MRI correlation between paraspinal muscle Atrophy, Age, and degenerative lumbar spine changes in low back pain patients

Objectives: MRI-detected paraspinal muscle atrophy may influence operative planning by guiding the choice of approach, modifying decompression strategy and supporting the need for extended fusion. To assess the correlation between paraspinal muscle atrophy and degenerative spinal parameters—ligamentum flavum thickness, facet joint tropism, and Modic changes—using MRI in patients with mechanical low back pain. Methods: A total of 351 lumbar spine MRIs from patients aged more than 20 years who presented with mechanical low back pain were analysed. Measurements included cross-sectional area (CSA) of paraspinal muscles (multifidus and erector spinae), ligamentum flavum (LF) thickness, facet tropism, and Modic endplate changes at L2-L3 to L4–L5 levels. Statistical analysis was performed using the Pearson correlation and ANOVA tests. Intraclass correlation coefficient = 0.94 confirmed measurement reliability. Results: Paraspinal muscle CSA showed a significant inverse correlation with age (p < 0.01). Increased LF thickness and facet joint asymmetry were both associated with reduced muscle mass. Modic Type II changes were the most common and correlated with lower paraspinal CSA and greater LF thickness (p < 0.05). A positive correlation (p < 0.05) was found between LF thickness and facet tropism, suggesting concurrent degenerative progression. Conclusions: Paraspinal muscle atrophy shows a strong association with age-related degenerative spinal parameters, supporting its role as an early indicator of spinal degeneration. Integrating muscle evaluation into routine lumbar MRI may enhance diagnostic precision and aid in planning individualised, muscle-targeted interventions.