Biochemical characterization of catilages by a novel approach of blunt impact testing

Abstract

The present article introduces a novel method of characterizing the macromechanical cartilage properties based on dynamic testing. The proposed approach of instrumented impact testing shows the possibility of more detailed investigation of the acting dynamic forces and corresponding deformations within the wide range of strain rates and loads, including the unloading part of stress-strain curves and hysteresis loops. The presented results of the unconfined compression testing of both the native joint cartilage tissues and potential substitute materials outlined the opportunity to measure the dissipation energy and thus to identify the initial mechanical deterioration symptoms and to introduce a better definition of material damage. Based on the analysis of measured specimen deformation, the intact and pathologically changed cartilage tissue can be distinguished and the differences revealed.

Mathematical modeling of linear viscoelastic impact: Application to drop impact testing of articular cartilage

“…In the present study we addressed the question of whether the main features of articular impact observed in [6,7] could be qualitatively predicted using a linear viscoelastic theory or the linear biphasic theory. It is to note that the deformations encountered in impact tests should be small enough for the linear theories to apply.…”

“…The biphasic theory [10], which models the tissue as a mixture of a solid phase and a fluid phase, has demonstrated very good agreement with experimental results in the creep and stress relaxation tests [11]. The objective of this study was to investigate theoretically whether the main features of articular impact observed in [6,7] could be qualitatively predicted using a linear viscoelastic theory or the linear biphasic theory.…”

“…In recent years, a number of experimental studies have been conducted to investigate the mechanical behavior and damage mechanisms of articular cartilage under impact loading [3,4,5]. In particular, the experimental data on relative dissipation of the impact energy ∆E/E 0 versus overall impactor energy E 0 obtained in [6] were fitted with quadratic curves. Here, E 0 = mv 2 0 /2, ∆E = m(v 2 1 − v 2 0 )/2, v 0 and v 1 are the initial impact and rebound velocities, respectively, m is the impactor mass.…”

“…Since, v 1 = −e * v 0 , where e * is the coefficient of restitution, we easily get ∆E/E 0 = 1 − e 2 * . Thus, the experimental data and fitting curves for dissipation of the impact energy [6] can be recalculated in terms of the coefficient of restitution as presented in Fig. 1, which shows a non-monotonic dependence of e * on v 0 .…”

“…Coefficient of restitution e * versus the impact velocity v 0 for articular cartilage samples of different thicknesses. Based on the experimental data and fitting curves obtained in[6].…”