Creating an open-source two-phase fluid-structure interaction model of a trabecular bone structure validated against a 3D printed experimental trabecular bone structure specimen

Several numerical models are demonstrating the large effect of the interaction between trabecular bone and bone marrow(1). However, the most representative validations published to date have used an approximated geometry(2). This study aimed to create a representative open-source fluid-structure interaction (FSI) model validated against data obtained through experiments on the same structure. The geometry for the mesh of the physiological model was obtained by μ-CT scanning and segmenting the experimental specimen of a trabecular bone structure. The experimental specimen was obtained by μ-CT scanning, segmenting, enlarging and 3D printing a sectioned porcine trabecular bone. The model was set up using the modified fsiFoam solver of the foam-extend-4.0 FSI toolkit. Replicating the experimental testing (20 experiments per fluid, 5 repetitions per experiment), one model was set up using water and one using silicon oil (ν = 3.5e- 4 m2/s) for the fluid domain. A two-phase fluid solver was chosen to mimic the free surface of the fluid during testing. The solid domain was subjected to a vertical displacement of -0.5 mm in 0.13 s as done in the experiments. Pressure data were extracted at the location of the equivalent experimental pressure tappings. After validating the model against the experimental data, the model was run using physiological data input for trabecular bone and a power-law rheology model for bone marrow. The experimental loading of the bone structure resulted in a variation of pressure throughout the structure ranging from 0.01 kPa – 0.025 kPa. The fluid type further influenced this effect. The simulation results for the pressure around the pressure tappings were compared and demonstrated similar variations. The physiological model showed variation in pressure depending on the structural environment as well. The current model reflects the importance of taking into account the sophisticated structure of trabecular bone when creating a validated model. References: (1) Laouira et al., Comput Methods Biomech Biomed Engin, 18:1, 1974-5, 2015. (2) Birmingham. et al., Annals of Biomedical Engineering, 41:4, 814-826