The ABC’s of the cervical spine provide a helpful mnemonic to guide the systematic assessment of these x-rays. Remember; you require all three views (lateral, AP and odontoid/open mouth view) for an adequate study.
The C7/T1 junction must be visible
Ensure all 4 lines are contiguous/uninterrupted
1. Anterior longitudinal line
2. Posterior longitudinal line
3. Spinolaminal line
4. Spinous process line
Each vertebrae must be examined for fracture/collapse/avulsion.
Parallel facet joints.
C: Cartilage (aka. disc spaces).
Examine for symmetry/normality of the intervertebral discs between each vertebrae
S: Soft tissue.
Prevertebral swelling of <2/3 of adjacent vertebral width
- <7 mm anterior to C2
- <2 cm anterior to C7
Spaces & lines (see examples below):
- Normal <3 mm
- >3 mm (XR) or 2 mm (CT) ?damage to transverse ligament
- >5 mm implies rupture of transverse ligament
A marker of occipito-atlantial dissociation
- <12 mm on x-ray or
- ≤8.5 mm on CT
Line of Swischuk
Helps differentiate pathological anterior displacement of the cervical spine (typically C2/3) from physiological displacement, termed pseudosubluxation.
A line is drawn between the anterior aspect of C1 & C3 spinous processes.
The anterior aspect of C2 spinous process should be within 2 mm of this line.
Deviation >2 mm: indicative of true subluxation.
Deviated <2 mm: consistent with pseudosubluxation
A: No subluxation. Therefore, posterior cervical line (PCL) cannot be applied. Anterior aspect of spinous process of C2 commonly misses PCL by 2 mm.
B: Subluxation is present. The anterior aspect of spinous process of C2 misses the PCL >2 mm. Finding is suggestive of a hangman’s fracture of the neural arches of C2.
C: Pseudosubluxation is present. The anterior aspect of spinous process of C2 touches or lies within 2 mm of PCL.
Take at this very early post from Loren Yamamoto too.
Now we’ve seen what’s normal, let’s consider the potential injuries using the mnemonic – Jefferson Bit Off A Hangman’s Thumb.
Burst fracture of C1.
Bilateral facet dislocation
A flexion distraction type of dislocation of the C-spine, often a result of buckling force.
Odontoid fracture (types II & III)
Specifically, types II & III.
Severe injuries including both atlanto-occipital dislocations and atlanto-occipital subluxations.
Bilateral lamina and pedicle fracture at C2 with anterolisthesis of C2 on C3. Associated with judicial hangings.
Tear drop fracture (extension)
Typically resulting in an avulsion of the anteroinferior corner of the vertebral body.
Often associated with central cord syndrome.
Any injury involving two or more of Denis’ columns are considered unstable. One of the more extreme examples of this is the ‘Chance fracture’, a flexion-distraction injury.
An anterior crush fracture of >50% loss of height in the thoracolumbar spine or >25% of the cervical spine is considered unstable.