This invention relates to a spinal fusion system and method for use as a prosthetic implant. The system and method includes a housing dimensioned to be situated between adjacent spinal bones, such as adjacent vertebrae. The housing cooperates with the spinal bones to define at least one or a plurality of graft areas for receiving graft material, which may be pre-packed into the cage or inserted anteriorly into the housing during a surgical operation such as a vertebrectomy or discectomy. A housing may have various features such as migration preventers to prevent the housing from migrating posteriorly towards a spinal column and can be used with a cover that permits the housing to "float" relative thereto. Screws are provided in one embodiment and are dimensioned or configured to lock against each other to retain the screws and, consequently, the cover in place. Another embodiment illustrates a plurality of plate elements that can be slidably received and locked in the cage. Each of the plate elements are adapted to receive at least one screw and guide the screw at a predetermined angle into a vertebra, thereby securing the cage in an inter-vertebral space.
