A polyaxial bone anchoring device is provided including: a bone anchoring element (1) having a shank (2) for anchoring in a bone or a vertebra and a head (3)； a receiving part (4, 4') for receiving a rod (5) to be connected to the bone anchoring element (1), the receiving part having a first end (4a) and an opposite second end (4b), a central axis (C) passing through the two ends, a channel for receiving the rod (5), a coaxial first bore (9) at the first end (4a) and a coaxial second bore (12) at the second end, that is in communication with the first bore (9)； an insert piece (6, 6', 6") that can be assembled and mounted to the receiving part (4, 4'), the insert piece (6, 6', 6") having a seat (18) for the head of the bone anchoring element (1) to permit pivoting of the head relative to the seat； where the insert piece (6, 6', 6") projects out of the second bore (12) and has a bounding edge at an end (6b) opposite to the first bore (9) with an opening (17) that is smaller than that of the head to prevent passage of the head therethrough； and wherein the bounding edge is configured to permit the bone anchoring element (1) to pivot at a larger angle at a first location of the bounding edge than at another location of the bounding edge relative to the central axis (C)； and wherein the insert piece (6, 6', 6") is rotatable with respect to the receiving part and wherein the receiving part (4, 4') has a first flat surface portion (13) that is substantially perpendicular to the central axis (C) for supporting the insert piece (6, 6', 6") and the insert piece (6, 6', 6") has a corresponding second flat surface portion (15a) facing the first flat surface portion (13).本案提供一種多軸式骨骼固定裝置，包含：骨骼固定元件(1)，有固定於骨骼或椎骨所用軸部(2)，和頭部(3)；容納件(4,4')，供容納要連接於骨骼固定元件(1)之桿件(5)，容納件有第一端(4a)和對立之第二端(4b)，通過兩端之中心軸線(C)，容納桿件(5)用之槽溝，在第一端(4a)之共軸第一腔孔(9)，和在第二端之共軸第二腔孔(12)，與第一腔孔(9)相通；插件(6,6',6")，可組合安裝於容納件(4,4')內，插件(6,6',6")有骨骼固定元件(1)的頭部底座(18)，使頭部可相對於底座樞動；其中插件(6,6',6")凸出於第二腔孔(12)外，在第一腔孔(9)對立之末端(6b)有限制邊緣，其開口(17)比
