Differentiation between lumbosacral transitional vertebrae, pseudolumbarisation, and lumbosacral osteophyte formation in ventrodorsal radiographs of the canine pelvis.

Ventrodorsal radiographs of the pelvis (n=150) of Rottweilers, Golden Retrievers, and German Shepherd dogs and macerated spines (n=800) from a variety of breeds were assessed for morphological evidence of lumbosacral transitional vertebrae as well as for factors that might lead to radiographic misinterpretation of this condition. Those alterations closely resembling the radiographic appearance of transitional vertebrae were identified to be: (1) calcification of the dorsal and ventral sacroiliac ligaments (=pseudolumbarisation), which might be interpreted as a costal process at S1 (or the corresponding vertebra in cases of numerical vertebral variations); and (2) osteophyte formation at the lumbosacral junction simulating separation of the cranial articular processes from the assembly of the sacral wing as seen in transitional vertebrae.