Dynamic magnetic resonance imaging of the lumbosacral spine in neutral and flexed position for presurgical assessment of clinically affected dogs with degenerative lumbosacral stenosis.

Objective: To compare diagnostic findings in neutral and flexed magnetic resonance imaging (MRI) of the lumbosacral joint (LSJ) performed for presurgical assessment in dogs with clinically suspected, diagnostically confirmed degenerative lumbosacral stenosis (DLSS), and to assess if these findings support the need for decompressive dorsal laminectomy/partial discectomy and/or foraminotomy in combination with distraction-stabilization techniques.

Study design: Retrospective, comparative study.

Animals: A total of 24 dogs with clinically suspected, MRI-confirmed DLSS that underwent dynamic LSJ imaging.

Methods: Medical records and MRI findings of included cases from three referral hospitals were reviewed. Quantitative and qualitative assessments of the LSJ (LSJ angle, protrusion ratios, degree of intervertebral disc [IVD] protrusion, ventral bulging of the ligamentum flavum [VBLF], foraminal compression) were compared in neutral and flexed positions. Their correlations with the degree of IVD degeneration or spondylosis was evaluated. Interindividual agreement was assessed among three observers.

Results: Degree of IVD protrusion, foraminal stenosis, VBLF, and protrusion ratios, were significantly reduced in flexion compared with neutral position (p < .001 for all comparisons). No dogs had persistent compression of the cauda equina or completely occluded foramina in flexion. The response of IVD protrusion to flexion was significantly directly correlated to the degree of IVD degeneration (p = .004), but not of spondylosis.

Conclusion: In flexed position, IVD protrusions, VBLF and foraminal stenoses improved in all cases, with resolution of all compression sites.

Clinical significance: With LSJ distraction-stabilization techniques, the need for concurrent decompressive dorsal laminectomy/partial discectomy or foraminotomy should be questioned, unless performed for IVD-spacer placement. Surgical case-control studies are required to investigate this further.