Characterizing Uniaxial Mechanics of Single AF Lamella

Abstract

Intervertebral discs (IVD) are shock absorbers made of sheets of collagen fibers that are located between the vertebrae of the spine. They are known to serve as a cushion to absorb impact and protect body structures, as joints that allow the movement of the vertebrae, and as ligaments that hold the adjacent vertebra. Over time, the human aging process causes IVD to degenerate, diminishing its size and reducing its ability to absorb impact. Therefore, investigations of material properties of IVD in physiologically comparable environments provide information to improving modeling and understanding of IVD degeneration. In this study, the mechanical properties of cadaveric single AF lamella were characterized in uniaxial loading conditions, where loads on the single sheet of IVD were applied in one direction. Analyzing the load-displacement curves and strains maps and comparing them for each samples showed the importance of the fiber alignment in on the sample. That is, strains to the samples were directly aligned to the sample fiber rotation, making the tensile behavior vary within the sample. The results also confirmed the tensile nonlinearity by comparing the slope in toe region (Etoe) and in a linear region (Elin). Although the study is limited by a small number of specimens, the result strengthen the importance of uniaxial tests for fiber-reinforced soft tissues and helped towards understanding material properties to consider when engineering a replacement tissue.