The association of lumbar paraspinal muscle size and quality with physical function, disability, and pain in adults with chronic low back pain.
Cristiane R Carlesso, Jaclyn M Sions, William J Anderst and 6 others
Specific lumbar muscle size and quality showed small links to walking speed, balance, and abdominal endurance in chronic low back pain, but no link to disability or pain intensity.
Muscle-alone variance was 2.6–5%; the authors call clinical significance unclear.
Key findings
1After adjusting for age, sex, and BMI, lower erector spinae size was associated with faster 4-minute walk test performance, and lower multifidi size was associated with lower PainDETECT (neuropathic symptom) scores.
2No associations were found between any lumbar paraspinal muscle size or quality and disability (ODI) or pain intensity (NPRS) after adjustment for age, sex, and BMI.
3The muscle-alone contribution to explained variance was small across all significant associations (2.6% for walking speed, 3% for neuropathic symptoms, 4.6% for abdominal endurance, 5% for balance), and the authors state that minimal clinically important thresholds for lumbar paraspinal muscle morphology have not been established.
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What it does not show
Cross-sectional design: it cannot tell you whether smaller or fatter muscles cause poorer function, or whether reduced activity and deconditioning cause the muscle changes. No healthy comparison group, so it is impossible to separate chronic-LBP-specific muscle changes from normal aging or general deconditioning. No adjustment for multiple testing across the many muscle-by-outcome combinations, which raises the chance that some of the six surviving associations are false positives. The quadratus lumborum size finding was driven by BMI (which was positively associated with muscle size and negatively with abdominal endurance), not by the muscle itself. Single site (University of Pittsburgh), 81.3% White, mean age 55 — generalisability to other populations is uncertain. The authors note that minimal clinically important thresholds for lumbar paraspinal muscle morphology have not been established, so it is unknown whether the observed differences matter to a patient.
Declared interests
The authors declare no conflicts of interest. No funding source is named in the text provided.
The easy way to misread this
Do not read these associations as a basis for ordering lumbar CT to guide exercise prescription or to set a patient's functional prognosis. The muscle-alone contribution was 2.6% to 5% of outcome variance, the design is cross-sectional so the direction of effect is unknown, the authors state that minimal clinically important thresholds for muscle morphology have not been established, and the quadratus lumborum size finding was driven by BMI rather than by the muscle itself.
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