U.S. patent application number 17/713748 was filed with the patent office on 2022-07-28 for bone putty for bone pore and void filling.
The applicant listed for this patent is Zavation Medical Products, LLC. Invention is credited to Jeffrey Johnson, Nels Lauritzen, Brent Mitchell.
Application Number | 20220233751 17/713748 |
Document ID | / |
Family ID | 1000006253054 |
Filed Date | 2022-07-28 |
United States Patent
Application |
20220233751 |
Kind Code |
A1 |
Johnson; Jeffrey ; et
al. |
July 28, 2022 |
BONE PUTTY FOR BONE PORE AND VOID FILLING
Abstract
A bone pore or void filling composition is described. The
composition includes a mixture of: a type I collagen and/or a type
I collagen-glycosaminoglycan coprecipitate; a blend of polyethylene
glycol polymers having different molecular weights; a bone growth
stimulator; and bioactive glass. A kit for containing the bone pore
or void filling composition, and methods for using the composition
to fill a bone pore or void are also described.
Inventors: |
Johnson; Jeffrey; (Flowood,
MS) ; Lauritzen; Nels; (Somerville, NJ) ;
Mitchell; Brent; (Haskell, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zavation Medical Products, LLC |
Flowood |
MS |
US |
|
|
Family ID: |
1000006253054 |
Appl. No.: |
17/713748 |
Filed: |
April 5, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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16296465 |
Mar 8, 2019 |
11324856 |
|
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17713748 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61L 27/56 20130101;
A61L 27/26 20130101; C07K 14/78 20130101; A61L 24/0084 20130101;
C08L 67/02 20130101; A61L 27/10 20130101; A61L 27/58 20130101; A61L
27/12 20130101; A61L 27/3821 20130101; A61L 27/46 20130101; A61L
27/3608 20130101; A61L 2300/414 20130101 |
International
Class: |
A61L 27/38 20060101
A61L027/38; A61L 27/12 20060101 A61L027/12; A61L 27/58 20060101
A61L027/58; A61L 27/56 20060101 A61L027/56; A61L 27/26 20060101
A61L027/26 |
Claims
1. A bone pore or void filling composition, comprising a mixture
of: a collagen component comprising a type I collagen and/or a type
I collagen-glycosaminoglycan coprecipitate; a polyethylene glycol
component comprising a blend of polyethylene glycol polymers having
different molecular weights, a calcium phosphate component
comprising tricalcium phosphate; and a glass component comprising
bioactive glass, wherein the tricalcium phosphate and the bioactive
glass in the mixture are configured to fill bone pores of a size
less than 600 microns.
2. The composition of claim 1, wherein the tricalcium phosphate
comprises particles having a size from 50 to 300 microns.
3. The composition of claim 1, wherein the bioactive glass
comprises particles having a size from 50 to 300 microns.
4. The composition of claim 1, wherein the blend of polyethylene
glycol polymers consists of a first and a second polyethylene
glycol polymer having different molecular weights.
5. The composition of claim 4, wherein the first polyethylene
glycol polymer has molecular weight within the range of 1350 g/mol
to 1650 g/mol and the second polyethylene glycol polymer has a
molecular weight within the range of 350 g/mol to 650 g/mol.
6. The composition of claim 1, wherein the bone pore filling
composition comprises a type I collagen.
7. The composition of claim 1, wherein the bone pore filling
composition comprises a type I collagen-glycosaminoglycan
coprecipitate
8. The composition of claim 1, wherein the bioactive glass
comprises from 3% to 7.5% by weight.
9. The composition of claim 1, wherein the tricalcium phosphate
comprises from 15% to 30% by weight.
10. The composition of claim 1, wherein the weight percent of the
type I collagen or the type I collagen-glycosaminoglycan
coprecipitate is from 0.2% to 1.5%.
11. The composition of claim 1, wherein the composition further
comprises a hemostatic agent.
12. A method of filling a bone pore or void, comprising
administering a composition according to claim 1 to the site of the
bone pore or void.
13. The method of claim 12, wherein the composition is manually
applied to the bone pore or void.
14. The method of claim 12, wherein the composition is applied to
the bone pore or void using a syringe.
15. The method of claim 12, wherein the bone pore has a diameter
from 75 microns to 350 microns.
16. The method of claim 12, wherein the composition is applied to a
bone pore in spongy bone.
17. The method of claim 12, wherein the composition is applied to a
natural bone void.
18. A bone pore or void filling kit, comprising: the bone pore or
void filling composition of claim 1; a syringe for administering
the composition; and a sterile package for holding the composition
and the syringe.
19. The kit of claim 18, further comprising instructions for
filling a bone pore.
20. The kit of claim 18, wherein the blend of polyethylene glycol
polymers consists of a first and a second polyethylene glycol
polymer having different molecular weights.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and is a continuation of
U.S. Ser. No. 16/296,465 filed on Mar. 8, 2019 entitled BONE PUTTY
FOR BONE PORE AND VOID FILLING (the entire contents of which are
incorporated herein by reference).
BACKGROUND
[0002] Bone putty is used to correct surgical defects that may be
caused by trauma, pathological disease, surgical intervention or
other situations where defects need to be managed in osseous
surgery. It is important to have the defect filler in the form of a
stable, viscous putty to facilitate the placement of the bone
growth medium into the surgical site which is usually uneven in
shape and depth. The surgeon will take the putty on a spatula or
other instrument and trowel it into the site, or take it in his/her
fingers to shape the bone inducing material into the proper
configuration to fit the site being corrected.
[0003] The bone putty preferably provides various other features in
addition to filling a bone void or defect. For example, in some
situations, it is important to provide a secure site for attachment
of items such as bone screws. Because cancellous bone is very
porous, it does not provide a secure foundation for the attachment
of bone repair devices such as bone screws. It is also important
that the defect filler be biocompatible and not cause any
additional trauma at the surgical site.
[0004] Another desirable feature for bone putty is the ability to
control bleeding during bone surgery. Earlier forms of bone putty,
such as those based on bone wax, provide a useful hemostatic
effect, but can interfere with subsequent healing of the bony
tissues, and can also cause other problems such as
inflammation.
[0005] Some existing bone putty materials include materials such as
ceramics or demineralized bone matrix that help stimulate bone
repair. However, including these materials can make the bone putty
less viscous and less able to remain positioned inside the bone,
and can also interfere with the ability of the bone putty material
to fill in small bone pores. Accordingly, there remains a need for
more effective bone putty materials that address one or more of the
deficiencies of the bone putty materials that are currently
available.
SUMMARY OF THE INVENTION
[0006] In one aspect, the present invention provides a bone pore or
void filling composition. The composition includes a mixture of: a
type I collagen and/or a type I collagen-glycosaminoglycan
coprecipitate; a blend of polyethylene glycol polymers having
different molecular weights; tricalcium phosphate; and bioactive
glass. In some embodiments, the tricalcium phosphate comprises
particles having a size from 50 to 300 microns. In additional
embodiments, the tricalcium phosphate comprises from 15% to 30% by
weight. In further embodiments, the bioactive glass comprises
particles having a size from 50 to 300 microns. In additional
embodiments, the bioactive glass comprises from 3% to 7.5% by
weight.
[0007] In some embodiments, the blend of polyethylene glycol
polymers in the composition consists of a first and a second
polyethylene glycol polymer having different molecular weights. For
example, in some embodiments, the first polyethylene glycol polymer
has molecular weight within the range of 1350 g/mol to 1650 g/mol
and the second polyethylene glycol polymer has a molecular weight
within the range of 350 g/mol to 650 g/mol.
[0008] The bone pore or void filling composition includes a mixture
of: a type I collagen and/or a type I collagen-glycosaminoglycan
coprecipitate. In some embodiments the bone pore filling
composition comprises a type I collagen, while in other
embodiments, the bone pore filling composition comprises a type I
collagen-glycosaminoglycan coprecipitate. In further embodiments,
the weight percent of the type I collagen or the type I
collagen-glycosaminoglycan coprecipitate is from 0.2% to 1.5%.
[0009] Another aspect of the invention provides a method of filling
a bone pore or void, comprising administering a bone pore or void
filling composition to the site of the bone pore or void. The
composition includes a mixture of: a type I collagen and/or a type
I collagen-glycosaminoglycan coprecipitate; a blend of polyethylene
glycol polymers having different molecular weights; tricalcium
phosphate; and bioactive glass.
[0010] The method includes various different methods of applying
the composition to various different types of bone pores or voids.
In some embodiments, the composition is manually applied to the
bone pore or void, while in other embodiments the composition is
applied to the bone pore or void using a syringe. In further
embodiments, the composition is applied to a bone pore, or a
plurality of bone pores, each having a diameter from 75 microns to
350 microns. In some embodiments, the composition is applied to a
bone pore in spongy bone, while in other embodiments the
composition is applied to a natural bone void. An advantage of the
bone pore and void filling composition is that it is highly
lubricative and quickly resorbs, leaving tricalcium phosphate and
bioactive glass particles in the bone pores to induce and sustain
bone growth.
[0011] Another aspect of the invention provides a bone pore or void
filling kit. The kit includes a bone pore filling composition,
comprising a mixture of: a type I collagen and/or a type I
collagen-glycosaminoglycan coprecipitate; a blend of polyethylene
glycol polymers having different molecular weights; tricalcium
phosphate; and bioactive glass. The kit also includes a syringe for
administering the bone pore filling composition; and a sterile
package for holding the bone pore filling composition and the
syringe. In some embodiments, the kit also includes instructions
for filling a bone pore. The bone pore or void filling composition
used can include any of the features described herein. For example,
in some embodiments, the blend of polyethylene glycol polymers
consists of a first and a second polyethylene glycol polymer having
different molecular weights.
BRIEF DESCRIPTION OF THE FIGURES
[0012] FIG. 1 provides an image of a bone putty implant placed
within a rabbit leg.
[0013] FIG. 2 provides images showing the results using MGP at 6
weeks for coronal and sagittal bone sections evaluated using
microCT.
[0014] FIG. 3 provides images showing the results using Uni-FuZe-P
at 6 weeks for coronal and sagittal bone sections evaluated using
microCT.
[0015] FIG. 4 provides images showing the results using MGP at 12
weeks for coronal and sagittal bone sections evaluated using
microCT.
[0016] FIG. 5 provides images showing the results using Uni-FuZe-P
at 12 weeks for coronal and sagittal bone sections evaluated using
microCT.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present invention provides a composition for bone pore
or void filling. The composition includes a mixture of: a type I
collagen and/or a type I collagen-glycosaminoglycan coprecipitate;
a blend of polyethylene glycol polymers having different molecular
weights; a bone growth stimulator; and bioactive glass. The
invention also includes a kit for containing the bone pore or void
filling composition, and methods for using the composition to fill
a bone pore or void.
[0018] The terminology as set forth herein is for description of
the embodiments only and should not be construed as limiting of the
invention as a whole. Unless otherwise specified, "a," "an," "the,"
and "at least one" are used interchangeably. Furthermore, as used
in the description of the invention and the appended claims, the
singular forms "a", "an", and "the" are inclusive of their plural
forms, unless contraindicated by the context surrounding such.
[0019] Also herein, the recitations of numerical ranges by
endpoints include all numbers subsumed within that range (e.g., 1
to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).
[0020] As used herein, the term "about," when referring to a value
or to an amount of mass, weight, time, volume, concentration or
percentage is meant to encompass variations of in some embodiments
.+-.20%, in some embodiments .+-.10%, in some embodiments .+-.5%,
in some embodiments .+-.1%, in some embodiments .+-.0.5%, and in
some embodiments .+-.0.1% from the specified amount, as such
variations are appropriate to perform the disclosed method.
[0021] The terms "comprises," "comprising," "includes,"
"including," "having" and their conjugates mean "including but not
limited to". This term encompasses the terms "consisting of" and
"consisting essentially of".
[0022] The phrase "consisting essentially of" means that the
composition or method may include additional ingredients and/or
steps, but only if the additional ingredients and/or steps do not
materially alter the basic and novel characteristics of the claimed
composition or method.
[0023] The conjunctive phrase "and/or" indicates that either or
both of the items referred to can be present.
[0024] A "subject," as used herein, can be any animal, and may also
be referred to as the patient. Preferably the subject is a
vertebrate animal, and more preferably the subject is a mammal,
such as a research animal (e.g., a mouse or rat) or a domesticated
farm animal (e.g., cow, horse, pig) or pet (e.g., dog, cat). In
some embodiments, the subject is a human.
[0025] The terms "therapeutically effective" and "pharmacologically
effective" are intended to qualify the amount of each agent which
will achieve the goal of decreasing disease severity while avoiding
adverse side effects such as those typically associated with
alternative therapies. The therapeutically effective amount may be
administered in one or more doses.
[0026] "Biocompatible" as used herein, refers to any material that
does not cause injury or death to a subject or induce an adverse
reaction in a subject when placed in contact with the subject's
tissues. Adverse reactions include for example inflammation,
infection, fibrotic tissue formation, cell death, or thrombosis.
The terms "biocompatible" and "biocompatibility" when used herein
are art-recognized and mean that the material is neither itself
toxic to a subject, nor degrades (if it degrades) at a rate that
produces byproducts at toxic concentrations, does not cause
prolonged inflammation or irritation, or does not induce more than
a basal immune reaction in the host.
[0027] As used herein, "putty" refers to a dough-like/clay-like
composition that is readily malleable when pressure is applied, but
which generally retains its shape when pressure is not being
applied.
[0028] As used herein, "treatment" means any manner in which the
symptoms of a defect, condition, disorder, or disease, or any other
indication, are ameliorated or otherwise beneficially altered.
Bone Pore or Void Filling Composition
[0029] In one aspect, the present invention provides a bone pore or
void filling composition. The composition includes a mixture of: a
type I collagen and/or a type I collagen-glycosaminoglycan
coprecipitate; a blend of polyethylene glycol polymers having
different molecular weights; a bone growth stimulator; and
bioactive glass. The bone pore or void filling composition has a
putty consistency that provides many benefits such as enhanced
cohesiveness, ease of handling and moldability. Because materials
of the present invention are cohesive, they are also believed to
provide the benefit of maintaining an active compound at the site
of implantation longer than comparative materials with less
cohesiveness.
[0030] Long bones are composed of a dense outer cortical bone (also
called compact bone), which encloses an irregular medullary space
or cavity containing cancellous bone. The cortical bone is a dense
and compact bone that generally has a higher mineral content than
cancellous bone and higher stiffness and strength. The cancellous
bone (also called spongy bone or trabecular bone) is composed of a
branching network of interconnecting bony trabecular elements
(pores) and contains cells that have osteogenic potential.
[0031] When bone is damaged as a result of trauma (e.g., from
accident or surgery), bone pores can be exposed as a result of the
compact bone layer being damaged and exposing the lower spongy bone
layer. The exposure of bone pores can create a problem with regard
to bone repair, because the pores lack many of the features of
cortical bone that contribute to bone repair. Compact bone is made
of special cells called osteocytes that are lined up in rings
around the canals, which together form osteons, which play a role
in bone repair. Once exposed, it can be difficult for cortical bone
to reform over the site of bone injury. In addition, porous bone is
fragile and provides a poor attachment site for certain bone repair
devices such as bone screws. Accordingly, there is a need to be
able to fill bone pores with a material such as bone putty in order
to facilitate bone healing and the attachment and integration of
bone repair devices.
[0032] The bone pore or void filling composition includes a blend
of polyethylene glycol polymers having different molecular weights.
Polyethylene glycol is a polyether polymer, also known as
polyethylene oxide and polyoxyethylene, depending on its molecular
weight. Typically, this is the main material included in the bone
pore and void filling composition, by weight. In some embodiments,
the bone pore or void filling composition includes 50% to 90%
polyethylene glycol by weight, while in other embodiments the
composition includes 60% to 85% polyethylene glycol by weight, or
70% to 80% polyethylene glycol by weight.
[0033] In some embodiments, the blend of polyethylene glycol
polymers consists of a first and a second polyethylene glycol
polymer having different molecular weights. For example, the first
polyethylene glycol polymer can have a molecular weight that is 2.5
to 3.5 larger than the molecular weight of the second polyethylene
glycol polymer. In a further embodiment, the first polyethylene
glycol polymer has a molecular weight within the range of 1250
g/mol to 1750 g/mol and the second polyethylene glycol polymer has
a molecular weight within the range of 250 g/mol to 750 g/mol.,
while in an additional embodiment the first polyethylene glycol
polymer has a molecular weight within the range of 1350 g/mol to
1650 g/mol and the second polyethylene glycol polymer has a
molecular weight within the range of 350 g/mol to 650 g/mol, while
in a yet further embodiment the first polyethylene glycol polymer
has a molecular weight within the range of 1450 g/mol to 1550 g/mol
and the second polyethylene glycol polymer has a molecular weight
within the range of 450 g/mol to 550 g/mol.
[0034] The bone pore or void filling composition includes collagen
and/or a type I collagen-glycosaminoglycan coprecipitate. Collagen
is the major protein component of bone, cartilage, skin, and
connective tissue in animals. Collagen occurs in several types,
having differing physical properties. The most abundant types are
Types I, II and III. Collagen derived from any source is suitable
for use in the compositions of the present invention, including
insoluble collagen, collagen soluble in acid, in neutral or basic
aqueous solutions, as well as those collagens that are commercially
available. Typical animal sources for collagen include but are not
limited to recombinant collagen, fibrillar collagen from bovine,
porcine, ovine, caprine, avian, and shark sources as well as
soluble collagen from sources such as cattle bones and rat tail
tendon. In some embodiments, the collagen is obtained from corium,
which is a base material from which collagen is extracted.
[0035] Type I collagen is the most abundant collagen of the human
body which forms large, eosinophilic fibers known as collagen
fibers. The COL1A1 gene produces the pro-alpha1(I) chain. This
chain combines with another pro-alpha1(I) chain and also with a
pro-alpha2(I) chain (produced by the COL1A2 gene) to make a
molecule of type I procollagen. Type I collagen is present in scar
tissue, as well as tendons, ligaments, the endomysium of
myofibrils, the organic part of bone, the dermis, the dentin and
organ capsules.
[0036] The collagen included in the bone pore and void filling
composition can be in the form of small flakes, particles, or
fibers. Small flakes or particles can be obtained by milling a
collagen sponge, or other form of collagen having a reticulated
cellular structure. For example, in some embodiments, the collagen
comprises fine flakes or particles obtained by milling collagen
through a 10, 20, or 30 mesh screen. A preferred size is obtained
by milling collagen through a 20 mesh screen.
[0037] The collagen included in the bone pore or void filling
composition can be type I collagen and/or a type I
collagen-glycosaminoglycan coprecipitate. In some embodiments,
where both are present, the ratio of type I collagen to type I
collagen-glycosaminoglycan coprecipitate ranges from about 0.5:1 to
about 2:1. In further embodiments, the ratio of type I collagen to
type I collagen-glycosaminoglycan coprecipitate ranges from about
0.8:1 to about 1.5:1. In further embodiments, the type I collagen
is present in a ratio of about 1:1 compared with type I collagen
glycosaminoglycan coprecipitate.
[0038] The amount of type I collagen and/or type I
collagen-glycosaminoglycan coprecipitate included in the bone pore
and void filling composition can vary from about 0.1% to about 10%
by weight. In some embodiments, the composition includes from 0.1%
to 5% collagen and/or type I collagen-glycosaminoglycan
coprecipitate by weight, in further embodiments, the composition
includes from 0.2% to 1.5% collagen and/or type I
collagen-glycosaminoglycan coprecipitate by weight, in yet further
embodiments, the composition includes from 0.3% to 1% collagen
and/or type I collagen-glycosaminoglycan coprecipitate by
weight.
[0039] The bone pore and void filling composition can also include
a type I collagen-glycosaminoglycan coprecipitate. The type I
collagen-glycosaminoglycan coprecipitate is formed when collagen is
precipitated from acid dispersion by addition of a GAG such as
chondroitin 6-sulfate. The relative amount of GAG in the
coprecipitate varies with the amount of GAG added and with the pH.
Yannas et al., J Biomed Mater Res., 14(2):107-32 (1980). The
coprecipitate is predominantly collagen. In some embodiments, the
type I collagen glycosaminoglycan coprecipitate comprises a ratio
of glycosaminoglycan to type I collagen from between 1 to 8 and 1
to 15. In further embodiments, the type I collagen
glycosaminoglycan coprecipitate comprises a ratio of
glycosaminoglycan to type I collagen from between 1 to 10 and 1 to
12. In some embodiments, the ratio is about 1 to 11.
[0040] The term glycosaminoglycan (GAG) describes
hexosamine-containing polysaccharides. Glycosaminoglycans are also
referred to as mucopolysaccharides. Chemically, GAG are alternating
copolymers made up of residues of hexosamine that are
glycosidically bound and alternating in a more or less regular
manner with either hexuronic acid or hexose moieties.
Glycosaminoglylcans can be obtained from various marine and
mammalian sources.
[0041] Examples of glycosaminoglycan molecules that can be included
in the bone pore or void filling composition include hyaluronic
acid and chondroitin sulfate. Various forms of GAG which may be
suitable for use in the bone pore or void filling composition
include, but are not limited to, hyaluronic acid, chondroitin
6-sulfate, chondroitin 4-sulfate, heparin, heparin sulfate, keratin
sulfate and dermatan sulfate. In some embodiments, the
glycosaminoglycan included in the bone repair composition is
chondroitin 4 sulfate or chondroitin 6 sulfate.
[0042] The bone pore or void filling composition also includes a
bone growth stimulator (e.g., tricalcium phosphate). In some
embodiments, the bone growth stimulator (e.g., tricalcium
phosphate) comprises from 5% to 50% by weight, from 10% to 40% by
weight, from 15% to 30% by weight, or from 15% to 25% by
weight.
[0043] Suitable bone growth stimulators include substances that can
enhance filling of the bone pore or voids and encouraging
integration and regrowth of surrounding bone. Some examples of bone
growth stimulators include, but are not limited to, calcium,
hydroxyapatite, tricalcium phosphate, chitosan, coral derivatives,
bone growth factors, such as for example bone morphogenic proteins,
and the like. Hydroxyapatite includes
Ca.sub.10(PO.sub.4).sub.6(OH).sub.2, and is exogenous calcium
phosphate that resembles the primary inorganic component of bone.
This agent provides an osteophillic matrix for bone to bond and
grow. A preferred bone growth stimulator for inclusion in the bone
repair composition is tricalcium phosphate
(Ca.sub.3(PO.sub.4).sub.2). This term also includes sources or
variants of tricalcium phosphate, such as bone ash, alpha or beta
tricalcium phosphate, and combinations thereof.
[0044] The bone growth stimulator (e.g., tricalcium phosphate) is
included in the bone pore and void filling composition as small
particles. Preferably, the particles have a size that allows them
to readily fit within bone pores. In some embodiments, the
particles have a size from 10 to 1000 microns. In other
embodiments, the particles have a size from 25 to 500 microns. In
further embodiments, the particles have a size from 50 to 300
microns. In yet further embodiments, the particles have a size from
50 to 200 microns. In additional embodiments, the particles have a
size from 100 to 200 microns.
[0045] The bone pore and void filling composition also includes
bioactive glass. Bioactive glass is glass that is glass that
undergoes specific surface reactions when implanted into a subject
that facilitates integration and biocompatibility of the material.
For example, in some embodiments the bioactive glass develops a
hydroxyapatite surface layer upon implantation that facilitates the
formation of a firm bond with hard and soft tissues. Bioactive
glass is commercially available from companies such as
Prosidyan.RTM. and the Mo-Sci Corporation. Bioactive glass is based
on Silicon Dioxide (SiO.sub.2) but also typically includes lesser
amounts of Calcium Oxide (CaO), Sodium Oxide (Na.sub.2O), and
Phosphorus Pentoxide (P.sub.2O.sub.5)
[0046] Embodiments of the bone pore and void filling composition
can include varying amounts of the bioactive glass. In some
embodiments, the bone pore and void filling composition includes
from 1% to 15% bioactive glass by weight. In other embodiments, the
bone pore and void filling composition can include 1% to 10%
bioactive glass by weight. In other embodiments, the composition
includes from 2% to 10% bioactive glass. In other embodiments, the
composition includes from 3% to 7.5% bioactive glass, while in
further embodiments, the composition includes from 4% to 6%
bioactive glass.
[0047] The bioactive glass is included in the bone pore and void
filling composition as small particles. Preferably, the particles
have a size that allows them to readily fit within bone pores. In
some embodiments, the bioactive glass and the tricalcium phosphate
particles will be selected to have the same size. In some
embodiments, the particles have a size from 10 to 1000 microns. In
other embodiments, the particles have a size from 25 to 500
microns. In further embodiments, the particles have a size from 50
to 300 microns. In yet further embodiments, the particles have a
size from 50 to 200 microns. In additional embodiments, the
particles have a size from 100 to 200 microns.
[0048] The pH of blood plasma typically is 7.3 to 7.4. Thus, it is
preferable to maintain the pH of the bone pore and void filling
composition, which is in intimate contact with blood, at a
biocompatible pH 7.2-7.4. The pH of the bone pore or void filling
composition can be adjusted using various buffers known to those
skilled in the art, such as a phosphate buffer. It is important to
note that the body has many complex and redundant mechanisms to
maintain its biochemical balance. The blood pH can be adjusted by
several means to its normal, physiologic pH. Hence the presence of
a bone putty at the site of a bleeding bone wound will eventually
be overcome and any non-biocompatible condition will return to
normal pH. However, it is preferable that the bone putty start out
and maintain physiologic pH without stressing the body's
biochemical mechanisms when the bone pore or void filling
composition is applied at the site of the bone void or pores.
[0049] The bone pore and void filling composition can further
comprise bioactive molecules to facilitate bone repair or have
other beneficial effects. Suitable bioactive molecules include, but
are not limited to, growth factors, anti-inflammatory agents, wound
healing agents, anti-scarring agents, antimicrobial agents (for
example, silver), cell-adhesion peptides including Arg-Gly-Asp
(RGD) containing peptides, nucleic acids, nucleic acid analogues,
proteins, peptides, amino acids, and the like, or combinations
thereof.
[0050] In some embodiments, the bone pore or void filling
composition further comprises a hemostatic agent. Hemostatic agents
include, but not limited to, prothrombin, thrombin, fibrin,
fibronectin, Factor X/Xa, Factor VII/VIIa, Factor IX/IXa, Factor
XI/XIa, Factor XII/XIIa, factor XIII, factor VIII, vitronectin,
tissue factor, proteolytic enzyme obtainable from snake venom such
as batroxobin, von Willebrand Factor, plasminogen activator
inhibitor, platelet activating agents, synthetic peptides having
hemostatic activity, collagen particles, derivatives of the above
or any combination thereof. These hemostatic agents can enhance
clotting. In some embodiments, the hemostatic agent comprises
gelatins, collagens, oxidized celluloses, thrombin and fibrin
sealants, chitosan, synthetic glues, glutaraldehyde-based glues, or
a combination thereof. In addition, it should be noted that
collagen particles can also provide a hemostatic effect.
[0051] The bone pore and void filling composition can be treated to
sterilize or to reduce bioburden of the material. For example,
sterilization procedures can include low dose irradiation,
antibiotic washing and physical debridement. These methods provide
the benefit of reducing antigenicity as well as sterilizing the
bone pore and void filling composition. More extensive
sterilization can be provided through gamma irradiation, electron
beam irradiation, or ethylene oxide treatment.
[0052] Processes for producing bone pore or void filling
compositions as a putty are not generally limited and include those
methods known in the art. In one embodiment, the components (i.e.,
the type I collagen and/or a type I collagen-glycosaminoglycan
coprecipitate; a blend of polyethylene glycol polymers having
different molecular weights; tricalcium phosphate; and bioactive
glass) are combined. In some embodiments, the polyethylene glycol
polymers are combined first by, for example, blending them in a
jacketed mixer. The polyethylene glycol polymers can then be melt
blended, after which the tricalcium phosphate and bioactive glass
are introduced. The mixture is then quenched. The mixed/quenched
putty can then be expressed into open ended syringes or otherwise
packaged for later use. As a putty, the composition desirably has
suitable rheological properties (e.g., viscosity) so as to be
injectable through applicators including large gauge applicators,
such as catheters, or syringes, while largely remaining at the
implant site.
Methods of Filling a Bone Pore or Void
[0053] Another aspect of the invention provides a method of filling
a bone pore or void. The method includes administering a bone pore
or void filling composition, as described herein, to the site of a
bone pore or void. When being applied to bone pores, the
composition is typically applied to a bone pore in spongy bone,
which is significantly more porous than compact bone. The putty is
gently packed in these areas without required hydration.
[0054] The bone pore or void filling composition can be applied to
bone pores and/or bone voids. Bone pores are small holes that form
a network of channels within the bone. The pores serve to reduce
the weight of the bone, while maintaining structure and allowing
vascularization. Bone pores can range in size from 10 .mu.m to 600
.mu.m. Typically, cancellous bone (i.e., spongy bone) has 75-85%
porosity with 300-600 .mu.m diameter pores, while cortical bone
(i.e., compact bone) has 5-10% porosity with 10-50 .mu.m diameter
pores. It is preferable that the particles of bone growth
stimulator (e.g., tricalcium phosphate) and bioactive glass
included in the bone putty composition have a size smaller than the
pores so that they can fill the pores while providing a smooth
surface for bone regrowth. In some embodiments, the bone pores have
a diameter of 50 to 400 microns, while in other embodiments the
bone pores have a diameter from 75 microns to 350 microns, while in
further embodiments the bone pores have a diameter from 100 to 200
microns.
[0055] When the bone pore or void filling composition is applied to
a bone pore, it is typically applied to a plurality of bone pores
present in an area of bone. The bone putty is applied over at least
a portion of an area of bone including a plurality of bone pores.
Typically, the area is an area of spongy bone that has been exposed
as a result of disease, injury, or surgery. When applied to such an
area, the bone putty is typically applied in a thin layer to cover
the area including bone pores. The small particle size of the
bioactive glass and bone growth stimulator (e.g., tricalcium
phosphate) allows the particles to settle within the pores,
increasing the smoothness and the effectiveness of the resulting
layer.
[0056] In some embodiments, the composition is manually applied to
the bone pore or void. For example, the bone pore and void filling
composition can be applied using the finger of an individual who is
operating on the subject having bone pores or voids that need to be
filled. The blend of polyethylene glycol polymers is temperature
sensitive, and manual application provides sufficient body heat to
activate the putty to become more grease-like for application. Bone
pore or void filling composition can be administered directly to
the site of the bone pore or void. For example, the bone repair
composition can be packed into bony voids. In some embodiments, the
bone repair composition can be molded or formed into a desired
shape generally conforming to the shape and size of the defect
site, and then positioned or pressed, either manually and/or using
instrumentation, into the defect site.
[0057] Before application, the "putty" substance may be beaten or
kneaded to the consistency of dough, and manipulated into a shape
closely approximating that of the repair site. Putty provides ease
of use and economy of product manufacture. Putties are desirable
for surgical bone repair as they can be easily delivered to
difficult surgical sites and molded in situ into desired shapes.
These products are desirable for the reconstruction of skeletal
defects, e.g., in spine, dental, and/or other orthopedic
surgeries.
[0058] In some embodiments, the composition is applied to the bone
pore or void using a syringe. The bone putty or void filling
composition is readily malleable and injectable. "Injectable"
refers to the ability of bone pore or void filling compositions to
be introduced at a repair site under pressure (as by introduction
using a syringe or other cannulated device). Examples of suitable
syringes include the Merit 20SL open end syringe, and the Merit
Closed end syringe, available from MERITMEDICAL.RTM.. If the
composition is injectable, the composition may be loaded into the
barrel of a disposable syringe, with or without a cannula (e.g.,
needle) attached, and is extruded through the barrel aperture to
the desired anatomical site. An injectable composition of the
present invention may, for example, be introduced between elements
or into a confined space in vivo (e.g., between pieces of bone or
into the interface between a prosthetic device and bone, into a
tooth extraction socket, into alveolar ridge/sinus cavity, into a
confined void with any geometry due to trauma created either
natural or surgical procedure, into vertebral interbody spaces,
spinal fusions, joint and trauma defects, bone fractures. An
injectable composition may also be used to fill bone cysts, tumors
and other well-delineated voids
[0059] In accordance with the methods of the invention, a defect
site is desirably prepared to expose healthy bleeding bone,
facilitating subsequent bone growth. The methods may be performed
using minimally invasive procedures known to one skilled in the
art. The methods may be used in at least partially filling bone
pores or voids of the skeletal system. Such applications include
induction of bone formation for hip replacement operations, knee
replacement operations, spinal fusion procedures, repair of
periodontal defects, treatment of osteoporosis, repair of bone
tumor defects, dental procedures, repair of cranial maxilla facial
defects, and repair of bone fractures or defects. The pores or
voids may be a result of a development failure, degeneration or
trauma, either natural or by surgical creation. The bone pore or
void filling composition is resorbed by the body during the healing
process (over days, weeks, and months).
[0060] The bone pore or void filling composition can be used to
promote bone growth and/or bone remodeling, including in the
treatment of any of a variety of bone diseases, disorders, defects
or injuries for which other bone grafts, including allografts or
autografts, have been employed. Such diseases, disorders, defects
or injuries are well known to a skilled artisan. The subject for
treatment can be any animal subject that has a bone disease,
disorder, defect or injury and is in need of treatment, including
any mammal, such as a human or non-human primate. In particular
examples, the subject is a human. The bone pore or void filling
composition can be used to fill or partially fill areas including
bone pores or bone voids and/or gaps of the skeletal system
associated with the bone disease, disorder, defect or injury.
[0061] In some embodiments, the bone putty composition is applied
to a bone void. Bone voids are gaps in the bone structure that are
significantly larger than bone pores, and are typically the result
of trauma or surgery on the bone. For example, the bone pore or
void filling compositions described herein can be used to correct
bone defects in orthopedic, neurosurgical plastic or reconstructive
surgery, in periodontal procedures, and in endodontic procedures.
Such applications include, but are not limited to, induction of
bone formation for hip replacement operations, knee replacement
operations, foot and ankle surgeries (e.g. ankle fusion), spinal
fusion procedures, repair of periodontal defects, treatment of
osteoporosis, repair of bone tumor defects, dental procedures,
repair of cranial maxilla facial defects and repair of bone
fractures or defects. The bone disease, disorder, defect or injury
can result from a developmental failure, or by degeneration or
trauma, caused naturally or by surgery. In some embodiments, the
composition is applied to a natural bone void, which is a bone void
which is caused naturally.
[0062] In some examples, the bone pore or void filling composition
can be used in conjunction with devices employed in the treatment
of bone diseases, defects, disorders and injuries, such as, for
example, orthopedic cage implants, bone screws, ceramics or plates
that can be employed in the spine or in bones to promote bone
growth and fusion. Furthermore, the bone pore or void filling
composition can be used in conjunction with an autologous bone
graft.
Bone Pore and Void Filling Kits
[0063] Another aspect of the invention provides a bone pore or void
filling kit. The kit includes a bone pore filling composition,
comprising a mixture of: a type I collagen and/or a type I
collagen-glycosaminoglycan coprecipitate; a blend of polyethylene
glycol polymers having different molecular weights; a bone growth
stimulator; and bioactive glass; a syringe for administering the
bone pore filling composition; and a sterile package for holding
the bone pore filling composition and the syringe. The bone pore or
void filling composition can include any of the bone pore or void
filling compositions described herein. For example, in some
embodiments, the bone pore or void filling composition includes a
blend of polyethylene glycol polymers consists of a first and a
second polyethylene glycol polymer having different molecular
weights. Kits may include one, two, three or four
receptacle-containers, one of which may be suitable for combination
and/or "hydration" of the components. The kit may further have a
mixing implement such as a spatula, stir rod, etc., a disposable
syringe barrel with or without a cannulated extension (e.g., a
needle) in which to place and deliver the mixed bone pore or void
filling composition.
[0064] In addition to the above components, the subject kits may
further include (in certain embodiments) instructions for filling a
bone pore or bone void using the bone pore or void filling
composition. These instructions may be present in the subject kits
in a variety of forms, one or more of which may be present in the
kit. One form in which these instructions may be present is as
printed information on a suitable medium or substrate, e.g., a
piece or pieces of paper on which the information is printed, in
the packaging of the kit, in a package insert, etc. Yet another
form of these instructions is a computer readable medium, e.g.,
diskette, compact disk (CD), hard drive etc., on which the
information has been recorded. Yet another form of these
instructions that may be present is a website address which may be
used via the internet to access the information at a removed
site.
[0065] As used herein, the term "package" refers to a solid matrix
or material such as glass, plastic, paper, foil and the like
capable of holding the bone repair composition. For example, in
some embodiments, the package comprises high density polyethylene.
Preferable the package is transparent in order to allow the bone
repair composition to be viewed from outside the package. In some
embodiments, the package includes a tray that includes one or more
grip regions to facilitate access to the bone repair composition.
The package should be sterilized before use to provide a sterile
package. The package can be sterilized after the bone pore and void
filling composition and the syringe have been included within the
package to assure that these components are sterile as well.
[0066] The present invention is illustrated by the following
examples. It is to be understood that the particular examples,
materials, amounts, and procedures are to be interpreted broadly in
accordance with the scope and spirit of the invention as set forth
herein.
EXAMPLES
Example 1: Bone Putty Biocompatibility
[0067] A variety of different tests were conducted to evaluate the
biocompatibility of the bone putty described herein. The bone putty
that was evaluated included 4.67 grams of PEG 1450, 2.33 g of PEG
600, 2.40 g of tricalcium phosphate, 0.60 g of bioactive glass, and
0.10 g of collagen, which were mixed to form a putty as described
herein. Tests were conducted to evaluate the cytotoxicity,
sensitization, irritation, acute systemic injection,
material-mediated pyrogenic effects, and implantation at 4
weeks.
Cytotoxicity
[0068] MEM Elution testing was performed by Nelson Laboratories
according to ISO 10993-5: Biological evaluation of medical
devices--Part 5: Tests for In Vitro cytotoxicity. The purpose of
this test is to evaluate the presence of potential toxicants
released from the device when in its final and sterilized form.
Based on the criteria outlined in the standard, devices are
considered cytotoxic if they score greater than 2 on the reactivity
scale. The device was extracted with agitation in 1X MEM with 5%
bovine serum at 37.degree. C. for 72 hours at a ratio of 0.2 g/mL.
Cell culture 6-well plates, seeded with L-929 cells, were incubated
with the unfiltered, neat extract of the test article. Incubations
were maintained at 37.degree. C. for 48 hours with 5% CO.sub.2. The
cells were then studied under a microscope to determine the level
of cytotoxicity. Scores were given from 0-4: "0" being no cell
lysis and "4" being nearly complete cell destruction. The neat
sample of the subject device extract demonstrated a cytotoxic
reaction in the in vitro test system with a score of "4". Based on
acceptance criteria, the device is therefore considered
cytotoxic.
[0069] The cytotoxicity test is a useful biocompatibility test for
possible toxic leachables from material or residual processing. It
is also historically the most sensitive test available and is used
as a screening test for materials, process residuals, and the final
device configuration. This test is used to determine toxic effects
of the device on a cellular level and can help predict the
potential clinical response. In the ANSI/AAMI/ISO 10993-5 Guidance
section 10 it states "Any cytotoxic effect can be of concern.
However, it is primarily an indication of potential for in vivo
toxicity and the device cannot necessarily be determined to be
unsuitable for a given clinical application based solely on
cytotoxicity data." When elevated cytotoxicity results are seen, a
risk assessment should be performed to identify the risk. Then a
risk assessment should look at the toxic potential of the material
or compound to determine the clinical impact. The investigation
should include a review of the procedures to determine the
effectiveness of the test system, additional testing to evaluate
clinical risk of the results, and then a clinical risk assessment
of the toxicity using additional animal testing along with chemical
analysis and analysis of compounds.
[0070] The materials included in the Bone Putty, polyethylene
glycol, tri-calcium phosphate and porous bioactive glass, are all
known to be biocompatible and are often used in the formulation of
bone void fillers. All the in vivo tests performed on the Bone
Putty which demonstrate a more clinically relevant application and
overall effect of the Bone Putty than an in vitro cell culture test
such as the MEM elution assay, showed no evidence of device-related
toxic effects. Moreover, the performed E&L testing and
accompanied toxicological risk assessment addressed any concern for
any chemical compounds detected in the extract of the Bone Putty
and identified that the toxicological risk to the patient is
considered to be low.
[0071] Thus, based upon examination of the Bone Putty, history of
use of the included materials in medical industry, other more
clinically relevant biological endpoints with passing results as
well as the performed chemical characterization with a
toxicological risk assessment, this cytotoxicity failure may not be
clinically relevant and adverse effects in patients are considered
to be unlikely.
Sensitization
[0072] Testing was performed by Toxikon USA according to ISO
10993-10: Biological evaluation of medical devices--Part 10: Tests
for irritation and skin sensitization. The purpose of the study is
to determine the potential allergenic or sensitizing capacity of
the test article. Sensitization testing is conducted in two phases:
induction and challenge. The induction phase has two applications:
injection (on Day 0) and topical (on Day 7). Based on the criteria
outlined in the standard, a device is considered sensitizing if it
achieves a score of .gtoreq.1 on the Magnusson and Kligman grading
scale. Additional sensitization classification or grading scale per
USP is used to define the allergenic potential of the test article
based on the number of responsive animals with observed skin
reactions at any given time point. The material was extracted in
Normal Saline (NS) or Cottonseed Oil (CSO) at 50.degree. C. for 72
hours at a ratio of 0.2 g/mL. Ten test and five control guinea pigs
were injected per extract vehicle with three pairs of 0.1 mL
intradermal injections made in a row on each side of the midline.
The first pair of injections included a 1:1 (v/v) mixture of
Freund's Complete Adjuvant (FCA) with the appropriate
solvent/vehicle, the second pair of injections includes the
appropriate solvent/vehicle with or without the extracted test
article, and the third pair of injections is performed with 1:1
(v/v) mixture of FCA with either the test article extract in an
appropriate solvent/vehicle or just the solvent/vehicle. FCA is
used to potentiate the sensitization reaction and to evaluate the
possibility of hyperreactive skin status during the test and thus
interference with the reading and scoring. On Day 6, the injection
site area was clipped free of fur and treated with 10% (w/w) sodium
lauryl sulfate (SLS) in petrolatum that acts to increase the dermal
response to weak sensitizers. On day 7 after injection, filter
paper saturated with fresh test extract was secured to the skin of
each test animal and filter paper saturated with fresh control
vehicle was secured to the skin of each control animal and left
there for 48 hours. On day 23 after injection, filter paper was
again saturated with fresh test extract or control vehicle. A
control vehicle patch was attached to the left flank of each animal
and test extract patch was attached to the right flank of each
animals. The patch was left there for 24 hours and scoring was
performed at 24, 48 and 72 hours after the patch was removed. The
evaluation of skin reactions used the four-point Magnusson and
Kligman grading scale, and the allergenic potential of the test
article was classified based on the percent of responsive animals
with any skin reaction score of 1 or greater at any time point. The
test group demonstrated no visible change in dermal observations
with 0% animals sensitized for both NS and CSO extracts. Based on
the USP grading, and the calculated allergenic potential of the
test article, the device is categorized as a non-sensitizer.
Irritation
[0073] Testing was performed by Toxikon USA according to ISO
10993-10: Biological evaluation of medical devices--Part 10: Tests
for irritation and skin sensitization. The purpose of this test is
to determine the potential irritation effects of the test article
extract as a result of an intracutaneous injection to evaluate
whether the device stimulates a local irritation response in the
dermal tissues. Based on the criteria outlined in the standard, a
device is considered an irritant if the comparative result (the
average score of the test animals, minus the average score of the
control animals) is greater than 1. The device was extracted in NS
or CSO at 50.degree. C. for 72 hours at a ratio of 0.2 g/mL. A
volume of 0.2 mL per site of one extract was injected
intracutaneously at one side of each three rabbits, with fine sites
for the test article extract and five posterior sites for the
control. Similarly, at the other side of each rabbit, the other
test extract was injected. Appearance of each injection site was
observed for signs of erythema and edema, and scored based on the
classification system for scoring skin reactions immediately
following injection, and at 24, 48, and 72 hours post injection.
The overall mean score difference between the control and the test
article were 0.0 for both NS and CSO extracts. The device is
therefore considered a non-irritant.
Material Mediated Pyrogen
[0074] Testing was performed by Toxikon USA according to the United
States Pharmacopeia (USP) Pyrogen Test Procedure. The purpose of
the study was to determine the potential presence of chemical
pyrogens in the extracts of solid materials in order to limit to an
acceptable level the risks of febrile reaction following
administration of the product to the patient. The study involved
measuring the rise in temperature of rabbits following the
intravenous injection of the test article extract. The test article
was extracted in 0.9% NS at 50.degree. C. for 72 hours at a ratio
of 0.2 g/mL. The test extract was injected into the marginal ear
vein of each of the three animals; additionally, one animal was
injected with the vehicle control. All animals received a 10 mL/kg
dose of the test article. Rectal temperatures were recorded for
each animal prior to injection and between 1 and 3 hours
post-injection at 30 minute intervals. During the 3 hour
observation period, none of the rabbits administered with the test
article extract had a temperature rise .gtoreq.0.5.degree. C. at
the required observation time points. This response did not exceed
the USP limit and meets the requirements for this test. Therefore,
these results indicate that the test article was determined to be
non-pyrogenic.
Acute Systemic Toxicity
[0075] Testing was performed by Toxikon USA according to ISO
10993-11: Biological evaluation of medical devices--Part 11: Tests
for systemic toxicity. The purpose of this study was to determine
the potential toxic effects of the test article extract as a result
of a single-dose systemic injection in mice. The device was
extracted in NS or CSO at 50.degree. C. for 72 hours at a ratio of
0.2 g/mL. The NS test article and control extracts were injected
intravenously into five mice each. The CSO test article and control
extracts were injected intraperitoneally into five mice each.
Clinical observations and body weight recordings were taken before
injection as well as 24, 48, and 72 hours after injection. Based on
the criteria outlined the standard, a device is considered toxic if
death in two or more mice occurs or other toxic signs such as
convulsions, prostration, or body weight loss greater than 10% in
three or more mice. At the 4-hour time point NS test animal #3 was
found dead. A gross necropsy was performed with no abnormal
findings. None of the other test or control animals exhibited overt
signs of toxicity at any of the observation time points. Per
Section 9.2 of the report "A gross necropsy was performed with no
abnormal findings". Based on this and the fact that the rest of the
test animals were normal throughout the duration of the test, the
testing facility determined that the death of one test animal
during the study was an isolated event and does not reflect the
effect of the test article on the animal. The device was therefore
considered non-toxic.
4 Week Bone Implantation
[0076] Testing was performed by American Preclinical Services (APS)
according to ISO 10993-6: Biological evaluation of medical
devices--Part 6: Tests for local effects after implantation.
Implantation study for the Bone Putty included five test animals,
each receiving two test articles in one tibia, and two control
articles in the other tibia. The standard requires that a minimum
of three animals are to be used. Implants should be planned to
obtain 10 control and 10 test article implant sites for
examination. At the completion of the study, all of the animals on
study were euthanized and necropsy was performed for target tissue
procurement. Implant sites were explanted, fixed, and embedded. The
embedded specimens underwent histopathological interpretation to
evaluate cell type presence and tissue response to test and control
articles. Clinical, macroscopic and microscopic observations were
also made throughout the study.
[0077] There were no signs of infections associated with any of the
implant sites. All animals were in overall good health over the
course of the study except for one animal, which exhibited an
approximately 0.5-1.0.times.1.0 cm soft swelling on the medial
ventral abdomen during study days 2-28. There were no notable gross
findings, no abnormalities observed in four out of five animals.
One animal exhibited multifocal smooth, firm white subcutaneous
masses at one set of implant sites and smooth, purple intramuscular
discoloration at the other set of implant sites. These appeared to
be related to the surgical procedure. Per the pathology report, the
test articles implant sites had narrow to moderately thick bands of
fibrous connective tissue containing few fibrocytes, whereas the
control sites had narrow to thick bands of fibrous connective
tissue containing few fibrocytes. There were rare to mild
multifocal infiltrates of inflammatory cells composed primarily of
macrophages at test article implant sites. Minimal multifocal
neovascularization was noted in two out of nine sections examined
in the test articles sites; in control sites, minimal to mild
multifocal neovascularization was noted in two out of ten sections
examined. Necrosis and fatty infiltration was not noted in any the
examined sections for test article and control sites. The
conclusion of the study is based on the scores assigned by the
pathologist during the microscopic evaluation. The average
irritancy score per implant site was evaluated as 5.8 for the
control site and 5.1 for the test site. The resulting overall
irritant ranking score for the 4 week implant study indicates the
test article is considered to have a minimal or no reaction to the
tissue. Detailed information on the scores and scoring criteria are
contained in the final report.
[0078] It should be mentioned that only nine test article implanted
sites were scored, which is a deviation from the standard that
required 10 sites to be scored. It is noted in the report that
while all 10 test implant sites were identified and recovered, one
of the test Implant sites was not available for evaluation. The
nine evaluable test slides, however, afforded the study pathologist
an accurate overall evaluation. Thus, even though the standard
requires the analysis of 10 test article site, since the nine
evaluated sites showed consistent low tissue reactivity, the
results obtained in the study are considered valid for the test
article.
Example 2: Bone Putty Efficacy
[0079] The current study examined the in vivo performance of two
bone void filler materials, Uni-FuZe-P and Mastergraft Putty
(predicate material) in an established rabbit femoral defect model.
Uni-FuZe-P is the same bone putty composition of the present
invention which was also used for the biocompatibility studies
described in Example 1. More specifically, it was a bone putty
composition that included 4.67 grams of PEG 1450, 2.33 g of PEG
600, 2.40 g of tricalcium phosphate, 0.60 g of bioactive glass, and
0.10 g of collagen, The test groups were evaluated for
biocompatibility and osteoconductive healing response using
radiographic, microCT and histological analyses at time points of 1
day, 6, and 12 weeks following surgery.
[0080] Surgical Prep: All animals were prepared for surgical
procedures as per BHRL/ISRC/ARS SOPs. After the pre-anesthetic had
taken effect, rabbits were clipped free of fur over the surgical
areas. The surgical areas were scrubbed with chlorhexidine soap and
wiped with isopropyl alcohol. Betadine solution was applied just
prior to surgical incision.
[0081] A lateral incision, approximately 2.0 centimeters long, was
made and the soft-tissues overlying the femoral condyle dissected.
A 5.0 mm drill bit was used to drill through the cortex to a depth
of 10 mm and bone removed. Drilling was done under constant saline
irrigation. Once bone was removed, graft material was hand-packed
into the defect to the level of the original cortex (.about.0.2 cc)
or left empty. Fascia and skin were closed in the routine manner
consistent with good surgical practice. This surgical procedure was
conducted on the contralateral limb as well. FIG. 1 provides an
image of the implant placed within a rabbit leg.
[0082] No complications were observed in either test groups over
the course of the study. Gross observations of the implant sites
demonstrated healthy tissue absent of adverse inflammatory
reactions regardless of test group or time point. Radiographic
analysis indicated no adverse reactions and a normal progression in
healing over time in both groups. MicroCT scans supported the
radiographic observations, similar osteoconductive healing response
in both groups, with a progression of new bone formation and
implant resorption observed over time.
[0083] Ventral/dorsal and lateral radiographs were obtained with a
Simon DR (Quantum) RAD-X High Frequency Radiographic Imaging
System, (model: E7242X), and stored using Whitecap PACs system.
Radiographic images were obtained postoperatively and at 1 day, 6,
and 12 weeks post-surgery. Animals received sedation as described
for surgical procedures in Section 6.8 prior to radiography.
Radiographs were examined to confirm graft placement and assess
graft migration, osteolysis, fracture, and/or any other adverse
events.
[0084] Animals were euthanized using Euthasol solution (120 mg/kg
IV). Necropsy was conducted on all study animals according to
BHRL/ISRC standard operating procedures under the supervision of
the PI. Necropsy included examination of the external surface, all
orifices, thoracic, abdominal, and pelvic cavities including
contents. The stifle joint was transected removing the tibia. The
soft tissues were removed from the femoral condyles and a saw was
used to cut the femur just proximal to the condyles (approximately
20 mm from the joint surface). Condyles from the left and right
limbs were placed in 10% neutral buffered formalin.
[0085] Each specimen was scanned using a SkyScan 1176 Micro-CT.
Microtomography uses a similar technique as computerized tomography
systems in medicine (MDCT-scans) but at a higher resolution (as
thin as 9 .mu.m). X-ray images (2D) were acquired in multiple
planes while either the sample or the source/detector pair was
rotated. Internal structures were reconstructed as a series of 2D
cross sections which were then used to analyze the two and three
dimensional morphological parameters of the specimen. Image
acquisition and Reconstruction parameters are shown in Table 6.3.
The SkyScan 1176 was calibrated according to the manufacturers
recommended schedule for contrast, positioning and density. Each
specimen was analyzed for Total Volume (TV), Bone Volume (BV),
Graft Volume (GV), Soft Tissue Volume (SV). Soft Tissue Volume
includes both general soft tissues and void space not detected as
bone or implant (threshold: <58).
[0086] The test groups were comparatively evaluated for host
response, new bone formation and implant resorption within the
healing defects using radiographic, microCT and histological
analyses at time points of 1 day, 6 weeks, and 12 weeks. Gross
observations of the implant sites demonstrated healthy tissue
absent adverse inflammatory reactions regardless of test group or
time point. Radiographic analysis indicated no adverse reactions
and a normal progression in healing over time in both groups.
MicroCT scans supported the radiographic observations,
demonstrating no adverse reactions and a similar osteoconductive
healing response in both groups, with a progression of new bone
formation and implant resorption over time. The results of the
microCT scans are shown in FIGS. 2-5. Uni-FuZe-P was demonstrated
to be osteoconductive, providing a scaffold for cell attachment and
supporting formation of osseous tissue across bony defects.
[0087] This study has confirmed the biocompatibility and normal
osteoconductive healing response associated with the Uni-FuZe-P and
has demonstrated equivalent in vivo performance to the Mastergraft
Putty across radiographic, microCT and histological endpoints in an
established femoral cancellous defect animal model.
[0088] The complete disclosure of all patents, patent applications,
and publications, and electronically available materials cited
herein are incorporated by reference. Any disagreement between
material incorporated by reference and the specification is
resolved in favor of the specification. The foregoing detailed
description and examples have been given for clarity of
understanding only. No unnecessary limitations are to be understood
therefrom. The invention is not limited to the exact details shown
and described, for variations obvious to one skilled in the art
will be included within the invention defined by the claims.
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