36. FLEXURAL STRAINS IN ARTICULAR CARTILAGE: EFFECT OF NONLINEAR TENSION-COMPRESSION BEHAVIOR
Name: Gregory M. Williams
Grad Year: 2008
Mechanical loading of cartilage explants can regulate chondrocyte metabolism and direct tissue growth and remodeling. The application of bending deformations to immature articular cartilage can also induce reshaping of the tissue during in vitro culture. Mechanically manipulating cartilage shape through bending may prove useful for engineering shaped chondral grafts for the treatment of cartilage injury and disease. The hypothesis of this study was that nonlinear tension-compression behavior, such as that attributed to cartilage, will result in asymmetrical strain distributions during bending, while a more linear material such as alginate will have reduced asymmetry. Bending deformations were applied to articular cartilage and alginate samples in a configuration used previously for in vitro reshaping of cartilage. Fluorescently labeled nuclei and beads acted as fiducial markers for micromechanical strain analysis. There was a marked asymmetry in compressive and tensile strains in cartilage samples, with the neutral axis located off center, further (~0.76 mm, p<0.001) from the concave surface. The neutral axis was more centrally located (at ~0.55 mm, p=0.09) in alginate samples. The pronounced asymmetry in bending strains in cartilage compared to those in alginate is consistent with the degree of tension-compression nonlinearity in material properties. Testing cartilage in bending offers a unique way to assess the biomechanical behaviors of the tissue at varying magnitudes of compression and tension. Also, the understanding of cartilage strain during bending identifies both compressive and tensile stimuli as possible mediators of cartilage shape-change responses during mechanical molding.