Variations in the median sacral crest and angulation of the first sacral spinous process associated with sacrocaudal fusion in greyhounds

The current study aimed to investigate the association between the morphology of the median sacral crest, variation in the angle of the spinous process of the first sacral vertebra, and the occurrence of sacrocaudal fusion in greyhounds. In this study, 167 sacra from cadavers of greyhounds (previously euthanized for reasons unrelated to this study) were collected, classified into standard and fuses sacra (based on the number of fused vertebrae and type of fusion), and then classified based on the morphology of the median sacral crest into three different types: type F (full crest), type N (when the median sacral crest is incomplete, and type R (when the median sacral crest is present but it was short or reduced). Among the 167 sacra, 91 sacra were used to measure the angle of the spinous process of the first sacral vertebrae (1st SPA). Each of the sacra was digitally photographed using a Nikon D3100 digital camera (Tokyo, Japan) in which the camera was positioned laterally with the lens parallel to the central part of the lateral aspect of the sacrum and on a flat surface of the laboratory bench. Image-Pro Express Version 5.0 imaging software (Media Cybernetics, Silver Spring, Maryland) was used to draw and measure the angles. The angle of the 1st SPA was defined as the angle formed dorsally at the intersection of two lines. The first line was drawn to represent the cranial ridge of the spinous process of the 1st SPA, and the second line was drawn across the most dorsal surface points of the spinous processes of the 1st (S1) and 3rd (S3) sacral vertebrae. Significant (p < 0.001) morphological differences (F, R, N) were found in the median sacral crest, and the prevalence of median sacral crest type R in standard sacra was 35.1% compared to 10% in fused sacra, type F was 41.2% in standard sacra and 10% in fused sacra, and type N was 23.7% in standard sacra and 80% in fused sacra. The angle 1st SPA with median sacral type N was statistically significantly less (more upright) than those in sacra with median sacral type F (P < 0.042). Differences have been found in the median sacral crest and angulation of the spinous process of S1 vertebra in sacra with different types of median sacral crest.