Patent ID: 8439957

Claim:
An implant assembly adapted to be fixed to a bone using at least one bone screw having a thinner region and a thicker region, which implant assembly comprises: an implant member, which implant member has an aperture extending through the implant member, wherein the aperture includes a first region sized to permit the thinner region of the bone screw but not the thicker region of the bone screw to pass through and the aperture includes a second region sized to permit both the thinner region of the bone screw and the thicker region of the bone screw to pass through; a first interior perimeter surface in the implant member defined by the first region of the aperture; a second interior perimeter surface in the implant member defined by the second region of the aperture; and a washer disposed within the aperture in the second region thereof, which washer has a hole large enough to permit both the thinner region of the bone screw and the thicker region of the bone screw to pass through and which washer has at least a first region with a first wall thickness and a second region with a second wall thickness, wherein the first wall thickness is greater than the second wall thickness; wherein, when the bone screw is inserted in the aperture of the implant member and the hole of the washer such that the thicker region of the bone screw is in the second region of the aperture, rotation of the washer causes movement of the first region of the washer relative to the second interior perimeter surface such that the washer applies force to the bone screw to press the bone screw against the implant member and to fix the bone screw in orientation relative to the implant member; wherein the second interior perimeter surface includes a recess in at least a portion thereof, and at least a portion of the washer enters the recess; wherein the recess includes at least a first region and a second region, and wherein the recess is shallower in the second region than in the first region; and wherein, when the bone screw is inserted in the aperture of the implant member and the hole of the washer such that the thicker region of the bone screw is in the second region of the aperture, rotation of the washer causes movement of the first region of the washer from the first region of the recess to the second region of the recess such that the washer applies force to the bone screw to press the bone screw against the implant member and to fix the bone screw in orientation relative to the implant member.