title: Using ultrasound to measure the fibre angle of vastus medialis oblique: a cadaveric validation study.
abstract: BACKGROUND
  The assumption that the vastus medialis oblique (VMO) is involved in medial patellar stabilisation has led to speculation that patellofemoral pain (PF) may be a result of abnormal patellar tracking, due to weakness or difference in fibre orientation of the VMO. Recent studies have reported that the VMO fibre angle, measured in vivo with ultrasound (US), is reduced in patellofemoral pain (PF) patients. However, the validity of US in measuring this parameter was not investigated and this would inevitably cast doubt on whether the US results are comparable to direct measurement. The aim of this study was to validate the use of ultrasound (US) in measuring VMO fibre angle by comparing results obtained both from US and direct measurement.
  
  
  METHODS
  The VMO fibre angle was determined in relation to the femoral axis in nine lower limbs from five soft-fixed cadavers, first using US and then by direct measurement.
  
  
  RESULTS
  The Pearson correlation coefficient between the two methods was 0.92 (p<0.01) indicating a very strong relationship. The average difference in measurements between the two methods was 0.20. Bland/Altman analysis showed 95% limit of agreement to be between -2.550 and 30, showing minimal discrepancies between results obtained by the two methods.
  
  
  CONCLUSIONS
  In conclusion, the VMO fibre angle values obtained by the US method were proved to be valid and comparable to those obtained from direct measurement. We show, therefore, that US can be used with confidence to measure VMO fibre angles in the cadaver, and, by implication, in clinical practice.
authors: St. George's, University of London, UK.
authors: Shendy
authors: S
authors: Engelina
authors: Department of Rehabilitation Sciences, Kingston University/St. George's, University of London, UK.
authors: Claire J
authors: CJ
authors: Robertson
authors: Department of Medical Physics and Clinical Engineering, St. George's Healthcare NHS Trust, UK.
authors: James
authors: J
authors: Moggridge
authors: Department of Medical Physics and Clinical Engineering, St. George's Healthcare NHS Trust, UK.
authors: Alban
authors: A
authors: Killingback
authors: Division of Biomedical Sciences (Anatomy), St. George's, University of London, UK. Electronic address: padds@sgul.ac.uk.
authors: Philip
authors: P
authors: Adds
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D008875:Middle Aged; D052097:Quadriceps Muscle / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D014463:Ultrasonography