How is the stability of a vertebral burst fracture graded on MRI, and which sequences (T1‑weighted, T2‑weighted, fat‑suppressed STIR, gradient‑echo or susceptibility‑weighted) should be assessed for signal intensity to determine severity and potential complications?

MRI Stability Grading of Vertebral Burst Fractures

MRI is essential for assessing vertebral burst fracture stability, with T1-weighted and T2-weighted/STIR sequences being the critical sequences to evaluate posterior ligamentous complex (PLC) integrity, which directly determines surgical versus conservative management in up to 24% of patients. 1

Key MRI Sequences and Their Specific Roles

T1-Weighted Sequences

• Primary role: Assessment of posterior ligamentous complex (PLC) disruption
• Signal characteristics:
  • Intact PLC shows normal low signal intensity
  • Disrupted PLC demonstrates high signal intensity indicating hemorrhage/edema
  • Allows visualization of supraspinous ligament disruption, which is the most commonly missed source of instability 2
• Additional utility: Detection of spinal cord edema and epidural hematoma 1

T2-Weighted and STIR (Fat-Suppressed) Sequences

• Primary role: Detection of soft tissue injury and edema
• Signal characteristics:
  • High signal intensity indicates acute injury, edema, or hemorrhage
  • STIR provides highest contrast between abnormal and normal marrow 3
  • Essential for identifying spinal cord contusions, nerve root injuries, and epidural hematomas 1
• Critical distinction: Acute fractures show high signal on T2/STIR, but the pattern is typically more inhomogeneous than pathologic fractures 3

Susceptibility-Weighted Imaging (SWI/Gradient-Echo)

• Specialized role: Superior detection of cortical breaks and fracture lines
• Diagnostic accuracy:
  • 98% sensitivity/100% specificity for posterior vertebral body cortex involvement
  • 93% sensitivity/100% specificity for cortical breaks
  • 86% sensitivity/99% specificity for fracture lines 4
• Particular advantage: Most accurate in non-healed fractures where cortical disruption assessment is critical 4

Stability Grading Framework

The TLICS (Thoracolumbar Injury Classification and Severity) System

MRI changes TLICS scores from <5 (conservative) to ≥5 (surgical) in 24% of patients 1

Critical MRI findings that indicate instability:

1. PLC disruption (most important soft tissue predictor)

   • Complete disruption on T1/T2 sequences = unstable
   • Widening of interspinous/interlaminar distance

2. Posterior vertebral body cortex displacement

   • Best assessed on susceptibility-weighted sequences 4
   • Retropulsion into spinal canal

3. Spinal cord compression or injury

   • High T2 signal within cord = edema/contusion
   • Epidural hematoma causing canal compromise

4. Additional fractures detected

   • MRI identifies 34 additional fractures beyond CT (196 vs 162 total) 1
   • Non-contiguous spine injuries 1

Algorithmic Approach to MRI Assessment

Step 1: Obtain Standard Sequences

• T1-weighted (sagittal and axial)
• T2-weighted (sagittal and axial)
• STIR/fat-suppressed (sagittal)
• Consider adding susceptibility-weighted imaging for complex fractures 4

Step 2: Systematic Evaluation

1. Assess PLC integrity on T1/T2

   • Look for high signal in supraspinous/interspinous ligaments
   • Measure interspinous widening

2. Evaluate posterior vertebral cortex on all sequences

   • Measure displacement/retropulsion
   • Assess canal compromise percentage

3. Examine spinal cord on T2/STIR

   • Identify cord edema (high T2 signal)
   • Detect epidural hematoma

4. Screen entire spine for additional injuries

   • MRI detects 40% more fractures than plain films/CT alone 1

Step 3: Grade Severity

• Stable: Intact PLC, minimal retropulsion, no cord injury
• Potentially unstable: Partial PLC injury, moderate retropulsion
• Unstable: Complete PLC disruption, significant retropulsion, cord compression

Critical Pitfalls to Avoid

1. Relying on CT alone: CT misses PLC injuries and changes management in 16-40% of thoracolumbar fractures 1

2. Incomplete PLC assessment: Supraspinous ligament disruption is frequently unrecognized without MRI, leading to underestimation of instability 2

3. Missing non-contiguous fractures: MRI identifies additional vertebral injuries in 40% of patients that alter classification 1

4. Inadequate sequence selection: Standard T1/T2 sequences are mandatory; susceptibility-weighted imaging adds value for cortical assessment but is not always available 4

Consequences Assessed by MRI Signal Intensity

Neurological complications:

• Spinal cord edema/contusion: High T2/STIR signal within cord
• Nerve root avulsion: Best seen on T2-weighted sequences
• Epidural hematoma: Variable signal depending on age

Fracture age determination:

• Acute: High T2/STIR signal, edema pattern
• Chronic: Isointense to normal vertebrae on all sequences 3

Risk stratification:

• High T1-weighted VBQ scores predict imminent new vertebral fractures 5
• Complete fatty marrow replacement on fat-suppressed sequences suggests pathologic fracture 3