A spinal implant device for placement between vertebral bodies, the device comprising: an expandable shell (14 and 16); at least one wedge or screw member comprising a tapered configuration having an external helical thread (34-40); and at least one drive shaft ; the expandable shell comprising a top member and a bottom member separate from each other, at least the bottom member having step tracking (18 and 20) for receiving the wedge or screw member, the drive shaft being operably engagable with the wedge or screw member for moving the wedge or rotating the screw member along the step tracking, the wedge or screw member engaging the top member and the bottom member, whereby the top member and bottom member move relative to each other in response to movement of the wedge or rotation of the screw member along the step tracking to effect an expansion of the shell, the step tracking further permitting contraction of the shell by reversing the movement of the wedge or rotation of the screw member from that for expansion wherein the step tracking comprises a plurality of riser members (52-60), a height of individual riser members increasing along the step tracking, whereby the wedge or screw member(s) causes the top member and bottom member to move apart from each other to a greater degree as the wedge or screw member(s) moves along the increasing height of the riser members; and the thread(s) of the wedge or screw member(s) is/are received in gaps between the riser members for guiding the wedge or screw member along the step tracking; and a minor diameter of the wedge or screw member engages top edges of the riser members. an expandable shell (14 and 16); at least one wedge or screw member comprising a tapered configuration having an external helical thread (34-40); and at least one drive shaft ; the expandable shell comprising a top member and a bottom member separate from each other, at least the bottom member having step tracking (18 and 20) for receiving the wedge or screw member, the drive shaft being operably engagable with the wedge or screw member for moving the wedge or rotating the screw member along the step tracking, the wedge or screw member engaging the top member and the bottom member, whereby the top member and bottom member move relative to each other in response to movement of the wedge or rotation of the screw member along the step tracking to effect an expansion of the shell, the step tracking further permitting contraction of the shell by reversing the movement of the wedge or rotation of the screw member from that for expansion wherein the step tracking comprises a plurality of riser members (52-60), a height of individual riser members increasing along the step tracking, whereby the wedge or screw member(s) causes the top member and bottom member to move apart from each other to a greater degree as the wedge or screw member(s) moves along the increasing height of the riser members; and the thread(s) of the wedge or screw member(s) is/are received in gaps between the riser members for guiding the wedge or screw member along the step tracking; and a minor diameter of the wedge or screw member engages top edges of the riser members. <EOS>