Atlantodental interval

The atlantodental interval (ADI), as the name suggests, is the horizontal distance between the anterior arch of the atlas and the dens of the axis, used in the diagnosis of atlanto-occipital dissociation injuries and injuries of the atlas and axis.

It is the distance (in mm) between the posterior cortex of the anterior arch of the atlas and the anterior cortex of the dens in the median (midsagittal) plane.

Normal values are:

  • radiographs
    • adults
      • males: <3 mm
      • females: <2.5 mm 1 (although most authors describe <3 mm)
    • children: <5 mm
  • CT: adults: <2 mm 1

Related articles


Share article

Article information

rID: 40483
Synonyms or Alternate Spellings:
  • ADI
  • Atlantodental interval (ADI)
  • Atlanto-dental interval (ADI)

Support Radiopaedia and see fewer ads

Cases and figures

  • Base of skull lines (annotated images)
    Drag here to reorder.
  • Updating… Please wait.

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

     Thank you for updating your details.