Geometry alone? Evaluating the predictive capability of morphed intervertebral disc FEM models with a single material...

Area of Science:

• Biomechanics
• Spinal Mechanics
• Finite Element Analysis

Background:

• Individual intervertebral disc (IVD) characteristics influence spinal mechanics and pain.
• Individualized biomechanical modeling of IVDs is underexplored, particularly concerning material model validity across degeneration grades.
• Current models often use a single material model, potentially limiting accuracy for diverse disc geometries and degeneration levels.

Purpose of the Study:

• To establish and evaluate the femReg algorithm for generating patient-specific lumbar IVD finite element method (FEM) models.
• To assess the capacity of geometry-only individualized IVD models to represent the range of motion (ROM) of degenerated discs.
• To determine if a single material model is sufficient across varying degeneration states.

Main Methods:

• Generated 241 patient-specific lumbar IVD FEM models from MRI images using a single material model.
• Employed the automated morphing algorithm femReg for model generation.
• Simulated models under four load cases (1-7.5 Nm) and compared ROM with in vitro data across degeneration grades.

Main Results:

• Created 241 high-quality hexahedral IVD models with an average runtime of 6 minutes per model.
• Healthy models reproduced experimental ROM with RMSEs of 0.96°-2.05°.
• Degenerated models showed reduced height-normalized ROM compared to in vitro data, indicating a stiffer response.

Conclusions:

• Geometry-only IVD models with a single material model show limitations in representing degenerated disc behavior.
• Degeneration-specific material parameters are necessary for accurate biomechanical modeling of pathological spinal conditions.
• The femReg algorithm efficiently generates patient-specific IVD models for biomechanical simulations.