title: Assessment of association between low back pain and paraspinal muscle atrophy using opposed-phase magnetic resonance imaging: a population-based study among young adults.
abstract: METHODS
  A cross-sectional imaging study of young adults.
  
  
  OBJECTIVE
  To evaluate whether severity of low back symptoms predicts atrophy in the paraspinal muscles of young adults.
  
  
  BACKGROUND
  Although an increased fat content of the lumbar muscles has been observed among adults with chronic LBP, there is limited knowledge of this association in younger populations.
  
  
  METHODS
  The population-based study sample consisted of 554 subjects (321 females and 233 males) from the 1986 Northern Finland Birth Cohort. Latent Class Analysis (LCA) was used to cluster the subjects according to the low back symptoms and functional limitations at 18, 19, and 21 years. The mean age of the subjects at the time of the MRI (magnetic resonance imaging) was 21 years (range, 20-23). Muscle atrophy was evaluated by assessing the fat content of the paraspinal muscles using Opposed-Phase MRI. The cross-sectional areas (CSAs) of the erector spinae and multifidus muscles were also measured.
  
  
  RESULTS
  LCA analysis produced five clusters differing in symptoms, ranging from a cluster (n = 65) in which subjects had high likelihood of symptoms and functional limitations at all time points, to a cluster (n = 165) with no pain ever. The fat content of the multifidus muscles was significantly higher among women than men (14.0% vs. 5.3%, P < 0.001), but it was not significantly associated with symptom severity. The CSA of both erector spinae and multifidus muscles were significantly larger among men than women (P < 0.001 in all of the muscles), but were not associated with pain severity.
  
  
  CONCLUSIONS
  Low back symptoms and functional limitations over a 3-year period were not associated with increased fat content or a reduction in the cross-sectional area of lumbar paraspinal muscles among young adults.
authors.affiliation: Department of Physical and Rehabilitation Medicine, Institute of Clinical Medicine, University of Oulu, Oulu, Finland.
authors.forename: Niko
authors.initials: N
authors.lastname: Paalanne
authors.forename: Jaakko
authors.initials: J
authors.lastname: Niinimäki
authors.forename: Jaro
authors.initials: J
authors.lastname: Karppinen
authors.forename: Simo
authors.initials: S
authors.lastname: Taimela
authors.forename: Pertti
authors.initials: P
authors.lastname: Mutanen
authors.forename: Jani
authors.initials: J
authors.lastname: Takatalo
authors.forename: Raija
authors.initials: R
authors.lastname: Korpelainen
authors.forename: Osmo
authors.initials: O
authors.lastname: Tervonen
mesh_terms: D000704:Analysis of Variance; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000473:pathology; D009134:Muscular Atrophy, Spinal / Q000150:complications / Q000000981:diagnostic imaging*; D010147:Pain Measurement / Q000379:methods; D011859:Radiography; D018570:Risk Assessment; D055815:Young Adult