A spinal fusion apparatus includes a cage body configured to be inserted between two vertebral bodies and which has internal sidewalls that define a cavity which extends vertically through the cage body, and an internal compression member which includes a movable sidewall which defines at least one side of the cavity, and which is movable in a lateral direction from a first position located in the cavity to a second position located in the cavity such that a space within the cavity is reduced when the movable sidewall is at the second position. The internal compression member includes a compression mechanism coupled to the moveable sidewall, and moves the movable sidewall from the first position to the second position. Fusion material is disposed in the cavity is compressed and compacted by the movable sidewall as the moveable sidewall moves from the first position to the second position.