Polyaxial bone anchors with increased angulation

• US 20070118123A1
• Filed: 11/21/2006
• Published: 05/24/2007
• Est. Priority Date: 11/21/2005
• Status: Active Grant

• Current Assignee: Synthes USA LLC (Johnson & Johnson)
• Original Assignee: Synthes USA LLC (Johnson & Johnson)
• Inventors: Wolf, Boyd, Strausbaugh, William, Saidha, Sean
• Granted Patent: US 8,100,946 B2
• Time in Patent Office: Days
• US Class Current: 606/272
• CPC Class Codes: A61B 17/7032 Screws or hooks with U-shaped head or back through which longitudinal rods pass
• CPC Class Codes: A61B 17/7037 wherein pivoting is blocked when the rod is clamped
• CPC Class Codes: A61B 17/7038 to a different extent in different directions, e.g. within one plane only
• CPC Class Codes: A61B 17/7049 Connectors, not bearing on the vertebrae, for linking longitudinal elements together A61B17/7055, A61B17/7053, A61B17/7019 take precedence

Abstract

A polyaxial bone anchor has a locking element shaped and configured to allow an anchoring member (e.g., a screw or hook) to polyaxially rotate at large angles about a central axis of the bone anchor before compression locking the anchoring member within an anchor head.

Claims

1. A polyaxial bone anchor for attaching a rod to a bone comprising:

an anchor head comprising a longitudinal bore having a top and bottom opening, a generally U-shaped channel transverse to the longitudinal bore for receiving the rod, and a central axis extending through the hollow housing and bottom opening;

an anchor member for attaching to bone having a first portion and a second portion;

a locking member configured to be retained within the anchor head and to receive the first portion of the anchor member, the second portion of the anchor member extending through the bottom opening of the anchor head, the locking member allowing the anchor member to angulate at angles exceeding about 40 degrees from the central axis in all directions; and

a fastener removably mountable to the anchor head to close the top opening of the longitudinal bore and to lock the position of the rod in the U-shaped channel and the position of the anchor member.

2. The polyaxial bone anchor of claim 1 wherein an angle at which the anchor member can angulate from the central axis in at least one direction is about 50 degrees.

3. The polyaxial bone anchor of claim 1 wherein the angulation of the anchor member about the central axis forms a cone of about 100 degrees.

4. The polyaxial bone anchor of claim 1 wherein the locking member is operative to rotate within the anchor head prior to the fastener locking the positions of the rod and anchor member.

5. The polyaxial bone anchor of claim 1 wherein the locking member comprises a collet having an upper portion comprising resilient tabs for compressing against the first portion of the anchor member, the collet having a lower portion comprising at least two prongs that form a cutout to allow the anchor member to angulate there through.

6. The polyaxial bone anchor of claim 5 wherein the angle of the cutout measured from the central axis at the bottom of the collet to the top of the cutout is about 50 degrees.

7. The polyaxial bone anchor of claim 1 wherein:

the locking member comprises a lip extending around the perimeter of the locking member;

the anchor head has an interior groove in which the lip can be positioned; and

the locking member is capable of rotation within the anchor head with the lip positioned in the groove and prior to the fastener locking the positions of the rod and anchor member.

8. The polyaxial bone anchor of claim 1 wherein the exterior shape of the locking member is spherical and the locking member has an interior area sized and shaped to substantially match the size and shape of the first portion of the anchor member, the locking member having an interior centerpoint offset from the centerpoint of the exterior shape of the locking member.

9. The polyaxial bone anchor of claim 1 wherein the locking member is hollow and has a top end, a bottom end, and a spherically shaped exterior surface having a least one slot extending through the exterior surface from the bottom end.

10. The polyaxial bone anchor of claim 1 further comprising a hollow sleeve having a generally U-shaped channel for receiving the rod, the sleeve retained within the anchor head.

11. The polyaxial bone anchor of claim 10 wherein the sleeve has a bottom surface that engages a portion of the top of the locking member, the bottom surface having a contour that matches the engaged portion of the locking member top.

12. The polyaxial bone anchor of claim 11 wherein the bottom contoured surface of the sleeve is arcuate.

13. The polyaxial bone anchor of claim 11 wherein the bottom contoured surface of the sleeve is tapered upward and inward with respect to the sleeve.

14. The polyaxial bone anchor of claim 1 wherein the anchor head has an interior surface around the bottom opening that engages a portion of the exterior surface of the locking member and matches the contour thereof.

15. The polyaxial bone anchor of claim 1 wherein the anchor head has a tapered interior surface around the bottom opening that contacts a portion of the anchor member at full angulation.

16. The polyaxial bone anchor of claim 1 wherein the anchor member comprises a screw or hook.

17. The polyaxial bone anchor of claim 1 wherein the fastener is a locking cap comprising a locking ring and set screw.

18. The polyaxial bone anchor of claim 1 wherein the locking member surrounds at least a portion of the first portion of the anchor member, is received in a lower portion of the anchor head, and is rotatable about the central axis.

19. A polyaxial bone anchor for attaching a rod to a bone comprising:

an anchor head comprising a longitudinal bore having a top and bottom opening, a generally U-shaped channel transverse to the longitudinal bore for receiving the rod, and a central axis extending through the hollow housing and bottom opening;

an anchor member for attaching to bone having a first portion and a second portion;

a locking member configured to be retained within the anchor head and to receive the first portion of the anchor member, the second portion of the anchor member extending through the bottom opening of the anchor head, the locking member comprising a collet having an upper portion comprising resilient tabs for compressing against the first portion of the anchor member, the collet having a lower portion comprising at least two prongs that form a cutout to allow the anchor member to angulate there through; and

a fastener removably mountable to the anchor head to close the top opening of the longitudinal bore and to lock the position of the rod in the U-shaped channel and the position of the anchor member.

20. The polyaxial bone anchor of claim 19 wherein an angle at which the anchor member can angulate from the central axis in at least one direction exceeds 40 degrees.

21. The polyaxial bone anchor of claim 19 wherein the angulation of the anchor member about the central axis forms a cone of about 100 degrees.

22. The polyaxial bone anchor of claim 19 wherein the locking member is operative to rotate within the anchor head prior to the fastener locking the positions of the rod and anchor member.

23. The polyaxial bone anchor of claim 19 wherein the angle of the cutout measured from the central axis at the bottom of the collet to the top of the cutout is about 50 degrees.

24. The polyaxial bone anchor of claim 19 wherein:

the locking member comprises a lip extending around the perimeter of the locking member;

the anchor head has an interior groove in which the lip can be positioned; and

the locking member is capable of rotation within the anchor head with the lip positioned in the groove and prior to the fastener locking the positions of the rod and anchor member.

25. The polyaxial bone anchor of claim 19 further comprising a hollow sleeve having a generally U-shaped channel for receiving the rod, the sleeve retained within the anchor head.

26. The polyaxial bone anchor of claim 25 wherein the sleeve has a bottom surface that engages a portion of the top of the locking member, the bottom surface having a contour that matches the engaged portion of the locking member top.

27. The polyaxial bone anchor of claim 26 wherein the bottom contoured surface of the sleeve is arcuate.

28. The polyaxial bone anchor of claim 26 wherein the bottom contoured surface of the sleeve is tapered upward and inward with respect to the sleeve.

29. The polyaxial bone anchor of claim 19 wherein the anchor head has an interior surface around the bottom opening that engages a portion of the exterior surface of the locking member and matches the contour thereof.

30. The polyaxial bone anchor of claim 19 wherein the anchor head has a tapered interior surface around the bottom opening that contacts a portion of the anchor member at full angulation.

31. The polyaxial bone anchor of claim 19 wherein the anchor member comprises a screw or hook.

32. The polyaxial bone anchor of claim 19 wherein the fastener is a locking cap comprising a locking ring and set screw.

33. The polyaxial bone anchor of claim 19 wherein the lower portion of the collet comprises three prongs forming three cutouts to allow the anchor member to angulate through any one of the three cutouts.

34. A polyaxial bone anchor for attaching a rod to a bone comprising:

an anchor head comprising a longitudinal bore having a top and bottom opening, a generally U-shaped channel transverse to the longitudinal bore for receiving the rod, and a central axis extending through the hollow housing and bottom opening;

an anchor member for attaching to bone having a first portion and a second portion;

a locking member configured to be retained within the anchor head and to receive the first portion of the anchor member, the second portion of the anchor member extending through the bottom opening of the anchor head, the locking member having a spherical exterior shape and having an interior area sized and shaped to receive the first portion of the anchor member, the locking member having an interior centerpoint offset from the centerpoint of the exterior shape of the locking member; and

a fastener removably mountable to the anchor head to close the top opening of the longitudinal bore and to lock the position of the rod in the U-shaped channel and the position of the anchor member.

35. The polyaxial bone anchor of claim 34 wherein an angle at which the anchor member can angulate from the central axis in at least one direction exceeds 40 degrees.

36. The polyaxial bone anchor of claim 34 wherein the angulation of the anchor member about the central axis forms a cone of about 100 degrees.

37. The polyaxial bone anchor of claim 34 wherein the locking member is operative to rotate within the anchor head prior to the fastener locking the positions of the rod and anchor member.

38. The polyaxial bone anchor of claim 34 wherein the locking member is hollow and has a top end, a bottom end, and a spherically shaped exterior surface having a least one slot extending through the exterior surface from the bottom end.

39. The polyaxial bone anchor of claim 34 further comprising a hollow sleeve having a generally U-shaped channel for receiving the rod, the sleeve retained within the anchor head.

40. The polyaxial bone anchor of claim 39 wherein the sleeve has a bottom surface that engages a portion of the top of the locking member, the bottom surface having a contour that matches the engaged portion of the locking member top.

41. The polyaxial bone anchor of claim 40 wherein the bottom contoured surface of the sleeve is arcuate.

42. The polyaxial bone anchor of claim 40 wherein the bottom contoured surface of the sleeve is tapered upward and inward with respect to the sleeve.

43. The polyaxial bone anchor of claim 34 wherein the anchor head has an interior surface around the bottom opening that engages a portion of the exterior surface of the locking member and matches the contour thereof.

44. The polyaxial bone anchor of claim 34 wherein the anchor head has a tapered interior surface around the bottom opening that contacts a portion of the anchor member at full angulation.

45. The polyaxial bone anchor of claim 34 wherein the anchor member comprises a screw or hook.

46. The polyaxial bone anchor of claim 34 wherein the fastener is a locking cap comprising a locking ring and set screw.

47. The polyaxial bone anchor of claim 34 wherein the locking member surrounds at least a portion of the first portion of the anchor member, is received in a lower portion of the anchor head, and is rotatable about the central axis.