Anterior cervical plating system

• US 6,152,927 A
• Filed: 09/20/1999
• Issued: 11/28/2000
• Est. Priority Date: 05/15/1997
• Status: Expired due to Term

• Current Assignee: SDGI Holdings Incorporated (Medtronic Plc)
• Original Assignee: SDGI Holdings Incorporated (Medtronic Plc)
• Inventors: Haid, Regis W. Jr., Farris, Robert A., Poyner, Jeffrey Wade, Papadopoulos, Stephen M., Sonntag, Volker K. H.
• Primary Examiner(s): Buiz, Michael
• Assistant Examiner(s): HO, TAN-UYEN THI
• Application Number:
  US09/399,525
• Time in Patent Office: 435 Days
• Field of Search: 606/69, 606/70, 606/71, 606/72, 606/73, 606/61, 606/60, 623/17
• US Class Current: 606/287
• CPC Class Codes: A61B 17/7059 Cortical plates A61B17/7007, A61B17/7058 take precedence
• CPC Class Codes: A61B 17/8033 having indirect contact with screw heads, or having contact with screw heads maintained with the aid of additional components, e.g. nuts, wedges or head covers
• CPC Class Codes: A61B 17/8042 the additional component being a cover over the screw head
• CPC Class Codes: A61B 17/8047 wherein the additional element surrounds the screw head in the plate hole A61B17/8052 takes precedence

Abstract

In one embodiment of the invention, an anterior fixation system includes a plate defining a plurality of screw holes, a number of screws and a number of locking assemblies for fixing the screws to the plate. The system includes two bone screws, a fixed angle screw and a variable angle screw, that are configured to extend through the same screw openings in the fixation plate. The surgeon can select either the fixed or variable angled screws to be implanted with a single plate and can place either type of screw into any of the screw holes along the plate. The fixation plate according to the invention can include several screw holes in various patterns that provide the surgeon with great flexibility in the placement of bone screws depending upon the spinal anatomy and pathology. The invention further contemplates a locking assembly to lock one or more bone screws within a respective screw hole. In one embodiment, the locking assembly includes a washer that is held to the plate by a staked locking screw. The washer includes an outer surface that overlaps one or more screw holes. The washer is initially loosely held to the plate by the locking screw so that various tools and bone screws can be passed through the screw holes. In one embodiment of the washer, the washer includes cut-outs corresponding to the screw holes, along with a notch and key configuration for setting the locking washer in its locked configuration.

Claims

1. A bone fixation system comprising:

an elongated plate having a top surface and a bottom surface and defining a plurality of holes between said surfaces, at least one of said plurality of holes including a spherical recess portion adjacent said top surface having a first diameter and defining an opening at said bottom surface having a second diameter less than said first diameter;

a first bone engaging fastener having a first elongated shank defining bone engaging threads thereon, a first enlarged head and a first intermediate portion between said shank and said head, said first shank having an outer diameter less than said second diameter so said first bone engaging fastener can be inserted through said at least one hole from said top surface of said plate, said first enlarged head defining a partially spherical surface complementary to said spherical recess of said at least one hole, and said first intermediate portion having a third diameter that is substantially smaller than said second diameter, whereby said first head of said first bone engaging fastener can be pivoted within said recess portion of said at least one hole so that said first bone engaging fastener can assume a plurality of angles relative to said bottom surface of said plate; and

a second bone engaging fastener having a second elongated shank defining bone engaging threads thereon, a second enlarged head and a second intermediate portion between said shank and said head, said second shank having an outer diameter less than said second diameter so said second bone engaging fastener can be inserted through said at least one hole from said top surface of said plate, said second enlarged head defining a partially spherical surface complementary to said spherical recess of said at least one hole, and said second intermediate portion having a substantially cylindrical portion with a fourth diameter that is approximately equal to said second diameter, whereby said second head of said second bone engaging fastener cannot be pivoted within said recess portion of said at least one hole so that said second bone engaging fastener can assume a fixed orientation relative to said bottom surface of said plate.

2. The bone fixation system of claim 1, further comprising a locking screw assembly for locking said heads of said bone engaging fasteners within said spherical recess portion of said plate.

3. The bone fixation system of claim 1, wherein said locking screw assembly includes:

a fastener bore defined in said plate adjacent said at least one hole;

a washer defining a central aperture and a recess communicating with said aperture, said washer further having an outer circumferential surface configured to contact said head of said bone engaging fastener extending through said at least one hole; and

a locking fastener having a head configured to be recessed within said recess of said washer and an elongated shank extending through said central aperture and configured to engage said fastener bore of said plate.

4. The bone fixation system of claim 3, wherein said outer circumferential surface of said washer has a concave curvature substantially corresponding to said partially spherical surface of said head of said bone engaging fastener.

5. The bone fixation system of claim 3, wherein said plate further defines a locking recess in said top surface concentric with said fastener bore and said at least one hole includes a flared recess overlapping said locking recess.

6. The bone fixation system of claim 2, wherein said locking screw assembly includes:

a fastener bore defined in said plate adjacent said at least one hole;

a washer defining a central aperture and a bottom surface configured to contact said head of said bone engaging fastener when said bone engaging fastener is extended through said at least one hole, said washer further defining a circumferential surface having a first portion overlapping said at least one hole when said washer is in a first position relative to said at least one hole and having a second portion that does not overlap said at least one hole when said washer is rotated from said first position to a second position, whereby said bone engaging fastener can be inserted through said at least one hole with said washer engaged to said plate when said washer is in said second position; and

a locking fastener having a head configured to be recessed within said recess of said washer and an elongated shank extending through said central aperture and configured to engage said fastener bore of said plate.

7. The bone fixation system of claim 6, wherein said plate further defines a locking recess in said top surface concentric with said fastener bore and said at least one hole includes a flared recess overlapping said locking recess.

8. The bone fixation system of claim 2, wherein said locking screw assembly includes:

a fastener bore defined in said plate adjacent said at least one hole;

a notch defined in said plate adjacent said fastener bore;

a washer defining a central aperture and a recess communicating with said aperture, said washer further having an outer surface configured to contact said head of said bone engaging fastener when said bone engaging fastener is extended through said at least one hole, said washer including a key adjacent said central aperture configured to seat within said notch in said plate to prevent rotation of said washer relative to said plate; and

a locking fastener having a head configured to be recessed within said recess of said washer and an elongated shank extending through said central aperture and configured to engage said fastener bore of said plate.

9. The bone fixation system of claim 8, wherein said plate further defines a locking recess in said top surface concentric with said fastener bore, said at least one hole including a flared recess overlapping said locking recess.

10. The bone fixation system of claim 1, wherein said elongated plated defines a plurality of vertebral nodes along the length of the plate.

11. The bone fixation system of claim 10, wherein there are provided at least two holes at a corresponding one of said vertebral nodes.

12. The bone fixation system of claim 1, wherein said elongated plate has a rounded edge extending between said top and bottom surfaces.

13. The bone fixation system of claim 1, wherein said head of said fastener includes a truncated top surface.

14. The bone fixation system of claim 1, wherein said bone engaging threads of said first and second bone engaging fasteners are self-tapping.

15. The bone fixation system of claim 1, wherein said third diameter is about 2.90 millimeters and said fourth diameter is about 4.05 millimeters.

16. A bone fixation system comprising:

an elongated plate having a top surface and a bottom surface and defining a plurality of holes between said surfaces, at least one of said plurality of holes including a spherical recess portion adjacent said top surface having a first diameter and defining an opening at said bottom surface having a second diameter less than said first diameter;

a bone engaging fastener having an elongated shank defining bone engaging threads thereon, an enlarged head and an intermediate portion between said shank and said head, said shank having an outer diameter less than said second diameter so said bone engaging fastener can be inserted through said at least one hole from said top surface of said plate, said enlarged head defining a partially spherical surface complementary to said spherical recess of said at least one hole; and

a locking screw assembly for locking said head of said bone engaging fastener within said recess portion of said plate, including;

a fastener bore defined in said plate adjacent said at least one hole;

a washer defining a central aperture and a recess communicating with said aperture, said washer further having an outer circumferential surface configured to contact said head of said bone engaging fastener when said bone engaging fastener is extended through said at least one hole; and

a locking fastener having a head configured to be recessed within said recess of said washer and an elongated shank extending through said central aperture and configured to engage said fastener bore of said plate.

17. The bone fixation system of claim 16, wherein said outer circumferential surface of said washer has a concave curvature substantially corresponding to said partially spherical surface of said head of said bone engaging fastener.

18. The bone fixation system of claim 16, wherein said plate further defines a locking recess in said top surface concentric with said fastener bore, said at least one hole including a flared recess overlapping said locking recess.

19. The bone fixation system of claim 16, wherein said plurality of holes includes at least one set of four holes in a diamond pattern, said locking screw assembly configured to contact heads of fasteners extending through said four holes.

20. The bone fixation system of claim 16, wherein said plurality of holes includes at least one four-hole cluster, said four-hole cluster having two hole pairs, said fixation system further including at least two of said locking screw assemblies each configured to contact a corresponding pair of fastener heads of fasteners extending through said hole pair.

21. The bone fixation system of claim 16, wherein said at least one of said plurality of holes includes at least one three-hole pattern, said locking screw assembly configured to contact fastener heads of fasteners extending through said three holes.

22. The bone fixation system of claim 16, wherein said at least one of said plurality of holes includes at least one five-hole pattern cluster, said five-hole pattern having two hole pairs and a single hole, the fixation system further including at least two locking screw assemblies, each locking screw assembly configured to engage fasteners extending through said single hole and a corresponding one of said hole pairs.

23. The bone fixation system of claim 16, wherein said elongated plated defines a plurality of vertebral nodes along the length of the plate.

24. The bone fixation system of claim 23, wherein there are provided at least two holes at a corresponding one of said vertebral nodes.

25. The bone fixation system of claim 16, wherein said elongated plate has a rounded edge extending between said top and bottom surfaces.

26. The bone fixation system of claim 16, wherein said washer further defines a first portion overlapping said at least one hole when said washer is in a first position relative to said at least one hole and a second portion that does not overlap said at least one hole when said washer is rotated from said first position to a second position, whereby said bone engaging fastener can be inserted through said at least one hole with said washer engaged to said plate when said washer is in said second position.

27. The bone fixation system of claim 16, wherein said head of said fastener includes a truncated top surface.

28. A bone fixation system comprising:

an elongated plate having a top surface and a bottom surface and defining a plurality of holes between said surfaces, at least one of said plurality of holes including a spherical recess portion adjacent said top surface having a first diameter and defining an opening at said bottom surface having a second diameter less than said first diameter;

a bone engaging fastener having an elongated shank defining bone engaging threads thereon, an enlarged head and an intermediate portion between said shank and said head, said shank having an outer diameter less than said second diameter so said bone engaging fastener can be inserted through said at least one hole from said top surface of said plate, said enlarged head defining a partially spherical surface complementary to said spherical recess of said at least one hole; and

a locking screw assembly for locking said head of said bone engaging fastener within said recess portion of said plate, including;

a fastener bore defined in said plate adjacent said at least one hole;

a washer defining a central aperture and a recess communicating with said aperture, said washer further having an outer circumferential surface configured to contact said head of said bone engaging fastener when said bone engaging fastener is extended through said at least one hole, said outer circumferential surface having a concave curvature substantially corresponding to said partially spherical surface of said head of said bone engaging fastener; and

a locking fastener having a head configured to be recessed within said recess of said washer and an elongated shank extending through said central aperture and configured to engage said fastener bore of said plate.

29. The bone fixation system of claim 28, wherein said plate further defines a locking recess in said top surface concentric with said fastener bore, said at least one hole including a flared recess overlapping said locking recess.

30. The bone fixation system of claim 28, wherein said elongated plated defines a plurality of vertebral nodes along the length of the plate.

31. The bone fixation system of claim 30, wherein there are provided at least two holes at a corresponding one of said vertebral nodes.

32. The bone fixation system of claim 28, wherein said elongated plate has a rounded edge extending between said top and bottom surfaces.

33. The bone fixation system of claim 28, wherein said head of said fastener includes a truncated top surface.

34. A bone fixation system comprising:

an elongated plate having a top surface and a bottom surface and defining a plurality of holes between said surfaces, at least one of said plurality of holes including a spherical recess portion adjacent said top surface having a first diameter and defining an opening at said bottom surface having a second diameter less than said first diameter;

a bone engaging fastener having an elongated shank defining bone engaging threads thereon, an enlarged head and an intermediate portion between said shank and said head, said shank having an outer diameter less than said second diameter so said bone engaging fastener can be inserted through said at least one hole from said top surface of said plate, said enlarged head defining a partially spherical surface complementary to said spherical recess of said at least one hole; and

a locking screw assembly for locking said head of said bone engaging fastener within said recess portion of said plate, including;

a fastener bore defined in said plate adjacent said at least one hole;

a washer defining a central aperture and a recess communicating with said aperture, and a bottom surface configured to contact said head of said bone engaging fastener when said bone engaging fastener is extended through said at least one hole, said washer further defining a circumferential surface having a first portion overlapping said at least one hole when said washer is in a first position relative to said at least one hole and having a second portion that does not overlap said at least one hole when said washer is rotated from said first position to a second position, whereby said bone engaging fastener can be inserted through said at least one hole with said washer engaged to said plate when said washer is in said second position; and

a locking fastener having a head configured to be recessed within said recess of said washer and an elongated shank extending through said central aperture and configured to engage said fastener bore of said plate.

35. The bone fixation system of claim 34, further including a notch defined in said plate adjacent said fastener bore and wherein said washer further includes a key adjacent said central aperture configured to seat within said notch in said plate to prevent rotation of said washer relative to said plate.

36. The bone fixation system of claim 35, wherein said plate further defines a locking recess in said top surface concentric with said fastener bore, said at least one hole including a flared recess overlapping said locking recess.

37. The bone fixation system of claim 35, wherein said head includes a truncated top surface.

38. The bone fixation system of claim 34, wherein said elongated plated defines a plurality of vertebral nodes along the length of the plate.

39. The bone fixation system of claim 38, wherein there are provided at least two holes at a corresponding one of said vertebral nodes.

40. The bone fixation system of claim 34, wherein said elongated plate has a rounded edge extending between said top and bottom surfaces.

41. A bone fixation system comprising:

an elongated plate having a top surface and a bottom surface and defining a plurality of holes between said surfaces, at least one of said plurality of holes including a spherical recess portion adjacent said top surface having a first diameter and defining an opening at said bottom surface having a second diameter less than said first diameter;

a bone engaging fastener having an elongated shank defining bone engaging threads thereon, an enlarged head and an intermediate portion between said shank and said head, said shank having an outer diameter less than said second diameter so said bone engaging fastener can be inserted through said at least one hole from said top surface of said plate, said enlarged had defining a partially spherical surface complementary to said spherical recess of said at least one hole; and

a locking screw assembly for locking said head of said bone engaging fastener within said recess portion of said plate, including;

a fastener bore defined in said plate adjacent said at least one hole;

a notch defined in said plate adjacent said fastener bore;

a washer defining a central aperture and a recess communicating with said aperture, said washer further having an outer surface configured to contact said head of said bone engaging fastener when said bone engaging fastener is extended through said at least one hole, said washer including a key adjacent said central aperture configured to seat within said notch in said plate to prevent rotation of said washer relative to said plate; and

a locking fastener having a head configured to be recessed within said recess of said washer and an elongated shank extending through said central aperture and configured to engage said fastener bore of said plate.

42. The bone fixation system of claim 41, said washer includes a first portion overlapping said at least one hole when said washer is in a first position relative to said at least one hole and having a second portion that does not overlap said at least one hole when said washer is rotated from said first position to a second position, whereby said bone engaging fastener can be inserted through said at least one hole with said washer engaged to said plate when said washer is in said second position.

43. The bone fixation system of claim 42, wherein said head includes a truncated top surface.

44. The bone fixation system of claim 41, wherein said elongated plated defines a plurality of vertebral nodes along the length of the plate.

45. The bone fixation system of claim 44, wherein there are provided at least two holes at a corresponding one of said vertebral nodes.

46. The bone fixation system of claim 41, wherein said elongated plate has a rounded edge extending between said top and bottom surfaces.

47. A bone fixation system comprising:

four bone engaging fasteners, each having an enlarged head and a threaded shank;

an elongated plate sized to span between at least three vertebrae, said plate defining two sets of two holes, each configured to receive said threaded shank of said bone engaging fasteners therethrough, a first set having a first hole aligned over a first vertebra and a second hole aligned over a second vertebra when said plate spans the vertebrae, and a second set having a third hole adjacent said second hole and aligned over the second vertebra, and a fourth hole aligned over a third vertebra adjacent the second vertebra; and

a pair of locking screw assemblies, one each for each of said two sets of two holes, each of said locking screw assemblies having a washer configured to overlap each of said two holes of said first and second sets when a bone engaging fastener extends through a corresponding one of said holes.

48. The bone fixation system of claim 47, wherein said plate has a top surface and bottom surface, said holes extend between said top and bottom surfaces, said holes further including a spherical recess portion adjacent said top surface, said four bone engaging fasteners including at least one of:

a first bone engaging fastener having a first head that can be pivoted within said recess portion of said holes so that said first bone engaging fastener can assume a plurality of angles relative to said bottom surface of said plate; and

a second bone engaging fastener having a second head that cannot be pivoted within said recess portion of said holes so that said second bone engaging fastener can assume a fixed orientation relative said bottom surface of said plate.

49. The bone fixation system of claim 47, wherein said washer has an outer circumferential surface with a concave curvature substantially corresponding to a partially spherical surface of said head of said bone engaging fasteners.

50. The bone fixation system of claim 47, wherein each of said pair of locking screw assemblies further includes:

a fastener bore defined in said plate adjacent a corresponding one of said two sets of two holes;

said washer defining a central aperture, a recess communicating with said aperture, and a bottom surface configured to contact said heads of said bone engaging fasteners when said bone engaging fasteners are extended through a respective one of said holes.

51. The bone fixation system of claim 50, wherein said plate further defines a locking recess in a top surface of said plate concentric with a respective one of said fastener bores and said at least one hole includes a flared recess overlapping said locking recess.

52. The bone fixation system of claim 50, said washer including a first portion overlapping said holes when said washer is in a first position relative to said holes and having a second portion that does not overlap said holes when said washer is rotated from said first position to a second position, whereby said bone engaging fasteners can be inserted through said holes with said washer engaged to said plate when said washer is in said second position.

53. The bone fixation system of claim 51, further comprising a locking fastener having a head configured to be recessed within said recess of said washer and an elongated shank extending through said central aperture and configured to engage said fastener bore of said plate.

54. The bone fixation system of claim 53, wherein said elongated shank of said locking fastener terminates in a sharp point for penetrating a vertebral body.

55. The bone fixation system of claim 53, wherein said head of said locking fastener defines a lower conical surface for contacting said washer.

56. The bone fixation system of claim 47, wherein said two sets of two holes define a four-hole cluster.

57. A bone fixation system comprising:

four bone engaging fasteners, each having an enlarged head and a threaded shank;

an elongated plate sized to span between at least three vertebrae, said plate defining a set of four adjacent holes, each configured to receive said threaded shank of said bone engaging fasteners therethrough; and

a locking screw assembly having a washer configured to overlap each of said four holes when a bone engaging fastener is extended through a corresponding one of said four holes.

58. The bone fixation system of claim 57, wherein said plate has a top surface and bottom surface, said holes extending between said top and bottom surfaces, said holes further including a spherical recess portion adjacent said top surface, said four bone engaging fasteners including at least one of:

a first bone engaging fastener having a first head that can be pivoted within said recess portion of said holes so that said first bone engaging fastener can assume a plurality of angles relative to said bottom surface of said plate; and

a second bone engaging fastener having a second head that cannot be pivoted within said recess portion of said holes so that said second bone engaging fastener can assume a fixed orientation relative said bottom surface of said plate.

59. The bone fixation system of claim 57, wherein said set of four adjacent holes defines a diamond pattern.

60. The bone fixation system of claim 57, wherein said washer has an outer circumferential surface with a concave curvature substantially corresponding to a partially spherical surface of said head of said bone engaging fasteners.

61. The bone fixation system of claim 57, wherein said locking screw assembly includes:

a fastener bore defined in said plate adjacent said set of four adjacent holes;

said washer defining a central aperture, a recess communicating with said aperture, and a bottom surface configured to contact said heads of said bone engaging fasteners when said bone engaging fasteners are extended through a respective one of said holes.

62. The bone fixation system of claim 61, wherein said plate further defines a locking recess in a top surface of said plate concentric with said fastener bore, said holes including a flared recess overlapping said locking recess.

63. The bone fixation system of claim 61, wherein said washer includes a first portion overlapping said holes when said washer is in a first position relative to said holes and having a second portion that does not overlap said holes when said washer is rotated from said first position to a second position, whereby said bone engaging fasteners can be inserted through said holes with said washer engaged to said plate when said washer is in said second position.

64. The bone fixation system of claim 61, further comprising a locking fastener having a head configured to be recessed within said recess of said washer and an elongated shank extending through said central aperture and configured to engage said fastener bore of said plate.

65. The bone fixation system of claim 64, wherein said elongated shank of said locking fastener terminates in a sharp point for penetrating a vertebral body.

66. The bone fixation system of claim 64, wherein said head of said locking fastener defines a lower conical surface for contacting said washer.

67. A bone fixation system comprising:

five bone engaging fasteners, each having an enlarged head and a threaded shank;

an elongated plate sized to span between at least three vertebrae, said plate defining three sets of holes, each hole configured to receive said threaded shank of said bone engaging fasteners therethrough, a first set having two holes aligned over a first vertebra, a second set having at least one hole aligned over a second vertebrae when said plate spans three vertebrae, and a third set having two holes aligned over the third vertebra; and

a pair of locking screw assemblies, a first one of said locking screw assemblies disposed between said first set and said second set of holes and including a first washer configured to overlap each of said two holes of said first set and said one hole of said second set when a bone engaging fastener extends through a corresponding one of said holes, and a second one of said locking screw assemblies disposed between said second set and said third set of holes and including a second washer configured to overlap said one hole of said second set and each of said two holes of said third set when a bone engaging fastener extends through a corresponding one of said holes.

68. The bone fixation system of claim 67, wherein said plate has a top surface and bottom surface, said holes extending between said top and bottom surfaces, said holes further including a spherical recess portion adjacent said top surface, said four bone engaging fasteners including at least one of:

a first bone engaging fastener having a first head that can be pivoted within said recess portion of said holes so that said first bone engaging fastener can assume a plurality of angles relative to said bottom surface of said plate; and

a second bone engaging fastener having a second head that cannot be pivoted within said recess portion of said holes so that said second bone engaging fastener can assume a fixed orientation relative said bottom surface of said plate.

69. The bone fixation system of claim 67, wherein each of said pair of locking screw assemblies includes:

a fastener bore defined in said plate adjacent said respective sets of holes;

said washer defining a central aperture, a recess communicating with said aperture, and a bottom surface configured to contact said heads of said bone engaging fasteners.

70. The bone fixation system of claim 69, wherein said plate further defines a pair of locking recesses in said top surface concentric with a corresponding one of said fastener bores and said holes include a flared recess overlapping a respective one of said locking recesses.

71. A bone fixation system comprising:

six bone engaging fasteners, each having an enlarged head and a threaded shank;

an elongated plate sized to span between at least three vertebrae, said plate defining a three sets of two adjacent holes, each hole configured to receive said threaded shank of said bone engaging fasteners therethrough; and

three locking screw assemblies having a washer configured to overlap a corresponding one of said three sets of two adjacent holes, said washer engaging said enlarged heads of said fasteners when said fasteners are extended through a corresponding one of said adjacent holes.

72. The bone fixation system of claim 71, wherein said plate further defines a fastener bore between a corresponding one of said set of two adjacent holes;

said washer defining a central aperture and having a bottom surface configured to contact said heads of said bone engaging fasteners when said bone engaging fasteners are extended through respective ones of said adjacent holes.

73. The bone fixation system of claim 72, further comprising a locking fastener having an elongated shank extending through said central aperture and configured to engage said fastener bore of said plate.

74. The bone fixation system of claim 73, wherein said washer defines a recess concentric with said central aperture and said head of said locking fastener is configured to be recessed within said recess of said washer.

75. The bone fixation system of claim 71, wherein said plate has a top surface and bottom surface, said holes extending between said top and bottom surfaces, each of said holes defining a recess portion, said six bone engaging fasteners including at least one first bone engaging fastener having a first head that can be pivoted within said recess portion of one of said holes so that said first bone engaging fastener can assume a plurality of angles relative to said bottom surface of said plate.

76. The bone fixation system of claim 71, wherein said elongated plated defines three vertebral nodes along the length of the plate, a corresponding one of said set of two adjacent holes being provided at a corresponding one of said nodes.

77. A bone fixation system comprising:

an elongated plate having a top surface and a bottom surface, said plate including a recess portion adjacent said top surface and a plurality of holes extending between said recess portion and said bottom surface, at least one of said plurality of holes defining an opening at said recess portion having a first diameter and an opening at said bottom surface having a second diameter less than said first diameter;

at least one bone engaging fastener having an elongated shank defining bone engaging threads thereon, an enlarged head and an intermediate portion between said shank and said head, said shank having an outer diameter less than said second diameter so said bone engaging fastener can be inserted through said at least one hole from said top surface of said plate; and

a locking screw assembly for locking said head of said bone engaging fastener within said recess portion of said plate, including;

a fastener bore defined in said plate adjacent said at least one hole;

a washer configured to be received within said recess portion of said plate, said washer defining a central aperture, said washer further including a bottom surface configured to contact said head of said bone engaging fastener when said bone engaging fastener is extended through said at least one hole; and

a locking fastener having a head configured to be received within said central aperture of said washer and an elongated shank extending through said central aperture configured to engage said fastener bore of said plate.

78. The bone fixation system of claim 77, wherein said at least one bone engaging fastener has a first head that can be pivoted within said at least one hole so that said first bone engaging fastener can assume a plurality of angles relative to said bottom surface of said plate.

79. The bone fixation system of claim 77, wherein said elongated plated defines a plurality of vertebral nodes along the length of the plate, each of said vertebral nodes being provided with at least two holes.