Special Poster Session 51st International Society for the Study of the Lumbar Spine Annual Meeting 2025

Introduction: Recent studies highlight the paraspinal muscles (PM) as essential for spinal health, with PM atrophy linked to degenerative spine conditions, chronic back pain, and poor surgical outcomes. However, assessments of spinal sarcopenia are often limited to fatty infiltration (FI) and functional cross-sectional area (fCSA), neglecting lean muscle quality. Elevated muscle T2 on MRI is a proposed marker for muscle aging due to its association with age and reduced muscle function. We propose a novel paraspinal muscle quality (PMQ) score, which normalizes T2 intensity of lean muscle to cerebrospinal fluid (CSF) intensity, aiming to establish its relationship with demographics, muscle atrophy markers, and low back pain.

Methods: Patients who underwent lumbar spinal surgery for degenerative lumbar pathologies from December 2014 to July 2023 were analyzed. Data collected included age, sex, BMI, smoking status, hypertension, diabetes, ASA score, vertebral bone mineral density (BMD), and low back pain as assessed by the Oswestry Disability Index (ODI) and its subsections. Erector spinae and multifidus muscles were segmented at the L4 upper endplate on axial T2-weighted MRI (Figure 1). Fat and muscle areas were determined using automated signal intensity thresholding, with fCSA defined as lean muscle area normalized to height squared. FI was calculated as fat area divided by total muscle area. A region of interest (ROI) was set at the same axial level in the cerebrospinal fluid (CSF) or the closest level if stenosis was present. The PMQ score was the ratio of lean muscle intensity to CSF intensity, ranging from 0 to 1. Right and left measurements were averaged. Interrater agreement for PMQ in 46 randomly selected patients was assessed using ICC. Spearman’s correlation was used to analyze parameter relationships. Proportional odds models with ordinary outcomes were used to assess the relationship between multifidus PMQ and the ODI-subsection pain intensity, adjusting for age, sex, BMI, and FI.

Results: A total of 481 patients (53.4% female) with a median age of 66 years (IQR: 58 - 72) were included. PMQ had a highly significant positive correlation (p < 0.01) with age, female sex, BMI, ASA score, and hypertension. A highly significant negative correlation was observed with vertebral BMD. Both erector spinae and multifidus PMQ had a significant positive correlation with corresponding muscle FI with a rho of 0.50 and 0.52, respectively (p < 0.001), and a significant negative correlation with muscle fCSA with a rho of -0.10 (p = 0.037) and -0.12 (p = 0.006), respectively. Multifidus PMQ significantly predicted pain intensity with an odds ratio of 4.39 (95% CI: 1.13 – 17.08, p = 0.033). The interrater reliability for PMQ was high for both muscle groups, with an ICC estimate of 0.867 (95% CI: 0.720 to 0.932) for erector spinae and 0.874 (95% CI: 0.767 to 0.931) for multifidus.

Conclusion: The novel PMQ score correlates with age, female sex, BMI, comorbidities, and predicts low back pain. As a potential indicator of muscle aging, this parameter can be integrated into paraspinal muscle assessment and implemented in future research in addition to conventional parameters.