• 
  

  The diagnostic approach to lower back pain is facilitated by classifying back pain into (1) nonspecific low back pain, (2) back pain associated with radiculopathy, and (3) back pain due to a serious underlying cause.

  
  
• 
  

  It is critical to screen for risk factors associated with serious back pathology as well as identify the presence of neurologic deficits.

  
  
• 
  

  Imaging is indicated in select patients with significant risk factors and/or neurologic deficits.

Acute low back pain may be due to a variety of conditions ranging from benign (eg, muscle strain) to devastating (eg, spinal cord compression from malignancy or abscess). For the clinician in the emergency department (ED), it is critical to develop a systematic approach that will allow one to differentiate and manage the minority of patients with conditions that threaten neurologic function from those with benign, self-limited etiologies. This chapter focuses primarily on the evaluation and management of acute (<4 weeks) low back pain.

An estimated 60–70% of adults in the United States will experience low back pain in their lifetime, and although only 25–30% will seek medical care, low back pain is an exceedingly common reason for ED visits in the United States. The economic impact of low back pain is substantial, estimated to account for $26.3 billion of direct health care costs in the United States in 1998.

The pathophysiology of nonspecific low back pain is usually indeterminate, as pain may arise from a number of sites including the vertebral column, surrounding muscles, tendons, ligaments, and fascia. The mechanism of injury to these structures varies from stretching, tearing, or contusion as a result of heavy lifting or torsion of the spinal column. In contrast, the pathophysiology of radicular low back pain is more clearly defined. Herniation of the nucleus pulposus through the annulus fibrosis causes compression of the dural lining around the spinal nerve root, resulting in radicular pain.

The history and physical examination serve as cornerstones in the evaluation of back pain. To facilitate a rational diagnostic approach, an attempt is made to classify low back pain into 1 of 3 categories:

1. 
   

   Nonspecific low back pain: pain with no signs or symptoms of a serious underlying condition

   
   
2. 
   

   Radicular back pain: pain with nerve root dysfunction associated with pain, sensory impairment, weakness, or impaired deep tendon reflexes in a specific nerve root distribution

   
   
3. 
   

   Serious underlying etiology: pain with neurologic deficits or underlying conditions requiring prompt evaluation (eg, tumor, infection, fracture, cauda equina syndrome)

History

The history should focus on the location of pain (including radiation of pain), frequency and duration of symptoms, and exacerbating and alleviating factors, as well as any previous episodes or treatments of back pain. Pain that radiates down the leg, usually past the knee, suggests a radiculopathy. Pain from a herniated disk is worse with movement, sitting, or Valsalva maneuver (eg, coughing). Pain worse at night or rest suggests malignancy or spinal infection. A past medical history of malignancy or immunocompromise is determined. Inquire about recent weight loss or fevers. Patients should also be asked about severe or progressive neurologic deficits including motor deficits, fecal incontinence, and bladder dysfunction. Bilateral leg pain and bowel/bladder dysfunction suggests cauda equina syndrome. Other warning signs of serious disease underlying low back pain are listed in Table 92-1