title: Changes in the cross-sectional area of multifidus and psoas in patients with unilateral back pain: the relationship to pain and disability.
abstract: METHODS
  Prospective, cross-sectional observational study.
  
  
  OBJECTIVE
  The aim of this study was to determine if there was an association between wasting of psoas and multifidus as observed on MRI scans and the presenting symptoms, reported pathology, pain, or disability of a cohort of patients presenting with unilateral low back pain.
  
  
  BACKGROUND
  Current physiotherapy practice is often based on localized spine stabilizing muscle exercises; most attention has been focused on transversus abdominus and multifidus with relatively little on psoas.
  
  
  METHODS
  Fifty consecutive patients presenting to a back pain triage clinic with unilateral low back pain lasting more than 12 weeks were recruited. The cross-sectional surface area (CSA) of the muscles was measured. Duration of symptoms, rating of pain, self-reported function, and the presence of neural compression were recorded.
  
  
  RESULTS
  Data analysis compared the CSA between the symptomatic and asymptomatic sides. There was a statistically significant difference in CSA between the sides (P < 0.001). There was a positive correlation between the percentage decrease in CSA of psoas on the affected side and with the rating of pain (rho = 0.608, P < 0.01), reported nerve root compression (rho = 0.812, P < 0.01), and the duration of symptoms (rho = 0.886, P < 0.01). There was an association between decrease in the CSA of multifidus and duration of symptoms.
  
  
  CONCLUSIONS
  Atrophy of multifidus has been used as one of the rationales for spine stabilization exercises. The evidence of coexisting atrophy of psoas and multifidus suggests that a future area for study should be selective exercise training of psoas, which is less commonly used in clinical practice.
authors.affiliation: Physiotherapy Research Unit, Nuffield Orthopaedic Centre NHS Trust, Oxford, UK. Karen.Barker@noc.anglox.nhs.uk
authors.forename: Karen L
authors.initials: KL
authors.lastname: Barker
authors.forename: Delva R
authors.initials: DR
authors.lastname: Shamley
authors.forename: David
authors.initials: D
authors.lastname: Jackson
mesh_terms: D000328:Adult; D000368:Aged; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D006233:Persons with Disabilities / Q000534:rehabilitation*; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000473:pathology* / Q000534:rehabilitation*; D008159:Lumbar Vertebrae; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology; D009133:Muscular Atrophy / Q000473:pathology; D011446:Prospective Studies; D016658:Psoas Muscles / Q000473:pathology*; D018709:Statistics, Nonparametric