title: Validity of real-time ultrasound imaging to measure anterior hip muscle size: a comparison with magnetic resonance imaging.
abstract: METHODS
  Clinical measurement, criterion standard.
  
  
  OBJECTIVE
  To investigate the validity of real-time ultrasound imaging (USI) to measure individual anterior hip muscle cross-sectional area.
  
  
  BACKGROUND
  The hip flexor muscles are important for hip joint function and could be affected by joint pathology or injury. Objectively documenting individual anterior hip muscle size can be useful in identifying muscle size asymmetry and monitoring treatment efficacy for patients with hip problems. USI offers a novel method of measuring individual muscle size in the clinic, but its validity in measuring the anterior hip muscles has not been investigated.
  
  
  METHODS
  Nine healthy participants (5 males, 4 females) underwent imaging of their iliopsoas, sartorius, and rectus femoris muscles with USI and magnetic resonance imaging. Bilateral muscle cross-sectional areas were measured on images from both modalities.
  
  
  RESULTS
  There was no significant difference (P>.05) in mean cross-sectional area measurements from USI and magnetic resonance imaging for each muscle. Agreement between measurements was high for the iliopsoas (left: intraclass correlation coefficient [ICC3,1] = 0.86; 95% confidence interval [CI]: 0.51, 0.97; right: ICC3,1 = 0.88; 95% CI: 0.57, 0.97), sartorius (left: ICC3,1 = 0.82; 95% CI: 0.41, 0.96; right: ICC3,1 = 0.81; 95% CI: 0.39, 0.95), and rectus femoris (left: ICC3,1 = 0.85; 95% CI: 0.49, 0.96; right: ICC3,1 = 0.89; 95% CI: 0.61, 0.97). Reliability of measuring each muscle with USI was high between 2 trials (ICCs3,1 = 0.84 to 0.94).
  
  
  CONCLUSIONS
  USI is a valid measure of iliopsoas, sartorius, and rectus femoris muscle size in healthy people, as long as a strict measurement protocol is followed.
authors.affiliation: Division of Physiotherapy, The University of Queensland, Brisbane, Australia. dilani.mendis@gmail.com
authors.forename: M Dilani
authors.initials: MD
authors.lastname: Mendis
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Wilson
authors.forename: Warren
authors.initials: W
authors.lastname: Stanton
authors.forename: Julie A
authors.initials: JA
authors.lastname: Hides
mesh_terms: D000328:Adult; D019412:Anatomy, Cross-Sectional; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D014463:Ultrasonography