Biomechanical response of a novel intervertebral disc prosthesis using functionally graded polymers: A finite element study.

With their gradual and continuous properties, functionally graded polymers (FGP) have high potentials to reproduce the regional variation in microstructure/property of the natural intervertebral disc and, therefore, the functional anatomy and biomechanics of the soft tissue. This paper evaluates by finite element analysis the biomechanical response and stress distribution of a novel disc prosthesis using FGP. The kinetics of the FGP parameters is designed using experimental data issued from linear ethylene copolymers over a wide crystallinity range. The radial variation in crystallinity index within the disc prosthesis varies gradually and continuously following a special function in the aim to tailor and optimize the FGP parameters. The experimental data of a healthy human cervical spine segment are used to predict the optimal model of the FGP disc prosthesis loaded under different physiological loading conditions, i.e. rotation, lateral bending and flexion/extension. The results suggest that the FGP parameters can be tailored to control the stiffening, the non-linear behavior, the inelastic effects and the stress distribution in the aim to propose the optimal prosthesis model giving the great opportunity of patient-specific FGP prostheses via 3D printing technologies.