title: Biomechanical properties of the calcaneal tendon in vivo assessed by transient shear wave elastography.
abstract: OBJECTIVE
  The purpose of this study is to assess the elastic and anisotropic properties of normal calcaneal tendon in vivo by transient shear wave elastography (SWE).
  
  
  METHODS
  This study was approved by our institutional ethics committee. Eighty healthy subjects over 18 years of age were prospectively included. Data on the patients' height, weight, sporting activities, and take-off foot were assessed. The thickness, width, and cross-sectional area of the calcaneal tendons were measured. The shear wave propagation velocity (Vmean) was measured by three radiologists on axial and sagittal SWE images at four different degrees of ankle flexion, enabling to calculate elasticity modulus (Emean), and relative anisotropy coefficient (A) values.
  
  
  RESULTS
  In complete plantar flexion, Vmean was 6.8 ± 1.4 m.s(-1) and 5.1 ± 0.8 m.s(-1), respectively, on the sagittal and axial SWE image, resulting in an elastographic anisotropy A of 0.24 ± 0.16. The best interobserver correlation coefficient of Emean and Vmean was 0.43 and 0.46, respectively, in the sagittal SWE for complete plantar flexion. Vmean and Emean significantly increase when the tendon is stretched by ankle dorsiflexion. The maximal values in sagittal SWE were Vmean = 16.1 ± 0.7 m.s(-1), Emean = 779.5 ± 57.1kPa and A = 0.63 ± 0.07.
  
  
  CONCLUSIONS
  SWE allows the elastic properties of the calcaneal tendon to be evaluated quantitatively in vivo, but interobserver reproducibility is questionable. It confirms the tendinous elastographic anisotropy and stiffness augmentation of stretched tendon.
authors.affiliation: Department of Radiology, University Hospital of Besancon, Boulevard Fleming, 25030, Besançon Cedex, France. radio.aubry@free.fr
authors.forename: Sébastien
authors.initials: S
authors.lastname: Aubry
authors.forename: Jean-Romain
authors.initials: JR
authors.lastname: Risson
authors.forename: Adrian
authors.initials: A
authors.lastname: Kastler
authors.forename: Benoit
authors.initials: B
authors.lastname: Barbier-Brion
authors.forename: Gaye
authors.initials: G
authors.lastname: Siliman
authors.forename: Michel
authors.initials: M
authors.lastname: Runge
authors.forename: Bruno
authors.initials: B
authors.lastname: Kastler
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging* / Q000502:physiology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D055119:Elastic Modulus / Q000502:physiology; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D005602:France; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015588:Observer Variation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D033081:Shear Strength / Q000502:physiology; D013718:Tensile Strength / Q000502:physiology; D055815:Young Adult