The screw is a self threading, self blocking screw with angular stabliity. Fixin screws have a 2° conical head which locks into a corresponding 2° tapered cone in the bushings, which are pre-assembled on the plate. This coupling is an expremely stable coupling and eliminates the risk of cross threading between the screw and plate and ensures a simple operative technique. It also permits easy removal of the screws, whether because they have been placed incorrectly intra-operatively or for later removal of the plate.