Comparison of Cervical Spine Anatomy in Calves, Pigs and Humans

Background Context Animals are commonly used to model the human spine for in vitro and in vivo experiments. Many studies have investigated similarities and differences between animals and humans in the lumbar and thoracic vertebrae. However, a quantitative anatomic comparison of calf, pig, and human cervical spines has not been reported. Purpose To compare fundamental structural similarities and differences in vertebral bodies from the cervical spines of commonly used experimental animal models and humans. Study Design Anatomical morphometric analysis was performed on cervical vertebra specimens harvested from humans and two common large animals (i.e., calves and pigs). Methods Multiple morphometric parameters were directly measured from cervical spine specimens of twelve pigs, twelve calves and twelve human adult cadavers. The following anatomical parameters were measured: vertebral body width (VBW), vertebral body depth (VBD), vertebral body height (VBH), spinal canal width (SCW), spinal canal depth (SCD), pedicle width (PW), pedicle depth (PD), pedicle inclination (PI), dens width (DW), dens depth (DD), total vertebral width (TVW), and total vertebral depth (TVD). Results The atlantoaxial (C1–2) joint in pigs is similar to that in humans and could serve as a human substitute. The pig cervical spine is highly similar to the human cervical spine, except for two large transverse processes in the anterior regions ofC4–C6. The width and depth of the calf odontoid process were larger than those in humans. VBW and VBD of calf cervical vertebrae were larger than those in humans, but the spinal canal was smaller. Calf C7 was relatively similar to human C7, thus, it may be a good substitute. Conclusion Pig cervical vertebrae were more suitable human substitutions than calf cervical vertebrae, especially with respect to C1, C2, and C7. The biomechanical properties of nerve vascular anatomy and various segment functions in pig and calf cervical vertebrae must be considered when selecting an animal model for research on the spine.