Bone anchoring device
A bone anchoring device includes a shaft for anchoring in a bone and a head, the shaft including a first section having a plurality of barb elements, the barb elements being elastically deformable relative to the body of the shaft, and a second section including a bone thread for engagement with the bone. The first section is located near the tip of the shaft and allows insertion by pushing whereas the second section provides enhanced resistance against pull-out.
1. A bone anchoring device comprising:
a head portion; and
a shaft for anchoring in a bone, the shaft comprising:
a first section comprising a plurality of barb elements, the barb elements being elastically deformable relative to the shaft, and
a second section comprising a bone thread for engagement with the bone;
wherein the shaft has a free end opposite to the head portion and the first section is provided between the second section and the free end;
wherein the barb elements are arranged on at least one helical line around the shaft; and
wherein a pitch of the helical line is the same as a pitch of the bone thread of the second section.
2. The bone anchoring device of claim 1 , wherein the second section is arranged adjacent to the head portion.
3. The bone anchoring device of claim 1 , wherein the barb elements form at least two turns of the helical line.
4. The bone anchoring device of claim 1 , wherein the first section is detachably mounted to the second section.
5. The bone anchoring device of claim 1 , wherein the first section is provided on a tubular body.
6. The bone anchoring device of claim 5 , wherein the barb elements are cut out of a wall of the tubular body.
7. The bone anchoring device of claim 1 , wherein the head portion comprises a recess for receiving a rod.
8. The bone anchoring device of claim 1 , wherein the head and the shaft are fixedly connected.
9. The bone anchoring device of claim 1 , wherein the head and the shaft are connected such as to allow pivoting of the shaft relative to the head.
10. The bone anchoring device of claim 9 , comprising means for locking the pivoting movement of the shaft relative to the head.
11. The bone anchoring device of claim 1 , wherein the barb elements are made of a shape-memory material.
12. The bone anchoring device of claim 11 , wherein the barb elements comprise nitinol.
13. The bone anchoring device of claim 1 , wherein free ends of the barb elements face towards the head portion.
14. The bone anchoring device of claim 1 , wherein the barb elements are arranged to prevent extraction without rotation of the bone anchoring device.
15. The bone anchoring device of claim 1 , wherein the head and the shaft are separate parts.
16. A bone anchoring device comprising:
a head portion; and
a shaft for anchoring in a bone, the shaft comprising:
a first section comprising a plurality of barb elements, the barb elements being elastically deformable relative to the shaft, and
a second section comprising a bone thread for engagement with the bone;
wherein the shaft has a free end opposite to the head portion and the first section is provided between the second section and the free end, and
wherein the length of the first section is at least approximately twice the length of the second section.
17. A bone anchoring comprising:
a head portion; and
a shaft for anchoring in a bone, the shaft comprising:
a first section comprising a plurality of barb elements arranged on at least one helical line around the shaft, the barb elements being elastically deformable relative to the shaft; and
a second section comprising a bone thread for engagement with the bone; and
wherein a pitch of the helical line is the same as a pitch of the bone thread of the second section.