U.S. patent application number 10/382715 was filed with the patent office on 2003-07-24 for threaded spinal implant for insertion between vertebral bodies.
This patent application is currently assigned to Karlin Technology, Inc.. Invention is credited to Michelson, Gary Karlin.
Application Number | 20030139816 10/382715 |
Document ID | / |
Family ID | 26900886 |
Filed Date | 2003-07-24 |
United States Patent
Application |
20030139816 |
Kind Code |
A1 |
Michelson, Gary Karlin |
July 24, 2003 |
Threaded spinal implant for insertion between vertebral bodies
Abstract
An artificial spinal implant is disclosed which when placed
between two adjacent vertebrae directly participates and is
incorporated in the ensuing fusion. Instrumentation and procedure
is also disclosed.
Inventors: |
Michelson, Gary Karlin;
(Venice, CA) |
Correspondence
Address: |
MARTIN & FERRARO
14500 AVION PARKWAY
SUITE 300
CHANTILLY
VA
201511101
|
Assignee: |
Karlin Technology, Inc.
|
Family ID: |
26900886 |
Appl. No.: |
10/382715 |
Filed: |
March 5, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10382715 |
Mar 5, 2003 |
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08480684 |
Jun 7, 1995 |
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08480684 |
Jun 7, 1995 |
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07968240 |
Oct 29, 1992 |
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5741253 |
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07968240 |
Oct 29, 1992 |
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07698674 |
May 10, 1991 |
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07698674 |
May 10, 1991 |
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07205935 |
Jun 13, 1988 |
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5015247 |
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Current U.S.
Class: |
623/17.11 |
Current CPC
Class: |
A61F 2002/4619 20130101;
A61B 2090/036 20160201; A61F 2002/4627 20130101; A61F 2002/4629
20130101; A61F 2/4611 20130101; A61F 2002/30405 20130101; A61F
2230/0017 20130101; A61B 17/1757 20130101; A61F 2/446 20130101;
A61F 2/442 20130101; A61F 2002/2835 20130101; A61F 2002/30143
20130101; A61F 2002/3085 20130101; A61F 2230/0069 20130101; A61F
2/4603 20130101; A61B 2017/0256 20130101; A61F 2220/0025 20130101;
A61B 17/8888 20130101; A61F 2002/30235 20130101; A61F 2002/448
20130101; A61F 2002/4681 20130101; A61B 17/1671 20130101; A61F
2002/30785 20130101; A61F 2/30744 20130101; A61F 2002/30593
20130101; A61F 2002/30787 20130101; A61F 2002/30774 20130101 |
Class at
Publication: |
623/17.11 |
International
Class: |
A61F 002/44 |
Claims
What is claimed is:
1. An at least in part hollow artificial interbody spinal fusion
implant for insertion at least in part in between the external
perimeters of two spaced apart vertebral bodies of a human spine,
said implant comprising: opposed arcuate portions each having an
interior facing surface and an exterior facing surface, said
interior facing surfaces being spaced apart to define a hollow
interior, each of said opposed arcuate portions having at least one
opening therethrough in communication with said hollow interior;
and a thread on at least a portion of said exterior facing surfaces
of said opposed arcuate portions.
2. The spinal implant of claim 1, wherein said implant is at least
in part cylindrical.
3. The spinal implant of claim 1, wherein said implant has a
mid-longitudinal axis and has a generally circular cross-section
transverse to the mid-longitudinal axis over at least a portion
thereof.
4. The spinal implant of claim 1, wherein said implant has opposite
ends between said opposed arcuate portions, at least one of said
ends being at least in part open.
5. The spinal implant of claim 4, wherein said at least one end
being at least in part open is configured to threadably engage a
length extending member.
6. The spinal implant of claim 4, wherein said at least one end
being at least in part open is adapted to threadably engage an end
cap.
7. The spinal implant of claim 6, wherein said end cap is a length
extending member.
8. The spinal implant of claim 7, wherein said length extending
member is adapted to contact at least one of the spaced apart
vertebral bodies.
9. The spinal implant of claim 1, wherein said opposed arcuate
portions include a plurality of said openings therethrough.
10. The spinal implant of claim 4, wherein said implant has a
maximum diameter and a maximum length from one of said opposite
ends to the other of said opposite ends, said maximum length being
greater than said maximum diameter.
11. The spinal implant of claim 1, wherein said thread on said
exterior facing surfaces is not continuous.
12. The spinal implant of claim 1, wherein said thread has at least
one interruption.
13. The spinal implant of claim 1, wherein said exterior facing
surfaces are not threaded between spaced apart portions of said
exterior facing surfaces that are threaded.
14. The spinal implant of claim 1, in combination with bone.
15. The spinal implant of claim 14, wherein said bone is loaded in
said hollow interior of said implant.
16. The spinal implant of claim 14, wherein said bone is
compressively loaded in said implant.
17. The spinal implant of claim 1, in combination with a fusion
promoting substance other than bone.
18. The spinal implant of claim 1, wherein said implant comprises
at least in part a fusion promoting substance.
19. The spinal implant of claim 1, wherein said implant is treated
with a fusion promoting substance.
20. The spinal implant of claim 1, in combination with a source of
osteogenesis.
21. The spinal implant of claim 1, wherein said implant comprises
an implantation material that is stronger than bone.
22. The spinal implant of claim 1, wherein said implant comprises
an implantation material that comprises a bone ingrowth
material.
23. The spinal implant of claim 1, wherein said implant is in
combination with an implantation material that intrinsically
participates in the growth of bone through said implant.
24. The spinal implant of claim 1, wherein said opposed arcuate
portions have a porous surface.
25. The spinal implant of claim 1, wherein said implant comprises
an implantation material that is porous.
26. The spinal implant of claim 1, wherein said implant comprises
an ASTM implant quality material.
27. The spinal implant of claim 26, wherein said ASTM quality
material comprises titanium.
28. An at least in part hollow artificial interbody spinal fusion
implant for insertion at least in part in between the external
perimeters of two spaced apart vertebral bodies of a human spine,
said implant comprising: a body having a generally cylindrical
sidewall and a mid-longitudinal axis, said body having opposite
ends in a plane generally perpendicular to the mid-longitudinal
axis, said sidewall having an exterior surface and an interior
surface defining a hollow interior of said implant, said sidewall
having a plurality of openings therethrough in communication with
said hollow interior; a thread on at least a portion of said
exterior surface of said sidewall; and an end member for
cooperatively engaging at least one of said opposite ends of said
body, said end member extending from said body when engaged to said
body.
29. The spinal implant of claim 28, wherein said end member
extending from said body comprises a portion of the length of said
implant.
30. The spinal implant of claim 28, wherein at least one of said
opposite ends is configured to threadably engage said end
member.
31. The spinal implant of claim 28, wherein at least one of said
opposite ends is at least in part open.
32. The spinal implant of claim 31, wherein said at least one end
being at least in part open is adapted to threadably engage said
end member.
33. The spinal implant of claim 28, wherein said end member is
adapted to contact at least one of the spaced apart vertebral
bodies.
34. The spinal implant of claim 28, wherein at least said one of
said openings is between at least a portion of said thread.
35. The spinal implant of claim 28, wherein said body has a maximum
diameter and a maximum length from one of said opposite ends to the
other of said opposite ends, said maximum length being greater than
said maximum diameter.
36. The spinal implant of claim 28, wherein said thread on said
exterior surface is not continuous.
37. The spinal implant of claim 28, wherein said thread on said
exterior surface has at least one interruption.
38. The spinal implant of claim 28, wherein said exterior surface
is not threaded between spaced apart portions of said exterior
surface that are threaded.
39. The spinal implant of claim 28, in combination with bone.
40. The spinal implant of claim 39, wherein said bone is loaded in
said hollow interior of said implant.
41. The spinal implant of claim 39, wherein said bone is
compressively loaded in said implant.
42. The spinal implant of claim 28, in combination with a fusion
promoting substance other than bone.
43. The spinal implant of claim 28, wherein said implant comprises
a fusion promoting substance.
44. The spinal implant of claim 28, wherein said implant is treated
with a fusion promoting substance.
45. The spinal implant of claim 28, in combination with a source of
osteogenesis.
46. The spinal implant of claim 28, wherein said implant comprises
an implantation material that is stronger than bone.
47. The spinal implant of claim 28, wherein said implant comprises
an implantation material that comprises a bone ingrowth
material.
48. The spinal implant of claim 28, wherein said implant is in
combination with an implantation material that intrinsically
participates in the growth of bone through said implant.
49. The spinal implant of claim 28, wherein said exterior surface
is at least in part porous.
50. The spinal implant of claim 28, wherein said implant comprises
an implantation material that is porous.
51. The spinal implant of claim 28, wherein said implant comprises
an ASTM implant quality material.
52. The spinal implant of claim 51, wherein said ASTM quality
material comprises titanium.
53. A spinal fusion system comprising: a first interbody spinal
fusion implant for insertion at least in part in between the
external perimeters of two spaced apart vertebral bodies of a human
spine, said implant comprising opposed arcuate portions each having
an interior facing surface and an exterior facing surface, said
interior facing surfaces being spaced apart to define a hollow
interior, each of said opposed arcuate portions having at least one
opening therethrough in communication with said hollow interior,
and a thread on at least a portion of said exterior facing surfaces
of said opposed arcuate portions; and a second spinal implant
adapted to penetrably engage each of the spaced apart vertebral
bodies, said second spinal implant comprising an elongated member
having a plurality of openings therethrough along at least a
portion of the length of said second spinal implant.
54. The spinal fusion system of claim 53, wherein said second
spinal implant includes a threaded member for penetrably engaging
at least one of the spaced apart vertebral bodies.
55. The spinal fusion system of claim 53, wherein said first
implant is at least in part cylindrical.
56. The spinal fusion system of claim 53, wherein said first
implant has a mid-longitudinal axis and has a generally circular
cross-section transverse to the mid-longitudinal axis over at least
a portion thereof.
57. The spinal fusion system of claim 53, wherein said first
implant has opposite ends between said opposed arcuate portions, at
least one of said ends being at least in part open.
58. The spinal fusion system of claim 57, wherein said at least one
end being at least in part open is configured to threadably engage
a length extending member.
59. The spinal fusion system of claim 57, wherein said at least one
end being at least in part open is adapted to threadably engage an
end cap.
60. The spinal fusion system of claim 59, wherein said end cap is a
length extending member.
61. The spinal fusion system of claim 60, wherein said length
extending member is adapted to contact at least one of the spaced
apart vertebral bodies.
62. The spinal fusion system of claim 53, wherein each of said
opposed arcuate portions includes a plurality of said openings
therethrough.
63. The spinal fusion system of claim 57, wherein said first
implant has a maximum diameter and a maximum length from one of
said opposite ends to the other of said opposite ends, said maximum
length being greater than said maximum diameter.
64. The spinal fusion system of claim 53, wherein said thread on
said exterior facing surfaces is not continuous.
65. The spinal fusion system of claim 64, wherein said thread has
at least one interruption.
66. The spinal fusion system of claim 53, wherein said exterior
facing surfaces are not threaded between spaced apart portions of
said exterior facing surfaces that are threaded.
67. The spinal fusion system of claim 53, in combination with
bone.
68. The spinal fusion system of claim 67, wherein said bone is
loaded in said hollow interior of said first implant.
69. The spinal fusion system of claim 67, wherein said bone is
compressively loaded in said first implant.
70. The spinal fusion system of claim 53, in combination with a
fusion promoting substance other than bone.
71. The spinal fusion system of claim 53, wherein said first
implant comprises at least in part a fusion promoting
substance.
72. The spinal fusion system of claim 53, wherein said first
implant is treated with a fusion promoting substance.
73. The spinal fusion system of claim 53, in combination with a
source of osteogenesis.
74. The spinal fusion system of claim 53, wherein said first
implant comprises an implantation material that is stronger than
bone.
75. The spinal fusion system of claim 53, wherein said first
implant comprises an implantation material that comprises a bone
ingrowth material.
76. The spinal fusion system of claim 53, in combination with an
implantation material that intrinsically participates in the growth
of bone through said first implant.
77. The spinal fusion system of claim 53, wherein said opposed
arcuate portions have a porous surface.
78. The spinal fusion system of claim 53, wherein said first
implant comprises an implantation material that is porous.
79. The spinal fusion system of claim 53, wherein at least one of
said first implant and said second implant comprises an ASTM
implant quality material.
80. The spinal fusion system of claim 79, wherein said ASTM quality
material comprises titanium.
81. A spinal fusion system comprising: an interbody spinal fusion
implant having a body for placement in between the external
perimeters of spaced apart vertebral bodies, said body having at
least in part a generally cylindrical sidewall with an exterior
surface, said cylindrical side wall having a plurality of
perforations therethrough, said exterior surface of said
cylindrical sidewall being at least in part threaded; and
additional orthopedic hardware comprising at least one threaded
member for threadably engaging said body at one end.
82. The spinal fusion system of claim 81, wherein said body has
opposite ends.
83. The spinal fusion system of claim 82, further comprising an end
member for cooperatively engaging at least one of said opposite
ends of said body, said end member extending from said body when
engaged to said body.
84. The spinal fusion system of claim 83, wherein said end member
extending from said body comprises a portion of the length of said
implant.
85. The spinal fusion system of claim 83, wherein at least one of
said opposite ends is configured to threadably engage said end
member.
86. The spinal fusion system of claim 83, wherein at least one of
said opposite ends is at least in part open.
87. The spinal fusion system of claim 86, wherein said at least one
end being at least in part open is adapted to threadably engage
said end member.
88. The spinal fusion system of claim 83, wherein said end member
is adapted to contact at least one of the spaced apart vertebral
bodies.
89. The spinal fusion system of claim 81, wherein said sidewall
includes a plurality of said openings therethrough.
90. The spinal fusion system of claim 81, wherein said body has a
maximum diameter and a maximum length from one of said opposite
ends to the other of said opposite ends, said maximum length being
greater than said maximum diameter.
91. The spinal fusion system of claim 81, wherein said thread on
said exterior surface is not continuous.
92. The spinal fusion system of claim 81, wherein said thread on
said exterior surface has at least one interruption.
93. The spinal fusion system of claim 81, wherein said exterior
surface is not threaded between spaced apart portions of said
exterior surface that are threaded.
94. The spinal fusion system of claim 81, in combination with
bone.
95. The spinal fusion system of claim 94, wherein said bone is
loaded in said hollow interior of said implant.
96. The spinal fusion system of claim 94, wherein said bone is
compressively loaded in said implant.
97. The spinal fusion system of claim 81, in combination with a
fusion promoting substance other than bone.
98. The spinal fusion system of claim 81, wherein said implant
comprises a fusion promoting substance.
99. The spinal fusion system of claim 81, wherein said implant is
treated with a fusion promoting substance.
100. The spinal fusion system of claim 81, in combination with a
source of osteogenesis.
101. The spinal fusion system of claim 81, wherein said implant
comprises an implantation material that is stronger than bone.
102. The spinal fusion system of claim 81, wherein said implant
comprises an implantation material that comprises a bone ingrowth
material.
103. The spinal fusion system of claim 81, in combination with an
implantation material that intrinsically participates in the growth
of bone through said implant.
104. The spinal fusion system of claim 81, wherein said exterior
surface is at least in part porous.
105. The spinal fusion system of claim 81, wherein said implant
comprises an implantation material that is porous.
106. The spinal fusion system of claim 81, wherein said implant
comprises an ASTM implant quality material.
107. The spinal fusion system of claim 106, wherein said ASTM
quality material comprises titanium.
Description
[0001] The present invention relates to an artificial fusion
implant to be placed into the intervertebral space left after the
removal of a damaged spinal disc.
[0002] The purpose of the present invention is to provide an
implant to be placed within the intervertebral disc space and
provide for the permanent elimination of all motion at that
location. To do so, the device is space occupying within the disc
space, rigid, self-stabilizing to resist dislodgement, stabilizing
to the adjacent spinal vertebrae to eliminate local motion, and
able to intrinsically participate in a vertebral to vertebrae bony
fusion so as to assure the permanency of the result.
[0003] At present, following the removal of a damaged disc, either
bone or nothing is placed into the space left. Placing nothing in
the space allows the space to collapse which may result in damage
to the nerves; or the space may fill with scar tissue and
eventually lead to a reherniation. The use of bone is less than
optimal in that the bone obtained from the patient requires
additional surgery and is of limited availability in its most
useful form, and if obtained elsewhere, lacks living bone cells,
carries a significant risk of infection, and is also limited in
supply as it is usually obtained from accident victims.
Furthermore, regardless of the source of the bone, it is only
marginal structurally and lacks a means to either stabilize itself
against dislodgement, or to stabilize the adjacent vertebrae.
[0004] A review of related prior art will demonstrate the novelty
of the present invention.
[0005] There have been an extensive number of attempts to develop
an acceptable disc prothesis (an artificial disc). Such devices by
design would be used to replace a damaged disc and seek to restore
the height of the interspace and to restore the normal motion of
that spinal joint. No such device has been found that is medically
acceptable. This group of prosthetic or artificial disc
replacements, seeking to preserve spinal motion and so are
different from the present invention, would include:
[0006] U.S. Pat. No. 3,867,728 STUBSTAD--describing a flexible disc
implant.
[0007] U.S. Pat. No. 4,349,921 KUNTZ--describing a flexible disc
replacement with file like surface projections to discourage device
dislocation.
[0008] U.S. Pat. No. 4,309,777 PATIL--describing a motion
preserving implant with spiked outer surfaces to resist dislocation
and containing a series of springs to urge the vertebrae away from
each other.
[0009] U.S. Pat. No. 3,875,595 FRONING--describing a motion
preserving bladder like disc replacement with two opposed stud-like
projections to resist dislocation.
[0010] U.S. Pat. No. 2,372,622 FRENCH (FASSIO)--describing a motion
preserving implant comprising complimentary opposed convex and
concave surfaces.
[0011] In summary then, these devices resemble the present
invention only in that they are placed within the intervertebral
space following the removal of a damaged disc. In that they seek to
preserve spinal motion, they are diametrically different from the
present invention which seeks to permanently eliminate all motion
at that spinal segment.
[0012] A second related area of prior art includes those devices
utilized to replace essentially wholly removed vertebrae. Such
removal is generally necessitated by extensive vertebral fractures,
or tumors, and is not associated with the treatment of disc
disease. While the present invention is to be placed within the
disc space, these other vertebral devices cannot be placed within
the disc space as at least one vertebrae has already been removed
such that there no longer remains a "disc space." Furthermore,
these devices are limited in that they seek to perform as temporary
structural members mechanically replacing the removed vertebrae
(not a removed disc), and do not intrinsically participate in
supplying osteogenic material to achieve cross vertebrae bony
fusion. Therefore, again unlike the present invention which
provides for a source of osteogenesis, use of this group of devices
must be accompanied by a further surgery consisting of a bone
fusion procedure utilizing conventional technique. This group
consisting of vertebral struts rather than disc replacements would
include the following:
[0013] U.S. Pat. No. 4,553,273 WU--describing a turnbuckle like
vertebral strut.
[0014] U.S. Pat. No. 4,401,112 REZAIAN--describing a turnbuckle
like vertebral strut with the addition of a long stabilizing staple
that spans the missing vertebral body.
[0015] U.S. Pat. No. 4,554,914 KAPP--describing a large
distractible spike that elongates with a screw mechanism to span
the gap left by the removal of a entire vertebrae and to serve as
an anchor for acrylic cement which is then used to replace the
missing bone (vertebrae).
[0016] U.S. Pat. No. 4,636,217 OGILVIE--describing a vertebral
strut mechanism that can be implanted after at least one vertebrae
has been removed and which device consists of a mechanism for
causing the engagement of screws into the vertebrae above and the
vertebrae below the one removed.
[0017] In summary then, this group of devices differs from the
present invention in that they are vertebral replacements struts,
do not intrinsically participate in the bony fusion, can only be
inserted in the limited circumstances where an entire vertebrae has
been removed from the anterior approach, and are not designed for,
or intended to be used for the treatment of disc disease.
[0018] A third area of prior art related to the present invention
includes all devices designed to be applied to one of the surfaces
of the spine. Such devices include all types of plates, struts, and
rods which are attached by hooks, wires and screws. These devices
differ significantly from the present invention in that they are
not inserted within the disc space, and furthermore do not
intrinsically participate in supplying osteogenic material for the
fusion.
[0019] Therefore, with these devices where permanent spinal
immobilization is desired an additional surgery consisting of a
spinal fusion performed by conventional means or the use of
supplemental methylmethacrylate cement is required. Such devices
applied to the spine, but not within the disc space, would include
the following:
[0020] U.S. Pat. No. 4,604,995--STEPHENS--describing a "U" shaped
metal rod attached to the posterior elements of the spine with
wires to stabilize the spine over a large number of segments.
[0021] U.S. Pat. No. 2,677,369--KNOWLES--describing a metal column
device to be placed posteriorly along the lumbar spine to be held
in position by its shape alone and to block pressure across the
posterior portions of the spinal column by locking the spine in
full flexion thereby shifting the maximum weight back onto the
patient's own disc.
[0022] Other devices are simply variations on the use of rods (e.g.
Harrington Luque, Cotrel-Dubosset, Zielke), wires or cables
(Dwyer), plates and screws (Steffee), or struts (Dunn,
Knowles).
[0023] In summary, none of these devices are designed or can be
used within the disc space, do not replace a damaged disc, and do
not intrinsically participate in the generation of a bony
fusion.
[0024] Another area of related prior art to be considered is that
of devices designed to be placed within the vertebral interspace
following the removal of a damaged disc, and seeking to eliminate
further motion at that location.
[0025] Such a device is contained in U.S. Pat. No. 4,501,269
BAGBY--describing an implantable device and limited
instrumentation. The method employed is as follows: a hole is bored
transversely across the joint and then a hollow metal basket of
larger diameter than the hole is then pounded into the hole and
then filled with the bone debris generated by the drilling.
[0026] While the present invention (device, instrumentation, and
method) may appear to bear some superficial resemblance to the
BAGBY invention, it is minimal, while the differences are many fold
and highly significant. These differences include the
following:
[0027] 1. Safety--The present invention provides for a system of
completely guarded instrumentation so that all contiguous vital
structures (e.g. large blood vessels, neural structures) are
absolutely protected. Said instrumentation also makes
overpenetration by the drill impossible. Such overpenetration in
the cervical spine, for example, would result in the total
paralysis or death of the patient. In the thoracic spine, the
result would be complete paraplegia. In the lumbar spine, the
result would be paraplegia or a life-threatening perforation of the
aorta, vena cava, or iliac vessels. The present invention is
atraumatically screwed into place while the BAGBY device, in
contradistinction, is pounded into position. BAGBY describes that
the implant is significantly larger in size than the hole drilled
and must be pounded in. This is extremely dangerous and the
pounding occurs directly over the spinal cord which is precariously
vulnerable to percussive injury. Furthermore, while it is possible,
for example in the lumbar spine, to insert the present invention
away from the spinal cord and nerves, the BAGBY device must always
be pounded directly towards the spinal cord.
[0028] Furthermore, since the BAGBY device is pounded into a smooth
hole under great resistance, and lacking any specific design
features to secure it, the device is highly susceptible to forceful
ejection which would result in great danger to the patient and a
clinical failure. The present invention, in contradistinction, is
securely screwed into place, and possesses highly specialized
locking threads to make accidental dislodgement impossible. Because
of the proximity of the spinal cord, spinal nerves, and blood
vessels, any implant dislodgement as might occur with the BAGBY
device might have catastrophic consequences.
[0029] 2. Broad applicability--The BAGBY device can only be
inserted from the front of the vertebral column, however, the
present invention can be utilized in the cervical, thoracic, and
lumbar spine, and can be inserted from behind (posteriorly) in the
lumbar spine. This is of great importance in that the purpose of
these devices is in the treatment of disc disease and probably
greater than 99 percent of all lumbar operations for the treatment
of disc disease are performed from behind where the present
invention can easily be utilized, but the BAGBY device, as per his
description, cannot.
[0030] 3. Disc removal--The BAGBY invention requires the complete
removal of the disc prior to the drilling step, whereas the present
invention eliminates the laborious separate process of disc removal
and efficiently removes the disc and prepares the vertebral end
plates in a single step.
[0031] 4. Time required--The present invention saves time over the
BAGBY invention in that time is not wasted laboring to remove the
disc prior to initiating the fusion. Also, since with the present
invention the procedure is performed through a system of guarded
instrumentation, time is not wasted constantly placing and
replacing various soft tissue retractors throughout the
procedure.
[0032] 5. Implant stability--Dislodgement of the implant would be a
major source of device failure (an unsuccessful clinical result),
and might result in patient paralysis or even death. As discussed,
the BAGBY device lacks any specific means of achieving stability
and since it is pounded in against resistance to achieve vertebral
distraction, it is susceptible to forceful dislodgement by the
tendency of the two distracted vertebrae, to return to their
original positions squeezing out the device. The present invention
however is screwed into place. As there is no unscrewing force
present between the vertebrae and compression alone cannot dislodge
the implant, the implant is inherently stable by its design.
Furthermore, the threads of the present invention are highly
specialized in that they are periodically interrupted such that the
tail ends of each of the tabs so formed are blunted and twisted so
as to resist accidental unscrewing. The removal of an implant with
such "locking threads" requires the use of a special extractor
included within the instrumentation. The stability of the present
invention is still further enhanced, again in contradistinction to
the BAGBY device, by the presence of a "bone ingrowth" surface
texturing, which both increases the friction of the fit and allows
for the direct growth of the vertebral bone into the casing of the
implant itself.
[0033] 6. Spinal stability--The present invention is not only
self-stabilizing, it also provides stability to the adjacent
vertebrae in at least three ways that the BAGBY device cannot.
First, the BAGBY device is placed transversely across the joint in
the center, leaving both vertebrae free to rock back and forth over
this round barrel shaped axis, much like a board over a barrel,
being used for a seesaw.
[0034] Secondly, as the BAGBY device lacks any specific design
features to resist sliding, it may actually behave as a third body
allowing the translation of the vertebrae relative to the device
and to each other.
[0035] Thirdly, any device can only provide stability if it remains
properly seated. The present invention is inherently stable, and
therefore assures that it will stabilize the adjacent vertebrae;
rather than, as with the BAGBY device, where the instability of the
spine to be treated may instead cause a dislocation of the implant,
with further loss of spinal stability.
[0036] 7. The collapse of the interspace--While both the present
invention and the BAGBY device can be fabricated to withstand the
compression forces within the interspace, the interspace may
nevertheless collapse under the superincumbent body weight as the
implant settles into the vertebral bone. This is related to the
load of per unit area. Again the present invention is superior to
the BAGBY device in at least four ways. First, the present
invention offers considerably greater surface area to distribute
the load. Secondly, while the BAGBY device is placed centrally, the
present device is placed bilaterally where the bone tends to be
more cortical and much stronger out towards the rim. Thirdly, the
present invention supports the load achieving an "I" beam effect,
whereas the BAGBY implant does not. Fourthly, it is not pressure
alone that causes the collapse of the bone adjacent to the implant,
but also bony erosion that is caused by the motion under pressure
of the implant against the bone. As discussed in item #6 above, the
present invention alone is highly resistant to such motion, again
diminishing the likelihood of erosion and interspace collapse.
[0037] 8. Bone ingrowth surface texturing--The present invention
has a surface treatment of known and conventional technology to
induce the growth of bone from the vertebrae directly into the
casing material of the implant itself. The BAGBY device has no
similar feature.
[0038] 9. Fusion mass--The BAGBY invention calls for removing the
disc and then drilling a hole between the adjacent vertebrae. The
bony debris so generated is then put into the device. The present
invention takes a core of pure bone producing marrow from the iliac
crest, and then by use of a special press forcibly injects the
device with an extremely dense compressed core of that osteogenic
material until the material itself virtually extrudes from every
cell of the implant.
[0039] 10. The probability of achieving fusion--The fusion rate
within the spine is known to be related directly to the amount of
exposed vascular bone bed area, the quality and quantity of the
fusion mass available, and the extent of the stabilization obtained
with all other factors being half constant. It would then be
anticipated, that the fusion rate would be superior with the
present invention as compared to the BAGBY device, because of
optimal implant stability (#5), optimal spinal stability (#6), bone
ingrowth surface treatment (#8), superior fusion mass (#9), and the
greater exposed vertebral bony surface area (#7).
[0040] The last area of prior art possibly related to the present
invention and therefore, to be considered related to "BONY
INGROWTH", and patents either describe methods of producing
materials and or materials or devices to achieve the same. Such
patents would include:
[0041] U.S. Pat. No. 4,636,526 (DORMAN), No. 4,634,720 (DORMAN),
No. 4,542,539 (ROWE), No. 4,405,319 (COSENTINO), No. 4,439,152
(SMALL), No. 4,168,326 (BROEMER), No. 4,535,485 (ASHMAN), No.
3,987,499 (SCHARBACH), No. 3,605,123 (HAHN), No. 4,655,777 (DUNN),
No. 4,645,503 (LIN), No. 4,547,390 (ASHMAN), No. 4,608,052 (VAN
KAMPEN), No. 4,698,375 (DORMAN), No. 4,661,536 (DORMAN), No.
3,952,334 (BOKROS), No. 3,905,047 (LONG), No. 4,693,721 (DUCHEYNE),
No. 4,070,514 (ENTHERLY).
[0042] However, while the present invention would utilize bone
ingrowth technology, it would do so with conventional
technology.
[0043] In summary then, the present invention, instrumentation, and
method, alone provides for a one stage discectomy, fusion, and
interbody internal spinal fixation; that being performed more
quickly, with greater safety, and more affectively, for all of the
aforementioned reasons than is possible with any other known
art.
BRIEF SUMMARY OF THE INVENTION
[0044] The present invention comprises a series of artificial
implants, the purpose of which is to participate in, and directly
cause bone fusion across an intervertebral space following the
excision of a damaged disc. Such implants are structurally load
bearing devices, stronger than bone, capable of withstanding the
substantial forces generated within the spinal interspace. Such
device have a plurality of macro sized cells and openings, which
can be loaded with fusion promoting materials, such as autogenous
bone, for the purpose of materially influencing the adjacent
vertebrae to perform a bony bond to the implants and to each other.
The implant casing may be surface textured or otherwise treated by
any of a number of known technologies to achieve a "bone ingrowth
surface" to further enhance the stability of the implant and to
expedite the fusion.
[0045] Further, said devices are so configured and designed so as
to promote their own stability within the vertebral interspace and
to resist being dislodged, and furthermore, to stabilize the
adjacent spinal segments.
[0046] The apparatus for preparing the vertebrae for insertion of
the implant is also disclosed, such instrumentation and method
allowing for the rapid and safe removal of the disc, preparation of
the vertebrae, performance of the fusion, and internal
stabilization of the spinal segment.
DISCUSSION OF THE INSTRUMENTATION
[0047] The concept of performing various aspects of this surgery
are not entirely new. Drills are frequently placed through hollow,
tubular guards to protect the adjacent soft tissues. A set of
instruments developed by Ralph Cloward utilizes such a tubular
drill guard on a larger scale, for the purpose of drilling into the
cervical spine. However, this inventor is unaware of any set of
instruments, system, or procedure designed to allow the entire
surgical procedure beyond the initial exposure, to be performed
blindly and with complete safety through a fixed sheath apparatus.
Specific design features which combine to make this uniquely
possible are as follows:
[0048] 1. The availability of the specific implant.
[0049] 2. The end of all the penetrating instrumentation is blunt
faced.
[0050] 3. All of the instruments have been stopped out at a
predetermined depth to avoid overpenetration.
[0051] 4. The design of the external sheath conforms to the spacial
limitations of the specific surgical site.
[0052] 5. The design and use of a second or inner sheath allows for
the difference in size between the inside diameter of the outer
sheath, and the outside diameter of the drill itself. This
difference being necessary to accommodate the sum of the
distraction to be produced, and the depth of the circumferential
threading present of the implant.
[0053] 6. A specially designed drill bit with a central shaft
recess allows for the safe collection of the drilling products,
which can then be removed without disturbing the outer sheath by
removing the drill bit and inner sheath as a single unit.
[0054] 7. A specially designed trephine for removing a core of bone
slightly smaller in diameter than the internal diameter of the
implant cavity itself, however of a greater length.
[0055] 8. A specially designed press for forcefully compressing and
injecting the long core of autogenous bone into the implant, such
that it extrudes through the implant itself.
[0056] 9. A specially designed driver extractor, which attaches to
the implant and allows the implant to be either inserted or removed
without itself dissociating from the implant, except by the
deliberate disengagement of the operator.
OBJECTS OF THE PRESENT INVENTION
[0057] It is an object of the present invention to provide an
improved method of performing a discectomy, a fusion, and an
internal stabilization of the spine, and specifically, all three of
the above simultaneously and as a single procedure.
[0058] It is another object of the present invention to provide an
improved method of performing a discectomy, a fusion, and an
internal stabilization of the spine, which is both quicker and
safer than is possible by previous methods.
[0059] It is another object of the present invention to provide an
improved method of performing a discectomy, a fusion, and an
internal stabilization of the spine, to provide for improved
surgical spinal implants.
[0060] It is another object of the present invention to provide an
improved method of performing a discectomy, a fusion, and an
internal stabilization of the spine, which provides for an improved
system of surgical instrumentation to facilitate the performance of
the combined discectomy, fusion, and internal spinal
stabilization.
[0061] It is another object of the present invention to provide an
improved method of performing a discectomy, a fusion, and an
internal stabilization of the spine procedures.
[0062] These and other objects of the present invention will be
apparent from review of the following specifications and the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0063] FIG. 1 is a partial view of the vertebrae structure with the
driver and outer sheath assembly of the present invention.
[0064] FIG. 1A is a perspective view of the driver member for the
outer sheath.
[0065] FIG. 2 is a perspective view of the outer sheath being
inserted into the vertebrae structure.
[0066] FIG. 3 is a perspective view of the outer sheath and inner
sheath assembly, with the drill bit of the present invention.
[0067] FIG. 3A is a side sectional view of the collar and drill bit
of FIG. 3.
[0068] FIG. 4 is a perspective view of a cylindrical implant and
vertebrae structure.
[0069] FIG. 4A is a perspective view of one preferred embodiment of
the implant.
[0070] FIG. 4B is a cross sectional view of the implant of FIG.
4A.
[0071] FIG. 4C is the driving and insertion equipment for the
implant of FIG. 4A.
[0072] FIG. 4d is a side sectional view of the driver and implant
between vertebrae.
[0073] FIG. 5 is a sectional view of the vertebrae structure, taken
along lines 5-5 of FIG. 4.
DETAILED DESCRIPTION OF THE DRAWINGS
[0074] Referring to FIG. 1 a vertebrae structure comprising two
vertebrae V and a disc D between the two vertebrae, is shown. A
hollow tubular drill sleeve 10 has teeth 12 at its lower end. The
sleeve 10 has an enlarged diameter upper portion 14.
[0075] A driver 16, shown in FIG. 1A, consists of a solid tubular
member 18 and an increased diameter head 20. The external diameter
of the solid tubular member 18 is slightly smaller than the inside
diameter of the hollow tubular drill sleeve 10 and has a length
that is substantially shorter than the overall length of the hollow
tubular drill sleeve 10.
[0076] The drill sleeve 10 is made of metal in order to be driven
into the vertebrae V and be held in place by the teeth 12 of the
drill sleeve 10.
[0077] Referring to FIG. 2 the drill sleeve 10 with the driver 16
installed is shown being driven into two vertebrae V on either side
of a disc D by hammer H.
[0078] Referring to FIGS. 3 and 3a the drill assembly is shown. In
FIG. 3 the drill sleeve 10 is illustrated in the two vertebrae V,
straddelling the disc D.
[0079] The retaining sleeve 15 has an outside diameter slightly
smaller than the inside diameter of the drill sleeve 10, and a
length substantially the same length as the drill sleeve 10. The
retaining sleeve 15 has a collar 17 at its upper end for engaging
the top of the drill sleeve 10.
[0080] The drill 22 comprises an upper portion 24, a central
recessed portion 26 and a lower cutting drill portion 28. The upper
24 and lower portion 28 of the drill 22 have the same outside
diameter. The drill 24 has a collar 30 attached to the upper
portion 24 of the drill 22.
[0081] The outside diameter of the drill 22 is slightly smaller
than the inside diameter of the retaining sleeve 15. The length of
the drill, from the collar 30 to the end of the drill bit, is such
that a predetermined portion of the drill bit 22 extends beyond the
end 29 of the sleeve when fully inserted.
[0082] Referring to FIG. 4, a cylindrical embodiment of the present
invention is shown, one implant positioned in the opening in the
vertebrae and disc formed by the drill 22, and a second implant
shown prior to implantation.
[0083] The cylindrical implant 50 comprises a hollow tubular member
which in the preferred embodiment is made of an ASTM surgically
implantable material, and preferably Titanium. The cylindrical
implant 50 is closed at one end 52 and open at the other end 54.
The outer cylindrical implant 50 has a series of macro-sized
openings 56 through the side walls of the cylindrical member 50. A
series of external threads 53 are formed on the circumference of
the cylindrical implant 50. The threads 53 are locking threads
having a series of interjections, the ends of which are blunted and
twisted so as to resist unscrewing.
[0084] The open end 54 of the cylindrical implant 50 has an
internal thread 51 for receiving a complementary cap 52 which has
an external thread 58 for engaging the internal threads 51 of the
cylindrical member 50. The cap 52 has a hexagonal opening 59 for
use with an allen wrench for tightening the cap. A driver engaging
element 70 is located on the rear surface 60 of the implant. The
driver engaging element 70 comprises a raised rectangular portion
63 and a central threaded opening 65, for engaging the driver
apparatus, shown in FIG. 4c and FIG. 4d. The driving equipment 100
comprises a central tubular rod 102 having a thread fitting into
opening 65 in the implant. An enlarged knurled knob 106 is affixed
to the other end of the rod 102 for ease in turning. The central
rod 102 is enclosed within a hollow tubular member 108, having a
narrow lower portion 110 and an increased diameter upper portion
112. At the end of the lower portion 110 is a attachment member
114, having a generally rectangular depression 116 for
complementing the driver engaging element 70 of the implant 50. A
pair of handles 118 and 120 extend perpendicular from the upper
position 112 of the tubular member 108 to assist in turning the
driver 100.
[0085] The operation is performed in the following manner: (Example
Lumbar Spine Posterior Approach) A skin incision is made directly
over the interspace to be operated on. The dissection is carried
down along side of the superspinous and intraspinous ligaments
preserving those structures. A semi hemi laminotomy is performed at
the upper level, removing sufficient bone to allow access into the
interspace. The ligament flavum is removed and then the dural sac
is protected by retracting it medially along with the traversing
(inferior) nerve root. The superior nerve root or the root exiting
beneath the pedicle at level above is visualized and protected.
[0086] At this time the drill sleeve 10 is placed into the spinal
canal with both nerve roots directly inspected and protected. The
drill sleeve 10 is imbedded by teeth 12 spanning the disc space
from the midline over and it is seated into the two vertebrae V
across the disc D space by using a driver 20. Once this is done,
the driver 20 is removed and a retaining sleeve 15 is placed
through the drill sleeve 10. Once sealed, sleeve 10 provides
absolute protection to the dural sac and nerve roots as the
remaining surgery is performed entirely through this sleeve.
[0087] The inner sleeve allows for the difference between the
outside diameter of the drill 22 and the outside diameter of the
threads 53 of the cylindrical implant 50. This then makes it
possible to perform the entire operation through the Lumbar of the
imbedded outer sleeve despite the differences in diameter between
the drill and the implant.
[0088] A drill 22 is then placed in the retaining sleeve 17. The
drill 22 is of such a length that it can not penetrate more then 28
millimeters beyond the end of the drill sleeve 10. This, of course,
could be varied and made smaller for enhanced safety. However at
the present time 27 to 28 millimeters seems to be safe for probably
3 standard deviations of the population. The drill 22 is attached
to a power unit and the drilling takes place.
[0089] The recessed central area between the reduced portion 26,
allows for the accumulation of the debris generated by the
drilling. At this time, leaving the outer sleeve firmly embedded,
the retaining sleeve 17 is removed with the drill 22 as a single
unit. All the vertebrae and disc debris that was generated during
the drilling is contained within the recess and against the inside
wall of the retaining sleeve 17 and can not come out within the
spinal canal. Once the retaining sleeve 17 and drill 22 is out of
the patient's operative field, all of the material so generated can
be removed.
[0090] The next step is that a screw tap is put down through the
drill sleeve 10. The tap also has a collar on it that will
automatically stop the tap from extending beyond 28 millimeters of
penetration. The tap itself has a blunt nose that would also avoid
any perforation. The tap is then removed. The tap size has
deliberately been selected so that it's inner root diameter is 1.3
millimeters greater than the outside diameter of the drill 22. This
insures that the interspace will be distracted by at least that
much once the implant is placed. The tap has its outside diameter
1.2 millimeters greater than its root diameter. The tap is removed
and the space is now prepared to accept the cylindrical implant
50.
[0091] The Implant 50 is prepared by utilizing the trephine, a
hollow drill, to obtain a core of pure cancellous bone from the
patients iliac crest of slightly smaller diameter than the internal
diameter of the implant but approximately 6 mm longer. The implant
50 is placed in a press like device like an ammo loader and the
bone graft measuring approximately 32 millimeters is then
compressed into the hollow body of the implant (26 mm) so that the
bone graft fills the opening 54 and extends through the openings
56. The cap 60 is then screwed on to the implant 50 by use of an
alien driver/wrench and the device is ready for implantation.
[0092] The inserter/remover is such that it lock onto the implant,
so that the implant can be moved either clockwise or
counter-clockwise, screwed or unscrewed. The implant itself has for
its root diameter the same exact root diameter as the tap which as
already noted is already 1.3 millimeters greater than the drill and
has an outside diameter, 1.5 millimeters greater than its root.
This is also 0.3 millimeters greater than the threads cut by the
tap so that in inserting the device it is actually cutting through
previously uncut bone helping to insure that it locks in firmly.
The threads on the implant 50 are locking threads so that it is
easier to screw the device in than for it to be unscrewed. However,
with sufficient torque it is possible to extract the device if ones
so desires.
[0093] Once the implant has been seated it is able to be inserted
only 28 millimeters. Since the implant 50 is only 26 millimeters in
length, this virtually guarantees that the implant 50 will be
recessed into the vertebral bodies more than 2 millimeters and can
not protrude into the spinal canal.
[0094] Similarly, the implants shown in FIG. 4b can be implanted.
The implant in FIG. 4b is a modified solid, having extensive
channelling throughout, and has no cap. A central opening 61
permits insertion of the bone graft material into the interior of
the implant.
[0095] These implants have a surface configuration such as to
induce bone ingrowth through the implant, and into the wall of the
vertebrae in effect inducing fusion from one vertebrae in joint to
the other, thereby eventually making the implant itself superfluous
as the bone would do the work.
[0096] The implant itself, because of its being made of stronger
material than bone, would provide structural support to the two
vertebrae while awaiting bone ingrowth. Once the bone ingrowth
occurred, however, the implant would be firmly and permanently
fixed in place.
[0097] As shown in FIG. 4, more than one implant is inserted into
the disc space, thereby preventing the rocking motion that would
result in the difficulties referred to above in the discussion of
the Bagby patent.
[0098] While the invention has been described with regards to the
preferred embodiment, it is recognized that alternative embodiment
may be devised which would not depart from the present
invention.
* * * * *