Lumbosacral transitional vertebrae in small-breed dogs: Prevalence, classification, and characteristics.

The lumbosacral transitional vertebra (LTV) is an abnormally formed vertebra that can be associated with cauda equina syndrome, lumbosacral (LS) degeneration, and pelvic rotation. However, there is little information on LTV in small-breed dogs, and no studies have investigated the association between LTV and LS diseases or degenerative changes in the coxofemoral joints. The purpose of this multicenter, retrospective, and cross-sectional study was to determine the prevalence of LTV in small-breed dogs (<10 kg), classify the type of LTV, and identify its association with degenerative changes in the LS and coxofemoral joints using CT images. Lumbosacral transitional vertebrae were divided into four types based on their morphological characteristics. Lumbosacral transitional vertebrae were detected in 127 of 812 dogs (15.6 %). The prevalence of LTV was higher in French bulldogs (33.3%), Schnauzers (33.3%), and Dachshunds (25%) than in other breeds. Type 2 was the most common, with morphological variations in the transverse processes, and 36.2% of the LTV group showed multiple types of LTV. Dogs with LTV tended to have LS spondylosis deformans (OR, 2.8) and pelvic rotation (OR, 6.4) compared with dogs without LTV. Type 4 LTV was significantly associated with pelvic rotation (p < 0.0001). This is the first study to investigate the prevalence, characteristics, and characteristics of LTV in small-breed dogs using CT images. The results of this study may contribute to a better understanding of this congenital anomaly in small-breed dogs. CT can evaluate LTV, which could predispose a dog to LS spondylosis deformans or pelvic rotation.