Do MRI-derived muscle moment-arms in patients with chronic low back pain differ from healthy individuals? A comparative study

Objectives The present study aimed to estimate the trunk muscles moment-arms in low back pain (LBP) patients and compare this data to those of healthy individuals. This research further explored whether the difference of the moment-arms between these two is a contributing factor to LBP. Methodology Fifty patients with CLBP (group A) and 25 healthy controls (group B) were enrolled. All participants were subjected to magnetic resonance imaging of lumbar spine. Muscle moment-arms were estimated on a T2W axial section parallel to the disc. Results There was statistically significant differences ( p < 0.05) in the sagittal plane moment-arms at L1–L2 for right erector spinae (ES), bilateral psoas and rectus abdominis (RA), right quadratus lumborum (QL), and left obliques; bilateral ES, QL, RA, and right psoas at L2–L3; bilateral QL, RA, and obliques at L3–L4; bilateral RA and obliques at L4–L5; and bilateral psoas, RA, and obliques at L5–S1. There was no statistically significant difference ( p < 0.05) in the coronal plane moment-arms except for left ES and QL at L1–L2; left QL and right RA at L3–L4; right RA and obliques at L4–L5; and bilateral ES and right RA at L5–S1. Conclusions There was a significant difference in muscle moment-arms of the lumbar spine's prime stabilizer (psoas) and primary locomotors (rectus abdominis and obliques) between LBP patients and healthy individuals. This difference in the moment-arms leads to altered compressive forces at intervertebral discs and may be one of the risk factors for LBP.