U.S. patent application number 09/754733 was filed with the patent office on 2002-04-18 for anterior cervical plating system, instrumentation, and method of installation.
Invention is credited to Michelson, Gary K..
Application Number | 20020045896 09/754733 |
Document ID | / |
Family ID | 26695760 |
Filed Date | 2002-04-18 |
United States Patent
Application |
20020045896 |
Kind Code |
A1 |
Michelson, Gary K. |
April 18, 2002 |
Anterior cervical plating system, instrumentation, and method of
installation
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.
Inventors: |
Michelson, Gary K.; (Venice,
CA) |
Correspondence
Address: |
MARTIN & FERRARO
14500 AVION PARKWAY
SUITE 300
CHANTILLY
VA
201511101
|
Family ID: |
26695760 |
Appl. No.: |
09/754733 |
Filed: |
January 4, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09754733 |
Jan 4, 2001 |
|
|
|
09022293 |
Feb 11, 1998 |
|
|
|
60037139 |
Feb 11, 1997 |
|
|
|
Current U.S.
Class: |
606/286 ;
606/280; 606/281; 606/289; 606/301; 606/312; 606/317; 606/331;
606/70; 606/71; 606/86B; 606/908 |
Current CPC
Class: |
A61B 17/1671 20130101;
A61B 17/861 20130101; A61B 17/8625 20130101; A61B 17/8695 20130101;
A61B 17/8875 20130101; A61B 2017/0046 20130101; Y10S 606/908
20130101; A61B 17/80 20130101; A61B 17/8033 20130101; A61B
2017/8655 20130101; Y10S 606/907 20130101; A61F 2/0077 20130101;
A61B 17/7059 20130101; Y10S 606/902 20130101; A61B 17/1604
20130101; A61B 17/8042 20130101; A61B 17/1757 20130101; A61B
17/7058 20130101; A61B 17/8019 20130101; A61B 17/8085 20130101;
A61B 17/1728 20130101; A61B 17/863 20130101; Y10S 606/91
20130101 |
Class at
Publication: |
606/61 ; 606/69;
606/70; 606/71 |
International
Class: |
A61B 017/70 |
Claims
What is claimed is:
1. An anterior cervical plate for engaging at least two vertebrae
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 vertebrae, 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,
said plate having at least a first pair of bone screw receiving
holes associated with a first of the adjacent cervical vertebrae
and at least a second pair of bone screw receiving holes associated
with a second of the adjacent cervical vertebrae, said plate having
a length longer than its width, wherein said lower surface of said
plate has a first concave curvature parallel to said length, said
first concave curvature having a radius of curvature between
approximately 20 cm to 24 cm.
2. The plate of claim 1 in which said lower surface has a second
concave curvature transverse to said length parallel to said width,
said second concave curvature having a radius of curvature between
approximately 15 mm to 20 mm.
3. The plate of claim 1 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 one of said lobes.
4. The plate of claim 1 in which said plate has a length longer
than said width.
5. The plate of claim 2 in which said second concave curvature has
a radius of curvature in the order of approximately 16 to 21
mm.
6. The plate of claim 1 in which said plate has a length sufficient
to span at least three consecutive vertebrae.
7. The plate of claim 1 in which said lower surface of said plate
has a complex concave curvature configured to mate with the
vertebral bodies of the at least two vertebrae, 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.
8. The plate of claim 1 futher comprising a plurality of bone
screws each 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 vertebra, each of said bone
screws retainable in a respective one of said bone screw receiving
holes below said upper surface.
9. The plate of claim 8 in which each of said bone screws has a
head dimensioned to achieve an interference fit with a respective
one of said bone screw receiving holes.
10. The plate of claim 8 in which said bone screws are
self-tapping.
11. The plate of claim 8 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.
12. The plate of claim 11 in which said thread of each of said bone
screws has a thin profile and a sharp crest.
13. The plate of claim 8 in which said bone screws are
convergent.
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 lower
surface comprises a bone growth material.
16. 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.
17. The plate of claim 1 in which said plate comprises bone
morphogenetic protein.
18. The plate of claim 1 in which at least a portion of said plate
is made of a material which is resorbable.
19. The plate of claim 18 in which said resorbable material is
polygyconate.
20. The plate of claim 19 in which said resorbable material is
impregnated with a fusion promoting substance.
21. The plate of claim 1 in which at least a portion of said lower
surface is textured so as to promote bone ingrowth.
22. The plate of claim 21 in which said textured portion is
impregnated with a fusion promoting substance.
23. The plate of claim 1 in which at least a portion of said lower
surface comprises a time released bone growth inducing
material.
24. 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.
25. The plate of claim 1 in which said plate includes an aperture
proximate at least one of said bone screw receiving holes.
26. The plate of claim 25 in which said aperture comprises a slot
along the longitudinal axis of said plate.
27. The plate of claim 1 in which at least at one end of said plate
includes means for engaging a compression tool.
28. The plate of claim 27 in which said engaging means comprises a
recess.
29. The plate of claim 28 in which said engaging means comprises a
depression in said at least one end of said plate.
30. An anterior cervical plate for engaging at least two vertebrae
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 vertebrae, a lower surface for contacting the cervical
vertebrae and an upper surface opposite to said lower surface, said
plate having a plurality of paired bone screw receiving holes
extending through said plate from said upper surface to said lower
surface, each pair of said bone screw receiving holes being adapted
to be placed in the same vertebra, said plate having a length
longer than its width, wherein said lower surface of said plate has
a concave radius of curvature parallel to its width 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 to each other in the range of approximately 15
degrees to 30 degrees.
31. The plate of claim 30 in which at least one of said pairs of
bone screw receiving holes form an included angle of approximately
20 degrees.
32. The plate of claim 30 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 less than
approximately 29 degrees and greater than 21 degrees.
33. The plate of claim 30 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.
34. The plate of claim 30 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.
35. The plate of claim 30 in which each bone screw receiving hole
is generally perpendicular to said lower surface of said plate.
36. The plate of claim 30 in which said increased upper portion of
said bone screw receiving holes has a threaded portion.
37. The plate of claim 30 further comprising a thread on the
interior of one of said bone screw receiving holes.
38. The plate of claim 30 in which at least one of said bone screw
receiving holes has means for preventing a bone screw from passing
entirely through said one of bone screw receiving holes.
39. The plate of claim 30 in which at least one of said bone screw
receiving holes has an upper diameter portion and a smaller lower
diameter portion to prevent a bone screw being placed in said one
of bone screw receiving holes from passing entirely through said
one of bone screw receiving holes.
40. The plate of claim 30 in which at least a portion of said lower
surface comprises a bone growth material.
41. The plate of claim 30 in which at least a portion of said plate
is coated with a material to induce the formation of bone.
42. The plate of claim 30 in which said plate comprises bone
morphogenetic protein.
43. The plate of claim 30 in which at least a portion of said plate
is made of a material which is resorbable.
44. The plate of claim 43 in which said resorbable material is
polygyconate.
45. The plate of claim 44 in which said resorbable material is
impregnated with a fusion promoting substance.
46. The plate of claim 30 in which at least a portion of said lower
surface is textured so as to promote bone growth.
47. The plate of claim 46 in which said textured portion is
impregnated with a fusion promoting substance.
48. The plate of claim 30 in which at least a portion of said lower
surface comprises a time released bone growth material.
49. The plate of claim 30 in which at least a portion of said lower
surface is roughened to promote the growth of bone along said lower
surface.
50. The plate of claim 30 in which said plate includes an aperture
between said first end and said second end proximate at least one
of said bone screw receiving holes.
51. The plate of claim 50 in which said aperture comprises a slot
along the longitudinal axis of said plate.
52. The plate of claim 30 in which at least at one end of said
plate includes means for engaging a compression tool.
53. The plate of claim 52 in which said engaging means comprises a
recess.
54. The plate of claim 52 in which said engaging means comprises a
depression in said at least one end of said plate.
55. An anterior cervical plate for engaging a human cervical spine
along the anterior aspect of the spine, said plate having a first
end, a second end, and a length sufficient to span at least three
adjacent cervical vertebrae, said plate having a lower surface for
contacting the adjacent cervical vertebrae and an upper surface
opposite to said lower surface, said plate having at least a first
pair of bone screw receiving holes associated with a first of the
adjacent cervical vertebrae and at least a second pair of bone
screw receiving holes associated with a second of the adjacent
cervical vertebrae, said plate having at least one transverse pair
of intermediate bone screw receiving holes associated with a
cervical vertebrae intermediate the first and second of the
adjacent cervical vertebrae, each of said bone screw receiving
holes extending through said plate from said upper surface to said
lower surface, and said plate having an aperture there through
between said first and second pairs of bone screw receiving holes,
said aperture being associated with the intermediate cervical
vertebrae.
56. The plate of claim 55 in which said plate has a length longer
than said width, and said lower surface has a concave curvature
parallel to said length, said concave curvature having a radius of
curvature greater than 15 cm and less than 25 cm.
57. The plate of claim 55 in which said plate has a length longer
than said width, and said lower surface has a first concave
curvature parallel to said width.
58. The plate of claim 57 in which said first concave curvature has
a radius of curvature in the order of approximately 16 to 21
mm.
59. The plate of claim 55 in which said lower surface of said plate
has a complex concave curvature configured to mate with the
vertebral bodies of the at least two vertebrae, 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.
60. The plate of claim 55 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 one of said lobes.
61. The plate of claim 55 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.
62. The plate of claim 55 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.
63. The plate of claim 55 in which at least a portion of said lower
surface comprises a bone growth material.
64. The plate of claim 55 in which at least a portion of said lower
surface comprises a bone ingrowth material.
65. The plate of claim 55 in which at least a portion of said lower
surface is roughened to promote the growth of bone along said lower
surface.
66. The plate of claim 55 in which at least a portion of said lower
surface comprises a bone growth material.
67. The plate of claim 55 in which at least a portion of said plate
is coated with a material to induce the formation of bone.
68. The plate of claim 55 in which said plate comprises bone
morphogenetic protein.
69. The plate of claim 55 in which at least a portion of said plate
is made of a material which is resorbable.
70. The plate of claim 69 in which said resorbable material is
polygyconate.
71. The plate of claim 69 in which said resorbable material is
impregnated with a fusion promoting substance.
72. The plate of claim 55 in which at least a portion of said lower
surface is textured so as to promote bone ingrowth.
73. The plate of claim 72 in which said textured portion is
impregnated with a fusion promoting substance.
74. The plate of claim 55 in which at least a portion of said lower
surface comprises a time released bone growth inducing
material.
75. The plate of claim 55 in which at least a portion of said lower
surface is roughened to induce the formation of bone along at least
a portion of said lower surface.
76. The plate of claim 55 in which said aperture comprises a slot
along the longitudinal axis of said plate.
77. The plate of claim 55 in which at least at one end of said
plate includes means for engaging a compression tool.
78. The plate of claim 77 in which said engaging means comprises a
recess.
79. An anterior cervical plate for engaging a human cervical spine
along the anterior aspect of the spine, said plate having a length
sufficient to span at least two adjacent cervical vertebrae, said
plate having a lower surface for contacting the cervical vertebrae
and an upper surface opposite to said lower surface, said plate
having at least a first pair of bone screw receiving holes
associated with a first of two adjacent cervical vertebrae and at
least a second pair of bone screw receiving holes associated with a
second of the two adjacent vertebrae, said bone screw receiving
holes extending through said plate from said upper surface to said
lower surface, and at least one end of said plate including a
recess for engaging a compression tool.
80. The plate of claim 79 in which said engaging means comprises a
recess.
81. The plate of claim 79 in which said plate includes an aperture
along a transverse line intermediate said first and said second
pairs of bone screw receiving holes.
82. The plate of claim 79 wherein said plate has a length longer
than said width, and said lower surface has a concave curvature
parallel to said length, said concave curvature having a radius of
curvature greater than 15 mm and less than 25 cm.
83. The plate of claim 79 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 one of said lobes.
84. The plate of claim 79 in which said plate has a length longer
than said width, and said lower surface has a concave curvature
parallel to said width.
85. The plate of claim 84 in which said concave curvature has a
radius of curvature in the order of approximately 16 to 21 mm.
86. The plate of claim 79 in which said plate has a length
sufficient to span at least three consecutive vertebrae.
87. The plate of claim 79 in which said lower surface of said plate
has a complex concave curvature configured to mate with the
vertebral bodies of the at least two vertebrae, 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.
88. The plate of claim 79 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 approximately
20 degrees to 30 degrees.
89. The plate of claim 79 in which the central longitudinal axes of
the bone screw receiving holes of said pairs of bone screw
receiving holes form an included angle of greater than 30
degrees.
90. The plate of claim 79 further comprising at least one bone
screw receiving hole associated with a cervical vertebrae
intermediate the first and second of the adjacent vertebrae.
91. The plate of claim 79 wherein at least a portion of said lower
surface comprises a bone ingrowth material.
92. The plate of claim 79 in which at least a portion of said lower
surface comprises a bone growth material.
93. The plate of claim 79 in which at least a portion of said lower
surface is roughened to promote the growth of bone along said lower
surface.
94. The plate of claim 79 in which at least a portion of said plate
is coated with a material to induce the formation of bone.
95. The plate of claim 79 in which said plate comprises bone
morphogenetic protein.
96. The plate of claim 79 in which at least a portion of said plate
is made of a material which is resorbable.
97. The plate of claim 96 in which said resorbable material is
polygyconate.
98. The plate of claim 96 in which said resorbable material is
impregnated with a fusion promoting substance.
99. The plate of claim 79 in which at least a portion of said lower
surface is textured so as to promote bone ingrowth.
100. The plate of claim 99 in which said textured portion is
impregnated with a fusion promoting substance.
101. The plate of claim 79 in which at least a portion of said
lower surface comprises a time released bone growth inducing
material.
102. An anterior cervical plate for engaging at least two vertebrae
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 vertebrae, a lower surface for contacting the adjacent
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 of said bone screw receiving holes
being associated with a first of the adjacent cervical vertebrae
and at least a second of said bone screw receiving holes being
associated with a second of the adjacent cervical vertebrae, at
least one of said bone screw receiving holes having a recess
associated with and partially offset therefrom, and a locking
element associated with said recess having a head, said locking
element capable of being pre-installed to said plate prior to
insertion of a bone screw into said at least one bone screw hole,
said locking element being movable from a first position to a
second position, said head being configured so as to permit
insertion of bone screws into said bone screw receiving hole
associated with said recess when in said first position and so as
to cover at least a portion of a bone screw inserted in said bone
screw receiving hole associated with said recess when said locking
element is in said second position.
103. The plate of claim 102 in which said locking element has a
bearing surface for bearing against a portion of a bone screw when
said locking element is in said second position.
104. The plate of claim 102 in which said locking element has at
least one camming surface.
105. The plate of claim 102 in which said locking element has at
least one ramped surface.
106. The plate of claim 102 in which said recess has a threaded
portion.
107. The plate of claim 106 in which said locking element comprises
a threaded member.
108. The plate of claim 106 in which said locking element has a
camming surface.
109. The plate of claim 106 in which said locking element has a
ramped surface.
110. The plate of claim 106 in which said locking element comprises
a screw having a head portion and a threaded shaft.
111. The plate of claim 106 in which said head has a camming
surface.
112. The plate of claim 106 in which said head has a ramped portion
surface.
113. The plate of claim 102 in which said locking element comprises
a rivet.
114. The plate of claim 113 in which said rivet has a camming
surface.
115. The plate of claim 113 in which said rivet has a ramped
surface.
116. The plate of claim 102 in which said recess has at least one
camming surface for cooperation with said locking element.
117. The plate of claim 116 in which said locking element has a
camming surface.
118. The plate of claim 102 in which said removed segment is
arcuate and has the same or greater radius of curvature than the
corresponding bone screw receiving hole.
119. The plate of claim 102 further comprising an opening in the
side wall of said bone screw receiving hole in communication with
the side wall of said recess, said locking element having a
projection to fit within said opening 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.
120. The plate of claim 119 in which said projection has a ramped
surface.
121. The plate of claim 102 in which said locking element is
permanently attached to said plate.
122. The plate of claim 102 in which said head has at least one
segment removed therefrom.
123. The plate of claim 102 in which said plate has a length longer
than said width, and said lower surface has a first concave
curvature parallel to said width.
124. The plate of claim 123 in which said first concave curvature
has a radius of curvature in the order of approximately 16 to 21
mm.
125. The plate of claim 102 in which said lower surface of said
plate has a second concave curvature parallel to said length.
126. The plate of claim 125 wherein said second concave curvature
has a radius of curvature greater than 15 cm and less than 25
cm.
127. The plate of claim 102 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 at one of said
lobes.
128. The plate of claim 102 in which said plate has a length
sufficient to span at least three consecutive vertebrae.
129. The plate of claim 102 in which the central axes of said bone
screw receiving holes are perpendicular to said lower surface of
said plate.
130. The plate of claim 102 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.
131. The plate of claim 102 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.
132. The plate of claim 102 in which at least one of said bone
screw receiving holes has means for preventing a bone screw from
passing entirely through said one of bone screw receiving
holes.
133. The plate of claim 102 in which at least one of said bone
screw receiving holes has an upper diameter portion and a smaller
lower diameter portion to prevent a bone screw being placed in said
one of bone screw receiving holes from passing entirely through
said one of bone screw receiving holes.
134. The plate of claim 102 in which at least a portion of said
lower surface comprises a bone ingrowth material.
135. The plate of claim 102 in which at least a portion of said
lower surface comprises a bone growth material.
136. The plate of claim 102 in which at least a portion of said
lower surface is roughened to promote the growth of bone along said
lower surface.
137. The plate of claim 102 in which at least a portion of said
plate is coated with a material to induce the formation of
bone.
138. The plate of claim 102 in which said plate comprises bone
morphogenetic protein.
139. The plate of claim 102 in which at least a portion of said
plate is made of a material which is resorbable.
140. The plate of claim 139 in which said resorbable material is
polygyconate.
141. The plate of claim 139 in which said resorbable material is
impregnated with a fusion promoting substance.
142. The plate of claim 102 in which at least a portion of said
lower surface is textured so as to promote bone ingrowth.
143. The plate of claim 142 in which said textured portion is
impregnated with a fusion promoting substance.
144. The plate of claim 102 in which at least a portion of said
lower surface comprises a time released bone growth inducing
material.
145. The plate of claim 102 in which at least one end of said plate
has a means for removably engaging a compression tool.
146. The plate of claim 145 in which said engaging means comprises
a depression in said at least one end of said plate.
147. An anterior cervical plate system for engaging at least two
vertebrae of a human cervical spine along the anterior aspect of
the spine, said system comprising: a plate having a length
sufficient to span at least two adjacent cervical vertebrae, 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
one of said bone screw receiving holes being associated with a
first of the adjacent vertebrae and at least a second of said bone
screw receiving holes being associated with a second of the
adjacent vertebrae, said bone screw receiving holes each having an
offset recess for receiving a locking element; a plurality of bone
screws each 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 vertebra, each of said bone
screws retainable in a respective one of said bone screw receiving
holes; and a plurality of locking elements each engageable in a
respective one of said offset recesses associated with said bone
screw receiving holes, said plurality of locking elements each
being configured to lock one of said bone screws to said plate by
covering at least a portion of one of said bone screw receiving
holes below said upper surface.
148. The plate system of claim 147 in which said locking element
has a bearing surface for bearing against a portion of a bone screw
when said locking element is in said second position.
149. The plate system of claim 147 in which said locking element
has a camming surface.
150. The plate system of claim 147 in which said locking element
has a ramped surface.
151. The plate system of claim 147 in which said recess has a
threaded portion.
152. The plate system of claim 151 in which said locking element
comprises a threaded portion.
153. The plate system of claim 152 in which said locking element
has a camming surface.
154. The plate system of claim 152 in which said locking element
has a ramped surface.
155. The plate system of claim 151 in which said locking element
comprises a screw having a head portion and a threaded shaft.
156. The plate system of claim 155 in which said screw has a
camming surface.
157. The plate system of claim 155 in which said screw has a ramped
surface.
158. The plate system of claim 147 in which said locking element
comprises a rivet.
159. The plate system of claim 158 in which said rivet has a
camming surface.
160. The plate system of claim 158 in which said rivet has a ramped
surface.
161. The plate system of claim 147 in which said recess has at
least one camming surface for cooperation with said locking
element.
162. The plate system of claim 161 in which said locking element
has a camming surface.
163. The plate system of claim 147 in which said locking element
has a removed segment that is arcuate and has the same or greater
radius of curvature than the corresponding bone screw receiving
hole.
164. The plate system of claim 147 further comprising an opening in
the side wall of one of said bone screw receiving hole in
communication with the side wall of said recess, said locking
element having a projection adapted to fit within said side wall
opening so as to cover a portion of said one of said bone screw
receiving hole when said locking element is moved from a first
position to a second position.
165. The plate system of claim 164 in which said projection has a
ramped surface.
166. The plate system of claim 147 in which said locking element is
permanently attached to said plate.
167. The plate system of claim 147 in which at least one end of
said plate has a means for removably engaging a compression
tool.
168. The plate system of claim 167 in which said engaging means
comprises a depression in said at least one end of said plate.
169. The plate system of claim 147 in which said recess for
receiving a locking element comprises a thread on the interior of
at least one of said bone screw receiving holes.
170. The plate system of claim 147 in which said locking element
covers at least a portion said bone screw receiving hole when
placed in said recess.
171. The plate system of claim 147 in which said plate has a width
and length longer than said width, and said lower surface has a
first concave curvature parallel to said width.
172. The plate system of claim 171 in which said first concave
curvature has a radius of curvature of the order of approximately
16-21 mm.
173. The plate system of claim 171 in which said lower surface of
said plate has a second concave curvature parallel to said
length.
174. The plate system of claim 173 in which said second concave
curvature has a radius of curvature greater than 15 cm and less
than 25 cm.
175. The plate system of claim 147 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 located within the circumference of said
lobes.
176. The plate system of claim 147 in which said plate has a length
sufficient to span at least three consecutive vertebrae.
177. The plate system of claim 147 in which the central axes of
said bone screw receiving holes are perpendicular to said lower
surface of said plate.
178. The plate system of claim 147 in which each of said bone
screws have a head dimensioned to achieve an interference fit with
a respective one of said bone screw receiving holes.
179. The plate system of claim 147 in which said bone screw and
said locking element have heads with means for engaging a tool for
rotating said bone screws and said locking element.
180. The plate system of claim 147 in which each of said bone
screws has a head and a first irregular depression in the top of
said head, and said locking element has a head portion and a second
irregular depression in said head, both of said first and second
depressions having the same cross section.
181. The plate system of claim 147 in which each of said bone
screws are self-tapping.
182. The plate system of claim 147 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.
183. The plate system of claim 182 in which said thread of each of
said bone screws has a thin profile and a sharp crest.
184. The plate system of claim 147 in which said bone screws and
said locking element do not project above the upper surface of said
plate when said plate is installed.
185. The plate system of claim 147 in which at least one of said
bone screw receiving holes has means for preventing a bone screw
from passing through said bone screw receiving hole.
186. The plate system of claim 147 in which each of said bone screw
receiving holes 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.
187. The plate system of claim 147 in which at least a portion of
said lower surface comprises a bone growth material.
188. The plate system of claim 147 in which at least a portion of
said plate is coated with a material to induce the formation of
bone.
189. The plate system of claim 147 in which said plate comprises
bone morphogenetic protein.
190. The plate system of claim 147 in which at least a portion of
said plate is made of a material which is resorbable.
191. The plate system of claim 190 in which said resorbable
material is polygyconate.
192. The plate system of claim 190 in which said resorbable
material is impregnated with a fusion promoting substance.
193. The plate system of claim 147 in which at least a portion of
said lower surface is textured so as to induce bone ingrowth.
194. The plate system of claim 193 in which said textured portion
is impregnated with a fusion promoting substance.
195. The plate system of claim 147 in which at least a portion of
said lower surface comprises a time released bone growth inducing
material.
196. The plate system of claim 147 in which at least a portion of
said lower surface is roughened to promote the growth of bone along
said lower surface.
197. The plate system of claim 147 in which at least one end of
said plate has means for removably engaging the first end of a
compression tool.
198. The plate system of claim 197 in which said engaging means
comprises a depression in said at least one end of said plate.
199. The plate system of claim 197 in which said opening comprises
a longitudinal slot along the longitudinal axis of said plate.
200. An anterior cervical plate for engaging at least two vertebrae
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 vertebrae, a lower surface for contacting the cervical
vertebrae, and an upper surface opposite to said lower surface; a
plurality of bone screw receiving holes associated with at least a
first and a second of the adjacent vertebrae, said plurality of
bone screw receiving holes extending through said plate from said
upper surface to said lower surface, at least one of said plurality
of bone screw receiving holes having a reduced diameter lower
portion and an increased diameter upper portion proximate said
upper surface; and a locking element engageable in said increased
diameter upper portion of one of said bone screw receiving holes to
lock one of said bone screws to said plate, said locking element
adapted to bear against one of said bone screws when in one of said
bone screw receiving holes.
201. The plate of claim 200 in which said locking element is
coaxially engageable to one of said bone screw receiving holes.
202. The plate of claim 200 in which said plate has a length longer
than said width, and said lower surface has a first concave
curvature parallel to said width.
203. The plate of claim 202 in which said first concave curvature
has a radius of curvature in the order of approximately 16-21
mm.
204. The plate of claim 200 in which said lower surface of said
plate has a second concave curvature parallel to said length.
205. The plate of claim 204 in which said second concave curvature
has a radius of curvature greater than approximately 15 cm and less
than approximately 25 cm.
206. The plate of claim 200 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 said lobes.
207. The plate of claim 200 in which said lower surface of said
plate has a complex concave curvature configured to mate with the
vertebral bodies of the at least two vertebrae, 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.
208. The plate of claim 200 in which said increased upper portion
of said bone screw receiving holes has a threaded portion.
209. The plate of claim 200 further comprising a thread on the
interior of one of said bone screw receiving hole.
210. The plate of claim 200 in which at least one of said bone
screw receiving holes has means for preventing a bone screw from
passing entirely through said one of bone screw receiving
holes.
211. The plate of claim 200 in which at least one of said bone
screw receiving holes has an upper diameter portion and a smaller
lower diameter portion to prevent a bone screw being placed in said
one of bone screw receiving holes from passing entirely through
said one of bone screw receiving holes.
212. The plate of claim 200 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.
213. The plate of claim 200 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.
214. The plate of claim 200 in which said locking element comprises
a cap.
215. The plate of claim 200 in which said locking element covers at
least a portion of one of said bone screw receiving holes.
216. The plate of claim 200 in which each of said bone screws have
a head dimensioned to achieve an interference fit with a respective
one of said bone screw receiving holes.
217. The plate of claim 200 in which said bone screws and said
locking element each have a head with means for engagement by the
same tool for rotating said bone screw and said locking
element.
218. The plate of claim 200 in which each of said bone screws has a
head with an irregular depression in the top of said head and said
locking element has a head portion with an irregular depression,
both of said depressions having the same cross sectional area.
219. The plate of claim 200 in which each of said bone screws is a
self-tapping screw.
220. The plate of claim 200 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 most of the length of said shank.
221. The plate of claim 220 in which said thread of each of said
bone screws has a thin profile and a sharp crest.
222. The plate of claim 200 in which said bone screws and said
locking element do not project above the upper surface of said
plate when said plate is installed.
223. The plate of claim 200 in which the central axes of said bone
screw receiving holes are perpendicular to said lower surface of
said plate.
224. The plate of claim 200 in which said plate has a length
sufficient to span at least three consecutive cervical
vertebrae.
225. The plate of claim 200 in which said bone screws are
convergent.
226. The plate of claim 200 in which at least a portion of said
lower surface comprises a bone growth material.
227. The plate of claim 200 in which at least a portion of said
lower surface comprises a bone ingrowth material.
228. The plate of claim 200 in which at least a portion of said
plate is coated with a material to induce the formation of
bone.
229. The plate of claim 200 in which said plate comprises bone
morphogenetic protein.
230. The plate of claim 200 in which at least a portion of said
plate is made of a material which is resorbable.
231. The plate of claim 200 in which said resorbable material is
polygyconate.
232. The plate of claim 230 in which said resorbable material is
impregnated with a fusion promoting substance.
233. The plate of claim 200 in which at least a portion of said
lower surface is textured so as to induce bone ingrowth.
234. The plate of claim 233 in which said textured portion is
impregnated with a fusion promoting substance.
235. The plate of claim 200 in which at least a portion of said
lower surface comprises a time released bone growth inducing
material.
236. The plate of claim 200 in which at least a portion of said
lower surface is roughened to promote the growth of bone along said
lower surface.
237. The plate of claim 200 in which said plate includes an
aperture between said first end and said second end proximate at
least one of said bone screw receiving holes.
238. The plate of claim 237 in which said aperture comprises a slot
along the longitudinal axis of said plate.
239. The plate of claim 200 in which at least one end of said plate
has means for removably engaging the first end of a compression
tool.
240. The plate of claim 239 in which said engaging means comprises
a depression in said at least one end of said plate.
241. An anterior cervical plate system for engaging at least two
vertebrae of a human cervical spine along the anterior aspect of
the spine, said system comprising: a plate having a length
sufficient to span at least two adjacent cervical vertebrae, a
lower surface for contacting the adjacent cervical vertebrae, and
an upper surface opposite to said lower surface; a plurality of
bone screw receiving holes associated with at least a first and a
second of the adjacent cervical vertebrae, said plurality of bone
screw receiving holes extending through said plate from said upper
surface to said lower surface, at least one of said plurality of
bone screw receiving holes having a reduced diameter lower portion
and an increased diameter upper portion proximate said upper
surface; a plurality of bone screws each having a longitudinal axis
for insertion into a respective one of said plurality of bone screw
receiving holes in a direction from said upper surface to said
lower surface and having a head for engaging said plate below said
upper surface to secure said plate to a vertebra; and a locking
element engageable in said increased diameter upper portion of one
of said bone screw receiving holes to lock one of said bone screws
to said plate.
242. The plate system of claim 241 in which said recess has a
threaded portion.
243. The plate system of claim 241 in which said locking element
comprises a cap.
244. The plate system of claim 241 in which said locking element
covers at least a portion of one of said bone screw receiving
holes.
245. The plate system of claim 241 in which said locking element is
coaxially engageable to one of said bone screw receiving holes.
246. The plate system of claim 241 in which said plate has a length
sufficient to span at least three consecutive cervical
vertebrae.
247. The plate system of claim 245 in which said plate includes an
aperture between said first end and said second end proximate at
least one of said bone screw receiving holes.
248. The plate system of claim 247 in which said aperture comprises
a slot along the longitudinal axis of said plate.
249. The plate system of claim 241 in which said plate has a length
longer than said width, and said lower surface has a concave
curvature parallel to said width.
250. The plate system of claim 249 in which said concave curvature
has a radius of curvature in the order of approximately about 16-21
mm.
251. The plate system of claim 241 in which said lower surface of
said plate has a concave curvature parallel to said length.
252. The plate system of claim 251 in which said concave curvature
has a radius of curvature approximately 15 cm and less than
approximately 25 cm.
253. The plate system of claim 241 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 said
lobes.
254. The plate system of claim 241 in which said lower surface of
said plate has a complex concave curvature configured to mate with
the vertebral bodies of the at least two vertebrae, 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.
255. The plate system of claim 241 in which each of said bone
screws have a head dimensioned to achieve an interference fit with
a respective one of said bone screw receiving holes.
256. The plate system of claim 241 in which said bone screws and
said locking element each have a head with means for engagement by
the same tool for rotating said bone screw and said locking
element.
257. The plate system of claim 241 in which each of said bone
screws has a head with an irregular depression in the top of said
head and said locking element has a head portion with an irregular
depression, both of said depressions having the same cross
sectional area.
258. The plate system of claim 241 in which each of said bone
screws is a self-tapping screw.
259. The plate system of claim 241 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 most of the length of said shank.
260. The plate system of claim 259 in which said thread of each of
said bone screws has a thin profile and a sharp crest.
261. The plate system of claim 241 in which said bone screws are
convergent.
262. The plate system of claim 241 in which said bone screws and
said locking element do not project above the upper surface of said
plate when said plate is installed.
263. The plate system of claim 241 in which said increased diameter
upper portion for retaining a locking element comprises a thread on
the interior of one of said bone screw receiving hole.
264. The plate system of claim 241 in which at least one of said
bone screw receiving holes has means for preventing a bone screw
from passing entirely through said one of bone screw receiving
holes.
265. The plate system of claim 241 in which at least one of said
bone screw receiving holes has an upper diameter portion and a
smaller lower diameter portion to prevent a bone screw being placed
in said one of bone screw receiving holes from passing entirely
through said one of bone screw receiving holes.
266. The plate system of claim 241 in which the central axes of
said bone screw receiving holes are perpendicular to said lower
surface of said plate.
267. The plate system of claim 241 in which at least a portion of
said lower surface comprises a bone ingrowth material.
268. The plate system of claim 241 in which at least a portion of
said lower surface comprises a bone growth material.
269. The plate system of claim 241 in which at least a portion of
said plate is coated with a material to induce the formation of
bone.
270. The plate system of claim 241 in which said plate comprises
bone morphogenetic protein.
271. The plate system of claim 241 in which at least a portion of
said plate is made of a material which is resorbable.
272. The plate system of claim 271 in which said resorbable
material is polygyconate.
273. The plate system of claim 271 in which said resorbable
material is impregnated with a fusion promoting substance.
274. The plate system of claim 241 in which at least a portion of
said lower surface is textured so as to induce bone ingrowth.
275. The plate system of claim 274 in which said textured portion
is impregnated with a fusion promoting substance.
276. The plate system of claim 241 in which at least a portion of
said lower surface comprises a time released bone growth inducing
material.
277. The plate of claim 241 in which at least a portion of said
lower surface is roughened to promote the growth of bone along said
lower surface.
278. The plate system of claim 241 in which said plate includes an
aperture between said first end and said second end proximate at
least one of said bone screw receiving holes.
279. The plate system of claim 278 in which said aperture comprises
a slot along the longitudinal axis of said plate.
280. The plate system of claim 241 in which at least one end of
said plate has means for removably engaging the first end of a
compression tool.
281. The plate system of claim 280 in which said engaging means
comprises a depression in said at least one end of said plate.
282. An anterior cervical plate system for engaging at least three
vertebrae of a human cervical spine along the anterior aspect of
the spine, said device 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
vertebrae, 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 vertebrae 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 and having a reduced diameter portion
near 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 corresponding to a first of
the adjacent vertebrae, a second pair of said bone screw receiving
holes corresponding to a second of the adjacent vertebrae, and a
third pair of said bone screw receiving holes corresponding to a
third of the adjacent vertebrae; and a plurality of locking
elements for locking a bone screw placed in said bone screw
receiving holes, each of said plurality of locking elements
coaxially engageable in a respective one of said bone screw
receiving holes to lock a bone screw to said plate, each of said
locking elements having a bottom surface and a top surface with a
depression for engaging a tool used to lock and unlock said locking
element to said plate, said bottom surface configured to fit over
the bone screw and bear against the bone screw.
283. The plate system of claim 282 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.
284. The plate system of claim 282 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.
285. The plate system of claim 282 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.
286. The plate system of claim 282 in which said plate has a length
longer than said width, and said lower surface has a first concave
curvature parallel to said width.
287. The plate system of claim 282 in which said first concave
curvature has a radius of curvature in the order of approximately
16 to 21 mm.
288. The plate system of claim 287 in which said lower surface of
said plate has a second concave curvature parallel to said
length.
289. The plate system of claim 288 wherein said second concave
curvature has a radius of curvature greater than 15 cm and less
than 25 cm.
290. The plate system of claim 282 in which said locking element
comprises a cap.
291. An anterior cervical plating system for engaging at least
three vertebrae of a human cervical spine along the anterior aspect
of the spine, said device 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
vertebrae, 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 vertebrae 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 and having a reduced diameter portion
near 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 corresponding to a first of
the adjacent vertebrae, a second pair of said bone screw receiving
holes corresponding to a second of the adjacent vertebrae, and a
third pair of bone screw receiving holes corresponding to a third
of the adjacent vertebrae, each of said bone screw receiving holes
having an offset recess for receiving a locking element; and a
plurality of locking elements for locking a bone screw placed in
said bone screw receiving hole, each of said plurality of locking
elements engageable in a respective one of said offset recesses to
lock a bone screw to said plate, each of said locking elements
having a bottom surface and a top surface with a depression for
engaging a tool used to lock and unlock said locking element to
said plate, said bottom surface configured to fit over the bone
screw and bear against the bone screw.
292. The plate system of claim 291 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.
293. The plate system of claim 291 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.
294. The plate system of claim 291 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.
295. The plate system of claim 291 in which said plate has a length
longer than said width, and said lower surface has a first concave
curvature parallel to said width.
296. The plate system of claim 295 in which said first concave
curvature has a radius of curvature in the order of approximately
16 to 21 mm.
297. The plate system of claim 296 in which said lower surface of
said plate has a second concave curvature parallel to said
length.
298. The plate system of claim 297 wherein said second concave
curvature has a radius of curvature greater than 15 cm and less
than 25 cm.
299. An anterior cervical plate for engaging at least two vertebrae
of a human cervical spine along the anterior aspect of the spine,
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 vertebrae, 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.
300. The plate of claim 299 further comprising at least a third
bone screw receiving hole corresponding to the area between the
first and second cervical vertebrae, and said recess being
associated with said first and second bone screw receiving holes
and with said third bone screw receiving hole.
301. The plate of claim 300 in which said recess overlaps a portion
of said first bone screw receiving hole and said third bone screw
receiving hole.
302. The plate of claim 299 in which said recess overlaps a portion
of at least four bone screw receiving holes.
303. The plate of claim 299 in which said plate has a length longer
than said width, and said lower surface has a first concave
curvature parallel to said width.
304. The plate of claim 303 in which said first concave curvature
has a radius of curvature in the order of approximately 16 to 21
mm.
305. The plate of claim 299 in which said lower surface of said
plate has a second concave curvature parallel to said length.
306. The plate of claim 305 wherein said second concave curvature
has a radius of curvature greater than 15 cm and less than 25
cm.
307. The plate of claim 299 in which said plate has a length
sufficient to span at least three consecutive vertebrae.
308. The plate of claim 299 in which said lower surface of said
plate has a complex concave curvature configured to mate with the
vertebral bodies of the at least two vertebrae, 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.
309. The plate of claim 299 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.
310. The plate of claim 299 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.
311. The plate of claim 299 in which at least a portion of said
lower surface comprises a bone growth material.
312. The plate of claim 299 in which at least a portion of said
lower surface comprises a bone ingrowth material.
313. The plate of claim 299 in which at least a portion of said
plate is coated with a material to induce the formation of
bone.
314. The plate of claim 299 in which said plate comprises bone
morphogenetic protein.
315. The plate of claim 299 in which at least a portion of said
plate is made of a material which is resorbable.
316. The plate of claim 315 in which said resorbable material is
polygyconate.
317. The plate of claim 315 in which said resorbable material is
impregnated with a fusion promoting substance.
318. The plate of claim 299 in which at least a portion of said
lower surface is textured so as to promote bone ingrowth.
319. The plate of claim 318 in which said textured portion is
impregnated with a fusion promoting substance.
320. The plate of claim 299 in which at least a portion of said
lower surface comprises a time released bone growth inducing
material.
321. The plate of claim 299 in which at least a portion of said
lower surface is roughened to promote the growth of bone along said
lower surface.
322. The plate of claim 299 in which said aperture comprises a slot
along the longitudinal axis of said plate.
323. The plate of claim 299 in which at least at one end of said
plate includes means for engaging a compression tool.
324. The plate of claim 323 in which said engaging means comprises
a recess.
325. The plate of claim 323 in which said engaging means comprises
a depression in said at least one end of said plate.
326. An anterior cervical plate for engaging at least two vertebrae
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 vertebrae, 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 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 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 in said first
position, and said head bearing 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.
327. The plate of claim 326 in which said locking element has a
bearing surface for bearing against a bone screw.
328. The plate of claim 326 in which said locking element has a
camming surface.
329. The plate of claim 326 in which said locking element has a
ramped surface.
330. The plate of claim 326 in which said recess has a threaded
portion.
331. The plate of claim 330 in which said locking element comprises
a threaded portion.
332. The plate of claim 330 in which said locking element has a
camming surface.
333. The plate of claim 330 in which said locking element has a
ramped surface.
334. The plate of claim 330 in which said locking element comprises
a screw having a head portion and a threaded shaft.
335. The plate of claim 330 in which said locking element has a
camming surface.
336. The plate of claim 330 in which said locking element has a
ramped surface.
337. The plate of claim 326 in which said locking element comprises
a rivet.
338. The plate of claim 337 in which said rivet has a camming
surface.
339. The plate of claim 337 in which said rivet has a ramped
surface.
340. The plate of claim 326 in which said recess has at least one
camming surface for cooperation with said locking element.
341. The plate of claim 326 in which said head has at least one
segment removed therefrom.
342. The plate of claim 341 in which said removed segment has the
same or greater radius of curvature as the corresponding bone screw
receiving holes.
343. The plate of claim 326 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 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.
344. The plate of claim 343 in which said projections have a ramped
surface.
345. The plate of claim 326 in which said locking element is
permanently attached to said plate.
346. The plate of claim 326 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.
347. The plate of claim 326 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.
348. The plate of claim 326 in which said locking element covers at
least a portion said bone screw receiving hole when placed in said
recess.
349. The plate of claim 326 in which said locking element covers at
least a portion of one of said bone screw receiving holes.
350. The plate of claim 326 in which said plate has a length longer
than said width, and said lower surface has a first concave
curvature parallel to said width.
351. The plate of claim 350 in which said first concave curvature
has a radius of curvature of the order of approximately 16-21
mm.
352. The plate of claim 326 in which said lower surface of said
plate has a second concave curvature parallel to said length.
353. The plate of claim 352 in which said second concave curvature
has a radius of curvature greater than approximately 15 cm and less
than approximately 25 cm.
354. The plate of claim 326 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 said lobes.
355. The plate of claim 326 in which said plate has a length
sufficient to span at least three consecutive vertebrae.
356. The plate of claim 326 in which the central axes of said bone
screw receiving holes are perpendicular to said lower surface of
said plate.
357. The plate of claim 326 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.
358. The plate of claim 326 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.
359. The plate of claim 326 in which at least a portion of said
lower surface comprises a bone ingrowth material.
360. The plate of claim 326 in which at least a portion of said
lower surface comprises a bone growth material.
361. The plate of claim 326 in which at least a portion of said
plate is coated with a material to induce the formation of
bone.
362. The plate of claim 326 in which said plate comprises bone
morphogenetic protein.
363. The plate of claim 326 in which at least a portion of said
plate is made of a material which is resorbable.
364. The plate of claim 363 in which said resorbable material is
polygyconate.
365. The plate of claim 363 in which said resorbable material is
impregnated with a fusion promoting substance.
366. The plate of claim 326 in which at least a portion of said
lower surface is textured so as to promote bone ingrowth.
367. The plate of claim 366 in which said textured portion is
impregnated with a fusion promoting substance.
368. The plate of claim 326 in which at least a portion of said
lower surface comprises a time released bone growth inducing
material.
369. The plate of claim 326 in which at least a portion of said
lower surface is roughened to promote the growth of bone along said
lower surface.
370. The plate of claim 326 in which at least one end of said plate
has means for removably engaging a compression tool.
371. The plate of claim 370 in which said engaging means comprises
a depression at least one end of said plate.
372. The plate of claim 326 in which said plate includes an opening
proximate said second bone screw receiving holes associated with
said second adjacent vertebrae.
373. The plate of claim 372 in which said opening comprises a slot
along the longitudinal axis of said plate.
374. An anterior cervical plate for engaging at least two vertebrae
of a human cervical spine along the anterior aspect of the spine,
said device comprising: a plate having a first end, a second end,
and a length sufficient to span at least two adjacent cervical
vertebrae, 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 adjacent
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 having a head and being movable from at least a first
position to a second position, said head having a configuration so
as to permit insertion of bone screws into said first and said
second bone screw receiving holes 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 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
vertebra.
375. The plate of claim 374 in which said locking element has a
bearing surface for bearing against a bone screw.
376. The plate of claim 374 in which said locking element has a
camming surface.
377. The plate of claim 374 in which said locking element has a
ramped surface.
378. The plate of claim 374 in which said recess has a threaded
portion.
379. The plate of claim 378 in which said locking element comprises
a threaded portion.
380. The plate of claim 378 in which said locking element has a
camming surface.
381. The plate of claim 374 in which said locking element has a
ramped surface.
382. The plate of claim 378 in which said locking element has a
head portion and a threaded shaft.
383. The plate of claim 382 in which said locking element has a
camming surface.
384. The plate of claim 382 in which said locking element has a
ramped portion surface.
385. The plate of claim 382 in which said locking element is a
rivet.
386. The plate of claim 385 in which said rivet has a camming
surface.
387. The plate of claim 385 in which said rivet has a ramped
surface.
388. The plate of claim 374 in which said recess has at least one
camming surface for cooperation with said locking element.
389. The plate of claim 374 in which said locking element has at
least two segments removed therefrom, said removed segments being
arcuate and have the same or greater radius of curvature than a
corresponding bone screw receiving holes.
390. The plate of claim 374 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 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.
391. The plate of claim 390 in which said projections have a ramped
surface.
392. The plate of claim 374 in which said locking element is
permanently attached to said plate.
393. The plate of claim 374 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.
394. The plate of claim 374 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.
395. The plate of claim 374 in which said locking element covers at
least one of said bone screw receiving holes.
396. The plate of claim 374 wherein said plate has a length longer
than said width, and said lower surface has a first concave
curvature parallel to said width.
397. The plate of claim 396 wherein said first concave curvature
has a first radius of curvature of approximately about 16-21
mm.
398. The plate of claim 397 wherein said lower surface of said
plate has a second concave curvature parallel to said length.
399. The plate of claim 398 wherein said second concave curvature
has a radius of curvature greater than approximately 15 cm and less
than approximately 25 cm.
400. The plate of claim 374 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 said
lobes.
401. The plate of claim 374 in which said plate has a length
sufficient to span at least three consecutive vertebrae.
402. The plate of claim 374 in which the central axes of said bone
screw receiving holes are perpendicular to said lower surface of
said plate.
403. The plate of claim 374 further comprising a plurality of bone
screws each having a head dimensioned to achieve an interference
fit with a respective one of said bone screw receiving holes.
404. The plate of claim 403 in which said bone screw and said
locking element have heads with means for engagement by the same
tool for rotating said bone screw and said locking element.
405. The plate of claim 403 in which said bone screw 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.
406. The plate of claim 403 in which each of said bone screws is a
self-tapping screw.
407. The plate of claim 403 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.
408. The plate of claim 407 in which said thread of each of said
bone screws has a thin profile and a sharp crest.
409. The plate of claim 403 in which said bone screws and said
locking element do not project above the upper surface of said
plate when said plate is installed.
410. The plate of claim 374 in which said recess includes a thread
on the interior of said bone screw receiving hole.
411. The plate of claim 374 in which said bone screw receiving hole
has means for preventing a bone screw from passing through said
bone screw receiving hole.
412. The plate of claim 374 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.
413. The plate of claim 374 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.
414. The plate of claim 374 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.
415. The plate of claim 374 wherein at least a portion of said
lower surface comprises a bone ingrowth material.
416. The plate of claim 374 in which at least a portion of said
lower surface comprises a bone growth material.
417. The plate of claim 374 in which at least a portion of said
plate is made of a material which is resorbable.
418. The plate of claim 417 in which said resorbable material is
polygyconate.
419. The plate of claim 417 in which said resorbable material is
impregnated with a fusion promoting substance.
420. The plate of claim 374 in which at least a portion of said
lower surface is textured.
421. The plate of claim 420 in which said textured portion is
impregnated with a fusion promoting substance.
422. The plate of claim 374 in which at least a portion of said
lower surface comprises a time released bone growth material.
423. The plate of claim 374 in which at least one of said ends of
said plate has means for removably engaging a compression tool.
424. The plate of claim 423 in which said engaging means comprises
a depression in said at least one end of said plate.
425. The plate of claim 374 in which said plate includes an opening
proximate said second bone screw receiving hole associated with
said second adjacent vertebrae.
426. The plate of claim 425 in which said opening comprises a slot
along the longitudinal axis of said plate.
427. An anterior cervical plating system for engaging at least
three vertebrae of a human cervical spine along the anterior aspect
of the spine, said device 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
vertebrae, 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 vertebrae 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 vertebrae, a second pair of said bone screw
receiving holes corresponding to a second of the adjacent
vertebrae, and a third pair of said bone screw receiving holes
corresponding to a third of the adjacent vertebrae; 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; a locking element positioned in said locking
element 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.
428. The plate system of claim 427 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.
429. The plate system of claim 427 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.
430. The plate system of claim 427 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.
431. The plate system of claim 427 in which said plate has a length
longer than said width, and said lower surface has a first concave
curvature parallel to said width.
432. The plate system of claim 431 in which said first concave
curvature has a radius of curvature in the order of approximately
16 to 21 mm.
433. The plate system of claim 432 in which said lower surface of
said plate has a second concave curvature parallel to said
length.
434. The plate system of claim 433 wherein said second concave
curvature has a radius of curvature greater than 15 cm and less
than 25 cm.
435. A method for joining adjacent vertebrae of the anterior
cervical spine together with a plating system composed of a plate
having a plurality of bone screw receiving holes and a plurality of
bone screws each securable in a vertebra through a respective one
of the bone screw receiving holes, said method comprising the steps
of: forming a pilot hole in a vertebra by driving a sharp-ended
tool into the bone of the vertebra to create a pilot hole whereby
the bone material displaced by said sharp-ended tool is driven into
the vertebrae and not substantially removed; and inserting a bone
screw into the pilot hole through the respective bone screw
receiving hole of the plate to attach the plate to the
vertebrae.
436. The method of claim 435 in which said pilot hole forming step
includes th sub-step of driving said sharp-ended tool to a final
depth which is short of the posterior cortex of the vertebra.
437. The method of claim 436 further comprising the step of
positioning the plate on the vertebra, and said step of forming the
pilot hole includes the sub-step of driving the sharp-ended tool
through a bone screw receiving hole in the plate.
438. The method of claim 437 further comprising the step of
engageably aligning said sharp-ended tool to a bone screw receiving
hole in the plate.
439. The method of claim 437 in which the inserting step includes
the sub-step of screwing a bone screw into the pilot hole through
the bone screw receiving holes of the plate.
440. The method of claim 439 in which the inserting step includes
utilizing a self-tapping screw.
441. The method of claim 440 further comprising the step of locking
the bone screw to the plate after the bone screw is screwed into
said vertebrae.
442. The method of claim 435 in which the forming step includes the
sub-step of utilizing a sharp ended tool contained within a housing
and said housing is attached to said plate prior to being driven
into said vertebrae.
443. The method of claim 442 in which the forming step includes the
sub-step of driving said sharp ended tool into said vertebrae
coaxial with the bone screw receiving holes of the plate.
444. The method of claim 435 further comprising the step of
rotating said sharp-ended tool.
445. A method for joining at least two adjacent cervical vertebrae
together anteriorly with a plating system comprising a plate having
a length sufficient for contacting the two adjacent cervical
vertebrae and having a plurality of bone screw receiving holes and
a plurality of bone screws each securable in a respective vertebra
through a respective one of the bone screw receiving holes, said
method comprising the steps of: positioning said plate so as to
align at least a transverse pair of the bone screw receiving holes
with each of the adjacent vertebrae; attaching said plate to a
first of at least one of the two adjacent vertebrae; compressing
the space between two adjacent vertebrae; and attaching the plate
to the second of the two vertebrae.
446. The method of claim 445 in which the compressing step
includes: securing an engaging post to a second vertebrae; applying
the first arm of a compression tool having a first arm and a second
arm and means for moving said first and said second arm towards one
another to said engaging post and said second arm to a portion of
said plate attached to the first of the vertebrae; and applying a
compression force to the space between said two adjacent vertebrae
by moving said first arm towards said second arm.
447. The method of claim 446 in which said engaging post is a
sharpened rod and said sharpened rod is secured to the second
adjacent vertebrae by embedding the sharpened rod into the second
vertebrae to a depth less than the depth of the body of the second
vertebrae.
448. The method of claim 446 in which said vertebral body engaging
post is driven to a final depth which is short of the posterior
cortex of the respective vertebra.
449. The method of claim 446 in which the engaging post is
installed through an opening in the plate intermediate the ends of
the plate and alignable with the second vertebrae.
450. The method of claim 446 in which the compression tool is
attached to the vertebral body engaging post and to the plate.
451. A method for compressing two adjacent vertebral bodies with a
plate comprising the steps of: engaging the plate with a first arm
of a compression tool; engaging the spine with a vertebral body
penetrating member affixed to a second arm of said compression
apparatus; and utilizing said compression apparatus to shorten the
distance between said first and second arms.
452. The method of claim 451 in which said plate engaging step
includes the substeps of: engaging said first arm over a first
vertebral body where said plate has been firmly attached to the
first vertebral body with a pair of bone screws; engaging said
second arm over a second vertebral body; and securing said plate to
said second vertebral body with at least one bone screw following
said step of shortening the distance between said first and second
arms of said compression tool.
453. Apparatus for compressing a spinal disc space disposed between
two adjacent vertebrae of a cervical spine, comprising: a body; a
first arm having a first end and a second end, said first arm
fixedly attached at its first end to said body; a second arm having
a first end and a second end, said second arm movably attached at
its first end to said body; means for imparting relative movement
to said first and said second arms toward one another to create a
compression force between said first and second arms; and means for
preventing movement of said second arm away from said first arm,
said preventing means associated with said body and said second
arm.
454. The apparatus of claim 453 in which the second end of at least
one of said first and second arms has an opening for removably
receiving an engagement device.
455. The apparatus of claim 454 in which said engaging device
comprises a sharp peg.
456. The apparatus of claim 454 in which said engaging device
comprises a hook.
457. The apparatus of claim 454 in which said engaging device is
movable in a rotational manner and extendible along the axis of
said arms.
458. The apparatus of claim 453 in which said preventing means
comprises of a ratcheted member, and said imparting means for
moving said arm comprises a gear associated with said second arm
connected to a handle whereby rotation of said handle in a first
direction moves said first arm toward said second arm.
459. The apparatus of claim 454 including a self-locking and
release assembly, said self-locking and release assembly engaging
said ratcheted member to prevent movement of said first and said
second arms away from one another while in a first position and
whereby said self-locking assembly may be disengaged from said
ratchetings to a second position by operation of said release
mechanism connected to said self-locking assembly.
460. A pilot hole forming apparatus for creating a pilot hole in a
cervical vertebral body comprising: a hollow tubular member having
a top end and a lower end configured to cooperatively engage a bone
screw receiving hole in a cervical plate, a rod having a
sharpened-end movable within said tubular member between an upper
position whereby said sharpened-end does not project beyond the
lower end of said tubular member and a lower position wherein said
sharpened-end projects below said lower end of said tubular member,
said rod having an upper portion that extends above the upper end
of said tubular member, whereby applying a force coaxial to said
rod force to said upper portion of said rod drives the
sharpened-end of said rod out of said tubular member, said
sharpened-end having sufficient length to pass through the cervical
plate and into the vertebral body to a predetermined depth less
than the depth of the vertebral body.
461. The apparatus of claim 460 further comprising means for
engaging the plate.
462. The apparatus of claim 460 in which said lower end of said
hollow tubular member has a reduced diameter portion.
463. The apparatus of claim 462 in which said reduced diameter
portion is threaded.
464. The apparatus of claim 460 in which top end of said upper end
of said rod has an increased diameter portion capable of being hit
by a hammer for driving the sharpened-end of the rod into the
vertebral body.
465. The apparatus of claim 460 including means for restricting the
distance that said rod can extend out of said lower end of said
tubular member.
466. The apparatus of claim 465 for use in the human adult cervical
spine in which the distance that the rod can extend out of said
lower end of said hollow tubular member is less than the depth of
the vertebrae with which it is to be used.
467. The apparatus of claim 466 in which said hollow tubular member
is configured to cooperatively engage a bone screw receiving hole
of a spinal plate so as to form a pilot hole coaxial to the central
longitudinal axis of the bone screw receiving hole.
468. The apparatus of claim 460 in which the sharpened-end of said
rod has surface edges to facilitate moving bone when said rod is
rotated.
469. The apparatus of claim 460 in which said sharpened-end extends
from said tubular member a length of 8-20 mm.
470. The apparatus of claim 460 in which said sharpened-end has a
major diameter of 2 mm.
471. A bone screw for use in attaching medical devices to the
anterior aspect cervical spine vertebrae, said screw comprising a
head, a shaft attached to said head and terminating at a tip, said
shaft having a thread, said shaft having a varying root diameter
from proximately below said head to proximately above said tip, the
outer diameter of said thread being substantially uniformly equal
from proximately below said head to proximately above said tip,
said thread having a thin profile and a sharp crest, said head
having a transverse cross sectional dimension greater than the
transverse cross sectional dimension of said shaft, and further
comprising a recess for coupling to a driver instrument.
472. The bone screw of claim 471 in which said tip is sharp.
473. The bone screw of claim 471 in which said root of said shaft
has an arcuate shape.
474. The bone screw of claim 471 in which said thread is of a
lesser diameter at said tip than above said tip.
475. The bone screw of claim 473 in which said arcuate portion of
said shaft has an increasing radius of curvature from said tip
towards said head.
476. The bone screw of claim 471 in which said bone screw has a
head, and said head has a convex top surface.
477. The bone screw of claim 471 in which said head has a flat
portion.
478. The bone screw of claim 471 in which said head has a first
upper diameter section and a smaller lower diameter section.
479. The bone screw of claim 471 in which said head has engagement
means for engagement with a screw driving tool.
480. The bone screw of claim 479 in which said engagement means is
an irregular recess.
481. The bone screw of claim 471 in which said bone screw is at
least in part made of a resorbable material.
482. The bone screw of claim 471 having a length of approximately
10-22 mm.
483. The bone screw of claim 482 having a thread pitch of 1.5-2.0
mm.
484. The bone screw of claim 471 in which the outer diameter of the
threads in 4-5 mm.
485. A bone screw for use in human spinal surgery, said screw
having a head portion, a threaded shank portion, and a tip, said
threaded shank portion having a length from about 10 mm to about 22
mm and a head length from about 1 mm to about 3 mm, said threaded
shank portion having a maximum outside diameter from about 3.6 mm
to about 5.2 mm and said head having a diameter from about 3.8 mm
to about 7.0 mm, said screw having a thread pitch from about 1.25
mm to about 2.5 mm and a sharp and thin threaded profile wherein
the apex of the two faces of the thread have an angle of less than
21 degrees and the base of said thread is less than 0.5 mm thick
and said screw has a root diameter that increases from proximately
above said tip along the longitudinal axis to proximately below the
head portion of said screw and said thread outer diameter being
generally constant from below said head portion to said tip
portion.
486. The bone screw of claim 485 in which said fluting interrupts
at least the most distant two thread turns at said tip.
487. The bone screw of claim 485 in which said screw has a tapered
tip and at least the first thread of said tip has a diameter less
than the diameter of the other screw threads.
488. The bone screw of claim 485 in which said bone screw is made
of a resorbable material.
489. The bone screw of claim 485 being made of a metal suitable for
human implantation.
490. The bone screw of claim 485 in which said tip being fluted by
at least one cut out section so as to make said screw
self-tapping.
491. A bone screw locking element for use in association with an
anterior cervical plating system, said locking element comprising a
member having a head, said head having a width and at least two
segments removed from said head for the width of said head.
492. The bone screw locking element of claim 491 in which said
member is a screw having a threaded shaft.
493. The bone screw locking element of claim 492 in which said
member has a camming surface on the bottom of said head.
494. The bone screw locking element of claim 492 in which said
member has a ramped surface on the bottom of said head.
495. The bone screw locking element of claim 491 in which said
member comprises a rivet having a top segment and a bottom segment
connected by a reduced diameter segment.
496. The bone screw locking element of claim 495 in which said
rivet has a camming surface on the bottom surface of said top
segment.
497. The bone screw locking element of claim 495 in which said
rivet has a camming surface on the top surface of said bottom
segment.
498. The bone screw locking element of claim 495 in which said
rivet has a ramped surface on the bottom surface of said top
segment.
499. The bone screw locking element of claim 495 in which said
rivet has a ramped surface on the top surface of said bottom
segment.
500. The bone screw locking element of claim 491 in which said
member comprises a threaded member.
501. The bone screw locking element of claim 491 in which said head
has a camming surface.
502. The bone screw locking element of claim 491 in which said head
has a ramped surface.
503. The bone screw locking element of claim 491 in which said
member has at least one projection extending from said head.
504. The bone screw locking element of claim 491 in which said head
has at least three removed segments.
505. The bone screw locking element of claim 491 in which said head
has at least four removed segments.
506. The bone screw locking element of claim 491 in which at least
a portion of said head is flexible.
507. The bone screw locking element of claim 491 in which said
heads has at least one slot for providing flexibility to at least a
portion of said head.
508. The bone screw locking element of claim 491 in which said
removed segments are arcuate.
509. A bone screw locking element for use in association with an
anterior cervical plating system comprising a member having a head,
said head having a width and at least a portion of said head being
flexible.
510. The bone screw locking element of claim 509 in which said head
has at least one slot for providing flexibility to at least a
portion of said head.
511. The bone screw locking element of claim 509 in which said
member is a screw having a threaded shaft.
512. The bone screw locking element of claim 511 in which said
member has a camming surface on the bottom of said head.
513. The bone screw locking element of claim 511 in which said
member has a ramped surface on the bottom of said head.
514. The bone screw locking element of claim 509 in which member
comprises a rivet having a top segment and a bottom segment
connected by a reduced diameter segment.
515. The bone screw locking element of claim 514 in which said
rivet has a camming surface on the bottom surface of said top
segment.
516. The bone screw locking element of claim 514 in which said
rivet has a camming surface on the top surface of said bottom
segment.
517. The bone screw locking element of claim 514 in which said
rivet has a ramped surface on the bottom surface of said top
segment.
518. The bone screw locking element of claim 514 in which said
rivet has a ramped surface on the top surface of said bottom
segment.
519. The bone screw locking element of claim 509 in which said
member comprises a set screw.
520. The bone screw locking element of claim 514 in which said set
screw has a camming surface.
521. The bone screw locking element of claim 509 in which said set
screw has a ramped surface.
522. The bone screw locking element of claim 518 in which said
member has at least one projection extending from said head.
523. The bone screw locking element of claim 509 in which said head
has at least one removed segment.
524. The bone screw locking element of claim 509 in which said head
has at least two removed segments.
525. The bone screw locking element of claim 509 in which said head
has at least three removed segments.
526. The bone screw locking element of claim 509 in which said head
has at least tour removed segments.
527. A locking element for use in association with an anterior
plating system comprising a member having a head, said head having
a width and at least a portion of the bottom surface of said head
being non uniform.
528. The locking element of claim 527 in which the bottom surface
of said member has a camming surface.
529. The locking element of claim 527 in which the bottom surface
of said member has a ramped surface.
530. The locking element of claim 529 in which the member is a set
screw.
531. The locking element of claim 529 in which the member is a
rivet.
532. The locking element of claim 529 in which the member has
projections.
533. The locking element of claim 529 in which the member is a
screw.
534. The locking element of claim 529 in which the member is a set
screw.
535. The locking element of claim 529 in which the member is a
rivet.
536. The locking element of claim 529 in which the member has
projections.
537. The locking element of claim 529 in which the member is a
screw.
Description
RELATED APPLICATIONS
[0001] This application claims priority of Application Serial No.
60/037,139 filed Feb. 11, 1997, incorporated herein by reference.
Application Ser. No. 08/______, (Attorney Docket No. P-13408) filed
Feb. 11, 1998, and titled SKELETAL PLATING SYSTEM is incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to implants, method,
and instrumentation for fusion of the human cervical spine from the
anterior aspect, and in particular to plate systems for aligning
and maintaining adjacent cervical vertebrae in a selected spatial
relationship during spinal fusion of those vertebrae.
[0004] 2. Description of the Related Art
[0005] It is current practice in the art to use cervical plating
systems for this purpose. Such systems are composed essentially of
plates and screws for aligning and holding vertebrae in a desired
position relative to one another. The earliest such devices
consisted of stainless steel plates and screws and required that
the screws passed entirely through the vertebrae and into the
spinal canal in order to engage the strong bone tissue (the
posterior cortex) of the vertebral bodies. This required the
ability to observe or visualize this area radiographically, which
is not always possible, especially in the lower cervical spine
where the vertebrae may be hidden radiographically by the
shoulders.
[0006] In order to form holes in the vertebral bodies for insertion
of each screw, a drilling operation was performed, followed by a
tapping operation. Each of these operations involved the passage of
an instrument entirely through the associated vertebral body and
into the spinal column. Thus, these instruments come into close
proximity to the spinal cord and the dural sac which are in close
proximity to the back surfaces of the vertebral bodies. Any
procedure which introduces an object into the spinal canal presents
serious risks which are of concern to the surgeon.
[0007] The conventional technique of forming a bone screw receiving
hole in vertebral bodies by drilling has a number of significant
disadvantages. For example, drilling removes bone material, leaving
a void and resulting in a loss of bone material. Drilling also
causes microfracturing of the bone at the drill bit-bone interface
and the resulting fracture lines tend to propagate in directions
perpendicular to the wall of the hole. More specifically, the bone
material is essentially a type of ceramic which exhibits a brittle
pattern of fracture formation and propagation in response to
drilling. Furthermore, drilling generates heat which can result in
thermal necrosis of the bone material precisely at the interface
between the bone and a subsequently installed screw, where necrosis
is most harmful. Any bone which does experience necrosis will
subsequently be resorbed by the body as part of the bone repair
process and this can lead to the loosening of the screw.
[0008] Another problem with drilling is that the path of the drill
bit is difficult to control and since the drill bit operates by
rotation, it can wind up soft tissue about the associated plate. In
addition, unless great care is taken, the drill bit may be driven
significantly past the posterior cortex and cause irreparable harm
within the spinal canal. Finally, a drill bit may bind and fracture
within the vertebral body and can then cause serious injury as the
still rotating portion of the drill bit passes into the wound,
while the portion of the bit which has broken off may either
protrude dangerously from the vertebral body or may be broken off
flush with the upper surface of the body so as to be irretrievably
embedded therein. In any event, the steps that must be taken to
retrieve the broken-off portion of a drill bit will inevitably
prolong and complicate the surgical procedure.
[0009] In known plating systems, there have been problems with
loosening and failure of the hardware, breakage of the screws and
plates, and backing out of screws into the patient's throat area.
These occurrences generally require further surgical procedures to
replace the broken parts or the plates and screws entirely, and to
repair any damage that may have been caused.
[0010] Other problems which have been encountered with known
systems result from the failure of the screws to achieve a
sufficient purchase in the bone and the stripping of the
screws.
[0011] Also, the use of the known plating systems may result in a
loss of lordosis, which is the normal curve of the cervical spine
when viewed from the side.
[0012] Known plating systems additionally experience problems in
connection with those procedures where bone grafts are placed
between vertebral bodies to achieve an interbody fusion which heals
by a process called "creeping substitution". In this process, bone
at the interface between the graft and a vertebra is removed by a
biological process which involves the production of powerful acids
and enzymes, as a prelude to invasion of the interface by living
tissue and the deposition, or growth, of new bone. While the plates
allow for proper alignment of the vertebrae and their rigid
fixation, they can therefore, at the same time unfortunately, hold
the vertebrae apart while the resorption phase of the creeping
substitution process forms gaps in the bone at the fusion site with
the result that the desired fusion does not occur. Such failure is
known as pseudoarthrosis. When such a failure occurs, the hardware
itself will usually break or become loosened from the spine, thus
requiring a further surgical procedure to remove the broken
components and another surgical procedure to again attempt
fusion.
[0013] In response to the problems described above, a second
generation of plating systems has been developed and/or proposed.
These include a system disclosed in U.S. Pat. No. 5,364,399 to
Lowery and U.S. Pat. No. 5,423,826 to Morscher, as well as cervical
spine locking plating systems offered by SYNTHES Spine, the DANEK
ORION plate, the CODMAN SHURTLEFF plate, and the SMITH NEPHEW
RICHARDS plate, among others. The systems' forming members of this
second generation have a number of common properties. They are all
made of either a titanium alloy or pure titanium rather than
stainless steel, to minimize adverse tissue reactions and are MRI
compatible, which stainless steel is not. The screws and the plates
have been given increased thickness in order to achieve increased
strength. The screws have larger diameters to improve their
purchase without requiring that they engage the posterior cortex of
the vertebral bodies. Some mild longitudinal contouring of the
plates is employed to allow for some lordosis, and/or limited
transverse contouring to better follow the generally curved aspect
of the front of the vertebral bodies. Mechanisms are employed for
securing the vertebral bone screws to their associated plates in a
manner to prevent the screws from backing out. While this second
generation of plating systems represents a significant improvement
over earlier systems, certain existing problems persist, while new
problems have been created.
[0014] For example, since the screws no longer extend into the
posterior cortex, it is common for the threads in the tapped screw
hole to become stripped and for the screws to fail to gain a
suitable purchase. In addition, screw breakage continues to be
experienced and occurs most commonly at the junction of the screw
to the posterior aspect of the plate. The screws employed in both
the SYNTHES system and the SMITH NEPHEW RICHARDS system are
particularly vulnerable to this problem because those screws are
hollow at the level where they attach to the plate to permit the
internal reception of locking screws.
[0015] In an attempt to prevent screw to plate junction breakage of
the screw, more recent designs of screws have an increasing root
diameter from tip to head, which thus far has resulted in a near
useless stubby and blunt thread near the screw head with little
holding power and little tactile feedback to the surgeon to signal
the completion of tightening prior to stripping of the screw within
the bone. Based on empiric studies testing these prior art screws,
the use of a pretapped hole, rather than a self-tapping screw, was
found to be preferred for pullout strength and thus these screws
have not been self-tapping and thus the screw holes must be
pre-tapped. Since the thread cutting portion of a tap is
necessarily sharp and rotated to work, there is a serious risk of
damage to the surrounding soft tissues when it is used. This is
compounded by the fact that the plates employed in these systems do
not provide sufficient long axis contouring to make full allowance
for lordosis and do not have sufficient transverse contouring to
prevent rocking of the plate about its longitudinal axis and to
conform to the anterior shape of the vertebral bodies, so that
these plates do not prevent soft tissue from creeping in from the
sides and beneath the screw holes thus exposing these tissues to
damage by the drill and the tap. While it is possible, at the time
of surgery, to make some change in the contouring of these plates,
this is generally limited to contouring of the longitudinal axis
and quite often causes distortion of the plate's bone screw holes
and screw hole to plate junctions in a manner which has an adverse
effect on the screw-plate interlock. Lack of proper contouring
prevents these plates from having an optimally low profile relative
to the spine.
[0016] In some of the second generation cervical plating systems,
screw backout continues to occur, because these plates could not be
designed to allow for the locking of all of the screws.
Specifically, while the designers of these plates recognized the
importance of securing the bone screws to the plates, they were
unable to lock all of the screws and had to settle for leaving some
of the screws unlocked.
[0017] Furthermore, several of these second generation systems
utilize tiny and delicate "watchmaker" parts to achieve
interlocking. These parts are characterized by the need to engage
them with particularly delicate small ended screw drivers. These
interlocking components are easily rendered ineffective by any
effort to alter the contours of a plate during surgery.
[0018] Despite the improvement of these second generation plating
systems over the first problems, the problems still persist, the
most important of which is pseudoarthroses, and particularly
"distraction pseudoarthroses". Although these second generation
plates have clearly led to an increase in fusion rate, when a
failure to produce fusion occurs, it is generally accompanied by
bone resorption along a line at the graft-to-vertebra junction,
which can be seen on a radiograph.
[0019] In the case of the weak first generation plates and screws,
the plates might hold the vertebrae apart, preventing fusion, but
only until the hardware would break, relieving the distraction, and
then allowing the fusion to occur. The second generation systems of
plates are too strong to allow this to occur, thus requiring
further surgical procedures for the correction of the
pseudoarthroses.
[0020] Compression plates are well-known and are widely used in
orthopedic surgery for the stabilization of tubular bones, and
sometimes also flat bones. Such plates may rely on some external
compression means or may be self-compressing, relying on the
ability of the screw head to slide within a ramped slot such that
the tightening of the bone screws through the plate imparts a
linear motion perpendicular to the screw axes. U.S. Pat. No.
5,180,381 discloses an attempt to employ such a mechanism in
connection with anterior spinal fixation.
[0021] However, it has been found that all of the proposed
self-compressing plating systems have in common the need for a
screw to engage both a proximal and a distal cortex, (bone casing
of very dense bone material), so as to anchor the screw tip in a
manner to allow the plate to move relative to the screw when
tightened rather than allowing the plate to drag the screw off
axis. However, as already discussed earlier herein, when a screw is
to engage the posterior cortex of the vertebral body, it is
necessary for the drill and the tap which form the screw hole, as
well as the screw tip itself, to all enter the spinal canal,
thereby exposing the spinal cord to damage.
[0022] While the system disclosed in U.S. Pat. No. 5,180,381 avoids
such danger by engaging the vertebral body end plate instead of the
posterior vertebral body cortex, the path of the screw is of
necessity quite short, so that there is very little opportunity for
the screw threads to achieve additional purchase within the
vertebral body. It would therefore appear that to the extent that
the device disclosed in U.S. Pat. No. 5,180,380 is able to achieve
its stated objectives, it would pull the front of the spine
together more than the back and would not appear to compress the
back of the vertebral bodies at all, thus producing an undesirable
iatrogenic loss of the normal cervical lordosis. Such a situation
is disruptive to the normal biomechanics of the cervical spine and
potentially quite harmful.
[0023] The creation of compression between adjacent vertebrae would
offer a number of advantages, including reduced distraction
pseudoarthrosis, increased surface area of contact between the
graft and vertebrae as slightly incongruent surfaces are forced
together, increased osteogenic stimulation, since compressive loads
stimulate bone formation, and increased fusion graft and spinal
segment stability.
[0024] Among the new problems created by these second generation
systems is a tendency for the small "watchmaker" parts used to lock
the bone screws to the plate to fall off of the driver used for
attaching those parts, or out of the associated plates and to
become lost in the wound. In addition, these small parts are quite
fragile and require specialized additional instruments for their
insertion and/or manipulation. Furthermore, incorrect bone screw
placement relative to the axis of a plate hole may render the screw
locking mechanism unworkable or may cause sharp and jagged shavings
of titanium to be formed as a locking screw is driven into contact
with an improperly seated bone screw. The means for establishing
bone screw to plate hole alignment and preparation are less than
reliable. Furthermore, most of these second generation systems lack
a reliable and effective means for positioning and holding the
plate during attachment.
[0025] Specific features of various prior art systems will be
summarized below.
[0026] The system disclosed in U.S. Pat. Nos. 5,364,399 and
5,423,826, cited earlier herein, includes a thin stainless steel
plate which allows for side-by-side or offset bicortical screw
placement, the plate having a combination of screw holes and
slots.
[0027] The "Acromed" system includes a titanium plate and screws
which require bicortical screw placement. This system does not
include any locking means for the bone screws.
[0028] The system disclosed in U.S. Pat. No. 5,180,381 includes an
"H" shaped plate having a combination of ramped slots and a hole
which requires bicortical screw placement at a 45.degree. angle to
the plane of the plate. This patent discloses that this angular
positioning is for the purpose of producing compression.
[0029] The SYNTHES Morscher plate system employs hollow, slotted
screw heads. The screws are placed unicortically so that the heads,
when properly aligned, come to rest in the upper portion of the
plate holes. The upper portion of each screw is internally threaded
to receive a tiny screw which is screwed into the bone screw head
in order to increase the interference fit between the bone screw
head and the wall of the associated plate hole.
[0030] In the system disclosed in U.S. Pat. Nos. 5,364,399 and
5,423,826, use is made of pairs of unicortical bone screws that may
be locked in place at both ends of the associated plate by locking
screws which have a small diameter shank and a large head. At each
end of a plate two bone screws may be locked in place by a single
locking screw which is situated between the bone screws. Generally,
the plate is provided, between its two ends, with a diagonal slot
or slots for receiving one or more additional screws, each
additional screw being securable in a bone graft or a respective
vertebra which is spanned by the plate. There is no locking screw
associated with these intermediate bone screws to lock the bone
screws to the plate.
[0031] The Codman Shurtleff plating system utilizes the side of a
preinstalled rivet having a head rotatable to press against the
side of the head of a bone screw so as to secure that one screw to
the plate. The plates of this system also are provided with holes
for receiving intermediate screws, but these screws are not
associated with any locking means.
[0032] While the designers of the last-mentioned systems recognized
the importance of locking the bone screws in position on their
associated plates, they did not provide for any locking of the
intermediate bone screws in their associated holes.
[0033] In an earlier version of the Codman Shurtleff system, the
locking mechanism was a lever pivotable about a shaft passing
entirely through the plate and then flared so as to retain the
shaft within the plate. The lever was rotated after the bone screw
had been inserted to engage the head of the bone screw and thus
secure the bone screw to the plate.
[0034] Based on a consideration of the features of all of the known
cervical plating systems, it appears that there remains a need for
an improved system having the following combination of
features:
[0035] 1) The plate should be sufficiently strong to perform its
intended function without mechanical failure;
[0036] 2) The plate should be preformed in three dimensions so as
to anatomically conform in both the longitudinal and transverse
planes to the anterior cervical spine;
[0037] 3) The plate should be constructed so that all of the bone
screws are generally perpendicular to the plate when viewed from
the side, but pairs of screws are highly convergent corresponding
to any vertebral level when viewed from the bottom, or on end;
[0038] 4) Each pair of screws engages in a respective vertebra and
the high convergence of screws in a pair allows the length of the
screws which engage the bone to be longer and still remain within
that vertebra and provide a safer and stronger engagement with the
vertebrae;
[0039] 5) The system should include bone screws which are capable
of achieving enhanced purchase within the bone of the vertebral
body and without the need to penetrate the posterior vertebral
cortex and enter the spinal canal;
[0040] 6) Use should be made of a screw which is self-tapping,
thereby eliminating the need for separate tapping steps;
[0041] 7) A reliable means should be provided for engaging and
manipulating the plate during installation;
[0042] 8) The plate should be engageable with an instrument means
which can reliably produce bone screw holes which are coaxial with
the screw holes in the plate;
[0043] 9) It should be possible to prepare the vertebral bone to
receive the bone screws so as to produce a stronger connection and
a reduced danger of thread stripping by means of a pilot hole punch
creating a pilot hole for the bone screws;
[0044] 10) Alternatively to the use of a pilot hole punch, a
relatively (compared to the overall root diameter of the screw)
small diameter drill may be used to create the pilot hole.
[0045] 11) Means should be provided for locking each and every bone
screw in position relative to the plate, and the locking means
should be of sufficient size and strength to reliably perform its
intended functions;
[0046] 12) Bone screw locking means should preferably be retainable
by the plate prior to bone screw insertion, or should be reliably
attachable to a driver to prevent any small parts from becoming
loose in the wound; and
[0047] 13) The system should be capable of effecting compression of
the vertebral segments to be fused while maintaining and/or
restoring lordosis.
OBJECTS OF THE INVENTION
[0048] It is an object of the present invention to provide an
improved anterior cervical plating system, installation
instrumentation, and installation method which has the above
described features and which avoids many of the shortcomings of
previously known systems.
[0049] One object of the present invention is to provide a locking
mechanism where a plurality of bone screws used for attaching the
plate to the vertebrae can be easily and reliably locked in place
at the same time by a single operation.
[0050] Another object of the present invention is to provide a
vertebral plate in which the locking mechanisms for locking the
bone screws may be pre-installed by the manufacturer prior to the
insertion of the bone screws by the physician so that the physician
does not have to attach the locking mechanism to the plate as a
separate procedure during the operation.
[0051] Another object of the invention is to provide an anterior
cervical plating system which allows for the intersegmental
compression of the spinal segment (compression of the adjacent
vertebrae and the fusion graft in the disc space between the
adjacent vertebrae) in lordosis, and similarly, where desired,
multisegmental compression.
[0052] A further object of the invention is to provide bone screws
which provide for tactile feedback to the surgeon to assure
sufficient tightening of the screws while avoiding stripping and
are less prone to failure by breakage or by loosening.
[0053] Another object of the invention is to provide bone screws
which achieve optimal purchase within the bone, without the need to
penetrate the posterior cortex of the vertebrae.
[0054] A further object of the invention is to provide plates which
are textured or otherwise treated to promote bone growth from
vertebrae to vertebra beneath the plate.
[0055] Another object of the invention is to provide a plate which
is constructed to reliably engage an instrument for forming all
bone screw holes coaxial with the holes formed in the plate, the
instrument having integral depth limiting means which completely
eliminates the danger of perforation of the posterior vertebral
wall or entry into the spinal canal.
[0056] Yet another object of the invention is to provide a system
in which the bone screws and locking mechanisms, when fully
installed, have a low profile.
[0057] It is another object of the present invention to provide for
an anterior cervical plating system which is at least in part
bioresorbable.
[0058] It is another object of the present invention to provide for
an anterior cervical plating system comprising at least in part of
bone ingrowth materials and surfaces.
[0059] It is another object of the present invention to provide for
an anterior cervical plating system comprising at least in part of
bone growth promoting substances.
[0060] It is another object of the present invention to provide
instruments for reliably and easily performing the installation of
the plates of the present invention.
[0061] It is still another object of the present invention to
provide an improved method of installing the plates of the present
invention.
[0062] The above and other objects and features of the invention
will become more readily apparent from the following description of
preferred embodiments of the invention, provided with reference to
the accompanying drawings, which illustrate embodiments of the
invention solely by way of non-limiting example.
SUMMARY OF THE INVENTION
[0063] The plating system of the first preferred embodiment of the
present invention comprises a plate having a length sufficient to
span a disc space and to overlap, at least in part, at least two
adjacent cervical vertebrae, a substantial portion of the lower
surface of the plate preferably being bi-concave, that is concave
curved along a substantial portion of the longitudinal axis of the
plate and concave curved along a substantial portion of the
transverse axis of the plate. The lower surface of the plate may
also textured and/or treated to induce bone growth along the lower
surface of the plate which contacts the cervical vertebrae. The
plate is provided with a plurality of bone screw receiving holes
which extend through the plate, from the upper surface to the lower
surface of the plate, and at least one locking element is
associated with the bone screw receiving hole. The plate and its
component parts, may be made of any implant quality material
suitable for use in the human body, and the plate and associated
component may be made of a bioresorbable material.
[0064] Bone screws are each insertable into a respective bone screw
receiving hole for attaching the plate to a vertebra. A locking
element, is engageable to a locking element receiving recess and
has a head formed to lock the bone screws to the plate. In the
preferred embodiment, a single locking element locks a number of
different bone screws in place. The locking elements are
pre-installed prior to use by the surgeon in a manner so as to not
impede installation of the bone screws.
[0065] As a result, the problems previously associated with the
locking screws of the type applied after the insertion of the bone
screws, including the problems of instrumentation to position and
deliver to the plate the locking means, backing out, breakage,
stripping and misthreading associated with the prior art more
delicate locking screws resembling "watchmaker's parts", are
eliminated.
[0066] In an alternative embodiment of the present invention, a
locking element fits within a respective bone screw receiving hole
to lock a respective one of the bone screws in place. According to
this second embodiment of the invention, each of the bone screws is
locked to the plate by means of an individual locking element which
bears against at least a portion of the bone screw. Since no other
holes need be formed in the plate to attach the locks to the plate,
the plate remains quite strong.
[0067] The locking elements can be in many forms to achieve their
intended purpose, such as, but not limited to, screws, threaded
caps, rivets, set screws, projecting elements, and the like.
[0068] Also, a novel bone screw is disclosed so as to prevent
pulling out of the bone screw during use. This is achieved by a
design which includes a screw in which the outer diameter or crest
diameter of the thread is maintained substantially constant along
the entire length of the shaft of the bone screw, from below the
head to above the tip, where threads of a lesser outer diameter
facilitate insertion. The screw tip is fluted at its distal end to
be self-tapping. The thread also has an extremely thin and sharp
profile to cut into and preserve the integrity of the vertebral
bone stock.
[0069] The plating system does not require that the head of the
bone screw be hollow, or that additional holes be placed through
the plate in addition to those provided for the passage of the bone
screws. It will be appreciated that bone screws are weakened when
their heads are hollow and that plates are weakened when they are
provided with additional holes.
[0070] Additionally, the plate of the disclosed systems permit the
proper aligning of the holes in the plate for the bone screws and
for the plate to be easily applied to the vertebrae in compression.
The plates include appropriate slots and engagement means for
engaging compression instrumentation, described in detail below,
for applying a compression force between adjacent vertebrae to
which the plate is attached, in a reliable and easy manner.
[0071] An improved locking screw driver is provided. The driver
provides for a wedged interference fit with a recess in the head of
the bone screws and the head of the locking elements. The same
driver is usable for both bone screws and locking elements. The
driver ensures that the locking element cannot fall off the driver
and become lost in the wound. The driver has a tapered end to
facilitate insertion into the complimentary recess in the head of
the screws and is used to engage and pick up the locking elements.
Alternatively, the receiving socket can be tapered to the same
purpose.
[0072] Alternatively, a combination bone screw and locking screw
driver is disclosed in which the bone screw driver passes through a
longitudinal opening in the locking screw driver so that both the
bone screw and the locking screw can be loaded prior to insertion
of the bone screw and both can be tightened with one instrument,
without removing it from position.
[0073] Also, instruments are provided for forming pilot holes to
assist in the ease and accuracy of the installment of the bone
screws, and for creating a creating a compression force between
adjacent vertebrae during installation of the plate and for holding
the plate during installation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0074] FIG. 1 is a top perspective view of a first embodiment of a
cervical spine multiple locking plate.
[0075] FIG. 2 is a top plan view of the cervical spine multiple
locking plate shown in FIG. 1.
[0076] FIG. 3 is a side elevational view of the cervical spine
multiple locking plate shown in FIG. 1.
[0077] FIG. 4 is an end view of the cervical spine multiple locking
plate shown in FIG. 1.
[0078] FIG. 5 is a bottom plan view of the cervical spine multiple
locking plate shown in FIG. 1.
[0079] FIG. 6 is a top plan view of the cervical spine multiple
locking plate shown in FIGS. 1-5, with locking elements installed
in an open configuration.
[0080] FIG. 7 is a top plan view of a modification of the plate of
FIGS. 1-6 with a four bone screw locking element in place.
[0081] FIG. 8 is a top plan view of a further embodiment of a
cervical locking plate of FIG. 1 with an elongated central slot for
increased compression capability.
[0082] FIG. 9 is a top plan view of a locking element for use with
the plates of FIGS. 1-6.
[0083] FIG. 10 is a top plan view of a locking element for use with
the central opening of the plate of FIGS. 7 and 22.
[0084] FIG. 11 is a top plan view of a locking cap for use in the
end openings shown in FIGS. 1, 6, and 7.
[0085] FIG. 12 is a side elevational view of the locking element of
FIG. 16.
[0086] FIG. 13 is a side elevational view of another embodiment of
the locking element of FIG. 16.
[0087] FIG. 14 is a top perspective view of an alternative
embodiment of cervical spine multiple locking plate for use with
locking rivets.
[0088] FIG. 15 is a bottom plan view of the cervical spine multiple
locking plate of FIG. 14.
[0089] FIG. 16 is a top plan view of a two bone screw locking
element.
[0090] FIG. 17 is a top plan view of an alternative embodiment of a
four bone screw locking element having head slits for increased
flexibility of the locking tabs.
[0091] FIG. 18 is a bottom plan view of a rivet type locking
element for use with the central opening of the plate of FIG.
14.
[0092] FIG. 19 is a side elevational view of a rivet locking
element.
[0093] FIG. 20 is a top perspective view of the bottom portion of
the head of rivet of FIG. 19 viewed along lines 20-20.
[0094] FIG. 21 is a top perspective view of the head portion of a
three bone screw locking element.
[0095] FIG. 22 is a top perspective view of a third embodiment of a
cervical spine multiple locking plate utilizing locking elements in
the form of threaded caps.
[0096] FIG. 23 is a side elevational view of a locking element for
use with the plate of FIG. 22.
[0097] FIG. 24A is a side elevational view of a bone screw in
accordance with the present invention.
[0098] FIG. 24B is an enlarged side elevational view of the bone
screw of FIG. 24A.
[0099] FIG. 25 is a side elevational view of an alternative
embodiment of a bone screw in accordance with the present
invention.
[0100] FIG. 26 is a bottom end view of the bone screw shown in FIG.
24A.
[0101] FIG. 27 is a top end view of the bone screw shown in FIG.
24A.
[0102] FIG. 28 is a top perspective view of a fourth embodiment of
a cervical spine multiple locking plate.
[0103] FIG. 29 is a top perspective view of a locking element for
use with the plate of FIG. 28.
[0104] FIG. 30 is a partial side sectional view of the plate of
FIG. 28 along lines 30-30 with a bone screw in place.
[0105] FIG. 31 is a top perspective view of the plate of FIG. 1
positioned against the anterior aspect of three successive
vertebral bodies in the cervical spine, a plate holder, and an
instrument for forming bone screw receiving holes in to the
vertebral bodies.
[0106] FIG. 32 is a cross-sectional view of a portion of the bone
forming device shown in FIG. 31 viewed along lines 32-32.
[0107] FIG. 33 is a side elevational view in partial cross section
illustrating a compression post tool and a compression post engaged
to it for insertion into a vertebral body.
[0108] FIG. 34 is a side elevational view in partial cross section
of the compression post tool engaged for removal of the compression
post from the vertebral body.
[0109] FIG. 35 is a bottom end view of the compression post tool of
FIG. 34.
[0110] FIG. 36 is a side elevational view of a plate engaging hook
for use with the compression apparatus shown in FIG. 38.
[0111] FIG. 37 is a cross-sectional view through the plate of an
alternative embodiment of a hole forming instrument in the form of
a drill guide and drill for use during the plate installation
procedure.
[0112] FIG. 38 is a side elevational view showing intersegmental
compression of the spine and compression apparatus.
[0113] FIG. 39 is a view similar to that of FIG. 38 showing the
compression apparatus in a further stage of the plate installation
procedure.
[0114] FIG. 40 is a top perspective view showing the locking of the
bone screws to the plate.
[0115] FIG. 41 is a partial side sectional view of a locking
element attached to a driver instrument.
[0116] FIG. 42 is a partial side sectional view of another
embodiment of the locking element attached to a driver
instrument.
[0117] FIG. 43 is a partial cross-sectional view showing a cervical
plate, locking element, and bone screws along lines 43-43 of FIG.
40.
[0118] FIG. 44 is an enlarged portion of detail along line 44 of
FIG. 43.
[0119] FIG. 45 is a side view in partial cross section of a plate
holder attached to a plate.
[0120] FIG. 46 is a side view in partial cross section of another
embodiment of a plate holder attached to a plate.
[0121] FIG. 47 is a top perspective view of a first embodiment of a
single locking plate.
[0122] FIG. 48 is a top plan view of the plate shown in FIG.
47.
[0123] FIG. 49 is a side elevational view of the plate shown in
FIG. 47.
[0124] FIG. 50 is an end view of the plate shown in FIG. 47.
[0125] FIG. 51 is a bottom plan view of the plate shown in FIG.
47.
[0126] FIG. 52 is a top plan view of the plate shown in FIG. 47,
with locking elements in place.
[0127] FIG. 53 is a side elevational view of a bone screw used with
the plate shown in FIG. 47.
[0128] FIG. 54 is a top end view of the bone screw shown in FIG.
53.
[0129] FIG. 55 is a bottom end view of the bone screw of FIG.
53.
[0130] FIG. 56 is a top plan view of a locking cap for use with the
single locking plate of FIG. 47.
[0131] FIG. 57 is a side elevational view of the locking cap shown
in FIG. 56.
[0132] FIG. 58 is a bottom plan view of the locking cap shown in
FIGS. 56 and 57.
[0133] FIG. 59 is a bottom perspective view of the locking cap of
FIGS. 56-58.
[0134] FIG. 60 is a top perspective view of the single locking
plate of FIG. 47 shown being held by a plate holder against three
vertebral bodies, with the hole forming instrument for punching a
pilot hole into the vertebral bodies for receiving a bone
screw.
[0135] FIG. 61 is a side elevational view in partial cutaway of the
hole forming instrument threaded to a bone screw receiving
hole.
[0136] FIG. 62 is a perspective side sectional view of the drill
and drill guide threadably engaged to the plate for drilling a hole
for insertion of a bone screw.
[0137] FIG. 63 is a top perspective view of a single locking plate
installed along a segment of the spine with two locking caps
installed in two bone screw receiving holes.
[0138] FIG. 64 is a side elevational view in partial cross section
of a locking cap engaged to a driver for installing the locking
cap.
[0139] FIG. 65 is a partial cross sectional view of the plate, bone
screws and locking caps along line 65-65 of FIG. 63.
[0140] FIG. 66 is an enlarged fragmentary view of area 66 of FIG.
65.
[0141] FIG. 67 is a perspective view of a cervical locking plate
being held by an alternative plate holder instrument.
[0142] FIG. 68 is an end sectional view showing the plate holder of
FIG. 67 engaging a plate.
[0143] FIG. 69A is an end sectional view of an alternative
embodiment of the plate holder.
[0144] FIG. 69B is an end sectional view of another alternative
embodiment of the plate holder.
[0145] FIG. 70 is a plate holder instrument with an offset and
removable handle.
[0146] FIG. 71 is a top perspective view of a second embodiment of
a cervical single locking plate having individual locking elements
to lock each bone screw.
[0147] FIG. 72 is a top perspective view of a threaded locking
element for use with the cervical single locking plate of FIG.
71.
[0148] FIG. 73 is a partial side sectional view of the plate of
FIG. 71 viewed along lines 73-73 with the locking element of FIG.
72 in place to hold a bone screw, but not fully tightened.
[0149] FIG. 74 is a top perspective view of an alternative locking
element for use with a first modification of the cervical single
locking plate of FIG. 71.
[0150] FIG. 75 is a side sectional view of the first modification
of the plate of FIG. 71 with the locking element of FIG. 74.
[0151] FIG. 76 is a perspective view of an alternative locking
element for use with the first modification of the plate of FIG.
71.
[0152] FIG. 77 is a partial side sectional view of the first
modification of the plate of FIG. 71 with the locking element of
FIG. 76 in place.
[0153] FIG. 78 is a top perspective view of another alternative
locking element in the form of a rivet for use with a second
modification of the locking plate of FIG. 71.
[0154] FIG. 79 is a partial side sectional detail view of the plate
of FIG. 71 modified to use a locking element of FIG. 78 shown in
place.
[0155] FIG. 80 is a partial cross sectional view of a plate and
bone screw with the end of a tool shown for use in inserting both
the bone screws and locking caps.
[0156] FIG. 81 is a side elevational view of another embodiment of
the tool of FIG. 80.
[0157] FIG. 83 is a further embodiment of a cervical spine multiple
locking plate for use in stabilizing multiple segments of the
spine.
[0158] FIG. 84A-84E are various embodiments of cervical spine
multiple locking plates for use in stabilizing a single segment of
the spine.
DETAILED DESCRIPTION OF THE DRAWINGS
[0159] The present invention will be described first in association
with the preferred embodiment of the plate system in which a
plurality of bone screws are locked in place with one locking
element. This is referred to as the multiple locking plate system.
The multiple locking plates will be described, then the locking
elements for locking the bone screws to the plate, then the bone
screws associated with the multiple locking plates, and finally the
instrumentation and method of installation of the multiple locking
plates. Thereafter the plate systems in which a single locking
element locks a single bone screw will be described. This is
referred to as the single locking plate system. The locking
elements, bone screws, instrumentation, and method of installation
associated with the single locking plate will then be
discussed.
[0160] 1. Multiple Locking Plate System
[0161] The preferred embodiment of the multiple locking anterior
cervical locking plate 2 according to the present invention (here
shown by way of example for use in a two level fusion (three
adjacent vertebrae)) is shown in FIGS. 1-5. Plate 2 has a generally
elongated form whose outline generally departs from rectangular due
to the presence of lobes or lateral projections 4 at the corners
and at the center of the sides of plate 2. Each lobe 4 has a
rounded outline and contains a respective circular bone screw
receiving hole 6. Two additional intermediate circular bone screw
receiving holes 8 are located inwardly of the sides of plate 2 and
are centered on the longitudinal center line of plate 2. Lobes 4
give plate 2 additional strength in the region surrounding each
bone screw receiving hole 6. It is recognized that other shapes for
the plate 2 may be employed.
[0162] The intermediate paired bone screw receiving holes 8 are for
use with a two level (three vertebrae) fusion. The intermediate
bone screw receiving holes 8 may be eliminated for a single level
(two vertebrae) fusion, or additional intermediate bone screw
receiving holes 8 may be added if additional levels are to be
fused.
[0163] Plate 2 is further provided with three locking element holes
12, each of which in the preferred embodiment is internally
threaded 3, and each of which is surrounded by a shallow
countersunk region 14. As will be described in greater detail
below, in the preferred embodiment, bone screws are inserted in the
bone screw receiving holes and a single pre-installed locking
element associated with each of the locking element holes 12 locks
a number of bone screws 30 in position at one time.
[0164] The number of paired bone screw holes generally correspond
to the number of vertebrae to be fused. A plate for a one level
fusion could have but a single locking element hole 12, while
plates for fusing more than two levels (three vertebrae) could have
additional middle locking element holes 12 corresponding to
additional paired bone screw holes. In the embodiment illustrated
in FIGS. 1-6, each end locking element 20 will lock three bone
screws 30 in place, while the locking screw 21 in the central
locking hole 12 locks two bone screws 30 in place. As shown in FIG.
7, central locking element 25 can also be configured so that four
bone screws 30 are locked at one time.
[0165] As shown particularly in FIGS. 3, 4 and 5, plate 2 is shaped
so that its bottom surface 27 (the surface which will be in contact
with the vertebral bodies) has a biconcave curvature, being concave
both in the longitudinal plane (corresponding to its length) and in
the plane transverse thereto, corresponding to its width. The
concave curvature in the longitudinal plane conforms to the proper
shape of the anterior aspect of the spine with the vertebrae
aligned in appropriate lordosis. That longitudinal curve is an arc
along the circumference of a circle (referred to herein as the
"radius of curvature") 15.0 cm to 30.0 cm in radius and more
preferably 20.0-25.0 cm in radius. Viewed on end in FIG. 4, the
plate 2 has a radius of curvature of a circle 15-25 mm in radius,
but preferably 19-21 mm in radius. While the plate 2 may have a
thickness between 2 to 3 mm, a thickness of between 2.25 and 2.5 mm
is preferred.
[0166] Having the bottom surface 27 of plate 2 contoured so that it
is able to lie flush against the associated vertebral bodies is in
contrast to conventional plates which have larger radii of
curvature that contact the vertebral bodies only along the
longitudinal centerline of the plate, thereby permitting
side-to-side rocking of the plate relative to the vertebral bodies.
The contour of the plate of the present invention provides
effective resistance to rocking of the plate 2 relative to the
vertebral bodies about the longitudinal center line of the plate,
thereby reducing stress on the plate 2 and bone screws 30, and
preventing the soft tissues from becoming engaged beneath the
plate.
[0167] Other advantages produced by the above curvature are that
the plate 2 will conform more closely to the facing bone surface;
the plate 2 will project from the spine by a smaller distance; soft
tissue will be prevented from sliding underneath the edges of the
plate 2, where it could be subject to damage; and the angle of the
bone screws 30, perpendicular to the plate when viewed from the
side, when installed will be at a substantial converging angle,
trapping the vertebral bone between the bone screws 30, and thus
more strongly anchoring the plate to the spine.
[0168] As shown in FIG. 5, the bottom surface 27 of plate 2,
preferably has a porous, roughened, and/or textured surface layer
and may be coated with, impregnated with, or comprise of fusion
promoting substances (such as bone morphogenetic proteins) so as to
encourage the growth of bone along the underside of the plate 2
from vertebrae to vertebrae. The textured bottom surface 27 also
provides a medium for retaining fusion promoting substances with
which the bottom surface 27 layer can be impregnated prior to
installation. The bottom surface 27 of plate 2 may be given the
desired porous textured form by rough blasting or any other
conventional technology, such as etching, plasma spraying,
sintering, and casting for example. If porous, the bottom surface
27 is formed to have a porosity or pore size in the order of 50-500
microns, and preferably 100-300 microns. Fusion promoting
substances with which the porous, textured bottom surface 27 can be
impregnated include, but are not limited to, bone morphogenetic
proteins, hydroxyapatite, or hydroxyapatite tricalcium phosphate.
The plate 2 may comprise of at least in part a resorbable material
which can further be impregnated with the bone growth material so
that as the plate 2 is resorbed by the body of the patient, the
bone growth material is released, thus acting as a time release
mechanism. Having the plate 2 being made from a material that is
resorbable and having bone growth promoting material present
permits the vertebrae to be fused in a more natural manner as the
plate becomes progressively less load bearing thereby avoiding late
stress shielding of the spine.
[0169] As further shown in FIGS. 4 and 5, at least one end of plate
2 has a recess 18 that can cooperate with a compression apparatus,
described in detail later in reference to FIGS. 36 and 38.
[0170] FIG. 6 is a top plan view of the plate 2 of FIG. 1 with
locking elements 20, 21 inserted into the locking element receiving
holes. In the preferred embodiment, the locking elements 20, 21 are
in the form of screws that cooperate with the threaded interior 3
of the locking holes 12. Each of these locking elements 20, 21 is
shown in its initial open orientation, where the orientation of the
cutouts 22 in the head 23 of each locking element 20, 21 is
oriented so as to permit introduction of bone screws 30 into
adjacent bone screw receiving holes 6, 8 without interference by
the head 23 of the locking element 20, 21. It is appreciated that
other configurations of the head 23 are possible so as to permit
introduction of bone screw into adjacent bone screw receiving holes
without interference by the head 23.
[0171] FIG. 8 is a top view of another embodiment of plate 2 of
FIGS. 1-5, and is generally referred to as plate 120. Plate 120 is
provided with a longitudinally extending elongated slot 122 along
its longitudinal axis which is superimposed on the middle locking
hole 12. Elongated slot 122 allows additional relative movement
between plate 120 and a compression post 54 associated with a
compression tool during the compression procedure, as discussed
below.
[0172] Referring to FIGS. 14 and 15, an alternative embodiment of a
multiple locking plate referred to by the number 70 is shown. In
plate 70, rather than the threaded locking hole 12, a central
opening 200 for receiving a removable rivet 202, of the type shown
in FIGS. 17-20, is provided. FIG. 15 is a bottom plan view of the
plate 70 shown in FIG. 14. The contour of the plate 70 is the same
as that of the plate 2 shown in FIGS. 1-5. The rivet 202 is
removable and fits within the unthreaded opening 200, comparable to
the locking hole 12 and slot 122 described above. Other embodiments
may employ a rivet that is not removable, but is manufactured as
part of the plate 70 as would be used in the end locking holes 19
of FIGS. 14 and 15.
[0173] Referring to FIG. 22, another alternative embodiment of a
multiple locking plate is shown and is generally referred to by the
number 230. The plate 230 uses threaded caps, such as cap 300 shown
in FIGS. 9 and 23, for a locking element or preferably one with cut
outs as described having an appearance in a top view such as the
locking element in FIGS. 10-11, for example. The central locking
hole 602 has an elongated slot 234 for providing an increased
compression capability, as will be discussed further herein.
[0174] Referring to FIGS. 10-13, a first embodiment of a locking
element 20, 21, 25 in the form of locking screws according to the
present invention for use with plate 2 is shown. FIG. 10 is a top
plan view which illustrates the head 23 of the central locking
element 25 shown in FIG. 7. The shaft 46 of locking element 25 is
threaded 47 to mate with the threading 3 within the associated
locking hole 12 of plate 2. As shown in FIG. 21, each segment 49 on
each side of cutouts 22 of the locking element 21 has a bearing
surface 48 formed at the lower surface of locking element head 23.
As shown in FIG. 16, the locking element head 23 can be provided
with two slots 42 for providing flexibility to the locking element
head 23 to assist in the locking element's ability to ride over the
top of the bone screw head 32 during the bearing action when the
locking element is rotated. Alternatively, it is appreciated that
the bearing surface can be cammed, ramped or wedged. The cammed,
ramped or wedged features can also be used with the other locking
elements described herein.
[0175] Referring to FIGS. 6 and 10-13, it will be appreciated that
when the locking elements 20, 21 are rotated in the clockwise
direction with respect to the view of FIG. 6, a respective bearing
surface 48 will ride upon the curved top surface 39 of a respective
bone screw head 32 in order to positively lock the associated bone
screws 30 and the locking elements 20, 21 in place.
[0176] Alternatively, as shown in FIG. 21 in place of a bearing
surface 44, a ramp or wedge shaped surface 44 may be used to
increase the force applied to the bone screw head 32. When locked,
the leading end of the ramped portion of the locking element would
be lower than the prominence of the bone screw head 32 so that more
force is needed to lift the locking element and untighten it than
is needed for the locking element to remain tight and locked.
However, the locking element heads 23 need not have slots, be
cammed, or have a ramped surface to achieve the locking of the bone
screw 30 in place. Pressure, friction, interference fits, or other
engagement means capable of preventing the locking element from
moving from its locked position may be employed.
[0177] The rivet 202, shown in FIGS. 17-20 is intended for use in
association with plate 70 shown in FIGS. 14-15, is shown in detail
in cross section in FIGS. 19 and 20. The rivet 202 has a head 204,
a shaft 206, and an elongated bottom segment 208 for fitting within
the corresponding opening 200 in the plate 70. The lower surface
210 of the head 204 of the rivet 202 has an irregular surface which
may be cammed, such as on the bottom of locking element 20, 21, for
engaging the top surface 39 of the bone screw head 32. For use in
the end locking holes 19, the upper surface of the elongated bottom
segment 208 can have an irregular surface for cooperating with the
irregular surface of the bottom of the plate 70 to hold the rivet
202 in the locked position against the bone screw head 32, as shown
in FIG. 15. While the rivet of FIG. 18 is a separate, removable
component from the plate, the rivets, and particularly those for
use with the end locking holes, can be formed as part of the plate
during the manufacturing process of the plate and rivet can be non
removable.
[0178] Each of the above embodiments provides tight attachment of
the locking element relative the bone screw 30 and relevant
plate.
[0179] In the alternative embodiment of multiple locking plate 23
shown in FIG. 22, the locking element can be in the form of
threaded locking cap 300 shown in FIG. 23. The threaded locking cap
300 has a thread 302 on its outer circumference corresponding to
the thread 303 on the inner circumference of the locking element
depressions 304 in the top of the plate 230 shown in FIG. 22. The
locking cap 300 is relatively thin, particularly compared to its
width. The top 305 of locking cap 300 is provided with a
noncircular through hole 306 for receiving a similarly configured
driving tool.
[0180] Referring to FIGS. 28, 29, and 30 another embodiment of the
multiple locking plate generally referred to by the number 400 and
a locking element in the form of a thin locking member 412 are
shown. Plate 400 has an opening in its top surface for insertion of
the thin locking member 412, a recess 402 associated with each of
the bone screw receiving holes 408 and a slot 410 in the side wall
of the bone screw receiving holes 408 to permit the thin locking
member 412, having a series of thin projections or blades 414,
thinner than the slot 410, that give this locking member 412 an
appearance similar to that of a propeller. The thin locking member
412 is able to be rotated within the plate so as to not cover the
bone screw holes, thus allowing the thin locking member 412 to be
pre-installed prior to the installation of the bone screws by the
surgeon. Limited rotation of the thin locking member 412 allows the
blades 414 to protrude through the slot 410 and to cover a portion
of the top of the associated bone screws 30. The blades 414 of the
thin locking member 412 are flexible and, when rotated, slide over
the top surface 39 of the bone screw head 32 to lock the bone screw
30 in place. As with the other embodiments discussed, each of the
embodiments of the locking element is capable of locking more than
one bone screw 30. It is appreciated that the various multiple
locking plates and locking element combinations are capable of
locking as many as four bone screws at once, but are equally
effective for locking a lesser number or none at all, that is
securing itself to the plate.
[0181] It will be noted that one characteristic of each of the
above described locking element embodiments is to have a driver
engagement means, in these cases for example, a recess 24 as large
as the recess 34 in the bone screws 30 so that the same tool can be
used to turn both the bone screws 30 and the locking elements.
Also, the locking elements are sufficiently strong and have
sufficient mass so as to be able to withstand being locked without
breakage.
[0182] All of the shown examples of the multiple locking elements
that have a number of cutout portions have an arc with a radius
greater than that of the bone screw head. In addition, the head 23
of each locking element 20, 21 is provided at its center with a
noncircular recess 24, such as shown in FIG. 9 which is engageable
by an appropriate manipulation tool, such as shown in FIGS. 40-42.
In the embodiment of head 23 shown in FIG. 9, the associated tool
would have a hex head, but as discussed with regard to FIGS. 80 and
81, other shapes of recesses in the head 23 may be used. The thread
of each locking hole 12 and of each locking element 20, 21 has a
close tolerance so that they will reliably retain their
orientations so as to permit introduction of bone screws 30 into
bone screw receiving holes 6, 8 without interference.
[0183] It is appreciated that while various forms of locking
elements have been disclosed, in light of the teaching, other
equivalent means can be used for the purpose of locking the bone
screws 30 in place. In FIG. 83, an alternative multiple locking
plate 990 is shown having additional intermediate bone screw
receiving holes 980 and associated locking elements 960 for locking
bone screws 30 in place. Plate 990 allows for a more close spacing
and more pairs of bone screw holes than the number of vertebrae to
be engaged.
[0184] In FIGS. 84A-84E various plates 700a-g used for a single
level fusion are shown. Each of these plates 700a-g is designed to
span one spinal segment consisting of one disc space and two
adjacent vertebrae (containing the bone graft), and have bone
screws inserted into the end of the vertebrae through the bone
screw receiving holes 6 associated with the two adjacent vertebrae
and then locked in place. As shown in FIGS. 84A-84E, one locking
element 710, or two locking elements can be used to lock four bone
screws in place. In FIGS. 84A-84E, each of the plates 700a-e is
shown with the locking elements in their open orientation, before
being rotated to lock the bone screws.
[0185] Each of the above described plates can have the same
generally biconcave contour as already described for conforming to
the anterior aspect of the spine.
[0186] FIGS. 24A and 24B provide a side view of one embodiment of a
bone screw 30 according to the present invention. FIG. 27 is a top
view of the bone screw 30. At the center of bone screw head 32 is a
profiled recess 34 which may have the same form as the recess 24 of
each locking element 20, 21 in which case it may be turned with the
same tool as that employed for turning locking elements 20, 21. It
is appreciated that the driver engaging portion of the bone screw
30 could be slotted, and be either male or female (as is
shown).
[0187] In the embodiment of bone screw 30 shown in FIGS. 24A and
24B, the bone screw head 32 is stepped, with the first lower head
portion 35 being contiguous with the screw shank 33 and has a
smaller diameter than the upper portion of the bone screw head 32.
When this embodiment of bone screw 30 is employed, each bone screw
receiving hole 6, 8 of the plate 2 has a countersunk region 14
matching the diameter of the upper portion of the bone screw head
32 and dimensioned for an interference fit. The lower portion 35 of
the bone screw head 32 is dimensioned to achieve an interference
fit with its associated portion of bone screw receiving holes 6, 8.
The larger diameter upper portion of bone screw head 32 assures
that the bone screw 30 cannot be advanced completely through bone
screw receiving holes 6, 8 of plate 2. The bone screw 30 passes
completely through the upper surface of the plate 2 without
engaging the upper surface in any way.
[0188] As shown in FIG. 44, the head 32 of screw 30 passes
unobstructed through the upper surface of the plate until the lower
surface of enlarged screw head 32 engages the upper face of the
narrowed bone screw receiving portion at the midsubstance or below
the midsubstance of the plate. This is considered optimal for
allowing for the greatest screw to plate stability, even absent the
lock, against all forces except those reverse the path of
insertion, while still providing for the greatest plate strength
beneath the bone screw head 23. That is, since the plate is of only
generally 2-3 mm in thickness, a sheer vertical circumferential
wall is best able to constrain the motion of a screw if the head is
similarly configured and there is little tolerance between them.
Placing the support of the head near the mid thickness of the plate
is preferred as it allows the head to remain large to accommodate
the recess for the driver without being weakened, while placing the
support of the head away from the upper surface of the plate allows
the screw head to be deep into the plate. Placing the support of
the head at approximately the mid thickness of the plate assures
plenty of plate material beneath the head to support while
providing adequate head length above and below the contact point to
prevent the contact point from acting as a fulcrum by providing
adequate lever arms to prevent unwanted motion.
[0189] In the alternative embodiment of bone screw 30', as shown in
FIG. 25, bone screw head 32' is tapered in the direction from the
top of the bone screw head 32' toward screw tip 36'. Again, the
bone screw head 32' is dimensioned to achieve an interference fit
in the associated bone screw receiving hole 6,8 when the bone screw
30' has been fully installed. When this embodiment of bone screw
30' is employed, bone screw receiving holes 6, 8 need not be
provided with a countersunk region 4.
[0190] In each of the above embodiments of the bone screws, the
bone screws 30 and 30' present a unique combination of a tapered
screw shaft 33 and a helical thread 31. The diameter of screw shaft
33 generally increases from a distal portion of the shaft near the
screw tip 36 toward the proximal portion of the shaft near screw
head 32. In the preferred embodiment, the rate of increase in
diameter is also greater near the bone screw head 32. Such a shape
avoids stress risers and provides increased strength at the
screw-plate junction, where it is needed the most. The tapering of
screw shaft 33 may have a concave form, as shown in FIG. 24A, or
may be linear. The distal portion of the screw shaft 33 may assume
a constant diameter.
[0191] Referring again to FIGS. 24A and 24B, the thread 31 of the
bone screw 30 has a substantially constant outer, or crest,
diameter "d" from the proximal portion of the shaft below the bone
screw head 32 to the distal portion of the shaft near the bone
screw tip 36. In the screw tip 36, the crest diameter of thread 31
may be reduced for preferably one to two turns to facilitate the
insertion and penetration of the bone screw 30 into the bone.
[0192] In the preferred embodiment, the thread 31 of each bone
screw 30 has an outer diameter slightly smaller than the diameter
of the lowest portion 35 of the bone screw head 32, which is
adjacent the trailing, or upper, end of the associated thread 31.
In addition, the thread 31 is relatively thin, in the direction of
the longitudinal axis of the screw, and tapers outwardly, and has a
cross section of a triangle.
[0193] An example of the dimensions of a bone screw for use in
human anterior cervical spinal surgery for insertion into the
vertebrae is as follows: the threaded portion of said screw has a
length from about 10 mm to about 22 mm (12-18 mm preferred) and a
head length from about 1 mm to about 3 mm (2-2.5 mm preferred). The
threaded portion should have a maximum outside diameter from about
3.6 mm to about 5.2 mm (3.8-4.5 mm preferred) and the head has a
diameter from about 3.8 mm to about 6 mm (4-5.5 mm preferred). The
thread pitch is from about 1.25 mm to about 2.5 mm (1.5-2.0 mm
preferred) and has a sharp and thin threaded profile. The apex of
the two faces of the thread have an angle of less than about 21
degrees (15 degrees preferred) and the base of the thread is less
than about 0.60 mm thick (0.25 mm-0.35 mm preferred). The screw has
a root diameter that increases from proximately above the tip of
the shank, along the longitudinal axis to proximately below the
head portion of the screw. Preferably, the tip of the screw tip is
fluted by at least one cut out section so as to make the screw
self-tapping.
[0194] Even though the thread 31 of the bone screw 30 has a thin
profile, the thread will nevertheless be stronger than the bone
into which it is introduced so that this thread will efficiently
cut a thin helical groove in the bone tissue. The volume of bone
that will be displaced by the thickness of the thread is minimized
by the thin form of the thread, yet the substantial crest diameter
of the screw thread maximizes the surface area of the threads in
contact with the bone. While enlarging the screw shaft 33 diameter
near the bone screw head 32 increases its strength where needed,
reducing the screw shaft 33 diameter away from the bone screw head
32 where such strength is not required allows for the maximum area
of engagement for the thread 31 to the bone.
[0195] In the preferred embodiment, as shown in FIGS. 24A and 26,
bone screw tip 36 is provided with cutting flutes 38, to make the
bone screw 30 self-tapping. Unlike the prior art bone screws, used
for anterior cervical spinal surgery which are not self-tapping,
the thread form of the present invention screw is itself more like
a tap than a conventional screw in that the threads are very sharp
and fluted. Additional embodiments of the bone screws 30 is shown
in FIGS. 53-55.
[0196] By way of example, plates for fusing three adjacent
vertebrae (2 interspaces, or two spinal segments) are shown. Each
set of the bone screw receiving holes associated with a vertebrae
is considered to be a segment of the plate so that for example, in
FIG. 1 three segments are shown--an upper, a central, and a lower
segment. While the present discussion is in association with plates
for use in fusing three vertebrae across two interspaces, it should
be understood that longer and shorter plates having the appropriate
number and location of bone screw receiving holes corresponding to
the number of vertebrae to be fused are contemplated, and would
take the form of the plates shown with fewer or more intermediate
segments, such as the segment along line 9 of FIG. 1, or the
intermediate segments of the plates shown in FIGS. 82-84F.
[0197] Referring to FIGS. 31-42, an outline of the steps of the
method for installing the plates of the present invention is set
forth below. A detailed description of the instrumentation and
method for installing the plates of the present invention follows
the outline.
[0198] Step 1
[0199] Having completed the interbody fusions, the surgeon removes
any bone spurs or localized irregularities along the front of the
spine of the area to be fused.
[0200] Step 2
[0201] The correct length plate is selected by the surgeon by
measuring the distance on the spine by a caliper, ruler, template,
and the like. That plate having a length sufficient to span the
distance of the spine to be fused and to partially overlap a
portion of each of the end vertebrae to be fused.
[0202] Step 3
[0203] Utilizing a plate holder, the plate is placed into the wound
and positioned to confirm positioning, length, and screw hole
alignment relative to the segments of the spine to be fused.
[0204] Step 4
[0205] As shown in FIG. 31, with the plate thus positioned and
securely held, the plate may be attached to any of the vertebrae to
be fused (by example only, here shown as the top vertebra).
[0206] Sub-Step 4A
[0207] The pilot (guide) hole punch 60 is attached to the plate 2
as per FIG. 32, or alternatively, while not preferred the drill
guide may be used as per FIG. 37. In either event, the pilot hole
forming means rigidly aligns with and is captured by the plate bone
screw receiving hole wall.
[0208] Sub-Step 4B
[0209] The pilot hole is then formed by impacting the pilot hole
punch of FIG. 32 or drilling with the drill of FIG. 37. In the
alternative while not preferred, the formation of the pilot hole
can be done away with altogether and the correct screw selected so
as to have a length less than the distance along its path to the
posterior vertebral cortex can be directly inserted.
[0210] The determination of the appropriate screw length is made by
measuring or templating from radiographs, MRI's, or CT scans, or
determined directly by measuring the depth of the disc space.
[0211] Step 5
[0212] The correct screw is then attached to the screw driver which
regardless of the specific form of the screw driver engagement
means, is designed to have an interference fit so as to remain
firmly bound to the driver during transport to the insertion site.
FIGS. 41, 42, 63, 64, 80 and 81 show various ways of achieving such
a fit of the driver and screw. In addition to a wedging at the
screw and driver interface, clips, and springs and other means are
well known for temporarily and reversibly securing the screw to the
driver, such as is shown in FIG. 80 where a slotted inwardly
springing sleeve holds a threaded cap peripherally until, as it is
screwed into the plate, it is automatically pushed back releasing
the threaded cap.
[0213] Once a first bone screw has been fully inserted into a
vertebra through the plate, it is preferable to insert the other of
the transverse pair in the manner already described as per FIG.
33.
[0214] In a similar manner, it is possible to insert the remaining
bone screws as per the surgeon's preference into each of the
vertebrae to be included into the fusion, just the end vertebrae of
the fusion construct, or additionally place screws into the fusion
grafts.
[0215] However, as shown in FIGS. 33, 34, 38 and 39, it is possible
with the present invention at the surgeon's option to place any
portion or all of the fusion construct under compression and to do
so intersegmentally or across the entire length of the fusion
construct even when multi-segmented.
[0216] It is appreciated that the same procedure could be generally
used for any of the plate systems of the present invention.
[0217] As shown in FIG. 31, the vertebrae 50a-c are separated from
one another by fusion graft blocks 51 which were previously
installed in the spinal disc space between adjacent vertebrae 50
forming a fusion bone graft construct. Plate 2 is shown in FIG. 31
with the locking elements 20, 21 removed in order to simplify the
illustration. It will be understood, however, that in the preferred
embodiment the locking elements 20, 21 can be, and preferably are,
pre-installed in the positions shown in FIG. 6 prior to positioning
plate 2 upon vertebral bodies of the vertebrae 50, thereby saving
the surgeon time and trouble.
[0218] Plate 2 may be held in position by any known plate holding
means, but preferably by the holding tools shown in FIGS. 45, 46 or
70 by the notches 142 in the sides of the compression arms 104, 130
of a vertebral compressor tool 100 shown in FIG. 39, or as a
further alternative, by the unitary plate holder similar to the
FIG. 70 design.
[0219] As shown in FIG. 45, plate holder 870 has a hollow tubular
housing 872, with a central rod 874 having a thread 878 at one end
for engaging one of the threaded locking holes 12 in the plate 2.
The bottom end of the housing 872 has projections 880, 882 that
extend outwardly and then downwardly to fit into the bone screw
receiving holes 8 of the plate 2 preventing the housing 872 from
rotating. The central rod 874 is located in the housing 872 such
that it can be rotated by rotating a handle (not shown) which is
fixed to the central rod 874 at its upper end.
[0220] In FIG. 46 an alternative embodiment of the plate holder 890
is shown. A single solid member 890 has a threaded projection 894
at its bottom end for attachment to the central threaded locking
hole 12 in the plate. The bottom surface of the holder 890 of this
embodiment is contoured so as to match the contours of the top
surface of the plate adjacent to the locking hole 12, shown as a
depression 14.
[0221] Referring to FIGS. 67-68, an embodiment of a plate holder
for holding any of the plates while being positioned on the
vertebrae is shown and generally referred to by the number 800. The
plate holder 800 has a hollow tubular housing 802, with a central
rod 804 having a handle 806 at one end and a thread 808 at its
other end for engaging one of the threaded locking holes 12 in the
plate 600. The bottom end of the housing 802 has projections 810,
812 that extend outwardly and then downwardly 814, 816 to fit along
the side edge of the plate 2 between the end and intermediate lobes
4, preventing the housing 802 from rotating. The central rod 804 is
located in the housing 802 such that it can be rotated by rotating
the handle 806 which is fixed to the central rod 804 at its upper
end. This central rod 804 can also be attached to the housing 802
so that it can move up and down to some extent, by any number of
conventional ways, such as by having the central rod 804 have an
annular depression with a length of approximately 3-5 mm, and a set
screw projecting inward from the housing to engage the central rod
804. Once the plate 600 is in the proper place and the plate is
attached to one of the vertebrae by bone screws 30, the central rod
804 is disconnected from the opening in the plate 600 and the
holder 800 is removed.
[0222] FIG. 69A is an alternative embodiment of the plate holder
850. A single solid member 852 has a threaded projection 854 at its
bottom end for attachment to the central threaded locking hole 12
in the plate. The solid member 852 could also be threaded into a
bone screw receiving hole 6. The bottom surface of the holder 850
of this embodiment is contoured so as to match the contours of the
top surface of the plate adjacent to the locking hole 12, shown as
a depression 14.
[0223] FIG. 69B is another embodiment of the plate holder 850'. A
housing 851' having an end 853' configured to engage a bone screw
receiving hole 6 contains a rod 855' having an uneven diameter and
having a threaded portion 857'. As rod 855' is rotated by a handle
similar to handle 806 shown in FIG. 68, rod 855' screws downward
into the housing 851' into matching threads 858'. As the end of rod
855' is driven down, it spreads portions 859a' and 859b' (859c' and
859d' not shown) wedging plate holder 850' into a bone screw
receiving hole of the plate. Plate holder 850' is best used with
non-threaded bone screw receiving holes, but works for all types of
bone screw receiving holes.
[0224] Referring to FIG. 70, an alternative embodiment of the plate
holder referred to by the number 800' is shown in which there is a
removable handle 860 that is used for first attaching the plate
holder 800' to the plate, by rotating the shaft 804, and then for
holding the plate holder 800' off to the side by extension 864,
during the attachment procedure reducing the interference of the
plate holder 800 with the surgical procedure.
[0225] Referring to FIG. 38, a compression tool 100 is shown with a
toothed gear bar 102 having a first compression arm 104 secured to
its free end. Compression arm 104 has at its distal end a bore 106
for removably holding either a plate engaging element 108, shown in
FIG. 36, having a hook 110 at one end for engaging a depression or
notch 18 in the end of plate 2, or for removably holding a
compression post 54 shown in FIGS. 33-34. As shown in FIG. 36,
plate engaging element 108 includes a shaft 112 that will be
inserted into the corresponding bore 106 of compression arm 104,
and a flange 115 for resting against the bottom face of bore 106 to
accurately limit the depth of insertion of plate engaging element
108 into the bore 106. A ring spring 128, preferably of metal, is
located in an annular depression of the shaft 112, for holding the
plate engaging element 108 in the bore 106.
[0226] Referring to FIGS. 38-39, compression tool 100 includes a
second moveable compression arm 130 movable along toothed bar 102
parallel to first compression arm 104. The distal end of the second
compression arm 130 also has a bore 132, the same as bore 106, that
can receive a removable post 134. Bores 106 and 132 are the same so
that either compression arm 104, 130 can be used to hold the
removable post 134, permitting the compression tool 100 to be used
in any orientation. By permitting the plate engaging element 108
and the compression post 54 to both rotate and slide in the bores
106, 132 of the two compression arms 104, 130, with the plate
engaging hook 110 able to work even at an angle to the plate allows
for the apparatus to be readily attachable to the spine through the
compression post 54 and plate.
[0227] Compression arm 130 has a driving assembly consisting of a
toothed wheel (not visible) which is engaged with the tooth gear
138 of bar toothed gear 102 and is connected to compression arm 130
such that compression arm 130 is movable along the length of
toothed gear bar 102 by means of the rotation of handle 140, which
is connected to the toothed wheel. When the handle 140 is turned in
the direction of the arrow shown in FIG. 38, compression arm 130 is
moved toward compression arm 104. The driving assembly has a self
lock release mechanism whereby the movement of the two compression
arms 104, 130 away from one another is prevented, without the
activation of the release. On the inward distal end of each
compression arm, on facing sides, is a notch 142 or recess for
holding the plate 2 along its sides between the central lobes 4 and
end lobes 4, as shown in FIG. 37.
[0228] While the toothed gear bar 102 and compression arms 104, 130
have been described as being straight, it is possible that the
toothed gear bar 102 and compression arms 104, 130 may be arcuately
or otherwise shaped, so as to induce lordosis in the vertebrae, if
so desired.
[0229] As shown in FIG. 31, in the event that the compression tool
100 is used to hold the plate 2, the ends 144 of the compression
arms 104, 130 will be located in line with the fusion graft
construct 51 which was placed in the disc space when plate 2 is
properly positioned. A gap will exist between plate 2 and each
fusion graft construct 51, providing a space to accommodate the
free ends of arms 104, 130 should they extend beyond the bottom
surface of the plate 2. As will be described below, the same
compression tool 100 can also be used for compressing a plurality
of cervical vertebral bodies with bone grafts interposed during the
attachment of plate 2 to the vertebrae 50.
[0230] Referring to FIG. 31, plate 2 is held by a suitable holder,
in this case shown as the compression arms 104 and 130. Once the
appropriate length plate 2 has been properly positioned so that the
bone screw receiving holes 6 are aligned with each of the
respective vertebrae 50a-c to be fused, the next step is the
formation of bone screw receiving holes 6 prior to installation of
the bone screws 30 themselves in the vertebrae 50a. While the
procedure is described as first attaching the plate 2 to the upper
vertebrae 50a, the plate 2 can be attached to any of the vertebrae
in any order. Different sized plates are used so that, as indicated
above, the physician will select the appropriate sized plate in
which the bone screw receiving holes 6, 8 are aligned with the
three adjacent vertebrae 50a, 50b and 50c. Pilot holes are formed
by a pilot hole forming apparatus 60 shown in FIGS. 31 and 32.
Unlike with known prior art and screw plating systems, the bone
screws 30 may be inserted without the prior formation of an opening
into the vertebrae as the bone screws 30 are preferably sharp
pointed, self-tapping, and have at their tip a diminishing major
diameter to assist the screw entering and pulling into the bone.
However, while a hole into the bone of the vertebrae may be formed
prior to screw insertion, it is preferable that the hole be of a
smaller diameter than the root diameter of the screw and for a
different purpose than with the prior art. With the prior art the
hole drilled had to be of a diameter equal to but preferably larger
than the root (minor) diameter of the screw, as the screws were not
self-tapping. It is desirous to create pilot holes to assure that a
proper path for the bone screws 30 is maintained, and also to
prevent damage to the vertebral bone during insertion of the bone
screws 30. In addition, the pilot hole forming apparatus 60 creates
a more compact vertebral bone mass for reception of the
self-tapping bone screw 30 used in this insertion.
[0231] As shown in FIGS. 31 and 32, pilot hole forming apparatus 60
includes a hollow cylindrical housing 62 having a bottom provided
with a through hole 63. Housing 62 contains a central shaft 64
which extends through the through hole 63 in the bottom of housing
62. The leading end 66 of shaft 64 tapers gradually to a sharp
point 65. Shaft 64 is provided with a ring member 73 having a
diameter which closely corresponds to the inner diameter of housing
62 to guide the travel of shaft 64 within housing 62. A compression
spring 67 is interposed between the ring member 73 and the bottom
of housing 62. Compression spring 67 provides a bias force which
normally urges the sharp point 65 into a retracted position within
housing 62. The upper end of shaft 64 has an enlarged head 68
extending outside of the housing 62 which is intended to be
manually depressed or struck by a percussion instrument in order to
drive the sharp point 65 out of housing 62 and into a vertebral
body 50a. Shaft 64 is given a length, taking into account the
length that spring 67 will have when fully compressed, to determine
the maximum depth of the pilot hole formed in a vertebral body. The
depth is selected to assure that the pilot hole does not reach the
posterior cortex of the vertebral body, which borders the spinal
canal.
[0232] Certain structural features of hole forming apparatus 60 are
shown in greater detail in FIG. 32. In particular, it can be seen
that the bottom end of housing 62 has a projecting portion 69
dimensioned to fit precisely in a bone screw receiving hole 6 or 8
of plate 2. The bottom 71 of the projecting portion 69 is flat in a
plane perpendicular to the axis of housing 62. When the projecting
portion 69 of housing 62 is snugly inserted into a bone screw
receiving hole 6, 8 and the flat bottom 71 is placed flush against
the upper surface of plate 2, it is assured that the leading end 66
of shaft 64 will form a pilot hole in the vertebral bone having an
axis perpendicular to the plane of the associated portion of plate
2, thereby assuring that the bone screw 30 will be subsequently
installed so that its axis is also perpendicular to the plane which
is parallel to the upper and lower surfaces of the associated
portion of plate 2.
[0233] When a plate is used which has a threaded bone screw
receiving hole, the lower end of the pilot hole forming apparatus
60 is threaded so as to engage the thread in the bone screw
receiving hole 6, 8 thereby fixing the plate and the pilot hole
forming apparatus together, assuring a stable fit between the pilot
hole forming apparatus and the plate 2. It should be noted that the
diameter of the leading end 66 of the shaft 64 is small since it
has to fit within the small space left between the inside wall of
the pilot hole forming apparatus. Since it is only a pilot hole for
a self-tapping bone screw 30 that is being formed, the small
diameter is satisfactory.
[0234] Referring to FIG. 37, if for any reason it should be desired
to form the pilot hole in the vertebral body 50 by drilling, rather
than by the use of the pilot hole forming apparatus 60, use can be
made of a drill guide 80, having a lower end as shown in FIG. 37.
The drill 80 guide consists of a tubular member 82 and a small
diameter lower end 84 which is dimensioned to achieve a precise
interference fit in the associated bone screw receiving hole 6, 8
of plate 2. Along the small diameter lower end 84, drill guide 80
has an axial end surface in a plane perpendicular to the
longitudinal axis of the drill guide 80 so that when the small
diameter portion 84 is fitted into the bone screw receiving hole 6
and the surface surrounding the small diameter portion 84 is flush
against the upper surface of plate 2, the axis of the drill guiding
bore 86 in drill guide 80 will be precisely perpendicular to the
upper and lower surfaces of the associated portion of plate 2. As
with the case described above, the bottom end of the drill guide 80
can be threaded so as to engage to the threaded opening of plate
2.
[0235] After the bone screw receiving holes 6, 8 are formed in the
vertebral body 50a through the upper two bone screw securing holes
6 of plate 2 by means of either hole forming apparatus 60 or drill
guide 80, bone screws 30 are threaded into the vertebrae 50 while
holding the plate 2 firmly against the vertebrae 50 with
compression tool 100 or plate holder 800. This locks the plate to
the vertebrae 50a.
[0236] It is then possible, if desired, to compress the fusion
graft in the next adjacent vertebrae 50b before attaching bone
screws 30 to the adjacent vertebrae sob through the central bone
screw receiving holes of plate 2. Once the initial bone screws are
in place in the vertebrae 50a, the plate holder 100 or 800 may be
removed from the plate 2. The compression of the fusion graft
construct between the two adjacent vertebrae 50a and 50b is
achieved as follows:
[0237] Compression post 54 is driven through the central locking
hole 12 of plate 2 by means of insertion tool 90, shown in FIGS.
33, 34 and 35, into the vertebral bone of vertebra 50b, where it
will be used in a subsequent step to apply a compression force
between vertebrae 50a and 50b. Compression post 54 consists of a
shaft 56 having a sharp point 57 at its lower end, an enlarged
central collar 58 which serves as a depth stop, and a
circumferential groove 59 proximate its upper end, defining an
enlarged head 55.
[0238] Compression post insertion tool 90 consists of a shaft 92
having a closed hollow portion 94 at its lower end 96 for receiving
compression post 54 and an enlarged percussion cap 98 at its other
end. Compression post insertion tool 90 also includes in its lower
end 96 a second opening 95 having a recess 99 in its inside wall
for permitting engagement of the enlarged head 55 on the
compression post 54 within the depression 97. The second opening 95
is in communication with the hollow portion 94 of the insertion
tool 90, as shown in FIG. 35.
[0239] Referring to FIG. 38, the bore 132 in the second compression
arm 130 of compression tool 100 is then applied over compression
post 54 in vertebrae 50b, and the plate engaging element 108 is
inserted in the bore 106 of the first compression arm 104 of
compression tool 100. The hook 110 of the plate engaging element
108 shown in FIG. 36 is fitted into the notch 18 at the end of the
plate 2 which is fixed by the bone screws 30 inserted into the
vertebra 50a, as shown in FIG. 38. As indicated above, however, the
compression tool 100 can be rotated so that the first compression
arm 104 is now at the bottom and is able to fit over the
compression post 54 in vertebrae 50c.
[0240] Since the plate is attached to vertebrae 50a by means of
bone screws 30 and compression post 64 is fixed to the adjacent
vertebrae 50b, movement of the first and second compression arms
104 and 130 in the direction of vertebrae 50a by rotation of handle
140 results in compression of the bone graft construct 51 between
the adjacent vertebrae 50a and 50b. The distance of several
millimeters is sufficient for compression of the bone graft
construct 51. Once the desired compression is obtained, bone screw
pilot holes can be formed in vertebral body 50b by means of pilot
hole forming apparatus 60, as described above, for insertion of
bone screws 30 into bone screw receiving holes 8 of bone plate 2,
fixing the plate 2 to the adjacent vertebrae 50b. Compression tool
100 can then be withdrawn by activation of the release.
[0241] FIG. 39 illustrates the use of compression tool 100 to
induce compression between the lower two vertebral bodies 50b and
50c after bone screws 30 have been installed in the middle
vertebral body 50b as just described. As shown in FIG. 39,
compression post 54 remains in place in the middle vertebral body
50b and an additional compression post 54 is driven into the lower
vertebral body 50c by means of pilot hole forming tool 60 distal to
the plate itself in the recess between the end projections 4 to
allow for the lower compression post 64 to be moved towards
vertebrae 50b upwardly as shown. The original compression post 64
is inserted in bore 106 in the first compression arm 104 and the
additional compression post 54 is inserted into the bore 132 of the
second compression arm 130 of compression tool 100. Again, as
discussed above, the turning of the handle 140 results in the two
compression arms 104, 130 moving towards one another, resulting in
the compression post 54 in vertebrae 50c moving towards the upper
compression post 54 in vertebrae 50b, once again compressing the
fusion graft construct 51 between vertebrae 50b and 50c. The upper
compression post 54 in vertebrae 50b can not move since the
vertebrae 50b has been fixed to the plate by the insertion of the
bone screws 30 in the bone screw receiving holes 8 of the plate 2.
Thus, only the lower compression post 54 and vertebrae 50c can
move. As before, the pilot holes associated with vertebrae 50c are
formed and the bone screws 30 are inserted through bone screw
receiving holes 6. The compression tool 100 is then removed.
Compression post 54 is then extracted from the vertebrae by
inserting it in the second opening 95 of the compression post
insertion/removal tool 90, so that it engages the enlarged head 55
of the end of compression post 54 by depression 97, as shown in
FIG. 34.
[0242] It is recognized that other variations in the order of
compression may be employed. For example, during the compression of
the fusion graft construct 51 between vertebrae 50b and 50c, the
hook 110 of compression tool 100 may engage the notch 18 in the end
of the plate 2, and the other compression arm of the compression
tool 100 may engage the compression post 54 in the third adjacent
vertebrae 50c. It should also be noted that plate 2 has a recess
end cut out portion between the lobes at the end of the plate for
insertion of the compression post 54 in the vertebrae. Otherwise,
there may not be room below the end of the plate 2 for insertion of
the compression post 54.
[0243] It will be noted that the above-described procedure will be
performed with the bone screws 30 fully inserted into vertebral
bodies 50a, 50b and 50c and lordosis is maintained during
compression of the bone graft construct 51.
[0244] As indicated above, the procedure for attaching the plate 2
to the vertebrae 50a, 50b and 50c was illustrated without the
locking screws 20, 21 in place on the plate 2. FIG. 40 is a
perspective view showing the plate 2 of FIGS. 1-5, at a stage of a
surgical procedure when bone screws 30 have been fully installed in
three adjacent vertebrae 50a, 50b and 50c, and locking screws 20,
21 have been rotated through an angle of about 90.degree. to lock
three bone screws 30 in place; the left-hand locking screw 20 as
viewed has been rotated through an angle of about 60.degree. to
lock three bone screws 30 in place and the central locking screw 21
has been rotated through an angle of about 90.degree. to lock two
other bone screws 30 in place. At this time, one of the camming
surfaces 44 of each locking screw 20, 21 rests atop the screw head
32 of a respective bone screw 30.
[0245] Installation of the locking cap 300 can also be performed
with a tool 220 such as shown in FIGS. 41 and 42 having a suitably
shaped tip 222 with a length corresponding to the depth of hole 306
in a locking cap 300. The end 222 of tool 220 is flared just
proximal to the most distal end so that it creates a friction fit
with the screw cap 300 for ease of manipulation, and prevents the
screw cap 300 from falling off the tool 200.
[0246] FIG. 43 is a cross-sectional view in the plane of the center
of the two end locking screw holes 6 of plate 2, with two bone
screws 30 in their installed positions and locking element 21 in
its locking position. FIG. 44 is an enlarged view of one of the
bone screws 30 in plate 2 of FIG. 43. In a preferred embodiment,
the axis of each screw 30 is generally perpendicular to tangents to
the upper and lower surfaces of plate 2 at points which are
intersected by the longitudinal axis of the associated bone screw
30. Thus, because of the curvature of plate 2 in the plane of FIG.
18, bone screws 30 can be directed so as to converge toward one
another at a desired angle. The axis of the two bone screws 30
shown in FIG. 18 may subtend an angle of about 45.degree..
Alternatively, the curvature of the plate from side to side may be
so as to conform to the surface of the anterior aspect of the human
adult cervical spine and the axis of the paired screw hole may
deviate from being perpendicular to the plate when viewed on end to
achieve optimal convergence.
[0247] Because the bone screws 30, once inserted, are locked to the
plate, a "claw" of a rigid triangular frame structure is obtained
at each pair of bone screws 30 such that the attachment of plate 2
to the vertebral bodies 50a, 50b and 50c would be highly secure due
to the trapping of a wedged mass of bone material between the
angled bone screws triangle, even if any thread stripping should
occur. The "claw" may be further formed by three angled bone screws
in a tripod configuration or by four bone screws in a four sided
claw configuration.
[0248] A plating system according to each of the above embodiments
can be installed in the same manner as described above, and using
the same instruments and tools, as illustrated and described above
with respect to the first embodiment. In the case of the embodiment
shown in FIG. 22, the compression operations would be performed by
means of slot 604 instead of the middle locking screw hole 12.
[0249] b.) The Single Locking Plate Systems
[0250] The single locking plate system will now be described. FIGS.
47-52 are views of a first embodiment of a single locking plate
system. The contour of plate 600 is the same as the plate 2 shown
in FIGS. 1-5. Plate 600 contains bone screw receiving holes 602
which are internally threaded 603 for receiving corresponding
locking elements in the form of a locking cap 610, shown in FIGS.
56-59. For example, in plate 600, the bone screw hole 602 has an
outer diameter of approximately 5 mm with a preferred range of 4-6
mm; and a threaded inner diameter of approximately 4.8 mm, with a
range of 3.5-5.8 mm for this use. Attaching means other than
threads may be used, such as bayonet type attachment elements.
[0251] The bottom of each bone screw receiving hole 602 has an
inwardly stepped portion of properly selected dimensions for
retaining an associated bone screw 170, as shown in FIGS. 53-55. As
described in greater detail below, in this embodiment, a single
locking element in the form of a locking cap 610 having threads 608
shown in FIGS. 56-59, is associated with each of the bone screws
receiving holes 602.
[0252] The difference between the bone screw 170 used in the single
locking embodiment of the plate from the bone screw used in
association with the multiple locking plate is essentially due to
the fact that whereas in the multiple locking plate embodiment the
locking elements slide over a portion of the top 39 of the screw
head 32, in the single locking embodiment the locking cap 610 fits
over the head 172 of the bone screw 170. Therefore, the head 172 of
the bone screw 170 of the present embodiment need not be smooth.
This permits the head 172 of this embodiment bone screw 170 to be
thicker and stronger.
[0253] FIG. 63 shows two bone screws 170 and associated threaded
locking caps 610 in their fully installed positions. In these
positions, head portions 174 and 176 of each bone screw 170 form an
interference fit with corresponding portions of an associated bone
screw receiving hole 602. Rim 612 of each threaded locking cap 610
forms an interference fit with upper portion 178 of the head of its
associated bone screw 170. Because the thread 608 of each locking
cap 610 mates precisely with the internal thread in an associated
bone screw receiving hole 602, each threaded locking cap 610 is
additionally subjected to a clamping force between associated head
portion 178 and the internal threads 603 of associated bone screw
receiving hole 602. The rounded head 614 of each threaded locking
cap 610 assures that the upper surface of an assembled plating
system will be free of sharp edges, or projections.
[0254] Referring to FIGS. 80 and 81 tools for use in inserting both
the bone screws and the locking cap in the single locking plate 600
are shown. In the first embodiment of the driving tool 1000 shown
in FIG. 80, the tool 1000 has an outer tubular housing 1002. Within
the housing 1002 is a torks type or hexagonal driver 1004 that has
a projecting end 1006 that corresponds to the recess 306 in the cap
610 for engagement with the cap 610. As indicated above, the driver
1004 is configured so that it makes a firm attachment for the
locking cap 610 for holding the locking cap 610 firmly to the
driver. The hex driver 1004 is hollow so as to be able to permit
the shaft 1010 of a Phillips or torks screw driver to fit through
the hollow portion 1012 for engagement by its tip 1012 with the
corresponding recess 180 of bone screw 170 for engagement by the
end 1006 of the driver 1004. The shaft 1010 of the driver 1000 is
longer than the tubular housing and driver 1004 has an upper end
(not shown) extending from the top end of the tubular housing 1002
so that it can be rotated by the handle.
[0255] The housing 1002 has a diameter that permits the locking cap
610 to be held within the inner end of the tubular housing 1002 by
a friction fit or to the driver 1004. It is appreciated that other
methods of holding the locking cap 610 within the end of the
tubular housing 1000 may also be employed.
[0256] As shown in FIG. 80, the operation of the bone screw and
locking element driver 1000 is as follows: the cap 610 is inserted
onto the end of the cap driver 1004, and then the cap driver 1004
with the shaft 1010 of the bone screw driver passing through the
central longitudinal opening of the cap driver. As shown, the bone
screw driver shaft 1010 passes through the recess 306 in the cap
610 and engages the recess 180 in the head of the bone screw 170.
The bone screw 170 is shown being installed in a bone screw
receiving hole in the plate 600. The handle (not shown) of the bone
screw driver is rotated, thereby screwing the bone screw 170 in
place. Since the diameter of the bone screw driver is less than the
width of the recess 306 of the cap 610, the bone screw driver 1010
is able to rotate without rotation of the cap 610.
[0257] The hollow tubular housing 1002 rests on the top surface of
the plate 600 and assists in the alignment of the shaft 1010 in
relationship to the plate. Once the bone screw 170 is inserted, the
cap driver 1004 is depressed until the threads 608 on the outside
of the cap 610 engages the threads 603 of the bone screw receiving
hole. The cap driver 1004 is then turned until the cap 610 is
securely locked in place.
[0258] In FIG. 81, an alternative embodiment of the combination
bone screw and locking cap driver is shown. In this embodiment, a
housing is not used. Instead, the cap driver 1010 holds the cap 610
by friction and the handle 620 for the bone screw driver 1010 is
rotated. A ball spring 622 assembly holds the cap driver 1002 up
until the bone screw has been screwed into the bone screw receiving
hole. Driver 1010 has an elongated portion that once the bone screw
has been installed, the ball spring 622 is depressed and the handle
624 associated with the cap driver is permitted to descend for
rotation of the cap 610. A tubular housing can be employed to
assist in aligning of the cap 610 in the bone screw receiving hole,
as indicated above.
[0259] The drivers shown in FIGS. 80 and 81 simplify the procedure,
and reduce the number of instruments that are necessary to be used
during the installation procedure. The procedure is quick and
reliable, giving the physician more assurance that small watch
parts will not be lost or difficult to manipulate.
[0260] FIG. 52 is a top view of the plate 600 partially installed,
with threaded locking caps 600 installed in bone screw receiving
holes 602.
[0261] FIGS. 54-56 show a bone screw 170 for use with the single
locking plating system according to the invention. Bone screw 170
differs from bone screw 30 previously described in detail, only
with regard to the stepped configuration of head 172. Preferably,
bone screw 170 includes a lower portion 174 which is contiguous
with the screw shank and has a reduced diameter equal to the
maximum diameter of the shank 176. Portion 178 of head 172 also has
smaller diameter than lower portion 174. The thread 182 has the
same configuration as for the bone screw 30 discussed above.
However, either embodiment of bone screws can be used with any of
the plates.
[0262] As in the case of the multiple locking plating system
described above, the bone screws 170 for use in the single locking
plating system are preferably solid, where the screws adjoin the
lower plate surface, where screws used with prior art plates are
most prone to breakage, the only recess in the heads being for
engagement of the tip 222 of driving tool 220 and with the recess
being above the critical area. Therefore, these bone screws 170
remain robust. The screw heads are not deeply slitted into portions
and the locking caps do not impose a radial outer force on the
associated bone screw heads so the screw heads do not spread apart
so as to be stressed and weakened.
[0263] Referring to FIGS. 71, 73 and 75 another alternative
embodiment of the single locking plate system of the present
invention is shown and referred to by the number 500. The plate 500
has the same contour as the plate 2 shown in FIGS. 1-5, but
associated with each of the bone screw openings 502, are threaded
openings 524 offset from the bone screw openings 502 for receiving
the locking element 506, 508, shown in FIGS. 72 and 74 as a
threaded locking set screw or cap 506 or screw 508.
[0264] It is appreciated that other configurations of single
locking plates may be employed. Referring to FIG. 82, a single
locking plate 900 is shown in which there are a pair of bone screw
receiving holes 910 at its ends 930 and a number of bone screw
receiving holes 950 along the longitudinal axis of the plate 900.
The additional bone screw receiving holes 950 permit a single plate
to be able to be aligned with a number of different sized vertebrae
disc spaces, and bone fusion grafts. As indicated above, the plate
of the present invention shown in FIGS. 1-5, requires that a
properly sized plate be selected by the surgeon so that each pair
of bone screw receiving holes 6, 8 line up with the appropriate
vertebrae. This requires a number of different sized plates to be
available for optimum attachment of the bone screw receiving holes
to each of the vertebrae. With the plate 900 of FIG. 82, the close
spacing and increased number of central openings permit the surgeon
to locate at least one appropriate opening to be aligned with each
of the intermediate vertebrae, and/or bone grafts.
[0265] The procedure for installation of the single locking plates
is substantially the same as described herein in detail for the
multiple locking plates. The central longitudinal slot 670 in the
single locking plates is used for the compression procedure. The
same instrumentation is used to create the plate hole either by
means of a punch or a drill. FIGS. 60-69 show the various steps in
the procedure for installation of the single locking plates,
comparable to the steps employed in the installation of the
multiple locking plates.
[0266] Referring to FIGS. 76-79 the heads 507 and 526 of the
locking elements 508 and 522 have a recess 510 and 524
corresponding to the radius of the bone screw openings 502 and 528
so that the locking element 508 and 522 may be installed in place
prior to the insertion of the bone screw 170 into the bone screw
receiving hole 502 and 528. When the locking elements 508 and 522
are rotated, a portion of its head extends over the top of the head
of bone screw 170 to lock it in place. As with the above
embodiments, the bottom surface of the locking screws 508 and 522
can have a camming or other configuration for engagement with the
top surface 39 of the associated bone screw 170.
[0267] While the plate instrumentation and method have been
described in association with attaching a plate to the vertebrae of
the spine, it should be appreciated that the plates can be adopted
for specification to other parties of the body. However, the
dimensions of the plate, the specific contours and placement of the
bone screw receiving holes would have to be modified.
[0268] Similarly, the bone screws described in this application
could be used in other parts of the body, again being modified so
as to serve their intended purposed, depending on the size of the
body part in which they are to be installed.
[0269] While particular embodiments of the present invention have
been shown and described, it will be obvious to those skilled in
the art that changes and modifications may be made without
departing from this invention in its broader aspects and,
therefore, the aim in the appended claims is to cover all such
changes and modifications as fall within the true spirit and scope
of this invention.
[0270] While specific innovative features may have been presented
in reference to specific examples, they are just examples, and it
should be understood that various combinations of these innovative
features beyond those specifically shown are taught such that they
may now be easily alternatively combined and are hereby anticipated
and claimed.
* * * * *