Three-dimensional printable metamaterial intramedullary nails with tunable strain for the treatment of long bone fractures

•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.