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

OBJECTIVES

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.

MATERIALS AND

METHODS

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.

RESULTS

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.

CONCLUSION

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.