Method of Evaluation a Basic Mechanic Property of Cartilage

Abstract

Many osteoarthritis animal models have been studied, attempting to model these findings after those of humans. an animal model that could develop naturally occurring osteoarthritis in a manner similar to humans would be of great benefit for future research. Studies with cynomologous macaques have shown that these animals develop naturally occurring os� teoarthritis similar to that in humans. The goal of the current project was to examine the basic biome� chanical characteristics of normal cynomologous macaque distal femoral articular cartilage as well as to develop a proper biomechanical testing protocol. Testing was performed with the EnduraTEC machine. Using a 0.5mm radius nonpermeable cylindrical indenter, instantaneous linear ramp compressions were applied to the cartilage specimens at a rate of 10 mm/sec to a depth of 0.15 mm. The thickness of the articular cartilage specimen was determined by using the needle probe. A load deformation curve was obtained and analyzed to determine the thickness. Using a linear elastic model, we assumed that compression was instantaneous. Young's Modulus (N/ mm2 = MPa) was calculated by plotting stress (load/crosssectional area) vs. strain (displacement/ thickness) and calculating the equation of the line. Stiffness (N/mm) was obtained by plotting load vs. displacement. Both were reached calculating the bestfit line form the speed compression ramp. Only one previous published experiment attempted to characterize the biomechanical properties of nor� mal cynomologous macaque monkey articular cartilage. Our study attempted to use a more simplified approach to calculate Young's modulus and stiffness. By assuming that the compression was instantane� ous and using an impermeable indenter we were able to calculate what we feel are important biome� chanical properties of articular cartilage.