Atlantodental interval

The atlantodental interval (ADI) 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

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Article information

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

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Cases and figures

  • Base of skull lines (annotated images)
    Drag here to reorder.
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