Defining Normative Mixed-Breed Ovine Spine Anatomy Using Computed Tomography and Magnetic Resonance Imaging

The availability of suitable preclinical models is critical for developing novel therapeutic interventions. Ovine models are particularly useful for studying spinal diseases due to their similarity in size and weight to humans. However, evaluation of the ovine spinal cord and canal anatomy is necessary for such translational application. To date, no studies have quantified the entire ovine spine using advanced imaging. In this work, we used MR and CT imaging to obtain the quantitative anatomic information necessary for the appropriate preclinical investigations of the spinal cord and spine using sheep. Six mixed-breed, female sheep were scanned in dorsal recumbency for MR T1- and T2-weighted images, as well as sternal and dorsal recumbency for CT images. Interactive multiplanar reformation and a series of automatic measurements, followed by computation of various distances within the spinal cord and canal, were completed for each animal. This led to the quantification of the MR-derived images: spinal cord and canal width and height, cord circumference, dorsal CSF distance, and ventral-dorsal/left-right vertebral displacements. The CT-derived, computed measurements were for aminal circumference, vertebral height, and disk height index. CT and MR imaging were performed on all animals, although some measurements were excluded due to image quality. Spinal cord circumference peaked at C6 (27.41 mm) and L6 (24.93 mm), with notable ventral-dorsal displacement at L7 (2.65 mm). Neural foramina circumference showed bimodal peaks at C8 and L7, while vertebral height declined from L7 to T9, peaking at C4 (40.42 mm), highlighting structural variability along the spine. This study will be beneficial in the modeling and development of precision neurosurgical treatments by providing a comprehensive quantitative dataset for veterinary research on spinal disease and the development of therapeutic interventions.