Quantification of Mechanical Properties in Healthy Achilles Tendon Using Continuous Shear Wave Elastography: A Reliability and Validation Study.

The purposes of this study were to (i) evaluate the intra-rater reliability of estimating Achilles tendon mechanical properties with continuous shear wave elastography (cSWE), (ii) propose an equivalent shear modulus comparable to Supersonic Shear Imaging, (iii) demonstrate construct validity of cSWE and (iv) explore relationships between tensile and shear properties. Achilles tendon mechanical properties were estimated with cSWE at four time points throughout a 4-h period and at a 2-wk follow up. Additionally, properties were estimated with cSWE across four different ankle positions. In these four positions, B-mode ultrasound imaging and dynamometry were used to quantify Young's modulus. Intra-rater reliability was fair-to-excellent for Achilles tendon mechanical properties estimated with cSWE. Construct validity was demonstrated with increased ankle dorsiflexion leading to increased mechanical properties. Linear relationships were found between tensile and shear mechanical properties. Findings demonstrate that cSWE has sufficient intra-rater reliability and validity for estimating Achilles tendon mechanical properties.