How should a doctor proceed to diagnose lower back pain in the immediate days following an event?

Diagnostic Approach for Low Back Pain in the Immediate Days Following an Event

In the immediate days following an event causing low back pain, clinicians should conduct a focused history and physical examination to categorize the patient into one of three categories: nonspecific low back pain, back pain potentially associated with radiculopathy or spinal stenosis, or back pain potentially associated with another specific spinal cause. 1

Initial Assessment

History Taking

• Inquire about location, frequency, and duration of pain, as well as any history of previous symptoms, treatments, and response to treatments 1
• Assess for risk factors for serious underlying conditions:
  • Cancer: history of cancer (positive likelihood ratio 14.7), unexplained weight loss (positive likelihood ratio 2.7), failure to improve after 1 month (positive likelihood ratio 3.0), age >50 years (positive likelihood ratio 2.7) 1
  • Infection: fever, intravenous drug use, recent infection 1
  • Compression fracture: older age, history of osteoporosis, steroid use 1
  • Ankylosing spondylitis: younger age, morning stiffness 1

Physical Examination

• Evaluate for rapidly progressive or severe neurologic deficits, including motor deficits at more than one level, fecal incontinence, and bladder dysfunction 1
• Check for urinary retention, which is the most frequent finding (90% sensitivity) in cauda equina syndrome 1
• Assess for signs of radiculopathy or spinal stenosis:
  • For radiculopathy: positive straight leg raise test (sensitivity 91%, specificity 26%) 1
  • For spinal stenosis: pseudoclaudication (positive likelihood ratio 1.2), radiating leg pain (positive likelihood ratio 2.2), changing symptoms on downhill treadmill testing (positive likelihood ratio 3.1) 1

Psychosocial Assessment

• Evaluate psychosocial factors and emotional distress, as these are stronger predictors of low back pain outcomes than physical examination findings or pain severity 1
• Key factors to assess include depression, passive coping strategies, job dissatisfaction, higher disability levels, disputed compensation claims, and somatization 1

Diagnostic Categorization

Based on history and physical examination, place patients into one of three categories:

1. Nonspecific low back pain (85% of cases) 1

   • Cannot be reliably attributed to a specific disease or spinal abnormality
   • No red flags or neurologic deficits

2. Back pain potentially associated with radiculopathy or spinal stenosis 1

   • Suggested by sciatica or pseudoclaudication
   • Positive neurologic findings consistent with nerve root compression

3. Back pain potentially associated with another specific spinal cause 1

   • Includes serious conditions requiring prompt evaluation (tumor, infection, cauda equina syndrome)
   • Also includes conditions that may respond to specific treatments (ankylosing spondylitis, vertebral compression fracture)

Diagnostic Testing

When to Avoid Imaging

• Do not routinely obtain imaging or other diagnostic tests in patients with nonspecific low back pain 1
• Routine imaging does not improve outcomes and may expose patients to unnecessary radiation 1
• In young women, a single lumbar spine radiograph (2 views) exposes them to gonadal radiation equivalent to daily chest radiographs for more than a year 1

When to Perform Imaging

• Perform diagnostic imaging when: 1
  • Severe or progressive neurologic deficits are present
  • Serious underlying conditions are suspected based on history and physical examination
• MRI is preferred over CT if available as it does not use ionizing radiation and provides better visualization of soft tissue, vertebral marrow, and the spinal canal 1
• For suspected vertebral compression fracture in high-risk patients (history of osteoporosis or steroid use), plain radiography is recommended for initial evaluation 1

Special Considerations for Cancer Risk

• For patients with a history of cancer (strongest predictor of vertebral cancer), consider direct MRI 1
• For patients with other risk factors but no signs of spinal cord compression, consider plain radiography or erythrocyte sedimentation rate (ESR ≥20 mm/h has 78% sensitivity and 67% specificity for cancer) 1
• For patients older than 50 years without other risk factors for cancer, consider delaying imaging while offering standard treatments and reevaluating within 1 month 1

Follow-up Assessment

• Reevaluate patients with persistent, unimproved symptoms after 1 month, as most patients with acute low back pain experience substantial improvement within the first month 1
• Consider earlier or more frequent reevaluation for: 1
  • Patients with severe pain or functional deficits
  • Older patients
  • Patients with signs of radiculopathy or spinal stenosis

Common Pitfalls and Caveats

• Avoid overreliance on imaging findings, as radiographic abnormalities are often poorly correlated with symptoms and could lead to unnecessary interventions 1
• Don't miss the cauda equina syndrome, which is rare (0.04% prevalence among patients with low back pain) but requires urgent intervention 1
• Remember that psychosocial factors are stronger predictors of outcomes than physical findings or pain severity 1
• Avoid bed rest, which is less effective than remaining active for patients with acute or subacute low back pain 1
• Be aware that attempts to identify specific anatomical sources of nonspecific low back pain have not been validated in rigorous studies 1