U.S. patent application number 16/883632 was filed with the patent office on 2020-09-10 for dynamic, non-homogeneous shape memory alloys.
The applicant listed for this patent is Verkko Biomedical, LLC. Invention is credited to Reed A. Ayers.
Application Number | 20200283879 16/883632 |
Document ID | / |
Family ID | 1000004856779 |
Filed Date | 2020-09-10 |
![](/patent/app/20200283879/US20200283879A1-20200910-D00000.png)
![](/patent/app/20200283879/US20200283879A1-20200910-D00001.png)
![](/patent/app/20200283879/US20200283879A1-20200910-D00002.png)
![](/patent/app/20200283879/US20200283879A1-20200910-D00003.png)
![](/patent/app/20200283879/US20200283879A1-20200910-D00004.png)
United States Patent
Application |
20200283879 |
Kind Code |
A1 |
Ayers; Reed A. |
September 10, 2020 |
DYNAMIC, NON-HOMOGENEOUS SHAPE MEMORY ALLOYS
Abstract
Composite alloys comprising a first alloy portion comprising
nickel and titanium and a second alloy portion comprising nickel
and titanium in a different stoichiometry than the first alloy
portion are disclosed, along with related methods of manufacture
and use. Particularly, the composite alloys may be used in
customized medical devices where a shape memory effect would be
beneficial.
Inventors: |
Ayers; Reed A.; (Arvada,
CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Verkko Biomedical, LLC |
Aurora |
CO |
US |
|
|
Family ID: |
1000004856779 |
Appl. No.: |
16/883632 |
Filed: |
May 26, 2020 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15659369 |
Jul 25, 2017 |
10662513 |
|
|
16883632 |
|
|
|
|
62366837 |
Jul 26, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 17/00 20130101;
A61B 17/72 20130101; B33Y 70/00 20141201; Y02P 10/25 20151101; C22C
1/0458 20130101; B22F 3/1055 20130101; C22C 1/0433 20130101; C22C
14/00 20130101; A61L 27/06 20130101; C21D 2201/01 20130101; C22F
1/006 20130101; C22C 19/03 20130101; A61B 17/7002 20130101; B33Y
80/00 20141201; A61B 2017/00867 20130101; B33Y 10/00 20141201; A61B
2017/00526 20130101; B22F 7/06 20130101; A61L 27/306 20130101; B22F
3/105 20130101; A61B 17/80 20130101; A61L 27/00 20130101 |
International
Class: |
C22F 1/00 20060101
C22F001/00; C22C 19/03 20060101 C22C019/03; C22C 14/00 20060101
C22C014/00; C22C 1/04 20060101 C22C001/04; A61L 27/00 20060101
A61L027/00; A61L 27/06 20060101 A61L027/06; B33Y 70/00 20060101
B33Y070/00; A61B 17/70 20060101 A61B017/70; B22F 7/06 20060101
B22F007/06; A61B 17/80 20060101 A61B017/80; B22F 3/105 20060101
B22F003/105; A61L 27/30 20060101 A61L027/30; A61B 17/00 20060101
A61B017/00; B33Y 10/00 20060101 B33Y010/00; A61B 17/72 20060101
A61B017/72 |
Claims
1. A composite alloy, comprising: a first alloy portion comprising
a first composition of 45 to 55 wt. % nickel (Ni) and 45 to 55 wt.
% titanium (Ti); and a second alloy portion comprising a second
composition of 45 to 55 wt. % nickel (Ni) and 45 to 55 wt. %
titanium (Ti); wherein said first and said second compositions are
different; and wherein said first alloy portion and said second
alloy portion are adjacent and interconnected through a functional
gradient interface.
2. The composite alloy of claim 1, wherein said composite alloy is
formed into a medical device selected from the group consisting of
an implantable spine rod, an external medical brace, a component of
an external medical brace, a bone plate, a screw, an intramedullary
nail, a vertebral spacer and a pin.
3. The composite alloy of claim 1, wherein said first and/or said
second composition(s) further comprise up to 10 wt. % of at least
one element selected from the group consisting of zirconium (Zr),
aluminum (Al), niobium (Nb), vanadium (V), copper (Cu), iron (Fe)
and combinations thereof.
4. The composite alloy of claim 1, wherein said first and/or said
second composition(s) comprise 0 wt. % to 2 wt. % of at least one
element selected from the group consisting of Zr, Al, Nb, V, Cu, Fe
and combinations thereof.
5. The composite alloy of claim 1, wherein the first alloy portion
and the second alloy portion occupy first and second locations
respectively.
6. The composite alloy of claim 5, wherein the first and second
locations are distributed non-uniformly throughout the composite
alloy.
7. The composite alloy of claim 1, wherein at least one of the
first and the second alloy is a shape memory alloy.
8. The composite alloy of claim 1, wherein said first alloy is a
superelastic alloy and said second alloy is a shape memory alloy,
or wherein said first alloy is a superelastic alloy and said second
alloy is a different superelastic alloy, or wherein said first
alloy is a shape memory alloy and said second alloy is a different
shape memory alloy.
9. The composite alloy of claim 1, wherein said composite alloy is
trained to undergo a transition from a first desired shape to a
second desired shape.
10. The composite alloy of claim 9, wherein the total strain
experienced by the composite alloy over the course of the
transition is less than 0.2.
11. The composite alloy of claim 9, wherein the rate of strain
experienced by the composite alloy over the course of the
transition is less than 2000 .mu..epsilon./day.
12. The composite alloy of claim 1, wherein the density of the
first alloy portion is between 30% and 100% of theoretical maximum
density for the first alloy, and the density of the second alloy
portion is between 30% and 100% of theoretical maximum density for
the second alloy.
13. The composite alloy of claim 1, wherein a porosity of said
first alloy portion and/or said second alloy portion is between 0%
and 70% on the basis of image analysis or Archimedes principle.
14. The composite alloy of claim 1 further comprising a
coating.
15. The composite alloy of claim 14, wherein the coating is
selected from the group consisting of a metal, a metal alloy, a
ceramic, a polymer, titanium hydroxide (Ti(OH).sub.2), titanium
hydride (TiH.sub.2), titanium nitride (TiN), titanium dioxide
(TiO.sub.2), collagen, bone morphogenic proteins and combinations
thereof.
16. The composite alloy of claim 1, wherein the functional gradient
interface is predominantly oriented along a longitudinal axis of
the composite alloy.
17. The composite alloy of claim 1, wherein the functional gradient
interface is predominantly oriented along a lateral axis of the
composite alloy.
18. The composite alloy of claim 1, wherein the functional gradient
interface is non-linear.
19. The composite alloy of claim 1 further comprising a third alloy
portion comprising a third composition.
20. The composite alloy of claim 19, wherein the third alloy
portion is adjacent and interconnected through another functional
gradient interface with the first alloy portion or the second alloy
portion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 15/659,369, filed Jul. 25, 2017, now U.S. Pat. No. 10,662,513,
which claims the benefit of and priority to U.S. Provisional Patent
Application No. 62/366,837, filed Jul. 26, 2016, both of which are
hereby incorporated by reference in their entireties.
STATEMENT REGARDING GOVERNMENT FUNDING
[0002] None.
BACKGROUND
[0003] In orthopedic spinal procedures requiring the use of
stabilizing or bone affecting instrumentation to correct
deformities such as scoliosis, to treat trauma, or to achieve
fusion, the use of rigid or stiff instrumentation is the current
standard of care. This instrumentation, however, has many
limitations.
[0004] First, it is difficult to use due to inherent stiffness,
where the rods have to be rigid enough to hold the weight and
deforming forces of a patient's spine in three-dimensional space.
This level of rigidity makes it difficult to intricately contour
the rods to fit the patient's anatomy.
[0005] Second, the rigidity of the rods limits the correction of a
spine to that which can be achieved acutely in the short duration
of an operation. The spine is a living, dynamic system that could
potentially deform over longer periods of time compared to the
brief time allowed in the operating room. Thus, if continuous
forces could be applied for longer periods of time, greater
correction could be obtained.
[0006] Third, spine constructs are often "over-engineered", which
can result in stress shielding (a reduction in bone density due to
reduced physiological responses to impact) and/or adjacent level
degeneration. Further, the existence or development of
screw-rod-bone mismatches in rigidity can lead to bone failure
(fracture).
[0007] Fourth, since instrumentation systems (rods and screws
combined) are rigid and cannot tolerate many cycles of strain
relative to the life of the patient, fusion of the spine is
required. Thus, spines that perhaps could be treated with
motion-preserving techniques currently require fusion to correct
curvature.
SUMMARY
[0008] Shape memory alloy (SMA) instrumentation may address the
clinical challenges outlined above. For example, SMAs slowly revert
to an original shape, which addresses the time constraints
previously mentioned and may allow continued physiologic motion
while applying a deformity-correcting force over a duration of 1-5
years. The instrumentation can also be converted to a ductile phase
in the operating theater when warmed and implanted in order to have
the ability to customize rods to fit a patient's biomechanical
needs, even when stiffer devices are used for heavier patients or
for more inherently unstable constructs.
[0009] Methods and devices comprising composite alloys that a
surgeon can shape into a medical device in the operating room and
then implant into a patient during surgery are provided herein.
These devices mimic the bone mechanics more appropriately than
existing materials, and they can be trained to move bone as
dictated by the patient's physiology, reducing the need for staged
surgeries.
[0010] In an embodiment, a medical device, such as a spine rod, is
comprised of a NiTi metal alloy that has at least two portions with
different compositions that are adjacent and interconnected through
a functional gradient interface. Additional metals may be included
in the NiTi alloy. In an embodiment, the at least two portions of
the alloy may have different physical and/or chemical properties,
such as yield strength, tensile strength, Young's modulus,
transition temperature, oxidation susceptibility, phase ratios,
elemental stoichiometry, intermetallic content, and density, e.g.,
due to different compositions and/or different porosities. The
incorporation of various alloy compositions, densities, and
porosities within a single device, and in a predetermined 3D
layout, makes it possible to customize medical devices made of the
composite alloys to meet a patient's biomedical needs.
[0011] In an aspect, a method of producing a composite alloy
comprises: depositing a non-uniform powder layer onto a surface,
wherein the non-uniform powder layer comprises a first portion
having a first composition of at least nickel (Ni) and titanium
(Ti) and a second portion having a second composition of at least
Ni and Ti, wherein the first and second compositions are different,
the first portion is received at a first location of the surface
and the second portion is received at a second location of the
surface, and the first and second locations are different; applying
energy from an energy source to the non-uniform powder layer
substantially concurrently with the depositing, wherein the energy
application forms a substantially contiguous layer of the composite
alloy comprising a first alloy portion having the first composition
at the first location on the surface and a second alloy portion
having the second composition at the second location on the
surface; and repeating the depositing and applying steps to form a
body having a first desired shape comprising at least the first and
second alloy portions. In an embodiment, a method of producing a
composite alloy further comprises a step of thermo-mechanically
training the composite alloy.
[0012] In an aspect, a composite alloy comprises a first alloy
portion comprising a first composition of 45 to 55 wt. % nickel
(Ni) and 45 to 55 wt. % titanium (Ti) and a second alloy portion
comprising a second composition of 45 to 55 wt. % nickel (Ni) and
45 to 55 wt. % titanium (Ti); wherein the first and the second
compositions are different; and wherein the first alloy portion and
the second alloy portion are adjacent and interconnected through a
functional gradient interface. In an embodiment, the first and the
second compositions are stoichiometrically different.
[0013] In an embodiment, the composite alloy further comprises a
third alloy portion comprising a third composition, wherein the
third alloy portion is adjacent and interconnected through a
functional gradient interface with the first alloy portion and/or
the second alloy portion.
[0014] In an embodiment, a functional gradient interface is
predominantly oriented along a longitudinal axis of the composite
alloy or is predominantly oriented along a lateral axis of the
composite alloy. In an embodiment, a functional gradient interface
is non-linear.
[0015] In an embodiment, a composite alloy is formed into a medical
device. For example, the medical device may be selected from the
group consisting of an implantable spine rod, an external medical
brace, a component of an external medical brace, a bone plate, a
screw, an intramedullary nail, a vertebral space and a pin. In an
embodiment, the medical device is an implantable spine rod.
[0016] In an embodiment, the density of the first alloy portion is
between 30% and 100% of theoretical maximum density for the first
alloy, and the density of the second alloy portion is between 30%
and 100% of theoretical maximum density for the second alloy.
[0017] In an embodiment, the first alloy portion and the second
alloy portion occupy first and second locations respectively. In an
embodiment, the first location and the second location are
predetermined. In an embodiment, the first and second locations are
distributed non-uniformly throughout the composite alloy.
[0018] In an embodiment, the first and second compositions each
comprise 45 wt. % to 55 wt. % Ni and 45 wt. % to 55 wt. % Ti.
[0019] In an embodiment, the first and/or the second composition(s)
further comprise(s) up to 10 wt. %, or up to 8 wt. %, or up to 5
wt. % of at least one element selected from the group consisting of
zirconium (Zr), aluminum (Al), niobium (Nb), vanadium (V), copper
(Cu), iron (Fe) and combinations thereof.
[0020] In an embodiment, the first and/or the second composition(s)
comprise(s) 0 wt. % to 2 wt. %, or 0.01 wt. % to 2 wt. %, or 0.02
wt. % to 1.8 wt. %, or 0.05 wt. % to 1.5 wt. %, or 0.08 wt. % to
1.3 wt. % of at least one element selected from the group
consisting of Zr, Al, Nb, V, Cu, Fe and combinations thereof.
[0021] In an embodiment, the powder layer comprises powder
particles having a mean diameter between 1,000 nm and 100,000 nm,
or between 1,000 nm and 50,000 nm, or between 1,000 nm and 10,000
nm, or between 1,000 nm and 5,000 nm, or between 1,000 nm and 4,400
nm.
[0022] In an embodiment, a porosity of the first alloy portion
and/or the second alloy portion is between 0% and 70%, or between
0.5% and 70%, or between 25% and 70%, or between 50% and 65% on the
basis of image analysis or Archimedes principle.
[0023] In an embodiment, the first alloy is a superelastic alloy
and the second alloy is a shape memory alloy, or the first alloy is
a superelastic alloy and the second alloy is a different
superelastic alloy, or the first alloy is a shape memory alloy and
the second alloy is a different shape memory alloy. In an
embodiment, a composite alloy may be 0-100% superelastic, 0-100%
shape memory alloy, or any combination thereof.
[0024] In an embodiment, the composite alloy is trained to undergo
a transition from a first desired shape to a second desired shape.
For example, one or more portions of a composite alloy may
transition from a martensite phase to an austenite phase. In an
embodiment, the total strain in tension, compression, torsion or
combinations thereof experienced by the composite alloy over the
course of the transition is less than 0.2, or less than 0.1, or
less than 0.05. In an embodiment, the rate of strain experienced by
the composite alloy over the course of the transition is less than
2000 .mu..epsilon./day, or less than 1500 .mu..epsilon./day, or
less than 1000 .mu..epsilon./day, or less than 500
.mu..epsilon./day. In an embodiment, a composite alloy has a
non-uniform strain response throughout its bulk.
[0025] In an embodiment, a method of producing a composite alloy
further comprises a step of coating the composite alloy with a
coating. For example, the coating may be selected from the group
consisting of a metal, a metal alloy, a ceramic, a polymer,
titanium hydroxide (Ti(OH).sub.2), titanium hydride (TiH.sub.2),
titanium nitride (TiN), titanium dioxide (TiO.sub.2), collagen,
bone morphogenic proteins and combinations thereof. Suitable metals
for the coating include but are not limited to biocompatible
metals, such as gold, silver and platinum.
[0026] In an embodiment, an energy source comprises a coherent
radiation source, a thermal heat source, an electrical energy
source, or any combination thereof. In an embodiment, the energy
source is an electrical energy source and the step of applying
energy comprises spark plasma sintering. In an embodiment, the
energy source is a coherent radiation source and the step of
applying energy comprises condensed-phase combustion synthesis.
[0027] In an embodiment, each of the first and second compositions
has a heat of combustion of at least 350 joules per gram.
[0028] In an embodiment, a non-equilibrium process is used to
fabricate a composite alloy comprising a variety of compositions,
densities, and porosities within a single unitary body, such as a
medical device. The distribution of the compositions, densities,
and porosities within the unitary body is tailored to fit a
patient's biomedical needs.
[0029] In an embodiment, the composite alloy comprises a shape
memory alloy capable of transitioning from a first desired shape to
a second desired shape under a selected stimulus. In an embodiment,
the first desired shape is a spinal rod characterized by matching
the patient conformation at the time of surgery and the second
desired shape is a spinal rod characterized by a shape change to a
desired conformation as deemed necessary by the treating surgeon to
correct the deformity or provide patient balance. In an embodiment,
the first desired shape is a shape that substantially conforms to a
patient's anatomy at the time of surgery and the second desired
shape is a shape more closely approximating an ideal anatomical
shape. In an embodiment, the first desired shape is a shape that
substantially conforms to a patient's anatomy at the time of
surgery and the second desired shape is a substantially ideal
anatomical shape.
[0030] In an embodiment, the selected stimulus is thermal energy.
In an embodiment, the thermal energy raises the temperature of the
first and/or the second alloy between 0.degree. C. and
1,000.degree. C., or between 1.degree. C. and 850.degree. C., or
between 5.degree. C. and 600.degree. C. In an embodiment, the
thermal energy is between 0 Watts and 2000 Watts, or between 0.5
Watts and 1500 Watts, or between 5 Watts and 1000 Watts, or between
50 Watts and 500 Watts.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 provides a photograph of a 3D-printed NiTi spine rod
placed in a cadaver spine, according to an exemplary
embodiment.
[0032] FIG. 2 provides schematic sagittal and coronal views of a
hip and a spine receiving corrective forces (arrows) from one or
more dynamic, composite alloy spine rods, according to the present
invention.
[0033] FIG. 3 provides schematic views of an exemplary composite
alloy spine rod in lateral cross-section (A), as well as a sagittal
view of a spine with a shape memory alloy (SMA) on one side of the
spine and a superelastic alloy on the other side of the spine (B)
and coronal views of a spine with a composite alloy having a SMA
portion proximal to the spine and a superelastic portion distal
from the spine or, alternatively, a superelastic portion proximal
to the spine and a SMA distal from the spine (C), according to
multiple embodiments.
[0034] FIG. 4 provides a schematic diagram of a spine rod
illustrating different types of alloys formed into a single,
composite body, according to an embodiment.
STATEMENTS REGARDING CHEMICAL COMPOUNDS AND NOMENCLATURE
[0035] In an embodiment, an alloy, a composition or compound of the
invention is isolated or purified. In an embodiment, an isolated or
purified compound is at least partially isolated or purified as
would be understood in the art. In an embodiment, an alloy,
composition or compound of the invention has a chemical purity of
at least 95%, optionally for some applications at least 99%,
optionally for some applications at least 99.9%, optionally for
some applications at least 99.99%, and optionally for some
applications at least 99.999%.
DETAILED DESCRIPTION
[0036] In general, the terms and phrases used herein have their
art-recognized meaning, which can be found by reference to standard
texts, journal references and contexts known to those skilled in
the art. The following definitions are provided to clarify their
specific use in the context of this description.
[0037] "Alloy" refers to a material of two or more metals, or of a
metal and another material. For example, brass is an alloy of
copper and zinc; steel is an alloy of iron and carbon.
[0038] A "composite alloy" refers to unitary body comprising two or
more alloys, or an alloy and another material.
[0039] A "construct" is an object built from various parts. In an
embodiment, a composite alloy is a construct.
[0040] "Composition" refers to the quantitative (mass)
relationships among elements in compounds.
[0041] "Shape memory alloy (SMA)" refers to a unique class of metal
alloys that can recover apparent permanent strains when they are
heated above a certain temperature (transition temperature). The
SMAs have two stable phases--the high-temperature phase, called
austenite, and the low-temperature phase, called martensite. An SMA
is an alloy that "remembers" its original shape and when deformed
returns to its pre-deformed shape when heated.
[0042] "Training" refers to the process of cycling an SMA through
heating and cooling cycles while mechanically constraining the
alloy in order to predispose the alloy to adopt a particular
desired shape when it undergoes a phase transformation.
[0043] A "green body" or "green construct" refers to a precursor of
a final product. For example, a final product may be achieved by
heating, combusting, sintering and/or shaping a green construct. In
an embodiment, a green construct may be a compressed powder
formation having the stoichiometry, 3D layout, and general
dimensions of a desired composite alloy.
[0044] "Spark plasma sintering (SPS)", also known as field assisted
sintering technique (FAST) or pulsed electric current sintering
(PECS), is a sintering technique. The main characteristic of SPS is
that a pulsed DC current directly passes through a graphite die, as
well as a powder compact (green construct) in cases of conductive
samples.
[0045] "Condensed-phase combustion synthesis" refers to Combustion
Synthesis (CS) which can occur by two modes: self-propagating
high-temperature synthesis (SHS) and volume combustion synthesis
(VCS). In both cases, reactants may be pressed into a pellet (green
construct), typically cylindrical in shape. The samples are then
heated by an external source (e.g., tungsten coil, laser) either
locally (SHS) or uniformly (VCS) to initiate an exothermic
reaction.
[0046] "Superelasticity" refers to an elastic (reversible) response
to an applied stress triggering a phase transformation between the
austenite and martensite phases of a crystal.
[0047] "Porosity" refers to the ratio, expressed as a percentage,
of the volume of the pores or interstices of a substance, such as
an alloy or green construct, to the total volume of the mass.
[0048] "Archimedes principle" refers to the upward buoyant force
that is exerted on a body immersed in a fluid, whether fully or
partially submerged. The force is equal to the weight of the fluid
that the body displaces.
[0049] A "functional gradient interface" is an area of transition
between a first composition and a second composition characterized
by a spatial variation in composition and/or structure. Materials
comprising one or more functional gradient interfaces generally do
not have distinct crystallographic boundaries or domains.
[0050] "Proximal" and "distal" refer to the relative positions of
two or more objects, planes or surfaces. For example, an object
that is close in space to a reference point relative to the
position of another object is considered proximal to the reference
point, whereas an object that is further away in space from a
reference point relative to the position of another object is
considered distal to the reference point.
[0051] "3-D printing" refers to an additive manufacturing process
that may be used to produce three-dimensional, complex objects,
layer-by-layer, often without molds or dies.
[0052] A "predetermined" location refers to the position of an
object, plane, surface or material within a construct that is set
or determined prior to fabrication and achieved during
fabrication.
[0053] The terms "direct and indirect" describe the actions or
physical positions of one component relative to another component.
For example, a component that "directly" acts upon or touches
another component does so without intervention from an
intermediary. Contrarily, a component that "indirectly" acts upon
or touches another component does so through an intermediary (e.g.,
a third component).
[0054] "Contiguous" refers to materials or layers that are touching
or connected throughout in an unbroken sequence.
[0055] "Non-uniform" refers to an inconstant, varying, irregular or
non-homogeneous distribution.
[0056] Processing Techniques
[0057] NiTi has long been investigated as an alloy for biomedical
applications, with several products currently on the market.
However, current processing of NiTi SMA metals is based on
equilibrium processes such as vacuum arc melting, vacuum induction
melting and electron beam melting generating homogeneous material
that has a consistent strain response throughout the entire bulk.
(Duerig 1994, Szurman and Miroslav 2010.) These processes are
intended to generate a homogeneous bulk.
[0058] Disclosed herein is the creation and use of non-equilibrium
processing techniques to generate NiTi alloys having non-uniform
densities and/or porosities for use in medical procedures, such as
spinal reconstructions. The non-uniform material properties are
generated by the specific design of material composition at
specific sites within the green construct. For example, a Ti-rich
region (superelastic) can be created by including an excess of Ti
particles in a specified zone next to a Ni-rich region (shape
memory) where the stoichiometry has more Ni particles present.
Stoichiometry can also be modified by the addition of other
alloying elements such as Zr, Al, Nb, V, Cu, and/or Fe. Each
alloying element has a specific effect on the subsequent material
properties due to modification of the material microstructure.
[0059] Composite alloys of the medical devices disclosed herein are
fabricated layer-by-layer to tailor the compositions, densities,
and porosities within a single device to meet a patient's
biomedical needs. Suitable fabrication processes include combustion
synthesis with mechanical construction of the reacting volume
(consolidation) during reaction, direct metal laser sintering
(DMLS) and spark plasma sintering (SPS). These processes rely on
the solid-state reaction at the interfaces between elemental
particles in a green body. In these cases no large volume of molten
material is developed. The processes can be accommodated/enhanced
by 3D laser printing technology, e.g., the laser initiates a SHS
reaction to form the metal as the device is printed.
[0060] To generate a layer of homogeneous material within a
composite alloy, a single type of powder is placed in a 3D printer
and all laser parameters are kept constant. If a preheat is needed
to effect combustion, which is common when a mixture is Ti-rich,
the laser is rastered across the surface of the powder at a reduced
power density (e.g., by increasing spot diameter, operating at a
fast raster rate or lowering power output of the laser) to preheat
the powder to a target temperature of about 350.degree. C. to
400.degree. C.
[0061] For SPS production of a non-homogeneous material, powders
are placed or packed and axially or isostatically pressed into a
green construct. Loose packed powders are processed in a graphite
die, while compressed powders can be processed in a graphite die or
with no die (open die). Current up to 10,000 amps at 0-10 V is
passed through the green construct and/or die to affect current
aided diffusion between powder particles. Process temperatures can
range from 100.degree. C. to 600.degree. C. for 10 minutes to 120
minutes to achieve the desired microstructure. Alloy "training" is
subsequently performed in an annealing oven, if necessary.
[0062] In addition to compositional variation, porosity can be used
to affect material properties based on the rule of mixtures.
Porosity of the composite alloys disclosed herein is generally
controlled by use of a printer having a minimum pore size of about
100 .mu.m.
[0063] Spine rods created by the present fabrication processes are
typically 4 mm to 6 mm in diameter and 50 mm to 400 mm in length.
The ends of a spine rod according to the present invention may be
porous in a region 1-2 vertebral levels beyond fusion to reduce
strength and stiffness, thereby reducing proximal junction
kyphosis/proximal junction failure (PJK/PJF).
[0064] Examples of the composite alloys and medical devices are
illustrated in the accompanying figures. FIG. 1 provides a
photograph of a 3D printed NiTi spine rod placed in a cadaver
spine. FIG. 2 provides schematic sagittal and coronal views of a
hip and a spine receiving corrective forces (arrows) from one or
more dynamic spine rods 10. FIG. 3 provides schematic views of an
exemplary composite spine rod in lateral cross-section (A), as well
as a sagittal view of a spine with a shape memory alloy (SMA) on
one side of the spine and a superelastic alloy on the other side of
the spine (B) and coronal views of a spine with a composite alloy
having a SMA portion proximal to the spine and a superelastic
portion distal from the spine or, alternatively, a superelastic
portion proximal to the spine and a SMA distal from the spine (C).
FIG. 4 provides a schematic diagram of a spine rod illustrating
different types of alloys formed into a single, composite body,
according to an embodiment.
Statements Regarding Incorporation by Reference and Variations
[0065] All references cited throughout this application, for
example patent documents including issued or granted patents or
equivalents; patent application publications; and non-patent
literature documents or other source material; are hereby
incorporated by reference herein in their entireties, as though
individually incorporated by reference, to the extent each
reference is at least partially not inconsistent with the
disclosure in this application (for example, a reference that is
partially inconsistent is incorporated by reference except for the
partially inconsistent portion of the reference).
[0066] The terms and expressions which have been employed herein
are used as terms of description and not of limitation, and there
is no intention in the use of such terms and expressions of
excluding any equivalents of the features shown and described or
portions thereof, but it is recognized that various modifications
are possible within the scope of the invention claimed. Thus, it
should be understood that although the invention has been
specifically disclosed by preferred embodiments, exemplary
embodiments and optional features, modification and variation of
the concepts herein disclosed can be resorted to by those skilled
in the art, and that such modifications and variations are
considered to be within the scope of this invention as defined by
the appended claims. The specific embodiments provided herein are
examples of useful embodiments of the invention and it will be
apparent to one skilled in the art that the invention can be
carried out using a large number of variations of the devices,
device components, and method steps set forth in the present
description. As will be apparent to one of skill in the art,
methods and devices useful for the present methods and devices can
include a large number of optional composition and processing
elements and steps. All art-known functional equivalents of
materials and methods are intended to be included in this
disclosure.
[0067] When a group of substituents is disclosed herein, it is
understood that all individual members of that group and all
subgroups are disclosed separately. When a Markush group or other
grouping is used herein, all individual members of the group and
all combinations and subcombinations possible of the group are
intended to be individually included in the disclosure. As used
herein, "and/or" means that one, all, or any combination of items
in a list separated by "and/or" are included in the list; for
example "1, 2 and/or 3" is equivalent to "`1` or `2` or `3` or `1
and 2` or `1 and 3` or `2 and 3` or `1, 2 and 3`".
[0068] It must be noted that as used herein and in the appended
claims, the singular forms "a", "an", and "the" include plural
reference unless the context clearly dictates otherwise. Thus, for
example, reference to "a rod" includes a plurality of such rods and
equivalents thereof known to those skilled in the art, and so
forth. As well, the terms "a" (or "an"), "one or more" and "at
least one" can be used interchangeably herein. It is also to be
noted that the terms "comprising", "including", and "having" can be
used interchangeably. The expression "of any of claims XX-YY"
(wherein XX and YY refer to claim numbers) is intended to provide a
multiple dependent claim in the alternative form, and in some
embodiments is interchangeable with the expression "as in any one
of claims XX-YY."
[0069] Unless defined otherwise, all technical and scientific terms
used herein have the same meanings as commonly understood by one of
ordinary skill in the art to which this invention belongs. Although
any methods and materials similar or equivalent to those described
herein can be used in the practice or testing of the present
invention, the preferred methods and materials are described.
Nothing herein is to be construed as an admission that the
invention is not entitled to antedate such disclosure by virtue of
prior invention.
[0070] Whenever a range is given in the specification, for example,
a range of integers, a temperature range, a time range, a
composition range, or concentration range, all intermediate ranges
and subranges, as well as all individual values included in the
ranges given are intended to be included in the disclosure. As used
herein, ranges specifically include the values provided as endpoint
values of the range. As used herein, ranges specifically include
all the integer values of the range. For example, a range of 1 to
100 specifically includes the end point values of 1 and 100. It
will be understood that any subranges or individual values in a
range or subrange that are included in the description herein can
be excluded from the claims herein.
[0071] As used herein, "comprising" is synonymous and can be used
interchangeably with "including," "containing," or "characterized
by," and is inclusive or open-ended and does not exclude
additional, unrecited elements or method steps. As used herein,
"consisting of" excludes any element, step, or ingredient not
specified in the claim element. As used herein, "consisting
essentially of" does not exclude materials or steps that do not
materially affect the basic and novel characteristics of the claim.
In each instance herein any of the terms "comprising", "consisting
essentially of" and "consisting of" can be replaced with either of
the other two terms. The invention illustratively described herein
suitably can be practiced in the absence of any element or
elements, limitation or limitations which is/are not specifically
disclosed herein.
* * * * *