The gross and radiographic appearance of sacroiliac ankylosis capsularis ossea in the dog.

This study was carried out to determine the incidence and to describe the radiographic appearance of ankylosis capsularis ossea at the canine sacroiliac joint, as well as to determine factors, which might cause radiographic misinterpretation of this finding. Bone specimens of 646 pelves of pure-bred dogs were assessed for morphological evidence of ankylosis capsularis ossea. The lesion was most commonly present at the cranioventral aspects of the sacroiliac joint. More than 50% of adult dogs had signs of being at least mildly affected. Among these, large and giant breeds were most commonly involved. Unlike moderate and severe degrees of this disease, smaller osteophytes had not been visualised on radiographs. For radiographic diagnosis, angled views of the sacrum are recommended. In central views of the sacrum, the presence of increased sacral concavity consistent with increased ilial convexity of the caudal aspect of the sacroiliac contact area might simulate the presence of ankylosis capsularis ossea. The clinical importance of the present findings is discussed in context with human literature.

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.