Numerical Evaluation and Prediction of Porous Implant Design and Flow Performance

Abstract

Porous structure has been widely acknowledged as important factor for mass transfer and tissue regeneration. This study investigates effect of aimed-control design on mass transfer and tissue regeneration of porous implant with regular unit cell. Two shapes of unit cells (Octet truss, and Rhombic dodecahedron) were selected, which have similar symmetrical structure and are commonly used in practice. Through parametric design, porous scaffolds with the strut sizes of φ 0.5, 0.7, 0.9, and 1.1mm were created, respectively. Then using fluid flow simulation method, flow velocity, permeability, and shear stress which could reflect the properties of mass transfer and tissue regeneration were compared and evaluated, and the relationships between porous structure's physical parameters and flow performance were studied. Results demonstrated that unit cell shape and strut size greatly determine and influence other physical parameters and flow performances of porous implant. With the increasing of strut size, pore size and porosity linearly decrease, but the volume, surface area, and specific surface area increased. Importantly, implant with smaller strut size resulted in smaller flow velocity directly but greater permeability and more appropriate shear stress, which should be beneficial to cell attachment and proliferation. This study confirmed that porous implant with different unit cell shows different performances of mass transfer and tissue regeneration, and unit cell shape and strut size play vital roles in the control design. These findings could facilitate the quantitative assessment and optimization of the porous implant.

Evaluation and Prediction of Mass Transport Properties for Porous Implant with Different Unit Cells: A Numerical Study

“…Besides, in order to compare the results intuitively, the same numbers of trajectory lines were depicted and amplified by the uniform multiple. In the meantime, one cloud chart was shared for the three shapes [23]. Obviously, curvatures of the trajectories were quite different from each other, and the descending order of flow velocity is RD, OT, and DO.…”

“…Specifically, volume and surface area were analyzed automatically in the SolidWorks software, and max-pore size could be measured manually. Further on, porosity and surface-to volume ratio were calculated as [23, 27]T17p=V0−VV0×100%s=VS∗where V 0 and V are the volumes of the solid initial structure and porous structure, respectively, and S ∗ is the surface area of porous structure.…”

“…Namely, the enclosed tube was filled with DMEM, and then porous scaffolds were immersed in one by one. Meanwhile, for the three shapes, the same boundary conditions were defined as: an inlet velocity (v i = 1 mm/s) at the inlet-flow side and an output environmental pressure (one Atm pressure) at the opposite-flow side [23]. It is worth noting that the aim of the chosen boundary conditions was to imitate cell culture of porous implant in vitro.…”

“…It is worth noting that the aim of the chosen boundary conditions was to imitate cell culture of porous implant in vitro. Besides, diagonal section, middle section (Figure 2(c)), and middle line views (Figure 2(d)) of the porous scaffolds were stressed and used to display inner flow velocity and shear stress [23]. Furthermore, the governing equation underlying the calculation was the Navier-Stokes formulation in this study, which could be expressed as (3).…”

“…Therefore, based on the above state and our previous study [23], this study focused on the regular unit cell and chose one diagonal-symmetrical regular unit cell and two midline-symmetrical regular unit cells, which are commonly used in actual design. From the biological viewpoints, singe unit cells were design quantitatively, and corresponding scaffolds were created with same porosity and scaffold size.…”