Abstract: The present invention is a polyaxial locking screw plate assembly for immobilization of vertebral bones, via fixation to surfaces thereof. The invention includes a plate, having an upper portion and a lower portion, each of which has a pair of holes having a threaded upper portion and a tapered lower portion. Coupling elements, including slideably joined socket and cap portions, are mounted about the semi-spherical heads of bone screws, which are screwed through the holes in the plate and into the bone. The heads of the screws are polyaxially mounted in the socket portions and as such may be inserted into the bone at a variety of angles. The socket portions of the coupling elements have slots in them which permit crush locking of the heads of the screws once the sockets seat and are forceably driven into the tapered portions of the corresponding holes.