A
spinal implant device for placement between vertebral bodies includes a housing, at least one screw member in the housing, and at least one
drive shaft operably engageable with the screw member. The housing includes a first shell member and a second shell member. At least the first shell member has
step tracking comprising a plurality of individual riser members for receiving the at least one screw member. The height of the plurality of individual riser members may change along the
step tracking. The
drive shaft may be operable to rotate the at least one screw member, causing the at least one screw member to move on the plurality of individual riser members. The at least one screw member comprises an external
helical thread having a thickness configured to fit in the gaps between adjacent individual riser members, and is engageable with the first and second shell members, whereby the first and second shell members move relative to each other in response to the rotation of the at least one screw member to effect an expansion of the housing or a contraction of the housing from the expansion by reversing the rotation of the at least one screw member.