Expandable spinal fusion devices, systems, and methods of using them are provided, and they can be inserted in a subject in a collapsed state through a small surgical corridor, and the expand cephalocaudal only, transverse only, or in both directions, in which direction of expansion can also be obtained independently, if desired, after the insertion. These inventions are valuable in reducing risk and surgical complexity, allowing for an on-the-fly selection of a desirable width footprint, a desired control of height expansion through a gradual cephalocaudal expansion, and a desired control of the alignment of the adjacent vertebral bodies. Devices, systems, and methods are also offered to provide a desired control of the contact area desired between the device and the upper and lower vertebral endplates achieved, for example, using an interdigitated endplate system.
