A polyaxial bone anchoring device is provided including an anchoring element (1) having a shank (2) for anchoring in the bone and a head (3), the head having a spherical outer surface portion that includes a largest outer diameter (E) a receiving part (5) having a top end (5a) and a bottom end (5b), a channel (12) for receiving a rod therein, a bore (51) extending from the top end (5a) in the direction of the bottom end (5b), the bore having a bore axis (C) and a seat portion (52) for receiving the head at the bottom end, wherein at least two circumferentially distinct receses (55) are provided in the seat portion a pressure element (6) arranged within the bore on top of the head, the pressure element (6) having a head contacting surface portion (62, 63) that contacts the spherical outer surface portion of the head (3), wherein the head contacting surface portion includes at least two circumferentially distinct lugs (63) that extend along a region of the head that includes the largest outer diameter (E) in an axial direction wherein the head (3) is pivotable with respect to the receiving part (5) and can be fixed at an angle by exerting pressure via the pressure element (6) onto the head, and wherein the pressure element (6) is configured to have an undersize with respect to the head only in a region of said lugs (63), such that when the pressure element is placed onto the head, the head is clamped by the friction between the spherical outer surface portion and the lugs and wherein the lugs are configured to extend at least partially into the recesses (55).本案提供一種多軸式骨骼固定裝置,包含:固定元件(1),具有固定於骨骼之幹部(2),和頭部(3),頭部有球形外表面部,含最大外徑(E);容納件(5),有頂端(5a)和底端(5b)、容納桿件之槽溝(12)、從頂端(5a)按底端(5b)方向延伸之腔孔(51),腔孔有腔孔軸線(C)和在底端容納頭部用之支座部(52),其中在支座部設有至少二沿周分別之凹部(55);壓力元件(6),配置在腔孔內,於頭部頂上,壓力元件(6)有頭部接觸表面部(62,63),與頭部(3)之球形外表面部接觸,其中頭部接觸表面部含有至少二沿周分別之凸耳(63),沿軸向含有最大外徑(E)的頭部區域延伸;其中頭部(3)可相對於容納件(5)樞動,並可經壓力元件(6)施壓於頭部,而固定角度,且其中壓力元件(6)構成只在該凸耳(63)區域內較頭部小,當壓力元件置於頭部上時,頭部即被球形外表面部和凸耳間之摩擦夾持,又其中凸耳構成至少部份延伸入凹部(55)內。3‧‧‧頭部4‧
