Numerical model of vertebral unit for the nucleus pulposus prosthesis analysis

This paper presents a physiological model of a L4-L5 Functional Vertebral Unit (FVU) based on dimensions extracted from the literature, which is used as a platform for simulation of Nucleus pulposus prostheses prototypes. CAD computational tools and finite element simulations were used for stress analysis considering the anisotropy of the outer annulus fibrosus, and the incompressibility of the inner nucleus pulposus. The mechanical behavior of the FVU is compared to a similar model without nucleus under compressive loads. Numerical results show higher displacements and stress values in the annulus fibrosus that show the importance of the nucleus. The model was modified in order to include tentative design of prosthetic prototypes of the Nucleus pulposus using three different shapes: circular, oval and adjusted to the outer annulus fibrosus geometry, all based on the concept of a Silicone gel-filled prostheses. Finally, the results show that the adjusted design has a better performance at restraining deflections.