A spinal interbody cage comprising: (a) a bulk interbody cage; (b) a top face being a top exterior surface of the bulk interbody cage and having a top central opening; (c) a bottom face being a bottom exterior surface of the bulk interbody cage and having a bottom central opening; (d) a top mesh structure extending from the bulk interbody cage across the top central opening, comprising top mesh links, and having top mesh openings between the top mesh links, each top mesh link having a width of 100 to 2,000 μm, and each top mesh opening having a mesh opening area of (100 × 100) to (2,500 × 2,500) μm 2; and (e) a bottom mesh structure extending from the bulk interbody cage across the bottom central opening, comprising bottom mesh links, and having bottom mesh openings between the bottom mesh links, each bottom mesh link having a width of 100 to 2,000 μm, and each bottom mesh opening having a mesh opening area of (100 × 100) to (2,500 × 2,500) μm 2; (f) pillars for contacting vertebral bodies, the pillars being distributed on the top face, the bottom face, the top mesh structure, and the bottom mesh structure, and extending distally therefrom, across areas of at least 25 mm 2 of each of the top face, the bottom face, the top mesh structure, and the bottom mesh structure, each pillar that extends from the top face or the bottom face being integral to the bulk interbody cage, each pillar that extends from the top mesh structure or the bottom mesh structure being integral to the top mesh structure or the bottom mesh structure, respectively, and each pillar having a distal end, a transverse area of (100 × 100) to (2,000 × 2,000) μm 2, and a height of 100 to 2,500 μm; and (g) slots to be occupied by bone of the vertebral bodies and/or by bone of a bone graft, the slots being defined by the pillars, the slots intersecting between the pillars, and each slot having a width of 100 to 2,500 μm as measured along the shortest distance between adjacent pillars; wherein: the spinal interbody cage has a Young's modulus of elasticity of at least 3 GPa, and has a ratio of (i) the sum of the volumes of the slots to (ii) the sum of the volumes of the pillars and the volumes of the slots of 0.40:1 to 0.90:1. (a) a bulk interbody cage; (b) a top face being a top exterior surface of the bulk interbody cage and having a top central opening; (c) a bottom face being a bottom exterior surface of the bulk interbody cage and having a bottom central opening; (d) a top mesh structure extending from the bulk interbody cage across the top central opening, comprising top mesh links, and having top mesh openings between the top mesh links, each top mesh link having a width of 100 to 2,000 μm, and each top mesh opening having a mesh opening area of (100 × 100) to (2,500 × 2,500) μm 2; and (e) a bottom mesh structure extending from the bulk interbody cage across the bottom central opening, comprising bottom mesh links, and having bottom mesh openings between the bottom mesh links, each bottom mesh link having a width of 100 to 2,000 μm, and each bottom mesh opening having a mesh opening area of (100 × 100) to (2,500 × 2,500) μm 2; (f) pillars for contacting vertebral bodies, the pillars being distributed on the top face, the bottom face, the top mesh structure, and the bottom mesh structure, and extending distally therefrom, across areas of at least 25 mm 2 of each of the top face, the bottom face, the top mesh structure, and the bottom mesh structure, each pillar that extends from the top face or the bottom face being integral to the bulk interbody cage, each pillar that extends from the top mesh structure or the bottom mesh structure being integral to the top mesh structure or the bottom mesh structure, respectively, and each pillar having a distal end, a transverse area of (100 × 100) to (2,000 × 2,000) μm 2, and a height of 100 to 2,500 μm; and (g) slots to be occupied by bone of the vertebral bodies and/or by bone of a bone graft, the slots being defined by the pillars, the slots intersecting between the pillars, and each slot having a width of 100 to 2,500 μm as measured along the shortest distance between adjacent pillars; wherein: the spinal interbody cage has a Young's modulus of elasticity of at least 3 GPa, and has a ratio of (i) the sum of the volumes of the slots to (ii) the sum of the volumes of the pillars and the volumes of the slots of 0.40:1 to 0.90:1.