Microcomputed tomography examination of the cortical and trabecular structures of the cranial cervical spine in dogs and cats.

INTRODUCTION: The microarchitectural structure of the cervical spine in small animals, particularly the cranial cervical spine, has received little attention to date. This study aimed to analyze the trabecular and cortical microarchitecture of the first four cervical vertebrae and to identify potential differences between toy- and small-breed dogs and between toy-breed dogs and cats. METHODS: The first four cervical vertebrae from 20 euthanized dogs (10 toy-breed dogs and 10 small-breed dogs) and 20 euthanized cats were examined using micro-computed tomography. The following parameters were analyzed: bone volume fraction (BV/TV), bone surface-to-volume ratio (BS/BV), connectivity density (Conn. D), trabecular number (Tb. N), trabecular thickness (Tb. Th), trabecular separation (Tb. Sp), degree of anisotropy (DA), cortical bone density (mean density), and the dens-to-axis length ratio (DALR). RESULTS: Trabecular microarchitecture was largely comparable between toy-breed dogs and small-breed dogs; however, cortical bone density was significantly higher in toy-breed dogs than in small-breed dogs. Compared with toy-breed dogs and cats, cats more frequently exhibited a larger BS/BV, a higher DA, and a larger Tb. Sp. In contrast, toy-breed dogs exhibited higher BV/TV, a higher Conn. D, Tb. Th, Tb. N, and mean density. The DALR did not differ significantly among the groups. DISCUSSION: These findings suggest greater overall stability of the cervical spine in toy-breed dogs compared to cats. Furthermore, these microarchitectural differences may provide useful criteria for selecting appropriate surgical interventions for affected animals.