Quantitative ultrasound mapping of regional variations in shear wave speeds of the aging Achilles tendon

Evaluate the effects of aging on healthy Achilles tendon and aponeurosis shear wave speed (SWS), a quantitative metric which reflects tissue elasticity. 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 15A degrees from R) and slack (plantarflexed 15A degrees from R) postures. 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. 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. aEuro cent Shear wave elastography shows promise as a clinical quantitative ultrasound-based technique. aEuro cent Aging induces location-dependent changes in Achilles tendon shear wave speed. aEuro cent Spatial and postural dependence necessitates careful integration of this approach clinically.