Objective: The purpose of our study was to establish normal values on MDCT images for the measurement of various craniocervical junction relationships in children and to address discrepancies in the literature based on radiographic values.
Materials and methods: Accepted methods of evaluating the craniocervical junction were used to calculate normal values in 117 normal children on MDCT images with multiplanar reconstructions. The basion-axial interval, basion-dens interval, Powers ratio, atlantodental interval, and atlantooccipital interval were measured in each patient and compared with accepted data based on radiographs.
Results: The basion-axial interval was difficult to reproduce on MDCT images. In 97.5% of patients, the basion-dens interval was less than 10.5 mm compared with 12 mm based on data from radiographs. Separating the patient population into those in whom the os terminale was ossified and those in whom it was not revealed a difference of 2 mm in the upper limit of normal (9.5 and 11.6 mm, respectively). The Powers ratio showed no significant difference compared with data obtained using radiographs. In 97.5% of the population, the atlantodental interval was less than 2.6 mm, compared with 4-5 mm measured on radiographs. The atlantooccipital interval showed 97.5% of the population falling below 2.5 mm at any point in the joint space, compared with the previously accepted value of 5 mm.
Conclusion: Normal values for the craniocervical junction articulations and relationships as seen on MDCT are different from the accepted ranges of normal based on radiographs. The values should be considered the normal values in the pediatric population on MDCT.