Abstract
BACKGROUND: While chronic low back pain (CLBP) is mechanistically linked to intervertebral disc degeneration (IDD) and multifidus muscle atrophy, the trajectory of these degenerative processes across aging populations remains poorly defined. Notably, sex-specific patterns and progression in elderly subgroups (≥ 80 years) require systematic characterization. Given the unclear age-related trajectory of these degenerative processes and the need for systematic clarification of sex-specific patterns and progression in elderly subgroups, this study aims to elucidate age- and sex-dependent relationships between disc degeneration and multifidus degeneration in a broad age spectrum of CLBP patients. METHODS: This retrospective cohort study analyzed indicators related to disc and multifidus degeneration in lumbar MRI data from 238 CLBP patients (20–99 years, 50.42% female). The cross-sectional area (CSA) of the multifidus muscle and fat infiltration ratio at the L3-L5 levels were quantified using semi-automated segmentation software (SlicerOmatic 5.0). Disc degeneration was assessed using the Griffith-modified Pfirrmann grading system. Age-stratified analyses included four subgroups: 20–39, 40–59, 60–79, and 80–99 years. Spearman correlation and ANOVA were applied to assess associations RESULTS: Pfirrmann grades negatively correlated with multifidus CSA (r=-0.208 to -0.28, P < 0.01) and positively with fat infiltration ratio (r = 0.396–0.478, P < 0.01). Age exacerbated both disc and multifidus degeneration (P < 0.01), with the 80–99 years group showing the highest fat infiltration ratio (35.56%-52.08%). Males had larger CSA but lower fat infiltration ratio than females (P < 0.01). CONCLUSION : Disc degeneration and multifidus atrophy are interdependent and influenced by aging and sex. Fat infiltration ratio may serve as a prognostic marker for personalized rehabilitation.