Should further imaging be considered for a suspected stress fracture in a patient with persistent foot pain at the dorsum of the foot, despite a negative X-ray?

MRI is the Recommended Imaging for Suspected Stress Fracture After Negative X-ray

For a patient with persistent foot pain at the dorsum of the foot for one week with a negative X-ray, MRI without IV contrast should be performed if a stress fracture is still suspected. 1

Diagnostic Algorithm for Suspected Stress Fracture

Initial Imaging

• X-ray is the appropriate first-line imaging test for suspected stress fractures, but has limited sensitivity (15-35%) in early stages 2
• Early radiographic signs of stress fractures may be subtle or nonexistent, particularly when symptoms have been present for less than 10-14 days 2

When X-rays are Negative

• MRI without IV contrast is the preferred second-line imaging study when X-rays are negative but clinical suspicion for stress fracture remains high 1
• MRI demonstrates stress abnormalities earlier than X-rays with excellent sensitivity and specificity 1
• MRI typically shows:
  • Linear T1 and T2 hypointense signal (fracture lines)
  • T1 hypointense and T2 hyperintense signal in surrounding bone marrow (edema) 1

Alternative Imaging Options

• Follow-up radiographs in 10-14 days can show increased sensitivity (30-70%) compared to initial X-rays, but are still less sensitive than MRI 1, 2
• CT without contrast can be considered when MRI is contraindicated or unavailable, but is less sensitive than MRI 1, 3
• Ultrasound has emerging evidence for use in distal extremity stress fractures but should not be the primary imaging choice for foot stress fractures 1
• Bone scintigraphy with SPECT or SPECT/CT has high sensitivity but lacks specificity compared to MRI 1

Clinical Considerations

High-Risk Stress Fracture Locations

• Certain foot bones are considered "high-risk" locations for stress fractures, including:
  • Navicular
  • Fifth metatarsal base
  • Proximal second metatarsal
  • Tibial hallux sesamoid 1, 3, 4
• Delayed diagnosis of stress fractures in these high-risk locations can lead to significant complications including nonunion, delayed union, or complete fracture 3, 4

Benefits of Early MRI

• Prevents delayed diagnosis which can lead to fracture progression and complications 1
• Allows for definitive diagnosis with excellent sensitivity 1
• Can identify associated soft tissue injuries or other causes of foot pain 1, 3
• Can guide treatment decisions and predict time to return to activity 3, 4
• Does not use ionizing radiation 1

Common Pitfalls to Avoid

• Relying solely on negative initial X-rays to rule out stress fracture, especially when clinical suspicion is high 2, 5
• Delaying appropriate imaging when symptoms persist, which can lead to fracture progression 1, 6
• Using ultrasound as the primary imaging modality for suspected foot stress fractures 3
• Waiting for follow-up X-rays when immediate diagnosis is needed for high-risk stress fracture locations 1, 3

Summary of Evidence Quality

The American College of Radiology Appropriateness Criteria (2024) provides the most recent and highest quality evidence supporting MRI without contrast as the preferred second-line imaging study for suspected stress fractures after negative radiographs 1. This recommendation is consistent across multiple guidelines and research studies 5, 6, 7.