An fusion cage having a longitudinal element and two planar bendable expansion arms slideably captured in a track on opposing sides, the expansion arms expandable from a pre-implantation position adjacent to the longitudinal element to a deployed position bounding an area around the longitudinal element in which bone graft material may be packed and retained after implantation into the intervertebral space. The longitudinal element is eliminated in favor of front and back lateral tracks in which the opposing ends of the expansion arms are slideably received so as to allow expansion of the bounded areas in both a lateral and anterior-posterior direction by sliding within the channels. Expansion of the area within the bendable members may be accomplished by rotation of leaves to which the bendable members are rigidly and slideably affixed.