U.S. patent application number 15/626596 was filed with the patent office on 2017-10-05 for orthopaedic implant with porous structural member.
This patent application is currently assigned to SMed-TA/TD, LLC. The applicant listed for this patent is SMed-TA/TD, LLC. Invention is credited to Paul S. Nebosky, Gregory C. Stalcup.
Application Number | 20170281363 15/626596 |
Document ID | / |
Family ID | 53881137 |
Filed Date | 2017-10-05 |
United States Patent
Application |
20170281363 |
Kind Code |
A1 |
Nebosky; Paul S. ; et
al. |
October 5, 2017 |
ORTHOPAEDIC IMPLANT WITH POROUS STRUCTURAL MEMBER
Abstract
An orthopaedic implant includes an implant body having a first
surface with a first peak, a second surface opposite the first
surface, and a cavity formed therein that extends through the first
surface and second surface. The implant body is substantially
non-porous. A load bearing member comprising a substantially porous
material is held within the cavity. The load bearing member has a
first contact surface that extends out of the cavity past the first
peak of the first surface.
Inventors: |
Nebosky; Paul S.; (Fort
Wayne, IN) ; Stalcup; Gregory C.; (Fort Wayne,
IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SMed-TA/TD, LLC |
Columbia City |
IN |
US |
|
|
Assignee: |
SMed-TA/TD, LLC
Columbia City
IN
|
Family ID: |
53881137 |
Appl. No.: |
15/626596 |
Filed: |
June 19, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14637142 |
Mar 3, 2015 |
9700431 |
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15626596 |
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12540515 |
Aug 13, 2009 |
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14637142 |
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61088460 |
Aug 13, 2008 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2002/30677
20130101; A61F 2002/3097 20130101; A61F 2002/30261 20130101; A61F
2002/30971 20130101; A61F 2002/3008 20130101; A61F 2002/30622
20130101; A61F 2/447 20130101; A61F 2310/00293 20130101; A61F
2002/30593 20130101; A61F 2002/30492 20130101; A61F 2002/30733
20130101; A61F 2002/30322 20130101; A61F 2002/30451 20130101; A61F
2310/00023 20130101; A61F 2/3094 20130101; A61F 2002/305 20130101;
A61F 2/30965 20130101; A61F 2002/30028 20130101; A61F 2002/30841
20130101; A61F 2310/00017 20130101; A61F 2310/00203 20130101; A61F
2002/30599 20130101; A61F 2/4465 20130101; A61F 2002/30387
20130101 |
International
Class: |
A61F 2/44 20060101
A61F002/44 |
Claims
1. An orthopaedic implant, comprising: an implant body having a
first surface with a first peak, a second surface opposite said
first surface, and a cavity formed therein that extends through
said first surface and said second surface, said implant body being
substantially non-porous, said implant body further including a
third surface with an opening formed therethrough to said cavity
and a protrusion formed adjacent to said opening that extends away
from said third surface; and a load bearing member comprising a
substantially porous material held within said cavity, said load
bearing member having a first contact surface extending out of said
cavity past said first peak of said first surface.
2. The orthopaedic implant according to claim 1, wherein said load
bearing member has a second contact surface opposite said first
contact surface, said load bearing member having interconnecting
pores extending from said first contact surface to said second
contact surface, said load bearing member having a total volume and
said interconnecting pores in aggregate occupying at least 60% of
said total volume.
3. An orthopaedic implant, comprising: an implant body having a
first surface with a first peak, a second surface opposite said
first surface, a cavity formed therein that extends through said
first surface and said second surface, and a second cavity formed
therein that extends through said first surface and said second
surface, said implant body being substantially non-porous; and a
load bearing member comprising a substantially porous material held
within said cavity, said load bearing member having a first contact
surface extending out of said cavity past said first peak of said
first surface.
4. The orthopaedic implant according to claim 3, further comprising
a second load bearing member comprising a substantially porous
material held within said second cavity, said second load bearing
member having a third contact surface, said third contact surface
of said second load bearing member extending out of said second
cavity past said first peak of said first surface.
5. The orthopaedic implant according to claim 4, wherein said first
contact surface defines a first thickness relative to said first
surface and said third contact surface defines a second thickness
relative to said first surface, said second thickness being at
least equal to said first thickness.
6. The orthopaedic implant according to claim 5, wherein said
second thickness is greater than said first thickness.
7. The orthopaedic implant according to claim 4, wherein a porosity
of said second load bearing member is different than a porosity of
said load bearing member.
8. The orthopaedic implant according to claim 4, wherein said load
bearing member is formed of a first material and said second load
bearing member is formed of a second material which is different
than said first material.
9. The orthopaedic implant according to claim 3, wherein said load
bearing member has a second contact surface opposite said first
contact surface, said load bearing member having interconnecting
pores extending from said first contact surface to said second
contact surface, said load bearing member having a total volume and
said interconnecting pores in aggregate occupying at least 60% of
said total volume.
10. The orthopaedic implant according to claim 9, further
comprising a second load bearing member comprising a substantially
porous material held within said second cavity, said second load
bearing member having a third contact surface, said third contact
surface of said second load bearing member extending out of said
second cavity past said first peak of said first surface.
11. The orthopaedic implant according to claim 10, wherein a
porosity of said second load bearing member is different than a
porosity of said load bearing member.
12. The orthopaedic implant according to claim 10, wherein said
load bearing member is formed of a first material and said second
load bearing member is formed of a second material which is
different than said first material.
13. The orthopaedic implant according to claim 3, wherein said
implant body includes a third surface with an opening formed
therethrough to said cavity and a protrusion formed adjacent to
said opening that extends away from said third surface
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a division of U.S. patent application Ser. No.
14/637,142 entitled "ORTHOPAEDIC IMPLANT WITH POROUS STRUCTURAL
MEMBER", filed Mar. 3, 2015, which is incorporated herein by
reference. U.S. patent application Ser. No. 14/637,142 is a
continuation-in-part application based upon U.S. patent application
Ser. No. 12/540,515, entitled "ORTHOPAEDIC IMPLANT WITH POROUS
STRUCTURAL MEMBER", filed Aug. 13, 2009, which is incorporated
herein by reference. U.S. patent application Ser. No. 12/540,515 is
based upon U.S. provisional patent application Ser. No. 61/088,460,
entitled "SPINAL DEVICES", filed Aug. 13, 2008, which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to orthopaedic devices, and,
more particularly, to orthopaedic implants.
[0004] 2. Description of the Related Art
[0005] Most orthopaedic implants are formed from a metallic
material suitable for a given implant, such as a hip implant, knee
implant, glenoid implant, etc. In the case of articulating joints,
the implant may include a non-metallic load bearing surface, such
as an ultra high molecular weight polyethylene (UHMWPE). The UHMWPE
is attached to the metallic body of the implant, and provides the
implant with good wear characteristics and low friction.
[0006] It is also known to provide an implant with a porous bony
ingrowth surface. For example, a hip implant may include a porous
surface on the stem which is intended to allow bony ingrowth of the
proximal end of the femur bone. Such a porous surface may be in the
form of a metal porous surface which is bonded, such as by heat
sintering, to the stem of the implant. Examples of porous surfaces
of this type include a woven mesh, a fiber mesh and particles. Knee
implants are also known that include porous ingrowth surfaces that
can bear load from surrounding anatomic structures.
[0007] Porous surfaces of the type described above which are used
with implants are not typically part of a single structural member
with two opposed, external porous surfaces. For example, in a knee
implant, the distal surface of the implant can sit on the porous
material that is slightly above the substrate material, but the
porous material only typically has one external surface for tissue
ingrowth. For hip implants, the porous ingrowth surface is usually
provided as a coating on a structural component of the implant,
such as the stem.
[0008] In some orthopaedic applications, such as spinal cages, it
is beneficial to have a porous member that extends between two
external, load bearing surfaces of the implant. In such
arrangements, a cavity is typically formed between the two external
surfaces of the implant and filled with a porous ingrowth material,
which is typically a natural substance such as cancellous bone
tissue. Such an implant is described in U.S. Patent Application No.
2002/0091447 to Shimp et al. One problem with the implant described
by Shimp et al. is that harvesting sufficient cancellous bone
tissue to fill the cavity is expensive, and host rejection issues
can be a concern. Other similar implants that contemplate utilizing
natural or synthetic materials are described in U.S. Patent
Application Publication No. 2004/0210316 to King et al., and U.S.
Pat. No. 6,423,095 to Van Hoeck et al. In each of these described
implants, the porous material held in the cavity is fairly isolated
from bearing load from surrounding anatomic structures after
implantation, with external surfaces that are either flush or below
the most protruding external surface of the main implant body. This
is intentional, as the materials placed in the cavity tend to have
significantly lower strength than the implant body. However,
isolating the porous ingrowth material from bearing loads from
surrounding anatomic structures also decreases the amount of
surface area the porous ingrowth material has in contact with the
anatomic structures, which can slow down integration of the
implant. In addition, the porous materials placed in the cavity are
typically resorbable by the body and will not last throughout the
life of the implant.
[0009] What is needed in the art is an orthopaedic implant that can
overcome some of the disadvantages of known devices.
SUMMARY OF THE INVENTION
[0010] The present invention provides an orthopaedic implant with a
porous load bearing member held within a surface-to-surface cavity
formed in the implant's body that projects outwardly away from an
exterior surface of the implant.
[0011] The invention in one form is directed to an orthopaedic
implant that includes an implant body having a first surface with a
first peak, a second surface opposite the first surface, and a
cavity formed therein that extends through the first surface and
second surface. The implant body is substantially non-porous. A
load bearing member comprising a substantially porous material is
held within the cavity. The load bearing member has a first contact
surface that extends out of the cavity past the first peak of the
first surface.
[0012] The invention in another form is directed to an orthopaedic
implant that includes an implant body having a first surface with a
first peak, a second surface opposite the first surface, and a
cavity formed therein that extends through the first surface and
second surface. The implant body is substantially non-porous. A
load bearing member comprising a substantially porous material is
held within the cavity. The load bearing member has a first contact
surface that extends out of the cavity and is proud of a portion of
the first surface.
[0013] An advantage of the present invention is that the porous
load bearing member can bear load from anatomic structures during
implantation while providing a surface for tissue ingrowth.
[0014] Another advantage of the present invention is that an
ingrowth material can be included on the implant to provide an
additional surface for tissue ingrowth that has different ingrowth
properties than the load bearing member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention will be better understood by reference
to the following description of embodiments of the invention taken
in conjunction with the accompanying drawings, wherein:
[0016] FIG. 1 is a perspective view of an embodiment of a solid
component of a device formed according to the present
invention;
[0017] FIG. 2 is a perspective view of an embodiment of a porous
component of a device formed according to the present
invention;
[0018] FIG. 3 is a perspective view of a device created from the
solid component shown in FIG. 1 and the porous component shown in
FIG. 2;
[0019] FIG. 4 is a cross-sectional view of a single, continuous
layer with porous and solid regions;
[0020] FIG. 5 is a perspective view of an embodiment of a spinal
cage with windows;
[0021] FIG. 6 is a cross-sectional view of the spinal cage shown in
FIG. 5 taken along line 6-6;
[0022] FIG. 7 is a perspective view of an embodiment of a spinal
cage with a ledge or groove;
[0023] FIG. 8 is a cross-sectional view of the spinal cage shown in
FIG. 7 taken along line 8-8;
[0024] FIG. 9 is a perspective view of an embodiment of a spinal
cage with a two-part solid component that is assembled to contain
the porous material;
[0025] FIG. 10 is a cross-sectional view of the spinal cage shown
in FIG. 9 taken along line 10-10;
[0026] FIG. 11 is a perspective view of an embodiment of a spinal
cage with laminates perpendicular to an axis of the spinal
cage;
[0027] FIG. 12 is a perspective view of an embodiment of a spinal
cage with laminates parallel to an axis of the spinal cage;
[0028] FIG. 13 is a perspective view of an embodiment of a spinal
cage with laminates at an angle to an axis of the spinal cage;
[0029] FIG. 14 is a perspective view of an embodiment of a spinal
cage;
[0030] FIG. 15 is a perspective view of another embodiment of a
spinal cage;
[0031] FIG. 16 is a perspective view of yet another embodiment of a
spinal cage;
[0032] FIG. 17 is a perspective view of yet another embodiment of a
spinal cage;
[0033] FIG. 18 is a sectional view of an implant with features for
the delivery of therapeutic agents;
[0034] FIG. 19 is a sectional view of a tapered implant;
[0035] FIG. 20 is a sectional view of another tapered implant;
[0036] FIG. 21 is a sectional view of yet another tapered
implant;
[0037] FIG. 22 is a sectional view of yet another tapered
implant;
[0038] FIG. 23 is a sectional view of yet another tapered
implant;
[0039] FIG. 24 is a perspective view of an implant showing teeth
that mate with surrounding bone;
[0040] FIG. 25 is a side view of the implant shown in FIG. 24;
[0041] FIG. 26 is a spinal fusion device;
[0042] FIG. 27 is a perspective view of another embodiment of an
orthopaedic implant according to the present invention;
[0043] FIG. 28 is a side view of the orthopaedic implant shown in
FIG. 27;
[0044] FIG. 29 is a front view of the orthopaedic implant shown in
FIGS. 27-28;
[0045] FIG. 30 is a perspective view of yet another embodiment of
an orthopaedic implant according to the present invention;
[0046] FIG. 31 is a side view of the orthopaedic implant shown in
FIG. 30;
[0047] FIG. 32 is a perspective view of yet another embodiment of
an orthopaedic implant according to the present invention;
[0048] FIG. 33 is a front view of the orthopaedic implant shown in
FIG. 32;
[0049] FIG. 34 is a side view of the orthopaedic implant shown in
FIGS. 32-33;
[0050] FIG. 35 is a side view of the orthopaedic implant shown in
FIGS. 32-34 including an ingrowth material;
[0051] FIG. 36 is a perspective view of yet another embodiment of
an orthopaedic implant according to the present invention;
[0052] FIG. 37 is a side view of the orthopaedic implant shown in
FIG. 36; and
[0053] FIG. 38 is a side view of the orthopaedic implant shown in
FIGS. 36-37 including an ingrowth material.
[0054] The exemplifications set out herein illustrate embodiments
of the invention, and such exemplifications are not to be construed
as limiting the scope of the invention in any manner.
DETAILED DESCRIPTION OF THE INVENTION
I. Porous Spinal Devices--Laminate Designs
[0055] The present invention provides a laminate method for a
spinal implant or implant component, including manufacturing
methods for sheet creation, bonding/assembly methods, and ways of
creating tapers. Further, the present invention provides delivery
of therapeutic agents through a spinal device.
[0056] The present invention addresses these issues by providing
the design and method of manufacturing of a porous spinal fusion
device.
A. Materials
[0057] Material options for the spinal device include the
following: implantable polymers (such as PEEK, PMMA), implantable
reinforced polymers (such as carbon-fiber reinforced PEEK),
implantable metals (such as titanium, titanium alloy), and
implantable ceramics (such as hydroxyapatite, alumina). One or more
of these materials can be combined in a given device.
B. Overall Design
[0058] With regard to the overall design, the implant can include
entirely porous material or one or more porous regions and one or
more solid regions. Additionally, an entirely porous device can be
created to mate with existing solid devices (See FIGS. 1-3).
[0059] The porous region is created by stacking layers of material
with interconnecting holes/geometry (hereafter referred to as
holes).
[0060] The solid region can be formed by traditional techniques
such as injection molding or machining or by bonding solid sheets
together. The later method allows the solid and porous regions to
be created from continuous sheets (See FIG. 4).
[0061] The holes in the sheets can be created by, for example,
laser cutting, punching, etching, electrical discharge machining,
plasma etching, electroforming, electron beam machining, water jet
cutting, stamping, or machining. For polymer based materials, they
can be created as the sheets are created by, for example,
extruding, injection molding, or hot stamping.
[0062] Attachment of the sheets to each other can be achieved by
any number of ways, including the following:
[0063] 1. Heat. Heat can be generated by several ways: [0064] a.
Ultrasonic welding--use ultrasonic waves to create heat at the
interface of layers. [0065] b. Heat staking--use a heated tool to
cause melting between the layers [0066] c. Vibratory welding [0067]
d. Laser welding [0068] e. Convection--use an oven to create heat
to cause bonding [0069] f. Intermediary layer--for example, use a
material that can absorb energy waves that pass through the polymer
(for example PEEK) without causing damage. The absorbed energy will
cause localized heating. An example of such a coating is Clearweld
by Gentex.RTM. Corporation. The laser waves that Clearweld absorbs
pass through the PEEK without causing damage, allowing the layers
to be melted together without large scale damage to the PEEK.
[0070] 2. Chemical. [0071] a. Adhesives--a secondary material (such
as adhesive) can be used to bond the material. [0072] b. Solvent
bonding--a material in which the polymer or reinforced polymer is
soluble can be applied to the sheet surfaces allowing multiple
surfaces to be bonded to one another. [0073] c.
Overmolding--overmolding of the polymer or reinforced polymer can
provide a chemical bonding
[0074] 3. Mechanical. [0075] a. Overmolding--overmolding of a
polymer or reinforced polymer can create a mechanical lock between
components on a micro or macro scale (microscale--the molded
material locks with surface asperities of the existing material.
Macroscale--features such as tongue-groove connections or
undercuts). The overmolded material can be a separate component
from the layers or one layer can be overmolded onto another layer.
[0076] b. Features are provided within the layers or by a separate
component which provides a mechanical lock--e.g. A pin, snap lock
connection, dove-tail, tongue-groove, rivet, screw and/or melting
tabs to create a mechanical lock. For example, one or more rivets
can connect all layers of a porous implant together. These
connection features can be made of any implantable material
including, but not limited to, titanium, titanium alloy, PEEK,
and/or other implantable polymers. These features can also be used
as radiopaque markers as is described below. [0077] c. Some
adhesives provide a mechanical bond in addition to or instead of a
chemical bond.
[0078] 4. Combinations of any/all of the above methods.
[0079] If the porous and solid regions are created separately (as
in FIGS. 1-3), it may be desirable to bond the two together. There
are several methods of achieving this bond:
[0080] 1. Heat. Heat can be generated by several ways: [0081] a.
Ultrasonic welding--use ultrasonic waves to create heat at the
interface of layers. [0082] b. Heat staking--use a heated tool to
cause melting between the layers [0083] c. Vibratory welding [0084]
d. Laser welding [0085] e. Convection--use an oven to create heat
to cause bonding [0086] f. Intermediary layer--for example, use a
material that can absorb energy waves that pass through the polymer
(for example PEEK) without causing damage. The absorbed energy will
cause localized heating. An example of such a coating is Clearweld
by Gentex.RTM. Corporation. The laser waves that Clearweld absorbs
pass through the PEEK without causing damage, allowing the layers
to be melted together without large scale damage to the PEEK.
[0087] 2. Chemical. [0088] a. Adhesives--a secondary material (such
as adhesive) can be used to bond the material. [0089] b. Solvent
bonding--a material in which the polymer or reinforced polymer is
soluble can be applied to the sheet surfaces allowing multiple
surfaces to be bonded to one another. [0090] c.
Overmolding--overmolding of the polymer or reinforced polymer can
provide a chemical bonding
[0091] 3. Mechanical. [0092] a. Overmolding--overmolding of a
polymer or reinforced polymer can create a mechanical lock between
components on a micro or macro scale (microscale--the molded
material locks with surface asperities of the existing material.
Macroscale--features such as tongue-groove connections or
undercuts). The overmolded material can be a separate component
from the layers or one layer can be overmolded onto another layer.
[0093] b. Features are provided within the layers or by a separate
component which provides a mechanical lock--e.g. A pin, snap lock
connection, dove-tail, tongue-groove, rivet, and/or melting tabs to
create a mechanical lock. For example, the porous material can
attach to the windows that are typical in spinal cages or to a
groove or ledge is created along the interior edge of the solid
ring (see FIGS. 5-10). These connection features can be made of any
implantable material including, but not limited to, titanium,
titanium alloy, PEEK, and/or other implantable polymers. These
features can also be used as radiopaque markers as is discussed
later in this disclosure. [0094] c. Some adhesives provide a
mechanical bond in addition to or instead of a chemical bond.
[0095] 4. Combinations of any/all of the above methods.
[0096] Assembly of layer to layer or one component to another (for
example a porous component to a solid component) can be aided by
such ways as surface modifications to improve adhesive or solvent
bonding or roughened surfaces.
[0097] FIGS. 5-6 illustrate a spinal cage showing windows (a cross
section view is shown at the right). This is an example of a type
of feature onto which the porous component can be bonded.
[0098] FIGS. 7-8 illustrate a spinal cage showing a ledge or groove
(a cross section view is shown at the right). This is an example of
a type of feature onto which the porous component can be
bonded.
[0099] FIGS. 9-10 illustrate a spinal cage showing a two-part solid
component that is assembled to contain the porous material. In this
example mechanical means (screw/rivet) are used in conjunction with
an adhesive bond. Adhesive ways alone, mechanical ways alone or any
of the other manufacturing methods discussed in this disclosure are
also options.
[0100] FIGS. 11-13 illustrate a spinal cages showing laminates
perpendicular, parallel, and at an angle to the axis of the
implant.
[0101] The laminate portion of the implant can have layers oriented
in any direction. For example, the layers can be perpendicular,
parallel, or at an angle to the axis of the implant (See FIGS.
11-13). This angle need not be constant within an implant.
[0102] The overall shape of the implant can be of any typical
existing type, such as ALIF, TLIF,
C. Delivery of Therapeutic Agent.
[0103] This device can be used to deliver therapeutic agents
directly to the tissue surrounding the implant (See FIG. 18). Some
examples of situations in which this would be desired: delivery of
oncology treatments to cancerous tissue or tissue surrounding
cancerous tissue; delivery of agents (such as BMP, hydroxyapatite
slurry, and/or platelets) to encourage/enhance bone growth to
promote faster and better fusion; and delivery of analgesic agents
to reduce pain. This list is not exhaustive.
[0104] FIG. 18 illustrates a sectioned, side-view of an implant
with features for the delivery of therapeutic agents.
[0105] The implant can include a reservoir for delivery of the
therapeutic agent over an extended period of time. Openings leading
from the reservoir to the porous material allow for controlled
release of the therapeutic agents at a desired rate. The reservoir
can be refilled at any time before, during, or after the
surgery.
[0106] If immediate delivery of the therapeutic agents to the
surrounding tissue is all that is required (not extended time
release), the design need not include a reservoir. In this case,
the therapeutic agents can be directly routed from the implant
access to the porous material via channels. However, a reservoir
can be included in an immediate delivery design; the openings in
the reservoir would be sized to allow for immediate release of the
therapeutic agent rather than a slower, long-term delivery.
[0107] The access in the implant (see FIG. 18) can mate with an
insertion of a delivery tool (such as a needle) or a device (or
catheter leading to a device) to allow for remote filling of the
reservoir (such as by way of a subcutaneous port or external
pain-pump).
[0108] In order to allow and promote bone growth through the
implant from one vertebra to the other, openings run from the
superior to the inferior portion of the implant and be
appropriately sized to allow for bone ingrowth (See FIG. 18).
D. Anterior-Posterior Taper
[0109] Some implants are tapered to mate with the natural
anterior-posterior taper that exists between vertebrae. If a solid
portion exists, this taper can be created by traditional machining
and/or molding techniques. In the porous region, there are several
ways of creating this taper, including the following: [0110] a. If
the design includes a reservoir, the reservoir itself can be
tapered. The porous ingrowth layers can be of uniform thickness and
layered outside of the reservoir (as indicated in FIG. 18). [0111]
b. A wedge-shaped piece or pieces can create the taper with the
ingrowth layers stacked on the wedge(s). This is essentially the
same design as shown in FIG. 20 without the reservoir, access and
holes for the therapeutic agent delivery. To allow and promote bone
growth through the implant from one vertebra to the other, openings
run from the superior to the inferior portion of the implant and be
appropriately sized to allow for bone ingrowth (See FIG. 18).
[0112] c. Shorter layers can be stacked with larger layers to
create an overall taper as in FIG. 19. [0113] d. Layers of varying
lengths can be sacked to create a stepped taper as in FIG. 20.
[0114] e. Similar to the technique in (d), layers of varying length
can be stacked. A smooth taper can be created by using layers that
are tapered prior to stacking or the smooth taper can be created,
by such ways as machining or hot forming, after the layers are
stacked. The second of these would involve first creating a part
like that in (d), then removing material to create the smooth taper
shown in FIG. 21. [0115] f. Another way of creating a smooth
surface on a stepped taper is to have one or more outer layers
which are parallel to the taper face, as shown in FIG. 22. [0116]
g. The design in (f) does not allow for a large amount of contact
area between the outer layer of the taper and the corners of the
stepped layer. One way of providing increased contact area (which
can provide increased strength) is to taper the stepped layers as
in FIG. 21 before adding the outer layer(s) that are parallel to
the face of the taper. An example of this is shown in FIG. 23. E.
Interface with Bone
[0117] It is often desirable to have an implant-bone interface with
relative high friction. Traditionally, this is achieved by such
ways as a roughened implant surface, teeth (See FIGS. 24-25),
spikes, or hooks.
[0118] In a laminate implant, there are several options for
creating such features. These options include the following: [0119]
a. Form features prior to bonding laminate sheets: Form teeth or
other "rough" features into the outermost layers of the implant
prior to bonding them to the other sheets. These teeth can be
created by several ways: [0120] i. Form material--for example: heat
forming, cold forming. [0121] ii. Remove material--for example:
machining, laser cutting, chemical etching. [0122] iii. Add
material--attach material to create the features by, for example,
insert molding, mechanical attachment, adhesive bonding, laser
welding, solvent bonding. [0123] b. Form features after bonding
laminate sheets: Form the rough surface features on the faces of
the implant after the sheets have been bonded. These features can
be formed by the same ways as listed in (a). [0124] c. Secondary
feature (such as hooks, spikes, etc) protruding from the implant
into the bone. This feature can be attached by, for example, insert
molding, mechanical attachment, adhesive bonding, laser welding, or
solvent bonding.
[0125] FIGS. 24-25 illustrate an implant showing teeth that mate
with the surrounding bone.
F. Interface with Instruments
[0126] To aid in insertion of the implant into position in the
body, it is often necessary to attach the implant to
instrumentation. The material near the interface of the instrument
and implant can often see additional stress. In a partially or
fully laminate implant, it may be necessary to provide additional
support in the region of this interface. This can be achieved by a
number of ways, including: designing the instrument to reduce
stresses and/or strengthening the implant in the region of the
interface. For example, in the case of an instrument that contains
a male thread which mates with a female thread in the implant, the
implant can be strengthened by adding metal, solid polymer, or
reinforced polymer in the region of the female thread. In machine
design, thread inserts are frequently used to repair damaged
threads. In this case, thread inserts can be used to strengthen the
implant at the interface with the instrument(s).
G. Radiopaque Markers
[0127] When a radiolucent material, such as unfilled PEEK, is used,
it is sometimes desirable to have the ability to see some or all of
that implant on a diagnostic tool such as x-ray without the
white-out problems of solid metal. For example, the surgeon may use
such markers to determine the orientation and position of the
implant to ensure proper placement during surgery. Radiopaque
markers can provide this ability. The opacity and/or amount of
radiopaque material can be controlled so that the marker does not
prevent evaluation of the tissue near the implant by x-ray or other
diagnostic ways. Material options include, but are not limited to,
the following: [0128] a. Implantable metals (stainless steel,
titanium, or titanium alloys for example). [0129] b. Barium sulfate
filled PEEK. [0130] c. Carbon filled PEEK. [0131] d. Other polymers
with radiopaque material (such as barium sulfate or zirconium
dioxide).
[0132] Examples of the marker design include one or more of the
following: [0133] a. One or more radiopaque pins. [0134] b.
Assembly features such as rivets or pins. [0135] c. Coating a
portion of the device with a radiopaque material. Examples of
methods for creating a radiopaque coating include, but are not
limited to, the following: [0136] i. Using chemical vapor
deposition to deposit a layer of titanium onto the polymer. [0137]
ii. Using a radiopaque ink such as Radiopaque.TM. ink (developed by
CI Medical). [0138] d. One or more of the laminate layers being
radiopaque. Examples of methods to make the layer(s) radiopaque
include, but are not limited to, the following: [0139] i. Making
the layer from an implantable metal (such as tantalum, titanium,
titanium alloy, cobalt chrome, or stainless steel). [0140] ii.
Using a barium sulfate filled polymer to create the layer. [0141]
iii. Coating the layer with a radiopaque material--for example,
using chemical vapor deposition to deposit a layer of titanium onto
the surface of one or more layers. [0142] e. A slightly radiopaque
porous material. This can be achieved, for example, by using a
polymer with barium sulfate.
II. Porous Polymer Spinal Fusion Devices
[0143] The key to the success of a spinal fusion surgery is the
formation of good bone growth between the vertebrae that are being
fused. Evaluation of this bone growth is, thus, critical to
determining the progress and eventual success of the surgery.
[0144] Existing porous spinal cages are made of biocompatible
metals. Due to the density of these metals, the implants made
post-operative examination of the tissue surrounding the implant
difficult.
[0145] Several current devices are now made from solid
biocompatible polymers such as PEEK. PEEK is a relatively
radiolucent material. While this addresses the issue of radiopacity
for solid fusion devices, it is often desired to encourage more
rapid bone growth between the two vertebrae.
[0146] One solution for this problem is implants made from porous
biocompatible polymers, such as PEEK or reinforced porous PEEK.
A. Overall Design
[0147] Such implants can be entirely porous or have a mix of porous
and solid polymer. For example, a solid ring of material can
surround a porous core (See FIG. 26).
[0148] FIG. 26 illustrates a spinal fusion device with solid region
(Region 1) and porous region (Region 2)
[0149] One embodiment of the design is a porous center component
that mates with existing solid, ring-like devices. This device
could be assembled with the solid device in a manufacturing setting
or in the operating room.
[0150] If a solid region/component exists, the porous and solid
regions may need, but do not necessarily need, to be attached to
one another. Examples of methods that can be used to attach the
porous and solid material are: [0151] a. Mechanical
features--snap-fit connections, `dove-tail` types of connections.
[0152] b. Adhesive bonding. [0153] c. Solvent bonding. [0154] d.
Heat applied by, for example, laser, ultrasonic or vibratory
welding, convection heating, heat staking.
B. Material
[0154] [0155] a. Method of creating porosity [0156] i. Laminate
design--bonding sheets of material which contain holes. [0157] ii.
Foaming methods. [0158] iii. Bond `beads` of polymer--bead of any
shape can be bonded together (via, for example, heating, adhesive
bonding, or solvent bonding) to create a porous structure. [0159]
iv. Mix of polymer and dissolvable material. [0160] 1. One method
involves creating a mixture of powdered implantable material (e.g.
PEEK) and a powder (e.g. salt) that is soluble in something in
which the implantable material is not soluble (such as water,
isopropyl alcohol for the PEEK example). The mixture is then heated
to bond the implantable particles together. Pressure can also be
applied to aid in the bonding of particle to particle. Heat can be
created by convection or other ways (such as coating the powder
with a material that absorbs a given range of energy waves--such as
laser waves--and causes heating. E.g. Clearweld coating by
Gentex.RTM. Corporation). Finally, dissolve away the filler to
create the porous implantable material. This method can create net
shape parts or raw material shapes from which individual parts can
be created. [0161] 2. Another method involves mixing an implantable
polymer with a dissolvable material such as described above. The
mixture is then pelletized and then injection molded to an
intermediary or the final part shape. The filler is dissolved away
to create the porous implantable polymer. [0162] b.
Reinforcement--If improved mechanical properties are desired,
various reinforcing materials can be used. For example, carbon
fiber or barium sulfate can be used.
C. Radiopaque Markers
[0163] It is sometimes desirable to have the ability to see some of
the implant on a diagnostic tool such as an x-ray without the
white-out problems of solid metal. For example, the surgeon may use
such markers to determine the orientation and position of the
implant to ensure proper placement during surgery. Radiopaque
markers can provide this ability. The opacity and/or amount of
radiopaque material can be controlled so that the marker does not
prevent evaluation of the tissue near the implant by x-ray or other
diagnostic ways. Material options include, but are not limited to,
the following: [0164] a. Implantable metals (stainless steel,
titanium, or titanium alloys for example). [0165] b. Barium sulfate
filled PEEK. [0166] c. Carbon filled PEEK. [0167] d. Other polymers
with radiopaque material (such as barium sulfate or zirconium
dioxide).
[0168] Examples of the marker design include one or more of the
following: [0169] a. One or more radiopaque pins. [0170] b. Coating
a portion of the device with a radiopaque material. Examples of
methods for creating a radiopaque coating include, but are not
limited to, the following: [0171] i. Using chemical vapor
deposition to deposit a layer of titanium onto the polymer. [0172]
ii. Using a radiopaque ink such as Radiopaque.TM. ink (developed by
CI Medical). [0173] c. A slightly radiopaque porous material. This
can be achieved, for example, by using a polymer with barium
sulfate.
[0174] Referring now to FIGS. 27-29, an embodiment of an
orthopaedic implant 100 according to the present invention is shown
that includes an implant body 102 formed from a substantially
non-porous material having a first surface 104 and a second surface
106 opposite the first surface 104. As used herein, "substantially
non-porous" indicates a porosity of 5% or less, so that the implant
body 102 is mostly solid. The implant body 102 can be formed from a
variety of different materials that are biocompatible and commonly
used to form orthopaedic implants, including polyether ether ketone
(PEEK), other polyaryl ether ketones (PAEKs), titanium, stainless
steel, cobalt chrome, ultra-high molecular weight polyethylene
(UHMWPE), or any previously described material. It should be
appreciated that these materials are exemplary only and other
biocompatible materials could be used to form the implant body. As
shown in FIGS. 27-29, the implant body 102 is formed in the shape
of a cervical cage for spinal applications, but other shapes can
also be used, as shown further herein. The first surface 104 and
second surface 106 can be curved, as shown, or can be formed as
planar surfaces that are substantially flat. Alternatively, one of
the surfaces 104, 106 can be formed as a surface with one or more
curvatures while the other surface is planar.
[0175] A cavity 108 is formed in the implant body 102 extending
through the first surface 104 and second surface 106 to form a
continuous cavity 108 through the implant body 102. The cavity 108
has a first cavity entrance 110 formed through the first surface
104 and a second cavity entrance 112 (shown in FIG. 28) formed
through the second surface 106. One or both of the cavity entrances
110, 112 can be concentrically formed through their respective
surface 104, 106 so that the cavity entrances 110, 112 have a
perimeter shape that approximately matches a perimeter shape of
their respective surface 104, 106, with the cavity entrances 110,
112 having a smaller perimeter than their respective surfaces 104,
106. The cavity 108 can be formed to have a constant or varying
shape throughout.
[0176] A load bearing member 114 comprising a substantially porous
material having a first contact surface 116 is held within the
cavity 108 that is formed within the implant body 102. As used
herein, "substantially porous" indicates a porosity of at least
20%, but can be significantly higher. For example, the load bearing
member 114 can have a total volume, that is the entire volume
occupied by the load bearing member 114, of which 60% or more is
defined by pores 117 formed in the load bearing member 114. In
other words, 40% of the total volume of the load bearing member 114
can be occupied by structural material forming the load bearing
member 114 while 60% of the total volume is occupied by empty
spaced defined by the pores 117, in aggregate. If an extremely
porous material is used to form the load bearing member 114, the
pores 117, in aggregate, can occupy 80% or more of the total volume
of the load bearing member 114. If desired, one or more therapeutic
agents can be held within some or all of the pores 117 for elution
into surrounding anatomic features after implantation of the
orthopaedic implant 100 to increase the efficacy of the surgical
procedure. A non-exhaustive list of possible therapeutic agents
that can be provided in the pores 117 includes various growth
factors, bone morphogenetic factors, bone morphogenetic proteins,
anti-microbial agents, anti-inflammatories, anti-coagulants,
painkillers, cytotoxic substances, stem cells, and any other
substance, known or unknown, that is desirable to elute from the
orthopaedic implant 100 following implantation. The material(s)
used to form the load bearing member 114 should, like the implant
body 102, be biocompatible so that the orthopaedic implant 100 is
suitable for implantation at an anatomical site within a patient.
It is also useful if the load bearing member 114 is formed from one
or more materials that are non-resorbable, i.e., the material of
the load bearing member 114 can maintain at least 90% of its
original mass after being implanted in a living patient for at
least a year. Examples of such materials are PEEK, tantalum, and
titanium, but other porous materials are also contemplated as being
used. The load bearing member 114 can comprise either a synthetic
material, such as those previously described, or one or more
naturally derived materials, such as a bone graft. The naturally
derived material can also be, for example, cells or tissues
harvested from the patient or a different organism, scaffolds
created using collagen or other biomaterials, etc. It is useful,
but not required, for the load bearing member 114 to substantially
fill the cavity 108 so that at least 90% of the empty space in the
implant body 102 defined by the cavity 108 is filled by the bearing
member 114. Such filling of the cavity 108 by the load bearing
member 114 makes it easier to hold the load bearing member 114
within the cavity 108 during implantation.
[0177] The first surface 104 defines a first peak 118, which is a
point on the first surface 104 that has a maximum height, relative
to a ground surface, when the second surface 106 of the implant
body 102 is laid on the ground surface. The first peak 118 of
implant body 102 is best shown in FIG. 28, where it can be seen
that the first peak 118 is adjacent to the first cavity entrance
110. With further reference to FIG. 28, it can be seen that the
first contact surface 116 of the load bearing member 114 extends
out of the cavity 108 past the first cavity entrance 110 so that
the first contact surface 116 extends past the first peak 118,
i.e., the first contact surface 116 is proud of the first surface
104. In this sense, the first contact surface 116 defines a
thickness Ti that extends past and projects from the first surface
104, which can be either constant or varying throughout the first
contact surface 116. By extending the first contact surface 116
past the first peak 118 of the first surface 104, the first contact
surface 116 can be placed in contact with an anatomic structure,
such as a vertebrae, during implantation while isolating the first
surface 104 from contact with the anatomic structure. Once
implanted, the porous load bearing member 114 can then bear load
from the anatomic structure while allowing for ingrowth of tissue
into the load bearing member 114 through the pores 117.
[0178] Due to the varying shapes of anatomic structures and desired
load bearing characteristics, the first contact surface 116 can be
a curved surface or a planar surface. The relative sizing between
the first surface 104 and the first contact surface 116 can also be
adjusted, as desired, to balance the load bearing characteristics
of the load bearing member 114. As can be seen, the first contact
surface 116 defines a contact surface area and the first surface
104 defines a first surface area, with the contact surface area and
first surface area together defining a top surface area of the
orthopaedic implant 100. The relative percentage of the top surface
area that the contact surface area makes up can be altered to give
varying amount of contact surface for anatomic structures during
implantation. It is contemplated that the contact surface area can
be 40 to 90% of the total surface area when a large contact surface
116 is desired, or less than 40% of the total surface area when a
smaller contact surface 116 is desired. It should be understood
that the term "top surface area" is used for convenience of
description only and not to limit the scope of the present
invention.
[0179] Optionally, the load bearing member 114 can have a second
contact surface 120 extending out of the cavity 108 past the second
cavity entrance 112 so that it extends past a second peak 122 of
the second surface 106 of the implant body 102. The second peak 122
of the second surface 106 is analogous to the first peak 118 of the
first surface 104, with the key difference being that the second
peak 122 defines a maximum height of the second surface 106
relative to a ground surface when the first surface 104 is laid on
the ground surface. The second contact surface 120 can be
configured and altered similarly to the first contact surface 116
so that the second contact surface 120 can be in contact with an
anatomic structure following implantation. The second contact
surface 120 can be a mirror image of the first contact surface 116
or a different configuration, depending on the desired load bearing
characteristics of the load bearing member 114 caused by loads
bearing on the first and second contact surfaces 116, 120 from
surrounding anatomic structures. It can be useful if the pores 117
of the load bearing member 114 interconnect from the first contact
surface 116 to the second contact surface 120 so that a travel path
through the entirety of the load bearing member 114 can be formed
through interconnected pores 117 formed therein.
[0180] To assist in implanting the orthopaedic implant 100, an
opening 124 can be formed through another surface 126 of the
implant body 102 to the cavity 108. The opening 124 can be any size
or shape that allows for an insertion tool (not shown) to be placed
within the opening 124 to help steady and position the orthopaedic
implant 100 during implantation. The load bearing member 114 can
partially extend into the opening 124, another material can be held
in the opening 124, or the opening 124 can provide a clear path to
the load bearing member 114 held in the cavity 108. In a similar
manner, one or more protrusions 128 can be placed adjacent to the
opening 124 that are shaped to interact with the insertion tool and
provide a more stable connection between the orthopaedic implant
100 and the insertion tool. The opening 124 and protrusion(s) 128
can also be configured so that a removal tool (not shown), rather
than an insertion tool, can interact with the opening 124 and
protrusion(s) 128 to remove the orthopaedic implant 100 from a
patient following implantation, if necessary.
[0181] Referring now to FIGS. 30-31, another embodiment of an
orthopaedic implant 200 is shown that is configured similarly to
orthopaedic implant 100 previously described. For brevity of
description, all features of orthopaedic implant 200 that are
analogous to features of orthopaedic implant 100 are numbered
similarly but raised by 100. As can be seen, the first surface 204
of the implant body 202 is covered by an ingrowth material 230,
shown as a porous endplate. The ingrowth material 230 can cover all
or part of the first surface 204 to encourage ingrowth of
surrounding tissues into the ingrowth material 230 following
implantation and provide good integration of the orthopaedic
implant 200. The ingrowth material 230 can be formed of any
material that encourages ingrowth of a desired body tissue into the
ingrowth material 230. A non-exhaustive list of contemplated
materials includes porous titanium, tantalum, hydroxyapatite,
tricalcium phosphate, PEEK, PAEK, polymethyl methacrylate (PMMA),
polylactic acid (PLA), and polyglycolic acid (PGA), but it should
be understood that many other types of materials can be used as the
ingrowth material 230. Since the load bearing member 214 will
initially bear the brunt of the load from surrounding anatomic
structures, the ingrowth material 230 can be formed of a lower
strength material, with a higher porosity than the load bearing
member 214, or both. For example, the load bearing member 214 can
be formed of a reinforced PEEK material that has a porosity of 60%
and the ingrowth material 230 can be formed of a PEEK material that
has a porosity of 80%. This allows for orthopaedic implant 200 to
have a higher strength material of the load bearing member 214
initially bear the brunt of the load from surrounding anatomic
structures while a higher porosity material of the ingrowth
material 230 allows for better tissue ingrowth to fixate the
orthopaedic implant 200.
[0182] As shown in FIG. 31, the ingrowth material 230 has an
ingrowth peak 234, which is the highest point of the ingrowth
material 230 relative to a ground surface when the implant body 202
rests its second surface 206 on the ground surface. The first
contact surface 216 of the load bearing member 214 extends out of
the cavity 208 formed in the implant body 202 past the ingrowth
peak 234, so that the first contact surface 216 can bear load from
an anatomic structure following implantation and isolate the
ingrowth material 230 from initially bearing load from the anatomic
structure. The orthopaedic implant 200 can have a second ingrowth
material 236 covering all or part of the second surface 206 of the
implant body 202 and the load bearing member 214 can have a second
contact surface 220 extending past the second ingrowth material 236
similarly to how the first ingrowth material 230 extends past the
ingrowth peak 234 of the ingrowth material 230. In this sense, the
ingrowth materials 230, 236 have surfaces that are analogous to the
first and second surfaces 104, 106 of orthopaedic implant 100 and
which the load bearing member 214 extends past.
[0183] Referring now to FIGS. 32-34, another embodiment of an
orthopaedic implant 300 according to the present invention is shown
that includes an implant body 302 configured to be used as a lumbar
cage. The implant body 302 is comprised of a substantially
non-porous material and has a first surface 304; a second surface
306 opposite the first surface 304; a first cavity 308 formed
through the first surface 304 and second surface 306; and a second
cavity 310 formed through the first surface 304 and second surface
306. As can be seen, the implant body 302 has a planar portion 312
that is flat and a curved portion 314 that has a sloped curvature.
The cavities 308, 310 can be formed through the first and second
surface 304, 306 all or partially within either the planar portion
312 or curved portion 314. A first load bearing member 316 is held
within the first cavity 308 and a second load bearing member 318 is
held within the second cavity 310. The first load bearing member
316 has a first contact surface 320 and the second load bearing
member 318 has a third contact surface 322 that each extend out of
their respective cavity 308, 310 past the plane of the planar
portion 312, so that the contact surfaces 320, 322 can bear load
from surrounding anatomic features following implantation. The load
bearing members 316, 318 and their contact surfaces 320, 322 can be
configured similarly to previously described load bearing members
114, 214, and even though the load bearing members 316, 318 are
shown as having different sizes and total volumes, their size and
total volume could be equal. The contact surfaces 320, 322 each
define a respective thickness T2, T3 relative to the planar portion
312 of the first surface 304. The thicknesses T2, T3 of the contact
surfaces 320, 322 can be equal to each other or could be different
to provide different load bearing characteristics. For example, it
may be desirable to provide load bearing member 316 with a thicker
contact surface 320 than the contact surface 322 of load bearing
member 318 due to the larger overall volume of load bearing member
316, in which case T2 would be greater than T3. It is also
contemplated that the load bearing members 316 and 318 can be
formed of different materials, have differing porosities, or be
otherwise configured differently from one another to produce a
desired healing effect.
[0184] Referring now to FIG. 35, the orthopaedic implant 300 shown
in FIGS. 32-34 is shown with ingrowth material 324 covering the
first and second surfaces 304, 306 of the implant body 302. The
ingrowth material 324 can be configured in an analogous manner to
previously described ingrowth material 230.
[0185] Referring now to FIGS. 36-37, another embodiment of an
orthopaedic implant 400 according to the present invention is
shown. The orthopaedic implant 400 includes an implant body 402,
configured as an anterior lumbar interbody fusion cage, comprising
a substantially non-porous material having a first surface 404, a
second surface 406 opposite the first surface 404, and a cavity 408
that extends through the first surface 404 and second surface 406.
As can be seen, the first surface 404 is a sloped planar surface
that slopes downward from a front of the implant body 402 toward a
back of the implant body 402. It should be appreciated that the
slope of the first surface 404 can be adjusted, as desired, to
provide a variety of shapes for the implant body 402 that are
suitable for different surgical procedures.
[0186] A load bearing member 410 comprising a substantially porous
material is held within the cavity 408. The load bearing member 410
has a first contact surface 412 that extends out of the cavity 408
and is proud of a portion of the first surface 404 to which the
first contact surface 412 is immediately adjacent. Put another way,
the first contact surface 412 outwardly projects from the cavity
408 so that it will contact surrounding anatomic features when the
orthopaedic implant 400 is implanted and isolate portions of the
first surface 404 immediately adjacent to the cavity 408 from
initially bearing load from the surrounding anatomic features.
Since the first surface 404 is sloped, the first contact surface
412 does not necessarily extend past a peak of the first surface
404, as previously described first contact surfaces do. However, in
all other aspects, load bearing member 410 and first contact
surface 412 can be configured similarly to previously described
load bearing members and contact surfaces.
[0187] Referring now to FIG. 38, the orthopaedic implant 400 shown
in FIGS. 36-37 is shown with an ingrowth material 414 covering the
first surface 404 of the implant body 402. The ingrowth material
414 can be configured similarly to previously described ingrowth
materials. As can be seen, the load bearing member 410 is proud of
a portion of the ingrowth material 414 similarly to how the load
bearing member 410 shown in FIGS. 36-37 is proud of a portion of
the first surface 404.
[0188] While this invention has been described with respect to at
least one embodiment, the present invention can be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains and which fall within the limits of
the appended claims.
* * * * *