title: Are MRI-defined fat infiltrations in the multifidus muscles associated with low back pain?
abstract: BACKGROUND
  Because training of the lumbar muscles is a commonly recommended intervention in low back pain (LBP), it is important to clarify whether lumbar muscle atrophy is related to LBP. Fat infiltration seems to be a late stage of muscular degeneration, and can be measured in a non-invasive manner using magnetic resonance imaging. The purpose of this study was to investigate if fat infiltration in the lumbar multifidus muscles (LMM) is associated with LBP in adults and adolescents.
  
  
  METHODS
  In total, 412 adults (40-year-olds) and 442 adolescents (13-year-olds) from the general Danish population participated in this cross-sectional cohort study. People with LBP were identified through questionnaires. Using MRI, fat infiltration of the LMM was visually graded as none, slight or severe. Odds ratios were calculated for both age groups, taking into account sex, body composition and leisure time physical activity for both groups, and physical workload (in adults only) or daily bicycling (in adolescents only).
  
  
  RESULTS
  Fat infiltration was noted in 81% of the adults but only 14% of the adolescents. In the adults, severe fat infiltration was strongly associated with ever having had LBP (OR 9.2; 95% CI 2.0-43.2), and with having LBP in the past year (OR 4.1; 1.5-11.2), but there was no such association in adolescents. None of the investigated moderating factors had an obvious effect on the OR in the adults.
  
  
  CONCLUSIONS
  Fat infiltration in the LMM is strongly associated with LBP in adults only. However, it will be necessary to quantify these measurements objectively and to investigate the direction of this link longitudinally in order to determine if the abnormal muscle is the cause of LBP or vice versa.
authors.affiliation: The Back Research Center, Backcenter Funen, Part of Clinical Locomotion Science, University of Southern Denmark, Denmark. pkrj@shf.fyns-amt.dk
authors.forename: Per
authors.initials: P
authors.lastname: Kjaer
authors.forename: Tom
authors.initials: T
authors.lastname: Bendix
authors.forename: Joan Solgaard
authors.initials: JS
authors.lastname: Sorensen
authors.forename: Lars
authors.initials: L
authors.lastname: Korsholm
authors.forename: Charlotte
authors.initials: C
authors.lastname: Leboeuf-Yde
mesh_terms: D000273:Adipose Tissue / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000209:etiology* / Q000473:pathology*; D008161:Lumbosacral Region; D008279:Magnetic Resonance Imaging; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology*