Alteration of lumbar muscle morphology and composition in relation to low back pain: a systematic review and meta-analysis

BACKGROUND CONTEXT: Previous studies have proposed that there is a relationship between low back pain (LBP) and morphology and composition of paraspinal muscles. However, results have been conflicting, especially regarding fatty infiltration of muscles. PURPOSE: The primary goal of this study was to review and analyze results from imaging studies which investigated morphological and composition changes in the multifidus, erector spinae and psoas major muscles in people with LBP. STUDY DESIGN/SETTING: Systematic review with meta-analysis. PATIENT SAMPLE: A patient sample was not required OUTCOME MEASURES: This review did not have outcome measures. METHODS: PubMed, Scopus, Web of Sciences, EMBASE and ProQuest were searched for eligible studies up to 31st July 2020 (all languages). A systematic search of electronic databases was conducted to identify studies investigating the association between the morphology and fat content of lumbar muscles in people with LBP compared with a (no LBP) control group. 13,795 articles were identified. Based on the screening for inclusion/ exclusion, 25 were included. The quality of the studies was evaluated using the Newcastle-Ottawa Scale. From the 25 articles, 20 were included in the meta-analysis. RESULTS: Results showed that the total cross-sectional area of the multifidus was smaller in people with LBP (Standardized mean difference, SMD =-0.24, 95% CI =-0.5 to 0.03). Combined SMDs showed a medium effect of LBP on increasing multifidus muscle fat infiltration (SMD = 0.61, 95% CI = 0.30 to 0.91). There were no LBP related differences identified in the morphology or composition of the lumbar erector spine and psoas major muscles. CONCLUSIONS: People with LBP were found to have somewhat smaller multifidus muscles with a significant amount of intramuscular fat infiltration. Varying sample size, age and BMI of participants, quality of studies and the procedures used to measure fat infiltration are possible reasons for inconsistencies in results of previous studies. (C) 2021 Elsevier Inc. All rights reserved.