Fat infiltration of paraspinal muscles is associated with low back pain, disability, and structural abnormalities in community-based adults

Low back pain and disability are major public health problems and may be related to paraspinal muscle abnormalities, such as a reduction in muscle size and muscle fat content.The aim of this study was to examine the associations between paraspinal muscle size and fat content with lumbar spine symptoms and structure.This was a community-based magnetic resonance imaging (MRI) cohort study.A total of 72 adults not selected on the basis of low back pain were included in the study.The outcomes measured were lumbar modic change and intervertebral disc height. Pain intensity and disability were measured from the Chronic Pain Grade Questionnaire at the time of MRI.The cross-sectional area (CSA) and amount of fat in multifidus and erector spinae (high percentage defined by >50% of muscle) were measured, and their association with outcome was assessed.Muscle CSA was not associated with low back pain/disability or structure. High percentage of fat in multifidus was associated with an increased risk of high-intensity pain/disability (odds ratio [OR], 12.6; 95% confidence interval [CI], 2.0-78.3; p=.007) and modic change (OR, 4.3; 95% CI, 1.1-17.3; p=.04). High fat replacement of erector spinae was associated with reduced intervertebral disc height (β=-0.9 mm; 95% CI, -1.4 to -0.3; p=.002) and modic change (OR, 4.9; 95% CI, 1.1-21.9; p=.04).Paraspinal fat infiltration, but not muscle CSA, was associated with high-intensity pain/disability and structural abnormalities in the lumbar spine. Although cause and effect cannot be determined from this cross-sectional study, longitudinal data will help to determine whether disabling low back pain and structural abnormalities of the spine are a cause or result of fat replacement of paraspinal muscles.