COMPUTED-TOMOGRAPHY OF THE NORMAL CANINE LUMBOSACRAL SPINE - A MORPHOLOGIC PERSPECTIVE

The lumbosacral spine of six normal dogs weighing 4.5 to 24.5 kg was i maged by computed tomography in 5.0 mm & 10.0 mm transverse planes, Th e vertebral canal and thecal sac (including emerging nerve roots not d istinguished as separate structures from the spinal cord) were measure d along dorsoventral and transverse dimensions at cranial, middle and caudal levels within each vertebra from transverse tomographic images, Linear measurements were standardized to the dorsoventral dimension o f the L(6) vertebral midbody to permit comparison and averaging of the vertebral and thecal sac dimensions among different sized dogs, The d orsoventral and transverse vertebral canal size progressively increase d from cranial to caudal within each vertebra from L(1)-L(6) (p less t han or equal to 0.05). The transverse dimension of the thecal sac imag e increased caudally within each vertebra from L(1)-L(4) (p less than or equal to 0.05), The vertebral canal dorsoventrat and transverse dim ensions were largest in the midlumbar area (p less than or equal to 0. 05), The transverse, but not the dorsoventral, imaged dimension of the thecal sac peaked in the L(4) vertebra (p less than or equal to 0.05) , The dorsoventral thecal sac image was observed to fill the vertebral canal in the cranial and middle vertebral Levels in vertebrae L(1) th rough L(5) in over 60% of these normal dogs. However, epidural fat cou ld almost always be seen lateral to the thecal sac regardless of what lumbar vertebra or vertebral level was imaged, Cranial to the lumbosac ral junction, the dorsal intervertebral disk margin was almost always concave relative to the thecal sac, However, at the L(7)-S-1 junction, some dogs had flat or even slightly convex dorsal intervertebral disk margins, The dorsal and ventral longitudinal ligaments and the ligame ntum flavum could not be identified as distinct structures on the 5.0 mm transverse tomographic images.