bone anchor assembly includes a bone anchor, the receiving member for receiving a spinal fixation element that is coupled to the bone anchor, and a compression member disposed within the receiving member, the outer set screw and the inner set screw including a closing mechanism, the. Outside set screw, the compression member to deliver a distal direction force, to secure the bone anchor to the receiving member. Proximal surface of the compression member has a shape configured to limit the deformation of the compression member arm comprising a movement relative to one another of the compression member arm. The distal surface of the outer set screw has a shape complementary to the shape of the proximal surface of the compression member.骨アンカーアセンブリは、骨アンカーと、骨アンカーに連結される脊柱固定要素を受容するための受容部材と、受容部材内に配置される圧縮部材と、外側止めねじ及び内側止めねじを含む閉鎖機構と、を含む。外側止めねじは、圧縮部材に遠位方向力を送達して、骨アンカーを受容部材に対して固定する。圧縮部材の近位表面は、圧縮部材アームの互いに対する動きを含む圧縮部材アームの変形を制限するように構成された形状を有する。外側止めねじの遠位表面は、圧縮部材の近位表面の形状に相補的な形状を有する。
