Correlation between the shear wave speed in tendon and its elasticity properties

Abstract

Mechanical properties, such as the Young's modulus, of the tendon are highly correlated to its pathological state. The isolated tensile testing is the conventional method for measuring the Young's modulus of tendon. However, it is an invasive process and is not suitable for early diagnosis. A non-invasive method for measuring the Young's modulus of tendon is thus highly desired. Recently, shear wave elasticity imaging has been widely used to quantify the elasticity property of soft tissue non-invasively. Up to date, the relation between the Young's modulus (E) and the shear wave speed (Vs), (i.e., E-V relation), of tendon is still difficult to formulate. In this study, five porcine tendons were used to test the correlation between the relation between shear wave speed and Young's modulus in a normal and a collagenase-induced diseased model. The measurement of the Young's modulus was accomplished on a step motor with a load cell. Different degrees of pre-loading ranging from 0.5 to 3N were used to change the elastic properties both in normal and diseased models. For each loading condition, a fully preprogrammed array system was used to generate and detect the shear wave speed. The measured Young's modulus under different degrees of preloading are highly correlated with the shear wave speed in both normal and diseased models. The averaged correlation coefficients between the wave speed and elastic modulus in normal and diseased models are 0.97±0.02 and 0.99 ± 0.005, respectively. We further use a second order polynomial to model the E-Vs relation. The scaling coefficient was found to be 0.104 and 0.117, respectively, for the normal and the diseased model. When all data points were adopted in the fitting, the scaling coefficient was 0.107. Based on these results, we found that the E-Vs relation is similar in both the normal and diseased model. The shear wave speed can be an index for quantifying Young's modulus of tendon. Our findings may provide a new strategy for tendon function investigation in clinical practice.