Computed Tomography-Based Stiffness Measures of Trabecular Bone Microstructure: Cadaveric Validation and In Vivo...

Area of Science:

• Biomedical Engineering
• Orthopedics
• Radiology

Background:

• Osteoporosis leads to fragile bones and increased fracture risk.
• Assessing trabecular bone microstructural strength via CT imaging is challenging due to segmentation difficulties.
• Existing methods limit the application of finite element analysis (FEA) for evaluating bone strength.

Purpose of the Study:

• To present a novel nonlinear FEA method for distal tibia CT scans that bypasses the need for trabecular bone microstructure segmentation.
• To account for bone microstructural distribution in FEA, enabling more accurate strength assessments.
• To validate the CT-based FEA method against micro-CT (μCT) and investigate in vivo differences in bone properties between sexes.

Main Methods:

• Developed a nonlinear FEA approach for distal tibia CT scans, aligning the tibial axis with the FE loading axis.
• Modeled FE cubic mesh elements using image voxels and calibrated CT intensity values to ash density for mechanical properties.
• Applied a fixed bottom surface and constant displacement on the top surface of the volume of interest (VOI) to simulate loading conditions, implemented in ANSYS software.

Main Results:

• CT-derived computational modulus values demonstrated high reproducibility (ICC ≥ 0.97) and strong correlation (r ≥ 0.86) with μCT-derived values.
• FEA-derived von Mises stresses were significantly higher in the trabecular bone microregion compared to the marrow space (p < 1 × 10⁻¹¹).
• In vivo analysis revealed higher shear and compressive modulus in males than females (p < 0.01), with effect sizes reduced upon adjustment for lean mass. Pure lean mass and height showed the strongest correlations with modulus measures.

Conclusions:

• CT-based nonlinear FEA effectively serves as a surrogate for measuring trabecular bone microstructural stiffness.
• Eliminating the requirement for binary segmentation broadens the applicability of FEA in human studies using in vivo, lower-resolution imaging.
• The findings provide a more accessible method for evaluating bone strength and fracture risk in clinical settings.