A prosthesis for spinal surgery includes a spacer (12, 612, 712) adapted to be secured into the bone and attached to one of a plurality of configuration plates (40, 140, 240, 640, 640', 740, 740'). The configuration plates (40, 140, 240, 640, 640', 740, 740') are interchangeable and each one is configured to utilize a different combination of bone screws, anchors (80), or both. The prosthesis may further include a retaining mechanism (60) to prevent bone screws and/or anchors (80) from backing out.