There were statistically significant differences in the basion cartilaginous dens interval values among the 3 groups. Radiograph using the basion axial interval.
It is the distance from the most inferior portion of the basion to the closest point of the superior aspect of the dens in the median midsagittal plane.
Basion dens interval pediatric. An abnormal distance between the dens or posterior axial line and the basion suggests failure or insufficiency of the alar ligaments tectorial membrane or both. Harris et al 2 calculated that 95 of adults in their study population had a bdi and bai less than 12 mm and considered this value as the upper limit of normal. Each patient underwent measurement of the occipital condyle c1 interval cci pb c2 atlantodental interval adi basion dens interval bdi basion opisthion diameter bod basion axial interval bai dens angulation and canal diameter at c1.
Mean values were calculated in each group. Several other authors have used the basion dens interval as published in the keats and sistrom atlas of radiologic measurement 10 to assess for atlantooccipital dissocia tion. All the children in their study population had a basion axial interval between 0 and 12 mm.
The basion dens interval bdi is the distance between the basion and the tip of the dens used in the diagnosis of atlanto occipital dissociation injuries. The method used by this group included the basion dens interval bdi originally described by wholey et al 4 as well as the basion axial interval bai. Normal pediatric craniocervical measurements.
7 3 0 1 7 5. Ct cervical spine midsagittal of normal patient illustrates the basion dens interval bdi anterior atlanto dental interval aadi posterior atlanto dental interval padi and basion atlanto interval bai which is measured in between the basion to the posterior axial line which is a line tangential to the posterior surface of c2. Mean sd mm mdct normal value mm basion dens interval.
One method involves the use of the basion dens interval which is measured from the tip of the dens to the basion the inferior margin of the clivus. The upper limits of the basion cartilaginous dens interval for the 3 groups were 5 34 mm in group a 5 64 mm in group b and 7 24 mm in group c. In 95 of adults the basion dens interval was less than 12 mm and in 98 the basion was situated no more than 12 mm anterior or 4 mm posterior to the posterior axial line fig 2.
The commonly accepted normative upper limit of the basion dens interval in children 12 12 5 mm 25 26 was found to be excessive as the maximum distance recorded in the study population. This interval can be measured on conventional film or ct images and a normal measurement is less than 12 mm but greater than 0 mm fig 11 32.