Abstract
[Display omitted]
•Three different models of 3D printable titanium cylindrical, pillar and reference metamaterials were prepared.•Design parameters were tuned for axial compression under 20% body weight and examined for torsional and bending tests.•Stable cylindrical metamaterial design was further used into the intramedullary nails to produce 5 ∼ 20% interfragmentary strain at fracture site.•Finite element analysis was used to check the biomechanical performance of metamaterial IM nails for bone union.•Metamaterial IM nail with 10% (S2) interfragmentary strain deformed with only 100 N gave maximum healing performance.
Novel metamaterial unit cells with tunable strain were incorporated into titanium intramedullary (IM) nails to overcome problems of dense metallic implants. Three-dimensional (3D) models of cylindrical, pillar, and reference metamaterials were tuned and analyzed for structural authentication. Further, one solid IM nail (S0) and four different cylindrical metamaterial cell IM nails with gap sizes of 0.15 mm, 0.30 mm, 0.45 mm, and 0.60 mm were used to achieve 5% (S1), 10% (S2), 15% (S3), and 20% (S4) strain, respectively, in a 3-mm fracture, to investigate the healing outcomes. The bending stiffness (callus quality) in the S2 metamaterial IM nail increased by 22% between the 7th and 16th iterations, whereas for the S0, S1, S3, and S4 IM nails, the increases were 5.6%, 8.1%, 12.4%, and 9.0%, respectively. The S2 IM nail exhibited the best healing and bending stiffness; however, the S0 IM nail exhibited the worst results. This unique design was customized for different fracture gap sizes according to patient-specific needs.