Spinal mobility and paraspinal muscle degeneration: a cross-sectional analysis from the Berlin Back Study

Chronic low back pain (cLBP) is a major contributor to global disability. This study examined the association between paraspinal muscle morphology and spinal mobility and alignment in individuals with and without cLBP.

In this cross-sectional study, participants were prospectively recruited from the general population. Magnetic resonance imaging (MRI) was used to assess morphological characteristics, namely fatty infiltration (FI) and functional cross-sectional area (fCSA) of the multifidus (MF), erector spinae (ES), and psoas muscles at all lumbar levels individually and averaged. Lumbar mobility (flexion, extension, side-bending) was assessed with a skin surface measurement device. Associations between both parameters were evaluated using multivariable regression models adjusted for demographic, structural, and clinical confounders.

721 participants (56.9% females, 226 without cLBP, 495 with cLBP) with a mean age of 41.8 (SD 12.1) were included. Average MF FI showed the strongest association with flexion in the cLBP group (ß: -0.50, 95% CI-0.66 - -0.34, p < 0.001, η²=0.071), exceeding the influence of age, disc degeneration, and pain intensity. This association was also significant in asymptomatic participants, though weaker (ß: -0.40, 95% CI -0.66 - -0.14, p = 0.003, η²=0.041). Level-specific differences were observed, with MF fCSA at L4/5-L5/S1 and ES fCSA at upper levels showing the strongest association with lumbar mobility.

MRI-based morphology of paraspinal muscles is associated with spinal mobility in both cLBP and asymptomatic individuals, independent of key confounders. Associations were level-, muscle-, and movement-specific, with the strongest effects observed for MF FI and lumbar flexion.