Bone anchoring device

A modular bone anchoring system 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;
• a pressure element arranged in the receiving part between the head and the locking device for exerting pressure onto said head to lock the head in the receiving part, wherein said pressure element has a substantially U-shaped recess for receiving at least a part of the rod, the depth of the recess being larger than the diameter of the rod;
• a two-part locking device for securing the rod in the receiving part, said two-part locking device comprising an engagement structure provided at the circumference of at least a part of the outer surface of the two-part locking device and configured to project above the first end of the receiving part, the structure being engageable with a tool in a form-fit manner and wherein a maximum outer diameter of said two-part locking device in the region of said structure is larger than the inner diameter of the internal thread of the receiving part;
• and
• a single-part locking device for securing the rod in the receiving part, said single-part locking device comprising an engagement structure provided at the circumference of at least a part of the outer surface of the single-part locking device and configured to project above the first end of the receiving part, wherein a maximum outer diameter of said single-part locking device in the region of said structure is larger than the inner diameter of the internal thread of the receiving part.

A method of attaching a bone anchoring device to a bone, the bone anchoring device comprising an anchoring element having 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, the bone anchoring device further comprising 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 an 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 and 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, the method comprising:

• anchoring the shank into a bone;
• inserting a rod in the U-shaped recess of the receiving part;
• fixing the shank of the anchoring element relative to the receiving part, the fixing comprising screwing the first locking member to the internal threads of the free legs, and tightening the first locking member by the tool engaging the engagement structure provided at the circumference of the at least a part of the outer surface of the first locking member;
• fixing the rod in the U-shaped recess of the receiving part by screwing the second locking member to the internal threads of the first locking member and tightening the second locking member over the rod.