INTRODUCTION: Lack of adequate nutrition is believed to contribute to degeneration of the intervertebral discs (IVD). Disc cells require nutrients to survive and function; glucose is considered the critical nutrient for cell survival. We developed a 3D finite element model of the IVD with cell viability criteria, and investigated the effects of disc degenerative changes and mechanical compression on nutrient profiles and cell viability in the IVD.
METHODS: Our model, based on mechano‐electrochemical mixture theory, includes anatomical geometry, nutrient concentrations coupled to cell metabolism, and strain‐dependent tissue properties. We also included cell viability criteria based on minimum glucose concentrations needed for cell survival, determined in‐vitro. Effects of degeneration were investigated by altering tissue properties to reflect those of degenerated tissue, including decreased water content, fixed charge density, height, and endplate permeability, as well as variations in mechanical properties based on the literature. Effects of compression were examined by applying a 10% static deformation to the disc.
RESULTS: Degeneration led to a 70% decrease in the minimum glucose concentration and a 25% decrease in averaged cell density, concentrated in the NP region. No cell death occurred in the normal disc. The 10% compressive deformation led to 19% and 5% decreases in minimum glucose concentrations in normal and degenerated IVD, respectively. While no cell death occurred in the normal disc, cell density in the degenerated disc decreased 8% following compression.
DISCUSSION: Our results indicate that both disc degeneration and mechanical strain can lead to decreased nutrient levels in IVD, and subsequent loss of cell viability. This model can predict cell viability in IVD under various conditions, and may therefore serve as a useful tool in developing new treatment strategies. This study provides important insight into mechanisms of disc degeneration.