title: Multifidus atrophy is localized and bilateral in active persons with chronic unilateral low back pain.
abstract: OBJECTIVE
  To compare the lumbar multifidi muscle volume devoid of fat local to the site of pain in persons with and without chronic unilateral lower lumbar pain.
  
  
  METHODS
  Prospective cross-sectional design.
  
  
  METHODS
  University biokinesiology laboratory.
  
  
  METHODS
  Active individuals (n=14) with chronic unilateral lower lumbar pain (>1 y) were matched for age, height, weight, and activity level with healthy individuals (n=14). Individuals with back pain had minimal disability (Oswestry Disability Index [mean ± SD], 14.9%±6.3%) at the time of testing.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Multifidus and erector spinae muscle volumes at the L5-S1 levels, multifidus muscle volumes at the L4 and S2-3 levels.
  
  
  RESULTS
  Average multifidus volume was diminished by 18.1% between groups (P=.026) only at the L5-S1 levels. There was no difference between painful and pain-free sides. There were no volume differences between groups above L5, below S1, or in erector spinae at the L5-S1 levels.
  
  
  CONCLUSIONS
  The results of this study indicate that despite a low level of disability and an activity level similar to that of matched control subjects, considerable localized, bilateral multifidus atrophy is present. Such impaired size of the multifidus will likely reduce its capacity to control intersegmental motion, thus increasing the susceptibility to further injury. Unlike acute unilateral low back pain (LBP), muscle size is reduced bilaterally in persons with chronic unilateral LBP.
authors.affiliation: Department of Physical Therapy, California State University Long Beach, Long Beach, CA 90840, USA. gbeneck@csulb.edu
authors.forename: George J
authors.initials: GJ
authors.lastname: Beneck
authors.forename: Kornelia
authors.initials: K
authors.lastname: Kulig
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D017116:Low Back Pain / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D016555:Matched-Pair Analysis; D018482:Muscle, Skeletal / Q000473:pathology*; D009133:Muscular Atrophy / Q000473:pathology*; D011446:Prospective Studies