Patent ID: 8343191

Claim:
A bone anchoring device comprising: an anchoring element comprising a shank to be anchored in a bone or a vertebra; a receiving part connected to the shank, the receiving part comprising; a first end opposite to the shank and a second end facing the shank; a longitudinal axis passing through the two ends; a bore 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 for receiving a rod, the recess forming two free legs extending in the direction of the first end, the legs being provided with an internal thread; and a locking device for securing the rod in the receiving part, said locking device comprising: a first locking member having a first end and a second end which is provided with an external thread on at least a portion thereof which cooperates with the internal thread provided on said legs, a coaxial bore passing entirely through the first locking member, and an internal thread provided in at least a portion of said bore; a second locking member, the second locking member having an outer surface with an external thread in at least a portion thereof which cooperates with the internal thread provided at said bore of the first locking member; and a non-cylindrical engagement structure provided at the circumference of at least a part of the outer surface of the first locking member projecting above the first end of the receiving part, the structure being engageable with a tool in a form-fit manner, wherein a maximum outer diameter of said first locking member in the region of said structure is larger than the inner diameter of the internal thread of the receiving part and wherein the maximum outer diameter of the engagement structure is smaller than the outer diameter of the receiving part in the region of said legs; wherein the first locking member has an annular recess adjacent to the first end and the second locking member has a section with an annular shoulder, wherein a largest outer diameter of the annular shoulder is larger than the outer diameter of the external thread of the second locking member, and wherein the largest outer diameter of the annular shoulder is slightly smaller than the inner diameter of the recess of the first locking member, so that the largest outer diameter of the annular shoulder can be accommodated in the recess.