Association between the morphology of certain bones in the hind limbs and the variation in the morphology of the sacrum in greyhounds

OBJECTIVE: To identify associations between the occurrence of sacrocaudal fusion and the potential morphology of certain hind limb bones in actively racing greyhounds.

METHODS: The calcaneus, talus and patella from each hind limb were collected from 94 male and 77 female mature greyhound cadavers and grouped into four groups; right or left bones from greyhounds with a standard or fused sacrum. The measurements were recorded for the following parameters: body mass of the greyhound, mass, length, and width of the right and left calcanei, tali and patellae.

RESULTS: A fused sacrum (4 sacral vertebrae) was present in 41% of specimens. The right and left calcanei, tali and patellae in greyhounds with a standard or fused sacrum were anatomically similar. Overall, left to right asymmetry was found, in the width of calcaneus (P < 0.01) and the talus (P < 0.05) and the length of calcaneus (P < 0.001) all these being larger in bones from the left hind limbs. Comparing bones from dogs with a fused or unfused sacrum showed that the right calcaneus length (P < 0.05) was significantly less than the left in those greyhounds with standard sacrum; the right calcaneus width was significantly less (P < 0.01) than the left in those with a fused sacrum. There were no significant differences in the means of measurements of bones between greyhounds with a standard and those with a fused sacrum except for the mass of the right (95% CI 0.22 to 1.10, P < 0.01) and left (95% CI 0.18 to 1.04, P < 0.01) calcaneus which were heavier in greyhounds with a fused sacrum than those with a standard sacrum.

CONCLUSION: In a population of greyhounds that race on anticlockwise tracks, the left calcaneus was wider and longer than the right and the left talus was wider. This asymmetry was more significant in dogs with sacrocaudal fusion and those dogs had more massive calcanei than dogs with standard sacrums, suggesting a difference in the way these bones were loaded in dogs with sacrocaudal fusion compared to dogs with the standard sacral anatomy.