Multi-lock anterior cervical plating system

• US 6,193,721 B1
• Filed: 02/11/1998
• Issued: 02/27/2001
• Est. Priority Date: 02/11/1997
• Status: Expired due to Term

• Current Assignee: Zimmer Spine, Inc. (Zimmer Biomet Holdings, Inc.)
• Original Assignee: Sulzer Spine Tech, Inc.
• Inventors: Michelson, Gary K.
• Primary Examiner(s): Buiz, Michael
• Assistant Examiner(s): REIP, DAVID OWEN
• Application Number:
  US09/022,293
• Time in Patent Office: 1,112 Days
• Field of Search: 606/61, 606/69, 606/70, 606/71, 606/72, 606/73, 606/76, 606/77
• US Class Current: 606/70
• CPC Class Codes: A61B 17/1604 Chisels; Rongeurs; Punches; Stamps
• CPC Class Codes: A61B 17/1671 for the spine
• CPC Class Codes: A61B 17/1728 for holes for bone plates or plate screws
• CPC Class Codes: A61B 17/1757 for the spine
• CPC Class Codes: A61B 17/7058 Plates mounted on top of bone anchor heads or shoulders
• CPC Class Codes: A61B 17/7059 Cortical plates A61B17/7007, A61B17/7058 take precedence
• CPC Class Codes: A61B 17/80 Cortical plates , i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates
• CPC Class Codes: A61B 17/8019 where the means are a separate tool rather than being part of the plate
• 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 17/8085 with pliable or malleable elements or having a mesh-like structure, e.g. small strips A61B17/8071, A61B17/8076 take precedence
• CPC Class Codes: A61B 17/861 specially shaped for gripping driver
• CPC Class Codes: A61B 17/8625 Shanks, i.e. parts contacting bone tissue
• CPC Class Codes: A61B 17/863 with thread interrupted or changing its form along shank, other than constant taper
• CPC Class Codes: A61B 17/8695 Washers surrounding screw head in plate hole A61B17/8047, between bone plate and bone A61B17/8028
• CPC Class Codes: A61B 17/8875 Screwdrivers, spanners or wrenches
• CPC Class Codes: A61B 2017/0046 with a releasable handle; with handle and operating part separable
• CPC Class Codes: A61B 2017/8655 with special features for locking in the bone
• CPC Class Codes: A61F 2/0077 Special surfaces of prostheses, e.g. for improving ingrowth A61F2/30767 takes precedence
• CPC Class Codes: Y10S 606/902 Cortical plate specifically adapted for a particular bone
• CPC Class Codes: Y10S 606/907 : Composed of particular material or coated
• CPC Class Codes: Y10S 606/908 : Bioabsorbable material
• CPC Class Codes: Y10S 606/91 : Polymer

Abstract

Anatomically contoured anterior cervical plates with bone ingrowth surfaces, providing for intersegmental compressive preloading, and a rigid and locked interface to all of the bone screws, with those engaging the vertebrae deployed in highly convergent pairs. The bone screws have a tapered self-tapping leading end, an increasing root diameter with a generally constant outer diameter with a thread that is narrow and sharp throughout and an enlarged head portion capable of an interference fit to the receiving holes of the plate. Instrumentation consists of plate holders, a compression apparatus and a pilot hole forming device that interlocks with the plate. Methods for spinal compression and bone hole preparation are provided.

Claims

1. An anterior cervical plate for engaging at least two vertebral bodies of a human cervical spine along the anterior aspect of the spine, said plate having a lower surface for contacting the cervical vertebral bodies and an upper surface opposite to said lower surface, said plate having a plurality of bone screw receiving holes extending through said plate from said upper surface to said lower surface, at least a first and second of said bone screw receiving holes being associated with a first of the cervical vertebral bodies, and a recess associated with said at least first and second of said bone screw receiving holes, said recess having a configuration for retaining a locking element for locking at least two bone screws in said at least first and second bone screw receiving holes, the central longitudinal axis of said recess being offset from a transverse line passing through the central longitudinal axes of said first and second bone screw receiving holes.

2. The plate of claim 1 further comprising at least a third bone screw receiving hole corresponding to the area between the first and second cervical vertebral bodies, and said recess being associated with said first and second bone screw receiving holes and with said third bone screw receiving hole.

3. The plate of claim 2 in which said recess overlaps a portion of said first bone screw receiving hole and said third bone screw receiving hole.

4. The plate of claim 1 in which said recess overlaps a portion of at least four bone screw receiving holes.

5. The plate of claim 1 in which said plate has a length longer than said width, and said lower surface has a first concave curvature parallel to said width.

6. The plate of claim 5 in which said first concave curvature has a radius of curvature in the order of approximately 16 to 21 mm.

7. The plate of claim 1 in which said lower surface of said plate has a second concave curvature parallel to said length.

8. The plate of claim 7 wherein said second concave curvature has a radius of curvature greater than 15 cm and less than 25 cm.

9. The plate of claim 1 in which said plate has a length sufficient to span at least three consecutive vertebral bodies.

10. The plate of claim 1 in which said lower surface of said plate has a complex concave curvature configured to mate with at least two vertebral bodies, and each bone screw receiving hole has a longitudinal axis that is generally perpendicular to said lower surface at the location of said bone screw receiving hole and each of said bone screw receiving holes is formed to retain a respective bone screw in a position in which the longitudinal axis of said respective bone screw is aligned with the longitudinal axis of said bone screw receiving hole.

11. The plate of claim 1 in which the central longitudinal axes of the bone screw receiving holes of at least one of said pairs of bone screw receiving holes form an included angle of greater than 14 degrees and less than 30 degrees.

12. The plate of claim 1 in which the central longitudinal axes of the bone screw receiving holes of at least one of said pairs of bone screw receiving holes form an included angle greater than 20 degrees and less than 30 degrees.

13. The plate of claim 1 in which at least a portion of said lower surface comprises a bone growth material.

14. The plate of claim 1 in which at least a portion of said lower surface comprises a bone ingrowth material.

15. The plate of claim 1 in which at least a portion of said plate is coated with a material to induce the formation of bone.

16. The plate of claim 1 in which said plate comprises bone morphogenetic protein.

17. The plate of claim 1 in which at least a portion of said plate is made of a material which is resorbable.

18. The plate of claim 17 in which said resorbable material is polyglyconate.

19. The plate of claim 17 in which said resorbable material is impregnated with a fusion promoting substance.

20. The plate of claim 1 in which at least a portion of said lower surface is textured so as to promote bone ingrowth.

21. The plate of claim 20 in which said textured portion is impregnated with a fusion promoting substance.

22. The plate of claim 1 in which at least a portion of said lower surface comprises a time released bone growth inducing material.

23. The plate of claim 1 in which at least a portion of said lower surface is roughened to promote the growth of bone along said lower surface.

24. The plate of claim 1 further comprising a slot along at least a portion of the longitudinal axis of said plate.

25. The plate of claim 1 in which at least at one end of said plate includes means for engaging a compression tool.

26. The plate of claim 25 in which said engaging means comprises a recess.

27. The plate of claim 25 in which said engaging means comprises a depression in said at least one end of said plate.

28. An anterior cervical plate for engaging at least two vertebral bodies of a human cervical spine along the anterior aspect of the spine, said plate having a length sufficient to span at least two adjacent cervical vertebral bodies, said plate having a lower surface for contacting the cervical vertebrae and an upper surface opposite to said lower surface, said plate having a plurality of bone screw receiving holes extending through said plate from said upper surface to said lower surface, at least a first and second of said bone screw receiving holes being associated with a first of the cervical vertebral bodies, and a recess for retaining a locking element for locking bone screws in said bone screw receiving holes, said recess having a central longitudinal axis offset from a transverse line passing through the central longitudinal axes of said first and second bone screw receiving holes, and a locking element movably engageable in said recess, said locking element being movable from at least a first position to a second position when engaged to said plate, said locking element being configured so as to permit insertion of bone screws into each of said first and second bone screw receiving holes when said locking clement is in said first position and is engaged to said plate, and said locking element bearing against at least a portion of at least two of said bone screws in said first and second bone screw receiving holes, respectively, when moved to said second position.

29. The plate of claim 28 in which said locking element has a bearing surface for bearing against a bone screw.

30. The plate of claim 28 in which said locking element has a camming surface.

31. The plate of claim 28 in which said locking element has a ramped surface.

32. The plate of claim 28 in which said recess has a threaded portion.

33. The plate of claim 32 in which said locking element comprises a threaded portion.

34. The plate of claim 32 in which said locking element has a camming surface.

35. The plate of claim 32 in which said locking element has a ramped surface.

36. The plate of claim 32 in which said locking element comprises a screw having a head portion and a threaded shaft.

37. The plate of claim 36 in which said locking element has a camming surface.

38. The plate of claim 36 in which said locking element has a ramped surface.

39. The plate of claim 28 in which said locking element comprises a rivet.

40. The plate of claim 29 in which said rivet has a camming surface.

41. The plate of claim 39 in which said rivet has a ramped surface.

42. The plate of claim 38 in which said recess has at least one camming surface for cooperation with said locking element.

43. The plate of claim 28 in which said locking element has a head with at least one segment removed therefrom.

44. The plate of claim 43 in which said removed segment has the same or greater radius of curvature as the corresponding bone screw receiving holes.

45. The plate of claim 28 further comprising an opening in the side wall of said bone screw receiving holes in communication with the side wall of said recess, said locking element having a plurality of projections adapted to fit within said side wall openings so as to cover a portion of said bone screw receiving hole when said locking element is moved from said first position to said second position.

46. The plate of claim 45 in which said projections have a ramped surface.

47. The plate of claim 28 in which said locking element is permanently attached to said plate.

48. The plate of claim 28 in which said locking element has at least three segments removed therefrom, each of said at least three segments corresponding to a different bone screw receiving hole whereby movement of said locking element from said first position to said second position causes said locking element to bear against at least a portion of the bone screws in said three bone screw receiving holes.

49. The plate of claim 28 in which said locking element has at least four segments removed, each of said at least four segments corresponding to a different bone screw receiving hole whereby movement of said locking element from said first position to said second position causes said locking element to bear against at least a portion of the bone screws in said four bone screw receiving holes.

50. The plate of claim 28 in which said locking element covers at least a portion said bone screw receiving holes when placed in said recess.

51. The plate of claim 28 in which said locking element covers at least a portion of one of said bone screw receiving holes.

52. The plate of claim 28 in which said plate has a length longer than said width, and said lower surface has a first concave curvature parallel to said width.

53. The plate of claim 52 in which said first concave curvature has a radius of curvature of the order of approximately 16-21 mm.

54. The plate of claim 28 in which said lower surface of said plate has a second concave curvature parallel to said length.

55. The plate of claim 54 in which said second concave curvature has a radius of curvature greater than approximately 15 cm and less than approximately 25 cm.

56. The plate of claim 28 in which said plate has a generally rectangular configuration with lobes extending from at least the corners of said plate and has at least one of said bone screw receiving holes located within the circumference of a representative one of said lobes.

57. The plate of claim 28 in which said plate has a length sufficient to span at least three consecutive vertebral bodies.

58. The plate of claim 28 in which the central axes of said bone screw receiving holes are perpendicular to said lower surface of said plate.

59. The plate of claim 28 in which the central longitudinal axes of the bone screw receiving holes of at least one of said pairs of bone screw receiving holes form an included angle of greater than 14 degrees and less than 30 degrees.

60. The plate of claim 28 in which the central longitudinal axes of the bone screw receiving holes of at least one of said pairs of bone screw receiving holes form an included angle greater than 20 degrees and less than 30 degrees.

61. The plate of claim 28 in which at least a portion of said lower surface comprises a bone ingrowth material.

62. The plate of claim 28 in which at least a portion of said plate is coated with a material to induce the formation of bone.

63. The plate of claim 28 in which said plate comprises bone morphogenetic protein.

64. The plate of claim 28 in which at least a portion of said plate is made of a material which is resorbable.

65. The plate of claim 64 in which said resorbable material is polyglyconate.

66. The plate of claim 64 in which said resorbable material is impregnated with a fusion romoting substance.

67. The plate of claim 28 in which at least a portion of said lower surface is textured so as to promote bone ingrowth.

68. The plate of claim 67 in which said textured portion is impregnated with a fusion promoting substance.

69. The plate of claim 28 in which at least a portion of said lower surface comprises a time released bone growth inducing material.

70. The plate of claim 28 in which at least a portion of said lower surface is roughened to promote the growth of bone along said lower surface.

71. The plate of claim 28 in which at least one end of said plate has means for removably engaging a compression tool.

72. The plate of claim 71 in which said engaging means comprises a depression at least one end of said plate.

73. The plate of claim 28 in which said plate includes an opening proximate said second bone screw receiving holes associated with said second adjacent vertebrae.

74. The plate of claim 73 in which said opening comprises a slot along the longitudinal axis of said plate.

87. The plate of claim 36 in which said rivet has a camming surface.

88. The plate of claim 36 in which said rivet has a ramped surface.

75. An anterior cervical plate system for engaging at least two vertebral bodies of a human cervical spine along the anterior aspect of the spine, said system comprising:

a plate having a first end, a second end, and a length sufficient to span at least two adjacent cervical vertebral bodies, said plate having a lower surface for contacting the cervical vertebral bodies and an upper surface opposite to said lower surface, said plate having a plurality of bone screw receiving holes extending through said plate from said upper surface to said lower surface, at least a first and second of said bone screw receiving holes being associated with a first of the adjacent vertebral bodies, and a recess for retaining a locking element for locking bone screws in said bone screw receiving holes, said recess having a central longitudinal axis offset from a transverse line passing through the central longitudinal axes of said first and second bone screw receiving holes, and a locking element movably engageable in said recess and being movable from at least a first position to a second position, said locking element having a head having a configuration so as to permit insertion of bone screws into said first and said second bone screw receiving holes, respectively, when in said first position, and said head bearing against a portion of the bone screws inserted into said first and said second bone screw receiving holes respectively, when moved to said second position; and

a plurality of bone screws each having a longitudinal axis and insertable into a respective one of said bone screw receiving holes in a direction from said upper surface to said lower surface to secure said plate to a the vertebral bodies.

76. The plate of claim 75 in which said locking element has a bearing surface for bearing against a bone screw.

77. The plate of claim 75 in which said locking element has a camming surface.

78. The plate of claim 75 in which said locking element has a ramped surface.

79. The plate of claim 75 in which said recess has a threaded portion.

80. The plate of claim 79 in which said locking element comprises a threaded portion.

81. The plate of claim 79 in which said locking element has a camming surface.

82. The plate of claim 79 in which said locking element has a ramped surface.

83. The plate of claim 79 in which said locking element has a head portion and a threaded shaft.

84. The plate of claim 83 in which said locking element has a camming surface.

85. The plate of claim 83 in which said locking element has a ramped portion surface.

86. The plate of claim 75 in which said locking element is a rivet.

89. The plate of claim 75 in which said recess has at least one camming surface for cooperation with said locking element.

90. The plate of claim 75 in which said locking element has at least two segments removed therefrom, said removed segments being arcuate and each having the same or greater radius of curvature as a corresponding one of said bone screw receiving holes.

91. The plate of claim 75 further comprising an opening in the side wall of said bone screw receiving holes in communication with the side wall of said recess, said locking element having a plurality of projections adapted to fit within said side wall openings so as to cover a portion of said first, second, and intermediate bone screw receiving holes when said locking element is moved from its first position to its second position.

92. The plate of claim 91 in which said projections have a ramped surface.

93. The plate of claim 75 in which said locking element is permanently attached to said plate.

94. The plate of claim 75 in which said locking element has at least three segments removed therefrom, each of said at least three segments corresponding to a different bone screw receiving hole whereby movement of said locking element from said first position to said second position causes said locking element to cover at least a portion of three bone screw receiving holes.

95. The plate of claim 75 in which said locking element has at least four segments removed therefrom, each of said at least four segments corresponding to a different bone screw receiving hole whereby movement of said locking element from said first position to said second position causes said locking element to cover at least a portion of four bone screw receiving holes.

96. The plate of claim 75 in which said locking element covers at least one of said bone screw receiving holes.

97. The plate of claim 75 wherein said plate has a length longer than said width, and said lower surface has a first concave curvature parallel to said width.

98. The plate of claim 97 wherein said first concave curvature has a first radius of curvature of approximately about 16-21 mm.

99. The plate of claim 98 wherein said lower surface of said plate has a second concave curvature parallel to said length.

100. The plate of claim 99 wherein said second concave curvature has a radius of curvature greater than approximately 15 cm and less than approximately 25 cm.

101. The plate of claim 75 in which said plate has a generally rectangular configuration, has lobes extending from at least the corners of said plate, and has at least one of said bone screw receiving holes are located within the circumference of a respective one of said lobes.

102. The plate of claim 75 in which said plate has a length sufficient to span at least three consecutive vertebral bodies.

103. The plate of claim 75 in which the central axes of said bone screw receiving holes are perpendicular to said lower surface of said plate.

104. The plate of claim 75 wherein said plurality of bone screws each have a head dimensioned to achieve an interference fit with a respective one of said bone screw receiving holes.

105. The plate of claim 104 in which said bone screws and said locking element have heads with means for engagement by the same tool for rotating said bone screw and said locking element.

106. The plate of claim 104 in which each of said bone screws has a first head with an irregular depression in the top of said first head for engagement with a screwdriver;

and said locking element has a second head with an irregular depression in said second head for engagement with a screwdriver, whereby both said first and said second heads may be engaged by the same screwdriver.

107. The plate of claim 75 in which each of said bone screws is a self-tapping screw.

108. The plate of claim 75 in which each of said bone screws has a tip remote from said head, a shank which is tapered from said head to said tip, and a thread having a substantially constant crest diameter over substantially the length of said shank.

109. The plate of claim 108 in which said thread of each of said bone screws has a thin profile and a sharp crest.

110. The plate of claim 75 in which said bone screws and said locking element do not project above the upper surface of said plate when said plate is installed.

111. The plate of claim 75 in which said bone screw receiving hole has means for preventing a bone screw from passing through said bone screw receiving hole.

112. The plate of claim 75 in which said bone screw receiving hole has an upper diameter portion and a smaller lower diameter portion to prevent a bone screw being placed in said bone screw receiving hole from passing through said bone screw receiving hole.

113. The plate of claim 75 in which the central longitudinal axes of the bone screw receiving holes of at least one of said pairs of bone screw receiving holes form an included angle of greater than 14 degrees and is than 30 degrees.

114. The plate of claim 75 in which the central longitudinal axes of the bone screw receiving holes of at least one of said pairs of bone screw receiving holes form an included angle greater than 20 degrees and less than 30 degrees.

115. The plate of claim 75 wherein at least a portion of said lower surface comprises a bone ingrowth material.

116. The plate of claim 75 in which at least a portion of said plate is made of a material which is resorbable.

117. The plate of claim 116 in which said resorbable material is polyglyconate.

118. The plate of claim 116 in which said resorbable material is impregnated with a fusion promoting substance.

119. The plate of claim 75 in which at least a portion of said lower surface is textured.

120. The plate of claim 119 in which said textured portion is impregnated with a fusion promoting substance.

121. The plate of claim 75 in which at least a portion of said lower surface comprises a time released bone growth material.

122. The plate of claim 75 in which at least one of said ends of said plate has means for removably engaging a compression tool.

123. The plate of claim 122 in which said engaging means comprises a depression in said at least one end of said plate.

124. The plate of claim 75 in which said plate includes an opening proximate said second bond screw receiving hole associated with the second adjacent vertebral body.

125. The plate of claim 124 in which said opening comprises a slot along the longitudinal axis of said plate.

126. An anterior cervical plating system for engaging at least three vertebral bodies of a human cervical spine along the anterior aspect of the spine, said system comprising:

a plate having a generally rectangular configuration with a first end, a second end, sides, and a length sufficient to span at least two adjacent cervical vertebral bodies, said plate having;

rounded lobes at each corner of said generally rectangular configuration and having rounded lobes on said sides between said first and second ends;

a lower surface for contacting the cervical vertebral bodies and an upper surface opposite to said lower surface;

a bi-concave curvature for conforming to the anterior aspect of the cervical spine in lordosis, said bi-concave curvature having a longitudinal concave curvature along the longitudinal axis of said plate and a transverse concave curvature along the transverse axis of said plate;

a plurality of bone screw receiving holes extending through said plate from said upper surface to said lower surface, a respective one of said plurality of bone screw receiving holes located at each of said rounded lobes such that said plate has a first pair of said bone screw receiving holes located at said first end of said plate and corresponding to a first of the adjacent vertebral bodies, a second pair of said bone screw receiving holes corresponding to a second of the adjacent vertebral bodies, and a third pair of said bone screw receiving holes corresponding to a third of the adjacent vertebral bodies;

a locking element receiving opening positioned between said first pair of bone screw receiving holes, said locking element receiving opening surrounded by a recess in said plate concentric with said locking element receiving opening and overlapping a portion of said first pair of bone screw receiving holes, said recess having a central longitudinal axis offset from a transverse line passing through the central longitudinal axes of said first pair of bone screw receiving holes; and

a locking element positioned in said locking clement receiving opening and having a head positionable within said recess, said head having a top surface with a depression for engaging a tool used to lock and unlock said locking element to said plate, said head being configured so as to permit insertion of bone screws into said bone screw receiving holes when in a first unlocked position and to bear against at least a portion of the bone screw in said bone screw receiving holes when moved to a second locked position.

127. The plate system of claim 126 in which the central longitudinal axes of the bone screw receiving holes of at least one of said pairs of bone screw receiving holes form an included angle of greater than 14 degrees and less than 30 degrees.

128. The plate system of claim 126 in which the central longitudinal axes of the bone screw receiving holes of at least one of said pairs of bone screw receiving holes form an included angle greater than 20 degrees and less than 30 degrees.

129. The plate system of claim 126 in which said plate has a length longer than said width, and said lower surface has concave curvature parallel to said length, said concave curvature having a radius of curvature greater than 15 cm and less than 25 cm.

130. The plate system of claim 126 in which said plate has a length longer than said width, and said lower surface has a first concave curvature parallel to said width.

131. The plate system of claim 130 in which said first concave curvature has a radius of curvature in the order of approximately 16 to 21 mm.

132. The plate system of claim 131 in which said lower surface of said plate has a second concave curvature parallel to said length.

133. The plate system of claim 132 wherein said second concave curvature has a radius of curvature greater than 15 cm and less than 25 cm.

134. An anterior cervical plate for engaging at least two vertebral bodies of a human cervical spine along the anterior aspect of the spine, said plate having a length sufficient to span at least two adjacent cervical vertebral bodies, said plate having a lower surface for contacting the cervical vertebral bodies and an upper surface opposite to said lower surface, said plate having a plurality of bone screw receiving holes extending through said plate from said upper surface to said lower surface, at least a first and second of said bone screw receiving holes being associated with a first of the cervical vertebral bodies, and a recess for retaining a locking element for locking bone screws in said bone screw receiving holes, said recess having a central longitudinal axis offset from a transverse line passing through the central longitudinal axes of said first and second bone screw receiving holes, and a locking element movably engageable in said recess, said locking element being movable from at least a first position to a second position, said locking element being configured so as to permit insertion of bone screws into each of said first and second bone screw receiving holes when said locking element is in said first position, said locking element having a head configured to bear against at least a portion of at least one of said bone screws in said first and second bone screw receiving holes when moved to said second position, said head having at least one segment removed therefrom, said removed segment having the same or greater radius of curvature as the radius of curvature of a corresponding one of said bone screw receiving holes.

135. The plate of claim 134 in which said recess has a threaded portion.

136. The plate of claim 134 in which said locking element comprises a threaded portion.

137. The plate of claim 134 in which said locking element comprises a rivet.

138. The plate of claim 134 in which said locking element has a head with at least one segment removed therefrom.

139. The plate of claim 134 in which said locking element is permanently attached to said plate.

140. The plate of claim 134 in which said locking element covers at least a portion of one of said bone screw receiving holes.

141. The plate of claim 134 in which the central longitudinal axes of the bone screw receiving holes of at least one of said pairs of bone screw receiving holes form an included angle of greater than 14 degrees and less than 30 degrees.

142. The plate of claim 134 in which at least a portion of said lower surface comprises a bone ingrowth material.

143. The plate of claim 134 in which at least a portion of said plate is coated with a material to induce the formation of bone.

144. The plate of claim 134 in which said plate comprises bone morphogenetic protein.

145. The plate of claim 134 in which at least a portion of said plate is made of a material which is resorbable.

146. The plate of claim 145 in which said resorbable material is polyglyconate.

147. The plate of claim 145 in which said resorbable material is impregnated with a fusion promoting substance.

148. The plate of claim 134 in which at least a portion of said lower surface is textured so as to promote bone ingrowth.

149. The plate of claim 148 in which said textured portion is impregnated with a fusion promoting substance.

150. The plate of claim 134 in which at least a portion of said lower surface comprises a time released bone growth inducing material.

151. The plate of claim 134 in which at least a portion of said lower surface is roughened to promote the growth of bone along said lower surface.

152. The plate of claim 134 in which at least one end of said plate has means for removably engaging a compression tool.

153. The plate of claim 152 in which said engaging means comprises a depression in said at least one end of said plate.

154. An anterior cervical plate for engaging at least two vertebral bodies of a human cervical spine along the anterior aspect of the spine, said plate having a length sufficient to span at least two adjacent cervical vertebral bodies, said plate having a lower surface for contacting the cervical vertebral bodies and an upper surface opposite to said lower surface, said plate having a plurality of bone screw receiving holes extending through said plate from said upper surface to said lower surface, at least a first and second of said bone screw receiving holes being associated with a first of the cervical vertebrae, and a recess for retaining a locking element for locking bone screws in said bone screw receiving holes, said recess having a central longitudinal axis offset from a transverse line passing through the central longitudinal axes of said first and second bone screw receiving holes, and a locking element movably engageable in said recess, said locking element being movable from at least a first position to a second position, said locking element being configured so as to permit insertion of bone screws into each of said first and second bone screw receiving holes when said locking element is in said first position, said plate having an opening in the side wall of said bone screw receiving holes in communication with the side wall of said recess, said locking element having a plurality of projections to fit within said side wall openings so as to cover a portion of said bone screw receiving hole when said locking element is moved from said position to said second position.

155. The plate of claim 154 in which said recess has a threaded portion.

156. The plate of claim 155 in which said locking element comprises a threaded portion.

157. The plate of claim 154 in which said locking element comprises a rivet.

158. The plate of claim 154 in which said locking element has a head with at least one segment removed therefrom.

159. The plate of claim 154 in which said locking element is permanently attached to said plate.

160. The plate of claim 154 in which said locking element covers at least a portion of one of said bone screw receiving holes.

161. The plate of claim 154 in which the central longitudinal axes of the bone screw receiving holes of at least one of said pairs of bone screw receiving holes form an included angle of greater than 14 degrees and less than 30 degrees.

162. The plate of claim 154 in which at least a portion of said lower surface comprises a bone ingrowth material.

163. The plate of claim 154 in which at least a portion of said plate is coated with a material to induce the formation of bone.

164. The plate of claim 154 in which said plate comprises bone morphogenetic protein.

165. The plate of claim 154 in which at least a portion of said plate is made of a material which is resorbable.

166. The plate of claim 165 in which said resorbable material is polyglyconate.

167. The plate of claim 165 in which said resorbable material is impregnated with a fusion promoting substance.

168. The plate of claim 154 in which at least a portion of said lower surface is textured so as to promote bone ingrowth.

169. The plate of claim 168 in which said textured portion is impregnated with a fusion promoting substance.

170. The plate of claim 154 in which at least a portion of said lower surface comprises a time released bone growth inducing material.

171. The plate of claim 154 in which at least a portion of said lower surface is roughened to promote the growth of bone along said lower surface.

172. The plate of claim 154 in which at least one end of said plate has means for removably engaging a compression tool.

173. The plate of claim 172 in which said engaging means comprises a depression in said at least one end of said plate.