• Kaitlin Hintelmann, Biomedical Engineering, University of Delaware

• Dawn Elliott, Biomedical Engineering, University of Delaware

Lumbar Paraspinal Muscle Size and Fatty Infiltration in Chronic Low Back Pain Assessed with MRI

Kaitlin R.  Hintelmann, Mackenzie N. Conner, J. Megan Sions, Dawn M. Elliott

Introduction

Low back pain (LBP) is the leading cause of disability worldwide [1]. The multifidi (MF) and erector spinae (ES) are crucial for spine stability and movement [2]. Studies found associations between pain, smaller muscle size, and greater fatty infiltration [3,4,5]. Therefore, this study evaluated whether participants with chronic LBP have greater degeneration in the multifidi and erector spinae than controls and whether these differences vary by spinal level.

Methodology

Participants with chronic LBP (n=17) and controls (n=8) underwent 3T Dixon magnetic resonance imaging. The MF and ES were segmented from L1 to S1 using ITK-SNAP following Crawford+ 2017 [6]. Cross-sectional area (CSA) was calculated at the mid-disc level and volume was calculated from L1 to S1. Fat Signal Fraction(FSF) was calculated from water and fat images for CSA and volume [7].

Results

The ES CSA was significantly smaller in the pain group (p = 0.0209 , Δ= 119.7±118.9 mm²) but not the MF (p=0.1057, Δ= 36.003±41.467 mm²). Volume did not differ between groups in the muscles.

The FSF CSA was not significantly different between groups in the ES (p=0.1692) or the MF (p=0.0589), but the pain group had higher fatty infiltration in the ES (p = 0.004, x̄ = 24.870±15.346 %).On average, the FSF CSA was greater in the ES (24.3±15.5 %) than the MF (20.1±8.9 %). FSF Volume did not differ between groups in either of the muscles.

Conclusion

This study suggests chronic LBP is associated with reduced ES CSA, but not volume, implying regional muscle atrophy. Although no significant fatty infiltration differences were detected, the pain group demonstrated higher MF fatty infiltration. Larger studies are needed to determine whether level-specific muscle size and fatty infiltration are associated with LBP and may guide targeted assessment and treatment.

Bibliography

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