An assembly for the fixation of a spinal facet joint, including an outer shank, an inner shank and a tip, such that rotation of the inner shank with respect to the outer shank causes the tip to move into the outer shank. Movement of the tip causes deformation of the distal end of the outer shank such that the distal end of the outer shank is larger in diameter than the hole through which it was inserted, said deformation causing increased compression and reduced chance of device loosening.