title: Ultrasound measures of the lumbar multifidus: effect of task and transducer position on reliability.
abstract: OBJECTIVE
  To (1) assess the intra- and inter-rater reliability of different ultrasound (US) measures of the lumbar multifidus muscle in subjects with and without chronic low back pain and (2) test 3 different ways to enhance reliability, that is, by testing different tasks, using a template, and averaging trials within or between days.
  
  
  METHODS
  Cross-sectional repeated-measures design.
  
  
  METHODS
  Laboratory setting.
  
  
  METHODS
  Fifteen subjects with chronic low back pain and 15 control subjects.
  
  
  METHODS
  Subjects (n = 30) performed contralateral arm lifting and contralateral leg lifting while in the prone position. Two 7-second videos of the lumbar multifidus (from rest to contraction) were collected with and without a template (transparency) to reposition the transducer on the skin. One of the two raters repeated the testing 7 to 14 days later to assess intrarater reliability in addition to inter-rater reliability. Reliability was assessed with the generalizability theory as a framework.
  
  
  METHODS
  US imaging measures of the lumbar multifidus thickness were obtained in patients at rest and during standardized contractions (hereafter called primary measures) at 2 vertebral levels and on both sides. These primary measures were used to calculate different, potentially useful US parameters (hereafter called derived measures).
  
  
  RESULTS
  Intrarater reliability was better than inter-rater reliability, and primary measures were more reliable than derived measures. The tasks investigated showed comparable reliability results, and the use of the transducer position template was not effective to increase reliability. Averaging the measures of 3 images increased reliability substantially.
  
  
  CONCLUSIONS
  Optimal reliability requires the use of a single rater and the averaging of at least 3 images per visit. In these conditions, primary measures reach acceptable levels of reliability, which was more difficult to achieve for most derived measures. Arm or leg lifting tasks showed similar reliability, and thus the arm-lifting task is recommended for comparisons with previous studies. The use of a transducer position template is not recommended.
authors.affiliation: Occupational Health and Safety Research Institute Robert-Sauvé, De Maisonneuve Ouest, Montréal, Québec. larchr@irsst.qc.ca
authors.forename: Christian
authors.initials: C
authors.lastname: Larivière
authors.forename: Dany
authors.initials: D
authors.lastname: Gagnon
authors.forename: Eros
authors.initials: E
authors.lastname: De Oliveira
authors.forename: Sharon M
authors.initials: SM
authors.lastname: Henry
authors.forename: Hakim
authors.initials: H
authors.lastname: Mecheri
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Dumas
mesh_terms: D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D064170:Paraspinal Muscles / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D015203:Reproducibility of Results; D014159:Transducers; D014463:Ultrasonography