A bone anchor is provided bone anchor comprising an anchor member (1) having a first end (11) and a second end (12) and an tubular section between the first end and the second end, a longitudinal axis (L) extending from the first end to the second end, and a bone engagement structure (16) for engaging the bone in at least a portion of the tubular section wherein the tubular section (13) is expandable in a radial direction by reducing a distance between the first end and the second end and wherein the anchor member (1) is made of a first material a core member (2, 2) having a first end (21) and a second end (22) and being insertable into the anchor member and connectable thereto, the core member (2, 2) being configured to cooperate with the anchor member (1) such that by actuating the core member with respect to the anchor member the tubular section (13) is expandable characterized in that the core member (2, 2) is made of a second material that is different from the first material.本案提供一種骨骼固定器,包括固定器構件(1),有第一端(11)和第二端(12),以及介於第一端和第二端間之管狀段,縱軸線(L)從第一端延伸到第二端;以及骨骼結合結構(16),可供把骨骼結合於管狀段之至少一部份;其中管狀段(13)可藉縮小第一端和第二端之距離,而按徑向擴張,又其中固定器構件(1)係由第一種材料製成;芯部構件(2,2),具有第一端(21)和第二端(22),可插入固定器構件內,與之連接,芯部構件(2,2)構成與固定器構件(1)合作,使得相對於固定器構件作動芯部構件,即可使管狀段(13)擴張;其特徵為,芯部構件(2,2)係與第一種材料不同之第二種材料製作。1‧‧‧固定器構件2‧‧‧芯部構件3‧‧‧頭部11‧‧‧固定器構件第一端12‧‧‧固定器構件第二端13‧‧‧管狀段15‧‧‧開縫16‧‧‧骨骼螺紋17‧‧‧凹部21‧‧‧芯部構件第一端22‧‧‧芯部構件第二端23‧‧‧桿狀中央部24‧‧‧陽螺紋部25‧‧‧圓筒形部26‧‧‧結合部35‧‧‧第一共軸腔孔38‧‧‧凸部L‧‧‧縱軸線
