Age and sex-based distribution of lumbar multifidus muscle atrophy and coexistence of disc hernia: an MRI study of 2028 patients.

PURPOSE We aimed to investigate the prevalence of lumbar multifidus muscle (LMM) atrophy in patients having mechanical low back pain with and without disc hernia. METHODS In total, 2028 lumbar magnetic resonance imaging scans of low back pain patients (age range, 18-88 years) were re-evaluated retrospectively. LMM atrophy was visually assessed in axial sections of L4-L5 and L5-S1 levels. RESULTS LMM atrophy prevalence at both levels was significantly higher in subjects ≥40 years compared with younger adults (P < 0.001). LMM atrophy was significantly more frequent in women than in men (P < 0.001). Among patients with low back pain without hernia, LMM atrophy was significantly more frequent than normal muscle (n=559 vs. n=392; P < 0.001). Frequency of LMM atrophy in low back pain patients without disc hernia was 13%. Hernia was more frequent in patients with LMM atrophy compared with patients without atrophy (P < 0.001). CONCLUSION LMM atrophy is more common in women; its prevalence and severity are observed to increase with advancing age, and disc hernia is found more frequently in individuals with LMM atrophy.