Anatomy

The thoracolumbar spine is composed of 12 thoracic vertebrae and 5 lumbar vertebrae. The sacrum is formed by five fused vertebrae, and the coccyx by four fused vertebrae. The upper thoracic spine (T1–T10) is more rigid, owing to rib cage stabilization, and the structure of the vertebrae limit rotation, flexion, and extension. Injury in this area is associated with a substantial mechanism. The spinal canal in the thoracic spine is also narrower, leading to a higher proportion of complete spinal cord injury when injury does occur. The thoracolumbar junction (T11–L2) is a transitional zone between the thoracic and lumbar vertebral anatomy that is highly flexible and constitutes approximately 50% of thoracolumbar injuries.^{1, 2} The lower lumbar spine (L3–L5) is wider, owing to its weight bearing role, and the lumbar canal is also wider with less frequent spinal cord injury.

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  The thoracic spine is least likely to have injury but will have the highest proportion of complete spinal cord injury.

  
  
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  The transitional zone (T11–L2) is most susceptible to injury.

  
  
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  The lower lumbar spine has the lowest proportion of complete spinal cord injury.

The spinal cord exits the skull through the foramen magnum and terminates in the conus medulla, at approximately the L1 level. The nerve roots of the corresponding vertebra exit below the vertebra. The final filament of the spinal cord is the filum terminale and attaches to the sacrum to anchor the spinal cord. The filum terminale and remainder of nerves ending past the conus medulla constitute the cauda equina.²

Spinal cord injury can be described as complete and incomplete lesions. Complete spinal cord injury is defined as the complete loss of motor and sensory function below the injury. Incomplete spinal cord injury will have partial deficits of sensory or motor function. The American Spinal Injury Association (ASIA) defines these terms in greater detail:³

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   A. Complete: No sensory or motor function is preserved in sacral segments S4–S5

   
   
2. 
   

   B. Incomplete: Sensory, but not motor, function is preserved below the neurologic level and extends through sacral segments S4–S5

   
   
3. 
   

   C. Incomplete: Motor function is preserved below the neurologic level, and most key muscles below the neurologic level have a muscle grade of less than 3

   
   
4. 
   

   D. Incomplete: Motor function is preserved below the neurologic level, and most key muscles below the neurologic level have a muscle grade that is greater than or equal to 3

   
   
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   E. Normal: Sensory and motor functions are normal

Three principle spinal tracts are involved in partial and complete spinal cord injuries: corticospinal lesions, spinothalamic lesions, and dorsal column lesions (Figure 11.1).

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  Corticospinal lesions (A) are upper motor lesions with ipsilateral muscle weakness, spasticity, and increased deep tendon reflexes at the level of the lesion.

  
  
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  Spinothalamic lesions (C) involve the loss of pain and temperature contralateral to the lesion and one to two levels below the injury.

  
  
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  Dorsal column lesions (B) involve ipsilateral loss of vibratory and positional sense at the level of the lesion.

Figure 11.1 Spinal tracts

Pre-Hospital Management

Despite a lack of strong evidence, any patient with suspected thoracolumbar injury should be transported with a long backboard.

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  Patients should be considered at risk for injury with complaints of pain in the spine, neurologic deficits, altered mental status or intoxication, or with a concerning mechanism (Box 11.1).

  
  
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  Prolonged backboard use is known to cause bedsores, induce respiratory compromise, and cause patient discomfort, thus removal should be prompt once in the emergency department.⁴

  
  
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  With continued concern for thoracolumbar trauma, strict log roll precautions should be maintained.

Examination of Suspected Thoracolumbar Trauma

After initial stabilization of a trauma patient, a thorough secondary physical exam should be obtained. This should include palpation of the spine for step offs and deformities, motor function of all major muscle groups, sensory testing, and a digital rectal exam (Table 11.1). Examination of the perineum may demonstrate decreased sensation, loss of rectal tone, or priapism, all suggesting spinal cord involvement.⁵

It is important to note the physical exam alone may not have high sensitivity and specificity for identifying injury. One study found that 52% of known thoracolumbar injuries demonstrated abnormal clinical exam findings, including tenderness to palpation. Furthermore, when pain was elicited, it was in an inaccurate location almost 40% of the time. Injuries of higher severity were more likely to have positive exam findings, with the highest sensitivity and specificity reported at 79% and 84%, respectively.⁶

Muscle strength can be graded on a scale from 0 to 5, as defined by ASIA,³ and reflexes should be assessed (Tables 11.2 and 11.3). Loss of reflexes or tendon jerks implies a complete spinal cord lesion, whereas spasticity or increased tone may suggest a partial cord lesion.

Imaging Thoracolumbar Trauma

Imaging the spine is indicated in patients with severe pain, bony tenderness, palpable subluxations, neurologic deficits, or a concerning mechanism of injury. Concomitant injury and mechanism of injury are important because physical exam alone, including tenderness to palpation, may be normal in up to 40% of patients.⁵

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  The modality of choice is computed tomography.^{5, 7} This modality has the highest resolution of bony abnormalities and should be the initial form of imaging.

  
  
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  Plain films have a lower sensitivity and are liable to miss injury.⁵ Furthermore, plain films are unable to fully visualize the middle and posterior columns and have even lower sensitivity in obese patients.

  
  
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  If any spinal injury is found, a low threshold should be had to image the entire spine; up to 15% of injuries will have additional injuries.^7–9

  
  
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  While CT is the modality of choice for bony injury, if ligamentous or neural injury is suspected, an MR should be ordered. This is typically done in consultation with a spine specialist.

Classification

The most common way to describe fractures of the spine is with the three-column system (Figure 11.2). This system assumes stability of a fracture when only one column is involved; however, clinical judgment should be used.^10–14

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  Anterior column: from the anterior longitudinal ligament through the anterior two thirds of the vertebral body.

  
  
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  Middle column: from the posterior third of the vertebral bodies through the posterior longitudinal ligament.

  
  
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  Posterior column: from the facets through the spinous ligament.

Figure 11.2 The three column classification system

Injury Patterns (Table 11.4)

Compression Fractures

These are the most common form of fracture and are most often due to flexion of the spine or axial compression. This pattern also represents the most common elderly fragility fracture, affecting 50% of patients over 80 years old (Figure 11.3).

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  Fractures most commonly occurs in the anterior column and may result in the failure of the anterior longitudinal ligament. These fractures are almost always stable unless there is a loss of height greater than 50% or loss of integrity of the posterior longitudinal ligament.^11–14

  
  
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  Management of smaller deformities (20–30% compression) typically involves pain control, increasing levels of activity, and physical therapy. Some practices may involve a spinal surgeon for bracing recommendations.^{13, 14}

  
  
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  Injuries with greater degrees of compression or any neurological symptoms require consultation with a spinal specialist.

Table 11.4 Fracture classification

Fracture	Mechanism	Stability	Management
Compression fracture	Flexion or compression	Stable if <50% and no neuro symptoms	Pain management, possible bracing, possible consultation
Burst fracture	Compression	Unstable	Spinal precautions, spine consultation
Chance fracture	Flexion-distraction	Unstable	Spinal precautions, spine consultation
Translational injuries	Shearing forces	Unstable	Spinal precautions, spine consultation
Transverse process fracture	Multiple mechanisms	Stable	Pain control
Spinous process fracture	Multiple mechanisms	Stable	Pain control
Pars interarticularis fracture	Multiple mechanisms	Stable	Pain control

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Chapter 5 – Pediatric Trauma Chapter 6 – Geriatric Trauma Chapter 7 – Head Trauma Chapter 10 – Cervical Spine Trauma Chapter 13 – Pulmonary Trauma Chapter 20 – Lower Extremity Trauma