Evaluation of the influence of cartilage endplates composition gradient on intervertebral disc degeneration

Abstract

Intervertebral disc (IVD) degeneration is one of the leading causes of Low Back Pain (LBP), a main cause of disability affecting 7.5% of global population. IVD degeneration has been directly related to alterations in the nutrition of the IVD. The main nutrition pathways are diffusion through the cartilage endplates (CEPs) and the capillaries surrounding the disc rim. Nevertheless, the role of the CEPs in IVD degeneration is unclear. Experimental models showed a change in composition through the CEP, influencing its biochemical and transport properties. Numerical models can complement these results addressing the study of IVD degeneration. A previous 2D study showed that CEP gradient of permeability had influence in the mass exchange, however, the exploration of the influence of such gradient in a 3D model remains unexplored. Hence, the aim of this project is to study the influence of CEP composition gradient on IVD degeneration using a 3D Finite Element IVD mechano-transport model. Two composition gradients were used, defined on a 2-layer CEP and a 4-layer CEP of elements, in two conditions Grade I (GI) and Grade III (GIII) of degeneration. On the one hand, fluid velocity and mass flow were studied by simulating a daily cycle activity. On the other hand, solutes concentrations and cell viability were explored during three days. Results showed a reduction in 24.60% of mass flow at the boundary CEP-Nucleus when using CEP composition gradient on GI and 11.98% on GIII. Glucose concentration decreased 29.76% and 8.40% on GI and GIII, respectively, inducing cell death at the anterior zone of the disc. The results suggest that it is important to consider the CEP composition gradient as it might act as a barrier in the solutes transport. Next step would be to implement the gradient on a patient-specific IVD cohort for better understanding IVD degeneration. Such knowledge might contribute to generate personalised treatment to enhance the quality of life of patient with LBP.