Intra- and inter-rater reliability of the anterior atlantodental interval measurement from conventional lateral view flexion/extension radiographs

Flexion and extension lateral radiographs of individuals investigated for atlantoaxial instability were measured for AADI on three occasions. Intra-rater intraclass correlation coefficients (ICC) were calculated for both flexion (0.99) and extension (0.96). Inter-rater ICCs were 0.93 and 0.84 for flexion and extension, respectively. The AADI measurement proved to be reproducible with a minimal standard of error, between and within raters.