Thoracolumbar Burst Fractures - Spine

SUMMARY
- Thoracolumbar Burst Fractures are a common high-energy traumatic vertebral fractures 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.
- Diagnosis is made with radiographs of the thoracolumbar spine. CT scan is useful for fracture characterization and surgical planning.
- 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.

Epidemiology
- Demographics
  - often seen from falls from height or motor cycle accidents

ETIOLOGY
- 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
    
    associated with
    
    lamina fractures
    
    split 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
    
    assess the presence of a posterior ligamentous injury
    
    should be performed in nearly every case, unless radiographs and CT clearly suggest injury
  - 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 extend 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