C-spine x-ray interpretation

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.

A: Adequacy

The C7/T1 junction must be visible

A: Alignment

Ensure all four lines are contiguous/uninterrupted

1. Anterior longitudinal line

2. Posterior longitudinal line

3. Spinolaminal line

4. Spinous process line

B: Bones

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

Pre-dental space

Normal <3 mm

>3 mm (XR) or 2 mm (CT) ?damage to transverse ligament

>5 mm implies rupture of transverse ligament

Basion-dental interval

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.