How to Read Emergency Images

How to read a C-spine film

While emergency physicians are increasingly utilizing C-spine CT (especially in high-risk patients and those already getting a head CT), familiarity with the reading of the cervical spine x-ray is a skill that falls solidly within the scope of the ED physician. Below we will review the ten steps to reading a c-spine xray. One way to remember these steps is AAABBBCs.

Steps: Adequacy Alignment AADI (anterior atlantodental interval) BDI (bsion dental interval) Base of dens Bony abnormalities Cartilage disks Cartliage facets Soft tissues Scan the periphery

Step 1: Adequacy

Make sure that you can visualize the entire C spine to the C7-T1 interface.

Failure to visualize the seventh cervical vertebra and the CT/TI junction is the most common error made in the radiographic assessment of cervical spine injury.

Step 2: Alignment

Make sure there is no rotation present (rotation will be seen when left and right diamond-shaped lateral masses of each vertebra are not superimposed as below).


Make sure the the anterior longitudinal ligament line (also anterior vertebral line), posterior longitudinal ligament line (also posterior vertebral line), spinolaminar line and tips of spinous processes fall along a smooth and continuous line.

Step 3: AADI (anterior atlantodental interval)

Make sure the anterior atlantodental interval (also called pre-dental space) is less then 3 mm in adults and less than 5 mm in children.

Step 4: BDI (basion dental interval)

Make sure the basion-dens interspace is less than 12 mm (see examples below of a normal and abnormal BDI).

Step 5: Base of dens

Make sure the ring of C2 is smooth and continous.


Check for a "fat C2".


Step 6: Bony abnormalities

Inspect each bone (vertebral body, pedicle, articular mass, lamina, spinous process) from top to bottom.

*The majority of missed fractures are at the upper and lower cervical segments.

Step 7: Cartilage disks

Check for uniform disk spaces between vertebrae.

Cartilage Disks

Step 8: Cartilage facets

Make sure that the space between opposing facets is parallel and that joint space is uniform

Step 9: Soft Tissues

Make sure that the pre-vertebral tissue is within the expected size range.

  • 6 mm at C2
  • 22 mm at C6
  • Or above C4: soft tissues less than 50% of the width of a vertebral body
  • below C4 the limit is one full vertebral body width.
soft tissues

Step 10: Scan the periphery

  • Briefly view base of skull, mandibles, anterior neck
  • Also evaluate sinuses, occiput, mandible
  • Airway: epiglottis, hyoid bone, tracheal air shadow
  • Finally, check for foreign bodies

Open Mouth View

Same system for open mouth view

  • Adequacy/alignment: no overlap by teeth or skull base, dens, spinous process, lateral masses are all symmetrically aligned
  • Bones: base of dens, body of C2, C1 lateral masses
  • Cartilage: articular spaces between C1 and C2 are even and the image that's now there.
open mouth view

AP View

Same system for AP films

  • Adequacy/alignment: spinous processes midline and evenly spaced
  • Bones: vertebral bodies, uncinate processes, lateral masses, spinous processes
  • Cartilage: disk spaces uniform in height to the end
AP View