A bone plate locking cannula and drill guide assembly having a locking cannula detachably mountable onto screw-receiving apertures of a bone plate and a drill guide received within the locking cannula such that pilot holes are drilled through the apertures into bone at the proper angle to receive bone screws. The screw receiving apertures have a proximal bore of greater diameter than a distal bore, and the proximal bore is provided with internal threading to mate with external threading located on the distal end of the locking cannula. The bone screws are inserted through the locking cannula after removal of the drill guide and fastened into the bone to secure the bone plate in position without having to remove the locking cannulas from the bone plate, the internal diameter of the locking cannula bore being greater than the maximum diameter of the screw heads. The locking cannula is detached from the bone plate after the bone plate has been secured in place on the bone.