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

Area of Science:

• Biomaterials Engineering
• Computational Biomechanics
• Polymer Science

Background:

• Natural intervertebral discs exhibit complex regional variations in microstructure and mechanical properties.
• Existing disc prostheses often fail to replicate this natural heterogeneity, leading to suboptimal biomechanical performance.
• Functionally graded polymers (FGP) present a unique material solution due to their tunable, continuous property gradients.

Purpose of the Study:

• To evaluate the biomechanical response and stress distribution of a novel intervertebral disc prosthesis utilizing FGP.
• To design and optimize FGP parameters based on experimental data and physiological loading conditions.
• To explore the potential for patient-specific FGP disc prostheses through 3D printing.

Main Methods:

• Finite element analysis (FEA) was employed to simulate the biomechanical behavior of the FGP disc prosthesis.
• FGP kinetics were designed using experimental data from linear ethylene copolymers across a range of crystallinities.
• The radial variation of crystallinity index within the prosthesis followed a specific function to tailor FGP parameters.
• FEA models were validated against experimental data from healthy human cervical spine segments under various physiological loads (rotation, lateral bending, flexion/extension).

Main Results:

• The study successfully demonstrated the capability of FGP to mimic the gradual and continuous property variations found in natural intervertebral discs.
• Tailoring FGP parameters allowed for control over key mechanical characteristics, including stiffening, non-linear behavior, and inelastic effects.
• FEA predicted optimal FGP parameters for the disc prosthesis, showing favorable stress distribution under physiological loading.
• The findings highlight the significant potential for developing patient-specific FGP prostheses.

Conclusions:

• FGP are highly suitable for designing intervertebral disc prostheses that can replicate the biomechanics of native soft tissues.
• The ability to tailor FGP parameters offers a pathway to optimize prosthesis performance and mitigate stress concentrations.
• This research paves the way for advanced, patient-specific spinal implants manufactured using 3D printing technologies.