Variable Stiffness Support Members

• US 20080177388A1
• Filed: 01/18/2007
• Published: 07/24/2008
• Est. Priority Date: 01/18/2007
• Status: Active Grant

• Current Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Original Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Inventors: Allard, Randall, Veldman, Michael S., Patterson, Christopher M.
• Granted Patent: US 7,875,059 B2
• Time in Patent Office: Days
• US Class Current: 623/17.16
• CPC Class Codes: A61B 17/7004 with a cross-section which varies along its length A61B17/7019 takes precedence
• CPC Class Codes: A61B 17/7031 made wholly or partly of flexible material
• CPC Class Codes: A61B 17/705 for linking adjacent ends of longitudinal elements
• CPC Class Codes: A61B 2017/00526 Methods of manufacturing

Abstract

Spinal support members having varying stiffnesses are disclosed. In one embodiment, an elongated spinal prosthetic includes a pair of curved elongated portions. The portions are formed of materials having different stiffness characteristics such that the stiffness of the prosthetic varies along its length. In another embodiment, an elongated spinal implant includes a pair of threadedly engaged elongated sections. The first section is formed of a first material having a first rigidity. The second section has an inner portion formed of the first material and an outer portion formed of a second material. The second material is less rigid than the first material. In another embodiment, a modular spinal rod is provided. The modular spinal rod includes a pair of connectable rod portions with different stiffness characteristics. In yet another embodiment, a kit for a modular spinal rod includes a plurality of connectable modular rod portions having different stiffness characteristics.

Claims

1. An elongated spinal prosthetic comprising:

a first elongated portion having a male connection mechanism extending from one end, the first elongated portion having a first outer surface formed of a first material having a first rigidity; and

a second elongated portion having a female connection mechanism for receiving the male connection mechanism of the first elongated portion to connect the first and second elongated portions, the second elongated portion having a second outer surface formed of a second material different from the first material, the second material having a second rigidity less than the first rigidity of the first material.

2. The elongated spinal prosthetic of claim 1 wherein a majority of the first elongated portion is formed of the first material and wherein a majority of the second elongated portion is formed of the second material.

3. The elongated spinal prosthetic of claim 2 wherein the first material is a polymer and the second material is a polymer.

4. The elongated spinal prosthetic of claim 3 wherein the first material is a metal and the second material is a polymer.

5. The elongated spinal prosthetic of claim 4 wherein the first material is selected from the group of metals consisting of titanium alloys, cobalt-chromium alloys, nickel titanium alloys, and stainless steel alloys, and the second material is PEEK.

6. The elongated spinal prosthetic of claim 4 wherein a thickness of the male connection mechanism is varied along its length.

7. The elongated spinal prosthetic of claim 6 wherein the thickness of the male connection mechanism is tapered along its length.

8. The elongated spinal prosthetic of claim 7 wherein the male connection mechanism extends within the second elongated portion along a majority of the length of the second elongated portion.

9. The elongated spinal prosthetic of claim 6 wherein the thickness of male connection mechanism decreases and increases along its length.

10. The elongated spinal prosthetic of claim 4 wherein the first elongated portion is curved along its length.

11. The elongated spinal prosthetic of claim 10 wherein the second elongated portion is curved along its length.

12. The elongated spinal prosthetic of claim 11 wherein the radii of curvature for the first and second elongated portions are substantially equal such that the elongated spinal prosthetic has a substantially continuous radius of curvature along its length.

13. The elongated spinal prosthetic of claim 11 wherein the radius of curvature for the first elongated portion is different from the radius of curvature for the second elongated portion such that the elongated spinal prosthetic has a varying radius of curvature along its length.

14. The elongated spinal prosthetic of claim 13 wherein the radius of curvature for the first elongated portion is curved in a direction substantially opposite the radius of curvature for the second elongated portion when the first and second portions are connected.

15. The elongated spinal prosthetic of claim 4 further comprising a sleeve member positioned around the first and second elongated portions adjacent a junction between the first and second outer surfaces.

16. A spinal support system comprising:

a support member comprising;

a first elongated section, the first section formed of a first material having a first rigidity;

a second elongated section engaged with the first section, the second section having an inner portion formed of the first material and an outer portion formed of a second material different from the first material, the second material having a second rigidity less than the first rigidity;

a first fixation member for connecting the first elongated section to a first vertebra; and

a second fixation member for connecting the second elongated section to a second vertebra.

17. The spinal support system of claim 16 wherein the inner portion extends along a majority of the length of the second section.

18. The spinal support system of claim 17 wherein the thickness of the inner portion varies along its length.

19. The spinal support system of claim 18 wherein the thickness of the inner portion is tapered.

20. The spinal support system of claim 18 wherein the thickness of the inner portion is stepped.

21. The spinal support system of claim 16 further comprising a sleeve member positioned around the first and second elongated sections adjacent a junction between the first and second elongated sections.

22. The spinal support system of claim 21 wherein the sleeve member comprises a clamp.

23. The spinal support system of claim 16 wherein the inner portion is a separate piece adapted to mate with the outer portion to form the second section.

24. The spinal support system of claim 23 wherein the first section includes an opening to allow the inner portion of the second section to pass therethrough when assembling the support member.

25. The spinal support system of claim 24 wherein the inner portion extends within at least a portion of the opening of the first section when mated with the outer portion.

26. The spinal support system of claim 25 further comprising an end cap adapted to engage the opening of the first section.

27. A modular spinal rod comprising:

a first rod portion having a first connection mechanism extending from one end, the first rod portion formed of a first material having a first rigidity; and

a second rod portion having a second connection mechanism for selective engagement with the first connection mechanism of the first rod portion to securely engage the first and second rod portions, the second rod portion formed of a second material different from the first material, the second material having a second rigidity less than the first rigidity of the first material.

28. The modular spinal rod of claim 27 further comprising a third rod portion having a third connection mechanism extending from one end, the third rod portion formed of a third material, the third material having a third rigidity less than the second rigidity of the second material;

wherein the second rod portion includes a fourth connection mechanism at the end opposite the second connection mechanism; and

wherein the third connection mechanism is adapted to selectively engage the fourth connection mechanism to securely engage the third rod portion to the second rod portion.

29. The modular spinal rod of claim 27 further comprising an axial sleeve member positioned adjacent a transition between the first rod portion and the second rod portion.

30. The modular spinal rod of claim 27 further comprising an end cap adapted to engage at least one end of at least one of the first and second rod portions.

31. The modular spinal rod of claim 27 further comprising a stiffening member positioned at least partially within the second rod portion, the stiffening member formed of a third material. the third material having a third rigidity greater than the second rigidity of the second material.

32. The modular spinal rod of claim 31 wherein the third material is the same as the first material.

33. A kit for a modular spinal rod, the kit comprising:

a plurality of modular rod portions, each of the plurality of rod portions connectable to at least one of the other rod portions to form a spinal rod;

wherein a majority of the plurality of rod portions each have different stiffness characteristics such that rod portions with different stiffness characteristics may be connected to form a spinal rod with varying degrees of stiffness along its length.

34. The kit of claim 33 wherein at least two of the plurality of modular rod portions have substantially similar stiffness characteristics.

35. The kit of claim 34 further comprising a plurality of stiffening members for insertion within an opening of at least one of the plurality of rod portions, wherein each of the stiffening members has a different stiffness characteristic.

36. The kit of claim 35 further comprising at least one sleeve member adapted to be positioned around the spinal rod adjacent a transition between connected rod portions.

37. The kit of claim 36 further comprising at least two end caps, each end cap adapted to be positioned at an end of the spinal rod.

38. The kit of claim 33 wherein the rod portions with different stiffness characteristics are connectable via a snap connection.

39. A spinal support member with a substantially constant periphery along its length, the support member comprising:

a first portion extending along a majority of the length of the support member, the first portion having a first section with a first periphery and a second section with a second periphery, the second periphery being smaller than the first periphery; and

a second portion extending over at least the second section of the first portion, the second portion having third periphery substantially similar to the first periphery of the first section of the first portion;

wherein the first portion is formed of a first material and the second portion is formed of a second material different than the first material.

40. The spinal support member of claim 39 wherein the first section of the first portion extends along approximately half of the length of the support member.

41. The spinal support member of claim 40 wherein the second portion extends over the second section of the first portion along approximately half of the length of the support member.

42. The spinal support member of claim 41 wherein the second portion is molded over the first portion.

43. The spinal support member of claim 42 wherein at least one of the first and second portions is curved along its length.

44. The spinal support member of claim 42 wherein the first portion is formed by injection molding.

45. The spinal support member of claim 44 wherein the first material is a polymer and the second material is a polymer.

46. The spinal support member of claim 42 wherein the first material is a metal and the second material is a polymer.