U.S. patent application number 17/551305 was filed with the patent office on 2022-07-21 for prosthetic surgical sling systems and methods.
The applicant listed for this patent is Beda B.G. Ruefer, Rebecca U. Ruefer. Invention is credited to Beda B.G. Ruefer, Rebecca U. Ruefer.
Application Number | 20220226092 17/551305 |
Document ID | / |
Family ID | 1000006080196 |
Filed Date | 2022-07-21 |
United States Patent
Application |
20220226092 |
Kind Code |
A1 |
Ruefer; Beda B.G. ; et
al. |
July 21, 2022 |
PROSTHETIC SURGICAL SLING SYSTEMS AND METHODS
Abstract
Disclosed are versions of a prosthetic sling manufactured using
an expanded fluoropolymer, e.g., PTFE. In some versions, a tubular
ePTFE extrusion is, after initially processing, subjected to
moderate temperatures and pressures to flatten the tubular
extrusion such that it has rounded edges. In other versions a
multiaxially expanded ePTFE strip is used.
Inventors: |
Ruefer; Beda B.G.; (Bozeman,
MT) ; Ruefer; Rebecca U.; (Bozeman, MT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ruefer; Beda B.G.
Ruefer; Rebecca U. |
Bozeman
Bozeman |
MT
MT |
US
US |
|
|
Family ID: |
1000006080196 |
Appl. No.: |
17/551305 |
Filed: |
December 15, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
63140052 |
Jan 21, 2021 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C 48/0018 20190201;
B29C 48/09 20190201; B29L 2031/7532 20130101; A61F 2240/002
20130101; A61L 31/06 20130101; B29K 2027/18 20130101; A61L 31/146
20130101; A61F 2/0036 20130101 |
International
Class: |
A61F 2/00 20060101
A61F002/00; A61L 31/06 20060101 A61L031/06; A61L 31/14 20060101
A61L031/14; B29C 48/00 20060101 B29C048/00; B29C 48/09 20060101
B29C048/09 |
Claims
1. A method for producing a surgical implant device, the method
comprising: mixing a polytetrafluoroethylene (PTFE) resin paste
with an extrusion aid; forming the resin paste and the extrusion
aid into a billet; extruding the billet into a PTFE tube; drying
the PTFE tube to remove the extrusion aid; reheating the PTFE tube
at a temperature lower than a melt temperature of the PTFE tube;
expanding the PTFE tube in at least one dimension to create a
node/fibril structure; heating the PTFE tube to a temperature above
a thermal transition temperature for the PTFE thus setting a
node/fibril structure in place resulting in an expanded tube; and
applying heat and pressure to collapse the expanded tube and adhere
the inside tube surfaces together to form a substantially flat
article having rounded lateral edges.
2. The method of claim 1, wherein the expanding the PTFE tube in at
least one dimension step comprises: unidirectionally and
longitudinally expanding the PTFE tube resulting a plurality of
substantially parallel fibrils interconnecting a plurality of nodes
defining a plurality of apertures therebetween, each aperture in
the plurality of apertures having a pore size less than 2
microns.
3. The method of claim 1 comprising: establishing a tube wall
thickness in the extruding step of about 0.20 millimeters.
4. The method of claim 1 comprising: allowing the article to cool
after the restraining step and the applying heat and pressure
step.
5. The method of claim 1 comprising: presenting the article for use
as a supportive surgical implant.
6. The method of claim 1 comprising: configuring the article for
use as a supportive surgical implant.
7. The method of claim 6 comprising: sizing the article to operate
as a supportive surgical implant, and configuring a first end and a
second end of the article to attach to surgical placement aids.
8. The method of claim 6 comprising: configuring the article to
have a length making the article usable as a supportive surgical
implant device having first and second ends.
9. The method of claim 8 comprising: densifying the first and
second ends by the application of elevated heat and pressure making
the ends apt for the receipt of implantation aids.
10. The method of claim 9 comprising: forming apertures into the
first and second ends, the apertures being configured to receive
implantation aids.
11. The method of claim 1 comprising: after setting the node/fibril
structure in place, and before the step of applying heat and
pressure: inserting a meltable filler material into the expanded
tube, and melting the filler material to aid in adhering the inside
tube surfaces together.
12. The method of claim 11 comprising: selecting Fluorinated
Ethylene Propylene (FEP) as the meltable filler.
13. The method of claim 1 wherein the applying heat and pressure
step is executed at a temperature lower than the thermal transition
point of the PTFE.
14. The method of claim 1 wherein the applying heat and pressure
step is executed by: sandwiching the expanded tube between a hot
surface and another surface under moderate pressure; and applying
heat and pressure until porosity is reduced and a now collapsed
tube softens.
15. An article usable as a supportive surgical implant, the article
comprising: a collapsed tube forming an elongated body having a
first end and a second end, rounded lateral edges, the elongated
body being formed of a biocompatible, bacteria-resistant
fluoropolymer material, the fluoropolymer material being configured
to have a plurality fibrils connecting between nodes.
16. The article of claim 15 wherein the biocompatible,
bacteria-resistant fluoropolymer material comprises
Polytetrafluoroethylene (PTFE).
17. The article of claim 16 wherein the bacteria-resistant
fluoropolymer comprises expanded PTFE (ePTFE).
18. The article of claim 17 wherein the plurality of fibrils extend
longitudinally substantially in parallel, and the plurality of
fibrils and plurality of nodes together define a plurality of pores
having sizes of 2 microns or less in smallest dimension.
19. The article of claim 15 wherein the article is configured for
use as a tissue support.
20. The article of claim 19 wherein the article is configured for
use as a pubovaginal sling.
21. The article of claim 19 wherein the first end is configured to
receive a first surgical placement aid, and the second end is
configured to receive a second surgical placement aid.
22. The article of claim 15 wherein the bacteria-resistant
fluoropolymer comprises a microporous structure which is relatively
closed to ingrowth and bacterial penetration.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 63/140,052 filed Jan. 21, 2021, the entire contents
of which are herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field
[0002] The disclosed embodiments relate generally to the field of
prosthetic medical devices. More specifically, the field relates to
the development of prosthetic medical slings implemented for
supporting internal body structures.
2. Description of the Related Art
[0003] Pubovaginal sling procedures are very prevalently used to
offer support needed to stabilize a patient's urethra or bladder.
The most common device used in executing such a process is an
elongated flexible strip constructed of a nonabsorbable
polypropylene mesh material, the ends of which can be anchored
elsewhere in the patient's body, and support is offered to prevent
incontinence.
SUMMARY
[0004] This summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the detailed description. This summary is not intended to identify
key features or essential features of the claimed subject matter,
nor is it intended to be used to limit the scope of the claimed
subject matter. Other aspects and advantages will be apparent from
the following detailed description of the embodiments and the
accompanying drawing figures.
[0005] In embodiments, a medical support device includes an
elongated body comprised of an expanded fluoropolymer. The device
is used to support a body component, e.g., in embodiments, can be
used as a urethral sling or for other like applications. In some
embodiments, the elongated expanded fluoropolymer is
polytetrafluoroethylene (ePTFE). The ePTFE can be formed into a
hollow crushed tube shape. In some of the crushed tube embodiments,
the tube is filled with a co-elongated core within the tube. In
some of the embodiments where the crushed tube includes a core, the
core can be made of fluorinated ethylene propylene (FEP).
[0006] In some aspects, the techniques described herein relate to a
method for producing a surgical implant device, the method
including: mixing a polytetrafluoroethylene (PTFE) resin paste with
an extrusion aid; forming the resin paste and the extrusion aid
into a billet; extruding the billet into a PTFE tube; drying the
PTFE tube to remove the extrusion aid; reheating the PTFE tube at a
temperature lower than a melt temperature of the PTFE tube;
expanding the PTFE tube in at least one dimension to create a
node/fibril structure; heating the PTFE tube to a temperature above
a thermal transition temperature for the PTFE thus setting a
node/fibril structure in place resulting in an expanded tube; and
applying heat and pressure to collapse the expanded tube and adhere
the inside tube surfaces together to form a substantially flat
article having rounded lateral edges.
[0007] In some aspects, the techniques described herein relate to a
method, wherein the expanding the PTFE tube in at least one
dimension step includes: unidirectionally and longitudinally
expanding the PTFE tube resulting a plurality of substantially
parallel fibrils interconnecting a plurality of nodes defining a
plurality of apertures therebetween, each aperture in the plurality
of apertures having a pore size less than 2 microns.
[0008] In some aspects, the techniques described herein relate to a
method including: establishing a tube wall thickness in the
extruding step of about 0.20 millimeters.
[0009] In some aspects, the techniques described herein relate to a
method including: allowing the article to cool after the
restraining step and the applying heat and pressure step.
[0010] In some aspects, the techniques described herein relate to a
method including: presenting the article for use as a supportive
surgical implant.
[0011] In some aspects, the techniques described herein relate to a
method including: configuring the article for use as a supportive
surgical implant.
[0012] In some aspects, the techniques described herein relate to a
method including: sizing the article to operate as a supportive
surgical implant, and configuring a first end and a second end of
the article to attach to surgical placement aids.
[0013] In some aspects, the techniques described herein relate to a
method including: configuring the article to have a length making
the article usable as a supportive surgical implant device having
first and second ends.
[0014] In some aspects, the techniques described herein relate to a
method including: densifying the first and second ends by the
application of elevated heat and pressure making the ends apt for
the receipt of implantation aids.
[0015] In some aspects, the techniques described herein relate to a
method including: forming apertures into the first and second ends,
the apertures being configured to receive implantation aids.
[0016] In some aspects, the techniques described herein relate to a
method including: after setting the node/fibril structure in place,
and before the step of applying heat and pressure: inserting a
meltable filler material into the expanded tube, and melting the
filler material to aid in adhering the inside tube surfaces
together.
[0017] In some aspects, the techniques described herein relate to a
method including: selecting Fluorinated Ethylene Propylene (FEP) as
the meltable filler.
[0018] In some aspects, the techniques described herein relate to a
method wherein the applying heat and pressure step is executed at a
temperature lower than the thermal transition point of the
PTFE.
[0019] In some aspects, the techniques described herein relate to a
method wherein the applying heat and pressure step is executed by:
sandwiching the expanded tube between a hot surface and another
surface under moderate pressure; and applying heat and pressure
until porosity is reduced and a now collapsed tube softens.
[0020] In some aspects, the techniques described herein relate to
an article usable as a supportive surgical implant, the article
including: a collapsed tube forming an elongated body having a
first end and a second end, rounded lateral edges, the elongated
body being formed of a biocompatible, bacteria-resistant
fluoropolymer material, the fluoropolymer material being configured
to have a plurality fibrils connecting between nodes.
[0021] In some aspects, the techniques described herein relate to a
article wherein the biocompatible, bacteria-resistant fluoropolymer
material includes Polytetrafluoroethylene (PTFE).
[0022] In some aspects, the techniques described herein relate to a
article wherein the bacteria-resistant fluoropolymer includes
expanded PTFE (ePTFE).
[0023] In some aspects, the techniques described herein relate to a
article wherein the plurality of fibrils extend longitudinally
substantially in parallel, and the plurality of fibrils and
plurality of nodes together define a plurality of pores having
sizes of 2 microns or less in smallest dimension.
[0024] In some aspects, the techniques described herein relate to a
article wherein the article is configured for use as a tissue
support.
[0025] In some aspects, the techniques described herein relate to a
article wherein the article is configured for use as a pubovaginal
sling.
[0026] In some aspects, the techniques described herein relate to a
article wherein the first end is configured to receive a first
surgical placement aid, and the second end is configured to receive
a second surgical placement aid.
[0027] In some aspects, the techniques described herein relate to a
article wherein the bacteria-resistant fluoropolymer includes a
microporous structure which is relatively closed to ingrowth and
bacterial penetration.
[0028] Regardless of the particular configuration involved, the
elongated medical support device can have first and second ends
both receivable by a placement tool designed to aid with implanting
the device into the human body in a supporting capacity regarding
an internal structure. In some embodiments the device is usable as
a surgical sling.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0029] Illustrative embodiments are described in detail below with
reference to the attached drawing figures, which are incorporated
by reference herein and wherein:
[0030] FIG. 1A shows an overall view for an article in a first
embodiment;
[0031] FIG. 1B shows a cross sectional view taken across the
article from line 1B-1B in FIG. 1A;
[0032] FIG. 1C shows an overall perspective view for an embodiment
of the collapsed tube shown in FIGS. 1A-B configured with
connection mechanisms added to each end;
[0033] FIG. 1D depicts the embodiment of the sling (shown in FIGS.
1A-B) attached to placement aids which might be used for implanting
the article.
[0034] FIG. 1E shows an overall perspective view for an embodiment
which is also a collapsed tube like shown in FIGS. 1A-B, but having
ends which have been densified by heat and pressure to create
relatively dense attachment ends;
[0035] FIG. 2 is a micrograph taken of the article before final
processing; and
[0036] FIG. 3 is a micrograph taken of the material of FIG. 2 after
the material has been finally processed.
[0037] FIG. 4A shows an overall perspective view for a third
embodiment, also a collapsed tube like shown in FIG. 1A-B, but also
having a core made of a second material; and
[0038] FIG. 4B shows a cross sectional view taken from line 4B-4B
in FIG. 4A.
[0039] The drawing figures do not limit the invention to the
specific embodiments disclosed and described herein. The drawings
are not necessarily to scale, emphasis instead being placed upon
clearly illustrating the principles of the invention.
DETAILED DESCRIPTION
[0040] The following detailed description references the
accompanying drawings that illustrate specific embodiments in which
the invention can be practiced. The embodiments are intended to
describe aspects of the invention in sufficient detail to enable
those skilled in the art to practice the invention. Other
embodiments can be utilized and changes can be made without
departing from the scope of the invention. The following detailed
description is, therefore, not to be taken in a limiting sense. The
scope of the invention is defined only by the appended claims,
along with the full scope of equivalents to which such claims are
entitled.
[0041] In this description, references to "one embodiment," "an
embodiment," or "embodiments" mean that the feature or features
being referred to are included in at least one embodiment of the
technology. Separate references to "one embodiment," "an
embodiment," or "embodiments" in this description do not
necessarily refer to the same embodiment and are also not mutually
exclusive unless so stated and/or except as will be readily
apparent to those skilled in the art from the description. For
example, a feature, structure, act, etc. described in one
embodiment may also be included in other embodiments, but is not
necessarily included. Thus, the technology can include a variety of
combinations and/or integrations of the embodiments described
herein.
[0042] Synthetic slings have been available for implant procedures
for many decades. The most common form of sling is constructed of
polypropylene, which is typically comprised of woven or knit
filaments. A polypropylene sling presents open structure which
allows bacteria to penetrate. This can lead to post-operative
infection. Although these devices have been implanted in many
thousands of patients, there remain many post-implantation problems
that have yet to be resolved. Most of these problems are clinically
significant, and can end with surgical retrieval of the devices,
which can lead to further internal tissue damage.
[0043] One problem with these prior art polypropylene mesh slings
is damage that can be caused upon surgical implant. Those skilled
in the art will recognize that during surgery the polypropylene
mesh sling is worked through bodily tissues, e.g., being pushed or
pulled therethrough using needles or other devices. The edges of
these prior art slings may be rough, and when passed through the
body during surgical implant can create tissue damage, e.g., scar
tissue, etc.
[0044] Any limited damage created upon implant of the polypropylene
sling is not necessarily considered a bad thing, in that the damage
causes an immediate inflammatory response, which ultimately helps
incorporate the device structurally. But this damage can compromise
tissues in undesirable ways also.
[0045] Another problem is that the polypropylene mesh degrades over
time. This degradation can result in migration of sling segments or
filaments, or even extrusion of same. These obvious failures create
harm, and often result in the need for removal of an
already-implanted sling by a surgery far more complicated and
potentially harmful than the initial implant procedure, and can
leave behind massive scar tissue, as well as result in chronic pain
moving forward.
[0046] Another problem is that of infection. The vulnerability of
the polypropylene to infection is due in large part to the nature
of the mesh material. Following implant of a conventional
polypropylene mesh sling, it is considered desirable that the
surrounding tissues grow into the device. This ingrowth is seen as
necessary to secure the polypropylene device in place. But this
also makes the device extremely difficult to remove surgically,
e.g., in the case of complications such as infection or structural
degradation over time. Many times, surgery to remove the sling
creates serious problems to the tissues on or around the
implant.
[0047] The invention disclosed herein is a prosthetic medical sling
made of a novel synthetic material, in embodiments, a relatively
closed expanded Polytetrafluoroethylene structure. The inventive
design of the medical device provides for a strong, supportive,
biocompatible sling that resists bacterial invasion and
disintegration.
[0048] The prosthetic sling embodiments disclosed herein overcome
the aforementioned problems significantly.
[0049] More specifically, the embodiments described herein comprise
a novel synthetic prosthetic medical sling that is biocompatible,
resists bacterial infection, exhibits significant long-term
strength to support tissues, does not promote massive scar tissue,
and will not deteriorate over time. Further, the sling embodiments
exhibit strength adequate for intended use, are supple and tissue
compliant to minimize scar tissue formation, and are durable, as
PTFE, a fluoropolymer is known to be resistant to
biodegradation.
[0050] Embodiments are comprised of a processed fluoropolymer, such
as Polytetrafluoroethylene (PTFE). Embodiments disclosed in the
figures herein incorporate expanded PTFE, or "ePTFE" which is
formed by longitudinal expansion under heat. An ePTFE article can
be manufactured to have fibril lengths such that the article is
relatively closed structured to prevent the infiltration of
bacteria yet supple for tissue compliance, and adequately strong
for its intended use as a tissue support device. And of course, as
ePTFE, it is fully biocompatible and will not degrade.
[0051] The micro porous structure of known ePTFE articles is
characterized by a plurality of nodes that are connected together
by a plurality of fibrils. The nodes are essentially solid PTFE,
having a density of about 2.0-2.2 grams per cubic centimeter,
whereas the density of the expanded material is less than about 2.0
grams per cubic centimeter. The shape, size and orientation of the
nodes and fibrils within the structure can be controlled by varying
the expansion rate, expansion ratio, number of expansion axes and
other processing parameters to yield many different structures. It
is also known that properties such as the expandability and
microstructure of the expanded article vary with the molecular
weight, particle size and other physical characteristics of the
PTFE resin.
[0052] The disclosed embodiments of the ePTFE implant device (e.g.,
sling) are configured as (i) a first embodiment comprised of a
collapsed tube (FIGS. 1A and 1B); and (ii) a collapsed-tube
embodiment including a meltable filler (FIGS. 4A and 4B).
[0053] The body of the device in each of the embodiments in FIGS.
1A-1B, and 4A and 4B is made of a relatively closed structure, high
strength, expanded fluoropolymer. The body of the embodiment in
FIGS. 4A and 4B is also made with an expanded fluoropolymer (e.g.,
ePTFE) but then filled with a melt-processable fluoropolymer, e.g.,
fluorinated ethylene propylene (FEP) in embodiments.
[0054] The embodiments above have shown no ingrowth or bacterial
penetration. Thus, they avoid the well-known infection problems
existing in the polypropylene prior art devices. Additionally,
because ingrowth is avoided, surgical removal is relatively easy to
accomplish, if necessary, and leaves little if any scar tissue or
other damage.
[0055] The embodiment 100 is shown in perspective in FIG. 1A. FIG.
1B shows a cross section taken at 1B-1B in FIG. 1A.
[0056] Referring to FIG. 1A, the collapsed-tube embodiment 100
includes a first end 102, a second end 104, and an elongated body
106. The elongated body 106 of the collapsed tube embodiment 100
is, in embodiments, comprised of expanded PTFE, more specifically,
expanded to reflect a node/fibril structure that makes the article
relatively closed to bacteria. In FIGS. 1A and 1B, it can be seen
that a collapsed center 108 is included within the tubular mass
110. It is also evident from the cross-sectional of FIG. 1B that
the lateral edges 111 and 113 existing after the tubular ePTFE
extrusion has been heat treated are substantially rounded, and
thus, present a smooth surface to surrounding tissues when passed
through the body, thereby preventing tissue abrasion.
[0057] A process for making the first embodiment of FIGS. 1A-B is
also disclosed. This process involves preparing the article by
extrusion and longitudinal expansion of the tubular article. First,
a resin paste is mixed with an extrusion-aid such as mineral
spirits, and then compressed at relatively low pressures into an
extrusion billet.
[0058] Next, the pellet is mechanically extruded using a ram
extruder. The extruder initially compacts the resin and
extrusion-aid paste and feeds it into a die nozzle. The material is
then subjected to very high pressure and shear forces within the
die such that the resin exits as a tubular shaped article.
[0059] After being extruded, the article is dried. More
specifically, the lubricant is removed by subjecting the article to
temperatures slightly above the boiling point of the lubricant
(e.g., about 150.degree. C.), and far below the sintering or
coalescing temperature of the polymer (generally at about
327.degree. C.) in embodiments.
[0060] Following extrusion and drying, the tubular PTFE is heated
above the thermal transition point of about 354.degree. C. and
expanded longitudinally. This expansion process creates openings
containing fibrils interconnecting solid nodes of PTFE.
[0061] In embodiments, the article is extruded (and expanded) to a
tubular wall thickness of about 0.20 millimeters.
[0062] The now tubular expanded PTFE article is allowed to cool
over a period of time at a lower temperature, e.g., at ambient. The
article can also be cut into desired lengths which will ultimately
comprise individual prosthetic devices, e.g., surgical slings.
[0063] Once the article has cooled and is ready for use it, in
embodiments, will have expanded fibrils in the elongated
dimension.
[0064] After expansion the article, in embodiments, is subjected to
post-expansion processing where the article is subjected to both
moderate temperatures and pressures (below the thermal transition
point for PTFE) to flatten and soften the article. This can be done
by sandwiching the length of the article between a single hot
surface and an opposing surface, between two opposing plates, or on
one or more rollers in a system. The temperature at which the
article is reheated is, in embodiments, below the thermal
transition point (about 254.degree. C.). Conventionally, it has
been assumed that nothing can happen micro-structurally below that
transition temperature, but here significant changes in the
structure have been discovered (e.g., at temperatures around
200.degree. C.). The pressure applied to the article during this
step is low, e.g., a few psi.
[0065] Upon completion of this post-expansion processing, the
article will be softer. Additionally, the fibril structures will,
microscopically, appear to be more integrated and pore sizes will
be reduced and in some cases pores eliminated. The result is a
material that is softer and at the same time less porous.
[0066] As an optional additional step, an antimicrobial coating can
be added after the completion of earlier process steps discussed
above or below, in order to inhibit bacteria.
[0067] Once the article has been processed as discussed above, the
article can be presented for use along with existing implant
systems and/or methods. The article can also be prepared for use as
a sling according to any number of configuration steps. For
example, in embodiments, the ends of the article can be configured
for connection at each of ends 102 and 104 shown in FIG. 1A. In
FIG. 1C, it can be seen that a first coupler 114 and a second
coupler 116 have been added. The couplers 114 and 116 are crimped
on by applying a tool to crimp bodies 118 and 120. Once crimped on,
coupler 114 outwardly presents a first eyelet 122 and second
coupler 116 outwardly presents a second eyelet 124. Those skilled
in the art know that eyelets 122 and 124 could be received onto the
ends of placement aids for use in an implant procedure.
[0068] FIG. 1D depicts the article 100 shown in FIGS. 1A-B attached
at each end to a pair of placement aids (e.g., needles) 126 and 128
at each of the first and second ends 102 and 104 at connection
interfaces 130 and 132. Those skilled in the art will recognize
that numerous different sorts of ways that the placement aids 126
and 128 can be connected to ends 102 and 104 exist in the art. For
example, the ends can be: (i) secured into clamps existing on each
placement aids (ii) apertured for receipt of snaps on each
placement aid (see, e.g., upcoming FIG. 1E); (iii) knotted and then
secured into a V-shaped grooves on each aid; (iv) attached using
sutures; (v) attached using trocars; (vi) configured with anchors
configured for receipt by a snare with anchor-release functions; or
(vii) other means.
[0069] FIG. 1E shows an additional configuration process utilizing
the article created according to the processes above. In this
embodiment, the ends 102 and 104 of the device 100 have been
densified by the application of elevated heat and pressure. If the
ends of the device are subjected to temperatures slightly above
melt temperature and under pressure for an ample amount of time,
the ends 102 and 104 will be hardened, thus, creating transition
areas 134 and 136 between the sling body and the now densified ends
102 and 104. The relatively dense PTFE material at each end is more
rigid and has greater strength than the rest of the body of the
sling, thus configuring it for coupling. As an additional step in
embodiments, apertures 138 and 140 can be formed through the ends
102 and 104 for the receipt of placement aids.
[0070] Again here, as an optional step, antimicrobial coating could
be added after the article is configured for use as an implant
instead of beforehand. This timing might be advantageous since the
coating of the article will occur when the implant is in final (or
nearly final) form.
Example
[0071] A 100% PTFE powder was mixed with mineral spirits, and then
compressed under relatively low pressure to form a billet. The
billet was then mechanically extruded under high pressure using a
ram extruder having a die nozzle such that the resin was expanded
and solidified into a tubular shaped article having a thickness of
about 0.20 millimeters.
[0072] After being extruded, the article was dried by subjecting
the article to temperatures at about 175.degree. C., which is
slightly above the boiling point of the lubricant (about
150.degree. C.), and far below the sintering or coalescing
temperature of the polymer (about 327.degree. C.).
[0073] After drying, the tubular article was expanded
longitudinally at elevated temperatures and sintered to lock in the
expanded structure.
[0074] The tubular expanded PTFE article created was then allowed
to cool over a period of time at a lower temperature, e.g., at
ambient.
[0075] Once the article was cooled, it possessed expanded fibrils
in the elongated dimension, and resulted in the microscopic
appearance shown in the micrograph of FIG. 2. Referring to the
figure, it can be seen that the fibrils all extend in parallel
along the single axis of expansion. Also revealed in the FIG. 2
micrograph are columns of fibrils that are mostly 2 microns or less
in width and much smaller in height, but exist, nonetheless. This
structure is typical of a uniaxial expansion, albeit at a very,
very low expansion ratio (hence the short fibrils and large
expanses of solid PTFE between fibril columns).
[0076] After expansion, the now expanded article as shown in the
FIG. 2 micrograph was subjected to the post-expansion processing
discussed above where the article was exposed to moderately
elevated temperatures (e.g., about 200.degree. C.) and relatively
low applied pressures to flatten and soften the article. The
temperature was maintained below the melt point for PTFE.
[0077] Upon completion of this post-expansion processing, the
article was appreciably softer. Additionally, the fibril structures
were more integrated with the nodes/body of the article as can be
seen in the post-processing micrograph of FIG. 3. The application
of moderate temperatures and pressures resulted in greatly reduced
pore sizes (and sometimes pore elimination). Comparing the after
post-processing micrograph of FIG. 3 against the before post
processing In the after micrograph, it can be seen that the small
but regular longitudinal openings have almost entirely disappeared,
and are replaced with a sort of ridge shaped area. The few openings
that remain are much smaller than those shown in FIG. 2. Again, the
opening configurations determine whether any cells or bacteria can
penetrate the article after implant. This result is starkly
different than a typical ePTFE structure, more closely resembling a
conventional full density PTFE product. However, conventional full
density PTFE products are stiff and solid and would not work as a
prosthetic support, e.g., as a sling. The surprisingly tight
microstructure and soft drape make the product shown in FIG. 3
ideal for such a use.
[0078] The softness, strength, and porosity created in the article
proved to be ideal for use as a surgical sling device, and are also
quite surprising in view of conventional wisdom that when ePTFE
structure is closed down, stiffness goes up.
[0079] The article was then cut into desired sections which will
ultimately comprise individual slings, and otherwise configured for
use as sling implants.
[0080] FIG. 4A shows a perspective view of a second embodiment 400
that includes a first end 402, a second end 404, and a collapsed
tube and filled body 406. FIG. 4B shows a cross sectional view
taken at 4B-4B in FIG. 4A. The collapsed-filled tube embodiment 400
includes a first end 402, a second end 404, and an elongated body
406. The elongated body 406 of the second embodiment comprises
expanded PTFE with a node/fibril structures like the one processed
in the first embodiment (article 100). Different, however, is that
the center of the tubular mass 410, after the article has been
expanded and cooled, is filled with a meltable filler material 408.
In embodiments, the filler material 408 is a fluoropolymer
Fluorinated Ethylene Propylene (FEP) in embodiments, but could be
some other equivalent material). In order to function properly, the
filler should be comprised of a material having a melt point below
that of PTFE. Thus, the filler could be comprised of any of
numerous kinds of meltable materials capable of adequately
bonding.
[0081] Once the filler has been put into the processed ePTFE tube,
heat and pressure are applied to flatten the article much like is
done in the process described for the first article 100 except that
the temperature selected should be greater than the melt point of
the filler, but still lower than the melt point for PTFE. The
application of the moderate temperatures and pressures flatten and
soften the article, and allow the filler to serve as a bond
enhancer, facilitating adhesion within the now collapsed tube.
[0082] Articles made according to the example above have been
configured for use as surgically implantable slings as discussed
above (before the example section). For example, the ends have been
modified to add hardware like discussed for FIG. 1C; (ii) densified
and apertured as discussed regarding FIG. 1E, and otherwise
configured to operate with placement aids.
[0083] Additionally, an antimicrobial coating step has been
contemplated to be beneficial for many applications. The coating
could be added any time after the completion of post-processing
heat treatment, but most likely be executed after the article has
been configured for use as an implant, the purpose being to inhibit
bacteria.
[0084] Although the descriptions above relate to the ePTFE strips
of articles 100 and 200 being implemented as prosthetic slings used
to stabilize a patient's urethra or bladder, they could also be
useful in providing support for other pelvic organs. Additionally,
multiple strips could be used together for certain applications.
Further, the articles could be used for the support of rectal
muscles in other applications.
[0085] Many different arrangements of the various components
depicted, as well as components not shown, are possible without
departing from the spirit and scope of what is claimed herein.
Embodiments have been described with the intent to be illustrative
rather than restrictive. Alternative embodiments will become
apparent to those skilled in the art that do not depart from what
is disclosed. A skilled artisan may develop alternative means of
implementing the aforementioned improvements without departing from
what is claimed.
[0086] It will be understood that certain features and
subcombinations are of utility and may be employed without
reference to other features and subcombinations and are
contemplated within the scope of the claims. Not all steps listed
in the various figures need be carried out in the specific order
described.
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