What is the best imaging modality to assess a non-healing fracture?

Best Imaging Modality for Non-Healing Fracture Assessment

MRI is the best imaging modality for assessing a non-healing fracture due to its superior sensitivity for detecting bone marrow edema, soft tissue abnormalities, and early signs of healing before they are visible on other imaging modalities. 1

Imaging Algorithm for Non-Healing Fracture Evaluation

First-Line Imaging

• Radiographs (X-rays): Should always be the initial imaging study
  • Provides baseline assessment of fracture alignment, callus formation
  • Limited sensitivity (15-35%) for early detection of healing problems 1
  • May remain negative despite ongoing non-union

Second-Line Imaging (When Radiographs Are Inconclusive)

• MRI without contrast: Preferred second-line imaging
  • Extremely sensitive for detecting stress abnormalities and non-union 1
  • Superior for evaluating:
    • Bone marrow edema patterns
    • Soft tissue complications
    • Vascular status of bone fragments
    • Associated ligamentous injuries 1
  • Provides prognostic information about healing potential 1
  • Fluid-sensitive sequences (STIR, T1-weighted) are most valuable 1

Alternative Second-Line Options

• CT scan: Best for detailed bony anatomy assessment

  • Superior for evaluating:
    • Fracture patterns and comminution
    • Intra-articular extension
    • Degree of displacement 1, 2
    • Extent of callus formation 3
  • Multiplanar reconstructions improve visualization of non-union 3
  • 3D reconstructions help surgical planning by showing malalignment 1, 2
  • Less sensitive than MRI for early detection of healing problems 1

• Bone scan (nuclear scintigraphy):

  • Can detect metabolic activity at fracture site 4
  • Useful for differentiating between viable and non-viable bone 4
  • Less specific than MRI or CT (may show increased uptake in infection) 1
  • Involves radiation exposure 1

Special Considerations

Anatomic Location Considerations

• Complex anatomical regions (ankle, scapula, pelvis):
  • CT provides better visualization of complex bony anatomy 1
  • MRI better for associated soft tissue injuries 1

Suspected Complications

• Infection concern: MRI with contrast or nuclear imaging 1
• Osteonecrosis risk: MRI is especially important for high-risk sites like talus 1
• Malignant transformation: FDG-PET/CT can differentiate benign from malignant pathologic fractures 1

Common Pitfalls to Avoid

• Relying solely on radiographs when clinical suspicion for non-union is high
• Failing to obtain adequate views (minimum of two perpendicular planes) 5
• Not considering ultrasound for early detection of callus formation in superficial bones 6
• Overlooking the need for CT when surgical planning is required 1, 3

Emerging Technologies

• Ultrasound shows promise for detecting bridging callus prior to radiographic confirmation 6
• Dynamic contrast-enhanced MRI may help assess infected non-unions 6

In conclusion, while radiographs remain the initial imaging modality, MRI provides the most comprehensive assessment of non-healing fractures with superior sensitivity for both bone and soft tissue abnormalities that may contribute to delayed union or non-union.