Thoracolumbar Burst Fractures - Spine

SUMMARY

Thoracolumbar burst fractures are a common high-energy traumatic vertebral fracture caused by flexion of the spine that leads to a compression force through the anterior and middle column of the vertebrae leading to retropulsion of bone into the spinal canal and compression of the neural elements.
Patients may present without neurological deficits or with neurologic deficits characterized by whether the compression is above, at, or below the level of the conus medullaris and whether a traumatic durotomy occured.
Treatment is bracing or surgical decompression and stabilization depending on whether the patient has neurologic deficits and whether the facture is unstable with a risk of drifting into kyphosis.

SCIENCE

Epidemiology
- demographics
  - often seen from falls from height or motor cycle accidents
Pathophysiology
- mechanism
  - axial loading with flexion
- pathoanatomy
  - at thoracolumbar junction there is fulcrum of increased motion that makes spine more vulnerable to traumatic injury
    - burst fractures typically occur between T10-L2 (thoracolumbar junction)
  - neurologic deficits
    - canal compromise often caused by retropulsion of bone
      - maximum canal occlusion and neural compression at moment of impact
      - tissue recoiling post-injury can minimize the extent of displacement
      - retropulsed fragments resorb over time and usually do not cause progressive neurologic deterioration
    - deficit type
      - location of stenosis relative to conus determines
        
        spinal cord injury
        
        conus medullaris syndrome
        
        neurogenic claudication due to stenosis distal to conus
Associated injuries
- concomitant spine fractures
  - occurs in 20%
- traumatic durotomy
  - lamina fracture is associated with dural tear and entrapped nerve roots
  - be aware when spit spinous process
- chest and intra-abdominal injuries
  - common
  - thoracic spine fractures with neurologic deficit
    - 1/3 associated with hemopneumothorax, major vessel injury, and diaphragmatic rupture
  - flexion-distration and fracture-dislocations
    - bowel rupture, major vessel injury, upper urinary tract injury, hepatic, splenic, and pancreatic lacerations
- long bone fractures
  - can make rehabilitation difficult

ANATOMY

Thoracic osteology
- T1-10 are rigidly fixed to ribs that join each other anteriorly via the sternum
  - least mobile portion of the entire spine
- T10-L2 is considered the thoracolumbar junction
  - T10-12 have free floating ribs and are more mobile than the upper thoracic spine
  - transition from rigid thoracic spine to mobile lumbar spine acts as a stress riser and predisposes to injury
Lumbar osteology
- increasingly more mobile as progresses caudal
- increasingly prone to degenerative changes
Denis three column system
- clinical relevance
  - only moderately reliable in determining clinical degree of stability
- definitions
  - anterior column
    - anterior longitudinal ligament (ALL)
    - anterior 2/3 of vertebral body and annulus
  - middle column
    - posterior longitudinal ligament (PLL)
    - posterior 1/3 of vertebral body and annulus
  - posterior column
    - pedicles
    - lamina
    - facets
    - ligamentum flavum
    - spinous process
    - posterior ligament complex (PLC)
  - instability defined by
    - injury to middle column
      - as evidenced by widening of interpedicular distance on AP radiograph
      - loss of height of posterior cortex of vertebral body
    - disruption of posterior ligament complex combined with anterior and middle column involvement
Posterior Ligamentous Complex
- considered to be a critical predictor of spinal fracture stability
- consists of
  - supraspinous ligament
  - interspinous ligament
  - ligamentum flavum
  - facet capsule
- evaluation
  - determining the integrity of the PLC can be challenging
    - conditions where PLC is clearly ruptured
      - bony chance fracture
      - widening of interspinous distance
      - progressive kyphosis with nonoperative treatment
      - facet diastasis
    - conditions where integrity of PLC is indeterminant
      - MRI shows signal intensity between spinous process
Spinal cord
- spinal cord ends at L1-2
  - conus medullaris
    - houses upper motor neurons on the sacral motor nerves
  - fractures involving L1 and result in conus medullaris syndrome
    - paralysis of the bowel and bladder with sparring of the motor nerve roots of the lower extremity

CLASSIFICATION

Dennis classification
- Type A
  - fracture of both end-plates. The bone is retropulsed into the canal.
- Type B
  - fracture of the superior end-plate. It is common and occurs due to a combination of axial load with flexion.
- Type C
  - fracture of the inferior end-plate.
- Type D
  - Burst rotation. This fracture could be misdiagnosed as a fracture-dislocation. The mechanism of this injury is a combination of axial load and rotation.
- Type E
  - Burst lateral flexion. This type of fracture differs from the lateral compression fracture in that it presents an increase of the interpediculate distance on anteroposterior roentgenogram
Thoracolumbar Injury Classification and Severity Score
- injury characteristic qualifier points
  - injury morphology
    - compression (+1 point)
    - burst (+2 points)
    - rotation/translation (+3 points)
    - distraction (+4 points)
  - neurologic status
    - intact (0 point)
    - nerve root (+2 points)
    - incomplete Spinal cord or conus medullaris injury (+3 points)
    - complete Spinal cord or conus medullaris injury (+2 points)
    - cauda equina syndrome (+3 points)
  - posterior ligamentous complex integrity
    - intact (0 point)
      - no interspinous ligament widening seen with flexion views. MRI shows no edema in interspinous ligament region
    - suspected/indeterminate (+2 points)
      - MRI shows some signal in region of interspinous ligaments
    - disrupted (+3 points)
      - widening of interspinous distance seen
- TLICS treatment implications
  - score < 4 points
    - nonsurgical management
  - score = 4 points
    - nonsurgical or surgical managment
  - score > 4 points
    - surgical management indicated

PRESENTATION

History
- high-energy mechanism
  - axial-loading and flexion mechanisms
    - fall from height (e.g. fall from deer hunting stand, fall from ladder, etc.)
    - high-speed motor vehicle collision
Symptoms
- severe back pain
- radicular pain
- parasthesias
Physical exam
- vital signs
  - hypotension is common
    - neurogenic shock
      - hypotension with associated bradycardia
        
        suggests spinal cord injury leading to loss of autonomic regulation
    - hypovolemic shock
      - hypotension with compensatory tachycardia
        
        suggests massive hemorrhage from major vessel injury
- inspection
  - log roll patient during initial assessment to avoid iatrogenic spinal cord injury in the setting of an unstable fracture pattern
  - skin abraisons and ecchymosis
    - open spinal fractures are uncommon
- palpation of spinous processes
  - fluid collection
  - crepitus
  - increased interspinous distance
    - suggests injury to the posterior elements
  - localized tenderness
- neurologic examination
  - motor
  - sensory
  - reflexes
    - absence of bulbocavernous reflex is considered spinal shock
      - can persist for up to 72 hours
      - hyperactive bulbocavernous reflex suggests disinhibition and a complete spinal cord injury

IMAGING

Radiographs
- recommended views
  - AP/lateral cervical, thoracic, lumbar spine
    - often CT chest, abdomen, and pelvis done by trauma team and instead of radiographs
    - imaging of entire spine must be performed due to concomitant spine fractures in 20%
  - flexion and extension lateral radiographs
    - useful once patient is stabilized to get understanding of integrity of PLC
  - findings
    - AP shows
      - widening of pedicles
      - coronal deformity
    - lateral shows
      - retropulsion of bone into canal
      - extent of retropulsion can be underestimated with plain radiographs alone
      - kyphotic deformity
      - chance-like spinous process fx
    - flexion/extension
      - diastasis of spinous process with flexion indicates soft tissue injury to PLC
CT scan
- indications
  - fracture on plain film
  - neurologic deficit in lower extremity
  - inadequate plain films
    - higher sensitivity at detecting acute spine fractures than plain films
- most accurately assesses the extent of fragment retropulsion
  - best assess on the axial views
- better assessment vertebral body comminution
CT myelography
- indications
  - alternative for patients with pacemaker and other implants that are MRI incompatible
  - cannot assess the cord status
  - consider traumatic durotomy
MRI
- indications
  - whenever neurological deficits
- useful to evaluate for
  - level of conus relative to retropulsed bone
  - spinal cord or thecal sac compression by disk or osseous material
  - cord edema or hematoma
    - cord edema
      - fusiform cord enlargement
      - increased signal intensity on T2-weighted images
    - cord hematoma
      - decreased singal intensity on T2-weighted images
      - halo of T2 enhancement for surrounding edema
    - presence of cord edema more than 2 vertebral levels and hematoma are poor prognostic signs for functional motor recovery
  - injury posterior ligament complex
    - increased signal intensity on T2 weighted images in PLC is concerning for instability and may warrant surgical intervention
    - best visualized on the sagittal images

TREATMENT

Nonoperative
- activity as tolerated +/- thoracolumbosacral orthosis
  - indications
    - patients that are neurologically intact and mechanically stable
      - posterior ligament complex preserved
      - no focal kyphosis on flexion and extension lateral radiographs
      - kyphosis < 30° (controversial)
      - vertebral body has lost < 50% of body height (controversial)
    - TLICS score = 3 or lower
  - modality
    - thoracolumbar orthosis
      - recent evidence shows no clear advantage of TLSO on outcomes
        
        if it provides symptomatic relief, may be beneficial for patient
        
        bracing may not be suitable for those with associated abdominal or chest injuries
  - outcomes
    - retropulsed fragments resorb over time and usually do not cause neurologic deterioration
    - decreased complication rates in neurologically intact patients treated nonsurgically
    - equivalent outcomes in neurologically intact patients
    - prolonged bedrest associated with increased deconditioning and recumbency complications (pneumonia, DVT, etc.)
Operative
- posterior instrumented fusion/stabilization without decompression
  - indications
    - unstable fracture pattern as defined by
      - injury to the Posterior Ligament Complex (PLC)
      - progressive kyphosis
      - lamina fractures (controversial)
      - polytrauma
        
        surgical stabilization can assist with recovery and rehabilitation of other injuries
  - technique
    - may be performed with percutanous pedicle screws using fluoroscopy or navigation
    - may extension instrumentation further than level of arthrodesis (fuse short, instrument long)
  - outcomes
    - unstable injuries are more likely to benefit from surgical stabilization compared to nonsurgical treatment
- neurologic decompression & spinal stabilization
  - indications
    - neurologic deficits with radiographic evidence of cord/thecal sac compression
      - both complete and incomplete spinal cord injuries require decompression and stabilization to facilitate rehabilitation
    - TLICS score = 5 or higher
  - techniques
    - while classic teaching was anterior approach is required to eliminate anterior pathology, with modern techniques decompression can be performed with
      - posterior approach
        
        favored when
        
        below conus so possible to medialize thecal sac to perform decompression of canal / posterior corpectomy and expandable cage
        
        injury to posterior ligamentous complex so posterior tension-band stabilization required
        
        fracture dislocations
      - anterior/direct lateral approach
        
        favored when
        
        neurologic deficits caused by anterior compression (bony retropulsion) , especially above the conus medullaris (above L2)
        
        allow for thorough decompression of the thecal sac
        
        substantial vertebral body comminution in order to reconstitute the anterior column
        
        kyphotic deformity >30°
        
        chronic injuries
        
        greater than 4-5 days from the injury
        
        cons
        
        must consider level of diaphragm
  - outcomes
    - studies have suggested posterior distraction instrumentation with ligamentotaxis have similar clinical and radiographic outcomes as anterior decompression and 360° stabilization
    - over distraction of the anterior column can lead to pseudoarthrosis, chronic pain, and recurrent deformity

TECHNIQUES

Posterior instrumented fusion/stabilization without decompression
- approach
  - posterior midline approach
    - subperiosteal elevation of paraspinal musculature
    - expose lateral to the transverse processes
- technique
  - transpedicular screw fixation above and below the level of injury
    - historically involve three levels above and two levels below the level of injury
      - modern constructs typically involve one level above and one level below the injury
        
        short segment fixation not suitable for injuires involving the thoracolumbar junction
- complications
  - loss of sagittal plane correction
Neurologic decompression & spine stabilization
- approach
  - posterior approach
    - typically posterior midline approach
      - subperiosteal elevation of paraspinal musculature
      - expose lateral to the transverse processes
  - anterior approach
    - lumbar spine
      - anterior retroperitoneal or transperitoneal approach
        
        left paramedian incision
      - suitable for levels below L1
    - thoracolumbar junction
      - lateral lumbotomy
      - suitable for injuries at T11-L1
      - left-sided approach to avoid liver obstructing access
    - thoracic spine
      - lateral thoracotomy
        
        right-sided approach to avoid major vessels
        
        appropriate for injuries above T11
- technique
  - neural decompression
    - direct decompression
      - posterior decompression
        
        retropulsed bone can be removed via transpedicular approach
        
        usually done below the level of the conus medullaris (L2)
        
        significant dural retraction required, which may iatrogenically damage the cord
        
        avoid laminectomy if possible as it will further destabilize the spine by compromising the posterior supporting structures
      - anterior decompression
        
        corpectomy performed with direct removal of canal-occupying fragments
        
        ipsilateral pedicle and transverse process are removed
        
        corpectomy performed until the medial wall of the contralateral pedicle is visualized
        
        preferrable for fractures at or above the level of the conus medullaris (L1-2)
    - indirect decompression
      - distraction and lordosing rod construct leads to ligamentotaxis of the retropulsed fragments
        
        attachements of the annulus fibrosis and posterior longitudinal ligament to the fragments facilitates reduction
        
        less effective if performed 4-5 days after the injury
      - restored height and sagittal alignment with posterior instrumentation
      - monoaxial screws provided greater distractive forces for deformity correction
  - arthrodesis
    - posterior fusion
      - usually performed with locally harvested autograft and freeze-dried cancellous allograft +/- BMP
      - posterior instrumentation should be under distraction and lordosis to restore vertebral body height and achieve indirect decompression
    - anterior fusion
      - structural bone graft placed in corpectomy site to reconstitute the anterior column
        
        tricortical iliac crest autograft
        
        humeral or tibial allograft
        
        expandable metal cages with locally harvested autograft
      - can be stabilized with anterior instrumentation, posterior instrumentation, or both
- complications
  - posterior decompression
    - dural tear
    - iatrogenic cord injury
      - excessive thecal retraction above the conus medullaris
    - iatrogenic instability
      - laminectomy in the setting of disrupted posterior ligamentous complex
  - anterior decompression
    - ileus
      - transperitoneal approach to the lumbar spine
    - pleural effusion
      - related to approaches requiring thoractomy

COMPLICATIONS

Entrapped nerve roots and dural tear
- from associated lamina fractures
- can be iatrogenic from decompression
  - decreased risk of dural tears with anterior approach due to improved visualization of the thecal sac during decompression
- requires closure primarily or reinforced with dural patch
  - prolonged recumbency postoperatively
Pain
- most common
- over distraction with instrumentation
Progressive kyphosis
- common with unrecognized injury to PLL
- increased comminution of the vertebral body
  - loss of anterior column support
Flat back
- leads to pain, a forward flexed posture, and easy fatigue
- post-traumatic syringomyelia
Surgical site infection
- can occur in up to 10% of cases
  - trauma predisposes to infection
    - catabolic state
    - increased soft tissue damage
    - inflammatory response
- requires irrigation and debridement with culture specific antibiotics
Pseudoarthrosis
- can result from overdistraction instrumentation
Iatrogenic neurologic injury
- can occur in 1% of cases
- causes include
  - over medialized pedicle screws
  - inadvertant manipulation of the spinal cord