The Cervical Spine

1

Radiographic examination

• Minimum necessary views

  • Lateral cervical spine to include T1

  • AP cervical spine

  • AP open-mouth odontoid

• CT examination: minimum necessary

  • Axial, sagittal, and coronal noncontrast images in bone algorithm

    • Extending through at least the level of T1

  • Axial and sagittal images in soft tissue algorithm

2

Common sites of injury in adults

• Craniocervical junction (Skull base – C2)

  • Fractures

    • Occipital condyle

      • Atlas – C1

      • Posterior arch

      • Jefferson fracture – fractures of ring anterior and posterior

      • Anterior arch

    • Axis – C2

      • Odontoid (dens)

      • Body

        • Extension of dens fracture

        • Teardrop fracture

      • C2 pars interarticularis fractures – hangman’s fracture

  • Dislocations/subluxation

    • Atlanto-occipital dissociation

    • Atlanto-axial dislocation

• Lower cervical spine (C3-C7)

  • Fractures

    • Vertebral bodies

      • Compression, distraction, and translation/rotation injuries (SLIC)

        • Simple compression, anterior wedge

        • Teardrop

        • Vertical sagittal split of vertebral body

        • Burst

    • Lateral mass

      • Facets

      • Articular mass

      • Transverse process

    • Spinous process

    • Traumatic disc injuries

  • Dislocations/subluxations

    • Teardrop fracture dislocation

    • Distraction – ligament disruption

      • Intervertebral disc, joint capsules, and interspinous ligament

      • Anterior and posterior longitudinal ligaments

    • Facets – unilateral or bilateral – rotation, shearing injuries

      • Subluxed

      • Perched

      • Dislocated

3

Special considerations in the elderly

• Odontoid fractures common

  • Often combined with C1 arch fractures

• Spinal cord injury in presence of significant degenerative arthritis and disc disease

  • Often with either subtle or even without overt radiographic abnormality (SCIWORA)

  • Hyperextension teardrop

    • Fracture of inferior or superior anterior margins of vertebral body

    • Fracture of osteophyte at superior or inferior anterior margin of vertebral body

• Fractures in DISH (diffuse idiopathic skeletal hyperostosis)

4

Common sites of injury in children and adolescents

• Cervical spine injury ( CSI) rare in children under 8 years of age

  • Relatively more involve upper cervical spine

    • Craniocervical dissociation

    • C1 fractures

    • Dens fractures uncommon in children

      • Rare – apophyseal separations of synchondrosis between dens and body of C2

  • Spinal cord injury without radiographic abnormality (SCIWORA)

• At and beyond 14 years of age injuries similar to those of adults

  • Relatively more involve lower cervical spine, C4-C7

  • Vertebral body

    • Compression fracture

    • Teardrop fracture dislocation

5

Injuries likely to be missed

• Subtle fractures on radiography – need CT

  • Nondisplaced odontoid fractures

• Facet fractures

• Occipital condyle fractures

6

Where else to look when you see something obvious

• Avoid “satisfaction of search.”

• Find an injury at one level: closely evaluate the entire cervical spine above and below.

  • Multilevel discontiguous spine fractures

  • Fractures of C1 and C2 often associated with fractures of the lower cervical spine (C4-C7)

  • Two- or three-level fractures encountered in 20% of spinal fractures

    • CT entire T and L spine after identifying fracture of C-spine

• Find a compression fracture: look for associated posterior element injury.

• Find a vertebral body injury: look for bony compromise of spinal canal.

• Find a facet malalignment on one side: look for contralateral facet malalignment/fracture.

7

Where to look when you see nothing at all

• Obtain an MRI for those with neurologic signs and symptoms.

  • Spinal cord contusion

  • Herniated nucleus pulposus (HNP)

• Spinal cord injury without radiographic abnormality (SCIWORA)

  • Check width of spinal canal for spinal stenosis.

  • Spondylosis and degenerative changes in elderly

    • Check for evidence of hyperextension injury.

      • Teardrop fractures at anterior margins of vertebral bodies

      • Anterior widening of disc space

      • Prevertebral soft tissue swelling

• Review images.

  • Spinolaminar line

  • Interspinous distances

  • Closely evaluate prevertebral soft tissues for swelling.

  • Look for subtle fractures.

    • Facets

    • Transverse processes

    • Spinous processes

Preamble: Imaging Spinal Trauma

Though traditional and long the mainstay of cervical spine evaluation, radiographs of the cervical spine now have a limited role in the initial assessment of cervical spine trauma. Computed tomography (CT) was first introduced in the 1970s but did not prove adequate for the evaluation of the acutely injured spine until the early 2000s with the introduction and perfection of multidetector CT (MDCT), with rapid exposures coupled with the development of immediate and readily accomplished multiplanar image reconstructions. This permitted coronal and sagittal reconstructions of the entire length of the cervical spine in addition to the standard axial images. With these advances it became apparent that MDCT is more accurate and more efficient in the detection and depiction of spinal injuries.

The comparative difficulty of detection by radiography is shown by a fracture of the dens that is hard to see, if not impossible to identify, on the lateral cervical spine radiograph ( Figure 6-1 A ) but is clearly shown by the MDCT sagittal reconstruction ( Figure 6-1 B ). The associated fracture of the posterior arch of C1 is seen by both examinations ( Figure 6-1 A, C) .

It has been shown that up to 20% or more of cervical fractures disclosed by MDCT are unapparent, overlooked, or simply missed on plain film radiographs of the cervical spine. Thus, the American College of Radiology Appropriateness Criteria: Suspected Cervical Spine Injury states that MDCT, not radiography, is now the primary, preferred, and most appropriate method of imaging suspected cervical spine injury in patients older than 14 years.

1

Radiographic examination

• Minimum necessary views

  • Lateral cervical spine to include T1

  • AP cervical spine

  • AP open-mouth odontoid

The radiographic examination of the cervical spine should include a minimum of three views: lateral ( Figure 6-2 A ), AP ( Figure 6-2 B ), and AP open mouth of C1/C2 ( Figure 6-2 C ). Fractures and dislocations are best visualized on the lateral projection ( Figure 6-2 A ). Rotational injuries and fractures of the lateral masses may be evident on the AP projection ( Fig 6-2 B ). A few fractures of the ring of the atlas (C1) and the dens of the axis (C2) may be better visualized on the AP open-mouth view ( Figure 6-2 C ).

• Pattern of search: Lateral radiograph ( Figure 6-3 A )

  • Basion-dens interval

  • Atlanto-dens interval

  • Alignment of spine ( Figure 6-3 B )

  • Anterior spinal line (solid red line)

  • Posterior spinal line (dashed red line)

  • Spinolaminar line (dotted red line)

  • Interspinous distance (red dots)

    • Vertebral bodies configuration and alignment

    • Facet joints configuration, width and alignment

    • Prevertebral soft tissues

  • Pattern of search: AP radiograph ( Figure 6-4 A, B )

    • Alignment of spinous processes (thin red line)

    • Alignment of vertebral bodies (thick red lines)

    • Interspinous distance (red dots)

    • Undulant, smooth contour of the articular pillars (arrows)

    

  

Computed tomography (MDCT)

MDCT has superseded radiography for the initial assessment of older teenagers and adults because of the accuracy and ease of detecting injuries by MDCT in comparison to radiography. Therefore, when imaging is indicated, cervical spine MDCT is the initial diagnostic modality in all patients age 14 and older.

Sagittal CT search pattern ( Figure 6-6 )

• Right atlanto-occipital (occipital-C1) and atlanto-axial (C1-C2) joints ( Figure 6-6 A, B )

• Right lateral facet alignment and facet fractures ( Figure 6-6 A, B )

• Anterior spinal line and vertebral body heights ( Figure 6-6 C )

• Posterior spinal line ( Figure 6-6 C )

• Spinolaminar line ( Figure 6-6 C )

• Interspinous distances and posterior spinous processes ( Figure 6-6 C )

• Midline craniocervical junction alignment ( Figure 6-6 C )

  • Basion-dens interval

  • C1 anterior arch – dens interval

  • Opisthion (posterior margin of foramen magnum) – C1 posterior arch – C2 spinolaminar junction alignment

• Left lateral facet alignment and facet fractures

• Left atlanto-occipital (OC-C1) and atlanto-axial (C1-C2) joints

Axial CT search pattern ( Figure 6-7 A, B )

• 1.

  Vertebral body for fractures and uncovertebral joints

• 2.

  Transverse processes and transverse foramina

• 3.

  Pedicles

• 4.

  Facets (also referred to as articular pillars)

• 5.

  Posterior arch with laminae

• 6.

  Spinous process

Coronal search pattern ( Figure 6-8 A, B )

• 1.

  Occipital condyles

• 2.

  Facets and lateral masses (also referred to as articular pillars)

• 3.

  Transverse processes

  Spinous processes (not shown)

Soft tissue windows ( Figures 6-9 and 6-10 )

• Prevertebral soft tissues

• Paraspinous musculature for edema/ hemorrhage

• Tectorial membrane at craniocervical junction

• Spinal canal for disc injuries, epidural hematoma, bone fragments

It is important to view all images in both bone and soft tissue windows. Abnormal findings in the soft tissues point to underlying bone and joint abnormalities. The normal appearance of the soft tissue anatomy at the craniocervical junction is shown in Figure 6-9 A . Note the course and position of tectorial membrane extending from the clivus to the posterior surface of the dens. The posterior longitudinal ligament lining the spinal canal is seen on the posterior surface of the vertebral bodies, and the ligamentum flavum lining the posterior surface of the spinal canal is shown on and between the anterior surfaces of the laminae ( Figure 6-9 A ). Extradural hematomas pointing to underlying bone or joint abnormalities may be identified ( Figure 6-9 B ). In this case, the bone window clearly shows subluxation of the atlanto-occipital joint ( Figure 6-9 C ) as the cause of the extradural hematoma.

Bulging or herniated discs may be identified indicating the need for further evaluation by MRI ( Figure 6-10 ). This elderly patient sustained a type II fracture of the dens ( Figure 6-10 A ). Mid-sagittal recon soft tissue window image revealed a small hematoma about the fracture. Closer inspection revealed a rounded density at the posterior surface of the C3-4 disc space and a similar density posteriorly consistent with an enfolded, hypertrophied ligamentum flavum ( Figure 6-10 B ). The canal is constricted between these two densities. MRI confirms these findings ( Figure 6-10 C, D ). Note the herniated disc compressing the spinal cord ( Figure 6-10 D ). The spinal cord shows evidence of edema and/or myelomalacia. This proved to be important for preoperative planning. The fracture of the dens was reduced and pinned with single-screw fixation. An anterior discectomy was performed at C3-4 to relieve the pressure on the spinal cord. C3-4 was fused with placement of bone graft and a metal cage in the disc space.

Paraspinous musculature

Paraspinous muscular edema is a useful sign, when present, to indicate the presence of significant injury to the cervical spine soft tissues. However, edema takes time to develop, and the absence of paraspinous muscular edema does not exclude soft tissue injury. Evaluate the paraspinous soft tissues on a narrow CT window to visualize this finding optimally ( Figure 6-11 A ), confirmed on MRI in this patient ( Figure 6-11 B ).

Magnetic resonance (MR) evaluation

Indications for MR imaging in the cervical spine have expanded in recent years. For a patient with suspected cervical spine trauma, the American College of Radiology (ACR) appropriateness criteria recommend MRI evaluation of the cervical spine in addition to MDCT, especially when ligamentous or neurologic injury is suspected. ( ACR 2013 update ). The spectrum of spinal cord injury ranges from mild edema manifested by increased T2 signal in a patient without underlying myelomalacia, to severe edema, cord hemorrhage, and transection. Extensive cord signal change or compression on MRI, in a patient with only a partial or mild neurologic deficit, indicates a spinal cord at risk for further injury and a patient in whom aggressive management is warranted.

Integrity of the intervertebral disc and associated ligamentous structures is best evaluated with MRI. The anterior and posterior longitudinal ligaments, interspinous and supraspinous ligaments are assessed, in addition to the capsular ligaments of the facets. Imaging of the intervertebral disc can be complex, with annular fissures, disk protrusions and extrusions often difficult to date. Clinical history and physical exam findings are important in determining whether a disc protrusion is acute or chronic. A comprehensive review of cervical spine MRI is beyond the scope of this primer.

2

Common sites of injury in adults

• Craniocervical junction (skull base – C2)

  • Fractures

    • Occipital condyle

    • Atlas – C1

      • Posterior arch

      • Jefferson fracture – fractures of ring anterior and posterior

      • Anterior arch

    • Axis – C2

      • Odontoid (dens)

      • Body

        • Extension of dens fracture

        • Teardrop fracture

      • C2 neural arch – hangman’s fracture

  • Dislocations/subluxation

    • Atlanto-occipital dissociation

    • Atlanto-axial dislocation

Diagrams of the craniocervical junction ( Figure 6-12 A , 6-12 B , Clivus, C1 and C2) pinpoint the common sites of fractures and dislocations in adults. The most common sites of fracture are identified by red lines. Red arrows demonstrate displacement of the lateral masses of C1 indicative of simultaneous fractures of the anterior and posterior arches of the atlas (C1). Your pattern of search should include all sites.

Craniocervical junction injuries

Occipital condyle fractures

Occipital condyle fractures indicate disruption of the alar ligament, with or without other ligaments, at the craniocervical junction. The injury may be stable (unilateral ligament involvement) or unstable (bilateral involvement).

• Diagnosis : There are three major types ( Figures 6-13 and 6-14 ):

  • Type I: comminution of the occipital condyle without significant displacement

  • Type II: extension of a basilar skull fracture through the occipital condyle

  • Type III: avulsion of the occipital condyle with inferomedial displacement

  
  

Figure 6-15 is another type III fracture of the left occipital condyle shown in the axial ( Figure 6-15 A ), coronal ( Figure 6-15 B ), and sagittal ( Figure 6-15 C ) left lateral reconstruction images.

Atlanto-occipital dissociation

Mechanism

Atlanto-occipital dissociation is most commonly due to anterior dislocation of the head relative to the spine but may also be caused by longitudinal distraction or posterior dislocation. This injury is much more common in young children. Atlanto-occipital dissociation is usually fatal, particularly when widely displaced, but there are some survivors. Survival is three times more likely in children, principally in those with lesser injuries and displacement.

Diagnosis

Evaluate the alignment of the occiput relative to C1. The joint surfaces should be parallel. The width of atlanto-occipital articulation is generally ≤2 mm ( Figure 6-16 A, B ). Look for supporting findings, like soft tissue swelling at the craniocervical junction (see Figure 6-18 ) or joint asymmetry ( Figure 6-16 C, D ) compared with the contralateral side.

This patient demonstrates atlantal-occipital joint widening ( Figure 6-17 A ), posterior dislocation of the cervical spine ( Figure 6-17 B ), and an increased basion-dens interval ( Figure 6-17 C ).

An anterior atlanto-occipital dissociation, with fracture of the right occipital condyle, is demonstrated by anterior displacement of the dens and C1 ( Figure 6-18 A, B ) and an associated extradural hematoma at the foramen magnum ( Figure 6-18 B ). Note also a small avulsion from the tip of the dens ( Figure 6-18 B ). Axial ( Figure 6-18 C ) and right sagittal images ( Figure 6-18 D, E ) reveal a fracture of the right occipital condyle and anterior dislocation of the atlanto-occipital joint.

C1 ring fractures

C1 ring fractures may involve the anterior arch, the posterior arch, or both arches ( Figure 6-19 ). Fractures involving both arches are known as Jefferson fractures.

Posterior arch

Mechanism

Hyperextension of the head compressing C1 arch between occiput and neural arch of C2.

Diagnosis

The most common posterior arch fracture is a bilateral vertical fracture of the neural (posterior) arch ( Figures 6-20 and 6-21 ). However, this fracture must be distinguished from developmental defects, which have rounded, tapered, and corticated margins ( Figure 6-21 , black arrow). The latter is a congenital failure of fusion of the two limbs of the posterior arch in the midline, a common normal variant, associated with a dens fracture and bilateral fractures of the posterior arch in this patient ( Figure 6-21 ).

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