A normal adult Atlanto-Dental-Interspace (ADI) is ≤ 3mm. A normal child ADI can range from 1-5mm, (figure 1).
What Is The Most Common Cause For ADI Disruption?
Trauma - This is by far the most common. An accident or injury has occurred that has torn the Transverese Atlantal Ligament (TAL). (figure 2)
How Is The ADI Measured?
Typically the Atlanto-Dental-Interspace is measured on a neutral lateral cervical x-ray from the bottom of the anterior tubercle to the anterior surface of the odontoid process of (C2). (figure 3).
How Is The ADI Tested For Stability?
Typically flexion-extension x-rays are taken with the patient tipping their head forward and back to determine ligament stability or laxity of the Atlanto-Dental-Interspace.