title: Quantitative ultrasound mapping of regional variations in shear wave speeds of the aging Achilles tendon.
abstract: OBJECTIVE
  Evaluate the effects of aging on healthy Achilles tendon and aponeurosis shear wave speed (SWS), a quantitative metric which reflects tissue elasticity.
  
  
  METHODS
  Shear wave elastography was used to measure spatial variations in Achilles tendon SWS in healthy young (n = 15, 25 ± 4 years), middle-aged (n = 10, 49 ± 4 years) and older (n = 10, 68 ± 5 years) adults. SWS was separately measured in the free Achilles tendon, soleus aponeurosis and gastrocnemius aponeurosis in resting (R), stretched (dorsiflexed 15° from R) and slack (plantarflexed 15° from R) postures.
  
  
  RESULTS
  SWS significantly increased with stretch and varied with age in all tendon regions. Slack free tendon SWS was significantly higher in older adults than young adults (p = 0.025). However, stretched soleus aponeurosis SWS was significantly lower in older adults than young adults (p = 0.01). Stretched gastrocnemius aponeurosis SWS was significantly lower in both middle-aged (p = 0.003) and older (p = 0.001) adults, relative to younger adults.
  
  
  CONCLUSIONS
  These results suggest that aging alters spatial variations in Achilles tendon elasticity, which could alter deformations within the triceps surae muscle-tendon units, thus affecting injury potential. The observed location- and posture-dependent variations highlight the importance of controlling ankle posture and imaging location when using shear wave approaches clinically to evaluate tendon disorders.
  
  
  CONCLUSIONS
  • Shear wave elastography shows promise as a clinical quantitative ultrasound-based technique. • Aging induces location-dependent changes in Achilles tendon shear wave speed. • Spatial and postural dependence necessitates careful integration of this approach clinically.
authors.affiliation: Department of Radiology, 600 Highland Avenue, University of Wisconsin-Madison, Madison, WI, USA. laura.c.slane@gmail.com.|Institute for Orthopaedic Research and Training (IORT), KU Leuven, UZ Pellenberg, Weligerveld 1 Blok 1, 3212, Pellenberg, Belgium. laura.c.slane@gmail.com.
authors.forename: Laura Chernak
authors.initials: LC
authors.lastname: Slane
authors.affiliation: Materials Science Program, 1415 Engineering Drive, University of Wisconsin-Madison, Madison, WI, USA.
authors.forename: Jack
authors.initials: J
authors.lastname: Martin
authors.affiliation: Department of Radiology, 600 Highland Avenue, University of Wisconsin-Madison, Madison, WI, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: DeWall
authors.affiliation: Materials Science Program, 1415 Engineering Drive, University of Wisconsin-Madison, Madison, WI, USA.|Department of Mechanical Engineering, 1513 University Avenue, University of Wisconsin-Madison, Madison, WI, USA.|Department of Biomedical Engineering, 1513 University Avenue, University of Wisconsin-Madison, Madison, WI, USA.
authors.forename: Darryl
authors.initials: D
authors.lastname: Thelen
authors.affiliation: Department of Radiology, 600 Highland Avenue, University of Wisconsin-Madison, Madison, WI, USA.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Lee
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging* / Q000502:physiology*; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D000843:Ankle Joint / Q000000981:diagnostic imaging; D004548:Elasticity / Q000502:physiology*; D054459:Elasticity Imaging Techniques / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging; D014463:Ultrasonography / Q000379:methods*; D055815:Young Adult
keywords: Aging; Compliance; Elastography; Tendon; Ultrasound