An expandable interbody spacer includes a first endplate surface located on a first side of the spacer and adapted to contact a vertebral endplate surface of a first vertebral body, a second endplate surface located on a second, opposed, side of the spacer and adapted to contact a vertebral endplate surface of a second, opposed, vertebral body and an expansion mechanism adapted to selectively apply a distracting force between the first endplate surface and the second endplate surface, whereby actuation of the expansion mechanism causes the spacer to transition between a compressed insertion configuration to an expanded fusion configuration. The spacer also includes one or more of a deformable surface, a porosity to promote bone on-growth or through-growth, a stiffness substantially equivalent to cortical bone, and structure distributing loads through the spacer substantially without transferring the loads through higher-stiffness structures.
