A Viscoelastic Modeling for Failure Analysis of Human Vertebral Bone Undergoing Quasi-Static and Dynamic Compression

Area of Science:

• Biomechanics
• Orthopedic research
• Computational modeling

Background:

• Vertebral fractures are common, posing challenges for older adults and those with low bone density.
• Accurate prediction of vertebral mechanical response is crucial for understanding spinal injury mechanisms.
• Existing models may not fully capture the complex behavior of vertebrae under various loading conditions.

Purpose of the Study:

• To develop and validate a density-dependent viscoelastic analytical model for predicting vertebral stiffness and fracture force.
• To assess the model's accuracy compared to experimental data under different compression rates.
• To evaluate the benefits of incorporating viscoelasticity and density-dependence in biomechanical models of vertebrae.

Main Methods:

• A composite model representing the vertebral body (cortical shell and trabecular core) was developed.
• Trabecular bone was modeled using a Kelvin-Voigt viscoelastic formulation with density-dependent properties.
• Material parameters were optimized using the Nelder-Mead algorithm with experimental data from cadaveric vertebral specimens.

Main Results:

• The model successfully reproduced experimental trends in specimen-to-specimen mechanical variation.
• Predicted stiffness showed reasonable agreement with measured data.
• Fracture force predictions demonstrated moderate to strong agreement (R²=0.60 to 0.88) with experimental data, outperforming linear elastic models.

Conclusions:

• The density-dependent viscoelastic model provides an improved representation of vertebral mechanical behavior, particularly at higher loading rates.
• The model's simplicity and computational efficiency make it suitable for biomechanical investigations and injury risk prediction.
• This approach offers a valuable tool for understanding spinal injury mechanisms and screening individuals at risk.