Spinal interbody cages are provided that include a bulk interbody cage, a top face, a bottom face, a top mesh structure, a bottom mesh structure, pillars, and slots. The top and bottom faces are exterior surfaces of the bulk interbody cage having a top central opening and a bottom central opening, respectively. The top and bottom mesh structures extend from the bulk interbody cage across the top central opening and the bottom central opening, respectively. The pillars are for contacting vertebral bodies. The slots are to be occupied by bone of the vertebral bodies and/or by bone of a bone graft. The spinal interbody cage has a Young's modulus of elasticity of at least 3 GPa, and has a ratio of the sum of (i) 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.