The Effect of Degenerative Changes on the Stressed State of the Intervertebral Disc and Adjacent Tissues: A Finite Element Study

The work presents a finite element analysis of the mechanical interaction of adjacent tissues in degenerative conditions of the intervertebral disc. To address this, we developed a three-dimensional finite element model that included the L1–L2 vertebrae, the intervertebral disc, and the hyaline endplate. Nonlinear elasticity theory was employed for the numerical computations, allowing for the consideration of hyperelastic properties of soft tissues. The research findings revealed significant trends associated with the increase in stiffness of the intervertebral disc: in the model with severe degeneration of annulus fibrosus and nucleus pulposus, the yield strength on the cortical bone is reached at a displacement of 3.2 mm, whereas with moderate stiffness of annulus fibrosus and nucleus pulposus, the bone's strength reserve is significantly higher, and the maximum stresses under such loading conditions reach 50 MPa. In cases with a healthy intervertebral disc, the established stress values differed by almost 50 percent, the maximum value being 41 MPa.