What is the pathophysiology and management of a closed burst fractured lumbar vertebra?

Pathophysiology and Management of Closed Burst Fractured Lumbar Vertebra

Burst fractures of the lumbar spine occur due to axial compression forces that cause failure of both the anterior and middle columns of the spine, resulting in vertebral body fragmentation with potential retropulsion of bone fragments into the spinal canal.

Pathophysiology

Mechanism of Injury

• Burst fractures typically result from high-energy axial compression forces, most commonly from:
  • Falls from height
  • Motor vehicle accidents
  • Direct trauma to the spine 1

Anatomical Disruption

• Characterized by vertebral body fragmentation with potential involvement of:
  • Anterior column (vertebral body)
  • Middle column (posterior vertebral body wall and posterior longitudinal ligament)
  • Possible posterior column involvement in more severe cases 2
• Retropulsion of bone fragments into the spinal canal may occur, potentially causing neural compression 2
• Differs from simple compression fractures which involve only the anterior column

Classification

The AO Spine classification system categorizes thoracolumbar fractures into three types:

1. Type A: Compression Fractures

   • A1: Impaction fractures
   • A2: Split fractures
   • A3: Burst fractures (with fragmentation of the vertebral body) 2

2. Type B: Distraction/Tension Injuries

   • B1: Transosseous monosegmental failure of posterior tension band
   • B2: Osseous and/or ligamentous failure of posterior tension band with Type A fracture
   • B3: Hyperextension injuries through disc space or bone 3

3. Type C: Translation Injuries

   • Disruption of all elements with displacement/dislocation 3

Neurological Considerations

• Neurological status is classified into 5 levels:
  • N0: Intact
  • N1: Transient symptoms
  • N2: Radiculopathy
  • N3: Incomplete spinal cord or cauda equina injury
  • N4: Complete spinal cord injury 2

Diagnostic Evaluation

Imaging

1. Plain Radiographs

   • Initial assessment of alignment, vertebral height loss, and interpedicular widening 2

2. Computed Tomography (CT)

   • Essential for characterizing:
     • Vertebral body fragmentation
     • Spinal canal compromise
     • Posterior element involvement
     • Vertebral displacement 2

3. Magnetic Resonance Imaging (MRI)

   • Critical for evaluating:
     • Posterior ligamentous complex integrity
     • Soft tissue injuries
     • Vertebral contusions not visible on CT
     • May modify the AO classification in up to 31% of cases 2

Management

Initial Management

• Immediate spinal immobilization for suspected spinal injury
• Adequate pain control
• Maintenance of blood pressure to optimize spinal cord perfusion 2

Treatment Decision Algorithm

1. Non-operative Management

   • Indicated for:
     • Neurologically intact patients with stable burst fractures
     • Minimal canal compromise
     • Minimal kyphosis
     • No posterior ligamentous complex injury 3, 4
   • Treatment options:
     • External bracing or no bracing (both equally effective) 3
     • Early mobilization as tolerated

2. Surgical Management

   • Indicated for:

     • Neurological deficit
     • Significant canal compromise
     • Significant kyphosis (>30°)
     • Posterior ligamentous complex injury
     • Type B and C injuries 3, 2

   • Surgical approach options:

     • Posterior approach: Most common, allows for decompression and stabilization
     • Anterior approach: Better for direct decompression of the spinal canal
     • Combined approach: For complex cases with significant anterior and posterior column disruption 3

Specific Considerations for Lumbar Burst Fractures

• L5 burst fractures have unique considerations due to their location at the lumbosacral junction 5
• Contiguous burst fractures involving multiple lumbar vertebrae are uncommon but require special attention 1
• Young patients with minimal canal compromise often have excellent outcomes with non-operative treatment 6
• Neurological deficits respond more predictably to surgical decompression than to conservative treatment 6

Outcomes and Complications

• Non-operative treatment:

  • Lower complication rates
  • Lower healthcare costs
  • Potential for chronic pain and progressive kyphosis in some cases 4

• Surgical treatment:

  • Higher complication rates
  • Need for implant removal in some cases
  • Better correction of deformity
  • Potentially better neurological outcomes in cases with deficits 4, 6

Key Management Principles

1. Thorough neurological assessment is essential for treatment decision-making
2. CT and MRI are critical for comprehensive fracture evaluation
3. Stable burst fractures without neurological deficit can be managed non-operatively
4. Unstable fractures and those with neurological deficits typically require surgical intervention
5. The choice of surgical approach (anterior, posterior, or combined) should be based on fracture pattern, neurological status, and degree of canal compromise 3

Common Pitfalls to Avoid

• Failing to recognize posterior ligamentous complex injury, which may necessitate surgical intervention
• Overlooking progressive kyphosis during non-operative management
• Underestimating the potential for neurological deterioration in initially intact patients with significant canal compromise
• Delaying surgical intervention in patients with progressive neurological deficits