Abstract: Background: Degenerative lumbosacral stenosis (DLSS) shows poor correlation between imaging and clinical findings in dogs. Kinematic or dynamic imaging may improve elucidation of this relationship. Kinematic MR imaging has not been evaluated in dogs with DLSS. Objectives: Describe the morphologic features of the lumbosacral vertebral column of large-breed dogs with or without DLSS in neutral, flexed and extended MRI positions. Animals: 27 large-breed dogs: 15 DLSS-affected, and 12 clinically normal. Methods: Prospective blinded morphologic study. Patients underwent a 3.0 T MRI in lateral recumbency (mimicking natural standing position), followed by imaging in flexed and extended positions using a kinematic positioning device. Eight morphologic parameters were assessed in each position, including Pfirrmann grade of discs, direction and cause of compression, presence/severity of foraminal stenosis, and percentage reduction in vertebral canal height. Results: The lumbosacral angle was significantly different between the three positions (neutral, extension and flexion) in both groups (p< 0.05). In neutral position, 15 compressions (counting both ventral and dorsal) were identified at the L7-S1 region in DLSS dogs, with 9 in the normal group. In extension, there were 20 compressions in DLSS dogs, with 14 in the normal group. There were fewer compressions in flexion in both groups. There was a significant difference in vertebral canal height between neutral and extension (p< 0.05) and neutral and flexion (p< 0.05) in the DLSS group. Conclusions: Kinematic MRI is a feasible technique for evaluation of the lumbosacral region. It can exacerbate existing compressive lesions and reveal new compressions not identified with neutral positioning alone.
