Polyaxial bone anchoring device

Patent metadata

Field	Value
Publication number	US-9345516-B2
Application number	US-201213588859-A
Country	US
Kind code	B2
Filing date	Aug 17, 2012
Priority date	Aug 18, 2011
Publication date	May 24, 2016
Grant date	May 24, 2016

Abstract

A polyaxial bone anchoring device includes an anchoring element having a shaft and a head, a receiving part having a first end and a second end, a bore extending from the first end towards the second end, a seat for receiving the head, and at least one threaded through hole transverse to the bore, a pressure element to exert pressure onto the head, such that the head is pivotable and can be locked at an angle relative to the receiving part, the pressure element having at least one hole configured to at least partially align with the through hole, and at least one set screw threadable into the through hole to engage the pressure element at the hole such that a force is exerted by the pressure element onto the head that maintains the head at an adjustable angular position relative to the receiving part by friction.

First claim

What is claimed is:

1. A polyaxial bone anchoring device comprising:
an anchoring element having a shaft for anchoring in a bone and a head;
a receiving part having a first end and a second end, a channel for receiving a rod therein, a bore extending from the first end towards the second end, a seat for receiving the head, and at least one threaded through hole transverse to the bore;
a pressure element configured to be arranged in the bore and to exert pressure onto the head when the head and the pressure element are in the receiving part, such that the head is pivotable with respect to the receiving part and can be locked at an angle relative to the receiving part by the pressure element, the pressure element having at least one hole configured to at least partially align with the through hole of the receiving part; and
at least one set screw having a tapered portion and being configured to be inserted into the through hole of the receiving part;
wherein when the head and the pressure element are in the receiving part, the set screw is threadable into the through hole to a first position where the set screw engages the pressure element at the hole such that a first force is exerted by the pressure element onto the head that maintains the head at an adjustable angular position relative to the receiving part by friction prior to locking the head relative to the receiving part;
wherein the set screw is threadable into the through hole past the first position to a second position where the set screw engages the pressure element at the hole such that a second force greater than the first force is exerted by the pressure element onto the head; and
wherein a surface of the pressure element that engages the set screw in the first position is tapered with respect to a central axis of the receiving part, and the tapered portion of the set screw is configured to engage the pressure element at the hole.

2. The polyaxial bone anchoring device according to claim 1 , wherein when the head and the pressure element are in the receiving part and the set screw is in the first position, an edge of the pressure element defining the hole is in contact with the set screw.

3. The polyaxial bone anchoring device according to claim 2 , wherein when the set screw is in the first position, a central axis of the set screw and a central axis of the hole are offset along an axial direction of the receiving part, such that the set screw exerts a pressure on the pressure element by engaging the edge defining the hole to generate a defined friction force between the head and the pressure element.

4. The polyaxial bone anchoring device according to claim 1 ,
wherein the surface of the pressure element that engages the set screw forms a first angle with the central axis of the receiving part, and wherein an angle of the tapered portion of the set screw corresponds to the first angle.

5. The polyaxial bone anchoring device according to claim 4 , wherein the first angle is between 30° and 60°.

6. The polyaxial bone anchoring device according to claim 1 , wherein the hole of the pressure element is cylindrical.

7. The polyaxial bone anchoring device according to claim 1 , wherein a cross-section of the hole of the pressure element is trapezoidal.

8. The polyaxial bone anchoring device according to claim 1 , wherein at least two through holes are provided on the receiving part and at least two holes are provided on the pressure element.

9. The polyaxial bone anchoring device according to claim 8 , wherein the through holes are offset by 180° in a circumferential direction of the receiving part, and wherein the holes are offset by 180° in a circumferential direction of the pressure element.

10. The polyaxial bone anchoring device according to claim 1 , wherein the pressure element has a first end and a second end, a coaxial bore, a spherical segment-shaped recess at the second end, and a cylindrical or U-shaped recess at the first end, wherein the cylindrical or U-shaped recess is configured to be aligned with a recess of the receiving part when the pressure element is in the receiving part.

11. The polyaxial bone anchoring device according to claim 1 , wherein the receiving part comprises an asymmetric end portion for allowing a greater pivot angle of the anchoring element to one side when the head is in the receiving part.

12. The polyaxial bone anchoring device according to claim 1 , wherein the set screw comprises a threadless portion for engaging the hole of the pressure element.

13. The polyaxial bone anchoring device according to claim 12 , wherein the threadless portion of the set screw is tapered.

14. The polyaxial bone anchoring device according to claim 1 , wherein the set screw is configured to be advanced in the through hole of the receiving part to the second position to lock the angular position of the head relative to the receiving part.

15. A method of coupling a rod to a bone or vertebra via a polyaxial bone anchoring device, the polyaxial bone anchoring device comprising an anchoring element having a shaft for anchoring in a bone and a head, a receiving part having a first end and a second end, a channel for receiving the rod therein, a bore extending from the first end towards the second end, a seat for receiving the head, and at least one threaded through hole transverse to the bore, a pressure element configured to be arranged in the bore and to exert pressure onto the head when the head and the pressure element are in the receiving part, such that the head is pivotable with respect to the receiving part and can be locked at an angle relative to the receiving part by the pressure element, the pressure element having at least one hole configured to at least partially align with the through hole of the receiving part, and at least one set screw configured to be inserted into the through hole of the receiving part, the method comprising:
threading the set screw in the through hole of the receiving part to a first position where the set screw is fixedly retained in the receiving part and engages an inserted pressure element at the hole, such that a first force is exerted by the pressure element onto the head of a connected anchoring element that maintains the head at an adjustable angular position relative to the receiving part by friction;
further threading the set screw into the through hole past the first position to a second position where the set screw engages the pressure element at the hole such that a second force greater than the first force is exerted by the pressure element onto the head;
inserting the anchoring element into a bone or vertebra;
adjusting the angular position of the receiving part relative to the anchoring element;
inserting a rod into the channel of the receiving part and the channel of the pressure element; and
locking the angular position of the receiving part relative to the anchoring element and a position of the rod relative to the receiving part.

16. The method of claim 15 , further comprising:
connecting the anchoring element to the receiving part by positioning the head in the seat;
inserting the pressure element into the bore; and
inserting the set screw into the through hole of the receiving part.

17. The method of claim 15 , wherein the bone anchoring device further comprises a fixation element, the method further comprising advancing the fixation element into the channel, such that the fixation element exerts pressure on the rod, the rod exerts pressure on the pressure element, and the pressure element exerts pressure onto the head of the anchoring e

Assignees

• Biedermann Timo
• Biedermann Lutz
• Biedermann Technologies Gmbh

Inventors

• Biedermann Timo
• Biedermann Lutz

Classifications

• A61B17/8605

  Heads, i.e. proximal ends projecting from bone · CPC title

• A61B17/70 Primary

  Spinal positioners or stabilisers, e.g. stabilisers comprising fluid filler in an implant · CPC title

• A61B17/7035 Primary

  Screws or hooks, wherein a rod-clamping part and a bone-anchoring part can pivot relative to each other · CPC title

• A61B17/7032

  Screws or hooks with U-shaped head or back through which longitudinal rods pass · CPC title

• A61B17/725

  with locking pins or screws of special form · CPC title