Introduction

Degenerative lumbosacral stenosis (DLSS) in dogs has similar manifestations of pain and neurological dysfunction to chronic low back pain in people, which is also characterized by lumbar paraspinal atrophy and asymmetry.

Objectives/Aims

The purpose of this study was to investigate whether dogs with DLSS have lower paraspinal mass and symmetry compared to control dogs.

Methods

Transverse T2-weighted magnetic resonance images were evaluated for nine dogs with and nine dogs without DLSS. Mean cross-sectional area was measured for the lumbar multifidus and longissimus lumborum muscles bilaterally and the L7 vertebral body at the level of the caudal endplate (see Figure 1). Asymmetry indices and cross-sectional areas relative to L7 were compared between study populations for both muscle groups using the Student's t-test.

Figure 1. T2-weighted sagittal and transverse images demonstrating localizer at the L7 caudal endplate and cross-sectional area measurement technique, respectively

Results

Mean muscle-to-L7 cross-sectional area ratios were significantly smaller in the DLSS group for both lumbar multifidus (p = 0.026) and longissimus lumborum (p = 0.011). Mean right-to-left lumbar multifidus and longissimus lumborum asymmetry indices were, respectively, 53% and 77% higher for the group with DLSS than for the control group, but the differences were not significant (see Figure 2).

Figure 2. Paraspinal muscle to L7 endplate cross-sectional area ratios and asymmetry indices for lumbar multifidus (red) and longissimus lumborum (blue)

Conclusions

This study demonstrated altered lumbar paraspinal muscle size and symmetry in dogs with lumbosacral stenosis. Based on these results, a study is currently underway to evaluate whether a co-restabilization exercise program can increase paraspinal muscle size and symmetry, as well as improve pain and function in dogs with DLSS that are mildly affected or are poor surgical candidates.