The ABCs of the cervical spine provide a helpful mnemonic to guide the systematic assessment of these x-rays. Remember, you need all three views (lateral, AP and odontoid/open mouth view) for an adequate study.
The C7/T1 junction must be visible
Ensure all four lines are contiguous/uninterrupted
1. Anterior longitudinal line
2. Posterior longitudinal line
3. Spinolaminal line
4. Spinous process line
Each vertebra 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
S: Spaces and lines
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 and 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.