A Bioinspired Lattice Bone Scaffold with Tunable Transverse Isotropy Based on a Modified Octet–Truss Unit Cell

Large bone defects, especially in load-bearing regions such as the diaphysis of long bones, require scaffolds that not only support biological integration but also replicate the anisotropic mechanical behavior of native bone tissue. This study presents the design of a novel lattice bone scaffold that utilizes a unit cell (OT-C), created by combining octet-truss and cross-strut geometries to mimic the transverse isotropy of cortical bone. Using numerical homogenization, the influence of porosity and longitudinal expansion on the effective longitudinal ( E 3 ) and transverse ( E 1 ) Young’s moduli was investigated. The results demonstrate that applying a longitudinal expansion to the nearly isotropic OT-C structure induces transverse isotropic behavior, allowing control over the stiffness values ( E 1 , E 3 ) and their ratio ( E 3 / E 1 ) to closely match that of native cortical bone. Experimental validation using compression tests on Ti-6Al-4V SLM-fabricated samples demonstrated good agreement with numerical predictions. A scaffold with an expansion ratio of 1.4 and 60% porosity was identified as optimal, achieving E 1 ≈ 13 GPa, E 3 ≈ 22.5 GPa, and E 3 / E 1 ≈ 1.73—closely aligning with human cortical bone. The proposed methodology provides a robust framework for designing load-bearing bone scaffolds with tailored anisotropic properties, enhancing biomechanical compatibility and supporting functional bone regeneration.