Abstract
Tissue scaffolds provide structural support while facilitating tissue growth, but are challenging to design due to diverse property trade-offs. Here, a computational approach was developed for modeling scaffolds with lattice structures of eight different topologies and assessing properties relevant to bone tissue engineering applications. Evaluated properties include porosity, pore size, surface-volume ratio, elastic modulus, shear modulus, and permeability. Lattice topologies were generated by patterning beam-based unit cells, with design parameters for beam diameter and unit cell length. Finite element simulations were conducted for each topology and quantified how elastic modulus and shear modulus scale with porosity, and how permeability scales with porosity cubed over surface-volume ratio squared. Lattices were compared with controlled properties related to porosity and pore size. Relative comparisons suggest that lattice topology leads to specializations in achievable properties. For instance, Cube topologies tend to have high elastic and low shear moduli while Octet topologies have high shear moduli and surface-volume ratios but low permeability. The developed method was utilized to analyze property trade-offs as beam diameter was altered for a given topology, and used to prototype a 3D printed lattice embedded in an interbody cage for spinal fusion treatments. Findings provide a basis for modeling and understanding relative differences among beam-based lattices designed to facilitate bone tissue growth.
Highlights
Tissue scaffolds provide in vivo mechanical support while facilitating targeted tissue growth, and are commonly used as external intervention in regenerative medicine for supporting bone growth [1]
Trends among lattice porosity P, pore size p, and surface-volume ratio S/V were analyzed by altering beam diameter ø and unit cell length Lc to facilitate topology comparisons with controlled porosity
The relative difference in pore size among topologies depends on the ratio of pore size to unit cell length and the diameter to length ratio of beams at a given porosity
Summary
Tissue scaffolds provide in vivo mechanical support while facilitating targeted tissue growth, and are commonly used as external intervention in regenerative medicine for supporting bone growth [1]. Designed lattices for tissue engineering with favorable mechanical properties [3,4,5,6]. Stretch-dominated lattices with beams deforming axially under load can achieve a higher mechanical efficiency compared to bending dominated structures of similar density, such as foams [7,8,9,10]. Recent studies have demonstrated the capacity for tissue growth on beam-based lattices that inform computational approaches for scaffold design [11,12,13]. Our aim is to computationally model lattices with designed properties suitable for tissue engineering, and provide a basis for comparing lattices as porous structures for bone growth, using a spinal interbody fusion cage application to inform lattice design decisions
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