When should I get an MRI if a navicular fracture is suspected on x-ray?

MRI for Suspected Navicular Fracture

When a navicular fracture is suspected on X-ray, an MRI should be obtained immediately as the next imaging study, especially since the navicular is classified as a high-risk stress fracture location where delayed diagnosis can lead to significant complications. 1

Diagnostic Challenges with Navicular Fractures

• Initial radiographs often miss navicular fractures, with studies showing false-negative rates of up to 20% for carpal navicular fractures 2 and poor sensitivity for tarsal navicular fractures 3
• The navicular bone is specifically classified as a "high-risk" location for stress fractures, along with the anterior tibial diaphysis, lateral femoral neck, patella, medial malleolus, fifth metatarsal base, proximal second metatarsal, tibial hallux sesamoid, and talus 1
• Delayed diagnosis of navicular fractures can lead to serious complications including delayed union, nonunion, avascular necrosis, and deformity 2, 4

Imaging Algorithm for Suspected Navicular Fracture

Step 1: Initial Radiographs

• Standard radiographs should be the first imaging study for any suspected fracture 1
• For suspected navicular fractures, consider additional views beyond standard three-view foot radiographs to improve detection 5

Step 2: When to Get MRI

• Immediate MRI is indicated when:

  • Radiographs show a suspected navicular fracture but further characterization is needed 1
  • Clinical suspicion remains high despite negative radiographs 1
  • There is a "need-to-know" diagnosis situation requiring immediate treatment decisions 1
  • The patient has significant functional limitations or is an athlete requiring expedited return-to-play decisions 1

• MRI without contrast is the preferred modality as it:

  • Demonstrates bone marrow edema patterns that improve fracture detection 1
  • Has superior sensitivity compared to CT for detecting early stress injuries 1
  • Can identify associated soft tissue injuries that may affect treatment decisions 1
  • Provides prognostic information about healing potential and return to activity 1

Step 3: Role of CT

• Consider CT as an alternative or complementary study when:
  • MRI is contraindicated or unavailable 1
  • There is need to better characterize fracture displacement or comminution for surgical planning 1, 6
  • The fracture is complex and involves articular surfaces 1, 3

Clinical Implications and Management Considerations

• Navicular stress fractures require aggressive management, with studies showing that non-weight-bearing cast immobilization for at least 6 weeks results in significantly better outcomes (86% successful return to sports) compared to limited activity with continued weight-bearing (only 26% successful return) 4
• MRI findings can guide treatment decisions and predict time to return to activity, with higher MRI grades of injury correlating with longer recovery times 1
• For navicular body fractures, surgical outcomes vary significantly based on fracture pattern, with type III fractures having particularly poor outcomes even with surgical intervention 6

Common Pitfalls to Avoid

• Do not rely solely on radiographs to rule out navicular fractures, especially in athletes with persistent symptoms 1, 2
• Do not delay MRI when clinical suspicion is high, as the navicular is a high-risk location where delayed diagnosis can lead to poor outcomes 1
• Do not allow patients with suspected navicular fractures to continue weight-bearing activities while awaiting definitive diagnosis, as this can significantly worsen outcomes 4
• Do not use ultrasound as primary imaging for navicular fractures, as it has poor sensitivity (40%) for detecting navicular fractures 1