Odontoid fracture (Anderson and D'Alonzo type 3, Roy-Camille type 1)

Case contributed by Assoc Prof Craig Hacking


High speed MVA.

Patient Data

Age: 75 years
Gender: Male

Acute oblique fracture through the base of C2 dens extending to the body and bilateral lateral masses as well as the right transverse foramen. Fracture line separation with cortical steps of up to 3 mm (anterior displacement of the dens with respect to C2 body). C2 left lateral mass lateral cortex sits 3 mm lateral to C1 lateral mass. Mild prominence of prevertebral soft tissues at this level and measures up to 5 mm AP, which remains within normal limits. No obvious epidural thickening demonstrated on CT.

Linear sclerotic line through C1 left transverse process tip is of uncertain chronicity.

7 mm linear bony focus lateral to C6 is of uncertain chronicity. It appears corticated without an obvious donor site. Acute fracture through the right C6 transverse process anteriorly.

Minimally displaced fracture of right C7 transverse process.

Multilevel degenerative changes of the cervical spine elsewhere (more prominent at C5/C6 and atlantodental articulation) with no further acute fracture identified. No evidence of acute facet joint widening or subluxation, although note that disruption of the joints can be difficult to completely exclude on CT.

Right clavicle fracture.


  • Acute fracture of C2 as described which appears unstable involving the base of the dens, body and bilateral lateral masses. This extends to the right transverse foramen (subsequent CTA did not demonstrate a vascular injury).
  • Sclerotic line through C1 left transverse process tip is of uncertain chronicity; an acute component is difficult to exclude in this setting
  • Right C6 and C7 transverse processes fractures
  • Right clavicle fracture

Case Discussion

The odontoid process injury represents a type 3 Anderson and D'Alonzo fracture as it involves the lateral masses. Given the oblique orientation of the fracture with anterior translation of the peg, it constitutes a type 1 Roy-Camille fracture.

How to use cases

You can use Radiopaedia cases in a variety of ways to help you learn and teach.

Creating your own cases is easy.

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.