What is the best initial imaging modality to rule out a fracture?

Best Imaging Modality to Rule Out Fracture

Radiographs (X-rays) should be the initial imaging modality for suspected fractures, with MRI as the preferred second-line imaging when radiographs are negative but clinical suspicion remains high. 1, 2

Initial Imaging Approach

Radiographs (X-rays)

• Standard first-line imaging for all suspected fractures
• Minimum requirements:
  • Two views: anteroposterior (AP) and lateral views 1, 2
  • Additional views for specific concerns:
    • Patellofemoral view for suspected patellar fractures/subluxation 1
    • Weightbearing views for suspected Lisfranc injuries 1
• Advantages:
  • Widely available and inexpensive
  • Good for initial screening
• Limitations:
  • Limited sensitivity (may miss occult fractures)
  • Cannot reliably exclude fracture when negative 1

Second-Line Imaging (When Radiographs are Negative)

MRI

• Preferred second-line imaging when radiographs are negative but clinical suspicion remains high 1, 2
• Indications:
  • Persistent pain despite negative radiographs
  • High clinical suspicion for occult fracture
• Advantages:
  • Near 100% sensitivity for fracture detection 1
  • Excellent for detecting:
    • Bone marrow contusions
    • Occult fractures
    • Soft tissue injuries (meniscal, ligamentous) 1, 3
  • No ionizing radiation
• Limitations:
  • Higher cost
  • Longer acquisition time
  • Contraindications (pacemakers, certain implants)
  • May not be immediately available

CT

• Alternative when MRI is contraindicated or unavailable 2, 4
• Indications:
  • Suspected complex fractures requiring surgical planning
  • Contraindications to MRI
  • Need for rapid imaging
• Advantages:
  • Superior to radiographs (80-100% sensitivity for fractures) 1
  • Excellent for bony detail and fracture characterization
  • Faster acquisition time than MRI
  • Fewer contraindications than MRI
• Limitations:
  • Ionizing radiation exposure
  • Less sensitive than MRI for soft tissue injuries
  • Less sensitive for bone marrow edema

Special Considerations

Anatomic Location

• Hip/Pelvis: MRI has 99% sensitivity for proximal femoral and pelvic fractures; CT is a reasonable alternative with 31% fracture detection rate in elderly patients with negative radiographs 1, 4
• Knee: CT superior for tibial plateau fractures (100% sensitivity vs 83% for radiographs) 1
• Foot: CT essential for midfoot fractures (25% of midfoot fractures identified on CT are missed on radiographs) 1

Patient Factors

• Elderly patients: Consider CT as an alternative to MRI due to:
  • Higher prevalence of MRI contraindications (26% in one study) 4
  • Shorter ED time with CT (430 min vs 502 min for MRI) 4
• Polytrauma patients: CT may be preferred as initial imaging due to:
  • Need for rapid assessment
  • Ability to image multiple body regions simultaneously 1

Common Pitfalls to Avoid

1. Relying solely on negative radiographs when clinical suspicion is high
2. Delaying advanced imaging when indicated, which can lead to:
   • Delayed diagnosis
   • Progression to complete fracture
   • Poorer outcomes
3. Choosing CT over MRI for soft tissue injury evaluation
4. Not considering patient-specific factors (contraindications, time constraints)

By following this evidence-based approach, clinicians can optimize fracture detection while minimizing unnecessary radiation exposure and healthcare costs.