Association of the Cross-Sectional Area, Muscularity, and Muscle-Fat Ratio of the Paraspinal Muscles with Chronic Low Back Pain

Background: It is now a well-established fact that paraspinal muscle integrity plays a critical role in low back pain. We aimed to determine the association of the cross-sectional area (CSA), muscle disc ratio (muscularity), and muscle-fat ratio of the paraspinal muscles with chronic low back pain (CLBP) of varied pathologies and the effect of ageing and body mass index (BMI). Methods: Fifty patients with CLBP (Group A) and 25 healthy controls (Group B) were enrolled. The Group A was further subgrouped into lumbar spondylosis, mechanical back pain, and lumbar disc herniation. All participants were subjected to magnetic resonance imaging of lumbar spine. Results: The CSAs of the muscles did not differ significantly between the two groups except for multifidus (P < 0.05) and psoas (P < 0.001) at L1-L2 and psoas (P < 0.001) at L2-L3. There was a significant difference in CSA of the disc at L3-L4, L4-L5, and L5-S1 (P < 0.05), muscle-fat ratio (P < 0.01), and muscularity of multifidus and psoas (P < 0.05) from L1 to L5 levels. There was no correlation between age and BMI and the CSA. Ageing led to fatty infiltration in both groups. The CSAs of muscles and discs were comparable (P > 0.05) among subgroups except at a few spinal levels. Muscularity among the subgroups varied at different levels. The muscle-fat ratio was comparable (P > 0.05). Conclusion: Muscularity and composition, rather than overall CSA of important spinal stabilizers, were found to be associated with CLBP. Age and BMI had no correlation with the CSA of paraspinal muscles. Various disc and muscle parameters did not differ much among common lumbar pathologies.