U.S. patent application number 13/058905 was filed with the patent office on 2011-06-16 for customized implants for bone replacement.
Invention is credited to Anthony Decarmine, Scott F. Defelice.
Application Number | 20110144752 13/058905 |
Document ID | / |
Family ID | 41669212 |
Filed Date | 2011-06-16 |
United States Patent
Application |
20110144752 |
Kind Code |
A1 |
Defelice; Scott F. ; et
al. |
June 16, 2011 |
CUSTOMIZED IMPLANTS FOR BONE REPLACEMENT
Abstract
The present invention relates to customized implants for bone
replacement that are prepared from poly(ether ketone ketone) or
PEKK, and to a computer-based imaging and rapid prototyping
(RP)-based manufacturing method for the design and manufacture of
these customized implants. The PEKK customized implants made using
rapid prototyping demonstrate biomechanical properties similar (if
not identical) to that of natural bone even when prepared without
the use of processing aids such as carbon black and aluminum
powder.
Inventors: |
Defelice; Scott F.;
(Holyoke, MA) ; Decarmine; Anthony; (Lebanon,
CT) |
Family ID: |
41669212 |
Appl. No.: |
13/058905 |
Filed: |
August 7, 2009 |
PCT Filed: |
August 7, 2009 |
PCT NO: |
PCT/US09/53104 |
371 Date: |
February 14, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61088838 |
Aug 14, 2008 |
|
|
|
Current U.S.
Class: |
623/16.11 ;
523/115; 528/220 |
Current CPC
Class: |
A61F 2002/30784
20130101; A61L 27/54 20130101; A61L 2300/602 20130101; A61F
2002/30838 20130101; A61F 2002/3097 20130101; A61F 2002/3093
20130101; A61F 2240/002 20130101; A61F 2002/30952 20130101; A61F
2002/30948 20130101; A61L 27/165 20130101; A61L 2430/02 20130101;
A61F 2002/3092 20130101; B33Y 80/00 20141201; B29K 2071/00
20130101; A61F 2/30942 20130101; A61F 2002/30774 20130101; A61L
27/56 20130101; A61F 2002/30962 20130101; B29C 64/153 20170801;
A61F 2/28 20130101; A61F 2002/30968 20130101; B29L 2031/7532
20130101; A61F 2/30771 20130101; A61L 27/165 20130101; C08L 29/12
20130101 |
Class at
Publication: |
623/16.11 ;
528/220; 523/115 |
International
Class: |
A61F 2/28 20060101
A61F002/28; C08G 16/00 20060101 C08G016/00; A61L 27/46 20060101
A61L027/46 |
Claims
1. A customized implant or scaffold for bone replacement comprising
poly(ether ketone ketone) (PEKK).
2. The customized implant or scaffold of claim 1 modified to add at
least one feature selected from the group consisting of a) openings
to encourage bone, vascular and nerve in-growth, b) adding surface
pores to hold therapeutic agents, and c) adding surface anchors
and/o threaded holes.
3. The customized implant or scaffold of claim 2 wherein said
surface pores hold one or more therapeutic agents selected from the
group consisting of antibiotics, anti-coagulants,
anti-inflammatory, anti-metabolites, antivirals, bone morphogenic
proteins, cell adhesion molecules, growth factors, healing
promotors, immunosuppressants, vascularizing agents, and topical
anesthetics/analgesics; said therapeutic agents optionally being
present in or on a carrier for controlled release.
4. The customized implant or scaffold of claim 3, wherein said
carrier is encapsulated in a biocompatible or biodegradable
polymer, or in a bioadhesive gel.
5. The customized implant or scaffold of claim 1, comprising a
rigid implant having an inner core with a low porosity of 10
percent or less pores, and an outer layer, said implant having a
compressive strength (ASTM #D695) of from 100 to greater than 200
megapascals (Mpa) and a flexural modulus (ASTM #D570) of greater
than 3.5 GPa.
6. The customized implant or scaffold of claim 5 wherein said
implant replaces a load-bearing bone.
7. The customized implant or scaffold of claim 6, wherein said
load-bearing bone is selected from the spine, a long bone of the
arms or legs, and a hip bone.
8. The customized implant or scaffold of claim 7, wherein at least
95 percent of pores have a diameter of 1-500 microns, and may or
may not be connected.
9. The customized implant or scaffold of claim 1 comprising a
substantially uniform cross-sectional morphology having a porosity
of greater than about 35 percent, wherein the pores are
interconnected and have an average diameter of 50-250 microns, and
wherein said implant or scaffold has a compressive strength (ASTM
#D695) of from 10 to 200 megapascals (Mpa) and a flexural modulus
(ASTM #D570) of from 0.5 to greater than 4.5 GPa.
10. The customized implant or scaffold of claim 9, comprising a
bone replacement scaffolding for ongrowth/ingrowth of tissues, or
as a support for stem cells.
11. The customized implant or scaffold of claim 9 comprising a
three-dimensional lattice structure having a plurality of bars
crossing each other in a plurality of zones, the bars being fused
in each of these zones, wherein the interstitial spaces between
adjacent bars define a plurality of interconnected pores or
channels in lattice structure.
12. A laser sinterable composition comprising poly(ether ketone
ketone) (PEKK) powder, wherein said powder has an average particle
size of from 10-150 microns, and is either a) semi-crystalline,
having at least 10% crystallinity by weight as measured by DSC, or
said powder is b) quasi-amorphous, at most 2% crystallinity as
measured by DSC.
13. The laser sinterable composition of claim 12, wherein said
composition further comprises one or more fillers selected from the
group consisting of glass, carbon, mineral fillers,
surface-bioactive ceramics, hydroxyapatite (HAp), biologically
active glass, resorbable bioactive ceramics, .alpha.-tricalcium
phosphate (.alpha.-TCP),.beta.-TCP), solids that will render the
implant or scaffold radioopaque, and barium sulfate
(BaSO.sub.4).
14. The laser sinterable composition of claim 12 having an average
particle size of from 20-100 microns.
15. The laser sinterable composition of claim 12 wherein said
semi-crystalline powder has 15-90% crystallinity as measured by
DSC.
16. The laser sinterable composition of claim 12 having an average
particle size of from 50-70 microns.
17. The laser sinterable composition of claim 12 wherein said
semi-crystalline powder has 15-35% crystallinity as measured by
DSC.
18. A process for producing a customized implant or scaffold for
bone replacement comprising the steps of : (a) scanning a patient
in an area requiring bone repair or replacement to obtain
tomographic information; (b) designing a bone implant model using
computer aided design from the tomographic information obtained
from the patient; (c) optionally, modifying the bone implant model
by one or more of the following steps: adding suture anchors,
threaded holes, mating surfaces and textures, open cell regions for
scaffolding, surface pores to carry antibiotics, and/or varying
density or porosity levels so as to vary stiffness or rigidity; and
(d) forming a bone implant or scaffold using a solid free-form
fabrication method from the bone implant model, the bone implant
comprising sequential layers of biocompatible poly(ether ketone
ketone) (PEKK) powder.
19. The process of claim 18, wherein said fabrication method in
step (d) is by selective laser sintering (SLS), fused deposition
modeling (FDM) or selective mask sintering (SMS).
20. The process of claim 18, wherein the PEKK powder has an average
particle size of from 10 to 150 microns.
21. The process of claim 18. wherein said PEKK powder further
comprises from 5 to 40 weight percent of additives, based on the
weight of PEKK.
22. The process of claim 21, wherein said additives are selected
from the group consisting of surface-bioactive ceramics, resorbable
bioactive ceramics, solids to render the implant or scaffold
radioopaque.
Description
TECHNICAL FIELD
[0001] The present invention generally relates to customized
implants for bone replacement that are prepared from poly(ether
ketone ketone) or PEKK, and to a computer-based imaging and rapid
prototyping (RP)-based manufacturing method for the design and
manufacture of these customized implants.
BACKGROUND AND SUMMARY OF THE INVENTION
[0002] Bone is composed of two kinds of tissue, exterior tissue
which is dense in texture (compact tissue) and interior tissue that
consists of slender fibers and lamellae that together form a
lattice-type structure (cancellous tissue). Damage or loss of bone
can result from trauma, congenital anomaly, pathologic conditions
(e.g., rheumatoid arthritis, scleroderma, acromegaly and Gauchers
disease), and surgical procedures.
[0003] In conventional treatment of bone defects, bone-derived or
synthetic biomaterials are used to restore form and function. These
biomaterials are preferably in the form of porous implant
structures having interconnected porous spaces across the
substratum of the implant. This allows bone growth into the porous
spaces of the implant, securing its incorporation and
osteointegration with the surrounding or adjacent viable bone at
the margins of the bone defect.
[0004] Porous implant structures may be fabricated by a number of
manufacturing routes. For implants made according to a standardized
format (i.e., not customized for a particular individual) many
conventional fabrication techniques can be used, including casting
(e.g., ceramic-mold casting, centrifugal casting, die casting,
investment casting, lost foam casting, permanent-mold casting,
plaster-mold casting, pressure casting, sand casting, shell mold
casting, slip casting, squeeze casting, slush casting, vacuum
casting), extrusion, laser cutting, machining (e.g.,
electrochemical machining, water-jet machining), molding (e.g.,
blow molding, compression molding, injection molding, powder
injection molding), thermoforming, and the like.
[0005] Implants may also be custom designed using computer-based
imaging, processing and modeling techniques to convert common
medical images into customized 3D renderings or Computer-Aided
Design (CAD) models, which may then be used to fabricate the
implant using any number of computer driven manufacturing
techniques. The CAD models may be derived from any number of
medical diagnostic imaging systems such as computed tomography
(CT), magnetic resonance imaging (MRI), positron emission
tomography (PET), and x-ray scans. Examples of computer driven
manufacturing techniques include fused deposition modeling (FDM),
selective laser sintering (SLS), and selective mask sintering
(SMS).
[0006] Regardless of the manufacturing route, the resulting implant
may then be subjected to one or more post-processing steps, which
include modifying the implant to include pre-tab holes and other
features that aid in rigid affixation.
[0007] Examples of synthetic biomaterials used in the fabrication
of porous implant structures include ceramics and polymers such as
polyethylene, polytetrafluoroethylene (PTFE) and poly(ether ether
ketone) (PEEK).
[0008] By the late 1990s, PEEK emerged as the leading biomaterial
for implants, first being offered commercially as a biomaterial for
implants in April 1998. Bolstered by the existence of a stable
supply of PEEK in the marketplace, research on PEEK biomaterials
has and continues to flourish.
[0009] Customized PEEK scaffolds that are fabricated using CAD and
rapid prototyping (RP) techniques are described in M. W. Naing et
al., FABRICATION OF CUSTOMISED SCAFFOLDS USING COMPUTER-AIDED
DESIGN AND RAPID PROTOTYPING TECHNIQUES, Rapid Prototyping Journal,
vol. 11, pages 249-259 (2005). In this publication,
PEEK-hydroxyapatite (HAP) biocomposite blends are sintered in SLS,
with the advantages of HAP reinforced PEEK composites being
identified as their strength and stiffness, which are reportedly
compatible to that of the bone. PEEK.TM. 150XF finely ground PEEK
powder is used to make these layered scaffolds.
[0010] Unfortunately, PEEK processing temperatures are quite high.
In addition, less than favorable compressive residual stress
profiles have been observed in these customized PEEK scaffolds,
attributed to the relatively high solidification rates demonstrated
by PEEK materials. Moreover, achieving and maintaining homogeneity
in PEEK-HAP powder blends is difficult, with a lack of homogeneity
causing the formation of HAP particle clusters in the powder blend.
Localized heating of these HAP particle clusters have been found to
result in the partial degradation of PEEK and/or the formation of
microscale thermal stresses in the resulting scaffold.
[0011] By way of the present invention, it has been discovered that
poly (ether ketone ketone) or PEKK may be used to make customized
implants for bone replacement using rapid prototyping. PEKK offers
the benefit of lower solidification rates, and in some embodiments,
may also offer the added benefit of considerably lower processing
temperatures.
[0012] It has also been discovered that customized implants for
bone replacement that are prepared from PEKK using rapid
prototyping demonstrate biomechanical properties similar (if not
identical) to that of natural bone even when prepared without the
use of processing aids such as carbon black and aluminum powder. In
other words, these implants meet desired shape and strength
requirements, which are typically expressed in terms of geometric
size and shape, minimum wall thickness and minimum load bearing
capacity.
[0013] The present invention specifically provides a
laser-sinterable PEKK powder product. The laser-sinterable powder
is comprised of a PEKK compound resin prepared from
semi-crystalline and/or quasi-amorphous PEKK resin, and one or more
fillers or additives selected from the group of glass, carbon and
mineral fillers. By a "semi-crystalline" or "substantially
crystalline" is meant a resin which has at least 10% crystallinity
as measured by DSC, preferably from about 15%-90%, and most
preferably from about 15-35% crystallinity. By "quasi-amorphous" is
meant a resin which has at most 2% crystallinity as measured by
DSC. The laser-sinterable powder has an average particle size
ranging from about 10 to about 150 microns (preferably, from about
20 to about 100 microns, more preferably, from about 50 to about 70
microns).
[0014] The present invention also provides customized implants for
bone replacement that are prepared from PEKK using rapid
prototyping. The phrase "rapid prototyping", as used herein, means
the automatic construction of physical objects such as implants
using sold freeform fabrication.
[0015] In a first contemplated embodiment, the customized implant
is a rigid implant having an inner core and an outer layer, the
inner core having a relatively low porosity of less than about 10%,
rendering the implant suitable for replacing bone in load bearing
applications such as the spine, long bone and hip. The inventive
rigid implant demonstrates a compressive strength (ASTM #D695) or
load bearing capability ranging from about 100 to greater than
about 200 megapascals (MPa).
[0016] Preferably, at least 95% of the pores have a diameter in the
range of from about 1 to about 500 microns. Individual pores may or
may not be connected to each other.
[0017] The implant's outer layer and its inner core preferably
match the corresponding regions of the bone to be replaced if that
bone were healthy. In other words, the outer layer would
approximate the morphologic traits of the compact tissue in the
cortical layer of a similar healthy bone, while the inner core
would approximate the morphologic traits of the cancellous tissue
in the trabecular core of a similar healthy bone.
[0018] In a second contemplated embodiment, the customized implant
is a less rigid implant with a substantially uniform
cross-sectional morphology, which has a higher porosity of greater
than about 35%. Such implants are suitable for replacing bone in
partially load bearing applications such as scaffolding for
ongrowth/ingrowth of tissues, support for stem cell media and the
like.
[0019] Preferably, individual pores in this less rigid implant are
connected to each other, the pores having a diameter in the range
of from about 50 to about 250 microns.
[0020] The present invention also provides a CAD-based RP process
for the design and manufacture of these customized implants, the
process comprising: [0021] (a) scanning a patient in an area
requiring bone repair or replacement to obtain tomographic
information; [0022] (b) designing a bone implant model at a CAD
terminal using the tomographic information obtained from the
patient; [0023] (c) optionally, modifying the bone implant model
by, for example, adding suture anchors, threaded holes, mating
surfaces and textures, open cell regions for scaffolding, surface
pores to carry antibiotics, and/or varying density or porosity
levels so as to vary stiffness or rigidity; and [0024] (d) using a
solid free-form fabrication method such as SLS to form a bone
implant from the bone implant model, the bone implant comprising
sequential layers of biocompatible PEKK.
[0025] In a preferred embodiment, a PEKK compound resin powder is
used to form the bone implant, the PEKK powder having a preferred
average particle size ranging from about 20 to about 100 microns
(more preferably, from about 50 to about 70 microns).
[0026] In a more preferred embodiment, a SLS fabrication method is
used to form the bone implant, the SLS fabrication method
comprising heating a part bed to a temperature ranging from about
280 to about 350.degree. C. and scanning a 0.015 to 1.5
Wattsec/millmeter(mm).sup.2 laser spot at selected locations of a
layer of PEKK powder contained in the part bed.
[0027] Other features and advantages of the invention will be
apparent to one of ordinary skill from the following detailed
description. Unless otherwise defined, all technical and scientific
terms used herein have the same meaning as commonly understood by
one of ordinary skill in the art to which this invention belongs.
All publications, patent applications, patents and other references
mentioned herein are incorporated by reference in their entirety.
In case of conflict, the present specification, including
definitions, will control. In addition, the materials, methods, and
examples are illustrative only and not intended to be limiting.
BEST MODE FOR CARRYING OUT THE INVENTION
[0028] Image based modeling involves three basic steps, namely,
image acquisition, image processing, and three dimensional
reconstruction (3DR) to form voxels (basic unit of computed
tomography reconstruction) that describe the 3D shape of the model
for use in further and more advanced modeling, and subsequent
manufacture.
[0029] As noted above, raw patient data in the form of noninvasive
images of the area encompassing the diseased or damaged bone(s) may
be acquired from any number of medical diagnostic imaging systems
such as CT, MRI, PET, and x-ray scans.
[0030] Image processing and 3DR may be achieved using any suitable
medical reconstructive and reverse engineering software such as
MIMICS.RTM. software programs for processing and editing images for
medical and surgical applications, which are available from
Materialise N.V. Technologielaan 15, B-3001, Leuven, Belgium, and
GEOMAGIC STUDIO.RTM. computer software for creating digitized
models, which is available from Geomagic U.S., 3200 East Hwy 54,
Cape Fear Building, Suite 300, Research Triangle Park, N.C.,
27709.
[0031] Once loaded into the software, the raw patient data in the
form of noninvasive images (which are typically in the form of
slice images) are properly registered and aligned. Next, the region
of interest (i.e., the diseased or damaged bone(s)) is identified
and a 3D rendering or model is made. In a first contemplated
embodiment, the 3D model, which is in the form of segmented
information, is further customized and then exported to an RP
machine using, for example, an RP Slice Module, which interfaces
with MIMICS.RTM. software programs or GEOMAGIC STUDIO computer
software and reportedly any kind of RP system. The RP Slice Module
is available from Materialise N.V. In a second contemplated
embodiment, the segmentation is transferred directly to an RP
machine.
[0032] The 3D rendering or model may be enhanced and further
customized by, for example, converting the 3D voxel dataset that
describes the 3D shape of the model to point data form, cleaning
the points (i.e., eliminating noise points), triangulating the
points to form a faceted model, varying density or porosity levels,
adding open cell regions for scaffolding, modeling the bone surface
using freeform surfaces or NURBS patches, further refining and
enhancing the surface (e.g., adding surface pores to carry
antibiotics, adding suture anchors and/or threaded holes, mating
surfaces and textures), etc. Design software suitable for enhancing
and further customizing the 3D rendering or model includes software
available from SolidWorks Corporation, 300 Baker Avenue, Concord,
Mass. 01742, under the trade designation SOLIDWORKS.RTM. computer
software.
[0033] The thus generated CAD models are saved in an IGES or
STEP/STL format, which are neutral data formats that allow for
transfer of the 3D rendering or CAD model between dissimilar
systems, and then exported to an RP machine.
[0034] In a preferred embodiment, the RP machine is a powder-based
SLS system. The system, which typically comprises two side powder
cartridges, a platform with variable height, heaters and a laser
source, produces 3D objects from sliced 3D CAD models using
powdered materials with heat generated by the laser.
[0035] Although the CAD-based RP process for the design and
manufacture of these customized implants will be described herein
mainly in connection with SLS, the invention is not so limited.
Other RP-based manufacturing methods such as fused deposition
modeling (FDM) and Selective Mask Sintering (SMS) may be used to
manufacture the inventive implant.
[0036] An SLS system suitable for use in the present invention
comprises: [0037] (a) a powder delivery system, for applying
successive layers of PEKK power onto a target surface on a variable
height part bed or platform; [0038] (b) a laser for generating a
laser beam; [0039] (c) a scanning system for controllably directing
the laser beam to a target plane at an uppermost surface of the
powder layer; and [0040] (d) a computer, coupled to the powder
delivery system and scanning system, and programmed to perform a
plurality of operations comprising: reading data from a CAD model,
directing the powder delivery system to lay down successive layers
of PEKK powder, and directing the scanning system to laser scan
each such successive PEKK layer.
[0041] Preferably, the laser for generating a laser beam in the SLS
system is a carbon dioxide (CO.sub.2) laser source. Such SLS
systems are available from EOS of North America Inc., 28970 Cabot
Drive, Novi, Mich. 48377-2978, and from 3D Systems, 333 Three D
Systems Circle, Rock Hill, S.C. 29730.
[0042] PEKK is used in either its pure form or with fillers or
additives selected from the group including, but not limited to,
surface-bioactive ceramics (e.g., hydroxyapatite (HAp),
BIOGLASS.RTM. biologically active glass), resorbable bioactive
ceramics (e.g., .alpha.-tricalcium phosphate (.alpha.-TCP),
.beta.-TCP), and solids that will render the implant or scaffold
radioopaque (e.g., barium sulfate (BaSO.sub.4)). Processing aids
such as carbon black and aluminum powder are not employed in the
subject invention.
[0043] In a first preferred embodiment, PEKK powder with an average
particle size ranging from about 10 to about 150 microns is used in
its pure form. Such powders are available from Oxford Performance
Materials, Inc., 120 Post Rd., Enfield, Conn. 06082 ("Oxford
Performance Materials"), under the product designation OXPEKK-IG
PEKK powder.
[0044] In a second preferred embodiment, PEKK powder in the form of
a compound resin powder with an average particle size ranging from
about 10 to about 150 microns is used, the compound resin powder
being prepared by melt blending a mixture of PEKK resin with from
about 10 to about 40% by wt. of one or more fillers or additives
(e.g., HAp, BIOGLASS.RTM. biologically active glass, .alpha.-TCP,
.beta.-TCP, BaSO.sub.4) using conventional melt-blending
techniques, and then grinding the blended product to form a
powder.
[0045] In operation, the platform used in the SLS system is heated
to a temperature ranging from about 280.degree. C. to about
350.degree. C. (preferably, from about 280.degree. C. to about
295.degree. C. (for quasi-amorphous PEKK) or from about 335.degree.
C. to about 350.degree. C. (for semi-crystalline PEKK)), and a thin
layer of PEKK powder having an average particle size ranging from
about 10 to about 150 microns (preferably, from about 20 to about
100 microns) is spread evenly onto the heated platform with a
roller mechanism. Then, the powder is raster-scanned with the
CO.sub.2 laser beam (power density (energy per unit area and time))
ranging from about 0.015 to about 1.5 Wattsec/mm.sup.2 (preferably,
from about 0.1 to about 0.25 Wattsec/mm.sup.2), with only the
powder that is struck becoming fused. Successive layers of PEKK
powder are then deposited and raster-scanned one on top of another
until the implant or scaffold is complete. Each layer is sintered
deeply enough to bond it to the underlying or preceding layer.
[0046] The customized implants of the present invention demonstrate
biomechanical properties similar (if not identical) to that of
natural bone. More specifically, the inventive implants have a
compressive strength (ASTM #D695) or load bearing capability
ranging from about 10 to greater than about 200 megapascals (MPa).
This compressive strength provides load-bearing capability greater
than typical cancellous bone and up to that of typical cortical
bone. The inventive implants also have a flexural modulus (ASTM
#D570) ranging from about 0.5 to greater than about 4.5 gigapascals
(GPa).
[0047] For implants used to replace bone in load bearing
applications such as the spine, long bone and hip, low porosity
(i.e., less than about 10%) implants would be formed. These
implants demonstrate compressive strength (ASTM #D695) or load
bearing capability ranging from about 100 to greater than about 200
MPa and flexural modulus (ASTM #D570) ranging from about 3.5 to
greater than about 4.5 GPa.
[0048] In one contemplated embodiment, the surface topography of
the low porosity implant is altered and/or one or more through
openings are added to encourage bone, vascular and nerve in-growth.
As will be readily appreciated by one skilled in the art, such
alterations or additions may be designed into the CAD model, or
formed post-manufacture by drilling, cutting, punching, or other
suitable means.
[0049] For implants used to replace bone in partially load bearing
applications such as scaffolding for ongrowth/ingrowth of tissues,
support for stem cell media and the like, a higher porosity implant
(i.e., open cell--3D interconnected pores) would be formed. These
implants demonstrate compressive strength (ASTM #D695) or load
bearing capability ranging from about 10 to about 200 MPa and a
flexural modulus (ASTM #D570) ranging from about 0.5 to about 4.5
GPa.
[0050] In one contemplated embodiment, the higher porosity implant
is in the form of a three-dimensional lattice structure. The
lattice structure, which is optimized for bone, vascular and nerve
in-growth, has a plurality of bars crossing each other in a
plurality of zones, the bars being fused in each of these zones.
Interstitial spaces provided between adjacent bars define a
plurality of interconnected pores or channels in the lattice
structure.
[0051] The implant of the present invention may contain one or more
porous reservoirs, which hold one or more therapeutic agents
including, but not limited to, antibiotics, anti-coagulants,
anti-inflammatory, anti-metabolites, antivirals, bone morphogenic
proteins, cell adhesion molecules, growth factors, healing
promotors, immunosuppressants, vascularizing agents, topical
anesthetics/analgesics, and the like. These therapeutic agents may
be prepared with carriers that will protect against rapid release
(e.g., a controlled release vehicle such as a polymer,
microencapsulated delivery system or bioadhesive gel). In one
contemplated embodiment, the therapeutic agent is encapsulated by
biocompatible, degradable polymers including, but not limited to,
polyhydroxy acids such as polylactic acid (PLA), polyglycolic acid
(PGA), and their copolymers (ALGA). These polymers are degraded by
hydrolysis to products that can be metabolized and excreted.
[0052] The inventive implant may also be modified to include means
for securing the implant to adjacent bony structures. For example,
interfacial fastening mechanisms such as custom mating screws and
fasteners may be designed into the CAD model, or formed/affixed
post-manufacture.
[0053] While various embodiments of the present invention have been
described above, it should be understood that they have been
presented by way of example only, and not limitation. Thus, the
breadth and scope of the present invention should not be limited by
any of the exemplary embodiments.
* * * * *