A Comprehensive Analysis Between Disk Geometry and Posterior Muscle Characteristics Among Degenerative Spine Patients: An Internal Retrospective Review.

Study Design: A retrospective Cohort Study.

Objective: The aim of this study is to investigate the associations between posterior muscle health characteristics and disk geometry parameters between L1 and S1.

Summary Of Background Data: Paralumbar muscle changes have been associated with clinical outcomes. However, the relationship between disk geometry and paralumbar muscle changes has not been defined.

Methods: Axial T2 MRI was analyzed for paralumbar muscle measurements, and lateral radiographs were analyzed for disk geometry parameters in patients with disk degeneration. Associations between disk shape and muscle health at each individual lumbar level were evaluated using a partial correlation controlling for age and sex. Demographic data were compared between the listhesis groups, and an ANCOVA analysis controlling for significant demographic parameters was conducted to evaluate differences in muscle characteristics.

Results: In all, 435 patients were included (age: 55.6±15, BMI: 29.5±6, 60.9% female, 41.3% White). Muscle health median characteristics were CSA/BMI=140, LIV=13, and Goutallier Classification of 1. Partial correlations between focal disk parameters and muscle health controlling for age and sex showed moderate significant positive associations between focal lordosis and lumbar indentation value (LIV) at every level L1-S1 (mean r=0.264 between L1 and L5, P<0.001), weak positive association between focal lordosis and CSA/BMI (mean r=0.113 at L2-L5, P <0.03), and weak negative associations between disk height and Goutallier Classification (mean r=0.158 at L1-L5, P<0.03). Listhesis at L4-S1 was stratified, and ANCOVA controlling for sex and age demonstrated no significant association between S and R groups and CSA/BMI, LIV, or Goutallier classification (P>0.1).

Conclusions: Posterior muscle health was significantly associated with disk shape, especially disk height and disk lordosis, with larger and more lordotic disks being associated with better muscle health. Disk listhesis was not significantly associated with muscle quality when controlling for demographic characteristics, and no differences in muscle health parameters were observed in patients with spondylolisthesis versus retrolisthesis. Overall, the results highlight important associations between lumbar compensation, disk geometry, and posterior muscle health.