title: Extended field of view ultrasound imaging to evaluate Achilles tendon length and thickness: a reliability and validity study.
abstract: BACKGROUND
  Achilles tendon structural changes are common after injury and correlate with recovery of function. Having simple, inexpensive, yet valid and reliable measures of Achilles tendon structure are useful both in research and clinical. The purpose of this study was to perform reliability and validity measures of extended field of view (EFOV) ultrasound (US) imaging of the Achilles tendon.
  
  
  METHODS
  eight cadavers (16 tendons) were used for the validation study to compare Achilles tendon length measurements from US images with actual measured length from dissected tendons. Nine healthy subjects (18 tendons) were included in the test-retest evaluation.
  
  
  RESULTS
  the correlation between the US images and cadaveric measurements was excellent (ICC=0.895) for the length between calcaneus and the gastrocnemius and good (ICC=0.744) for the length between the calcaneus and the soleus. The between-limb reliability was excellent (ICC 0.886-0.940) for the tendon length measurements with standard error of measurements (SEM) of 0.64 cm for calcaneus to soleus and 0.67 cm for calcaneus to gastrocnemius. Between-day test-retest reliability was also excellent (ICC=0.898-0.944).
  
  
  CONCLUSIONS
  this study supports the use of EFOV US imaging as a reliable and valid method to determine Achilles tendon length and thickness, and using the uninjured limb for comparison.
authors.affiliation: Department of Physical Therapy, University of Delaware, Newark, USA.
authors.forename: Karin Gravare
authors.initials: KG
authors.lastname: Silbernagel
authors.affiliation: Department of Physical Therapy for University of the Sciences, Philadelphia, USA.
authors.forename: Kristen
authors.initials: K
authors.lastname: Shelley
authors.affiliation: Department of Physical Therapy for University of the Sciences, Philadelphia, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Powell
authors.affiliation: Department of Physical Therapy for University of the Sciences, Philadelphia, USA.
authors.forename: Shaun
authors.initials: S
authors.lastname: Varrecchia
keywords: Achilles tendon rupture; extended field of view imaging; tendon elongation; triceps surae; ultrasound imaging