12. Low Back Pain

Low back pain is an incredibly common complaint with up to 25% of adults having at least one day of back pain in the previous three months.

Differential Diagnosis 

Broad list of diagnoses but 85% of adults with low back pain have a non-specific musculoligamentous cause. Other common causes include: herniated disc (4%), compression fracture (4%), spinal stenosis (3%), ankylosing spondylitis, cancer, infection.

Evaluation

  • Evaluate for “red flag” features which include: 
    • Focal neurologic complaints/deficits
    • History of cancer (strongly predicts back pain secondary to cancer)
    • Age > 50 years old
    • Fever not explained by another cause (highly predictive of spinal infection)
    • History of recent bacteremia or IVDU (predicts osteomyelitis)
    • Steroid use (strongly predicts compression fracture)
    • Weight loss
    • Pain that is worse at night (suggests cancer)
    • No relief with bed rest or pain lasting > 1 month
  • Examination 
    • Spine tenderness is 86% sensitive to help rule out spinal osteomyelitis
    • Straight leg raise is ~ 60% sensitive and specific for herniated disc
    • Crossed straight leg raise (when lifting the unaffected leg reproduces the sciatic pain) is 90% specific for herniated disc
  • Imaging 
    • Most patients with non-specific low back pain should not get diagnostic imaging
    • Immediate MRI should be performed for severe neurologic deficits, bowel or bladder incontinence, concern for spinal infection, or concern for cord compression
    • MRI can be considered after a trial of therapy in patients with signs and symptoms of radiculopathy or concern for spinal stenosis (who are candidates for surgical treatment)

Management

  • Most non-specific back pain resolves with conservative treatment. 50-75% of patients will be better by 4 weeks, 90% at 6 weeks
  • Conservative treatment can involve analgesia (acetaminophen, NSAIDs, opioids, gabapentin, TCAs), muscle relaxants if muscle spasm is present (e.g. baclofen), and physical therapy/exercise/yoga
  • Other management depends on the underlying cause

Choosing Wisely

Don’t obtain imaging studies in patients with non-specific low back pain. In patients with back pain that cannot be attributed to a specific disease or spinal abnormality following a history and physical examination, imaging with plain radiography, computed tomography (CT) scan, or magnetic resonance imaging (MRI) does not improve patient outcomes.

Key Points

  • Most (85%) of back pain is non-specific musculoligamentous injury
  • Evaluate for red flag features listed above