciatica is buttock pain radiating to the posterior thigh, and perhaps to the lower leg and foot. Sciatica, with pain and resistance on internal rotation of the hip, can indicate piriformis muscle spasm or strain. The SLR test is usually negative in spinal stenosis (2). Percussion of the spine and upper pelvis helps to identify areas of localized tenderness, as in fracture, metastatic disease, and some rheumatologic conditions. Palpate standard trigger points looking for fibromyalgia. Check for paraspinal muscle spasm. Measure thigh and calf circumferences to look for muscular atrophy.

Testing

 A. Clinical laboratory tests. Testing will be guided by the differential diagnosis as determined by the history and physical examination. If the back pain is felt to be of musculoskeletal origin, no test may be indicated. A urinalysis can help rule out hematuria or infection, if the pain is thought to be urologic or as a result of trauma. If the history suggests a medical problem, the considered diagnoses will determine the laboratory work. Extensive medical workup may be needed for a primary or metastatic malignancy. A calcium level should always be measured to identify a potentially lethal hypercalcemia. Rheumatologic studies may be indicated if a connective tissue disease (e.g., ankylosing spondylitis or rheumatoid arthritis) is suspected. If the pain is thought to be secondary to an urgent or life-threatening condition, have pertinent tests done expeditiously.

 B. Diagnostic imaging. In the absence of “red flags,” lumbar spine films are not indicated for musculoskeletal sounding low back pain of less than 1 month duration (1). Neurologic emergencies (e.g., major spine trauma, cauda equina syndrome) require magnetic resonance imaging (MRI) studies. It is usually unproductive to order an MRI for straightforward lumbar muscular strain or for initial evaluation of simple disc herniation, as the prevalence rate of nonsignificant abnormal findings is high. A bone scan may be helpful when tumor, infection, or occult fracture is suspected. Electromyography may be useful to assess for nerve root dysfunction when symptoms are questionable.

Diagnostic assessment

The most common cause of low back pain in the outpatient setting is musculoskeletal strain. Although temporarily very debilitating, muscle strain can be conservatively treated and usually has few long-term complications. Variations from this basic presentation must be recognized to identify more structurally significant or medically threatening problems. Clues to these other diagnoses, which are found in the history, are reinforced by abnormalities in the physical examination; they are found less often by diagnostic testing.

The following “red flags” suggest possible urgent diagnoses. A history of recent trauma or motor vehicle accident can signify a vertebral fracture or subluxation. Fever can indicate an infection of the spine or pyelonephritis (Chapter 2.6). Recent genitourinary instrumentation or other invasive procedure can precede this presentation. Weight loss, other constitutional symptoms, or pain at rest (or at night) may suggest cancer (Chapter 2.13). Neurologic abnormalities can signify nerve dysfunction or cord compression. Urinary or fecal incontinence or retention, saddle area perineal numbness, or anal sphincter incompetence suggests cauda equina syndrome. A sudden tearing sensation in the back with associated hypotension can be caused by a rupturing abdominal aortic aneurysm.

References

1. Bigos SJ. 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, US Department of Health and Human Services; December 1994.

2. Alvarez JA, Hardy Jr. RH. Lumbar spine stenosis: a common cause of back and leg pain. Am Fam Physician 1998;57:1825–1834.

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Book Source Details

• Book Title: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter
• Author(s): Robert B. Taylor (editor)
• Year of Publication: 2000
• Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2000 Lippincott Williams & Wilkins.

Other Book Chapters Related to Lower back pain

Read excerpts from these other book chapters related to Lower back pain:

Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2008 Williams & Wilkins.

More About Causes of Lower back pain

• Back to symptom: Lower back pain: Introduction (review 78 causes)
• Next Book Extract About Lower back pain: Low Back Pain (Field Guide to Bedside Diagnosis)
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More About This Book: Title: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter Authors: Robert B. Taylor (editor) Publisher: Lippincott Williams & Wilkins Copyright: 2000 ISBN: 0-78172-094-X

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