The invention relates to an implant plate assembly for stabilization of the spine, comprising a first screw receiving socket element at a distal end of said assembly and configured with a screw shank passage and a screw head seat for attachment to a vertebra with the aid of a bone fixation screw, an elongate arm extending proximally from said first socket element and having an elongate through slot therealong, a second screw receiving socket element also configured with a screw shank passage and a screw head seat, and slidably received over said arm with its passage aligned over said slot for receiving the shank of a fixation screw therethrough for attachment to a vertebra. The second screw receiving socket element and the slot configured and dimensioned whereby portions of a screw head of a fixation screw seated in said second screw receiving socket element protude through said second screw receiving socket element passage. The second screw receiving socket element comprises a locking mechanism to prevent movement of the second screw receiving socket element relative to the first screw receiving socket element.
