Devices and methods for implanting fusion cages

• US 20040172037A1
• Filed: 03/04/2004
• Published: 09/02/2004
• Est. Priority Date: 08/26/1999
• Status: Active Grant

• Current Assignee: Burkus J. Kenneth, Eddie F. Ray III, John D. Dorchak, John L. White
• Original Assignee: Burkus J. Kenneth, Eddie F. Ray III, John D. Dorchak, John L. White
• Inventors: White, John L., Ray, Eddie F. III, Burkus, J. Kenneth, Dorchak, John D.
• Granted Patent: US 7,316,686 B2
• Time in Patent Office: Days
• US Class Current: 606/90
• CPC Class Codes: A61B 17/025 Joint distractors
• CPC Class Codes: A61B 17/1659 Surgical rasps, files, planes, or scrapers
• CPC Class Codes: A61B 17/1671 for the spine
• CPC Class Codes: A61B 17/1757 for the spine
• CPC Class Codes: A61B 17/32002 with continuously rotating, oscillating or reciprocating cutting instruments
• CPC Class Codes: A61B 2017/0256 for the spine
• CPC Class Codes: A61B 2090/036 abutting on tissue or skin
• CPC Class Codes: A61F 2/30744 End caps, e.g. for closing an endoprosthetic cavity
• CPC Class Codes: A61F 2/442 Intervertebral or spinal discs, e.g. resilient non-disc-shaped intervertebral inflatable pockets A61F2/441; non-disc-shaped intervertebral fusion implants A61F2/4455
• CPC Class Codes: A61F 2/4455 for the fusion of spinal bodies, e.g. intervertebral fusion of adjacent spinal bodies, e.g. fusion cages intervertebral discs A61F2/442
• CPC Class Codes: A61F 2/446 having a circular or elliptical cross-section substantially parallel to the axis of the spine, e.g. cylinders or frustocones
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2002/2817 Bone stimulation by chemical reactions or by osteogenic or biological products for enhancing ossification, e.g. by bone morphogenetic or morphogenic proteins [BMP] or by transforming growth factors [TGF]
• CPC Class Codes: A61F 2002/2835 Bone graft implants for filling a bony defect or an endoprosthesis cavity, e.g. by synthetic material or biological material
• CPC Class Codes: A61F 2002/3021 frustoconical
• CPC Class Codes: A61F 2002/30217 hollow cones, e.g. tubular-like cones
• CPC Class Codes: A61F 2002/30405 made by screwing complementary threads machined on the parts themselves
• CPC Class Codes: A61F 2002/30593 hollow
• CPC Class Codes: A61F 2002/30774 internally-threaded
• CPC Class Codes: A61F 2002/30777 Oblong apertures
• CPC Class Codes: A61F 2002/30785 : parallel
• CPC Class Codes: A61F 2002/30787 : inclined obliquely with respect to each other
• CPC Class Codes: A61F 2002/30789 : perpendicular with respect to each other
• CPC Class Codes: A61F 2002/3082 : Grooves
• CPC Class Codes: A61F 2002/30858 : Threads interrupted by grooves or sidewalls, e.g. flat sidewalls
• CPC Class Codes: A61F 2002/30861 : having threads of increasing or decreasing height
• CPC Class Codes: A61F 2002/30873 : Threadings machined on non-cylindrical external surfaces
• CPC Class Codes: A61F 2002/448 : comprising multiple adjacent spinal implants within the same intervertebral space or within the same vertebra, e.g. comprising two adjacent spinal implants
• CPC Class Codes: A61F 2002/4627 : with linear motion along or rotating motion about the instrument axis or the implantation direction, e.g. telescopic, along a guiding rod, screwing inside the instrument
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2230/0067 : conical

Abstract

Methods and instrumentation for spinal interbody fusion are disclosed. The instruments and methods are particularly adapted for interbody fusion in an unreamed disc space. One instrument is a distractor assembly including a first distractor and a second distractor configured to be inserted in side-by-side relation in the disc space. Fusion cages adapted for insertion into an unreamed disc space are provided to enhance load distribution between adjacent vertebral bodies and lateral stability of the spinal column. The fusion cages may be inserted after distracting the disc space with the distractor assembly. Instruments for preparing the disc space through the inserted fusion cages or for use with the distractor assembly are also provided.

Claims

1. An apparatus for distracting a spinal disc space for insertion of at least one implant in an unreamed disc space, the apparatus comprising:

a first distractor; and

a second distractor insertable in side-by-side relation with said first distractor in the disc space, said second distractor including a medially extending portion having a guide surface abutting said first distractor to maintain a spacing between said first and second distractors as said first and second distractors are inserted into the disc space.

3. The apparatus of claim 1, wherein each of said first and second distractors includes a body portion having a length extending between a leading end and a trailing end, said body portions having a height between an upper surface and a lower surface sufficient to distract the disc space to a desired disc space height.

4. The apparatus of claim 3, wherein said medially extending portion of said second distractor is integrally formed with said body portion.

5. The apparatus of claim 3, wherein said medially extending portion has a height less than the height of said body portion of said second distractor.

6. The apparatus of claim 3, wherein each of said body portions have a height that is substantially the same as the height of the leading end of the at least one implant.

7. The apparatus of claim 3, wherein said leading end of said body portion is tapered to facilitate insertion of said distractor into the disc space.

8. The apparatus of claim 3, wherein said upper and lower surfaces include notches formed along at least a portion of said length of said body portion.

9. The apparatus of claim 3, wherein said medially extending portion extends from said trailing end along said length of said body portion of said second distractor to a position proximate said leading end of said second distractor.

10. The apparatus of claim 9, wherein said medially extending portion extends along said body portion about three-fourths of said length of said body portion.

11. The apparatus of claim 3, wherein each of said first and second distractors include a connecting portion extending proximally from said trailing end, said connecting portion having a height between a top surface and a bottom surface that is greater than said height of said body portion of said first and second distractors.

12. The apparatus of claim 11, wherein each of said connecting portions includes at least one anchoring member extending towards said leading end of said body portion along one of said upper or lower surfaces of said body portion.

13. The apparatus of claim 1, wherein said guide surface of said medially extending portion guides the insertion of the at least one implant into the distraction channel formed in the unreamed disc space after withdrawal of said first distractor.

14. The apparatus of claim 1, wherein:

said first distractor includes a body portion having a length extending between a leading end and a trailing end, said first distractor including a connecting portion extending from said trailing end of said body portion; and

said second distractor includes a body portion having a length extending between a leading end and a trailing end, said second distractor including a connecting portion extending from said trailing end of said body portion, said connecting portion of said second distractor including a guide member extending proximally therefrom.

15. The apparatus of claim 14, wherein said guide member includes a guide surface aligned with said guide surface of said medially extending portion.

16. The apparatus of claim 15, wherein said guide surface of said medially extending portion and said guide surface of said guide arm each have a concave shape.

17. The apparatus of claim 14, wherein said guide arm includes a notch formed in a proximal end thereof, and said connecting portion of said first distractor includes an extension member having a protrusion positionable in said notch.

2. The apparatus of claim 2, wherein said first and second distractors have a central axis extending therethrough when in said side-by side relation and said guide surface is offset towards said first distractor from said central axis.

18. A distractor assembly for performing a surgical procedure in a spinal disc space, the distractor assembly having a central axis extending therethrough, said distractor assembly comprising:

first distractor insertable in the disc space at a first implant location offset to a first side of the central axis;

a second distractor positionable adjacent said first distractor and insertable in the disc space at a second implant location is offset to a second side of the central axis, said second distractor having a guide surface adjacent said first distractor, wherein said guide surface is offset a distance from the central axis towards said first distractor.

19. The distractor assembly of claim 18, further comprising a first shaft removably attached to said first distractor and a second shaft removably attached to said second distractor.

20. The distractor assembly of claim 18, wherein said second distractor includes a medially extending portion forming said guide surface.

21. The distractor assembly of claim 20, wherein each of said first and second distractors includes a body portion having a length extending between a leading end and a trailing end, said body portions having a height sufficient to distract the disc space to a desired disc space height.

22. The distractor assembly of claim 21, wherein said medially extending portion has a height less than the height of said body portion of said second distractor.

23. The apparatus of claim 21, wherein said medially extending portion extends from said trailing end of said second distractor to a position proximate said leading end of said second distractor.

24. A fusion device insertable in the disc space between an upper vertebra and a lower vertebra, the device comprising:

a body extending between a leading end and a trailing end, said body having a wall defining a hollow interior, said wall having upper and lower bearing surfaces separated by a height that is selected to maintain the desired spacing between the upper vertebra and the lower vertebra, said height distance being tapered from a first height at said leading end to a second height at said trailing end to restore lordosis when the device is inserted in the disc space, said height between said upper and lower bearing surface being selected so that said body contacts the cortical bone of a substantially intact upper vertebral endplate and the cortical bone of a substantially intact lower vertebral endplate when the device is inserted in an unreamed disc space.

25. The device of claim 24, said device further including one or more threads extending outwardly from said upper and lower bearing surfaces to engage the cortical bone of the adjacent vertebral endplate with said upper and lower bearing surfaces contacting the adjacent vertebral endplates.

26. The device of claim 25, wherein said body defines a number of openings in said upper bearing surface in communication the upper vertebra and a number of openings in said lower bearing surface in communication with the lower vertebra when said device is positioned in the disc space.

27. The device of claim 26, wherein said threads are configured to deposit bone from the endplate through said openings into said hollow interior as said device is threaded into the disc space.

28. The device of claim 25, wherein said threads increase in depth from said leading end to said trailing end.

29. The device of claim 28, wherein said threads include:

a crest;

a leading face extending from said body to said crest;

a trailing face extending from said body to said crest, wherein said thread has a midpoint between said leading face and said trailing face at its junction with said body, said crest being positioned more proximate said trailing end than said midpoint.

30. The device of claim 29, wherein said leading face is convex and said trailing face is concave.

31. The device of claim 30, wherein said threads have a height of 1 mm above said body at said leading end and a height of 1.5 mm above said body at said trailing end.

32. The device of claim 24, wherein said body includes concave sidewalls extending between said upper bearing surface and said lower bearing surface.

33. The device of claim 32, wherein said body includes at least one opening formed through each of said concave sidewalls in communication with said hollow interior.

34. The device of claim 33, wherein said body includes:

a pair of openings adjacent said trailing end formed though said upper bearing surface in communication with said hollow interior;

a pair of openings adjacent said leading end formed though said upper bearing surface in communication with said hollow interior;

a pair of openings adjacent said trailing end formed though said lower bearing surface in communication with said hollow interior; and

a pair of openings adjacent said leading end formed though said lower bearing surface in communication with said hollow interior.

35. The device of claim 24, wherein said body includes an end nose at said leading end.

36. The device of claim 35, wherein said end nose includes a rounded configuration and a recessed hole formed through said nose communicating with said hollow interior.

37. An apparatus insertable in a disc space between adjacent vertebrae, comprising:

a first fusion cage positionable at a first location in the disc space, said first fusion cage having a body extending between a leading end and a trailing end and defining a hollow interior opening at said trailing end; and

a spacer having a connector positionable in said trailing end opening of said first cage to secure said spacer to said first fusion cage, said spacer further including a spacing member spaced from said connector and positionable outside of said body when said spacer is secured to said first fusion cage, said spacing member having a guide surface opposite said first fusion cage, wherein said guide surface guides the insertion of a second fusion cage at a second location in the disc space that is spaced from said first fusion cage.

38. The apparatus of claim 37, wherein said body of said first fusion cage includes threads extending outwardly therefrom to engage the cortical bone of the adjacent vertebral endplate.

39. The apparatus of claim 37, wherein said body includes an upper bearing surface and a lower bearing surface separated by a spacing distance, said spacing distance of said body being selected so that said body contacts the cortical bone of the upper vertebral endplate and the cortical bone of the lower vertebral endplate when the device is inserted in an unreamed disc space.

40. The apparatus of claim 39, wherein:

said body includes concave sidewalls extending between said upper and lower bearing surfaces; and

said spacing member includes a convex lateral surface opposite said guide surface positionable in one of said concave sidewalls.

41. The apparatus of claim 37, wherein said connector has a cross-sectional shape that is received in form fitting engagement with a trailing end wall opening of said cage.

42. A method for distracting a disc space, comprising:

providing a first distractor having a medial portion with a guide surface extending along said first distractor;

providing a second distractor;

assembling the first and second distractors with the second distractor abutting the guide surface to form a distractor assembly, the distractor assembly having a central axis with said guide surface of said first distractor offset from said central axis; and

inserting the distractor assembly into the disc space.

43. The method of claim 42, further including preparing a starter channel at the anterior lip of the disc space adjacent at the distractor insertion locations.

44. The method of claim 42, further comprising removing the second distractor from the disc space to form a distraction channel in the disc space at the first distractor location.

45. The method of claim 44, further comprising:

providing a fusion cage having a trailing end wall opening and a leading end with a spacing height approximating the distracted disc space height; and

inserting the fusion cage in disc space along the guide surface to maintain lateral positioning of the fusion cage in the disc space.

46. The method of claim 45, further comprising:

removing the first distractor; and

inserting a spacer into the trailing end wall opening of the fusion cage, the spacer having a spacing member positionable outside the fusion cage along a medial sidewall of the fusion, the spacing member having a guide surface opposite the fusion cage.

47. The method of claim 46, further comprising:

providing a second fusion cage having a leading end with a spacing height approximating the distracted disc space height; and

inserting the second fusion cage in disc space along the guide surface of the spacing member to maintain lateral positioning of the second fusion cage in the disc space.

48. The method of claim 47, wherein the inserted fusion cages each include at least one opening providing communication between a hollow interior of the cage and the adjacent vertebral endplates and further comprising removing bony material from the adjacent vertebral endplate through the opening.

49. The method of claim 48, further comprising placing bone growth material in the hollow interior of the fusion cages.

50. A method for inserting one or more fusion cages in the disc space between an upper vertebra and a lower vertebrae, comprising:

providing a fusion cage including a body having a hollow interior extending between a trailing end and a leading end, the body further including an upper bearing surface and a lower bearing surface separated by a height, the height being substantially the same as the desired spacing between the intact endplates of the upper vertebra and lower vertebra, respectively;

accessing a disc space;

distracting the disc space; and

inserting the fusion cage in the disc space with endplates of the upper and lower vertebra substantially intact and in contact with the upper and lower bearing surfaces, respectively, of the fusion cage.

51. The method of claim 50, wherein the body of the fusion cage is threaded and the height is tapered to restore lordosis.

52. The method of claim 50, wherein the body defines a number of openings in each of the top and bottom bearing surfaces in communication with the hollow interior.

53. The method of claim 50, wherein the fusion cage includes threads extending outwardly from the body, the threads engaging the cortical bone of the vertebral end plates.

54. The method of claim 53, wherein the threads include a swept back profile toward the trailing end of the fusion cage.

55. The method of claim 54, wherein the threads increase in depth from the leading end to the trailing end of the fusion cage.

56. The method of claim 54, wherein the threads include:

a crest;

a convex leading wall extending between the body and the crest; and

a concave trailing wall extending between the body and the crest.

57. The method of claim 50, wherein the fusion cage includes a blunt nose at the leading end of the fusion cage, the blunt nose including a recess extending from the leading end into the nose towards the trailing end, the nose further including a hole formed therethrough communicating with the hollow interior.

58. A combination, comprising:

a distractor having a body portion with an upper surface and a lower surface and a distraction height therebetween, said distraction height corresponding to the desired disc space height between adjacent vertebral endplates; and

a fusion cage having a body extending between a leading end and a trailing end of said fusion cage, said body having an upper bearing surface and a lower bearing surface separated by a height that increases from said leading end to said trailing end along said body, said height at said leading end of said fusion cage being the same as said distraction height of said distractor, wherein said body portion of said fusion cage engages the intact adjacent vertebral endplates when said cage is inserted in the disc space.

59. The combination of claim 58, wherein said fusion cage includes one or more threads extending outwardly from said body portion, said threads configured to engage the cortical bone of the adjacent vertebral endplates and advance said fusion cage into the disc space as it is threaded therein.

60. The device of claim 59, wherein said threads increase in depth from said leading end to said trailing end.

61. The device of claim 60, wherein said threads include:

a crest;

a leading face extending from said body to said crest;

a trailing face extending from said body to said crest, wherein said thread has a midpoint between said leading face and said trailing face at its junction with said body, said crest being positioned more proximate said trailing end than said midpoint.

62. The device of claim 61, wherein said leading face is convex and said trailing face is concave.