U.S. patent application number 14/580326 was filed with the patent office on 2015-04-23 for spinal implant and integration plate for optimizing vertebral endplate contact load-bearing edges.
The applicant listed for this patent is Titan Spine, LLC. Invention is credited to Chad J. Patterson, Peter F. Ullrich, JR..
Application Number | 20150112439 14/580326 |
Document ID | / |
Family ID | 47219752 |
Filed Date | 2015-04-23 |
United States Patent
Application |
20150112439 |
Kind Code |
A1 |
Ullrich, JR.; Peter F. ; et
al. |
April 23, 2015 |
SPINAL IMPLANT AND INTEGRATION PLATE FOR OPTIMIZING VERTEBRAL
ENDPLATE CONTACT LOAD-BEARING EDGES
Abstract
An interbody spinal implant including a body and an integration
plate having a top surface, a bottom surface, opposing lateral
sides, opposing anterior and posterior portions, and a
substantially hollow center in communication with a vertical
aperture. The body is recessed in a way that portions of the
integration plate protrude above the top and/or bottom surface of
the body to enhance the resistance of the implant to expulsion from
the intervertebral space.
Inventors: |
Ullrich, JR.; Peter F.;
(Neenah, WI) ; Patterson; Chad J.; (Port
Washington, WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Titan Spine, LLC |
Mequon |
WI |
US |
|
|
Family ID: |
47219752 |
Appl. No.: |
14/580326 |
Filed: |
December 23, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14057035 |
Oct 18, 2013 |
8940053 |
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14580326 |
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13571693 |
Aug 10, 2012 |
8562685 |
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14057035 |
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12151198 |
May 5, 2008 |
8262737 |
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13571693 |
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11123359 |
May 6, 2005 |
7662186 |
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12151198 |
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Current U.S.
Class: |
623/17.16 |
Current CPC
Class: |
A61F 2002/30906
20130101; A61F 2/4465 20130101; A61F 2310/00179 20130101; A61F
2002/30148 20130101; A61F 2002/30273 20130101; A61F 2002/30113
20130101; A61F 2/442 20130101; A61F 2002/30785 20130101; A61F
2002/448 20130101; A61F 2310/00023 20130101; A61F 2002/3013
20130101; A61F 2002/30156 20130101; A61F 2002/2835 20130101; A61F
2002/30187 20130101; A61F 2002/30014 20130101; A61F 2002/30405
20130101; A61F 2002/30973 20130101; A61F 2002/30171 20130101; A61F
2002/30774 20130101; A61F 2002/30836 20130101; A61F 2002/4629
20130101; A61F 2002/30593 20130101; A61F 2002/30214 20130101; A61F
2002/30176 20130101; A61F 2002/30125 20130101; A61F 2002/30266
20130101; A61F 2002/30772 20130101; A61F 2002/30133 20130101; A61F
2002/2817 20130101; A61F 2002/30604 20130101; A61F 2310/00017
20130101; A61F 2/30965 20130101; A61F 2002/30892 20130101; A61F
2/447 20130101; A61F 2002/30153 20130101; A61F 2002/30217 20130101;
A61F 2002/30925 20130101 |
Class at
Publication: |
623/17.16 |
International
Class: |
A61F 2/44 20060101
A61F002/44 |
Claims
1. An interbody spinal implant, comprising: a body that is
generally oval-shaped in transverse cross section, and comprises a
top surface, a bottom surface, a posterior portion, an anterior
portion comprising a solid rear wall extending substantially the
entire width and height of the body, a substantially hollow center,
and a single vertical aperture extending from the top surface to
the bottom surface, and having varying width and maximum width at
its center, wherein a portion of the top surface of the body, and
optionally the bottom surface of the body, is recessed and
comprises a plurality of vertical holes along the periphery of the
vertical aperture, and the non-recessed portion of the top surface
and, if the bottom surface is recessed, the non-recessed portion of
the bottom surface comprises a blunt and radiused portion; and a
first integration plate, and optionally a second integration plate,
comprising a top surface having a roughened surface topography
adapted to grip bone and inhibit migration of the implant, a bottom
surface having a plurality of vertical posts, opposing lateral
sides, opposing anterior and posterior portions, and a single
vertical aperture extending from the top surface to the bottom
surface of the integration plate, aligning with the single vertical
aperture of the body, and defining a transverse rim; wherein the
entire bottom surface of the first integration plate is inserted
into the recessed portion of the top surface of the body and the
plurality of posts are inserted into the plurality of holes,
thereby affixing the first integration plate to the body, and if a
second integration plate is present, the entire bottom surface of
the second integration plate is inserted into the recessed portion
of the bottom surface of the body and the plurality of posts are
inserted into the plurality of holes, thereby affixing the second
integration plate to the body.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of U.S. patent application Ser. No.
14/057,035 filed Oct. 18, 2013, which is a continuation of U.S.
patent application Ser. No. 13/571,693, filed Aug. 10, 2012, which
issued as U.S. Pat. No. 8,562,685 on Oct. 22, 2013, which is a
continuation-in-part of U.S. patent application Ser. No.
12/151,198, filed on May 5, 2008, which issued as U.S. Pat. No.
8,262,737 on Sep. 11, 2012, which is a continuation-in-part of U.S.
patent application Ser. No. 11/123,359, filed on May 6, 2005, which
issued as U.S. Pat. No. 7,662,186 on Feb. 16, 2010. The contents of
all prior applications are incorporated by reference in this
document, in their entirety and for all purposes.
FIELD OF THE INVENTION
[0002] The invention relates generally to interbody spinal implants
and methods of using such implants and, more particularly, to an
implant including a protruding edge on one or more of its anterior,
posterior or lateral portions to both bear some load force (e.g.,
keep some of the spinal load forces off of the body of the implant)
and enhance resistance to expulsion. The anti-expulsion edge may be
comprised on the top surface of one or more integration plates
affixed to the implant body.
BACKGROUND OF THE INVENTION
[0003] In the simplest terms, the spine is a column made of
vertebrae and discs. The vertebrae provide the support and
structure of the spine while the spinal discs, located between the
vertebrae, act as cushions or "shock absorbers." These discs also
contribute to the flexibility and motion of the spinal column. Over
time, the discs may become diseased or infected, may develop
deformities such as tears or cracks, or may simply lose structural
integrity (e.g., the discs may bulge or flatten). Impaired discs
can affect the anatomical functions of the vertebrae, due to the
resultant lack of proper biomechanical support, and are often
associated with chronic back pain.
[0004] Several surgical techniques have been developed to address
spinal defects, such as disc degeneration and deformity. Spinal
fusion has become a recognized surgical procedure for mitigating
back pain by restoring biomechanical and anatomical integrity to
the spine. Spinal fusion techniques involve the removal, or partial
removal, of at least one intervertebral disc and preparation of the
disc space for receiving an implant by shaping the exposed
vertebral endplates. An implant is then inserted between the
opposing endplates.
[0005] Several interbody implant systems have been introduced to
facilitate interbody fusion. Traditional threaded implants involve
at least two cylindrical bodies, each typically packed with bone
graft material, surgically placed on opposite sides of the
mid-sagittal plane through pre-tapped holes within the
intervertebral disc space. This location is not the preferable
seating position for an implant system, however, because only a
relatively small portion of the vertebral endplate is contacted by
these cylindrical implants. Accordingly, these implant bodies will
likely contact the softer cancellous bone rather than the stronger
cortical bone, or apophyseal rim, of the vertebral endplate. The
seating of these threaded cylindrical implants may also compromise
biomechanical integrity by reducing the area in which to distribute
mechanical forces, thus increasing the apparent stress experienced
by both the implant and vertebrae. Still further, a substantial
risk of implant subsidence (defined as sinking or settling) into
the softer cancellous bone of the vertebral body may arise from
such improper seating.
[0006] In contrast, open ring-shaped cage implant systems are
generally shaped to mimic the anatomical contour of the vertebral
body. Traditional ring-shaped cages are generally comprised of
allograft bone material, however, harvested from the human femur.
Such allograft bone material restricts the usable size and shape of
the resultant implant. For example, many of these femoral
ring-shaped cages generally have a medial-lateral width of less
than 25 mm. Therefore, these cages may not be of a sufficient size
to contact the strong cortical bone, or apophyseal rim, of the
vertebral endplate. These size-limited implant systems may also
poorly accommodate related instrumentation such as drivers,
reamers, distractors, and the like. For example, these implant
systems may lack sufficient structural integrity to withstand
repeated impact and may fracture during implantation. Still
further, other traditional non-allograft ring-shaped cage systems
may be size-limited due to varied and complex supplemental implant
instrumentation which may obstruct the disc space while requiring
greater exposure of the operating space. These supplemental implant
instrumentation systems also generally increase the instrument load
upon the surgeon.
[0007] The surgical procedure corresponding to an implant system
should preserve as much vertebral endplate bone surface as possible
by minimizing the amount of bone removed. This vertebral endplate
bone surface, or subchondral bone, is generally much stronger than
the underlying cancellous bone. Preservation of the endplate bone
stock ensures biomechanical integrity of the endplates and
minimizes the risk of implant subsidence. Thus, proper interbody
implant design should provide for optimal seating of the implant
while utilizing the maximum amount of available supporting
vertebral bone stock.
[0008] Nevertheless, traditional implantation practices often do
not preserve critical bone structures such as vertebral endplates
during the surgical procedure. In some cases, the implant devices
themselves necessitate removal of bone and were not designed or
implanted with the intent to preserve critical bone structures
during or after implantation.
[0009] In summary, at least ten, separate challenges can be
identified as inherent in traditional anterior spinal fusion
devices. Such challenges include: (1) end-plate preparation; (2)
implant difficulty; (3) materials of construction; (4) implant
expulsion; (5) implant subsidence; (6) insufficient room for bone
graft; (7) stress shielding; (8) lack of implant incorporation with
vertebral bone; (9) limitations on radiographic visualization; and
(10) cost of manufacture and inventory.
SUMMARY OF THE INVENTION
[0010] The invention is directed to interbody spinal implants and
to methods of using such implants. The implants can be inserted,
using methods of the invention, from a variety of vantages,
including anterior, antero-lateral, and lateral implantation. The
spinal implant is preferably adapted to be inserted into a prepared
disc space via a procedure which does not destroy the vertebral
end-plates, or contacts the vertebral end-plates only peripherally,
allowing the intact vertebral end-plates to deflect like a
diaphragm under axial compressive loads generated due to
physiologic activities and pressurize the bone graft material
disposed inside the spinal implant.
[0011] An implant preferably comprises a body having a top surface,
a bottom surface, opposing lateral sides, opposing anterior and
posterior portions, a substantially hollow center, and a single
vertical aperture extending from the top surface to the bottom
surface. The vertical aperture comprises a shape, dimensions, and
position on the top surface and the bottom surface of the implant
body, and the shape, dimensions, and position define a transverse
rim on the top surface and on the bottom surface of the body. The
rim includes an anterior section, a posterior section, a first
lateral section, and a second lateral section. The shape,
dimensions, and position of the vertical aperture cause a
particular amount of the load force caused by movement or flexing
of a vertebrae to be distributed to one or more of the anterior
section, posterior section, first lateral section, or second
lateral section of the transverse rim. As well, the shape,
dimensions, and position of the vertical aperture cause a
particular amount of said load force to be distributed to a bone
graft material disposed in the substantially hollow center and in
the aperture. The apportionment of the load force distribution may
be controlled, at least in part, by the placement and orientation
of the implant in the intervertebral space. The distribution,
therefore, may be according to a desired amount.
[0012] In general, an implant comprises a body comprising a top
surface comprising an anterior section, a posterior section, and
opposing lateral sections, as well as a bottom surface comprising
an anterior section, a posterior section, and opposing lateral
sections. The body also comprises opposing lateral sides, opposing
anterior and posterior portions, a substantially hollow center, and
a single vertical aperture extending from the top surface to the
bottom surface.
[0013] The implant also preferably comprises at least one
integration plate. An integration plate may be affixed to the top
surface of the body, the bottom surface of the body, or both the
top surface and the bottom surface of the body. The integration
plate comprises a top surface comprising an anterior section, a
posterior section, opposing lateral sections, and a roughened
surface topography adapted to grip bone and inhibit migration of
the implant, as well as a bottom surface comprising an anterior
section, a posterior section, and opposing lateral sections. The
integration plate also comprises opposing lateral sides, opposing
anterior and posterior portions, and a single vertical aperture
extending from the top surface to the bottom surface of the first
integration plate and aligning with the single vertical aperture of
the body.
[0014] In some aspects, at least a portion of the anterior section
of the top surface of the body is recessed to a first depth, and at
least a portion of the posterior section of the top surface of the
body is recessed to a second depth that is less than the first
depth. The anterior section of the bottom surface of the
integration plate is inserted into the recessed portion of the
anterior section of the top surface of the body and the posterior
section of the bottom surface of the integration plate is inserted
into the recessed portion of the posterior section of the top
surface of the body. Thus, the anterior section of the bottom
surface of the integration plate aligns with the anterior section
of the top surface of the body to facilitate the connection between
the body and the integration plate. As a result of the different
recessed depths, when the integration plate is joined with the
body, the posterior section of the top surface of the integration
plate protrudes above the horizontal plane of the top surface of
the body. In aspects where the implant includes an integration
plate on the bottom surface of the body (in addition to or in lieu
of an integration plate on the top surface of the body), the bottom
surface of the implant would be have the same recessed
configuration, appropriate for the orientation of the bottom. In
this case, however, the posterior section of the top surface of the
integration plate on the bottom of the body will protrude below
(e.g., downward) the horizontal plane of the bottom surface of the
body.
[0015] In some aspects, at least a portion of the posterior section
of the top surface of the body is recessed to a first depth, and at
least a portion of the anterior section of the top surface of the
body is recessed to a second depth that is less than the first
depth. The posterior section of the bottom surface of the
integration plate is inserted into the recessed portion of the
posterior section of the top surface of the body and the anterior
section of the bottom surface of the integration plate is inserted
into the recessed portion of the anterior section of the top
surface of the body. Thus, the posterior section of the bottom
surface of the integration plate aligns with the posterior section
of the top surface of the body to facilitate the connection between
the body and the integration plate. As a result of the different
recessed depths, when the integration plate is joined with the
body, the anterior section of the top surface of the integration
plate protrudes above the horizontal plane of the top surface of
the body. In aspects where the implant includes an integration
plate on the bottom surface of the body (in addition to or in lieu
of an integration plate on the top surface of the body), the bottom
surface of the implant would be have the same recessed
configuration, appropriate for the orientation of the bottom. In
this case, however, the anterior section of the top surface of the
integration plate on the bottom of the body will protrude below
(e.g., downward) the horizontal plane of the bottom surface of the
body.
[0016] In some aspects, at least a portion of one of the lateral
sections of the top surface of the body is recessed to a first
depth, and at least a portion of the opposing lateral section of
the top surface of the body is recessed to a second depth that is
greater than the first depth. One of the lateral sections of the
bottom surface of the integration plate is inserted into the
lateral section of the top surface of the body recessed to the
first depth, and the opposing lateral section of the bottom surface
of the integration plate is inserted into the lateral section of
the top surface of the body recessed to the second depth. Thus, the
lateral sections of the bottom surface of the integration plate
align with the lateral sections of the top surface of the body to
facilitate the connection between the body and the integration
plate. As a result of the different recessed depths, when the
integration plate is joined with the body, one of the lateral
sections of the top surface of the integration plate protrudes
above the horizontal plane of the top surface of the body, and in
particular, the protruding lateral section on the top surface is
the lateral section that is on the same side as (e.g., corresponds
to) the lateral section of the bottom surface of the integration
plate inserted into the lateral section of the top surface of the
body recessed to the first depth. In aspects where the implant
includes an integration plate on the bottom surface of the body (in
addition to or in lieu of an integration plate on the top surface
of the body), the bottom surface of the implant would be have the
same recessed configuration, appropriate for the orientation of the
bottom. In this case, however, the lateral section of the top
surface of the integration plate on the bottom of the body will
protrude below (e.g., downward) the horizontal plane of the bottom
surface of the body.
[0017] The implant may comprise a lordotic angle adapted to
facilitate alignment of the spine. At least one of the anterior,
posterior, or opposing lateral sections of the top surface of the
integration plate may comprise an anti-expulsion edge to resist
pullout of the implant from the spine of a patient into which the
implant has been implanted. The anti-expulsion edge may comprise a
blade.
[0018] The substantially hollow portion of the body and the
vertical aperture of the body and the vertical aperture of the
integration plate may contain a bone graft material adapted to
facilitate the formation of a solid fusion column within the spine.
The bone graft material may be cancellous autograft bone, allograft
bone, demineralized bone matrix (DBM), porous synthetic bone graft
substitute, bone morphogenic protein (BMP), or a combination
thereof. The body may comprise a wall closing at least one of the
opposing anterior and posterior portions of the body for containing
the bone graft material.
[0019] The implant body and/or the integration plate may be
fabricated from a metal. A preferred metal is titanium. The implant
body may be fabricated from a non-metallic material, non-limiting
examples of which include polyetherether-ketone, hedrocel,
ultra-high molecular weight polyethylene, and combinations thereof.
The implant body may be fabricated from both a metal and a
non-metallic material, including a composite thereof. For example,
a composite may be formed, in part, of titanium and, in part, of
polyetherether-ketone, hedrocel, ultra-high molecular weight
polyethylene, or combinations thereof.
[0020] It is to be understood that both the foregoing general
description and the following detailed description are exemplary,
but are not restrictive, of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The invention is best understood from the following detailed
description when read in connection with the accompanying drawing.
It is emphasized that, according to common practice, the various
features of the drawing are not to scale. On the contrary, the
dimensions of the various features are arbitrarily expanded or
reduced for clarity. Included in the drawing are the following
figures:
[0022] FIG. 1A shows a perspective view of an embodiment of the
interbody spinal implant having a generally oval shape and
roughened surface topography on the top surface;
[0023] FIG. 1B shows a top view of the first embodiment of the
interbody spinal implant illustrated in FIG. 1A;
[0024] FIG. 2 shows a perspective view from the front of another
embodiment of the interbody spinal implant according to the
invention;
[0025] FIG. 3 shows a perspective view from the rear of the
embodiment of the interbody spinal implant illustrated in FIG.
2;
[0026] FIG. 4 shows a perspective view from the front of yet
another embodiment of the interbody spinal implant according to the
invention;
[0027] FIG. 5 shows a perspective view from the rear of the
embodiment of the interbody spinal implant illustrated in FIG. 4
highlighting an alternative transverse aperture;
[0028] FIG. 6 shows a perspective view of another embodiment of the
interbody spinal implant having a generally oval shape and being
especially well adapted for use in a cervical spine surgical
procedure;
[0029] FIG. 7 shows a perspective view of an implant having a
generally box shape;
[0030] FIG. 8 shows an exploded view of a generally oval-shaped
implant with an integration plate;
[0031] FIG. 9 shows an exploded view of a curved implant with an
integration plate;
[0032] FIG. 10 shows an exploded view of a posterior implant with
an integration plate;
[0033] FIG. 11 shows an exploded view of a lateral lumbar implant
with an integration plate;
[0034] FIG. 12 shows an exploded view of a generally oval-shaped
anterior cervical implant with an integration plate;
[0035] FIG. 13A shows an oval-shaped implant with a protruding
anti-expulsion edge;
[0036] FIG. 13B shows a close-up view of the protruding
anti-expulsion edge of the implant illustrated in FIG. 13A;
[0037] FIG. 13C shows a rectangular-shaped implant with a
protruding anti-expulsion edge oriented toward the posterior
portion;
[0038] FIG. 13D shows a close-up view of the protruding
anti-expulsion edge of the implant illustrated in FIG. 183;
[0039] FIG. 13E shows a perspective view of a curved-shaped implant
with a protruding anti-expulsion edge oriented toward the posterior
portion;
[0040] FIG. 13F shows a close-up view of the protruding
anti-expulsion edge of the implant perspective illustrated in FIG.
13E;
[0041] FIG. 13G shows another perspective view of the implant
illustrated in FIG. 13E;
[0042] FIG. 13H shows a close-up view of the protruding
anti-expulsion edge of the implant illustrated in FIG. 13G;
[0043] FIG. 13I shows a perspective view of a rectangular-shaped
implant with a protruding anti-expulsion edge oriented toward one
of the lateral sides;
[0044] FIG. 13J shows another perspective view of the implant
illustrated in FIG. 13I;
[0045] FIG. 13K shows a close-up view of the protruding
anti-expulsion edge of the implant illustrated in FIG. 13L;
[0046] AG. 13L shows a perspective view of a cervical implant with
a protruding anti-expulsion edge;
[0047] AG. 13M shows a close-up view of the protruding
anti-expulsion edge of the implant illustrated in AG. 13L;
[0048] FIG. 13N shows an oval-shaped implant with an integration
plate substantially flush with the horizontal plane of the top
surface of the implant;
[0049] FIG. 14A shows an example of an integration plate lordotic
angle;
[0050] FIG. 14B shows an example of an anti-expulsion edge
angle.
[0051] FIG. 15A shows an oval-shaped implant positioned on the
vertebral endplate;
[0052] FIG. 15B shows an anterior spine perspective of an
oval-shaped implant positioned between an upper and lower
vertebrae;
[0053] FIG. 15C shows a laterally inserted implant positioned on
the vertebral endplate;
[0054] FIG. 15D shows an anterior spine perspective of a laterally
inserted implant positioned between an upper and lower
vertebrae;
[0055] FIG. 16A shows a perspective of two posterior inserted
implants positioned on the vertebral endplate;
[0056] AG. 16B shows a top perspective of two posterior inserted
implants positioned on the vertebral endplate;
[0057] FIG. 16C shows a perspective of a single posterior inserted
implant positioned at an oblique angle on the vertebral
endplate;
[0058] FIG. 16D shows a top perspective of a single posterior
inserted implant positioned at an oblique angle on the vertebral
endplate;
[0059] FIG. 16E shows a perspective of a transforaminal curved
implant positioned proximal to the anterior end of a vertebral
endplate;
[0060] FIG. 16F shows a top perspective of a transforaminal curved
implant positioned proximal to the anterior end of a vertebral
endplate;
[0061] FIG. 17A shows a top view of an embodiment of a vertical
aperture for an oval-shaped implant;
[0062] FIG. 17B shows a top view of another embodiment of a
vertical aperture for an oval-shaped implant;
[0063] FIG. 17C shows a top view of another embodiment of a
vertical aperture for an oval-shaped implant;
[0064] FIG. 17D shows a top view of another embodiment of a
vertical aperture for an oval-shaped implant;
[0065] FIG. 18A shows a top view of an embodiment of a vertical
aperture for a posterior implant;
[0066] FIG. 18B shows a top view of another embodiment of a
vertical aperture for a posterior implant;
[0067] FIG. 18C shows a top view of another embodiment of a
vertical aperture for a posterior implant;
[0068] FIG. 18D shows a top view of another embodiment of a
vertical aperture for a posterior implant;
[0069] FIG. 19A shows a top view of an embodiment of a vertical
aperture for a curved implant;
[0070] FIG. 19B shows a top view of another embodiment of a
vertical aperture for a curved implant;
[0071] FIG. 19C shows a top view of another embodiment of a
vertical aperture for a curved implant;
[0072] FIG. 19D shows a top view of another embodiment of a
vertical aperture for a curved implant;
[0073] FIG. 20A shows a top view of an embodiment of a vertical
aperture for a cervical implant;
[0074] FIG. 20B shows a top view of another embodiment of a
vertical aperture for a cervical implant;
[0075] FIG. 20C shows a top view of another embodiment of a
vertical aperture for a cervical implant;
[0076] FIG. 20D shows a top view of another embodiment of a
vertical aperture for a cervical implant;
[0077] FIG. 21A shows a top view of an embodiment of a vertical
aperture for a lateral implant;
[0078] FIG. 21B shows a top view of another embodiment of a
vertical aperture for a lateral implant;
[0079] FIG. 21C shows a top view of another embodiment of a
vertical aperture for a lateral implant; and
[0080] FIG. 21D shows a top view of another embodiment of a
vertical aperture for a lateral implant.
DETAILED DESCRIPTION OF THE INVENTION
[0081] Certain embodiments of the invention may be especially
suited for placement between adjacent human vertebral bodies. The
implants of the invention may be used in procedures such as
Anterior Lumbar Interbody Fusion (ALIF), Posterior Lumbar Interbody
Fusion (PLIF), Transforaminal Lumbar Interbody Fusion (TLIF), and
cervical fusion. Certain embodiments do not extend beyond the outer
dimensions of the vertebral bodies.
[0082] The ability to achieve spinal fusion is directly related to
the available vascular contact area over which fusion is desired,
the quality and quantity of the fusion mass, and the stability of
the interbody spinal implant. Interbody spinal implants, as now
taught, allow for improved seating over the apophyseal rim of the
vertebral body. Still further, interbody spinal implants, as now
taught, better utilize this vital surface area over which fusion
may occur and may better bear the considerable biomechanical loads
presented through the spinal column with minimal interference with
other anatomical or neurological spinal structures. Even further,
interbody spinal implants, according to certain aspects of the
invention, allow for improved visualization of implant seating and
fusion assessment. Interbody spinal implants, as now taught, may
also facilitate osteointegration with the surrounding living
bone.
[0083] Anterior interbody spinal implants in accordance with
certain aspects of the invention can be preferably made of a
durable material such as stainless steel, stainless steel alloy,
titanium, or titanium alloy, but can also be made of other durable
materials such as, but not limited to, polymeric, ceramic, and
composite materials. For example, certain embodiments of the
invention may be comprised of a biocompatible, polymeric matrix
reinforced with bioactive fillers, fibers, or both. Certain
embodiments of the invention may be comprised of urethane
dimethacrylate (DUDMA)/tri-ethylene glycol dimethacrylate (TEDGMA)
blended resin and a plurality of fillers and fibers including
bioactive fillers and E-glass fibers. Durable materials may also
consist of any number of pure metals, metal alloys, or both.
Titanium and its alloys are generally preferred for certain
embodiments of the invention due to their acceptable, and
desirable, strength and biocompatibility. In this manner, certain
embodiments of the present interbody spinal implant may have
improved structural integrity and may better resist fracture during
implantation by impact. Interbody spinal implants, as now taught,
may therefore be used as a distractor during implantation.
[0084] Referring now to the drawing, in which like reference
numbers refer to like elements throughout the various figures that
comprise the drawing, FIG. 1 shows a perspective view of a first
embodiment of the interbody spinal implant 1 especially well
adapted for use in an ALIF procedure.
[0085] The interbody spinal implant 1 includes a body having a top
surface 10, a bottom surface 20, opposing lateral sides 30, and
opposing anterior 40 and posterior 50 portions. One or both of the
top surface 10 and the bottom surface 20 has a roughened topography
80. The roughened topography 80, however, is distinct from the
teeth provided on the surfaces of some conventional devices.
[0086] In some aspects, the interbody spinal implant 1 is
substantially hollow and has a generally oval-shaped transverse
cross-sectional area with smooth, rounded, or both smooth and
rounded lateral sides 30 and posterior-lateral corners 52. A
substantially hollow implant 1 includes an implant 1 having at
least about 33% of the interior volume of the implant 1 vacant. The
implant 1 includes at least one vertical aperture 60 that extends
the entire height of the implant body.
[0087] It is generally believed that the surface of an implant
determines its ultimate ability to integrate into the surrounding
living bone. Without being limited to any particular theory or
mechanism of action, it is believed that the cumulative effects of
at least implant composition, implant surface energy, and implant
surface roughness play a major role in the biological response to,
and osteointegration of, an implant device. Thus, implant fixation
may depend, at least in part, on the attachment and proliferation
of osteoblasts and like-functioning cells upon the implant
surface.
[0088] It is believed that cells attach more readily to relatively
rough surfaces rather than smooth surfaces. In this manner, a
surface may be bioactive due to its ability to facilitate cellular
attachment and osteointegration. The surface roughened topography
80 may better promote the osteointegration of the implant 1. The
surface roughened topography 80 may also better grip the vertebral
endplate surfaces and inhibit implant migration of the implant 1
upon placement and seating in a patient.
[0089] Accordingly, the implant 1 further includes the roughened
topography 80 on at least a portion of its top 10 and bottom 20
surfaces for gripping adjacent bone and inhibiting migration of the
implant 1. FIG. 1 shows roughened topography 80 on an embodiment of
the implant 1.
[0090] The roughened topography 80 may be obtained through a
variety of techniques including, without limitation, chemical
etching, shot peening, plasma etching, laser etching, or abrasive
blasting (such as sand or grit blasting). In at least one
embodiment, the interbody spinal implant 1 may be comprised of
titanium, or a titanium alloy, having the surface roughened
topography 80. The surfaces of the implant 1 are preferably
bioactive.
[0091] In a preferred embodiment of the invention, the roughened
topography 80 is obtained via the repetitive masking and chemical
or electrochemical milling processes described in U.S. Pat. No.
5,258,098; No. 5,507,815; No. 5,922,029; and No. 6,193,762. Each of
these patents is incorporated in this document by reference. Where
the invention employs chemical etching, the surface is prepared
through an etching process which utilizes the random application of
a maskant and subsequent etching of the metallic substrate in areas
unprotected by the maskant. This etching process is repeated a
number of times as necessitated by the amount and nature of the
irregularities required for any particular application. Control of
the strength of the etchant material, the temperature at which the
etching process takes place, and the time allotted for the etching
process allow fine control over the resulting surface produced by
the process. The number of repetitions of the etching process can
also be used to control the surface features.
[0092] By way of example, an etchant mixture of nitric acid
(HNO.sub.3) and hydrofluoric (HF) acid may be repeatedly applied to
a titanium surface to produce an average etch depth of about 0.53
mm. Interbody spinal implants 1, in accordance with some preferred
embodiments of the invention, may be comprised of titanium, or a
titanium alloy, having an average surface roughness of about 100
.mu.m. Surface roughness may be measured using a laser profilometer
or other standard instrumentation.
[0093] In another example, chemical modification of the titanium
implant surfaces can be achieved using HF and a combination of
hydrochloric acid and sulfuric acid (HCl/H.sub.2SO.sub.4). In a
dual acid etching process, the first exposure is to HF and the
second is to HCl/H.sub.2SO.sub.4. Chemical acid etching alone of
the titanium implant surface has the potential to greatly enhance
osteointegration without adding particulate matter (e.g.,
hydroxyapatite) or embedding surface contaminants (e.g., grit
particles) and this surface can be bioactive, for example, by
inducing or supporting bone formation by cellular reactions.
[0094] The implant 1 may be shaped to reduce the risk of
subsidence, and improve stability, by maximizing contact with the
apophyseal rim of vertebral endplates. Embodiments may be provided
in a variety of anatomical footprints having a medial-lateral width
ranging from about 32 mm to about 44 mm. An interbody spinal
implant 1 generally does not require extensive supplemental or
obstructive implant instrumentation to maintain the prepared disc
space during implantation. Thus, the interbody spinal implant 1 and
associated implantation methods allow for larger-sized implants as
compared with other size-limited interbody spinal implants known in
the art. This advantage allows for greater medial-lateral width and
correspondingly greater contact with the apophyseal rim. The
implant 1 may also include an anti-expulsion edge 8 as described in
more detail below.
[0095] As illustrated in FIG. 1, the implant 1 has an opening 90 in
the anterior portion 40. In one embodiment the posterior portion 50
has a similarly shaped opening 90. In some aspects, only the
anterior portion 40 has the opening 90 while the posterior portion
50 has an alternative opening 92 (which may have a size and shape
different from the opening 90).
[0096] The opening 90 has a number of functions. One function is to
facilitate manipulation of the implant 1 by the caretaker. Thus,
the caretaker may insert a surgical tool into the opening 90 and,
through the engagement between the surgical tool and the opening
90, manipulate the implant 1. The opening 90 may be threaded to
enhance the engagement.
[0097] The implant 1 may further include at least one transverse
aperture 70 that extends the entire transverse length of the
implant body. The at least one transverse aperture 70 may provide
improved visibility of the implant 1 during surgical procedures to
ensure proper implant placement and seating, and may also improve
post-operative assessment of implant fusion. Still further, the
substantially hollow area defined by the implant 1 may be filled
with cancellous autograft bone, allograft bone, DBM, porous
synthetic bone graft substitute, BMP, or combinations of these
materials (collectively, bone graft materials), to facilitate the
formation of a solid fusion column within the spine of a
patient.
[0098] Certain embodiments of the invention are particularly suited
for use during interbody spinal implant procedures (or vertebral
body replacement procedures) and may act as a final distractor
during implantation, thus minimizing the instrument load upon the
surgeon. For example, in such a surgical procedure, the spine may
first be exposed via an anterior approach and the center of the
disc space identified. The disc space is then initially prepared
for implant insertion by removing vertebral cartilage. Soft tissue
and residual cartilage may then also be removed from the vertebral
endplates.
[0099] Vertebral distraction may be performed using trials of
various-sized embodiments of the interbody spinal implant 1. The
determinatively sized interbody implant 1 may then be inserted in
the prepared disc space for final placement. The distraction
procedure and final insertion may also be performed under
fluoroscopic guidance. The substantially hollow area within the
implant body may optionally be filled, at least partially, with
bone fusion-enabling materials such as, without limitation,
cancellous autograft bone, allograft bone, DBM, porous synthetic
bone graft substitute, BMP, or combinations of those materials.
Such bone fusion-enabling material may be delivered to the interior
of the interbody spinal implant 1 using a delivery device mated
with the opening 90 in the anterior portion 40 of the implant 1.
The interbody spinal implant 1 may be generally larger than those
currently known in the art, and therefore have a correspondingly
larger hollow area which may deliver larger volumes of
fusion-enabling bone graft material. The bone graft material may be
delivered such that it fills the full volume, or less than the full
volume, of the implant interior and surrounding disc space
appropriately.
[0100] As noted above, FIG. 1 shows a perspective view of one
embodiment of the invention, the interbody spinal implant 1, which
is especially well adapted for use in an ALIF procedure. Other
embodiments of the invention are better suited for PLIF, TLIF, or
cervical fusion procedures. Specifically, FIGS. 2 and 3 show
perspective views, from the front and rear, respectively, of an
embodiment of an interbody spinal implant 101 especially well
adapted for use in a PLIF procedure. The interbody spinal implant
101 includes a body having a top surface 110, a bottom surface 120,
opposing lateral sides 130, and opposing anterior 140 and posterior
150 portions. One or both of the top surface 110 and the bottom
surface 120 has a roughened topography 180 for gripping adjacent
bone and inhibiting migration of the implant 101.
[0101] Certain embodiments of the interbody spinal implant 101 are
substantially hollow and have a generally rectangular shape with
smooth, rounded, or both smooth and rounded lateral sides and
anterior-lateral corners. As best shown in FIG. 3, the anterior
portion 140 may have a tapered nose 142 to facilitate insertion of
the implant 101. To further facilitate insertion, the implant 101
has chamfers 106 at the corners of its posterior portion 150. The
chamfers 106 prevent the implant 101 from catching upon insertion,
risking potential damage such as severed nerves, while still
permitting the implant 101 to have an anti-expulsion edge 108.
[0102] The implant 101 includes at least one vertical aperture 160
that extends the entire height of the implant body. The vertical
aperture 160 further defines a transverse rim 200.
[0103] As illustrated in FIG. 2, the implant 101 has an opening 190
in the posterior portion 150. The opening 190 has a number of
functions. One function is to facilitate manipulation of the
implant 101 by the caretaker. Thus, the caretaker may insert a
surgical tool into the opening 190 and, through the engagement
between the surgical tool and the opening 190, manipulate the
implant 101. The opening 190 may be threaded to enhance the
engagement.
[0104] The implant 101 may also have an Implant Holding Feature
(IHF) 194 instead of or in addition to the opening 190. As
illustrated in FIG. 2, the IHF 194 is located proximate the opening
190 in the posterior portion 150. In this particular example, the
IHF 194 is a U-shaped notch. Like the opening 190, the IHF 194 has
a number of functions, one of which is to facilitate manipulation
of the implant 101 by the caretaker. Other functions of the opening
190 and the IHF 194 are to increase visibility of the implant 101
during surgical procedures and to enhance engagement between bone
graft material and adjacent bone.
[0105] The implant 101 may further include at least one transverse
aperture 170. Like the vertical aperture 160, the size and shape of
the transverse aperture 170 are carefully chosen (and
predetermined) to achieve a preferable design tradeoff for the
particular application envisioned for the implant 101.
Specifically, the transverse aperture 170 should have minimal
dimensions to maximize the strength and structural integrity of the
implant 101. On the other hand, the transverse aperture 70 should
have maximum dimensions to (a) improve the visibility of the
implant 101 during surgical procedures to ensure proper implant
placement and seating, and to improve post-operative assessment of
implant fusion, and (b) to facilitate engagement between bone graft
material and adjacent bone. The substantially hollow area defined
by the implant 101 may be filled with bone graft materials to
facilitate the formation of a solid fusion column within the spine
of a patient.
[0106] As shown in FIGS. 2 and 3, the transverse aperture 170
extends the entire transverse length of the implant body and nearly
the entire height of the implant body. Thus, the size and shape of
the transverse aperture 170 approach the maximum possible
dimensions for the transverse aperture 170.
[0107] The transverse aperture 170 may be broken into two, separate
sections by an intermediate wall 172. The section of the transverse
aperture 170 proximate the IHF 194 is substantially rectangular in
shape; the other section of the transverse aperture 170 has the
shape of a curved arch. Other shapes and dimensions are suitable
for the transverse aperture 170. In particular, all edges of the
transverse aperture 170 may be rounded, smooth, or both. The
intermediate wall 172 may be made of the same material as the
remainder of the implant 101 (e.g., metal), or it may be made of
another material (e.g., PEEK) to form a composite implant 101. The
intermediate wall 172 may offer one or more of several advantages,
including reinforcement of the implant 101 and improved bone graft
containment.
[0108] The embodiment of the invention illustrated in FIGS. 2 and 3
is especially well suited for a PLIF surgical procedure. TLIF
surgery is done through the posterior (rear) part of the spine and
is essentially like an extended PLIF procedure. The TLIF procedure
was developed in response to some of the technical problems
encountered with a PLIF procedure. The main difference between the
two spine fusion procedures is that the TLIF approach to the disc
space is expanded by removing one entire facet joint; a PLIF
procedure is usually done on both sides by only taking a portion of
each of the paired facet joints.
[0109] By removing the entire facet joint, visualization into the
disc space is improved and more disc material can be removed. Such
removal should also provide for less nerve retraction. Because one
entire facet is removed, the TLIF procedure is only done on one
side: removing the facet joints on both sides of the spine would
result in too much instability. With increased visualization and
room for dissection, one or both of a larger implant and more bone
graft can be used in the TLIF procedure. Theoretically, these
advantages can allow the spine surgeon to distract the disc space
more and realign the spine better (re-establish the normal lumbar
lordosis).
[0110] Although the TLIF procedure offers some improvements over a
PLIF procedure, the anterior approach in most cases still provides
the best visualization, most surface area for healing, and the best
reduction of any of the approaches to the disc space. These
advantages must be weighed, however, against the increased
morbidity (e.g., unwanted aftereffects and postoperative
discomfort) of a second incision. Probably the biggest determinate
in how the disc space is approached is the comfort level that the
spine surgeon has with an anterior approach for the spine fusion
surgery. Not all spine surgeons are comfortable with operating
around the great vessels (aorta and vena cava) or have access to a
skilled vascular surgeon to help them with the approach. Therefore,
choosing one of the posterior approaches for the spine fusion
surgery is often a more practical solution.
[0111] The embodiment of the invention illustrated in FIGS. 4 and 5
is especially well suited when the spine surgeon elects a TLIF
procedure. Many of the features of the implant 101a illustrated in
FIGS. 4 and 5 are the same as those of the implant 101 illustrated
in FIGS. 2 and 3. Therefore, these features are given the same
reference numbers, with the addition of the letter "a," and are not
described further.
[0112] There are several differences, however, between the two
embodiments. For example, unlike the substantially rectangular
shape of the implant 101, the implant 101a has a curved shape.
Further, the chamfers 106 and anti-expulsion edge 108 of the
implant 101 are replaced by curves or rounded edges for the implant
101a. Still further, the TLIF procedure often permits use of a
larger implant 101a which, in turn, may affect the size and shape
of the predetermined vertical aperture 160a.
[0113] The substantially constant 9 mm width of the transverse rim
200 of the implant 101 is replaced with a larger, curved transverse
rim 200a. The width of the transverse rim 200a is 9 mm in the
regions adjacent the anterior 140a and posterior 150a portions.
That width gradually increases to 11 mm, however, near the center
of the transverse rim 200a. The additional real estate provided by
the transverse rim 200a (relative to the transverse rim 200) allows
the shape of the vertical aperture 160a to change, in cross
section, from approximating a football to approximating a
boomerang.
[0114] The implant 101a may also have a lordotic angle to
facilitate alignment. The lateral side 130a depicted at the top of
the implant 101a is preferably generally greater in height than the
opposing lateral side 130a. Therefore, the implant 101a may better
compensate for the generally less supportive bone found in certain
regions of the vertebral endplate.
[0115] As shown in FIG. 4, the transverse aperture 170a extends the
entire transverse length of the implant body and nearly the entire
height of the implant body. FIG. 5 highlights an alternative
transverse aperture 170a. As illustrated in FIG. 5, the transverse
aperture 170a is broken into two, separate sections by an
intermediate wall 172a. Thus, the dimensions of the transverse
aperture 170a shown in FIG. 5 are much smaller than those for the
transverse aperture 170a shown in FIG. 4. The two sections of the
alternative transverse aperture 170a are each illustrated as
substantially rectangular in shape and extending nearly the entire
height of the implant body; other sizes and shapes are possible for
one or both sections of the alternative transverse aperture
170a.
[0116] The intermediate wall 172a may be made of the same material
as the remainder of the implant 101a (e.g., metal), or it may be
made of another material (e.g., PEEK) to form a composite implant
101a. It is also possible to extend the intermediate wall 172a,
whether made of metal, PEEK, ultra-high molecular weight
polyethylene (UHMWPE), or another material, to eliminate entirely
the transverse aperture 170a. Given the reinforcement function of
the intermediate wall 172a, the length of the vertical aperture
160a can be extended (as shown in FIG. 5) beyond the top surface
110a and into the anterior portion 140a of the implant 101a.
[0117] The top surface 110a of the implant 101a need not include
the roughened topography 180a. This difference permits the implant
101a, at least for certain applications, to be made entirely of a
non-metal material. Suitable materials of construction for the
implant 101a of such a design (which would not be a composite)
include PEEK, hedrocel, UHMWPE, other radiolucent soft plastics,
and additional materials as would be known to an artisan.
[0118] The embodiments of the invention described above are best
suited for one or more of the ALIF, PLIF, and TLIF surgical
procedures. Another embodiment of the invention is better suited
for cervical fusion procedures. This embodiment is illustrated in
FIGS. 6 and 7 as the interbody spinal implant 201.
[0119] Because there is not a lot of disc material between the
vertebral bodies in the cervical spine, the discs are usually not
very large. The space available for the nerves is also not that
great, however, which means that even a small cervical disc
herniation may impinge on the nerve and cause significant pain.
There is also less mechanical load on the discs in the cervical
spine as opposed to the load that exists lower in the spine. Among
others, these differences have ramifications for the design of the
implant 201.
[0120] The implant 201 is generally smaller in size than the other
implant embodiments. In addition, the lower mechanical load
requirements imposed by the cervical application typically render a
composite implant unnecessary. Therefore, the implant 201 is
generally made entirely of metal (e.g., titanium) and devoid of
other materials (e.g., PEEK).
[0121] With specific reference to FIG. 6, the implant 201 includes
a body having a top surface 210, a bottom surface 220, opposing
lateral sides 230, and opposing anterior 240 and posterior 250
portions. One or both of the top surface 210 and the bottom surface
220 has a roughened topography 280 for gripping adjacent bone and
inhibiting migration of the implant 201. The implant 201 is
substantially hollow and has a generally oval shape with smooth,
rounded, or both smooth and rounded edges.
[0122] The implant 201 includes at least one vertical aperture 260
that extends the entire height of the implant body. The vertical
aperture 260 further defines a transverse rim 300.
[0123] As illustrated in FIG. 6, the implant 201 has an opening 290
in the posterior portion 250. The opening 290 has a number of
functions. One function is to facilitate manipulation of the
implant 201 by the caretaker. Thus, the caretaker may insert a
surgical tool into the opening 290 and, through the engagement
between the surgical tool and the opening 290, manipulate the
implant 201. The opening 290 may be threaded to enhance the
engagement.
[0124] The implant 201 may further include at least one transverse
aperture 270. Like the vertical aperture 260, the size and shape of
the transverse aperture 270 are carefully chosen (and
predetermined) to achieve a preferable design tradeoff for the
particular application envisioned for the implant 201. For example,
as shown in FIG. 6, the transverse aperture 270 may extend the
entire transverse length of the implant body and nearly the entire
height of the implant body. Thus, the size and shape of the
transverse aperture 270 approach the maximum possible dimensions
for the transverse aperture 270.
[0125] As illustrated in FIG. 6, the implant 201 may be provided
with a solid rear wall 242. The rear wall 242 extends the entire
width of the implant body and nearly the entire height of the
implant body. Thus, the rear wall 242 essentially closes the
anterior portion 240 of the implant 201. The rear wall 242 may
offer one or more of several advantages, including reinforcement of
the implant 201 and improved bone graft containment. In the
cervical application, it may be important to prevent bone graft
material from entering the spinal canal.
[0126] Alternative shapes for the implant 201 are possible. As
illustrated in FIG. 7, for example, the implant 201 may have a
generally box shape which gives the implant 201 increased cortical
bone coverage. Like the implant 201 shown in FIG. 6, the implant
201 shown in FIG. 7 has a curved transverse rim 300 in the area of
the anterior portion 240. The shape of the posterior portion 250 of
the implant 201 is substantially flat, however, and the shape of
the transverse rim 300 in the area of the posterior portion 250 is
substantially square. Thus, the posterior portion 250 provides a
face that can receive impact from a tool, such as a surgical
hammer, to force the implant 201 into position.
[0127] The implant 201 may also have a lordotic angle to facilitate
alignment. As illustrated in FIGS. 6 and 7, the anterior portion
240 is preferably generally greater in height than the posterior
portion 250. Therefore, the implant 201 may better compensate for
the generally less supportive bone found in certain regions of the
vertebral endplate. As an example, four degrees of lordosis may be
built into the implant 201 to help restore balance to the
spine.
[0128] Certain embodiments of the implant 1, 101, 101a, and 201 are
generally shaped (i.e., made wide) to maximize contact with the
apophyseal rim of the vertebral endplates. They are designed to be
impacted between the endplates, with fixation to the endplates
created by an interference fit and annular tension. Thus, the
implants 1, 101, 101a, and 201 are shaped and sized to spare the
vertebral endplates and leave intact the hoop stress of the
endplates. A wide range of sizes are possible to capture the
apophyseal rim, along with a broad width of the peripheral rim,
especially in the posterior region. It is expected that such
designs will lead to reduced subsidence. As much as seven degrees
of lordosis (or more) may be built into the implants 1, 101, 101a,
and 201 to help restore cervical balance.
[0129] When endplate-sparing spinal implant 1, 101, 101a, and 201
seats in the disc space against the apophyseal rim, it should still
allow for deflection of the endplates like a diaphragm. This means
that, regardless of the stiffness of the spinal implant 1, 101,
101a, and 201, the bone graft material inside the spinal implant 1,
101, 101a, and 201 receives load, leading to healthy fusion. The
vertical load in the human spine is transferred though the
peripheral cortex of the vertebral bodies. By implanting an
apophyseal-supporting inter-body implant 1, 101, 101a, and 201, the
natural biomechanics may be better preserved than for conventional
devices. If this is true, the adjacent vertebral bodies should be
better preserved by the implant 1, 101, 101a, and 201, hence
reducing the risk of adjacent segment issues.
[0130] In addition, the dual-acid etched roughened topography 80,
180, 180a, and 280 of the top surface 30, 130, 130a, and 230 and
the bottom surface 40, 140, 140a, and 240 along with the broad
surface area of contact with the end-plates, is expected to yield a
high pull-out force in comparison to conventional designs. As
enhanced by the sharp edges 8 and 108, a pull-out strength of up to
3,000 nt may be expected. The roughened topography 80, 180, 180a,
and 280 creates a biological bond with the end-plates over time,
which should enhance the quality of fusion to the bone. Also, the
in-growth starts to happen much earlier than the bony fusion. The
center of the implant 1, 101, 101a, and 201 remains open to receive
bone graft material and enhance fusion. Therefore, it is possible
that patients might be able to achieve a full activity level sooner
than for conventional designs.
[0131] The spinal implant 1, 101, 101a, and 201 according to the
invention offers several advantages relative to conventional
devices. Such conventional devices include, among others,
ring-shaped cages made of allograft bone material, threaded
titanium cages, and ring-shaped cages made of PEEK or carbon
fiber.
[0132] In some aspects, the implant 1, 101, 101a, and 201 includes
an integration plate 82, 182, 182a, and 282, for example, as shown
in FIG. 8A-FIG. 10 and FIG. 12. In addition, a lateral implant 301
having a substantially rectangular shape may include an integration
plate 382, for example, as shown in FIG. 11. The lateral implant
301 comprises the same general features as the implant 1, 101,
101a, and 201, including a top surface 310, a bottom surface 320,
lateral sides 330, opposing anterior 340 and posterior 350
portions, an opening 390, as well as at least one vertical aperture
360 that extends the entire height of the implant body, and one or
more transverse apertures 370 that extend the entire transverse
length of the implant body.
[0133] The integration plate, shown in the drawings as component 82
(FIG. 8A and FIG. 8B), 182 (FIG. 10), 182a (FIG. 9), 382 (FIGS.
11), and 282 (FIG. 12), respectively, includes the roughened
surface topography 80, 180, 180a, 280, and 380, and is connectable
to either or both of the top surface 10, 110, 110a, 210, and 310 or
bottom surface 20, 120, 120a, 220, and 320. The integration plate
82, 182, 182a, 282, and 382 includes a top surface 81, 181, 181a,
281, and 381; a bottom surface 83, 183, 183a, 283, and 383; an
anterior portion 41, 141, 141a, 241, and 341; a posterior portion
51, 151, 151a, 251, and 351; and at least one vertical aperture 61,
161, 161a, 261, and 361. The anterior portion 41, 141, 141a, 241,
and 341 preferably aligns with the anterior portion 40, 140, 140a,
240, and 340 of the main body of the implant 1, 101, 101a, 201, and
301, respectively, and the posterior portion 51, 151, 151a, 251,
and 351 aligns with the posterior portion 50, 150, 150a, 250, and
350 of the main body of the implant 1, 101, 101a, 201, and 301,
respectively. The vertical aperture 61, 161, 161a, 261, and 361
preferably aligns with the vertical aperture 60, 160, 160a, 260,
and 360 of the main body of the implant 1, 101, 101a, 201, and 301,
respectively. Thus, the integration plate vertical aperture 61,
161, 161a, 261, and 361 and the body vertical aperture 60, 160,
160a, 260, and 360 preferably comprise substantially the same
shape.
[0134] The top surface 81, 181, 181a, 281, and 381 of the
integration plate 82, 182, 182a, 282, and 382 preferably comprises
the roughened topography 80, 180, 180a, 280, and 380. The bottom
surface 83, 183, 183a, 283, and 383 of the integration plate 82,
182, 182a, 282, and 382 preferably comprises a reciprocal connector
structure, such as a plurality of posts 84, 184, 184a, 284, and 384
that align with and insert into a corresponding connector structure
such as a plurality of holes 12, 112, 112a, 212, and 312 on the top
surface 10, 110, 110a, 210, and 310 and/or bottom surface 20, 120,
120a, 220, and 320 of the main body of the implant 1, 101, 101a,
201, and 301, respectively, and thus facilitate the connection
between the integration plate 82, 182, 182a, 282, and 382 and the
main body of the implant 1, 101, 101a, 201, and 301. Thus,
integration plates 82, 182, 182a, 282, and 382 with different
sizes, shapes, or features may be used in connection with the
implant 1, 101, 101a, 201, and 301, for example, to accommodate
attributes of the spine of the patient to which the implant 1, 101,
101a, 201, and 301 is to be implanted. Among these different sizes,
shapes, and features are lordotic angles; anti-expulsion edges 8,
108, 108a, 208, and 308; and anti-expulsion angles as described
throughout this specification.
[0135] The implant 1, 101, 101a, 201, and 301 is configured to
receive the integration plate 82, 182, 182a, 282, and 382,
respectively. Thus, for example, the top surface 10, 110, 110a,
210, and 310 and/or bottom surface 20, 120, 120a, 220, and 320 of
the implant 1, 101, 101a, 201, and 301 may be recessed, and
comprise a plurality of holes 12, 112, 112a, 212, and 312 that mate
with the plurality of posts 84, 184, 184a, 284, and 384 on the
bottom surface 83, 183, 183a, 283, and 383 of the integration plate
82, 182, 182a, 282, and 382. Thus, the plurality of posts 84, 184,
184a, 284, and 384 are inserted into the plurality of holes 12,
112, 112a, 212, and 312.
[0136] FIG. 8A and FIG. 8B show that the top surface 10 is recessed
and comprises a plurality of holes 12, but the recessed bottom
surface 20 and its holes 12 are not shown. FIG. 9 shows that the
top surface 110a is recessed and comprises a plurality of holes
112a, but the recessed bottom surface 120a and its holes 112a are
not shown. FIG. 10 shows that the top surface 110 is recessed and
comprises a plurality of holes 112, but the recessed bottom surface
120 and its holes 112 are not shown. FIG. 11 shows that the top
surface 310 is recessed and comprises a plurality of holes 312, but
the recessed bottom surface 320 and its holes 312 are not shown.
FIG. 12 shows that the top surface 210 is recessed and comprises a
plurality of holes 212, but the recessed bottom surface 220 and its
holes 212 are not shown.
[0137] The recess comprises a (first) depth D, which in some
aspects is uniform throughout the top surface 10, 110, 110a, 210,
and 310 and/or bottom surface 20, 120, 120a, 220, and 320. In some
aspects, the recess comprises a depth D and a second depth D'. For
example, implant 1, 101, 101a, 201, and 301 may be recessed to
depth D to form the anterior side of the ridge 11, 111, 111a, 211,
and 311, and recessed at second depth D' to form the posterior side
of the ridge 11, 111, 111a, 211, and 311, and vice versa. As well,
implant 1, 101, 101a, 201, and 301 may be recessed to depth D to
form the one lateral side of the ridge 11, 111, 111a, 211, and 311,
and recessed at second depth D' to form the other lateral side of
the ridge 11, 111, 111a, 211, and 311.
[0138] The top surface 10, 110, 110a, 210, and 310 and/or bottom
surface 20, 120, 120a, 220, and 320 may thus be inclined/declined
in the direction of depth D to second depth D', thereby
establishing a slope between the depth D and second depth D'
points. This slope may be used, for example, to allow an
integration plate 82, 182, 182a, 282, and 382 attached to the top
extend higher at a desired point at the surface of the implant 1,
101, 101a, 201, and 301. For example, the anterior edge 41, 141,
141a, 241, and 341, or the posterior edge 51, 151, 151a, 251, and
351, or one of the lateral side walls 31, 131, 131a, 231, and 331
of an integration plate 82, 182, 182a, 282, and 382 may extend
above the horizontal plane of the top surface 10, 110, 110a, 210,
and 310 and/or bottom surface 20, 120, 120a, 220, and 320 of the
implant 1, 101, 101a, 201, and 301. The extending portion of the
integration plate 82, 182, 182a, 282, and 382 may comprise an
anti-expulsion edge 8, 108, 108a, 208, and 308, for example, as
shown in FIGS. 13A-13M.
[0139] The an anti-expulsion edge 8, 108, 108a, 208, and 308
resists movement of the implant 1, 101, 101a, 201, and 301 seated
in the joint space of the spine. The anti-expulsion edge 8, 108,
108a, 208, and 308 tends to "dig" into the vertebral end-plate
bone, and thereby helps to resist expulsion of the implant 1, 101,
101a, 201, and 301 from the intervertebral space following
implantation. The anti-expulsion edge 8, 108, 108a, 208, and 308
may be present on the top surface 10, 110, 110a, 210, and 310, the
bottom surface 20, 120, 120a, 220, and 320, or both surfaces of the
implant 1, 101, 101a, 201, and 301, which may depend on whether the
implant 1, 101, 101a, 201, and 301 includes an integration plate
82, 182, 182a, 282, and 382 attached to the top surface 10, 110,
110a, 210, and 310 and/or the bottom surface 20, 120, 120a, 220,
and 320.
[0140] By way of example, FIG. 13A shows an anti-expulsion edge 8
on the top surface 10 and bottom surface 20 and at the anterior
face 40 of the implant 1. Each anti-expulsion edge 8 protrudes
above the plane of the top surface 10 and bottom surface 20, with
the amount of protrusion increasing toward the anterior face 40 and
the highest protrusion height P at the anterior-most edge of the
top surface 10 or bottom surface 20. As shown in FIG. 13B, the
protruding anti-expulsion edge 8 exposes a protruding surface
9.
[0141] An anti-expulsion edge 8, 108, 108a, 208, and 308 may be
oriented toward the anterior portion 40, 140, 140a, 240, and 340,
or the posterior portion 50, 150, 150a, 250, and 350, or either of
the opposing lateral sides 30, 130, 130a, 230, and 330. The
orientation of the anti-expulsion edge 8, 108, 108a, 208, and 308
may depend on the intended orientation of the implant 1, 101, 101a,
201, and 301 when it has been implanted between vertebrae in the
patient.
[0142] FIGS. 13C-13H show different perspective views of different
embodiments of the implant 101 and 101a, with the amount of
protrusion increasing toward the posterior face 150 and 150a and
the highest protrusion height P at the posterior-most edge of the
top surface 110 and 110a or bottom surface 120 and 120a. The
protruding anti-expulsion edge 108 and 108a exposes a protruding
surface 109 and 109a. FIGS. 13I-13K show different perspective
views of an embodiment of the implant 301, with the amount of
protrusion increasing toward one of the opposing lateral sides 330
and the highest protrusion height P at the most lateral edge of the
top surface 310 or bottom surface 320. The protruding
anti-expulsion edge 308 exposes a protruding surface 309. FIGS. 13L
and 13M show different perspective views of an embodiment of the
implant 201, with the amount of protrusion increasing toward the
anterior portion 240 and the highest protrusion height P at the
anterior-most edge of the top surface 210 or bottom surface 220.
The protruding anti-expulsion edge 208 exposes a protruding surface
209.
[0143] In some preferred embodiments, the integration plate 82,
182, 182a, 282, and 382 establishes the anti-expulsion edge 8, 108,
108a, 208, and 308 for either or both of the top surface 10, 110,
110a, 210, and 310 and bottom surface 20, 120, 120a, 220, and 320
of the implant 1, 101, 101a, 201, and 301. Different integration
plates 82, 182, 182a, 282, and 382 may be used to establish a range
of highest protrusion heights P.
[0144] The integration plate 82, 182, 182a, 282, and 382 has a
thickness T, that is preferably substantially uniform throughout.
Thus, for example, in embodiments where the integration plate 82,
182, 182a, 282, and 382 is substantially flush with the plane of
the top surface 10, 110, 110a, 210, and 310 and/or bottom surface
20, 120, 120a, 220, and 320 (e.g., no protruding surface 9, 109,
109a, 209, and 309) (e.g., FIG. 13N), the recess depth D in the
implant body substantially corresponds to the thickness T of the
integration plate 82, 182, 182a, 282, and 382, and the implant 1,
101, 101a, 201, and 301 does not have the second recess depth D'
(e.g., depth D is substantially uniform throughout).
[0145] In some embodiments, the integration plate 82, 182, 182a,
282, and 382 has a thickness T, that is preferably substantially
uniform throughout, and the top surface 10, 110, 110a, 210, and 310
and/or bottom surface 20, 120, 120a, 220, and 320 are recessed to a
first depth D about one portion and a second depth D' about a
second portion. For example, the posterior portion of the top
surface 10, 110, 110a, 210, and 310 and/or bottom surface 20, 120,
120a, 220, and 320 may comprise a recess depth D, and the anterior
portion of the top surface 10, 110, 110a, 210, and 310 and/or
bottom surface 20, 120, 120a, 220, and 320 may comprise the second
recess depth D'. In such embodiments, when recess depth D is
greater than the second recess depth D', the anterior portion 41,
141, 141a, 241, and 341 of the integration plate 82, 182, 182a,
282, and 382 will protrude to the height P. In such embodiments,
when recess depth D is lesser than the second recess depth D', the
posterior portion 51, 151, 151a, 251, and 351 of the integration
plate 82, 182, 182a, 282, and 382 will protrude to the height P. In
some aspects, one of the lateral portions of the top surface 10,
110, 110a, 210, and 310 and/or bottom surface 20, 120, 120a, 220,
and 320 may comprise a recess depth D, and the opposing lateral
portion of the top surface 10, 110, 110a, 210, and 310 and/or
bottom surface 20, 120, 120a, 220, and 320 may comprise the second
recess depth D'. In such embodiments, when recess depth D is
greater than the second recess depth D', one of the lateral side
portions 31, 131, 131a, 231, and 331 of the integration plate 82,
182, 182a, 282, and 382 will protrude to the height P.
[0146] The recess depth D, the second recess depth D', and the
thickness T may each independently be from about 0.1 mm to about 10
mm. In preferred aspects, the recess depth D, the second recess
depth D', and the thickness T may each independently be from about
1 mm to about 5 mm. Thus, for example, the recess depth D, the
second recess depth D', and the thickness T may independently be
about 0.1 mm, about 0.25 mm, about 0.5 mm, about 0.75 mm, about 1
mm, about 1.25 mm, about 1.5 mm, about 1.75 mm, about 2 mm, about
2.25 mm, about 2.5 mm, about 2.75 mm, about 3 mm, about 3.25 mm,
about 3.5 mm, about 3.75 mm, about 4 mm, about 4.25 mm, about 4.5
mm, about 4.75 mm, about 5 mm, 5.5 mm, about 6 mm, about 6.5 mm,
about 7 mm, about 75 mm, or about 8 mm.
[0147] The implant 1, 101, 101a, 201, and 301 may comprise a
lordotic angle .theta., e.g., may be wedge-shaped to facilitate
sagittal alignment. Thus, for example, the anterior portion 40,
140, 140a, 240, and 340 of the implant 1, 101, 101a, 201, and 301
may comprise a height that is larger than the height of the
posterior portion 50, 150, 150a, 250, and 350. The lordotic angle
.theta. may be established by the implant 1, 101, 101a, 201, and
301 itself, or may be established by the integration plate 82, 182,
182a, 282, and 382 when combined with the implant 1, 101, 101a,
201, and 301.
[0148] The lordotic angle O of the implant 1 preferably closely
approximates, or otherwise is substantially the same as, the angle
of lordosis of the spine of the patient where the implant 1, 101,
101a, 201, and 301 will be implanted. In some aspects, the
integration plate 82, 182, 182a, 282, and 382 increases the
lordotic angle O by about 3% to about 5%, measured according to the
angle of lordosis of a particular patient's spine.
[0149] The implant 1, 101, 101a, 201, and 301 may have a lordotic
angle O about 3%, about 3.3%, about 3.5%, about 3.7%, about 4%,
about 4.3%, about 4.5%, about 4.7%, or about 5% greater than the
patient's angle of lordosis, though percentages greater than 5% or
lesser 3% are possible. The increase of about 3% to about 5%
preferably results from the combination of the protruding height of
the integration plate 82, 182, 182a, 282, and 382 on the top
portion 10, 110, 110a, 210, and 310 and bottom portion 20, 120,
120a, 220, and 320 of the implant 1, 101, 101a, 201, and 301. For
example, as shown in FIG. 14A and FIG. 14B, the anti-expulsion edge
8 protrudes to a height sufficient to increase the overall height H
of the anterior portion 40 of the implant 1 such that implant 1 has
a lordotic angle O that is about 3% to about 5% greater than the
patient's angle of lordosis. In this regard, the interplay between
the depth D, the second depth D', and the integration plate
thickness T, which together establish the protrusion height P
establish the lordotic angle O of the implant 1, 101, 101a, 201,
and 301.
[0150] The expulsion-resistant edge 8, 108, 108a, 208, and 308 may
comprise an anti-expulsion edge angle E. The anti-expulsion edge
angle E may be from about 80 degrees to about 100 degrees. In
preferred aspects, the anti-expulsion edge angle E may be measured
by taking into account the lordosis angle O of the implant 1, 101,
101a, 201, and 301. In highly preferred aspects, the anti-expulsion
edge angle E is measured by subtracting half of the lordotic angle
O from 90 degrees. For example, where the lordosis angle O of the
implant 1, 101, 101a, 201, and 301 is 12 degrees, the
anti-expulsion edge angle E is 84 degrees (90-(12.times.0.5)). The
anti-expulsion edge angle E may be about 80 degrees, about 81
degrees, about 82 degrees, about 83 degrees, about 84 degrees,
about 85 degrees, about 86 degrees, about 86.5 degrees, about 87
degrees, about 88 degrees, or about 89 degrees.
[0151] The integration plate 82, 182, 182a, 282, and 382 may be
used with an implant suitable for ALIF (e.g., implant 1,
integration plate 82), PLIF (e.g., implant 101, integration plate
182), or TLIF fusion (e.g., implant 101a, integration plate 182a);
may be used with an implant suitable for cervical fusion (e.g.,
implant 201, integration plate 282); and may be used with an
implant suitable for lateral lumbar insertion (e.g., implant 301,
integration plate 382). The integration plate 82, 182, 182a, 282,
and 382 is preferably metal, and may be used with a metal implant.
The metal integration plate 82, 182, 182a, 282, and 382 may also be
used with a molded plastic or polymer implant, or a composite
implant. In some aspects, the integration plate 82, 182, 182a, 282,
and 382 may also comprise a plastic, polymeric, or composite
material.
[0152] The reciprocal connector such as the post 84, 184, 184a,
284, and 384 preferably is secured within the connector of the body
such as the hole 12, 112, 112a, 212, and 312 to mediate the
connection between the integration plate 82, 182, 182a, 282, and
382 and the implant 1, 101, 101a, 201, and 301. The connection
should be capable of withstanding significant loads and shear
forces when implanted in the spine of the patient. The connection
between the post 84, 184, 184a, 284, and 384 and the hole 12, 112,
112a, 212, and 312 may comprise a friction fit. In some aspects, an
adhesive may be used to further strengthen any of the integration
plate 82, 182, 182a, 282, and 382 and implant 1, 101, 101a, 201,
and 301 connections. An adhesive may comprise a cement, glue,
polymer, epoxy, solder, weld, or other suitable binding
material.
[0153] Vertebrae are comprised of trabecular bone of varying
densities. In opposition to the interbody disks this is thickened
subchondral bone. Due to the lower density bone composition within
the vertebral body load induced stresses can change the shape of
the body. Movement, including walking, lifting, stretching, and
other activities that implicate movement and flexing of the spine
produce load forces that impact disc material, and also induce
flexing and compression of the vertebral endplate surfaces. For
example, under load stress, the thickened subchondral bone of the
vertebral endplate surface may flex inward toward the core of the
vertebrae or outward toward the disc in the intervertebral space.
Load forces and vertebral endplate bone flexing under load forces
may be taken into account in terms of the configuration of the
implant 1, 101, 101a, 201, and 301. A goal is to balance the amount
of surface area of the implant 1, 101, 101a, 201, and 301 that
contacts vertebral endplate surfaces so that the spine is
adequately supported under load forces and stresses with the amount
of surface area of bone graft material used in conjunction with the
implant 1, 101, 101a, 201, and 301 to facilitate integration of the
implant 1, 101, 101a, 201, and 301 and new bone growth.
[0154] For each implant 1, 101, 101a, 201, and 301, the top surface
10, 110, 110a, 210, and 310 and/or bottom surface 20, 120, 120a,
220, and 320 make contact with the vertebral endplate bone, and
surround the vertical aperture 60, 160, 160a, 260, and 360 into
which a bone graft material is preferably placed and housed during
implantation. When occupying the space of the vertical aperture 60,
160, 160a, 260, and 360, the bone graft material also makes contact
with the vertebral endplate bone. In this sense, portions of the
top surface 10, 110, 110a, 210, and 310 and/or bottom surface 20,
120, 120a, 220, and 320 and/or bone graft material bear at least a
fraction of the load forces and stresses of the spine where the
implant is placed. The total load force or stress is not
necessarily borne equally by the implant surfaces and the bone
graft material, and is not necessarily distributed equally about
the top surface 10, 110, 110a, 210, and 310 and/or bottom surface
20, 120, 120a, 220, and 320 of the implant 1, 101, 101a, 201, and
301; certain sections, or subsections of the implant 1, 101, 101a,
201, and 301 may bear a higher share of the load force relative to
other sections.
[0155] To establish and maintain optimal contact between the
implant surfaces, the bone graft material and the vertebral
endplate bone, the location, direction, and extent, among other
aspects, of flexing of vertebral endplate bone under load stress,
and under normal conditions may be taken into account. Other
factors such as the type of vertebrae between which the implant 1,
101, 101a, 201, and 301 is/will be implanted (e.g., cervical,
thoracic, lumbar), the specific vertebrae (e.g., L-1/L-2 versus
L-5/S-1) between which the implant 1, 101, 101a, 201, and 301
is/will be implanted, the location where the implant 1, 101, 101a,
201, and 301 is/will be seated in the intervertebral space, the
size, shape, and configuration of the implant 1, 101, 101a, 201,
and 301 itself (including the dimensions, shape, and location of
the vertical aperture 60, 160, 160a, 260, and 360 and transverse
rim), and the amount of disc material retained in the
intervertebral space may also be taken into account. In addition,
the direction of insertion, and the insertion procedure (e.g.,
ALIF, PLIF, TLIF, etc.) may also be taken into account.
[0156] For example, the practitioner may position the implant 1,
101, 101a, 201, and 301 in the intervertebral space at a loci where
bone graft material exposed through the vertical aperture 60, 160,
160a, 260, and 360 may make maximal contact with vertebral endplate
bone, whether at rest/under normal conditions, or under particular
load stress. The practitioner may also position the implant 1, 101,
101a, 201, and 301 in the intervertebral space at a loci where a
higher amount of the load stress will be borne by the posterior,
anterior, or lateral portion of the top surface 10, 110, 110a, 210,
and 310 and/or bottom surface 20, 120, 120a, 220, and 320. By way
of example, but not of limitation, FIG. 15A shows the placement of
the implant 1 in the intervertebral space (upper vertebrae not
shown) on top of the apophyseal rim of the lower vertebrae endplate
such that posterior portion 50 of the implant 1 is positioned
proximal to the posterior edge of the endplate. FIG. 15B shows an
anterior view of the example in FIG. 15A, with the implant 1
between the upper and lower vertebrae. FIG. 15C shows the placement
of the implant 301 in the intervertebral space (upper vertebrae not
shown) on top of the apophyseal rim of the lower vertebrae endplate
such that a lateral side 330 of the implant 301 is positioned
proximal to the posterior edge of the endplate and the anterior 340
and posterior 350 portions of the implant 301 are positioned
laterally. FIG. 15D shows an anterior view of the example in FIG.
15C, with the implant 301 between the upper and lower
vertebrae.
[0157] Numerous other positions of the implant 1, 101, 101a, 201,
and 301 in the intervertebral space are possible. For example, as
shown in FIG. 16A and FIG. 16B, the practitioner may include two
implants 101 in the intervertebral space (upper vertebrae not
shown). In this non-limiting example, the posterior portion 150 of
each implant 101 faces the posterior edge of the endplate. Where
two implants 101 are used, the implants 101 may be positioned
substantially parallel relative to each other, or may be positioned
at any suitable angle relative to each other. In FIG. 16B, the
arrows illustrate the direction in which the implant 101 was
inserted in a PLIF procedure.
[0158] A single implant 101 may be positioned at an oblique angle
off of the anterior-posterior direction of the vertebrae, for
example, as shown in FIG. 16C and FIG. 16D. A single implant 101a
that has a curved profile may be positioned proximal to the
anterior edge of the vertebral endplate, as shown in FIGS. 16E and
16F. The curvature of the implant 101 may approximate the curvature
of the vertebral endplate. The implant 101a may also be positioned
proximal to the posterior edge of the vertebral endplate (not
shown) or proximate to one of the lateral sides of the vertebral
endplate (not shown). The implant 101a may also be positioned more
toward the center of the vertebral endplate, and less toward one of
the edges of the vertebral endplate. The implant 101a may also be
positioned at an oblique angle off of the anterior-posterior
direction of the vertebrae.
[0159] The shape and configuration of the implant 1, 101, 101a,
201, and 301 itself may facilitate the goal of balancing the amount
of surface area of the implant 1, 101, 101a, 201, and 301 and the
amount of surface area of bone graft material that contact
vertebral endplate bone. In some aspects, the vertical aperture 60,
160, 160a, 260, and 360 may be lengthened and/or widened and/or
positioned in different locations about the top surface 10, 110,
110a, 210, and 310 and/or bottom surface 20, 120, 120a, 220, and
320. For example, with respect to varying the position, the
vertical aperture 60, 160, 160a, 260, and 360 may be positioned
substantially in the center of the body of the implant 1, 101,
101a, 201, and 301, or may be positioned off-center, such as toward
the anterior 40, 140, 140a, 240, and 340, or the posterior 50, 150,
150a, 250, and 350, or one of the lateral sides 30, 130, 130a, 230,
and 330. The dimensions and location of the vertical aperture 60,
160, 160a, 260, and 360 may be based on the insertion path of the
implant 1, 101, 101a, 201, and 301 and/or the final location and
orientation in the disc space. The dimensions and location of the
vertical aperture 60, 160, 160a, 260, and 360 may also be based on
the frictional characteristics of the roughened surface topography
80, 180, 180a, 280, and 380.
[0160] In some aspects, the shape of the vertical aperture 60, 160,
160a, 260, and 360 may be varied. For example, the shape may be
substantially circular, elliptical, or D-shaped. In some aspects,
the anterior, posterior, or lateral sides of the circle, ellipse,
or D-shape may bow outward (e.g., a rhomboid oval) or inward (e.g.,
hourglass shape). The shape may also include straight edges,
including a substantially diamond, triangular, rectangular,
quadrilateral, or polygonal shape, including a star shape. The
shape may comprise an irregular shape or form. The particular shape
may be based on the insertion path of the implant 1, 101, 101a,
201, and 301 and/or the final location and orientation in the disc
space. The shape of the vertical aperture 60, 160, 160a, 260, and
360 may also be based on the frictional characteristics of the
roughened surface topography 80, 180, 180a, 280, and 380.
[0161] Thus, in some aspects, the shape, dimensions and location of
the vertical aperture 61, 160, 160a, 260, and 360 may be based on
the insertion path of the implant 1, 101, 101a, 201, and 301 and/or
the final location and orientation in the disc space. In some
aspects, the shape, dimensions and location of the vertical
aperture 60, 160, 160a, 260, and 360 may be based on the insertion
path of the implant 1, 101, 101a, 201, and 301, and/or the final
location and orientation in the disc space, and/or the frictional
characteristics of the roughened surface topography 80, 180, 180a,
280, and 380.
[0162] In some aspects, the implant 1, 101, 101a, 201, and 301
comprises an integration plate 82, 182, 182a, 282, and 382 on
either or both of the top surface 10, 110, 110a, 210, and 310 and
bottom surface 20, 120, 120a, 220, and 320, having a vertical
aperture 61, 161, 161a, 261, and 361. Thus, the bone graft material
is loaded into the vertical aperture 61, 161, 161a, 261, and 361 of
the integration plate 82, 182, 182a, 282, and 382 and the vertical
aperture 60, 160, 160a, 260, and 360 of the implant 1, 101, 101a,
201, and 301. Accordingly, bone graft material housed in the
implant 1, 101, 101a, 201, and 301 may extend through the implant
vertical aperture 60, 160, 160a, 260, and 360 and through the
integration plate vertical aperture 61, 161, 161a, 261, and 361.
The surface of the graft material may thus establish, and
preferably maintain, contact the vertebral endplate bone.
[0163] As with the vertical aperture 60, 160, 160a, 260, and 360,
the integration plate vertical aperture 61, 161, 161a, 261, and 361
may be lengthened and/or widened and/or positioned in different
locations about the top surface 81, 181, 181a, 281, and 381 and/or
bottom surface 83, 183, 183a, 283, and 383. For example, with
respect to varying the position, the vertical aperture 61, 161,
161a, 261, and 361 may be positioned substantially in the center of
the integration plate 82, 182, 182a, 282, and 382, or may be
positioned off-center, such as toward the anterior 41, 141, 141a,
241, and 341, or the posterior 51, 151, 151a, 251, and 351, or one
of the lateral sides of the integration plate 82, 182, 182a, 282,
and 382. The dimensions and location of the vertical aperture 61,
161, 161a, 261, and 361 may be based on the insertion path of the
implant 1, 101, 101a, 201, and 301 and/or the final location and
orientation in the disc space. The dimensions and location of the
vertical aperture 61, 161, 161a, 261, and 361 may also be based on
the frictional characteristics of the roughened surface topography
80, 180, 180a, 280, and 380.
[0164] In some aspects, the shape of the integration plate vertical
aperture 61, 161, 161a, 261, and 361 may be varied. For example,
the shape may be substantially circular, elliptical, or D-shaped.
In some aspects, the anterior, posterior, or lateral sides of the
circle, ellipse, or D-shape may bow outward (e.g., a rhomboid oval)
or inward (e.g., hourglass shape). The shape may also include
straight edges, including a substantially diamond, triangular,
rectangular, quadrilateral, or polygonal shape, including a star
shape. The shape may comprise an irregular shape or form. The
particular shape may be based on the insertion path of the implant
1, 101, 101a, 201, and 301 and/or the final location and
orientation in the disc space. The shape of the vertical aperture
61, 161, 161a, 261, and 361 may also be based on the frictional
characteristics of the roughened surface topography 80, 180, 180a,
280, and 380.
[0165] Thus, in some aspects, the shape, dimensions and location of
the vertical aperture 61, 161, 161a, 261, and 361 may be based on
the insertion path of the implant 1, 101, 101a, 201, and 301 and/or
the final location and orientation in the disc space. In some
aspects, the shape, dimensions and location of the vertical
aperture 61, 161, 161a, 261, and 361 may be based on the insertion
path of the implant 1, 101, 101a, 201, and 301, and/or the final
location and orientation in the disc space, and/or the frictional
characteristics of the roughened surface topography 80, 180, 180a,
280, and 380.
[0166] The implant vertical aperture 60, 160, 160a, 260, and 360
preferably aligns with the integration plate vertical aperture 61,
161, 161a, 261, and 361. Thus each implant body vertical aperture
60, 160, 160a, 260, and 360 and integration plate vertical aperture
61, 161, 161a, 261, and 361 preferably has substantially the same
length, substantially the same width, substantially the same shape,
and substantially the same location on their respective
surfaces.
[0167] Nevertheless, in some aspects, the integration plate
vertical aperture 61, 161, 161a, 261, and 361 may be longer and/or
wider and/or positioned differently than its implant vertical
aperture 60, 160, 160a, 260, and 360 counterpart. For example, the
vertical aperture 60, 160, 160a, 260, and 360 may be narrower in
terms of length and width relative to the integration plate
vertical aperture 61, 161, 161a, 261, and 361 (which are
comparatively larger) such that the graft material occupies a wider
surface area at its top or bottom relative to the center mass. Such
a configuration may be desirable for purposes of using less bone
graft material by lessening the inner volume of the implant 1, 101,
101a, 201, and 301 to be filled with bone graft material. In this
sense, the surface area of the bone graft material that will
ultimately contact vertebral endplate bone is maximized (because
the integration plate vertical aperture 61, 161, 161a, 261, and 361
has a larger berth), while the amount of bone graft material that
does not contact vertebral endplate bone, but rather occupies space
in the voids of the implant 1, 101, 101a, 201, and 301, is
minimized (because the implant vertical aperture 60, 160, 160a,
260, and 360 has a smaller berth). For example, the inner volume of
the implant 1, 101, 101a, 201, and 301 may comprise a "V" shape, or
an "X" or hourglass shape.
[0168] One or more of the anterior 40, 140, 140a, 240, and 340
edges, posterior 50, 150, 150a, 250, and 350 edges, and lateral
side 30, 130, 130a, 230, and 330 edges of the implant may be
rounded or tapered (see, e.g., FIG. 1A-FIG. 7). The rounding or
tapering is preferably present on at least the insertion face of
the implant 1, 101, 101a, 201, and 301. The rounding or tapering
may facilitate insertion of the implant 1, 101, 101a, 201, and 301
by lessening friction or the possibility of snagging vertebral
endplate bone as the implant 1, 101, 101a, 201, and 301 is placed
and positioned in the intervertebral space. As well, the rounding
or tapering may help to avoid snagging or damaging blood vessels
and nerves in and around the insertion site.
[0169] The implant vertical aperture 60, 160, 160a, 260, and 360
comprises dimensions and a shape, and defines a transverse rim 100
(implant 1), 200 (implant 101), 200a (implant 101a), 300 (implant
201), and 400 (implant 301). The integration plate vertical
aperture 61, 161, 161a, 261, and 361 comprises dimensions and a
shape, and defines an integration plate transverse rim 86 (implant
1), 186 (implant 101), 186a (implant 101a), 286 (implant 201), and
386 (implant 301). The transverse rim 100, 200, 200a, 300, and 400
is also defined by the position of the implant vertical aperture
60, 160, 160a, 260, and 360 or the integration plate vertical
aperture 61, 161, 161a, 261, and 361 (e.g., centered, toward the
anterior edge, toward the posterior edge, or toward one of the
lateral edges) on the top surface 10, 110, 110a, 210, and 310, the
bottom surface 20, 120, 120a, 220, and 320, or the integration
plate top surface 81, 181, 181a, 281, and 381.
[0170] Each transverse rim 100, 200, 200a, 300, and 400 and
integration plate transverse rim 86, 186, 186a, 286, and 386
comprise a posterior portion having a posterior portion width P, an
anterior portion having an anterior portion width A, and a first
lateral section having a first lateral side width L, and a second
lateral section having a second lateral side width L'. For example,
the posterior portion width P may comprise the distance between the
posterior edge of the implant 1, 101, 101a, 201, and 301 or
posterior edge of the integration plate 82, 182, 182a, 282, and 382
and the posterior edge of the implant vertical aperture 61, 161,
161a, 261, and 361 or the integration plate vertical aperture 60,
160, 160a, 260, and 360. The transverse rim 100, 200, 200a, 300,
and 400 or the transverse rim of the integration plate 86, 186,
186a, 286, and 386 effectively surrounds the vertical aperture 60,
160, 160a, 260, and 360 or 61, 161, 161a, 261, and 361,
respectively.
[0171] The transverse rim 100, 200, 200a, 300, and 400 may be
present on the top surface 10, 110, 110a, 210, and 310 and the
bottom surface 20, 120, 120a, 220, and 320 of the implant 1, 101,
101a, 201, and 301. The transverse rim of the integration plate 86,
186, 186a, 286, and 386 may be present on the top surface 81, 181,
181a, 281, and 381 of the integration plate 82, 182, 182a, 282, and
382. The top surface 81, 181, 181a, 281, and 381 is the surface
that is exposed and visible, and may make contact with vertebral
endplate bone. Thus, for example, the top surface 81, 181, 181a,
281, and 381 of an integration plate 82, 182, 182a, 282, and 382
that occupies the bottom portion 20, 120, 120a, 220, and 320 is the
bottom-most surface of the implant 1, 101, 101a, 201, and 301. For
clarification, the top surface of the bottom integration plate is
effectively the bottom surface of the implant.
[0172] The configuration of the implant vertical aperture 60, 160,
160a, 260, and 360 and/or the integration plate vertical aperture
61, 161, 161a, 261, and 361 (e.g., the shape, dimensions, and
position on the top or bottom surface) and the transverse rim 100,
200, 200a, 300, and 400 defined by the aperture shape, dimensions,
and position distributes the spine load force (e.g., the downward
force/stress that is produced by movement of vertebrae from
walking, lifting, moving, stretching, pushing, pulling, sitting,
standing, jumping, laying supine, etc.) about the implant 1, 101,
101a, 201, and 301. The load force may change and/or shift to
different sections of the implant 1, 101, 101a, 201, and 301 (e.g.,
posterior, anterior, or one of the lateral sides) depending on the
type and/or direction of movement by the patient, as well as the
level of exertion underlying the movement, among other things.
[0173] The posterior portion width P may be about 1 mm to about 15
mm, about 1 mm to about 7 mm, about 1 mm to about 6 mm, about 1 mm
to about 5 mm, about 1 mm to about 4 mm, about 1 mm to about 3 mm,
about 2 mm to about 6 mm, about 2 mm to about 5 mm, about 2 mm to
about 4 mm, about 2 mm to about 3 mm, about 3 mm to about 8 mm,
about 3 mm to about 7 mm, about 3 mm to about 6 mm, about 4 mm to
about 7 mm, about 4 mm to about 6 mm, about 5 to about 7 mm, or
about 5 mm to about 6 mm. In some aspects, the posterior portion
width P may be about 1 mm, about 2 mm, about 3 mm, about 4 mm,
about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, about
10 mm, about 11 mm, about 12 mm, about 13 mm, about 14 mm, or about
15 mm.
[0174] The anterior portion width A may be about 1 mm to about 15
mm, about 1 mm to about 8 mm, about 1 mm to about 7 mm, about 1 mm
to about 6 mm, about 1 mm to about 5 mm, about 1 mm to about 4 mm,
about 1 mm to about 3 mm, about 2 mm to about 10 mm, about 2 mm to
about 9 mm, about 2 mm to about 8 mm, about 2 mm to about 7 mm,
about 2 mm to about 6 mm, about 2 mm to about 5 mm, about 2 mm to
about 4 mm, about 2 mm to about 3 mm, about 3 mm to about 10 mm,
about 3 mm to about 9 mm, about 3 mm to about 8 mm, about 3 mm to
about 7 mm, about 3 mm to about 6 mm, about 3 mm to about 5 mm,
about 4 mm to about 9 mm, about 4 mm to about 8 mm, about 4 mm to
about 7 mm, about 4 mm to about 6 mm, about 5 to about 10 mm, about
5 mm to about 9 mm, about 5 mm to about 8 mm, about 5 mm to about 7
mm, about 6 mm to about 8 mm, or about 6 mm to about 7 mm. In some
aspects, the anterior portion width A may be about 1 mm, about 2
mm, about 3 mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm,
about 8 mm, about 9 mm, about 10 mm, about 11 mm, about 12 mm,
about 13 mm, about 14 mm, or about 15 mm.
[0175] The first lateral side width L and second lateral side width
L' may each independently be about 1 mm to about 10 mm, about 1 mm
to about 9 mm, about 1 mm to about 8 mm, about 1 mm to about 7 mm,
about 1 mm to about 6 mm, about 1 mm to about 5 mm, about 1 mm to
about 4 mm, about 1 mm to about 3 mm, about 2 mm to about 10 mm,
about 2 mm to about 9 mm, about 2 mm to about 8 mm, about 2 mm to
about 7 mm, about 2 mm to about 6 mm, about 2 mm to about 5 mm,
about 2 mm to about 4 mm, about 2 mm to about 3 mm, about 3 mm to
about 10 mm, about 3 mm to about 9 mm, about 3 mm to about 8 mm,
about 3 mm to about 7 mm, about 3 mm to about 6 mm, about 3 mm to
about 5 mm, about 3 mm to about 4 mm, about 4 mm to about 10 mm,
about 4 mm to about 9 mm, about 4 mm to about 8 mm, about 4 mm to
about 7 mm, about 4 mm to about 6 mm, about 5 to about 10 mm, about
5 mm to about 9 mm, about 5 mm to about 8 mm, about 5 mm to about 7
mm, about 6 mm to about 8 mm, or about 6 mm to about 7 mm. In some
aspects, the first lateral side width L and second lateral side
width L' may each independently be about 1 mm, about 2 mm, about 3
mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm,
about 9 mm, or about 10 mm.
[0176] The posterior portion width P, anterior portion width A,
first lateral side width L, and second lateral side width L' may
have the same size relative to each other, or may have a different
size relative to each other. When the position of the vertical
aperture 60, 160, 160a, 260, and 360 is positioned toward the
anterior portion 40, 140, 140a, 240, and 340, the anterior portion
width A decreases and the posterior portion width increases,
relative to a comparable implant 1, 101, 101a, 201, and 301 in
which the vertical aperture 60, 160, 160a, 260, and 360 is
centered, and vice versa. When the position of the vertical
aperture 60, 160, 160a, 260, and 360 is positioned toward a lateral
side 30, 130, 130a, 230, and 330, the first lateral side width L
(e.g., the side to which the vertical aperture 60, 160, 160a, 260,
and 360 is positioned closest) decreases and the second lateral
side width increases, relative to a comparable implant 1, 101,
101a, 201, and 301 in which the vertical aperture 60, 160, 160a,
260, and 360 is centered, and vice versa. The same holds true with
respect to the positioning of the integration plate vertical
aperture 61, 161, 161a, 261, and 361.
[0177] The posterior portion width P, anterior portion width A,
and/or first and second lateral side width L and L' may allow for
better stress sharing between the implant 1, 101, 101a, 201, and
301 and the adjacent vertebral endplates, and helps to compensate
for the weaker posterior endplate bone. In some aspects, the
transverse rim 100, 200, 200a, 300, and 400 has a generally large
surface area and contacts the vertebral endplate. The transverse
rim 100, 200, 200a, 300, and 400 may act to better distribute
contact stresses upon the implant 1, 101, 101a, 201, and 301, and
minimize the risk of subsidence while maximizing contact with the
apophyseal supportive bone. Some studies have challenged the
characterization of the posterior endplate bone as weaker.
[0178] The posterior portion width P, anterior portion width A,
and/or first and second lateral side width L and L' comprise
dimensions of the implant top surface 10, 110, 110a, 210, and 310,
the implant bottom surface 20, 120, 120a, 220, and 320, and/or the
integration plate top surface 81, 181, 181a, 281, and 381. Measured
from the edge of one lateral side 30, 130, 130a, 230, and 330 to
the edge of the other lateral side 30, 130, 130a, 230, and 330, the
implant top surface 10, 110, 110a, 210, and 310, the implant bottom
surface 20, 120, 120a, 220, and 320, and/or the integration plate
top surface 81, 181, 181a, 281, and 381 may be about 5 mm to about
50 mm in width, and in some aspects may be about 7 mm to about 15
mm, about 8 mm to about 12 mm, about 9 mm to about 12 mm, about 9
mm to about 11 mm, about 10 mm to about 20 mm, about 10 mm to about
18 mm, about 10 mm to about 17 mm, about 11 mm to about 19 mm,
about 11 mm to about 17 mm, about 12 mm to about 17 mm, about 12 mm
to about 16 mm, about 15 mm to about 25 mm, about 15 mm to about 23
mm, about 16 mm to about 24 mm, about 16 mm to about 23 mm, about
17 mm to about 24 mm, about 17 mm to about 23 mm, about 18 mm to
about 22 mm, about 20 mm to about 25 mm, about 20 mm to about 22
mm, about 30 mm to about 50 mm, about 30 mm to about 48 mm, about
30 mm to about 45 mm, about 30 mm to about 42 mm, about 31 mm to
about 45 mm, about 31 mm to about 43 mm, about 31 mm to about 41
mm, about 32 mm to about 42 mm, or about 32 mm to about 40 mm in
width. Measured from the edge of one lateral side 30, 130, 130a,
230, and 330 to the edge of the other lateral side 30, 130, 130a,
230, and 330, the implant top surface 10, 110, 110a, 210, and 310,
the implant bottom surface 20, 120, 120a, 220, and 320, and/or the
integration plate top surface 81, 181, 181a, 281, and 381 may be
about 9 mm, about 10 mm, about 11 mm, about 12 mm, about 13 mm,
about 14 mm, about 15 mm, about 16 mm, about 17 mm, about 18 mm,
about 19 mm, about 20 mm, about 21 mm, about 22 mm, about 25 mm,
about 30 mm, about 31 mm, about 32 mm, about 33 mm, about 34 mm,
about 35 mm, about 36 mm, about 37 mm, about 38 mm, about 39 mm, or
about 40 mm in width.
[0179] Measured from the edge of the posterior portion 50, 150,
150a, 250, and 350 to the edge of the anterior portion 40, 140,
140a, 240, and 340, the implant top surface 10, 110, 110a, 210, and
310, the implant bottom surface 20, 120, 120a, 220, and 320, and/or
the integration plate top surface 81, 181, 181a, 281, and 381 may
be about 10 mm to about 70 mm in length, and in some aspects may be
about 10 mm to about 20 mm, about 10 mm to about 18 mm, about 11 mm
to about 19 mm, about 11 mm to about 18 mm, about 11 mm to about 17
mm, about 12 mm to about 16 mm, about 18 mm to about 34 mm, about
18 mm to about 32 mm, about 20 mm to about 34 mm, about 20 mm to
about 32 mm, about 20 mm to about 31 mm, about 20 mm to about 30
mm, about 20 mm to about 28 mm, about 20 mm to about 27 mm, about
21 mm to about 32 mm, about 21 mm to about 30 mm, about 21 mm to
about 28 mm, about 21 mm to about 27 mm, about 22 mm to about 32
mm, about 22 mm to about 31 mm, about 30 mm to about 70 mm, about
35 mm to about 65 mm, about 38 mm to about 64 mm, about 38 mm to
about 62 mm, about 38 mm to about 60 mm, about 39 mm to about 62
mm, about 39 mm to about 61 mm, or about 40 mm to about 60 mm in
length. Measured from the edge of the posterior portion 50, 150,
150a, 250, and 350 to the edge of the anterior portion 40, 140,
140a, 240, and 340, the implant top surface 10, 110, 110a, 210, and
310, the implant bottom surface 20, 120, 120a, 220, and 320, and/or
the integration plate top surface 81, 181, 181a, 281, and 381 may
be about 9 mm, about 10 mm, about 11 mm, about 12 mm, about 13 mm,
about 14 mm, about 15 mm, about 16 mm, about 17 mm, about 18 mm,
about 19 mm, about 20 mm, about 21 mm, about 22 mm, about 23 mm,
about 24 mm, about 25 mm, about 26 mm, about 27 mm, about 28 mm,
about 29 mm, about 30 mm, about 31 mm, about 35 mm, about 40 mm,
about 45 mm, about 55 mm, or about 60 mm in length.
[0180] The size and shape of the vertical aperture 60, 160, 160a,
260, and 360, as well as the integration plate vertical aperture
61, 161, 161a, 261, and 361 are carefully chosen to achieve a
preferable design tradeoff for the particular application
envisioned for the implant 1, 101, 101a, 201, and 301. The vertical
aperture 60, 160, 160a, 260, and 360 or integration plate vertical
aperture 61, 161, 161a, 261, and 361 preferably maximizes the
surface area of the top surface 10, 110, 110a, 210, and 310,
integration plate top surface 81, 181, 181a, 281, and 381, and/or
bottom surface 20, 120, 120a, 220, and 320, while at the same time
maximizing both the capacity for radiographic visualization and
access to the bone graft material. It is highly preferred that the
bone graft material bear at least some of the load forces of the
spine once the implant 1, 101, 101a, 201, and 301 is implanted.
[0181] The vertical aperture 60, 160, 160a, 260, and 360, and the
integration plate vertical aperture 61, 161, 161a, 261, and 361
each preferably comprises a maximum width at its center. The width
of the vertical aperture 60, 160, 160a, 260, and 360, and the
integration plate vertical aperture 61, 161, 161a, 261, and 361 may
range from about 20% to about 80% of the distance between opposing
lateral sides. In some aspects, the width ranges from about 40% to
about 80% of the distance between the opposing lateral sides. In
some aspects, the width ranges from about 50% to about 70% of the
distance between the opposing lateral sides. In some aspects, the
width ranges from about 50% to about 65% of the distance between
the opposing lateral sides. In some aspects, the width ranges from
about 60% to about 70% of the distance between the opposing lateral
sides. In some aspects, the width ranges from about 55% to about
75% of the distance between the opposing lateral sides. In some
aspects, the width ranges from about 60% to about 80% of the
distance between the opposing lateral sides. In some aspects, the
width is about 40%, about 45%, about 50%, about 55%, about 60%,
about 65%, about 70%, about 75%, about 80%, about 85%, or about 90%
of the distance between the opposing lateral sides. Preferably, the
width of the vertical aperture 60, 160, 160a, 260, and 360, or the
integration plate vertical aperture 61, 161, 161a, 261, and 361
comprises the dimension between the lateral sides.
[0182] The length of the vertical aperture 60, 160, 160a, 260, and
360, and the integration plate vertical aperture 61, 161, 161a,
261, and 361 may range from about 20% to about 80% of the distance
between the anterior and posterior edges. In some aspects, the
length ranges from about 40% to about 80% of the distance between
the anterior and posterior edges. In some aspects, the length
ranges from about 50% to about 70% of the distance between the
anterior and posterior edges. In some aspects, the length ranges
from about 50% to about 65% of the distance between the anterior
and posterior edges. In some aspects, the length ranges from about
60% to about 70% of the distance between the anterior and posterior
edges. In some aspects, the length ranges from about 55% to about
75% of the distance between the anterior and posterior edges. In
some aspects, the length ranges from about 60% to about 80% of the
distance between the anterior and posterior edges. In some aspects,
the length is about 40%, about 45%, about 50%, about 55%, about
60%, about 65%, about 70%, about 75%, about 80%, about 85%, or
about 90% of the distance between the anterior and posterior edges.
Preferably, the length of the vertical aperture 60, 160, 160a, 260,
and 360, or the integration plate vertical aperture 61, 161, 161a,
261, and 361 comprises the dimension between the anterior and
posterior edges. The size of the length and the size of the width
of the vertical aperture 60, 160, 160a, 260, and 360, or the
integration plate vertical aperture 61, 161, 161a, 261, and 361 may
vary independently of each other.
[0183] The implant top surface 10, 110, 110a, 210, and 310, the
implant bottom surface 20, 120, 120a, 220, and 320, the integration
plate top surface 81, 181, 181a, 281, and 381, the vertical
aperture 60, 160, 160a, 260, and 360, and the integration plate
vertical aperture 61, 161, 161a, 261, and 361 each independently
comprises a surface area, e.g., that of the horizontal plane (foot
print). The surface area of the implant top surface 10, 110, 110a,
210, and 310, and the implant bottom surface 20, 120, 120a, 220,
and 320, including the integration plate top surface 81, 181, 181a,
281, and 381 may comprise the roughened surface topography 80, 180,
180a, 280, and 380 (contact surface), the area comprising rounded
or tapered edges, if rounded or tapered edges are present, and the
area occupied by the vertical aperture 60, 160, 160a, 260, and 360,
or the integration plate vertical aperture 61, 161, 161a, 261, and
361.
[0184] The drawings show examples different possible sizes, shapes,
and positions of the vertical aperture 60, 160, 160a, 260, and 360
and integration plate vertical aperture 61, 161, 161a, 261, and
361. The drawings simply illustrate various configurations, and are
not to be considered limiting in any way.
[0185] The vertical aperture 60, 61 may comprise any suitable
shape, dimensions, and position on the implant 1. For example, FIG.
17A shows the vertical aperture 60, 61 substantially in the center
of the implant 1. FIG. 17B shows the vertical aperture 60, 61 with
a wider length and width such that the posterior portion width P,
anterior portion width A, first lateral side width L, and second
lateral side width L' are diminished relative to the embodiment
shown in FIG. 17A. FIG. 17C shows an example of the vertical
aperture 60, 61 positioned to a lateral side of the implant 1. FIG.
17D shows an example of the vertical aperture 60, 61 having a wider
length and width, and positioned nearer to the anterior portion 40
of the implant 1.
[0186] The length and width of the vertical aperture 160 may be
enlarged such that the vertical aperture 160 spans most of the
surface area of the top surface 110, or the vertical aperture 161
may be positioned toward the anterior portion 140. Such
configurations, in addition to other possible configurations, are
shown from a top perspective in FIGS. 18A-18D. For example, FIG.
18A shows the vertical aperture 160, 161 substantially in the
center of the implant 101, though the anterior-most edge of the
aperture 160, 161 is positioned more toward the anterior edge of
the roughened surface topography 180 of the top surface 110. FIG.
18B shows the enlarged vertical aperture 160, 161 that is also
positioned nearer to the posterior portion 150. FIG. 18C shows a
vertical aperture 160, 161 having a smaller profile that is
positioned proximate to the posterior portion 150. FIG. 18D shows a
vertical aperture 160, 161 having a smaller profile that is
positioned nearer to the a lateral side 130.
[0187] Similar to the embodiments shown in FIG. 18, FIG. 19
illustrates different shapes and dimensions of the vertical
aperture 160a and 161a of the curved implant 101a. Although the
implant 101a curves, and the vertical aperture 160a and 161a has
curved edges as well, it is not necessary the outer arc of the
implant 101a curve and aperture 160a and 161a lateral curves are
identical. The shape of the implant 101a and the shape of the
vertical aperture 160a and 161a may be independent of each
other.
[0188] FIG. 19A shows the vertical aperture 160a, 161a
substantially in the center of the implant 101a, though the
anterior-most edge of the aperture 160a, 161a is positioned more
toward the anterior edge of the roughened surface topography 180a
of the top surface 110a.
[0189] FIG. 19B shows the enlarged vertical aperture 160a, 161a
that is also positioned nearer to the posterior portion 150a. FIG.
19C shows a vertical aperture 160a, 161a having a smaller profile
that is positioned proximate to the posterior portion 150a. FIG.
19D shows a vertical aperture 160a, 161a having a smaller profile
that is positioned nearer to the a lateral side 130a.
[0190] FIG. 20A shows the vertical aperture 260, 261 substantially
in the center of the implant 201. FIG. 20B shows the vertical
aperture 260, 261 positioned nearer to the second lateral side.
FIG. 20C shows a wider vertical aperture 260, 261 positioned
substantially in the center of the implant 201. FIG. 20D shows the
vertical aperture 260, 261 positioned nearer to the posterior
portion 250.
[0191] The vertical aperture 360 and 361 may be positioned
substantially in the center of the implant 301. The centered
configuration is shown from a top perspective in FIG. 21A. FIG. 21B
shows the vertical aperture 360, 361 positioned nearer to the
anterior portion 350. FIG. 21C shows the vertical aperture 360, 361
positioned proximate to a lateral side 330. FIG. 21D shows an
enlarged vertical aperture 360, 361 positioned substantially in the
center of the implant 301.
Example Surgical Methods
[0192] The following examples of surgical methods are included to
more dearly demonstrate the overall nature of the invention. These
examples are exemplary, not restrictive, of the invention.
[0193] Certain embodiments of the invention are particularly suited
for use during interbody spinal implant procedures currently known
in the art. For example, the disc space may be accessed using a
standard mini open retroperitoneal laparotomy approach. The center
of the disc space is located by AP fluoroscopy taking care to make
sure the pedicles are equidistant from the spinous process. The
disc space is then incised by making a window in the annulus for
insertion of certain embodiments of the spinal implant 1 (a 32 or
36 mm window in the annulus is typically suitable for insertion).
The process according to the invention minimizes, if it does not
eliminate, the cutting of bone. The endplates are cleaned of all
cartilage with a curette, however, and a size-specific rasp (or
broach) may then be used.
[0194] Use of a rasp preferably substantially minimizes or
eliminates removal of bone, thus substantially minimizing or
eliminating impact to the natural anatomical arch, or concavity, of
the vertebral endplate while preserving much of the apophyseal rim.
Preservation of the anatomical concavity is particularly
advantageous in maintaining biomechanical integrity of the spine.
For example, in a healthy spine, the transfer of compressive loads
from the vertebrae to the spinal disc is achieved via hoop stresses
acting upon the natural arch of the endplate. The distribution of
forces, and resultant hoop stress, along the natural arch allows
the relatively thin shell of subchondral bone to transfer large
amounts of load.
[0195] During traditional fusion procedures, the vertebral endplate
natural arch may be significantly removed due to excessive surface
preparation for implant placement and seating. This is especially
common where the implant is to be seated near the center of the
vertebral endplate or the implant is of relatively small
medial-lateral width. Breaching the vertebral endplate natural arch
disrupts the biomechanical integrity of the vertebral endplate such
that shear stress, rather than hoop stress, acts upon the endplate
surface. This redistribution of stresses may result in subsidence
of the implant into the vertebral body.
[0196] Preferred embodiments of the surgical method minimize
endplate bone removal on the whole, while still allowing for some
removal along the vertebral endplate far lateral edges where the
subchondral bone is thickest. Still further, certain embodiments of
the interbody spinal implant 1, 101, 101a, 201, and 301 include
smooth, rounded, and highly radiused posterior portions and lateral
sides which may minimize extraneous bone removal for endplate
preparation and reduce localized stress concentrations. Thus,
interbody surgical implant 1, 101, 101a, 201, and 301 and methods
of using it are particularly useful in preserving the natural arch
of the vertebral endplate and minimizing the chance of implant
subsidence.
[0197] Because the endplates are spared during the process of
inserting the spinal implant 1, 101, 101a, 201, and 301, hoop
stress of the inferior and superior endplates is maintained. Spared
endplates allow the transfer of axial stress to the apophasis.
Endplate flexion allows the bone graft placed in the interior of
the spinal implant 1 to accept and share stress transmitted from
the endplates. In addition, spared endplates minimize the concern
that BMP might erode the cancellous bone.
[0198] Certain embodiments of the interbody spinal implant 1, 101,
101a, 201, and 301 may maintain a position between the vertebral
endplates due, at least in part, to resultant annular tension
attributable to press-fit surgical implantation and,
post-operatively, improved osteointegration at the top surface 10,
110, 110a, 210, and 310; the bottom surface 20, 120, 120a, 220, and
320; or both surfaces.
[0199] Surgical implants and methods tension the vertebral annulus
via distraction. These embodiments and methods may also restore
spinal lordosis, thus improving sagittal and coronal alignment.
Implant systems currently known in the art require additional
instrumentation, such as distraction plugs, to tension the annulus.
These distraction plugs require further tertiary instrumentation,
however, to maintain the lordotic correction during actual spinal
implant insertion. If tertiary instrumentation is not used, then
some amount of lordotic correction may be lost upon distraction
plug removal. Interbody spinal implant 1, according to certain
embodiments of the invention, is particularly advantageous in
improving spinal lordosis without the need for tertiary
instrumentation, thus reducing the instrument load upon the
surgeon. This reduced instrument load may further decrease the
complexity, and required steps, of the implantation procedure.
[0200] Certain embodiments of the spinal implant 1, 101, 101a, 201,
and 301 may also reduce deformities (such as isthmic
spondylolythesis) caused by distraction implant methods.
Traditional implant systems require secondary or additional
instrumentation to maintain the relative position of the vertebrae
or distract collapsed disc spaces. In contrast, interbody spinal
implant 1, 101, 101a, 201, and 301 may be used as the final
distractor and thus maintain the relative position of the vertebrae
without the need for secondary instrumentation.
[0201] Certain embodiments collectively comprise a family of
implants, each having a common design philosophy. These implants
and the associated surgical technique have been designed to address
at least the ten, separate challenges associated with the current
generation of traditional anterior spinal fusion devices listed
above in the Background section of this document.
[0202] Embodiments of the invention allow end-plate preparation
with custom-designed rasps. These rasps preferably have a geometry
matched with the geometry of the implant. The rasps conveniently
remove cartilage from the endplates and remove minimal bone, only
in the postero-lateral regions of the vertebral end-plates. It has
been reported in the literature that the end-plate is the strongest
in postero-lateral regions.
[0203] After desired annulotomy and discectomy, embodiments of the
invention first adequately distract the disc space by inserting
(through impaction) and removing sequentially larger sizes of very
smooth distractors, which have been size matched with the size of
the available implant 1, 101, 101a, 201, and 301. Once adequate
distraction is achieved, the surgeon prepares the end-plate with a
rasp. There is no secondary instrumentation required to keep the
disc space distracted while the implant 1, 101, 101a, 201, and 301
is inserted, as the implant 1, 101, 101a, 201, and 301 has
sufficient mechanical strength that it is impacted into the disc
space. In fact, the height of the implant 1, 101, 101a, 201, and
301 is preferably about 1 mm greater than the height of the rasp
used for end-plate preparation, to create some additional tension
in the annulus by implantation, which creates a stable implant
construct in the disc space.
[0204] The implant geometry has features which allow it to be
implanted via any one of an anterior, antero-lateral, or lateral
approach, providing tremendous intra-operative flexibility of
options. The implant 1, 101, 101a, 201, and 301 has adequate
strength to allow impact. The sides of the implant 1, 101, 101a,
201, and 301 have smooth surfaces, included rounded or tapered
edges to allow for easy implantation and, specifically, to prevent
binding of the implant 1, 101, 101a, 201, and 301 to soft tissues
during implantation.
[0205] The invention encompasses a number of different implant 1,
101, 101a, 201, and 301 configurations, including a one-piece,
titanium-only implant and a composite implant formed of top and
bottom plates (components) made out of titanium. The surfaces
exposed to the vertebral body are dual acid etched to allow for
bony in-growth over time, and to provide resistance against
expulsion. The top and bottom titanium plates are assembled
together with the implant body that is injection molded with PEEK.
The net result is a composite implant that has engineered stiffness
for its clinical application.
[0206] It is believed that an intact vertebral end-plate deflects
like a diaphragm under axial compressive loads generated due to
physiologic activities. If a spinal fusion implant is inserted in
the prepared disc space via a procedure which does not destroy the
end-plates, and if the implant contacts the end-plates only
peripherally, the central dome of the end-plates can still deflect
under physiologic loads. This deflection of the dome can pressurize
the bone graft material packed inside the spinal implant, hence
allowing it to heal naturally. The implant 1, 101, 101a, 201, and
301 designed according to certain embodiments allows the vertebral
end-plate to deflect and allows healing of the bone graft into
fusion.
[0207] The top and bottom surfaces of the implant may be made out
of titanium and are dual acid etched. The dual acid etching process
creates a highly roughened texture on these surfaces, which
generates tremendous resistance to expulsion. The width of these
dual acid etched surfaces is very broad and creates a large area of
contact with the vertebral end-plates, further increasing the
resistance to expulsion.
[0208] The implant 1, 101, 101a, 201, and 301 according to certain
embodiments of the invention has a large foot-print, and offers
several sizes. Because there is no secondary instrument required to
maintain distraction during implantation, all the medial-lateral
(ML) exposure is available as implantable ML width of the implant
1, 101, 101a, 201, and 301. This feature allows the implant 1, 101,
101a, 201, and 301 to contact the vertebral end-plates at the
peripheral apophyseal rim, where the end-plates are the strongest
and least likely to subside.
[0209] Further, there are no teeth on the top and bottom surfaces
(teeth can create stress risers in the end-plate, encouraging
subsidence). Except for certain faces, all the implant surfaces
have heavily rounded edges, creating a low stress contact with the
end-plates. The wide rim of the top and bottom surfaces, in contact
with the end-plates, creates a low-stress contact due to the large
surface area. Finally, the implant construct has an engineered
stiffness to minimize the stiffness mismatch with the vertebral
body which it contacts.
[0210] Even the titanium-only embodiment of the invention has been
designed with large windows to allow for radiographic evaluation of
fusion, both through AP and lateral X-rays. A composite implant
minimizes the volume of titanium, and localizes it to the top and
bottom surfaces. The rest of the implant is made of PEEK which is
radiolucent and allows for free radiographic visualization.
[0211] Although illustrated and described above with reference to
certain specific embodiments and examples, the invention is
nevertheless not intended to be limited to the details shown.
Rather, various modifications may be made in the details within the
scope and range of equivalents of the claims and without departing
from the spirit of the invention. It is expressly intended, for
example, that all ranges broadly recited in this document include
within their scope all narrower ranges which fall within the
broader ranges. In addition, features of one embodiment may be
incorporated into another embodiment.
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