Cervical, Thoracic and Lumbosacral Spine CT

Acquisition settings and contrast timings below are illustrative adult protocol examples. Select the authorized protocol for the indication, scanner, body size, access device, and clinical condition. Treatment decisions belong to the responsible clinical team.

Cervical & Thoracolumbar Spine Trauma CT

Computed tomography has replaced conventional projection radiography as the gold standard imaging modality for acute spine trauma. The complex anatomy of the spinal column, with its overlapping osseous rings, neural canals, and dense articular facets, produces severe projectional superimposition on plain films. Multidetector CT (MDCT) delivers rapid, volumetric, submillimeter spatial resolution that detects occult cortical disruptions, evaluates spinal canal encroachment by displaced bone fragments, and guides emergent surgical stabilization versus conservative immobilization.

Clinical Triage: NEXUS Criteria vs. Canadian C-Spine Rule

Because routine spinal CT involves ionizing radiation, clinicians use validated decision rules within their eligible populations to decide whether imaging is needed. These rules do not authorize a technologist to clear immobilization or force neck motion:

1. NEXUS (National Emergency X-Radiography Utilization Study) Low-Risk Criteria: A patient is classified as low risk and does not require cervical spine imaging if and only if all five of the following criteria are met:

   • Absence of midline posterior cervical spine tenderness upon direct palpation
   • Absence of focal neurological deficits (e.g., motor weakness, sensory loss, radiculopathy)
   • Normal level of alertness (Glasgow Coma Scale score of 15, no disorientation, responds appropriately to questioning)
   • No evidence of acute intoxication (blood alcohol, drugs, or clinical slurring)
   • Absence of distracting painful injuries (e.g., long-bone fractures, large burns, crush injuries, visceral trauma that would distract from neck pain)

2. Canadian C-Spine Rule (CCR): Evaluates high-risk factors that mandate CT regardless of examination:

   • High-risk factors requiring cervical imaging under the Canadian C-Spine Rule: Age $\ge 65$ years, dangerous mechanism of injury (e.g., fall from height $\ge 1\text{ meter}$ or $\ge 5$ stairs, axial load to head/diving, high-speed motor vehicle collision $\ge 100\text{ km/h}$, rollover, ejection, motorized recreational vehicle, or bicycle collision), or presence of paresthesias in extremities.
   • Low-Risk Factors (Permit Range-of-Motion Assessment): Simple rear-end motor vehicle collision, sitting position in the emergency department, ambulatory at any time, delayed onset of neck pain, and absence of midline cervical spine tenderness. If any low-risk factor is present, the clinician assesses voluntary neck rotation.
   • Range-of-Motion Test: Inability to actively rotate the neck $45^\circ$ to the left and $45^\circ$ to the right mandates CT imaging.

Scanning Coverage, Collimation & Windowing Protocols

• Anatomical Scan Range: For cervical spine CT, coverage must extend from the skull base / occiput through the T1-T2 vertebrae. Visualizing the cervicothoracic junction (C7-T1) is critical because the biomechanical transition from the mobile cervical lordosis to the rigid thoracic kyphosis represents a frequent site of high-energy traumatic fractures and subluxations that were historically missed on plain radiographs due to shoulder girdle attenuation (the classic failure of the radiographic "swimmer's view").
• Collimation & Acquisition Parameters: Thin, submillimeter detector collimation (typically $0.5\text{ to }0.75\text{ mm}$ slice thickness) is acquired with a low pitch ($<1.0$). Data are reconstructed in overlapping intervals (e.g., 1.2 mm reconstructed thickness at 0.6 mm intervals, giving 50% overlap) to generate isotropic voxels for multiplanar reformation (MPR).
• Reconstruction Algorithms & Windowing:
  • Sharp Bone Kernel / Algorithm: Rendered with an ultra-wide window width and high center: Bone Window (WW $2500\text{ HU}$, WL $+500\text{ HU}$). This displays the fine trabecular microarchitecture, subtle cortical hairline fractures, and facet joint alignment.
  • Smooth Soft-Tissue Kernel / Algorithm: Rendered with standard soft-tissue settings: Soft-Tissue Window (WW $350\text{ HU}$, WL $+40\text{ HU}$). This evaluates prevertebral soft-tissue swelling or hematoma (a prevertebral soft-tissue thickness at C2-C3 $>6\text{ mm}$ or at C6-C7 $>14\text{--}20\text{ mm}$ in adults can raise concern for injury but is not diagnostic; adult anatomy, position and technique affect the measurement), epidural hematomas, spinal canal stenosis, acute traumatic intervertebral disc herniation, and spinal cord compression.
  • Multiplanar Reformations: True axial slices reconstructed parallel to the adjacent intervertebral disc spaces, coupled with true sagittal and coronal MPRs aligned along the longitudinal curvature of the vertebral bodies.

Denis Three-Column Spinal Classification & Instability

The Denis three-column classification divides the spinal motion segment into three structural columns:

1. Anterior Column: Comprises the anterior longitudinal ligament (ALL), the anterior two-thirds of the vertebral body, and the anterior two-thirds of the annulus fibrosus.
2. Middle Column: Comprises the posterior one-third of the vertebral body, the posterior one-third of the annulus fibrosus, and the posterior longitudinal ligament (PLL).
3. Posterior Column: Comprises the posterior osseous arch (pedicles, laminae, transverse processes, articular facet pillars, and spinous processes) and the posterior ligamentous complex (PLC: ligamentum flavum, interspinous ligament, supraspinous ligament, and facet capsular ligaments).

Column-based descriptions help communicate which spinal structures are injured, but injury to two columns is not a universal automatic surgical indication. Describe alignment, vertebral body, posterior wall, posterior elements and canal compromise, and follow the treating team's stability assessment. C1 lateral-mass displacement raises concern for ligament injury, but a displacement rule alone cannot reliably establish or exclude transverse ligament rupture; additional assessment may be required.

High-Yield Cervical Spine Fracture Patterns

• Jefferson Burst Fracture of C1 (Atlas):
  • Mechanism: Severe axial compressive loading directed downward onto the vertex of the skull (e.g., diving into shallow water, head-on football impacts).
  • CT Manifestations: Comminuted burst fracture disrupting both the anterior and posterior arches of the C1 ring, with lateral divergent displacement of the C1 lateral masses relative to the articulating superior facets of C2.
  • The Rule of Spence: Evaluates the competence of the transverse atlantal ligament (TAL). On coronal reformatted CT, the combined lateral overhang of both C1 lateral masses beyond the lateral margins of the C2 articular pillars is measured. Increased combined displacement raises concern for transverse ligament injury, but the historical displacement rule cannot reliably establish or exclude rupture. Follow the clinical team’s further assessment.
• Hangman's Fracture (Traumatic Spondylolisthesis of the Axis, C2):
  • Mechanism: Violent hyperextension combined with axial distraction (e.g., chin striking the dashboard in high-speed MVC, judicial hanging).
  • CT Manifestations: Bilateral fractures passing vertically through the pars interarticularis (or pedicles) of C2. This mechanically separates the anterior C2 vertebral body from the posterior neural arch, resulting in variable anterior subluxation of the C2 body over C3.
• Odontoid / Dens Fractures (Anderson and D'Alonzo Classification):
  • Type I ($<5\%$): Oblique avulsion fracture of the apex of the odontoid process at the insertion of the alar ligament. Mechanically stable; heals well with collar immobilization.
  • Type II ($>60\%$): Transverse fracture through the waist / base of the odontoid process where it merges with the C2 vertebral body. This is a highly unstable injury with a notorious nonunion rate ($>30\%\text{ to }40\%$) due to a tenuous watershed microvascular blood supply. Often mandates halo vest immobilization or surgical stabilization (anterior odontoid screw fixation or posterior C1-C2 fusion).
  • Type III (frequency varies by population): Fracture line extends downward into the rich cancellous bone of the C2 vertebral body itself. Because the cancellous vertebral body has abundant blood supply and a large surface area, Type III fractures demonstrate a high union rate ($>90\%$) and can frequently be managed with external halo or rigid collar immobilization.

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Routine cervical, thoracic and lumbosacral questions

A cervical reconstruction follows the vertebral bodies, facets, disc spaces and neural foramina through the cervicothoracic junction. Thoracic data need level identification with the ribs and assessment through the ordered thoracolumbar junction. Lumbosacral images relate the lumbar bodies and discs to the sacrum, with oblique axial views through the relevant disc or foramen when requested. Numbering variants require careful correlation; do not assign a level from one isolated slice.

For degenerative or postoperative questions, use thin bone images for osteophytes, facets, fusion and hardware, and suitable soft-tissue images for surrounding tissues. CT depicts osseous canal narrowing but does not replace MRI for every spinal cord, ligament or nerve-root question. An ordered postmyelographic CT follows separately administered intrathecal contrast and evaluates the opacified thecal sac and roots; routine IV contrast is not equivalent. Preserve positioning restrictions after the procedure and follow the supervising instructions.

Thoracic and lumbar trauma acquisitions may be reconstructed from adequately acquired body data if the approved protocol supports the needed detail, avoiding duplicate exposure. Verify coverage and quality rather than assuming that any thick body series is sufficient. Describe vertebral alignment, posterior wall fragments, canal compromise and posterior elements without independently assigning a treatment plan.

Reference: ACR spine CT practice parameter.