General Principles (Thoracic Spine)


General Concepts

Background

  1. Least often injured spinal area
  2. Anatomy
    • 12 thoracic vertebrae
    • 5 lumbar vertebrae
  3. Significant number of injuries
    • 50% of all vertebral body fractures
    • 40% of all spinal cord injuries
    • Neuro deficit in 15-20%
  4. Causes
    • MVA (45%)
    • Fall (20%)
    • Sports (15%)
    • Violence (15%)

Pathophysiology

  1. Most fractures occur in lower thoracic vertebrae
    • Upper spine (T-1 to T-10) more stable
      • Stabilized by ribs
      • Stabilized by orientation of spinal facets
  2. T/L junction (T-11 to L-2)
    • Very susceptible to injury
    • T/L spine is LESS capable of lateral bending than C-spine
      • Decrease in rib restraint
      • Changes in spine stiffness
        • Flexion-extension
        • Rotation
      • Changes in disc size / shape
  3. Three-column concept
    • Spine viewed as having 3 "columns" 
      • Some suggest a 4th column for the T-spine
    • Anterior column
      • Anterior longitudinal ligament
      • Anterior 1/2 of body, disc, and annulus
    • Middle column
      • Posterior 1/2 of body, disc, and annulus
      • Posterior longitudinal ligament
    • Posterior column
      • Facet joints
      • Ligamentum flavum
      • Posterior elements
      • Interconnecting ligaments
    • 4th column (proposed for T-spine)
      • Sternum-rib complex
      • NOT yet accepted



         
  4. Injury mechanisms
    • Axial load
    • Flexion
    • Lateral compression
    • Flexion-rotation
    • Shear injuries
    • Flexion-distraction
    • Extension
  5. Common fracture types
    • Compression fracture
      • Anterior column fails
      • Middle column remains intact
      • Examples:
        • Simple compression Fx
        • Wedge Fx
    • Burst fractures
      • Usually found in thoraco-lumbar spine (T10 - L2)
      • Less common in thoracic spine
      • Involve failure of both anterior and middle columns
      • Are comminuted fractures of vertebral bodies
        • Often have fragments in spinal canal
      • Usually from high-energy impact & vertical loading
      • Usually result in neurologic deficits
    • Fracture-dislocation
      • Include any fracture with dislocation
      • All three columns fail
      • Usually from compression, tension, shear, or rotation
      • Variants
        • Anterior/posterior dislocation of vertebral body with fracture of bony parts
        • Comminuted fractures of vertebral body WITH
          • Anterior/ posterior displacement and rotation
        • Lateral dislocation of vertebrae with fracture
      • All fracture - dislocations cause potentially devastating neurologic injuries
    • Chance fracture
      • A flexion-distraction injury
      • Usually from hyperflexion of spine
      • All three columns fail
      • Fracture includes
        • Vertebral body
        • Pedicles, lamina
        • Spinous process
        • Posterior ligaments (disrupted)
        • Intervertebral disc and facet joints may be distracted
      • 15-20% incidence of intra-abdominal injury
        • Pancreas
        • Duodenum
        • Proximal small bowel
  6. DENIS classification system for fractures
    Note: This is a simplification of the complete system. It is a generalization to help practitioner conceptualize and sort injuries
    1. Many systems exist
      • Denis system
      • McCormack system
      • AO system
    2. Denis classification system most commonly used
    3. Same for thoracic and lumbar injuries
      • Significant fractures put into four (4) groups
      • Three levels of instability listed
      • 4 injuries are considered minor fractures

    Major Injuries

    1. Compression fractures
      • Anterior column injuries
      • Middle column is INTACT
      • Subtypes
        • Fx in frontal plane 
        • Fx of anterior superior end plate 
        • Fx of anterior inferior end plate

           
        • Fx of both endplates




           
    2. Burst fractures
      • Anterior AND middle column injuries
      • Retropulsion of bone into spinal canal
      • Subtypes
        • Fx of both end plates
        • Fx of superior end plate
        • Fx of inferior end plate
        • Burst rotation
    3. Flexion-distraction injury
      • Injury to all three columns
        • Posterior and middle columns fail under tension
        • Anterior column serves as a fulcrum
      • Subtypes
        • One level bone injury
          • Type A (Chance Fx)
        • One level ligamentous injury
          • Type B
        • Two level through bony middle column
          • Type C
        • Two level through ligamentous middle column
          • Type D
    4. Fracture-dislocation
      • Injury to all three columns
      • Subtypes
        • Flexion-rotation (Type A)
        • Shear (Type B)
        • Flexion-distraction (Type C)
          • Bilateral facet dislocation

    Degrees of instability

    1. First-degree instability
      • Mechanical instability with risk of progressive kyphosis
      • Applies to
        • Severe compression Fx with posterior column disruption
        • Some seat-belt injuries
    2. Second-degree instability
      • Neurologic instability
      • Applies to
        • Burst Fx
    3. Third-degree instability
      • BOTH mechanical and neurologic instability
      • Applies to
        • Fracture-dislocations
        • Unstable burst fractures

    Minor Injuries

    1. Isolated articular process fractures
    2. Transverse process fractures
    3. Spinous process fractures
    4. Pars interarticularis fractures


     

 

 

Anatomy and Stability

ANATOMY OF SPINE

  1. Vertebral body
    • Weight-bearing part
  2. Neural arch: protects spinal cord and cauda equina
  3. Transverse processes: attachments for soft tissue structures
  4. 3-spinal "columns" make up support mechanism 
    • Anterior column
      • Anterior longitudinal ligament
      • Anterior 1/2 of body, disc, and annulus
    • Middle column
      • Posterior 1/2 of body, disc, and annulus
      • Posterior longitudinal ligament
    • Posterior column
      • Facet joints
      • Ligamentum flavum
      • Posterior elements
        • Pedicles
        • Laminae
      • Interconnecting ligaments
    • 4th column (proposed for T-spine)
      • Sternum-rib complex
      • NOT yet accepted
  5. Spinal tracts
    • Anterior cord spinothalamic tract
      • Pain
      • Temperature
      • Light touch
      • Fibers cross midline when they enter the cord
    • Posterior cord fasciculus gracilis and cuneatus tracts
      • Positional sensation
      • Fibers do not cross
    • Anterior cord corticospinal tract
      • Motor fibers
      • Fibers cross in the lower brainstem
    • Posterior column tracts
      • Vibration
      • Proprioception
      • Stereognosis
      • Light touch
  6. Spinal nerves exit through intervertebral foramina
    • Formed by inferior aspect of the pedicle above and superior aspect of the pedicle below
    • Disc disease affects nerve exiting one level below
  7. Spinal cord ends at L1
    • Inferior to L1 are the cauda equina

"STABILITY"

  1. Stability is lost when two columns are compromised adjacently
     
  2. If any fracture found
    • High probability of second fracture (> 30%)
    • Carefully evaluate remainder of entire spine
       
  3. Unstable fracture defined as
    • 2 or 3 columns disrupted
    • Neurological deficit present
       
  4. Usually unstable fractures:
    • >50% decrease in vertebral body height
    • Angulation >20 degrees between vertebrae
    • Fracture/ dislocations

 

Injury Mechanisms

Axial Compression 
  1. Most often causes thoracolumbar burst Fx
  2. Injury forces
    • Usually causes anterior flexion load on vertebra
      • Due to natural kyphosis of area
      • See flexion injuries for more detail
    • May see pure compressive loading of vertebrae
      • Usually in straight thoracolumbar region
    • Sequence of damage (with increasing force)
      • End-plate failure
      • Compression fracture
      • Burst fracture
      • Centripetal displacement of bone
        • Disc fragmentation
      • Posterior element disruption

Flexion 
  1. General principles
    • Usually causes STABLE anterior compression Fx
      • Occurs along vertebral bodies & discs
  2. Injury forces
    • Flexion forces to anterior vertebral body
    • Tensile forces can develop posteriorly
      • May NOT see posterior ligament tears
      • MAY see posterior avulsion fractures
    • Force dissipates anteriorly as bone fractures
    • Fractures can be stable or unstable
  3. Usually STABLE Fractures
    • Posterior ligaments intact
    • Middle column remains intact
  4. Possibly UNSTABLE Fractures
    • Posterior ligaments / facet capsules disrupted
      • ASSUME UNSTABLE Fx if Anterior compression > 40-50%
    • Flexion-compression Fx with middle element failure
      • High potential for instability


Lateral Compression 
  1. Usually cause STABLE lateral compression Fx
  2. Injury forces
    • Similar to anterior wedge fractures
      • Force is applied laterally
    • Usually limited to vertebral bodies
  3. MAY occasionally see posterior ligament injury
    • These may be chronically UNSTABLE fractures

     

Flexion-Rotation 
  1. Combination of flexion and rotation forces
    • Mining accidents
    • Falls from height
    • MVA with ejection from vehicle
  2. More likely to produce serious injuries than flexion alone
    • Posterior ligament / joint capsule disruption
    • Oblique anterior disc / vertebral body disruption
  3. Injury forces
    • Predominant injury is anterior bone disruption from flexion
    • Ligaments / facet capsules fail as rotational forces increase
    • Anterior and posterior columns then fail
    • VERY UNSTABLE injury develops
      • Posterior ligaments / joint capsules rupture
      • Anterior disc / vertebral body are disrupted obliquely
      • Can result in classic "slice" fracture
    • PURE DISLOCATIONS ARE RARE
      • Facet size and orientation make dislocation difficult
      • Can occur if facet Fx / posterior element disruption


Flexion-Distraction 
  1. Typical "seat belt" injury
    • Often causes Chance Fx
  2. Injury forces
    • Compression forces across anterior vertebral body
    • Distraction forces across middle column and posterior elements
    • Axis of flexion is moved anterior
      • Toward anterior abdominal wall
    • All of vertebral column experiences large tensile forces
      • Tissues are torn / avulsed, NOT crushed as usual
        • Bones, discs, ligaments
  3. Can produce various injury groups
    • Pure osseous (bone) lesion
      • Classic "Chance Fx"
        • Horizontal fracture
        • Usually in L-1 to L-3 region
        • Starts in spinous process
        • Goes through lamina, transverse processes, pedicels, vertebral body
        • Acutely UNSTABLE injury
        • Good healing potential
    • Mixed osteoligamentous lesion
      • Ligaments and bones injured
      • Usually in T-12 to L-2 region
      • UNSTABLE injuries
      • Poor healing potential
    • Pure soft tissue lesions
      • Soft tissues ONLY injured
        • Ligaments
        • Discs
      • Usually in T-12 to L-2 region
      • UNSTABLE injuries
      • Poor healing potential
  4. Can cause bilateral facet dislocation in T-L or L spine
    • See subluxation on X-ray
    • Ligaments, joint capsules, discs are disrupted
    • Anterior longitudinal ligament usually stays intact
    • If anterior longitudinal ligament is disrupted:
      • VERY UNSTABLE injury
      • Usually more of a pure flexion injury

     

     

Shear 
  1. Causes ligamentous disruption
    • Similar to flexion-rotation injuries
    • Force directed across long axis of trunk
      • "Lumberjack" Fx
  2. Injury forces
    • Forces from different directions pass through spine at different levels
  3. Often works with other forces to cause complex injuries
  4. May cause spondylolisthesis of superior vertebral segments on inferior ones
    • Can be anterior, posterior, or lateral
    • Anterior is most common
      • Usually see complete spinal cord injury
      • May get fracture through pars interarticularis
        • Results in autolaminectomy
        • May have neural sparing

 

 

Extension
  1. Occur when head / upper trunk forced posteriorly
  2. Injury forces
    • Reverse of flexion forces
      • Tension forces on anterior longitudinal ligaments / anterior part of annulus fibrosis
      • Compression forces on posterior elements
    • Injuries produced
      • Fractures of facet, lamina, and spinous process
      • Avulsion fractures of anteroinferior part of vertebral bodies
        • NOT pathognomonic of extension forces
  3. Most injuries are STABLE
    • NOT if significant retrolisthesis of upper vertebral body on lower vertebral body
    • NOT if combined with shear forces

 

T/L Spine Imaging

Indications for Imaging

  1. Pain
  2. Neurologic deficit
  3. Distracting injuries
  4. Altered consciousness
    • Head injury
    • Intoxication
    • Pharmaceutical intervention
  5. High-risk mechanism of injury
  6. All are appropriate and sensitive indicators

Plain X-Rays

  1. Indications
    • Initial study of choice
    • AP and lateral films should be the first ones obtained
  2. General principles of evaluation
    • Follow ABCs when evaluating films
      • Alignment
      • Bony integrity
      • Cartilage / Joint space injury
      • Soft tissue injury indicators
  3. AP View (T-spine)
    • Best view of contour of spinal column
    • Shows outline of vertebral bodies
    • Can take in erect OR supine position
    • Film requirements
      • Must see all 12 thoracic vertebrae
      • Exposure must penetrate vertebral bodies
        • Upper thoracic vertebrae should not be "burned out"
      • Include C-7 vertebra
        • Evaluate subluxation of upper T-spine
      • Include L-1
        • Evaluate subluxation of T-L junction
      • Lateral margins must include
        • Entire transverse processes
        • Small portion of the ribs
    • Medial to lateral, note:
      • Spinous process
      • Intervertebral foramina
      • Pedicles
      • Articular facet joint
      • Transverse processes
    • Check
      • Height of vertebral bodies
      • Distance between pedicles
      • Alignment of vertebral bodies
      • Alignment of spinous processes
        • All should be in midline
  4. Lateral View (T-spine)
    • Best view of vertebral bodies
      • CANNOT see upper thoracic vertebrae adequately
        • Shoulder superimposed
      • Need Fletcher view to see
        • Must specifically ask for
    • Can take in erect or supine position
    • Film requirements
      • Must see all 12 vertebrae
        • Lateral view
        • Swimmer's view for C-7 to T-4
      • All vertebrae must be penetrated
      • Spinous processes may be partially cut off
    • Shows:
      • Spinal curves
      • General shape of vertebral bodies
      • Note
        • Spinous process
          • Inferior articular facet
          • Transverse process
          • Superior articular facet
        • Pedicle
        • Body
      • Check
        • Anterior and posterior vertebral body height
        • Vertebral body alignment
        • Intervertebral disc space
        • Interspinous distance
          • Should be equal
          • Unequal = possible ligament disruption
  5. Oblique Views: (T-spine)
    • Views neural foramina
    • Views pedicles
      • "Scotty Dog": "face/eye" is pedicle, "ear" is articular facet joint, "nose" is transverse process, "body" is the lamina, "neck" is the isthmus or pars articularis (spondylolysis site)
      • Look for fractures
  6. AP View (L-Spine)
    • Must see T-12 and all of L-S spine
    • Must see both sacroiliac joints
    • Should penetrate vertebral bodies and spinous processes
    • Soft tissue details
      • Psoas muscles
      • Bowel gas pattern
      • Urinary bladder
         
  7. Lateral View (L-Spine)
    • Patient supine
    • Patient supported on backboard
    • All of L-S spine should be penetrated
    • Usually require second L-5 / S-1 View
  8. Lateral L-5 / S1 & Sacrum
    • Patient supine
    • Patient supported on backboard
    • Should see end of coccyx

CT Scan

  • Can see spinal canal
  • Can see bones, soft tissue, discs
  • Indications
    • Contrast CT in most patients
    • Exclude intrathoracic vascular injury
  • Coned down views or CT's in area of deficit or abnormality on plain films
  • CT-visualizes posterior elements as well

MRI

  • Provides best evaluation of soft tissue pathology
    • Essentially the ONLY direct evaluation of the spinal cord
    • Cord compression
    • Canal / foraminal compromise
    • Disks, ligaments
    • Hematomas
       
  • Indications
    • Patients with neurologic deficits
    • Patients with spinal canal compromise UNABLE to provide neuro Hx
       
  • If use STIR or fat-saturated T2-weighted sequences
    • May help determine acute injuries
    • May see other regions of bone edema
       
  • If use high-resolution and heavy T2-weighting
    • May see nerve root avulsions
    • May see pseudomeningocoele
    • Can also potentially visualize posttraumatic sequelae
      • A-V fistulas
      • Myelomalacia
      • Cord tethering

Myelogram or CT Myelogram

  1. Rarely used now
  2. MRI just as good or better in most situations
  3. Invasive procedure
  4. Used if
    • MRI unavailable
    • MRI impossible
      • Patient too contracted, metal issues, etc

Nuclear Medicine Scan

  1. Very rarely used
  2. Can help show if old or new fracture

 

Diagnosis

  1. History
    • Mechanism of injury
      • MVC, sports, etc.
    • ANY paresthesias, weakness, paralysis, pain
      • Even if transient
  2. Physical exam
    • Complete general physical
  3. Trauma neuro exam
    • Re-assess frequently
    • Spinal cord injury
      • Complete
        • No motor/sensory function below the level of the injury
      • Incomplete
        • Partial motor/sensory function
  4. Diagnostic testing
    • Lab evaluation
      • Trauma labs as indicated


 

Treatment/Disposition

Acute Treatment

  1. Trauma ABCs
  2. Immobilization
    • Prehospital
      • Back board, c-collar
      • Head blocks or tape
    • ED
      • Keep patient supine and immobile
        • Unless low suspicion of injury
      • Cooperative patient - talk to them
      • Uncooperative patients
        • More aggressive measures
        • Sedation/ intubation
  3. If intubation required
    • RSI with inline stabilization
  4. Continue with primary survey
    • Stabilize patient
    • NEVER assume
      • Spinal shock
      • Neurogenic shock
      • Diagnosis of exclusion
  5. For spinal cord injury:
    • Start methylprednisolone
      • 30 mg/kg initially THEN
      • 5.4 mg/kg/hr for 24 hr
      • Discuss with Neurosurgery
    • MAY improve neurologic recovery if started w/in 8 hrs
  6. Other issues
    • Remove patient with a fractured spine from the backboard within 2 hr
    • Move to rotary bed (stryker) to avoid skin breakdown
  7. Reduction of fracture (Neurosurg / ortho)
    • Cervical or upper thoracic
      • Gardener-Well tongs
    • Thoracic or lumbar
      • Placement of pillows on stryker frame

Disposition

  1. Admit
    • Essentially ALL spine fractures
      • Small compression fx's may be able to go home
        • Discuss with PMD / Ortho / Neurosurg first
    • Admit for
      • Observation
      • Assessment of stability
      • Pain control
      • Paralytic ileus frequently occurs
  2. Surgical intervention (reduction/ decompression/ fusion)
    • Emergent/ Urgent
      • Incomplete injury with worsening neuro exam
      • Incomplete deficits with an irreducible fracture
      • Severely unstable fracture with complete deficit
        • Allows earlier mobility
    • Non-emergent surgery
      • Usually done in 9-12 days
      • Mainly for stability and more rapid mobilization