U.S. patent application number 15/721998 was filed with the patent office on 2018-01-25 for rapid manufacturing of porous metal prostheses.
The applicant listed for this patent is Zimmer, Inc.. Invention is credited to Adam M. Griner, Jia Li.
Application Number | 20180021136 15/721998 |
Document ID | / |
Family ID | 46275996 |
Filed Date | 2018-01-25 |
United States Patent
Application |
20180021136 |
Kind Code |
A1 |
Li; Jia ; et al. |
January 25, 2018 |
RAPID MANUFACTURING OF POROUS METAL PROSTHESES
Abstract
An orthopaedic prosthesis and a method for rapidly manufacturing
the same are provided. The orthopaedic prosthesis includes a solid
bearing layer, a porous bone-ingrowth layer, and an interdigitating
layer therebetween. A laser sintering technique is performed to
manufacture the orthopaedic prosthesis.
Inventors: |
Li; Jia; (Fort Wayne,
IN) ; Griner; Adam M.; (Columbia City, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zimmer, Inc. |
Warsaw |
IN |
US |
|
|
Family ID: |
46275996 |
Appl. No.: |
15/721998 |
Filed: |
October 2, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14630820 |
Feb 25, 2015 |
9775711 |
|
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15721998 |
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13486310 |
Jun 1, 2012 |
8992825 |
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14630820 |
|
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61507151 |
Jul 13, 2011 |
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Current U.S.
Class: |
427/2.26 ;
419/2 |
Current CPC
Class: |
A61L 27/04 20130101;
B22F 3/105 20130101; B33Y 80/00 20141201; A61F 2/28 20130101; B22F
3/11 20130101; B05D 3/0254 20130101; A61L 27/56 20130101; B05D 1/12
20130101; B05D 5/00 20130101 |
International
Class: |
A61F 2/28 20060101
A61F002/28; B05D 5/00 20060101 B05D005/00; B05D 3/02 20060101
B05D003/02; A61L 27/56 20060101 A61L027/56; B05D 1/12 20060101
B05D001/12 |
Claims
1. A method of rapidly manufacturing an orthopaedic prosthesis
having a porous substrate, the porous substrate including an outer
surface and a plurality of ligaments that define pores beneath the
outer surface, the method comprising the steps of: depositing a
plurality of metal powder particles onto the outer surface of the
porous substrate; allowing at least a first portion of the
plurality of metal powder particles to enter the pores beneath the
outer surface of the porous substrate, the first portion of the
plurality of metal powder particles being sized to fit within the
pores of the porous substrate; and applying an energy source to the
first portion of the plurality of metal powder particles to form
solid metal, the solid metal interdigitating into the pores of the
porous substrate.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from U.S. Provisional
Patent Application Ser. No. 61/507,151, filed Jul. 13, 2011, the
disclosure of which is hereby expressly incorporated by reference
herein in its entirety.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates to porous metal prostheses.
More particularly, the present disclosure relates to rapid
manufacturing of porous metal prostheses.
BACKGROUND OF THE DISCLOSURE
[0003] Orthopaedic prostheses are commonly used to replace at least
a portion of a patient's bone following traumatic injury or
deterioration due to aging, illness, or disease, for example.
[0004] When the orthopaedic prosthesis is implanted into a joint,
the orthopaedic prosthesis may be configured to articulate with an
adjacent orthopaedic component. For example, when the orthopaedic
prosthesis is implanted into the patient's hip joint, the
orthopaedic prosthesis may be socket-shaped to receive and
articulate with an adjacent femoral component.
[0005] The orthopaedic prosthesis may be at least partially porous
to promote ingrowth of the patient's surrounding bone and/or soft
tissue, which may enhance the fixation between the orthopaedic
prosthesis and the patient's surrounding bone and/or soft tissue.
Typically, the porous portion of the orthopaedic prosthesis is
attached to a solid component, such as by diffusion bonding.
Diffusion bonding, however, requires a significant amount of time
to complete and subjects the orthopaedic prosthesis to high
temperatures.
SUMMARY
[0006] The present disclosure provides an orthopaedic prosthesis
having a solid bearing layer, a porous bone-ingrowth layer, and an
interdigitating layer therebetween. The present disclosure also
provides a method for rapidly manufacturing the orthopaedic
prosthesis, such as by performing a laser sintering process.
[0007] According to an embodiment of the present disclosure, a
method is provided for rapidly manufacturing an orthopaedic
prosthesis. The orthopaedic prosthesis has a porous substrate, the
porous substrate including an outer surface and a plurality of
ligaments that define pores beneath the outer surface. The method
includes the steps of: depositing a plurality of metal powder
particles onto the outer surface of the porous substrate; allowing
at least a first portion of the plurality of metal powder particles
to enter the pores beneath the outer surface of the porous
substrate, the first portion of the plurality of metal powder
particles being sized to fit within the pores of the porous
substrate; and applying an energy source to the first portion of
the plurality of metal powder particles to form solid metal, the
solid metal interdigitating into the pores of the porous
substrate.
[0008] According to another embodiment of the present disclosure, a
method is provided for rapidly manufacturing an orthopaedic
prosthesis. The orthopaedic prosthesis has a solid metal component
and a porous metal component, the porous metal component including
a plurality of ligaments that define pores. The method includes the
steps of: depositing a plurality of metal powder particles into the
pores of the porous metal component; and directing an energy source
into the pores of the porous metal component to convert the
plurality of metal powder particles in the pores to solid metal in
the pores, the solid metal in the pores coupling the solid metal
component to the porous metal component.
[0009] According to yet another embodiment of the present
disclosure, an orthopaedic prosthesis is provided including a solid
metal layer having a first thickness, a porous metal layer having a
second thickness that is less than or equal to the first thickness,
the porous metal layer including a plurality of ligaments that
define pores, and an interdigitating layer having a third
thickness, the interdigitating layer including a plurality of
ligaments that define pores, the pores of the interdigitating layer
being substantially filled with solid metal, the interdigitating
layer extending between the solid metal layer and the porous metal
layer to couple the solid metal layer to the porous metal
layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The above-mentioned and other features and advantages of
this disclosure, and the manner of attaining them, will become more
apparent and the invention itself will be better understood by
reference to the following description of embodiments of the
invention taken in conjunction with the accompanying drawings,
wherein:
[0011] FIG. 1 is a flow chart of an exemplary method for rapidly
manufacturing an orthopaedic prosthesis;
[0012] FIG. 2 is a schematic diagram of a porous substrate located
within a build chamber;
[0013] FIG. 3 is another schematic diagram showing a first layer of
metal powder deposited into the porous substrate of FIG. 2;
[0014] FIG. 4 is another schematic diagram showing a laser
selectively converting the first layer of metal powder of FIG. 3 to
solid metal;
[0015] FIG. 5 is another schematic diagram showing a second layer
of metal powder deposited into the porous substrate of FIG. 4;
[0016] FIG. 6 is another schematic diagram showing the laser
selectively converting the second layer of metal powder of FIG. 5
to solid metal;
[0017] FIG. 7 is another schematic diagram showing a third layer of
metal powder deposited into and atop the porous substrate of FIG.
6;
[0018] FIG. 8 is another schematic diagram showing the laser
selectively converting the third layer of metal powder of FIG. 7 to
solid metal;
[0019] FIGS. 9-11 are schematic diagrams similar to FIG. 8, further
showing the laser selectively converting additional layers of metal
powder to solid metal to produce an orthopaedic prosthesis;
[0020] FIG. 12 is a schematic diagram of the orthopaedic prosthesis
of FIG. 11, further including an exploded polymeric liner, and
[0021] FIG. 13 is a schematic diagram of another, patient-specific
orthopaedic prosthesis shown implanted in a patient's bone.
[0022] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate exemplary embodiments of the invention and such
exemplifications are not to be construed as limiting the scope of
the invention in any manner.
DETAILED DESCRIPTION
[0023] FIG. 1 provides an exemplary method 100 for designing and
manufacturing an orthopaedic prosthesis. Method 100 is exemplified
with reference to FIGS. 2-7.
[0024] Beginning at step 102 of method 100 (FIG. 1), a porous
substrate 200 is provided having a large plurality of struts or
ligaments 202 that define open spaces or pores 204 therebetween, as
shown in FIG. 2. Ligaments 202 may be constructed, at least in
part, of a first biocompatible metal, such as tantalum, a tantalum
alloy, niobium, a niobium alloy, or another suitable metal, for
example. In an exemplary porous substrate 200, pores 204 between
ligaments 202 form a matrix of continuous channels having no dead
ends, such that growth of cancellous bone and/or soft tissue
through porous substrate 200 is uninhibited. Thus, porous substrate
200 may provide a matrix into which cancellous bone and/or soft
tissue may grow to provide fixation of porous substrate 200 to the
patient's bone.
[0025] According to an exemplary embodiment of the present
disclosure, porous substrate 200 is a highly porous biomaterial
having a porosity as low as 55%, 65%, or 75% or as high as 80%,
85%, or 90%. An example of such a material is produced using
Trabecular Metal.TM. Technology generally available from Zimmer,
Inc., of Warsaw, Ind. Trabecular Metal.TM. is a trademark of
Zimmer, Inc. Porous substrate 200 may be formed from a reticulated
vitreous carbon foam substrate which is infiltrated and coated with
the above-described first biocompatible metal (e.g., tantalum) by a
chemical vapor deposition ("CVD") process in the manner disclosed
in detail in U.S. Pat. No. 5,282,861 to Kaplan, entitled "Open Cell
Tantalum Structures for Cancellous Bone Implants and Cell and
Tissue Receptors," filed Mar. 11, 1992, the entire disclosure of
which is expressly incorporated herein by reference. By performing
this CVD process, each ligament 202 of porous substrate 200
includes a carbon core covered by a thin film of the first
biocompatible metal (e.g., tantalum). It is also within the scope
of the present disclosure that porous substrate 200 may be in the
form of a fiber metal pad, for example, the ligaments of the fiber
metal pad being constructed entirely or substantially entirely of
the first biocompatible metal.
[0026] Porous substrate 200 may be fabricated to virtually any
desired porosity and pore size in order to selectively tailor
porous substrate 200 for a particular application, as discussed in
the above-incorporated U.S. Pat. No. 5,282,861. In an exemplary
embodiment, porous substrate 200 has an average pore size between
100 micrometers and 1,000 micrometers, and more specifically about
500 micrometers.
[0027] During the providing step 102 of method 100 (FIG. 1), porous
substrate 200 may be in a desired shape and size that is suitable
for implantation in a patient's body. For example, the illustrative
porous substrate 200 of FIG. 2 is provided in a hollow
hemispherical shape and in a size that is suitable for implantation
as an acetabular shell in a patient's hip joint. However, it is
also within the scope of the present disclosure that porous
substrate 200 may require subsequent shaping or machining after the
providing step 102 of method 100 (FIG. 1) and before being
implanted in the patient's body. Although the illustrative porous
substrate 200 of FIG. 2 is shaped and sized for use as an
acetabular shell in the patient's hip joint, it is also within the
scope of the present disclosure that the porous substrate may be
shaped and sized for use as a femoral component, a tibial
component, a humeral component, a spinal component, a dental
component, or another orthopaedic component, for example.
[0028] Porous substrate 200 includes a first, bone-engaging surface
206 that interacts with the patient's bone. In the illustrated
embodiment of FIG. 2, the bone-engaging surface 206 of porous
substrate 200 is a regular, stock surface that is shaped to
interact with a prepared (e.g., reamed, cut, etc.) bone surface of
a patient. In the illustrated embodiment of FIG. 13, on the other
hand, the bone-engaging surface 206' of porous substrate 200' is a
patient-specific surface that is shaped as substantially a negative
of the particular patient's bone surface S to conform to the
particular patient's bone surface S, even without preparing (e.g.,
reaming, cutting, etc.) the patient's bone B. The patient-specific
bone-engaging surface 206' may be designed to be highly irregular,
arbitrary, non-parametric, or biologically complex in shape to fill
a void or defect in the particular patient's bone B and to
accommodate the surrounding anatomy of the particular patient. An
exemplary method of manufacturing such a patient-specific component
is described in U.S. patent application Ser. No. 13/464,069 to Li
et al., entitled "Patient-Specific Manufacturing of Porous Metal
Prostheses," filed May 4, 2012, the entire disclosure of which is
expressly incorporated herein by reference.
[0029] Porous substrate 200 also includes a second, solid-receiving
surface 208. In the illustrated embodiment of FIG. 2,
solid-receiving surface 208 is concave in shape and opposes
bone-engaging surface 206 of porous substrate 200.
[0030] Continuing to step 104 of method 100 (FIG. 1), porous
substrate 200 is placed inside a build chamber 300, as shown in
FIG. 2. Build chamber 300 may be evacuated and flushed with an
inert gas (e.g., argon) to avoid oxidation. Build chamber 300 may
also be heated to improve the efficiency of the remaining process
steps.
[0031] Next, in step 106 of method 100 (FIG. 1), a first layer of
metal powder 302 is deposited onto porous substrate 200 in build
chamber 300, as shown in FIG. 3. More specifically, the first layer
of metal powder 302 is deposited onto solid-receiving surface 208
of porous substrate 200. Additionally, the first layer of metal
powder 302 may be deposited around porous substrate 200 to support
and stabilize porous substrate 200 in build chamber 300. In an
exemplary embodiment, the first layer of metal powder 302, and each
subsequent layer, is about 20 micrometers to about 30 micrometers
thick. After depositing each new layer of metal powder 302 into
build chamber 300, the newly deposited layer may be leveled by
rolling a roller (not shown) across build chamber 300, by vibrating
build chamber 300, or by another suitable leveling technique.
[0032] According to an exemplary embodiment of the present
disclosure, metal powder 302 comprises a second biocompatible metal
that differs from the first biocompatible metal of porous substrate
200. For example, if ligaments 202 of porous substrate 200 comprise
or are coated with tantalum, particles 304 of metal powder 302 may
comprise titanium or a titanium alloy (e.g., Ti-6Al-4V).
[0033] According to another exemplary embodiment of the present
disclosure, particles 304 of metal powder 302 are sized smaller
than pores 204 of porous substrate 200. Particles 304 of metal
powder 302 may be less than about 10% the size of pores 204 of
porous substrate 200. More specifically, particles 304 of metal
powder 302 may be as little as about 1%, about 2%, or about 3% the
size of pores 204 of porous substrate 200 and as much as about 4%,
about 5%, or about 6% the size of pores 204 of porous substrate
200, or within a range defined between any pair of the foregoing
values. For example, if pores 204 of porous substrate 200 are about
500 micrometers in size, each particle 304 of metal powder 302 may
be as small as about 5 micrometers, 10 micrometers, or 15
micrometers in size and as large as about 20 micrometers, 25
micrometers, or 30 micrometers in size. In this embodiment, a large
number of particles 304 may fall into pores 204 of porous substrate
200, especially pores 204 that are exposed along solid-receiving
surface 208 of porous substrate 200, as shown in FIG. 3. The
above-described leveling techniques may also encourage particles
304 to fall into pores 204 of porous substrate 200.
[0034] After the depositing step 106 of method 100, select areas of
metal powder 302 are exposed to an energy source during step 108 of
method 100 (FIG. 1). The applied energy source causes localized
sintering or melting of particles 304 of metal powder 302, which
converts select areas of metal powder 302 to solid metal 306. Each
newly-formed region of solid metal 306 may bond to a
previously-formed region of solid metal 306 and to porous substrate
200, as shown in FIG. 4. In this manner, solid metal 306 is
selectively and rapidly formed upon porous substrate 200 while
simultaneously bonding solid metal 306 to porous substrate 200.
[0035] In an exemplary embodiment, the applying step 108 of method
100 (FIG. 1) involves a direct metal laser sintering (DMLS)
process, where the energy source is a focused, high-powered laser
400 (e.g., a ytterbium fiber optic laser). The DMLS process may
also be referred to as a selective laser sintering (SLS) process or
a selective laser melting (SLM) process. Suitable DMLS systems are
commercially available from 3D Systems, Inc., of Rock Hill,
S.C.
[0036] Laser 400 may be controlled using a suitable computer
processor having, for example, computer-aided design (CAD) software
and/or computer-aided manufacturing (CAM) software installed
thereon. Such software can be used to rapidly create computer
numerical control (CNC) code that will control each individual pass
of laser 400 across build chamber 300. For example, as each layer
of metal powder 302 is deposited into build chamber 300 (i.e.,
along the z-axis), the CNC code may direct laser 400 side-to-side
across build chamber 300 (i.e., along the y-axis) and
back-and-forth across build chamber 300 (i.e., along the x-axis).
To convert select areas of metal powder 302 to solid metal 306,
laser 400 may be activated at select xy-coordinates. To leave other
areas of metal powder 302 as is, without forming solid metal 306,
laser 400 may be deactivated at other xy-coordinates or may avoid
traveling to those xy-coordinates altogether.
[0037] As shown by comparing FIGS. 3 and 4, even particles 304 of
metal powder 302 that settled into pores 204 of porous substrate
200 during the depositing step 106 of method 100 (FIG. 1) may be
converted to solid metal 306 during the applying step 108 of method
100 (FIG. 1). According to an exemplary embodiment of the present
disclosure, the second biocompatible metal of particles 304 of
metal powder 302 has a lower melting point than the first
biocompatible metal of ligaments 202 of porous substrate 200. For
example, if ligaments 202 of porous substrate 200 comprise or are
coated with tantalum, which has a melting point above 3,000.degree.
C., particles 304 of metal powder 302 may comprise titanium or a
titanium alloy (e.g., Ti-6Al-4V), which have melting points below
1,700.degree. C. In this embodiment, even when laser 400 passes
over and is absorbed by porous substrate 200, as shown in FIG. 4,
the thermally-stable ligaments 202 of porous substrate 200 remain
substantially intact without sintering or melting. However, when
laser 400 passes over and is absorbed by particles 304 of metal
powder 302, particles 304 may sinter or melt to form solid metal
306. If the melting points between the first and second
biocompatible metals are sufficiently different, solid metal 306
within each pore 204 of porous substrate 200 may be able to
maintain substantially the same elemental content as metal powder
302, without incorporating material from the thermally-stable
ligaments 202 of porous substrate 200.
[0038] As shown in FIGS. 5-11, the depositing step 106 and the
applying step 108 of method 100 (FIG. 1) are repeated until solid
metal 306 reaches a final, desired shape. As more metal powder 302
is deposited atop the previously-formed regions of solid metal 306,
particles 304 of metal powder 302 begin to substantially fill the
exposed pores 204 of porous substrate 200, as shown in FIG. 5. As
even more metal powder 302 is deposited atop the previously-formed
regions of solid metal 306, particles 304 of metal powder 302 begin
to accumulate atop solid-receiving surface 208 of porous substrate
200, as shown in FIGS. 7-11. After each new layer of metal powder
302 is deposited, select areas of the newly-deposited layer are
exposed to laser 400, converting more metal powder 302 to solid
metal 306.
[0039] Together, porous substrate 200 and solid metal 306 form
orthopaedic prosthesis 500 that is suitable for implantation in a
patient's body. For example, the illustrative orthopaedic
prosthesis 500 of FIG. 12 is suitable for implantation as an
acetabular cup in a patient's hip joint. Although the illustrative
orthopaedic prosthesis 500 of FIG. 12 is suitable for implantation
as an acetabular cup in the patient's hip joint, it is also within
the scope of the present disclosure that the orthopaedic prosthesis
may be configured for implantation in a patient's femur, tibia,
humerus, spine, or mouth, for example.
[0040] Returning to FIG. 6, porous substrate 200 and solid metal
306 cooperate to define an interdigitating layer L.sub.1 beneath
the solid-receiving surface 208 of porous substrate 200. Within the
interdigitating layer L.sub.1, solid metal 306 metallurgically
and/or mechanically interacts with ligaments 202 of porous
substrate 200 to create a strong attachment between solid metal 306
and porous substrate 200. The interdigitating layer L.sub.1 may
have a thickness of approximately 250 micrometers or more, 500
micrometers or more, 1,000 micrometers (1 millimeter) or more, or
1,500 micrometers (1.5 millimeters) or more, for example. Solid
metal 306 in the interdigitating layer L.sub.1 may be formed from
particles 304 of metal powder 302 that settled into pores 204 of
porous substrate 200 before exposure to laser 400, as shown in
FIGS. 3-6. Additionally, solid metal 306 in the interdigitating
layer L.sub.1 may be formed from particles 304 of metal powder 302
that settled atop solid-receiving surface 208 of porous substrate
200 before exposure to laser 400, but that later settled into pores
204 of porous substrate 200 upon exposure to laser 400. Depending
on the size of pores 204, the size of particles 304, and/or the
degree to which particles 304 are heated and rendered flowable,
solid metal 306 may substantially or completely fill pores 204 in
the interdigitating layer L.sub.1 of porous substrate 200.
[0041] In addition to the above-described interdigitating layer
L.sub.1, orthopaedic prosthesis 500 further includes a solid
bearing layer L.sub.2 and a porous bone-ingrowth layer L.sub.3, as
shown in FIG. 12. Solid metal 306 extends beyond porous substrate
200 and the interdigitating layer L.sub.1 to form the solid bearing
layer L.sub.2. The solid bearing layer L.sub.2 may have a thickness
of approximately 0.5 inch or more, 1.0 inch or more, 1.5 inches or
more, or 2.0 inches or more, for example. Porous substrate 200
extends beyond solid metal 306 and the interdigitating layer
L.sub.1 to define the porous bone-ingrowth layer L.sub.3.
[0042] An exemplary orthopaedic prosthesis 500 is predominantly
solid, not porous, by weight and/or volume. In one embodiment, the
thickness of the porous bone-ingrowth layer L.sub.3 is less than or
equal to the thickness of the solid bearing layer L.sub.2 to arrive
at orthopaedic prosthesis 500 that is predominantly solid. In this
exemplary embodiment, the solid bearing layer L.sub.2 of
orthopaedic prosthesis 500 constitutes more than just a thin
surface coating on the porous bone-ingrowth layer L.sub.3.
[0043] Advantageously, the above-described depositing step 106 and
the above-described applying step 108 of method 100 (FIG. 1)
produce orthopaedic prosthesis 500 in a rapid and automated manner.
The solid bearing layer L.sub.2 of orthopaedic prosthesis 500 may
be rapidly and automatically manufactured to strengthen and support
orthopaedic prosthesis 500 and/or to interact with an adjacent
orthopaedic component. In the illustrated embodiment of FIG. 12,
for example, the solid bearing layer L.sub.2 of orthopaedic
prosthesis 500 is configured to receive a polymeric liner 502,
which in turn interacts with and receives the patient's adjacent
femoral head. Also, the solid bearing layer L.sub.2 of orthopaedic
prosthesis 500 may be rapidly and automatically manufactured in a
highly complex geometry, without requiring any subsequent shaping.
At substantially the same time, the interdigitating layer L.sub.1
may be rapidly and automatically produced to bond the solid bearing
layer L.sub.2 to the underlying porous bone-ingrowth layer
L.sub.3.
[0044] Continuing to step 110 of method 100 (FIG. 1), orthopaedic
prosthesis 500 is removed from build chamber 300, leaving behind
metal powder 302 that was not converted to solid metal 306. Also,
excess metal powder 302 may be removed from porous substrate 200 by
shaking orthopaedic prosthesis 500 and/or by blowing pressurized
air into porous substrate 200, for example. Orthopaedic prosthesis
500 may then be subjected to any necessary cleaning, shaping,
processing, sterilizing, or packaging steps. For example, in the
illustrated embodiment of FIG. 12, the polymeric liner 502 may be
coupled to solid bearing layer L.sub.2 of orthopaedic prosthesis
500 to facilitate articulation with the patient's adjacent femoral
head.
[0045] Finally, in step 112 of method 100 (FIG. 1), orthopaedic
prosthesis 500 is implanted into the patient's body. Bone-engaging
surface 206 of orthopaedic prosthesis 500 is implanted against the
patient's bone to encourage bone and/or soft tissue ingrowth into
the porous bone-ingrowth layer L.sub.3 of orthopaedic prosthesis
500. Orthopaedic prosthesis 500 may be secured in place using
suitable fasteners (e.g., bone screws) or bone cement, for
example.
[0046] While this invention has been described as having exemplary
designs, 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.
* * * * *