T₂ Mapping Refined Finite Element Modeling to Predict Knee Osteoarthritis Progression

Area of Science:

• Biomechanics
• Biomaterials
• Medical Imaging

Background:

• Finite element models (FEM) are crucial for understanding cartilage mechanics in osteoarthritis (OA).
• Accurate material property assignment in FEM is essential for reliable OA outcome prediction.
• Current methods often assume homogeneous material properties, which may not reflect biological complexity.

Purpose of the Study:

• To develop and validate a novel pipeline for assigning subject-specific cartilage material properties in FEM using T2 relaxometry.
• To compare the predictive performance of T2-refined FEM with traditional homogeneous FEM in an OA patient.

Main Methods:

• A pipeline was developed to map T2 relaxation values from MRI to finite element model elements.
• Young's modulus was directly calculated for each element based on its T2 value.
• A subject-specific FEM of the knee was created and subjected to gait cycle simulations.
• Results were compared against a homogeneous material property model and qualitative MRI Osteoarthritis Knee Score (MOAKS) data.

Main Results:

• The T2-refined model exhibited higher maximum shear strain in areas with moderate cartilage loss compared to the homogeneous model.
• The homogeneous model showed higher maximum principal stress and shear strain in healthy cartilage regions.
• Homogeneous models may underestimate tissue strain in damaged areas and overestimate it in healthy areas.

Conclusions:

• T2-refined material properties provide a more accurate representation of cartilage behavior in FEM than homogeneous assumptions.
• This computationally efficient pipeline enhances subject-specificity for predictive models in OA evaluation.
• The findings support the use of T2 relaxometry for improving the accuracy of biomechanical models in OA research.