Patent ID: 8784455

Claim:
A bone anchoring device comprising: an anchoring element comprising a shank to be anchored in a bone or a vertebra; a receiving part connectable to the shank, the receiving part comprising: a first end opposite to the shank and a second end facing the shank, when connected to the shank; a longitudinal axis passing through the two ends; an outer surface at the first end, a side surface extending between the two ends, and an edge region between and inclined relative to the outer surface and the side surface; 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 each including respective portions of the outer surface, the side surface, and the edge region; 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, the first locking member being provided with an external thread on at least a portion thereof which cooperates with the internal thread provided on said legs to connect the first locking member to the receiving part, 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 a perimeter of at least a part of an outer surface of the first locking member projecting above the first end of the receiving part when connected to the receiving part, the structure being engageable with a tool in a form-fit manner, and wherein said engagement structure is larger than the inner diameter of the internal thread of the receiving part and is equal to or smaller than an inner dimension of the edge region of the receiving part.