A bone anchoring device is provided including: an anchoring element (1) comprising a shank (2) to be anchored in a bone or a vertebra, a receiving part (4) connected to the shank the receiving part comprising a first end (5) opposite to the shank and a second end (6) facing the shank, a longitudinal axis (L) passing through the two ends, a bore (7) coaxial with the longitudinal axis extending from the first end through at least a portion of the receiving part and a substantially U-shaped recess (10) for receiving a rod (20), the recess forming two free legs (11, 12) extending in the direction of the first end, the legs being provided with an internal thread (13), a locking device (30 50) for securing the rod in the receiving part said locking device comprising: an external thread (35 55) cooperating with the internal thread (13), and an engagement structure (38) provided at the circumference of least a part of the outer surface projecting above the first end (5) of the receiving part, the structure being engageable with a tool in a form-fit manner and wherein a maximum outer diameter of said first locking member in the region of said structure (38) is larger than the inner diameter of the internal thread (13) of the receiving part.(Fig. 1)本案提供一種骨骼固定裝置,包含:固定元件(1),包括幹部(2),要固定於骨骼或椎骨;容納件(4),連接於幹部,容納件包括在幹部對立的第一端(5)和朝向幹部的第二端(6),通過二端之縱向軸線(L),與縱向軸線同軸從第一端延伸通過容納件至少一部份之腔孔(7),和容納桿(20)用之實質上U形凹部(10),凹部形成二自由股部(11,12),按第一端方向延伸,股部設有陰螺紋(13);鎖定裝置(30;50),把桿保固於容納件內,該鎖定裝置包括:陽螺紋(35;55),與陰螺紋(13)嚙合;和結合結構(38),設在外表面至少一部份的周緣,突出於容納件第一端(5)上方,結構可以型套方式與工具結合,而其中該第一鎖定構件在該結構(38)之區域內之最大外徑,比容納件的陰螺紋(13)內徑為大。1‧‧‧螺釘元件2‧‧‧幹部3‧‧‧頭部3a‧‧‧凹部4‧‧‧容納件5‧‧‧容納件第一端6‧‧‧容納件第二端10‧‧‧U形凹部11,12‧‧‧自由股部13‧‧‧陰螺紋14‧‧‧加壓元件16‧‧‧U形凹部17,18‧‧‧自由股部19‧‧‧腔孔20‧‧‧桿21‧‧‧凹部30‧‧‧鎖定裝置31‧‧‧第一鎖定構件32‧‧‧第二鎖定構件L‧‧‧縱向軸線
