Analysis of the Association Between Lumbar Paraspinal Muscle Atrophy, Facet Joint Degeneration, and Degenerative Lumbar Scoliosis

Objective To analyze the correlation between paraspinal muscle atrophy, facet joint degeneration, and degenerative scoliosis (DS). Methods A retrospective study included 231 chronic low back pain patients from Zhongda Hospital Affiliated to Southeast University (January 2023-January 2024). Radiographic diagnosis assigned 150 patients to DS group (subclassified into mild [n = 72], moderate [n = 56], severe [n = 22]) and 81 to non-DS control group. Using T2-weighted MRI at L3-S1 levels, ImageJ software measured multifidus (MF) and erector spinae (ES) cross-sectional area (CSA) and functional muscle ratio (LCSA/GCSA). Surgimap software quantified facet joint angle (FJA), facet overhang (FO) length, and facet joint space width (FJSW). Logistic regression analyzed risk factors with ROC curves determining diagnostic thresholds. Results Non-DS controls had higher male proportion and bone mineral density (BMD) than DS patients(P < 0.05). Severe DS patients were older with lower BMD versus mild/moderate subgroups (P < 0.05).Non-DS controls exhibited larger MF CSA (L3/4-L5/S1), ES CSA(L3/4, L5/S1), MF + ES CSA (L3/4-L5/S1), LCSA/GCSA (L3/4-L5/S1) and FJSW (L3/4-L4/5), but smaller FJA (L3/4-L5/S1) and FO length (L4/5-L5/S1) than DS patients (P < 0.05). Significant concave-convex differences were observed across L3-4 to L5-S1: for mild DS patients in LCSA/GCSA, MF CSA, ES CSA, FJA, FO length, FJSW; for moderate DS in LCSA/GCSA, FJA, FO length, FJSW; for severe DS in FJA, FO length(P < 0.05). Mild vs Severe and Moderate vs Severe differed significantly in total MF + ES CSA, total MF CSA, convex/concave MF CSA, total ES CSA, convex/concave ES CSA, average LCSA/GCSA, convex/concave LCSA/GCSA across all levels (P < 0.05). Mild vs Severe differed in concave/convex FJA, FO length, FJSW at L3-4 & L4-5 (P < 0.05). Mild vs Moderate differed in total MF CSA, convex MF CSA, convex/concave FJA, convex FO length at L3-4, and convex LCSA/GCSA at L5-S1 (P < 0.05). Cobb angle correlated negatively with MF CSA, ES CSA, LCSA/GCSA, FJSW, and positively with FJA, FO length in moderate/severe DS patients(P < 0.05). MF CSA ,MF LCSA/GCSA and ES LCSA/GCSA correlated negatively with FJA and FO length at all levels in both groups (P < 0.05). No correlations existed between ES CSA, MF CSA, LCSA/GCSA and FJSW (P > 0.05). Multivariate analysis identified higher BMD (OR = 0.802, P = 0.032), greater LCSA/GCSA (OR = 0.005, P = 0.003), larger MF CSA (OR = 0.969, P = 0.027), and larger ES CSA (OR = 0.973, P = 0.014) were protective factors against DS, while larger FJA (OR = 1.075, P = 0.016) and greater FO Length (OR = 1.067, P = 0.001) were independent risk factors. ROC analysis yielded AUCs/cut-offs: BMD (0.581/-0.900T-score), LCSA/GCSA (0.717/0.805), MF CSA (0.608/635mm²), ES CSA (0.463/832mm²), FJA (0.627/57°), FO length (0.651/6.550mm). Conclusion DS patients demonstrate progressive paraspinal muscle atrophy, sagittal-oriented facet joints, and advanced facet degeneration correlating with scoliosis severity. Elevated FJA and FO length associate with aggravated muscle atrophy. Diagnostic thresholds indicating DS probability are BMD < − 0.900T-score, LCSA/GCSA < 0.805, MF CSA < 635 mm², ES CSA < 832 mm², FJA > 57°, and FO length > 6.550 mm.