Implants formed of shape memory polymeric material for spinal fixation

• US 20050033295A1
• Filed: 08/08/2003
• Published: 02/10/2005
• Est. Priority Date: 08/08/2003
• Status: Active Grant

• Current Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Original Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Inventors: Wisnewski, Paul
• Granted Patent: US 7,794,476 B2
• Time in Patent Office: Days
• US Class Current: 606/250
• CPC Class Codes: A61B 17/7001 Screws or hooks combined with longitudinal elements which do not contact vertebrae A61B17/7058 takes precedence
• CPC Class Codes: A61B 17/7011 Longitudinal element being non-straight, e.g. curved, angled or branched adjustable length longitudinal elements A61B17/7014; A61B17/7019 takes precedence, e.g. coil springs
• CPC Class Codes: A61B 17/7032 Screws or hooks with U-shaped head or back through which longitudinal rods pass
• CPC Class Codes: A61B 17/7044 also having plates, staples or washers bearing on the vertebrae
• 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
• CPC Class Codes: A61B 17/7053 with parts attached to bones or to each other by flexible wires, straps, sutures or cables
• CPC Class Codes: A61B 17/842 Flexible wires, bands or straps A61B17/72, A61B17/82, A61B17/86 take precedence
• CPC Class Codes: A61B 2017/00867 shape memory effect for prostheses A61F2210/0014
• CPC Class Codes: A61B 2017/00871 polymeric
• CPC Class Codes: Y10T 403/21 Utilizing thermal characteristic, e.g. , expansion or contraction, etc.

Abstract

This invention relates to a orthopedic implant that comprises a shape memory polymeric material. The orthopedic implant can be fabricated or molded in a desired configuration selected to provide support or tension to bony structures. Examples of implantable devices include spinal rods, bone plates, and bone fixation cords. The orthopedic implant can be deformed to a second configuration different from the first configuration either prior to implantation or after implantation. When desired, the shape memory polymeric material can be induced to revert to it original molded configuration. This can compress the attached bony structure and/or promote arthrodesis.

Claims

1. A system for treating a spinal defect said system comprising:

a rod member including an elongate body provided in a first configuration sufficient to extend from a first vertebra to a second vertebra, said elongate body comprising a shape memory polymeric material;

a first fixation device connected to the rod member; and

a second fixation device connected to the rod member spaced axially from the first fixation device, whereby the elongate body upon absorption of thermal energy deforms to a second configuration different from the first configuration.

2. The device of claim 1 wherein the elongate body defines a substantially straight rod.

3. The device of claim 1 wherein the elongate body is bent to approximate the natural curvature of a portion of the spinal column.

4. The system of claim 1 wherein the elongate body in the first configuration has a length is sufficient to extend across three or more vertebrae.

5. The system of claim 1 wherein the elongate body in first configuration has a first length and wherein the elongate body in the second configuration has a second length shorter than the first length.

6. The system of claim 1 wherein the elongate body in first configuration has a first length and wherein the elongate body in the second configuration has a second length longer than the first length.

7. The system of claim 1 wherein the elongate body in the first configuration is bent.

8. The system of claim 7 wherein the elongate body in the second configuration is straight.

9. The system of claim 1 wherein the elongate body in the second configuration is bent.

10. The system of claim 9 wherein the elongate body in the first configuration is straight.

11. The system of claim 1 wherein the shape memory polymeric material is formed from a polymer derived from the monomeric repeating units selected from the group consisting of:

l, d, or d/l lactide;

glycolide;

ethers;

ethylene, propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, styrene, norbornene;

butadiene;

acrylate, methacrylate, methyl methacrylate;

caprolactone; and

mixtures of these monomeric repeating units.

12. The system of claim 1 wherein the shape memory polymeric material is non-biodegradable.

13. The system of claim 1 wherein the elongate body comprises a first end secured to a first vertebral body and a second end secured to an adjacent second vertebral body.

14. The system of claim 1 wherein the spinal rod member has a strength of greater than about 900 K Pa determined at a temperature lower than the deformation temperature of the shape memory polymeric material.

15. The system of claim 1 comprising a connector comprising:

a collar sized to at least partially encircle the elongate rod; and

body having a recess therein to receive the collar and a portion of the spinal rod member encircled by the collar.

16. The system of claim 15 wherein the collar is formed a shape memory polymeric material.

17. The system of claim 1 comprising a flexible cord comprising a shape memory polymeric material.

18. The system of claim 17 wherein the flexible cord is provided in a first length sufficient to encircle a spinous process of a vertebral body.

19. The system of claim 18 wherein the first length is greater than about 100 mm.

20. The system of claim 1 comprising a second rod member.

21. The system of claim 20 wherein the rod member and the second rod member have the same length.

22. The system of claim 20 wherein the rod member and the second rod member are interconnected with a lateral connector.

23. The system of claim 20 wherein the rod member and the second rod member are positioned substantially parallel to each other.

24. The system of claim 1 wherein the fixation device comprises a bone screw.

25. The system of claim 24 wherein the fixation device comprises a head having a recess formed therein in and includes a collar configured to at least partially encircle the spinal rod member, said collar formed of a shape memory polymeric material.

26. The system of claim 25 wherein the rod member is formed of a first shape memory polymeric material and the collar is formed of a second shape memory polymeric material different from the first shape memory polymeric material.

27. The system of claim 25 comprising a second spinal rod member.

28. The system of claim 27 comprising a lateral connector having a first end secured to the rod member and a second end secured to the second rod member.

29. The system of claim 28 wherein the lateral connector comprises a shape memory polymeric material.

30. The system of claim 29 comprising a connection element interconnecting the lateral connector to the rod member, said connection element comprising a collar comprising a shape memory polymeric material.

31. A connector for securing a rod member, said connector comprising:

a body having a recess therein configured to receive a portion of the rod member; and

a collar provided to at least partially encircle a portion of the rod member and sized to be received within the recess of the body, the collar comprising a shape memory polymeric material and provided in a first configuration whereby absorption of thermal energy the collar deforms to a second configuration to secure the rod member to the body.

32. The connector of claim 31 wherein the rod member is an elongate rod having a length sufficient to extend to at least two adjacent vertebrae.

33. The connector of claim 31 wherein the body comprises a threaded portion to engage a bony structure.

34. The connector of claim 31 wherein the body is formed of a material selected from the group consisting of:

titanium, stainless steel, surgical steel, composite materials and polymeric materials.

35. The connector of claim 31 wherein the shape memory polymeric material is formed from a polymer derived from the monomeric repeating units selected from the group consisting of:

l, d, or d/l lactide;

glycolide;

ethers;

olefins, ethylene, propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, styrene, norbornene;

butadiene;

acrylate, methacrylate, methyl methacrylate;

caprolactone; and

mixtures of these monomeric repeating units.

36. The connector of claim 31 wherein the shape memory polymeric material is non-biodegradable.

37. The connector of claim 31 wherein the collar comprises a cylindrical sleeve.

38. The connector of claim 37 wherein the cylindrical sleeve is slit.

39. The connector of claim 31 wherein the recess defines an opening extending through and fully encircled by said body.

40. An orthopedic implant for treating a spinal defect said implant comprising:

a flexible cord provided in a first configuration sufficient to extend from a first bony structure to a second bony structure, said cord comprising a shape memory polymeric material wherein upon absorption of thermal energy the cord deforms to a second configuration different from the first configuration.

41. The implant of claim 40 wherein the cord in the first configuration has a first length and in the second configuration has a second length shorter than the first length.

42. The implant of claim 40 wherein the cord in the first configuration has a first length and in the second configuration has a second length longer than the first length.

43. The implant of claim 40 wherein the cord has a length sufficient to wrap about bony structures on two or more vertebrae.

44. The implant of claim 40 wherein the cord is secured to a first bony structure with a fixation device.

45. The implant of claim 40 wherein said cord is secured to the first bony structure with a fixation device.

46. A method of treating a spinal defect, said method comprising:

surgically preparing two or more vertebrae to receive a vertebral implant in a patient in need of treatment;

connecting an elongate member to a first one of the two or more vertebrae, and connecting the elongate member to a second one of the two or more vertebrae, wherein the elongate member comprises a shape memory polymeric material and is provided in a first configuration; and

stimulating said implant to induce said implant to deform into a second configuration.

47. The method of claim 46 wherein the elongate member is a rod.

48. The method of claim 46 wherein the elongate member is a flexible cord.

49. A method of treating a spinal defect, said method comprising:

surgically preparing the patent to receive an implant;

selecting an implant comprising a flexible cord having a first length sufficient to extend from a first vertebra to a second vertebra, said cord formed of a shape memory polymeric material;

attaching said cord to a first vertebra and then to a second vertebra; and

stimulating said cord to absorb thermal energy and induce said cord to deform.

50. The method of claim 49 wherein said stimulating induces the cord to deform from a first length to a second length shorter than the first length.

51. The method of claim 49 wherein the shape memory polymeric material is formed of a material selected from the group consisting of:

d, l, d/l, polylactide;

polyglycolide, poly(lactide-co-glycolide), poly(β

-hydroxy butyrate);

poly(β

-hydroxy butyrate-co-hydroxyvalerate), poly(trimethylene carbonate) polyurethane, poly(ethylene-co-vinyl acetate), poly(ethylene-co-propylene), poly(ethylene-co-propylene-co-diene), poly(ε

-caprolactone), polyimino carbonates, polyanhydrides, and copolymers of ethylene and propylene.

52. The method of claim 49 wherein the shape memory polymeric material is biodegradable.

53. The method of claim 49 wherein the shape memory polymeric material is non-biodegradable.