The Differences in Radiographic Vertebral Size in Dogs with Different Chest and Skull Types

Abstract

The objective of this study was to elucidate the differences in vertebral length, vertebral height, and vertebral length/height ratio of the fourth thoracic vertebra (T4), the second lumbar vertebra (L2), the fifth lumbar vertebra (L5) and the seventh lumbar vertebra (L7) based on radiographs in dogs with various body sizes, skull types, and thoracic conformations and to determine the relationships of these parameters with age and sex. A total of 258 dogs were included in this study and classified by three criteria-BW (Criterion 1), skull type (Criterion 2), and thoracic conformation (Criterion 3). Age had weak negative correlations with vertebral length and height. Sex did not affect the vertebral size parameters. BW had strong positive correlations with vertebral length and height, but there was no influence of BW on vertebral length/height ratio. Regarding the different body sizes and conformations, large breeds had vertebrae with significantly greater length and height than small and medium breeds (p < 0.001). In Criterion 2, the vertebrae of the mesocephalic dogs had significantly greater length and height than those of the brachycephalic and dolichocephalic dogs (p < 0.05). In Criterion 3, both deep-chest and round-chest dogs had vertebrae with significantly greater length and height than the barrel-chest dogs (p < 0.0001). Only vertebral length/height ratios of T4 were not influenced by age, sex, BW, skull type, and thoracic conformation. Age, differences in body size, skull type, and thoracic conformation could affect the vertebral size in dogs. Therefore, using breed-specific vertebral lengths and/or heights is a better approach for comparative radiographic analysis with vertebral measurements.

Keywords: canine; radiography; vertebral height; vertebral length; vertebral length to height ratio.

Figure 1

The vertebral length and height measurement methods on lateral radiographs. The vertebral length was measured from cranial ridge to caudal ridge of each vertebra (black line) and the vertebral height was measured from the narrowest part of each vertebra (red line). The vertebral length and height measurement of T4 (A). The vertebral length and height measurement of L2, L5 and L7 (B).

Figure 2

Comparing vertebral length/height ratios among size criteria (mean ± SD). (A) T4 length/height ratios, (B) L2 length/height ratios, (C) L5 length/height ratios and (D) L7 length/height ratios. Statistical differences among criteria were found using one-way ANOVA followed by Tukey’s test.

Figure 3

The vertebral length of mesocephalic dogs had significantly longer vertebrae of all four vertebrae than those of brachycephalic and dolichocephalic dogs (mean ± SD). (A) T4 length, (B) L2 length, (C) L5 length and (D) L7 length. Statistical differences among skull criteria were found using one-way ANOVA or the Kruskal–Wallis test followed by Tukey’s test.

Figure 4

The vertebral length of both deep-chest and round-chest group had significantly longer vertebrae of all four vertebrae than that of barrel-chest dogs (mean ± SD). (A) T4 length, (B) L2 length, (C) L5 length and (D) L7 length. Statistical differences among thoracic conformation criteria were found using one-way ANOVA or the Kruskal–Wallis test followed by Tukey’s test.

Figure 5

Correlations between the ages of all dogs and the vertebral length/height ratio. (A) T4 length/height ratio, (B) L2 length/height ratio, (C) L5 length/height ratio and (D) L7 length/height ratio. Correlations between parameters were made using Pearson’s correlation coefficient and Spearman’s correlation coefficient.