Computertomographic examinations of the canine lumbosacral spine

The objectives of this study were: 1) documentation of cross-sectional anatomy of the lumbosacral area, 2) to obtain and describe abnormalities and finally 3)to develop a CT technique for the diagnosis of a L7/S1 spondylolisthesis. In a 3 year retrospective study 61 large breed dogs with history of suspected cauda equina-syndrome were examined using flexion-extension radiography and flexion-extension computed tomography. 25 out of 60 dogs were German shepherd dogs, 3 shepherd-cross, 7 mongrels, 4 Rottweilers and 22 other breeds. 27 dogs of the flexion/extension group were also morphometrically examined. CT studies regarding morphology of the lumbosacral joint showed differences between flexed and extended position: The intervertebral foramina enlarged in flexed position, the intervertebral disc, segmental spinal nerves and contrast enhanced blood vessels were more easily to evaluate. In flexion the lumbosacral foramen was 'open' in all cases, while it was 'closed' in most of the extension slices. The cranial articular processes of the sacrum appeared earlier in extension, they seemed to 'slip' beneath the caudal articular processes of the last lumbar vertebra, the articular surfaces got incongruent, and therefore the intervertebral foramina were narrowed. The most common pathologic findings were disk protrusion (28 dogs) and spondylosis (24 dogs). Rare diagnoses were neoplasia (1 case), transitional vertebra (1 case), shortened L7 (2 cases) and osteochondrosis dissecans of the L7 or sacral endplate (5 cases). Morphometrical examinations showed that the intervertebral foramina enlarged in flexed positions, not only in length (craniocaudal dimension) but also in their dorsoventral diameter. There was no difference in the dorsoventral diameter of the spinal canal between flexion and extension CT. This study showed that computed tomography is superior to common ways of imaging of the lumbosacral spine like radiography or myelography. It was possible to identify pathologic changes as morphologic and morphometric differences between flexed and extended positions. A technique for diagnosis of lumbosacral spondylolisthesis could not be obtained. (author)