What is the best imaging modality for spinal fractures?

Best Imaging Modality for Spinal Fractures

CT is the gold standard for detecting spinal fractures, with sensitivity of 94-100% for identifying bony injuries across all spinal regions. 1

Initial Imaging Strategy

CT as First-Line Modality

• CT should be the primary imaging study for suspected spinal fractures in trauma patients, demonstrating superior sensitivity (94-100%) compared to plain radiographs which miss approximately two-thirds of fractures visible on CT. 1, 2
• Multidetector CT excels at delineating fracture patterns, displacement, and canal compromise with near-perfect specificity (approaching 100%). 1
• Sagittal and coronal reformations from chest/abdomen/pelvis CT data are equally effective as dedicated spine protocols for fracture detection, making additional dedicated spine CT unnecessary in most polytrauma cases. 1

Plain Radiography Has Limited Role

• Radiographs identify only 31-52% of fractures detected on CT and should not be used as the sole screening modality. 1
• The three-view cervical spine series (AP, lateral, open-mouth odontoid) misses significant injuries and has been largely supplanted by CT. 1

When to Add MRI

Mandatory MRI Indications

MRI must be obtained when any of the following are present: 1

• Neurologic deficits (motor weakness, sensory changes, bowel/bladder dysfunction)
• Clinical suspicion for spinal cord injury or compression
• Signs or symptoms of nerve root injury
• Concern for ligamentous instability despite normal or equivocal CT

MRI's Specific Advantages

• MRI is the only modality that directly visualizes spinal cord injury, including intramedullary hemorrhage, edema extent, and cord compression from disc herniation or epidural hematoma. 1, 3
• Superior for detecting soft tissue injuries: ligamentous disruption, traumatic disc herniation, and epidural hematomas that CT cannot adequately assess. 1, 4
• Prognostic value: intramedullary hemorrhage and edema spanning >1 segment correlate with severe neurologic deficit. 3

Critical Clinical Scenarios

Neurologically Intact Patients with Negative CT

• In patients without neurologic deficits, CT alone may be sufficient for clearance. 1
• MRI identifies soft tissue injuries in 5-24% of patients with negative cervical spine CT, but <1% represent clinically significant instability requiring surgical intervention. 1
• The ReCONECT trial found MRI abnormalities in 23.6% of patients with negative CT, but clinical significance remains uncertain as most did not require surgery. 1

Obtunded/Unexaminable Patients

• CT demonstrates 98.5% sensitivity for clinically significant injury in obtunded blunt trauma patients. 1
• MRI adds value primarily when patients remain unexaminable beyond 48-72 hours or have persistent unexplained cervicalgia. 1
• Purely ligamentous cervical injuries without fracture are exceptionally rare (0.1-0.7% of blunt trauma), making routine MRI screening of low yield. 1

Thoracolumbar Spine Considerations

• Isolated unstable ligamentous injury in the thoracolumbar spine without fracture is extremely rare or may not occur at all, making MRI screening unnecessary when CT is normal unless neurologic symptoms are present. 1
• CT sensitivity for thoracolumbar fractures is 94-99% using routine body imaging protocols. 1

Common Pitfalls to Avoid

Don't Miss Noncontiguous Fractures

• Image the entire spine when one fracture is identified—20% of patients have noncontiguous fractures at other levels. 2

Don't Delay MRI When Indicated

• In patients with neurologic deficits, delayed imaging correlates with poorer outcomes; obtain MRI urgently when spinal cord injury is suspected. 2

Don't Over-rely on MRI Specificity

• MRI has high sensitivity but lower specificity (25-40% false positive rate) for ligamentous injury, as many findings may not represent true instability. 1
• Established criteria for distinguishing significant from inconsequential MRI abnormalities do not exist. 1

CT Limitations You Must Recognize

• CT significantly underperforms for soft tissue pathology: epidural hematomas, cord contusions, disc herniations, and nerve root avulsions require MRI. 1, 4
• CT missed 50% of C-spine injuries ultimately detected on MRI in one comparative study, particularly soft tissue and C1 fractures. 4

Practical Algorithm

1. Start with CT for all suspected spinal fractures in trauma 1, 2
2. Add MRI immediately if:
   • Any neurologic deficit present 1
   • Clinical suspicion for cord injury regardless of CT findings 1
   • Unexplained neurologic symptoms with normal CT 1
3. Consider MRI selectively if:
   • Obtunded patient unable to be cleared clinically within 48-72 hours 1
   • Persistent neck pain despite negative CT in alert patient 1
4. CT alone sufficient when:
   • Neurologically intact with negative clinical examination 1
   • No persistent midline tenderness after negative CT 1