An instrument for inserting a bone anchoring element into a bone is provided, the instrument including a shaft (2) having an end portion (23, 23’) for engaging the bone anchoring element and for transferring torque to the bone anchoring element (1, 1’) and a longitudinal axis defining an axis of rotation (R)； a cutting member (4, 4’) connected to the shaft (2) with cutting portions (45) that are configured to cut bone material； wherein the cutting member (4, 4’) has an outer diameter (D) defined by the cutting portions (45) that is substantially the same or larger than an outer diameter (dd) of a receiving part (500) of the polyaxial bone anchor in a region at a bottom end (500b) of the receiving part.一種器具，用於插入一骨骼固定元件至骨骼。器具包括一軸(2)，其具有一端部(23、23’)以接合該骨骼固定元件與傳送扭力至該骨骼固定元件(1、1’)以及一定義一旋轉軸(R)的縱向軸；一切割元件(4、4’)連接至軸(2)且具有用於切割骨骼材料的切割部(45)；其中該切割元件(4、4’)具有一由切割部(45)定義的外直徑(D)，其實質上相同或大於該多軸式骨骼固定器的一接受部(500)在其一底端(500b)的一區域的一外直徑。
