Dynamic Six-Degrees-Of-Freedom Intervertebral Spinal Disc Prosthesis

• US 20100070033A1
• Filed: 09/12/2008
• Published: 03/18/2010
• Est. Priority Date: 09/12/2008
• Status: Active Grant

• Current Assignee: Keith L. Doty
• Original Assignee: Keith L. Doty
• Inventors: Doty, Keith L.
• Granted Patent: US 7,927,375 B2
• Time in Patent Office: Days
• US Class Current: 623/17.160
• CPC Class Codes: A61F 2/30965 Reinforcing the prosthesis by embedding particles or fibres during moulding or dipping
• CPC Class Codes: A61F 2/4425 made of articulated components
• CPC Class Codes: A61F 2002/302 toroidal, e.g. rings
• CPC Class Codes: A61F 2002/30364 Rotation about the common longitudinal axis
• CPC Class Codes: A61F 2002/30365 with additional means for limiting said rotation
• CPC Class Codes: A61F 2002/30433 using additional screws, bolts, dowels, rivets or washers e.g. connecting screws
• CPC Class Codes: A61F 2002/30451 soldered or brazed or welded
• CPC Class Codes: A61F 2002/30495 using a locking ring
• CPC Class Codes: A61F 2002/3055 for adjusting length
• CPC Class Codes: A61F 2002/30563 having elastic means or damping means, different from springs, e.g. including an elastomeric core or shock absorbers
• CPC Class Codes: A61F 2002/30565 having spring elements
• CPC Class Codes: A61F 2002/30579 with mechanically expandable devices, e.g. fixation devices
• CPC Class Codes: A61F 2002/30594 slotted, e.g. radial or meridian slot ending in a polar aperture, non-polar slots, horizontal or arcuate slots
• CPC Class Codes: A61F 2002/30601 telescopic
• CPC Class Codes: A61F 2002/30639 having rolling elements between both articulating surfaces
• CPC Class Codes: A61F 2002/30673 Lubricating means, e.g. synovial pocket
• CPC Class Codes: A61F 2002/307 Prostheses for animals
• CPC Class Codes: A61F 2002/30878 with non-sharp protrusions, for instance contacting the bone for anchoring, e.g. keels, pegs, pins, posts, shanks, stems, struts
• CPC Class Codes: A61F 2002/443 having two transversal endplates and at least one intermediate component
• CPC Class Codes: A61F 2220/0025 Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2220/0033 : made by longitudinally pushing a protrusion into a complementary-shaped recess, e.g. held by friction fit
• CPC Class Codes: A61F 2220/0041 : using additional screws, bolts, dowels or rivets, e.g. connecting screws
• CPC Class Codes: A61F 2220/0058 : soldered or brazed or welded
• CPC Class Codes: A61F 2230/0065 : toroidal, e.g. ring-shaped, doughnut-shaped
• CPC Class Codes: A61F 2250/0081 : Prosthesis for animals
• CPC Class Codes: A61F 2310/00017 : Iron- or Fe-based alloys, e.g. stainless steel
• CPC Class Codes: A61F 2310/00023 : Titanium or titanium-based alloys, e.g. Ti-Ni alloys
• CPC Class Codes: A61F 2310/00029 : Cobalt-based alloys, e.g. Co-Cr alloys or Vitallium
• CPC Class Codes: A61F 2310/00059 : Chromium or Cr-based alloys
• CPC Class Codes: A61F 2310/00101 : Molybdenum or Mo-based alloys
• CPC Class Codes: A61F 2310/00179 : Ceramics or ceramic-like structures
• CPC Class Codes: A61F 2310/00329 : Glasses, e.g. bioglass
• CPC Class Codes: A61F 2310/00748 : Coating made of titanium carbide

Abstract

The subject invention provides a modular six-degrees-of-freedom spatial mechanism for spinal disc prosthesis, with up to three rotational and up to three translational degrees-of-freedom within the entire workspace of a Functional Spinal Unit (FSU). The prosthetic disc mechanism consists of up to three independent cylindrical joints, each joint providing one linear and one rotational degree of freedom. The superior and inferior vertebral plates of the device anchor to the superior and inferior vertebrae of an FSU and the device maintains an inseparable mechanical linkage between those vertebrae for all normal motions and positions of the FSU. The device utilizes resilient spring elements, components that self-adjust in position and orientation, in conjunction with a fiber reinforced boot and toroidal belt, as well as a unique hydraulic damping system to accommodate dynamic and static forces and sudden shocks on the FSU. The device can adjust to maintain the appropriate, but changing, intervertebral spacing during normal FSU motion. Scaling, conjoined with cushioned, joint-limit stops, allows the device to realize almost any nominal spinal articulation, from the cervical to lumbar regions.

Claims

1. A prosthetic device for approximating spinal disc movement comprising:

a spring-dashpot system having a superior end and an inferior end that includes,

a superior segmented-wall inner core;

an inferior segmented-wall inner core that engages with the superior segmented-wall inner core;

one or more spring elements positioned around the segmented-wall inner cores,

an inferior hydraulic cylinder wall positioned around the one or more spring elements, and

a superior hydraulic cylinder wall that slidably engages telescopically with and is inseparable from the inferior hydraulic cylinder wall, such that the inferior and superior hydraulic cylinder walls confine the one or more spring elements;

a superior hydraulic cylinder plate having a top and bottom side, wherein the bottom side is fixedly attached to the superior end of the spring-dashpot system;

a first slide bearing block fixedly attached to the top side of the superior hydraulic cylinder plate;

a first rotation cylinder with a bearing raceway slidably affixed to the first slide bearing block;

an inferior hydraulic cylinder base having a top and bottom side, wherein the top side is fixedly attached to the inferior end of the spring-dashpot system;

a second slide bearing block fixedly attached to the bottom side of the inferior hydraulic cylinder base;

a second rotation cylinder with a bearing raceway slidably affixed to the second slide bearing block;

at least one means for attachment to a first vertebra being operably connected to the first rotation cylinder; and

at least one means for attachment to a second vertebra being operably connected to the second rotation cylinder,

such that when said device is implanted in the spine with said attachment means engaged with a first and second vertebra, said device forms a kinematic chain of inseparably connected, articulating components between said first and second vertebra, wherein said device can provide at least one and up to three independent rotational degrees of freedom and at least one and up to three independent linear degrees of freedom.

2. The device, according to claim 1, further comprising at least one hydraulic portal.

3. The device, according to claim 1, further comprising at least one indented wall slot within the bottom side of the superior hydraulic cylinder plate and capable of cooperatively engaging with the inferior segmented-wall inner core.

4. The device, according to claim 3, further comprising at least one indented wall slot within the top side of the inferior hydraulic cylinder base and capable of cooperatively engaging with the superior segmented-wall inner core.

5. The device, according to claim 1, further comprising a toroidal belt at least partially surrounding the spring-dashpot system.

6. The device, according to claim 3, wherein the toroidal belt comprises a solid fiber-weave-embedded elastomer material.

7. The device, according to claim 6, wherein the toroidal belt further comprises an interior cushioning material.

8. The device, according to claim 7, wherein the cushioning material is air, compressible fluid, or hydrogel material.

9. The device, according to claim 5 wherein the toroidal belt is unconnected and can move freely around the spring-dashpot system.

10. The device, according to claim 5, wherein the toroidal belt is fixedly engaged with each of said means for attachment to the vertebrae and surrounds the functional elements.

11. The device, according to claim 1, further comprising at least one bearing stop.

12. The device, according to claim 1, further comprising a locking key slot within at least one of the rotation cylinders for engaging with a locking key.

13. The device, according to claim 12, wherein the means for attachment to the vertebrae is affixed to at least one of the rotation cylinders utilizing the locking key.

14. The device, according to claim 1, wherein the one or more spring elements comprise one or more Belleville springs.

15. The device, according to claim 14, further comprising at least one matched-pair, or approximately matched-pair of Belleville springs.

16. The device, according to claim 15, further comprising at least one guard ring between matched Belleville spring pairs.

17. The device, according to claim 15, further comprising a raised lip on at least one of the Belleville springs in an approximately matched-pair.

18. The device, according to claim 1, further comprising at least one lock ring on both the inferior hydraulic cylinder wall and the superior hydraulic cylinder wall, wherein the lock rings render the cylinder walls inseparable.

19. The device, according to claim 1, further comprising at least one locking projection on at least one of the slide bearing blocks that, when engaged with the bearing raceway, renders the slide bearing block and rotating cylinder inseparable.

20. The device, according to claim 1, wherein at least one of the components comprises titanium steel, titanium-carbide-coated stainless steel, bio-inert hardened stainless steel, polyurethane, polyurethane thermoplastic, cobalt-chromium-molybdenum alloy, plastic, ceramics, glass, or other materials or combinations thereof.

21. The device, according to claim 1, further comprising an impermeable boot fixedly engaged with each of said means for attachment to the vertebrae and surrounding the functional elements.

22. The device, according to claim 21, further comprising a biocompatible lubricant sealed within the boot.

23. The device, according to claim 21, wherein the boot comprises a fiber-reinforced elastomer matrix.

24. The device, according to claim 23, wherein the fiber-reinforcement comprises a spherical cross weave, such that the weave direction of the embedded fibers is diagonal relative to the central axis of the boot structure.

25. The device, according to claim 23, wherein the elastomer matrix is a flexible silicon.

26. The device, according to claim 5, further comprising an impermeable boot fixedly engaged with each of said means for attachment to the vertebrae and to the toroidal belt.

27. The device, according to claim 26, further comprising a biocompatible lubricant sealed within the boot.

28. The device, according to claim 26, wherein the boot comprises a fiber-reinforced elastomer matrix.

29. The device, according to claim 28, wherein the fiber-reinforcement comprises a spherical cross weave, such that the weave direction of the embedded fibers is diagonal relative to the central axis the boot structure.

30. The device, according to claim 28, wherein the elastomer matrix is a flexible silicon.

31. The device, according to claim 26, wherein the toroidal belt comprises a solid fiber-weave-embedded elastomer material.

32. The device, according to claim 31, wherein the toroidal belt further comprises an interior cushioning material.

33. The device, according to claim 32, wherein the cushioning material is air, compressible fluid, or hydrogel material.

66. The device, according to claim 26, wherein the toroidal belt comprises a solid fiber-weave-embedded elastomer material.

67. The device, according to claim 66, wherein the toroidal belt further comprises an interior cushioning material.

68. The device, according to claim 67, wherein the cushioning material is air, compressible fluid, or hydrogel material.

34. A prosthetic device for approximating spinal disc movement comprising:

a spring-dashpot system having a superior end and an inferior end that includes,

a superior segmented-wall inner core;

an inferior segmented-wall inner core that engages with the superior segmented-wall inner core;

one or more spring elements positioned around the segmented-wall inner cores,

an inferior hydraulic cylinder wall positioned around the one or more spring elements, and

a superior hydraulic cylinder wall that slidably engages telescopically with and is inseparable from the inferior hydraulic cylinder wall, such that the inferior and superior hydraulic cylinder walls confine the one or more spring elements;

a superior hydraulic cylinder plate having a top and bottom side, wherein the bottom side is fixedly attached to the superior end of the spring-dashpot system and wherein the top side comprises a first slider joint raceway;

a first rotation cylinder comprising a linear bearing structure that is slidably connected to the first slider joint raceway;

an inferior hydraulic cylinder base having a top and bottom side, wherein the top side is fixedly attached to the inferior end of the spring-dashpot system and the bottom side comprises a second slider joint raceway;

a second rotation cylinder comprising a linear bearing structure that is slidably connected to the second slider joint raceway;

at least one means for attachment to a first vertebra being operably connected to the first rotation cylinder; and

at least one means for attachment to a second vertebra being operably connected to the second rotation cylinder,

such that when said device is implanted in the spine with said attachment means engaged with a first and second vertebra, said device forms a kinematic chain of inseparably connected, articulating components between said first and second vertebra, wherein said device can provide at least one and up to three independent rotational degrees of freedom and at least one and up to three independent linear degrees of freedom.

35. The device, according to claim 34, further comprising at least one hydraulic portal.

36. The device, according to claim 35, further comprising one or more bearings positioned within at least one of the slider joint raceways such that a linear bearing structure when slidably connected is supported by and moves upon the one or more bearings.

37. The device, according to claim 36, further comprising at least one bearing stop and/or bearing separator.

38. The device, according to claim 36, wherein the one or more bearings are ball bearings, rod bearings, textured rod bearings, curvate rod bearings, or combinations thereof.

39. The device, according to claim 34, further comprising at least one curvate bearing raceway within at least one of the rotation cylinders.

40. The device, according to claim 39, further comprising one or more bearings positioned within the at least one curvate bearing raceway.

41. The device, according to claim 40, wherein the means for attachment to a vertebra is operably and inseparably connected to a rotation cylinder utilizing the one or more bearings.

42. The device, according to claim 41, wherein the one or more bearings are ball bearings, rod bearings, textured rod bearings or combinations thereof.

43. The device, according to claim 39, further comprising at least one bearing stop.

44. The device, according to claim 34, further comprising a toroidal belt at least partially surrounding the spring-dashpot system.

45. The device, according to claim 44, wherein the toroidal belt comprises a solid fiber-weave-embedded elastomer material.

46. The device, according to claim 45, wherein the toroidal belt further comprises an interior cushioning material.

47. The device, according to claim 46, wherein the cushioning material is air, compressible fluid, or hydrogel material.

48. The device, according to claim 44, wherein the toroidal belt is unconnected and can move freely around the spring-dashpot system.

49. The device, according to claim 44, wherein the toroidal belt is fixedly engaged with each of said means for attachment to the vertebrae and surrounds the functional elements.

50. The device, according to claim 34, wherein the one or more spring elements comprise one or more Belleville springs.

51. The device, according to claim 50, further comprising at least one matched-pair of Belleville springs.

52. The device, according to claim 51, further comprising at least one guard ring between matched Belleville spring pairs.

53. The device, according to claim 51, further comprising a raised lip on at least one of the Belleville springs in a matched pair.

54. The device, according to claim 34, further comprising at least one lock ring on both the inferior hydraulic cylinder wall and the superior hydraulic cylinder wall, wherein the lock rings render the cylinder walls inseparable.

55. The device, according to claim 34, wherein at least one of the components comprises titanium steel, titanium-carbide-coated stainless steel, bio-inert hardened stainless steel, polyurethane, polyurethane thermoplastic, cobalt-chromium-molybdenum alloy, plastic, ceramics, glass, or other materials or combinations thereof.

56. The device, according to claim 34, further comprising an impermable boot fixedly engaged with each of said means for attachment to the vertebrae and surrounding the functional elements.

57. The device, according to claim 56, further comprising a biocompatible lubricant sealed within the boot.

58. The device, according to claim 56, wherein the boot comprises a fiber-reinforced elastomer matrix.

59. The device, according to claim 58, wherein the fiber-reinforcement comprises a spherical cross weave, such that the weave direction of the embedded fibers is diagonal relative to the central axis of the boot structure.

60. The device, according to claim 58, wherein the elastomer matrix is a flexible silicon.

61. The device, according to claim 44, further comprising an impermeable boot fixedly engaged with each of said means for attachment to the vertebrae and to the toroidal belt.

62. The device, according to claim 61, further comprising a biocompatible lubricant sealed within the boot.

63. The device, according to claim 61, wherein the boot comprises a fiber-reinforced elastomer matrix.

64. The device, according to claim 63, wherein the fiber-reinforcement comprises a spherical cross weave, such that the weave direction of the embedded fibers is diagonal relative to the central axis the boot structure.

65. The device, according to claim 63, wherein the elastomer matrix is a flexible silicon.

69. A method for approximating spinal disc movement utilizing a device comprising:

a spring-dashpot system having a superior end and an inferior end that includes,

a superior segmented-wall inner core;

an inferior segmented-wall inner core that engages with the superior segmented-wall inner core;

one or more spring elements positioned around the segmented-wall inner cores,

an inferior hydraulic cylinder wall positioned around the one or more spring elements, and

a superior hydraulic cylinder wall that slidably engages telescopically with and is inseparable from the inferior hydraulic cylinder wall, such that the inferior and superior hydraulic cylinder walls confine the one or more spring elements;

a superior hydraulic cylinder plate having a top and bottom side, wherein the bottom side is fixedly attached to the superior end of the spring-dashpot system;

a first slide bearing block fixedly attached to the top side of the superior hydraulic cylinder plate;

a first rotation cylinder with a bearing raceway slidably and inseparably affixed to the first slide bearing block;

an inferior hydraulic cylinder base having a top and bottom side, wherein the top side is fixedly attached to the inferior end of the spring-dashpot system;

a second slide bearing block fixedly attached to the bottom side of the inferior hydraulic cylinder base;

a second rotation cylinder with a bearing raceway slidably and inseparably affixed to the second slide bearing block;

at least one means for attachment to a first vertebra being operably connected to and inseparable from the first rotation cylinder; and

at least one means for attachment to a second vertebra being operably connected to and inseparable from the second rotation cylinder,

said method comprising securing the device within the spine of an animal utilizing said means for attachment to a first and second vertebra, such that said device forms a kinematic chain of inseparably connected, articulating components between said first and second vertebra, wherein said device can provide at least one and up to three independent rotational degrees of freedom and at least one and up to three independent linear degrees of freedom.

70. A method for approximating spinal disc movement utilizing a device comprising:

a spring-dashpot system having a superior end and an inferior end that includes,

a superior segmented-wall inner core;

an inferior segmented-wall inner core that engages with the superior segmented-wall inner core;

one or more spring elements positioned around the segmented-wall inner cores,

an inferior hydraulic cylinder wall positioned around the one or more spring elements, and

a superior hydraulic cylinder wall that slidably engages telescopically with and is inseparable from the inferior hydraulic cylinder wall, such that the inferior and superior hydraulic cylinder walls confine the one or more spring elements;

a superior hydraulic cylinder plate having a top and bottom side, wherein the bottom side is fixedly attached to the superior end of the spring-dashpot system and wherein the top side comprises a first slider joint raceway;

a first rotation cylinder comprising a linear bearing structure that is slidably connected to the first slider joint raceway;

an inferior hydraulic cylinder base having a top and bottom side, wherein the top side is fixedly attached to the inferior end of the spring-dashpot system and the bottom side comprises a second slider joint raceway;

a second rotation cylinder comprising a linear bearing structure that is slidably connected to the second slider joint raceway;

at least one means for attachment to a first vertebra being operably connected to the first rotation cylinder; and

at least one means for attachment to a second vertebra being operably connected to the second rotation cylinder,

said method comprising securing the device within the spine of an animal utilizing said means for attachment to a first and second vertebra, such that said device forms a kinematic chain of inseparably connected, articulating components between said first and second vertebra, wherein said device can provide at least one and up to three independent rotational degrees of freedom and at least one and up to three independent linear degrees of freedom.