Thirty healthy dogs had their cervical spines radiographed, and the dorsal atlantoaxial distance and others vertebral anatomical parameters were measured. These data were assessed using the Pearson correlation coefficient. After detection of the best correlation parameter, we used the dimensional correlation coefficient of formula (CCD). In the second stage of the study, radiographs of the 33 dogs with atlantoaxial subluxation (SAA) were used. In each radiographic image, the CCD formula was applied. All normal and subluxation radiographic images were randomized, and submitted to subjective analysis. It was observed that the anatomical parameter with the highest correlation is the length of the spinous process of the axis, obtaining a mean value of 0.056 index and 0.019 standard deviation. Index mean value obtained in dogs with the disease of 0.287 and standard deviation of 0.123. The subjective analysis revealed 88.89% to 95.24% agreement, while the result obtained by the CCD formula was shown to be 100% effective in the diagnosis of SAA. We suggest the use of the CCD formula to obtain the index of normality of the atlantoaxial distance with a mean value of 0.056 and maximum of 0.098, and it is concluded that the index is highly effective in the diagnosis of subluxation between the atlas and the axis.
atlas; axis; instability; neurology; subluxation