A device for insertion into a spinal (intervertebral or intravertebral) space is expandable and contractable. The device includes a body assembly, a top member configured to fit within a gap in the body assembly, a drive gear disposed within the body assembly at a distal end of the body assembly, a proximal gear assembly, and a distal gear assembly. The drive gear includes a receiver accessible from outside the body assembly and configured to be rotated in order to rotate the drive gear. Each gear assembly is attached to the top member. The distal gear assembly engages the drive gear. Rotation of the drive gear in a first direction causes the gear assemblies to translate the top member away from the body assembly, and rotation of the drive gear in a second direction causes the gear assemblies to translate the top member towards the body assembly.