Intrabiofidelity: A Methodological Proposal to Simulate the Internal Trabecular Structure of Bone Tissue in Finite Element Biomechanical Models

Computational biomechanics has grown substantially alongside imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI), which together enable high-fidelity biomodels of both hard and soft tissues. Most such biomodels, however, are represented as continuous homogeneous solids, limiting their capacity to reproduce the internal architecture of living tissues. Micro-finite element (μFE) analysis has addressed this limitation for bone at sub-millimetric scales using micro-CT data, but its adoption remains constrained by scanner availability, computational cost, and workflow complexity. This work proposes a methodological framework, termed intrabiofidelity, as a taxonomic descriptor complementary to biofidelity that characterizes the degree to which a biomodel reproduces the internal morphology and morphometry of a tissue. A reproducible pipeline based on ScanIP® segmentation of MRI-derived DICOM data, SolidWorks® solidification, and ANSYS® Workbench finite element analysis is presented, through which a macro-scale trabecular representation is extracted from the distal femoral cancellous bone and integrated into a knee biomodel. Two numerical analyses were performed under an equivalent bipodal-standing load with orthotropic material properties for cortical and trabecular bone: one with external biofidelity only (Case 1), and one incorporating macro-scale intrabiofidelity in the trabecular bone (Case 2). The introduction of intrabiofidelity produced a substantial redistribution of peak von Mises stress between compartments. Trabecular peak stress increased from 2.66 to 12.10 MPa (a 4.5-fold elevation), while cortical peak stress decreased from 56.25 to 45.97 MPa (an 18.3% reduction), whereas the volume-averaged stress remained essentially unchanged in both tissues, indicating that intrabiofidelity primarily affects local concentrations rather than the bulk stress state. Principal stress data further revealed that the trabecular region transitions from a low-stress, predominantly compressive state in Case 1 to one in which substantial local tensile and compressive concentrations of comparable magnitude coexist in Case 2. The proposed methodology provides an accessible workflow for macro-scale integration of internal bone architecture using routinely available MRI data and commercial FEA software, and introduces intrabiofidelity as a terminological complement useful for teaching and for systematically documenting the fidelity of computational biomodels.