will engage cooperating threads on an inside surface of the locking member 28 the knob 37 can then be operated to properly torque the implant 40 including to fully seat fastener 44 with locking member 28 the invention provides numerous advantages over prior art pedicle screw fixation systems as the bone joint segments such as the superior facet 160 and inferior facet 164 are compressed between the first washer 20 and second washer 24 there are no internal threads in the bone to raise stresses within the bone the threads 58 are only on the lower end of the shaft 44 such that these threads engage only the locking member 28 and do not apply thread stresses to the interior of the bone also as the implant is tightened using the rotational force conventional torqueing mechanisms can be applied such that a known compressive force is applied to the joint the first washer 20 and second washer 24 can be provided with varied angled contact surfaces to variously fit differing bone geometries for joining bone segments other than the facets also the amount of tilt in the first washer 20 and second washer 24 relative to the fastener 44 can be adjusted depending upon the particular bone geometry that is being fused owing to the pivotal and polyaxial motion that is permitted the installation of the implant 40 is reversible the compression of the implant washers 20 and 24 can be removed to allow repositioning prior to fastener 44 insertion accordingly the invention provides great variability and flexibility in addition to ease control and consistency of installation the various components of the invention are constructed with constructions.