Tensile properties of human Achilles tendon

There were three foci of this study, The first was a delineation of the effect of two variables on the tensile properties of human Achilles tendon. To that end, the values of the ultimate tensile strength, UTS, strain at the UTS point, epsilon(max), and tangent modulus of elasticity, E-T, of cadaveric Achilles tendon were obtained as a function of(a) donor age (36 to 100 y), at a fixed loading rate of 10 %/s; and (b) loading rate (for tendons from the 52- to 67-year-old donor group). The second focus was the presentation of a suitable constitutive relation between the tensile stress, sigma, and the tensile strain, epsilon, for this tissue. The aim of these two foci was to provide information that will aid in the selection of Achilles tendon for the repair of ruptured Achilles tendons as well as anterior cruciate ligaments (ACLs). The third focus was, thus, a comparison of the tensile properties of Achilles tendon and patellar tendon, which is now widely used for the repair of ruptured ACLs. It was found that: (a) age exerts a marked effect on UTS, an insignificant one on epsilon(max), and a moderate one on E-T; (b) a ten-fold increase in loading rate results in a moderate but insignificant increase in UTS, a significant decrease in epsilon(max), and a significant increase in E-T; (c) a suitable constitutive relation is sigma = C epsilon exp[D epsilon+F epsilon(2)], with C, D, and F being material constants; and (d) the tensile properties of Achilles and patellar tendons have similar values.