title: Poor reproducibility of compression elastography in the Achilles tendon: same day and consecutive day measurements.
abstract: OBJECTIVE
  To determine the reproducibility of compression elastography (CE) when measuring strain data, a measure of stiffness of the human Achilles tendon in vivo, over consecutive measures, consecutive days and when using different foot positions.
  
  
  METHODS
  Eight participants (4 males, 4 females; mean age 25.5 ± 2.51 years, range 21-30 years; height 173.6 ± 11.7 cm, range 156-189 cm) had five consecutive CE measurements taken on one day and a further five CE measures taken, one per day, at the same time of day, every day for a consecutive 5-day period. These 80 measurements were used to assess both the repeatability and reproducibility of the technique. Means, standard deviations, coefficient of variation (CV), Pearson correlation analysis (R) and intra-class correlation coefficients (ICC) were calculated.
  
  
  RESULTS
  For CE data, all CVs were above 53%, R values indicated no-to-weak correlations between measures at best (range 0.01-0.25), and ICC values were all classified in the poor category (range 0.00-0.11). CVs for length and diameter measures were acceptably low indicating a high level of reliability.
  
  
  CONCLUSIONS
  Given the wide variation obtained in the CE results, it was concluded that CE using this specific system has a low level of reproducibility for measuring the stiffness of the human Achilles tendon in vivo over consecutive days, consecutive measures and in different foot positions.
authors.affiliation: Centre for Sport and Exercise Science and Medicine (SESAME), University of Brighton, Carlisle Road, Eastbourne, BN20 7SN, UK. C.E.Payne@brighton.ac.uk.
authors.forename: Catherine
authors.initials: C
authors.lastname: Payne
authors.affiliation: Centre for Sport and Exercise Science and Medicine (SESAME), University of Brighton, Carlisle Road, Eastbourne, BN20 7SN, UK.
authors.forename: Nick
authors.initials: N
authors.lastname: Webborn
authors.affiliation: Centre for Sport and Exercise Science and Medicine (SESAME), University of Brighton, Carlisle Road, Eastbourne, BN20 7SN, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Watt
authors.affiliation: Clinical Imaging Sciences Centre, Brighton and Sussex Medical School, Falmer, BN1 9RR, UK.
authors.forename: Mara
authors.initials: M
authors.lastname: Cercignani
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging* / Q000502:physiology*; D000328:Adult; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D011312:Pressure; D015203:Reproducibility of Results
keywords: Achilles tendon; Compression elastography; Elastography