Post-Mortem Computed Tomographic Features of the Most Caudal Lumbar Vertebrae, Anatomical Variations and Acquired Osseous Pathological Changes, in a Mixed Population of Horses

SIMPLE SUMMARY: Conventional diagnostic techniques cannot always provide a diagnosis for horses with back pain. A better visualization of the vertebral morphologic details can be achieved by using advanced diagnostic imaging tools. For this reason, this study presented a detailed post-mortem computed tomographic description of the anatomical variations and acquired osseous pathological changes in the equine caudal lumbar region that have never been reported. The authors hypothesized that body weight, age, previous use, and some anatomical variations might be correlated with the presence and severity of the lesions. The results partially supported the initial hypotheses because the concomitant presence of anatomical variations and acquired osseous pathological changes at the same level, and the correlation between age and the presence of some degenerative pathologies were observed. Furthermore, this study provided additional tomographic information on bone features in both pathological and non-pathological specimens. However, other future studies are needed to correlate the clinical significance of the anatomical variations and acquired osseous pathologies of the equine lumbar vertebrae. ABSTRACT: The radiographic, ultrasonographic, and scintigraphic findings of horses with thoracolumbosacral pain have been previously reported. In this study, the computed tomographic appearance of anatomical variations and pathological changes of the equine caudal lumbar region through a post-mortem examination were investigated. A total of 40 horses that had died or were submitted for euthanasia, for reasons unrelated to the study, were included in the study. From all the specimens, the modified vertebral system was adopted to evaluate and describe the four most caudal lumbar vertebrae, which were numbered from a caudal reference point (lumbosacral junction), with the segment number designated within parentheses (i.e., L(i)-L(iv)). Contact of the spinous processes was detected in 21 specimens (54%) and fusion in 6 specimens (15%). Lumbar spondylosis was seen in 17 specimens (42.5%), more commonly on the lateral aspect or on both ventral and lateral aspects in 12 specimens (71%). The presence of spondylosis was found more commonly in older horses (p < 0.001). There was no difference in bony density in specimens with spondylosis or spinous processes contact compared to specimens without. The highest prevalence of bony changes was found at L(ii)-L(i) intertransverse joints in 28 specimens (97%) on the left and in 22 specimens (96%) on the right side. Spondylolisthesis and partial fusion of the L(ii)-L(i) vertebral disc were found in association with degenerative pathologies. This study showed a high frequency of several anatomical variations and acquired osseous pathological changes in the most caudal lumbar vertebrae via a CT examination.