A polyaxial bone anchoring system is provided including a first anchoring element (1) having a first shank (2) for anchoring in the bone or a vertebra and a first head (3), the head having a spherically-shaped outer surface portion (3a) and wherein the first bone anchoring element (1) comprises a sleeve-like insert piece (5, 5) encompassing a portion of the first head (3) and being configured to pivot in the accommodation space (11) of the receiving part (4) a second anchoring element (101) having a second shank (102) for anchoring in the bone or a vertebra and a second haed (103), a receiving part (4), the receiving part having a top end (4a) and a bottom end (4b), a central axis (C) extending through the top end and the bottom end, a transverse channel (9) for receiving a rod (100) and an accommodation space (11) for accommodating the head (3), the accommodation space (11) having a lower opening (12) at the bottom (4b), a pressure member (6), the pressure member being arranged at least partially in the accommodation space (11) and wherein the pressure member has a lower surface portion (61) that contacts the first head (3) or the second head (103) to exert pressure onto the first head (3) or the second head (103) wherein the first anchoring element (1) and the secnd bone anchoring element (101), respectively, are pivotable with respect to the receiving part (4) and can be locked at an angle by exerting pressure with the pressure member (6) onto the first head (3) or the second head (103) to lock the first head (3) or the second head (103) in the receiving part (4) and wherein the first head (3) with the sleeve-like insert piece (5, 5) and the second head (103) each are configured to be introduced into the accommodation space through the lower opening and wherein the first bone anchoring element and the second bone anchoring element are configured to be interchangeable.本案提供一種多軸式骨骼固定系統,包含第一固定元件(1),有固定於骨骼或椎骨用之第一軸部(2),和第一頭部(3),頭部有球形外表面部(3a)其中第一骨骼固定元件(1)包括套筒狀插件(5,5),包圍
