U.S. patent application number 11/093983 was filed with the patent office on 2005-10-06 for medical device.
Invention is credited to Gingras, Peter, King, Dean.
Application Number | 20050222591 11/093983 |
Document ID | / |
Family ID | 34962450 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050222591 |
Kind Code |
A1 |
Gingras, Peter ; et
al. |
October 6, 2005 |
Medical device
Abstract
A soft tissue implant comprises a condensed surgical mesh having
a plurality of monofilament biocompatible fibres 12. Condensing of
the fibres reduces the void space between adjacent fibres 12 in the
mesh and reduces the surface area of the fibres 12 available for
contact with tissue 18. Condensation of the fibres 12 may be
achieved by applying mechanical pressure, and/or vacuum, and/or
heat to the mesh.
Inventors: |
Gingras, Peter; (Taylors
Hill, IE) ; King, Dean; (Shantalla, IE) |
Correspondence
Address: |
FISH & RICHARDSON PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Family ID: |
34962450 |
Appl. No.: |
11/093983 |
Filed: |
March 30, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60558067 |
Mar 30, 2004 |
|
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|
60642607 |
Jan 10, 2005 |
|
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Current U.S.
Class: |
606/151 ;
623/23.74 |
Current CPC
Class: |
Y10T 442/40 20150401;
A61L 27/56 20130101; A61F 2/0045 20130101; A61F 2/0063 20130101;
A61F 2002/0068 20130101; Y10T 442/30 20150401; D04B 21/12 20130101;
A61L 27/50 20130101; D10B 2509/08 20130101 |
Class at
Publication: |
606/151 ;
623/023.74 |
International
Class: |
A61F 002/02 |
Claims
1. A soft tissue implant comprising a condensed surgical mesh, the
mesh comprising one or more biocompatible fibres, at least one of
the fibres comprising a monofilament fibre.
2. An implant as claimed in claim 1 wherein each fibre in the mesh
comprises a monofilament fibre.
3. An implant as claimed in claim 1 wherein along at least part of
at least one fibre, the fibre is condensed.
4. An implant as claimed in claim 3 wherein the mesh has a void
space between adjacent fibres in the mesh, and along the condensed
part of the fibre, the mesh void space is reduced.
5. An implant as claimed in claim 3 wherein along the condensed
part of the fibre: 6 A v A F 1.5where: A.sub.V=area of the void
between adjacent fibres in the mesh available for tissue
infiltration. A.sub.F=cross-sectional area of the fibre.
6. An implant as claimed in claim 3 wherein along the condensed
part of the fibre, the surface area of the fibre available for
contact with tissue is reduced.
7. An implant as claimed in claim 6 wherein along the condensed
part of the fibre: 7 P FC P F 0.8where: P.sub.FC=Perimeter of the
fibre, at a cross-section of the fibre, which is available for
contact with tissue. P.sub.F=Total perimeter of the fibre, at a
cross-section of the fibre.
8. An implant as claimed in claim 1 wherein the fibres are
condensed at at least some points of intersection between the
fibres.
9. An implant as claimed in claim 1 wherein the fibres are at least
partially flattened at at least some points of intersection between
the fibres.
10. An implant as claimed in claim 1 wherein the mesh has at least
one overlap region, at which at least one fibre overlaps at least
one other fibre, at least one of the fibres being condensed at the
overlap region.
11. An implant as claimed in claim 10 wherein at the overlap
region, one fibre is fused with an overlapping fibre.
12. An implant as claimed in claim 10 wherein at the overlap
region, one fibre engages with an overlapping fibre.
13. An implant as claimed in claim 12 wherein the engagement of one
fibre with an overlapping fibre substantially prevents in-growth of
tissue between the overlapping fibres.
14. An implant as claimed in claim 10 wherein the overlapping
fibres are condensed together.
15. An implant as claimed in claim 1 wherein the fibre comprises a
polymer and/or a copolymer.
16. An implant as claimed in claim 1 wherein the fibre comprises
polypropylene.
17. An implant as claimed in claim 1 wherein the mesh is condensed
substantially uniformly.
18. An implant as claimed in claim 1 wherein the mesh comprises a
condensed region and an uncondensed region.
19. An implant as claimed in claim 1 wherein the mesh comprises at
least two regions which are differentially condensed.
20. An implant as claimed in claim 1 wherein the implant is
configured for attachment to tissue.
21. An implant as claimed in claim 20 wherein the implant is
configured to facilitate coupling of an attachment element to the
mesh.
22. An implant as claimed in claim 21 wherein the attachment point
comprises an attachment opening in the mesh to receive an
attachment element, such as a suture, and/or a staple, and/or an
adhesive.
23. An implant as claimed in claim 20 wherein the mesh comprises
one or more engagement formations for attachment of the mesh to
tissue.
24. An implant as claimed in claim 23 wherein the mesh comprises a
plurality of protrusions configured in a wave-like or dimple like
pattern.
25. An implant as claimed in claim 1 wherein at least part of the
mesh is treated to increase the coefficient of friction of the
mesh.
26. An implant as claimed in claim 1 wherein the mesh is configured
to maintain the position of the mesh relative to tissue.
27. An implant as claimed in claim 26 wherein the mesh comprises
one or more engagement formations for engaging tissue.
28. An implant as claimed in claim 1 wherein at least a portion of
the mesh is of a composite configuration.
29. An implant as claimed in claim 18 wherein the implant comprises
an inelastic element to reinforce the mesh.
30. An implant as claimed in claim 29 wherein the inelastic element
is woven into the mesh.
31. An implant as claimed in claim 29 wherein the inelastic element
is attached to a surface of the mesh.
32. An implant as claimed in claim 1 wherein the thickness of at
least part of the mesh is in the range of from 0.001 inches to 0.04
inches.
33. An implant as claimed in claim 1 wherein the thickness of the
mesh is substantially constant across the mesh.
34. An implant as claimed in claim 1 wherein the thickness of the
mesh varies across the mesh.
35. An implant as claimed in claim 1 wherein the density of at
least part of the mesh is greater than 0.081 g/cm.sup.3.
36. An implant as claimed in claims 1 wherein the density of the
mesh is substantially constant across the mesh.
37. An implant as claimed in claim 1 wherein the density of the
mesh varies across the mesh.
38. An implant as claimed in claim 1 wherein the mesh pore size is
uniform across the mesh.
39. An implant as claimed in claim 1 wherein the mesh pore size
varies across the mesh.
40. An implant as claimed in claim 1 wherein the implant comprises
a three dimensional structure.
41. An implant as claimed in claim 1 wherein at least some of the
mechanical properties of the mesh are substantially
omnidirectional.
42. A method of forming a surgical mesh, comprising one or more
biocompatible fibres, at least one of the fibres comprising a
monofilament fibre, the method comprising the step of condensing at
least part of the mesh.
43. A method as claimed in claim 42 wherein each fibre in the mesh
comprises a monofilament fibre.
44. A method as claimed in claim 42 wherein the mesh is condensed
by applying heat to at least part of the mesh.
45. A method as claimed in claim 42 wherein the mesh is condensed
by applying pressure to at least part of the mesh.
46. A method as claimed in claims 42 wherein the mesh is condensed
by applying a vacuum to at least part of the mesh.
47. A method as claimed in claim 42 wherein the method comprises
the step of heat-setting the mesh.
48. A method as claimed in claim 42 wherein the method comprises
the step of controlling the texture of the mesh.
49. A method as claimed in claim 48 wherein the texture is
controlled by arranging the mesh in contact with a control surface
before the step of condensing is performed.
50. A method as claimed in claim 49 wherein the method comprises
the step of maintaining the temperature of the control surface
substantially stable.
51. A method as claimed in claim 49 wherein the method comprises
the step of maintaining the pressure of the control surface
substantially stable.
52. A method as claimed in claim 42 wherein the method comprises
the step of forming the mesh into a three-dimensional
structure.
53. A method as claimed in claim 42 wherein the method comprises
the step of treating the mesh to make at least some of the
mechanical properties of the mesh substantially
omnidirectional.
54. A method of making a soft tissue implant, the method
comprising: (c) providing a surgical mesh; and (d) condensing the
surgical mesh to generate-material useful as a soft tissue
implant
55. The method of claim 54, further comprising altering the size or
shape of the material to generate the soft tissue implant.
56. The method of claim 54, wherein providing the surgical mesh
comprises extruding a biocompatible polymer or copolymer into a
fibre and forming the surgical mesh from the fibre.
57. The method of claim 56 wherein the biocompatible polymer or
copolymer is a non-absorbable polymer or copolymer.
58. The method of claim 57 wherein the non-absorbable polymer is a
polymer of polypropylene, polyethylene, polyethylene terephthalate,
polytetrafluoroethylene, polyaryletherketone, nylon, fluorinated
ethylene propylene, polybutester, or silicone, or a copolymer
thereof.
59. The method of claim 58, wherein the biocompatible polymer or
copolymer is an absorbable polymer.
60. The method of claim 59, wherein the absorbable polymer is a
polymer of polyglycolic acid (PGA), polylactic acid (PLA),
polycaprolactone, polydioxanone or polyhydroxyalkanoate, or a
copolymer thereof.
61. The method of claim 60, wherein the biocompatible polymer is
collagen or a copolymer comprising collagen.
62. The method of claim 57, wherein forming the surgical mesh
comprises knitting the fibre.
63. The method of claim 54 wherein the mesh comprises pores of a
substantially uniform size.
64. The method of claim 54 wherein the mesh comprises pores that
are greater than 50 micrometers in diameter.
65. The method of claim 54 wherein condensing the surgical mesh
comprises applying pressure and, optionally, heat to the mesh.
66. The method of claim 65 wherein the pressure or heat is applied
for a time and under conditions sufficient to reduce the void space
within the mesh.
67. The method of claim 65 wherein the pressure or heat is applied
for a time and under conditions sufficient to reduce the surface
area available for contact with a patient's tissue.
68. The method of claim 66, wherein the pressure or heat is applied
to the mesh uniformly.
69. The method of claim 66 wherein the pressure or heat is applied
to the mesh non-uniformly.
70. The method of claim 65 wherein the pressure or heat is applied
to the mesh while the mesh is under vacuum.
71. The method of claim 54 further comprising inserting, into the
material, an opening for receiving an attachment element.
72. The method of claim 54 wherein the material is about
0.001-0.040 inches thick.
73. The method of claim 54 wherein the material is of a size and
shape appropriate for stabilizing or supporting the bladder neck,
urethra, pelvic floor, or abdominal wall.
74. The method of claim 54 further comprising fashioning the
material into a tubular or conical shape.
75. A soft tissue implant made by the method of claim 54.
76. A method of making a soft tissue implant, the method
comprising: (d) providing a surgical mesh; (e) condensing the
surgical mesh by applying pressure and, optionally, heat to the
mesh, wherein the pressure and, optionally, the heat, is applied
for a time and under conditions sufficient to reduce the void space
within the mesh; and (f) cleaning or sterilizing the mesh, thereby
generating material useful as a soft tissue implant.
77. A soft tissue implant comprising a woven or knit monofilament
mesh having a density greater than 0.081 g/cm.sup.3, the space
between the monofilament mesh constituting pores of about 500 .mu.m
to about 10 mm in diameter.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to medical devices and more
specifically to soft tissue implants that can be used to repair
injured or otherwise defective tissue within the body (e.g., pelvic
floor prolapse and hernias).
BACKGROUND
[0002] Stress urinary incontinence (SUI), pelvic floor prolapse,
and hernias are serious health concerns worldwide. Millions of
people suffer from these problems, and surgical procedures
involving the placement of implants to stabilize or support the
affected tissue are required.
[0003] Devices for treating tissue defects can be constructed from
synthetic materials such as polypropylene, polytetrafluoroethylene,
polyester, and silicone. Devices constructed from non-synthetic
materials can include allografts, homografts, heterografts,
xenografts, autologous tissues, cadaveric fascia, and fascia lata.
The supply of non-synthetic devices can vary greatly and certain
sizes of non-synthetic materials can be difficult to obtain. For
example, autologous material may be difficult or impossible to
harvest from some patients due to the health of the patient or the
size of the tissue needed for a repair.
[0004] Biomaterials, which work either by mechanical closure or by
inducing strong scar tissue, can also be used. However, the
synthetic material can increase the rate of local wound
complications such as seromas (by about 30-50%), paraesthesia (by
about 10-20%), and restriction of mobility (by about 25%) (see
Klinge et al., Eur. J. Surg. 164:951-960, 1998). More specifically,
biomaterial implants are used to support the abdominal wall, which
has an average displacement elasticity of 25% at a maximum tensile
strength of 16 N/cm (see Junge et al., Hernia 5:113-118, 2001).
Biomaterials with initially low bending stiffness may turn into
hard sheets in the post implant period and fail to exhibit 25%
strain under forces of 16 N/cm. With excessive scar tissue
formation, there is a decrease in abdominal wall mobility.
Histological analysis of explanted biomaterials has revealed
persistent inflammation at the interface, even after several years
of implantation, which is influenced by the weight of the
biomaterial and the surface area in contact with the recipient
tissue. The persistent foreign body reaction is independent of the
inflammation time, but considerably affected by the type of
biomaterial (see Welty et al., Hernia 5:142-147, 2001; and Klinge
et al., Eur. J. Surg. 165:665-673, 1999). Consequently, the
persistence of a foreign body reaction at the biomaterial-tissue
interface might cause severe problems, particularly in young
patients, in whom the biomaterial is expected to hold for prolonged
periods of time.
[0005] Bard Mesh.TM. is a non-absorbable implant that is made from
monofilament polypropylene fibres using a knitting process (C. R.
Bard, Inc., Cranston, R. I.; see also U.S. Pat. No. 3,054,406; U.S.
Pat. No. 3,124,136; and Chu et al., J. Bio. Mat. Res. 19:903-916,
1985). The thickness for Bard Mesh.TM. and other commercially
available implants is provided in the table below. As indicated,
the thinnest of these materials has a thickness of 0.016
inches.
1 Thickness Material Company Code No. (inches) Bard Mesh C. R.
Bard/Davol 112660 0.026 Prolene Mesh J&J/Ethicon PML 0.020
Prolene Soft Mesh J&J/Ethicon SPMXXL 0.016 Gore-Tex Soft W. L.
Gore 1315020020 0.079 Tissue Patch ProLite Atrium Medical
1001212-00 0.019 ProLite Ultra Atrium Medical 30721 0.016
[0006] Additional non-absorbable meshes are known (see U.S. Pat.
Nos. 2,671,444; 4,347,847; 4,452,245; 5,292,328; 5,569,273;
6,042,593; 6,090,116; 6,287,316 (this patent describes the mesh
marketed as Prolene.TM.; and U.S. Pat. No. 6,408,656). These
products are all made using synthetic fibre technology. Different
knit patterns impart unique mechanical properties to each
configuration.
[0007] A variety of absorbable or partially absorbable materials
have been described (see U.S. Pat. Nos. 4,633,873; 4,693,720;
4,838,884; and 6,319,264). There are also a variety of implants
used to treat urinary incontinence in women (see U.S. Pat. Nos.
4,857,041; 5,840,011; 6,042,534; 6,110,101; 6,306,079; and
6,355,065; see also U.S. Pat. Nos. 5,112,344; 5,611,515; 5,637,074;
5,842,478; 5,860,425; 5,899,909; 6,039,686; 6,273,852; 6,406,423;
6,478,727; 6,702,827; WO 2004/017862; WO 02/39890; and WO
02/26108).
[0008] At present, monofilament polypropylene surgical meshes are
the most widely used soft tissue implants. Although serious
complications associated with implants are infrequent, they are
well documented. Moreover, each of the implants presently in use
are believed to have one or more deficiencies. For example, their
construction can result in characteristics (e.g., wall thickness
and surface area) that increase the risk of an inflammatory
response or of infection; seromas can form postoperatively within
the space between the prosthesis and the host tissues; due to
material content, width, and wall thickness, surgeons must make
large incisions for implantation (the present implants can be
difficult to deploy in less invasive surgical methods); rough and
irregular implant surfaces can irritate tissues and lead to the
erosion of adjacent tissue structures; adhesions to the bowel can
form when the implant comes in direct contact with the intestinal
tract; where pore size is reduced, there can be inadequate tissue
ingrowth and incorporation; and the pore size and configuration of
the implants does not permit adequate visualization through the
implant during laparoscopic procedures. Additional complications
include pain, discomfort, obstruction, and organ perforations.
SUMMARY
[0009] The present invention features medical devices that include
biocompatible material for stabilising or supporting a tissue of a
patient's body. Methods for making the devices are also within the
scope of the invention. More specifically, the devices include
condensed surgical meshes with reduced void and surface contact
areas (e.g., a condensed monofilament surgical mesh) produced from
a biocompatible polymer without added materials (e.g. coatings).
The studies conducted with the condensed mesh indicate that, by
reducing the void space therein (e.g., the space between fibres
within the mesh), the mesh is less likely to cause inflammation.
With a reduced surface area, there are fewer places for
inflammatory cells to aggregate. Void area reduction may create a
superior device in other ways as well.
[0010] The term "implant" may be used instead of "device." Soft
tissue implants are those suitable for application to any soft
tissue within a patient's body, and they may also be referred to as
surgical implants. While the patient may be a human, the invention
is not so limited; the implants can be used to repair or stabilize
soft tissue in any animal.
[0011] The methods of the invention include methods of making a
soft tissue implant by providing a surgical mesh and condensing the
surgical mesh to generate material useful as a soft tissue implant.
If desired, one can further alter the size or shape of the material
(e.g., one can trim the implant or fold or roll it into a conical
or tubular shape). As with other medical devices, the implants may
be sterilized before use.
[0012] The surgical mesh can be obtained from a commercial supplier
or made using methods known in the art. For example, a mesh can be
made by extruding a biocompatible polymer or copolymer into a fibre
and knitting or weaving the fibres together. To facilitate
production, the process can be mechanized. For example, the knitted
mesh of the invention can be made on any two-bar warp loom.
[0013] Useful polymers and copolymers are described as
biocompatible as they are non-toxic or sufficiently harmless to
allow their use in human patients. The polymers and copolymers can
be non-absorbable (e.g., they may made with polypropylene,
polyethylene, polyethylene terephthalate, polytetrafluoroethylene,
polyaryletherketone, nylon, fluorinated ethylene propylene,
polybutester, or silicone) or absorbable (polyglycolic acid (PGA),
polylactic acid (PLA), polycaprolactone, polydioxanone or
polyhydroxyalkanoate, or a copolymer thereof. Absorbable implants
degrade following implantation, and the rate of degradation can
vary greatly depending upon the amount and type of material used.
In other embodiments, the polymer or copolymer can include a
naturally occurring biological molecule, or a variant thereof, such
as collagen. The fibres can be intertwined in many different ways
by knitting or weaving. The spaces within the mesh may be referred
to as cells or pores, and a given mesh can include uniformly or
non-uniformly patterned cells having any number of shapes (e.g.,
the cells or pores can be substantially round, square, oval-shaped
or diamond-shaped). The size of the pores can also vary and may be
uniform or non-uniform. For example, the mesh can include pores
that are about 50 .mu.m in diameter.
[0014] The mesh can be condensed in any way that reduces the void
space between the fibres. For example, one can apply mechanical
pressure, vacuum, and/or heat to the mesh. The fibres are thermally
set to a desired shape that reduces the void space between and
around the fibres of the surgical mesh. The condensation force is
applied for a time and under conditions sufficient to reduce the
void space within the mesh or the area of the implant available to
contact a patient's tissue. We may refer to that area as the
surface contact area.
[0015] The fibres most useful for creating the implant are
monofilament fibres. Monofilament fibres are less prone to
infection and inflammation. Consequently, a surgical mesh
constructed from monofilament fibres is a preferred structure
compared to multifilament based surgical meshes. Monofilament
fibres have a consistent cross sectional area compared to
multifilament fibres that have small individual fibres bundled
together. Multifilament fibres have an increased surface contact
area compared to monofilament fibres of the same diameter. In
addition, monofilament fibres are more stable when subjected to
condensation treatment and are less likely to move in relation to
adjacent fibres which preserves the condensed structure.
[0016] The compressive force can be applied to the mesh uniformly,
in which case the void space will be reduced in a substantially
uniform way within the entire mesh. Alternatively, the force (e.g.,
pressure) can be applied to the mesh non-uniformly. In that event,
the extent to which the void space is reduced will vary from one
region of the mesh to another (the reduction being greater where
the force is greater). To facilitate condensation, the force can be
applied to the mesh while the mesh is under vacuum.
[0017] Either before or after condensation, the mesh can be
altered. For example, the mesh can be cut or otherwise fashioned
into a different shape before condensation. The shape change can
include inserting, into the mesh or material condensed therefrom,
an opening for receiving an attachment element (e.g., a suture,
staple, or other fixation device). The force may be applied to the
mesh in such a way that a region for receiving an attachment
element (e.g., a point along the edge, or a folded edge, of the
mesh or material) varies in density from a region that is not
intended to receive an attachment element.
[0018] Depending upon the strength of the condensation, the
thickness (or average thickness) of the material can vary. For
example, the material can be about 0.001-0.040 inches thick. The
overall dimensions of the mesh or material can be unique or can be
those of any presently available surgical mesh or implant. For
example, the condensed materials described herein can be fashioned
to support tissue (e.g., a part of the bladder, urethra, pelvic
floor, or abdominal wall) and may have the overall shape of any
device presently used to do so.
[0019] The invention also features devices (e.g., soft tissue
implants) made by any of the methods described herein. These
devices are described further below and illustrated in the
drawings.
[0020] In specific embodiments, the methods of the invention
include providing a surgical mesh; placing the surgical mesh under
vacuum; heating the surgical mesh; compressing the surgical mesh by
applying pressure to the mesh (for a time and under conditions
sufficient to reduce the void space within the mesh or the surface
contact area); and cleaning and/or sterilizing the mesh, thereby
generating material useful as a soft tissue implant. The heating
process can impact longitudinal elasticity; applying heat while
applying tension to the implant can reduce elasticity).
[0021] In specific embodiments, the invention features a soft
tissue implant comprising a woven or knit monofilament mesh having
a density greater than 0.081 g/cm.sup.3, the space between the
monofilament mesh constituting pores of about 500 .mu.m to about 10
mm in diameter.
[0022] The implants of the present invention offer a combination of
high porosity, high strength, and low material content, and they
may have one or more of the following advantages. They can include
pores or porous structures that stimulate fibrosis and reduce
inflammation; they can reduce the risk of erosion and formation of
adhesions with adjacent tissue (this is especially true with
implants having a smooth surface and reduced surface contact area)
and atraumatic (e.g., smooth, tapered, or rounded edges); they can
simulate the physical properties (e.g. elasticity) of the tissue
being repaired or replaced, which is expected to promote more
complete healing and minimise patient discomfort; their surface
areas can be reduced relative to prior art devices (having a
reduced amount of material in contact with tissue may decrease the
likelihood of an immune or inflammatory response). Practically, the
techniques that can be used to produce the implants of the present
invention are efficient and reproducible. The implants described
herein should provide enhanced biocompatibility in a low profile
configuration while maintaining the requisite strength for the
intended purpose. The implants may also have improved wrinkle
recovery memory.
[0023] According to the invention there is provided a soft tissue
implant comprising a condensed surgical mesh, the mesh comprising
one or more biocompatible fibres, at least one of the fibres
comprising a monofilament fibre.
[0024] In one embodiment of the invention each fibre in the mesh
comprises a monofilament fibre. The mesh may be knit from one or
more fibres. The mesh may be woven from one or more fibres.
[0025] In one embodiment along at least part of at least one fibre,
the fibre is condensed. The mesh may have a void space between
adjacent fibres in the mesh, and along the condensed part of the
fibre, the mesh void space is reduced. The distance between
adjacent fibres in the mesh may be in the range of from
approximately 5 .mu.m to approximately 500 .mu.m. Along the
condensed part of the fibre: 1 A v A F may be 1.5
[0026] where:
[0027] A.sub.v=area of the void between adjacent fibres in the mesh
available for tissue infiltration.
[0028] A.sub.F=cross-sectional area of the fibre.
[0029] In one case 2 A v A F 1.0 3 A v A F
maybeapproximatelyequalto0.6.
[0030] Along the condensed part of the fibre, the surface area of
the fibre available for contact with tissue may be reduced. Along
the condensed part of the fibre: 4 P FC P F maybe 0.8
[0031] where:
[0032] P.sub.FC=Perimeter of the fibre, at a cross-section of the
fibre, which is available for contact with tissue.
[0033] P.sub.F=Total perimeter of the fibre, at a cross-section of
the fibre.
[0034] In one case 5 P FC P F 0.65 P FC P F
maybeapproximatelyequalto0.5
[0035] In another embodiment the fibres are condensed at at least
some points of intersection between the fibres. The fibres may be
at least partially flattened at at least some points of
intersection between the fibres. At least some of the points of
intersection may be stitch loop intersections.
[0036] In one case the mesh has at least one overlap region, at
which at least one fibre overlaps at least one other fibre, at
least one of the fibres being condensed at the overlap region. At
the overlap region, the surface of the mesh available for contact
with tissue may be less than the sum of the total surface areas of
the overlapping fibres. The ratio of the tissue contact area of the
mesh to the sum of the total surface areas of the overlapping
fibres may be less than or equal to 0.8. At the overlap region, one
fibre may be fused with an overlapping fibre. At the overlap
region, one fibre may engage with an overlapping fibre. The
engagement of one fibre with an overlapping fibre may substantially
prevent in-growth of tissue between the overlapping fibres. The
overlapping fibres may be condensed together.
[0037] In another embodiment the fibre comprises a polymer and/or a
copolymer. The polymer and/or copolymer may be absorbable. The
polymer and/or copolymer may be non-absorbable.
[0038] The fibre may comprise polypropylene.
[0039] In another case the mesh is condensed substantially
uniformly. The mesh may comprise a condensed region and an
uncondensed region. The mesh may comprise at least two regions
which are differentially condensed.
[0040] In one embodiment the implant is configured for attachment
to tissue. The mesh may comprise one or more attachment points. The
mesh may be reinforced in the region of the attachment point. The
implant may be configured to facilitate coupling of an attachment
element to the mesh. In one case the attachment point comprises an
attachment opening in the mesh to receive an attachment element,
such as a suture, and/or a staple, and/or an adhesive. The mesh may
comprise one or more engagement formations for attachment of the
mesh to tissue. The engagement formation may comprise a protrusion.
The mesh may comprise a plurality of protrusions configured in a
wave-like or dimple like pattern.
[0041] In one embodiment at least part of the mesh is treated to
increase the coefficient of friction of the mesh. At least part of
the mesh may have an increased surface roughness.
[0042] In another embodiment the mesh is configured to maintain the
position of the mesh relative to tissue. The mesh may comprise one
or more engagement formations for engaging tissue.
[0043] At least a portion of the mesh may be of a composite
configuration. The implant may comprise an inelastic element to
reinforce the mesh. The inelastic element may comprise one or more
fibres. The inelastic element may be woven into the mesh. The
inelastic element may be attached to a surface of the mesh.
[0044] In another case the thickness of at least part of the mesh
is in the range of from 0.001 inches to 0.04 inches. The thickness
of the mesh may be substantially constant across the mesh. The
thickness of the mesh may vary across the mesh. The density of at
least part of the mesh may be greater than 0.081 g/cm.sup.3. The
density of the mesh may be substantially constant across the mesh.
The density of the mesh may vary across the mesh.
[0045] In another embodiment the mesh pore size is uniform across
the mesh. The mesh pore size may vary across the mesh.
[0046] The implant may comprise a three dimensional structure. The
three dimensional structure may comprise a conical shape. The three
dimensional structure may comprise a cylindrical shape.
[0047] In one embodiment at least some of the mechanical properties
of the mesh are substantially omnidirectional. The elasticity of
the mesh may be substantially omnidirectional.
[0048] In another aspect of the invention there is provided a
method of forming a surgical mesh, comprising one or more
biocompatible fibres, at least one of the fibres comprising a
monofilament fibre, the method comprising the step of condensing at
least part of the mesh.
[0049] In one embodiment the method comprises the steps of:--
[0050] providing the one or more biocompatible fibres; and
[0051] forming the surgical mesh from the one or more fibres.
[0052] Each fibre in the mesh may comprise a monofilament
fibre.
[0053] In one case the mesh is condensed by applying heat to at
least part of the mesh. The mesh may be condensed by applying
pressure to at least part of the mesh. The mesh may be condensed by
applying a vacuum to at least part of the mesh.
[0054] In one case the method comprises the step of heat-setting
the mesh. The step of heat-setting may be performed before the step
of condensing. The step of heat-setting may be performed after the
step of condensing. The step of heat-setting may be performed
during the step of condensing.
[0055] In another embodiment the method comprises the step of
controlling the texture of the mesh. The method may comprise the
step of controlling the texture of the external surface of the
mesh. The texture may be controlled by arranging the mesh in
contact with a control surface before the step of condensing is
performed. The method may comprise the step of maintaining the
temperature of the control surface substantially stable. The method
may comprise the step of maintaining the pressure of the control
surface substantially stable.
[0056] In one case the method comprises the step of forming the
mesh into a three-dimensional structure. The method may comprise
the step of treating the mesh to make at least some of the
mechanical properties of the mesh substantially omnidirectional.
The mesh may be stretched in a first direction while holding the
mesh in a second direction perpendicular to the first
direction.
[0057] In one case the mesh is formed by knitting the one or more
fibres, or weaving the one or more fibres.
[0058] In another aspect the invention provides a method of making
a soft tissue implant, the method comprising:
[0059] (a) providing a surgical mesh; and
[0060] (b) condensing the surgical mesh to generate material useful
as a soft tissue implant
[0061] The method may comprise altering the size or shape of the
material to generate the soft tissue implant. Providing the
surgical mesh may comprise extruding a biocompatible polymer or
copolymer into a fibre and forming the surgical mesh from the
fibre. In one case the biocompatible polymer or copolymer is a
non-absorbable polymer or copolymer. The non-absorbable polymer may
be a polymer of polypropylene, polyethylene, polyethylene
terephthalate, polytetrafluoroethylene, polyaryletherketone, nylon,
fluorinated ethylene propylene, polybutester, or silicone, or a
copolymer thereof. In another case the biocompatible polymer or
copolymer is an absorbable polymer. The absorbable polymer may be a
polymer of polyglycolic acid (PGA), polylactic acid (PLA),
polycaprolactone, polydioxanone or polyhydroxyalkanoate, or a
copolymer thereof. The biocompatible polymer may be collagen or a
copolymer comprising collagen.
[0062] In one embodiment forming the surgical mesh comprises
knitting the fibre. The mesh may comprise pores of a substantially
uniform size. The mesh may comprise pores that are greater than 50
micrometers in diameter.
[0063] In one case condensing the surgical mesh comprises applying
pressure and, optionally, heat to the mesh. The pressure or heat
may be applied for a time and under conditions sufficient to reduce
the void space within the mesh. The pressure or heat may be applied
for a time and under conditions sufficient to reduce the surface
area available for contact with a patient's tissue. The pressure or
heat may be applied to the mesh uniformly. The pressure or heat may
be applied to the mesh non-uniformly. The pressure or heat may be
applied to the mesh while the mesh is under vacuum.
[0064] In one case the method comprises inserting, into the
material, an opening for receiving an attachment element. The
material may be about 0.001-0.040 inches thick. The material may be
of a size and shape appropriate for stabilizing or supporting the
bladder neck, urethra, pelvic floor, or abdominal wall.
[0065] In one embodiment the method comprises fashioning the
material into a tubular or conical shape.
[0066] The invention also provides a soft tissue implant made by
the method of the invention.
[0067] In a further aspect the invention provides a method of
making a soft tissue implant, the method comprising:
[0068] (a) providing a surgical mesh;
[0069] (b) condensing the surgical mesh by applying pressure and,
optionally, heat to the mesh, wherein the pressure and, optionally,
the heat, is applied for a time and under conditions sufficient to
reduce the void space within the mesh; and
[0070] (c) cleaning or sterilizing the mesh, thereby generating
material useful as a soft tissue implant.
[0071] The invention provides in a further aspect a soft tissue
implant comprising a woven or knit monofilament mesh having a
density greater than 0.081 g/cm.sup.3, the space between the
monofilament mesh constituting pores of about 500 .mu.m to about 10
mm in diameter.
[0072] The details of one or more embodiments of the invention are
set forth in the accompanying drawings and the description below.
Other features, objects, and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0073] FIG. 1 is a flow chart illustrating some of the steps in a
method for producing an implant for treating tissue defects;
[0074] FIGS. 2A and 2B are cross sectional diagrams of an
uncondensed surgical mesh implant;
[0075] FIG. 2A depicts the round and oval perimeters of
monofilament fibres and the fibre cross sections;
[0076] FIG. 2B depicts the perimeters and illustrates the area of
the mesh available to contact tissue once implanted into a patient
also referred to as the area of void for tissue infiltration;
[0077] FIGS. 3A and 3B are cross sectional diagrams of the surgical
mesh implant of FIGS. 2A and 2B following condensation;
[0078] FIG. 3A depicts the altered perimeters and FIG. 3B
illustrates the reduced area of the mesh available for tissue
contact;
[0079] FIGS. 4A-4C are scanning electron micrographs of a surgical
mesh before (FIG. 4A) and after (FIG. 4B) condensation and with an
attached non-elastic element (FIG. 4C). The implant shown in FIG.
4C may be referred to as a composite implant sling;
[0080] FIGS. 5A and 5B are scanning electron micrographs of
Prolene.TM. Soft Mesh (no condensation) 35.times. and Mersilene.TM.
Mesh (no condensation) 35.times., respectively;
[0081] FIGS. 6A-6C are scanning electron micrographs of a
polypropylene mesh made as described in Example 3, with no
condensation, at 35.times., 80.times., and 70.times., respectively.
FIG. 6D is a light micrograph of a polypropylene mesh made as
described in Example 3, with no condensation, cross section shown
at 125.times..;
[0082] FIGS. 7A-7C are scanning electron micrographs of a
polypropylene mesh made as described in Example 4, with
condensation at a force of 10 N/cm.sup.2, heat application, and
vacuum, at 35.times., 80.times., and 70.times., respectively. FIG.
7D is a light micrograph of a polypropylene mesh made as described
in Example 4, with condensation at a force of 10 N/cm.sup.2, heat
application, and vacuum, cross section shown at 125.times..;
[0083] FIGS. 8A-8C are scanning electron micrographs of a
polypropylene mesh made as described in Example 5, with
condensation at a force of 25 N/cm.sup.2, heat application, and
vacuum, at 35.times., 80.times., and 70.times., respectively. FIG.
8D is a light micrograph of a polypropylene mesh made as described
in Example 5, with condensation at a force of 25 N/cm.sup.2, heat
application, and vacuum, cross section shown at 125.times..;
[0084] FIGS. 9A-9C are scanning electron micrographs of a
polypropylene mesh made as described in Example 6, with
condensation at a force of 50 N/cm.sup.2, heat application, and
vacuum, at 35.times., 80.times., and 70.times., respectively. FIG.
9D is a light micrograph of a polypropylene mesh made as described
in Example 6, with condensation at a force of 50 N/cm.sup.2, heat
application, and vacuum, cross section shown at 125.times..;
[0085] FIGS. 10A-10C are scanning electron micrographs of a
polypropylene mesh made as described in Example 7, with
condensation at a force of 75 N/cm.sup.2, heat application, and
vacuum, at 35.times., 80.times., and 70.times., respectively. FIG.
10D is a light micrograph of a polypropylene mesh made as described
in Example 7, with condensation at a force of 75 N/cm.sup.2, heat
application, and vacuum, cross section shown at 125.times..;
[0086] FIGS. 1A-11C are scanning electron micrographs of a
polypropylene mesh made as described in Example 8, with
condensation at a force of 100 N/cm.sup.2, heat application, and
vacuum, at 35.times., 80.times., and 70.times., respectively. FIG.
11D is a light micrograph of a polypropylene mesh made as described
in Example 4, with condensation at a force of 100 N/cm.sup.2, heat
application, and vacuum, cross section shown at 125.times..;
[0087] FIGS. 12A-12C are scanning electron micrographs of a
polypropylene mesh made as described in Example 9, with
condensation at a force of 125 N/cm.sup.2 heat application, and
vacuum, at 35.times., 80.times., and 70.times., respectively. FIG.
12D is a light micrograph of a polypropylene mesh made as described
in Example 9, with condensation at a force of 125 N/cm.sup.2, heat
application, and vacuum, cross section shown at 125.times..;
[0088] FIGS. 13A-13C are scanning electron micrographs of a
polypropylene mesh made as described in Example 10, with
condensation at a force of 250 N/cm.sup.2, heat application, and
vacuum, at 35.times., 80.times., and 70.times., respectively. FIG.
13D is a light micrograph of a polypropylene mesh made as described
in Example 10, with condensation at a force of 250 N/cm.sup.2, heat
application, and vacuum, cross section shown at 125.times..;
[0089] FIGS. 14A-14D are light micrographs of hemotoxylin and eosin
(H&E) stained 6 mil polypropylene meshes in cross section;
[0090] FIGS. 14A and 14C show a non-condensed mesh after
implantation for 28 days at 100.times. and 200.times.,
respectively;
[0091] FIGS. 14B and 14D show a mesh condensed at a force of 75
N/cm.sup.2, heat application, and vacuum, after implantation for 28
days at 100.times. and 200.times., respectively;
[0092] FIGS. 15A-15D are light micrographs of trichrome stained 6
mil polypropylene meshes in cross section;
[0093] FIGS. 15A and 15C show a non-condensed mesh after
implantation for 28 days at 100.times. and 200.times.,
respectively; and
[0094] FIGS. 15B and 15D show a mesh condensed at a force of 75
N/cm.sup.2, heat application, and vacuum, after implantation for 28
days at 100.times. and 200.times., respectively.
DETAILED DESCRIPTION
[0095] Referring to the figures, FIG. 1 illustrates one embodiment
of the present methods. While the methods are described further
below, they can include the steps of extruding and orienting a
polymer into a monofilament fibre; converting the fibre into a
surgical mesh; heat setting the surgical mesh; condensing the
surgical mesh to a predetermined density; reducing the thickness,
void area, and surface contact area of the surgical mesh; forming
the surgical mesh into a three-dimensional structure (a
subassembly); converting the subassembly into a predetermined
shape; cleaning the implant; and packaging and sterilizing the
implant.
[0096] It will be appreciated that the method described with
reference to FIG. 1 is one method according to the invention.
However other methods, including only some of the steps described
with reference to FIG. 1, also fall within the scope of the
invention is suit. It is not essential that all of the steps
described with reference to FIG. 1 be included in the method of the
invention.
[0097] Referring to FIGS. 2A and 2B, schematics of an uncondensed
surgical mesh in cross section corresponding to the surgical mesh
described in Example 3 and shown in FIG. 6D, monofilament fibres 10
have substantially round or oval perimeters and varying cross
sectional area 12 depending upon the plane of the section. Upon
implantation, monofilament fibres 10 are in contact with
surrounding tissue 14. Where monofilament fibres 10 are in direct
contact, a portion of the perimeter 16 is unavailable to contact
surrounding tissue 14.
[0098] Referring to FIGS. 3A and 3B, schematics of a condensed
surgical mesh in cross section corresponding to the surgical mesh
described in Example 6 and shown in FIG. 10D, the perimeters of
monofilament fibres 10 have been altered relative to those of the
uncondensed mesh while the total cross sectional area remains
constant. Thus, the value of the perimeter in contact with tissue
upon implantation and the void area 18 within the implant available
for tissue infiltration are both reduced in a condensed mesh
relative to an uncondensed mesh.
[0099] Referring to FIG. 4A, a scanning electron micrograph of
uncondensed polypropylene surgical mesh, monofilament fibres 10 are
used to knit a mesh of large pore 20 construction that permits
tissue ingrowth upon implantation. Stitch loop intersections 22 are
created during the knitting process. The surgical mesh is sold as
Prolene.TM. Mesh (Ethicon, Somerville, N.J., USA). Referring to
FIG. 4B, condensation zones 24 are created at stitch loop
intersections 22 following the application of vacuum, heat, and
pressure, which compresses monofilament fibres 10 into shapes
having lower profiles. Nonelastic fibres 26 are applied to the
surgical mesh of FIG. 4C to generate a composite implant.
[0100] Referring to FIG. 5A, a scanning electron micrograph of
uncondensed polypropylene surgical mesh, monofilament fibres 10 are
used to knit a mesh of large pore 20 construction that permits
tissue ingrowth upon implantation. Stitch loop intersections 22 are
created during the knitting process. The surgical mesh is sold as
Prolene Soft.TM. Mesh (Ethicon, Somerville, N.J., USA). Referring
to FIG. 5B, a scanning electron micrograph of uncondensed
polypropylene surgical mesh, multifilament fibres 28 are used to
knit a mesh of large pore 20 construction that permits tissue
ingrowth upon implantation. Stitch loop intersections 22 are
created during the knitting process. The surgical mesh is sold as
Mersilene.TM. Mesh (Ethicon, Somerville, N.J., USA).
[0101] Referring to FIGS. 6A and 6B, scanning electron micrographs
of uncondensed polypropylene mesh are shown at 35.times. and
80.times., respectively. Monofilament fibres 10 are used to knit
the mesh into a large pore 20 construction which permits tissue
ingrowth upon implantation. Stitch loop intersections 22 are
created during the knitting process. Referring to FIG. 6C, a
scanning electron micrograph of uncondensed polypropylene mesh, the
surgical mesh thickness profile 30 is determined by the distance
between monofilament fibres 10 from a first side to a second side
of the surgical mesh (e.g., from the back to the front). Referring
to FIG. 6D, a light micrograph of an uncondensed surgical mesh
cross section shown at 10.times.. The area of void for tissue
infiltration 18 is identified and the monofilament fibres 10 having
substantially round or oval perimeters and varying cross-sectional
area 12 depending on the plane of the section. Where monofilament
fibres 10 are in direct contact, a portion of the perimeter 16 is
unavailable to contact surrounding tissue 14.
[0102] Referring to FIGS. 7A and 7B, scanning electron micrographs
of polypropylene mesh condensed under vacuum, heat, and a force of
10 N/cm.sup.2, magnified 35.times. and 80.times., respectively.
Monofilament fibres 10 are used to knit the mesh into a large pore
20 construction which permits tissue ingrowth. Stitch loop
intersections 22 are created during the knitting process.
Condensation zones 24 are beginning to appear. Referring to FIG.
7C, a scanning electron micrograph of a cross section of a
polypropylene mesh condensed under vacuum, heat, and a force of 10
N/cm.sup.2, magnified 70.times.. The surgical mesh thickness
profile 30 is determined by the distance between monofilament
fibres 10 at the front and back of the condensed surgical mesh.
Referring to FIG. 7D, a light micrograph of a surgical mesh cross
section condensed under vacuum, heat, and a force of 10 N/cm.sup.2
shown at 10.times.. The area of void for tissue infiltration 18 is
outlined and the monofilament fibres 10 having substantially round
or oval perimeters and varying cross-sectional area 12 depending on
the plane of the section. Where monofilament fibres 10 are in
direct contact, a portion of the perimeter 16 is unavailable to
contact surrounding tissue 14.
[0103] Referring to FIGS. 8A and 8B, scanning electron micrographs
of polypropylene mesh condensed under vacuum, heat, and a force of
25 N/cm.sup.2, magnified 35.times. and 80.times., respectively.
Monofilament fibres 10 are used to knit the mesh into a large pore
20 construction which permits tissue ingrowth. Stitch loop
intersections 22 are created during the knitting process.
Condensation zones 24 are shown. Referring to FIG. 8C, a scanning
electron micrograph of a cross section of a polypropylene mesh
condensed under vacuum, heat, and a force of 25 N/cm.sup.2,
magnified 70.times.. The surgical mesh thickness profile 30 is
determined by the distance between monofilament fibres 10 at the
front and back of the condensed surgical mesh. Referring to FIG.
8D, a light micrograph of a surgical mesh cross section Condensed
under vacuum, heat, and a force of 25 N/cm.sup.2 shown at
10.times.. The area of void for tissue infiltration 18 is outlined
and the monofilament fibres 10 having substantially round or oval
perimeters and varying cross-sectional area 12 depending on the
plane of the section. Where monofilament fibres 10 are in direct
contact, a portion of the perimeter 16 is unavailable to contact
surrounding tissue 14.
[0104] Referring to FIGS. 9A and 9B, scanning electron micrographs
of polypropylene mesh condensed under vacuum, heat, and a force of
50 N/cm.sup.2, magnified 35.times. and 80.times., respectively.
Monofilament fibres 10 are used to knit the mesh into a large pore
20 construction which permits tissue ingrowth. Stitch loop
intersections 22 are created during the knitting process.
Condensation zones 24 are readily apparent. Referring to FIG. 9C, a
scanning electron micrograph of a cross section of a polypropylene
mesh condensed under vacuum, heat, and a force of 50 N/cm.sup.2,
magnified 70.times.. The surgical mesh thickness profile 30 is
determined by the distance between monofilament fibres 10 at the
front and back of the condensed surgical mesh. Referring to FIG.
9D, a light micrograph of a surgical mesh cross section condensed
under vacuum, heat, and a force of 50 N/cm.sup.2 shown at
10.times.. The area of void for tissue infiltration 18 is outlined
and the monofilament fibres 10 having substantially round or oval
perimeters and varying cross-sectional area 12 depending on the
plane of the section. Where monofilament fibres 10 are in direct
contact, a portion of the perimeter 16 is unavailable to contact
surrounding tissue 14.
[0105] Referring to FIGS. 10A and 10B, scanning electron
micrographs of polypropylene mesh condensed under vacuum, heat, and
a force of 75 N/cm.sup.2, magnified 35.times. and 80.times.,
respectively. Monofilament fibres 10 are used to knit the mesh into
a large pore 20 construction which permits tissue ingrowth. Stitch
loop intersections 22 are created during the knitting process.
Condensation zones 24 are readily visible. Referring to FIG. 10C, a
scanning electron micrograph of a cross section of a polypropylene
mesh condensed under vacuum, heat, and a force of 75 N/cm.sup.2,
magnified 70.times.. The surgical mesh thickness profile 30 is
determined by the distance between monofilament fibres 10 at the
front and back of the condensed surgical mesh. Referring to FIG.
10D, a light micrograph of a surgical mesh cross section condensed
under vacuum, heat, and a force of 75 N/cm.sup.2 shown at
10.times.. The area of void for tissue infiltration 18 is outlined
and the monofilament fibres 10 having substantially round or oval
perimeters and varying cross-sectional area 12 depending on the
plane of the section. Where monofilament fibres 10 are in direct
contact, a portion of the perimeter 16 is unavailable to contact
surrounding tissue 14.
[0106] Referring to FIGS. 1A and 1B, scanning electron micrographs
of polypropylene mesh condensed under vacuum, heat, and a force of
100 N/cm.sup.2, magnified 35.times. and 80.times., respectively.
Monofilament fibres 10 are used to knit the mesh into a large pore
20 construction which permits tissue ingrowth. Stitch loop
intersections 22 are created during the knitting process.
Condensation zones 24 are readily visible. Referring to FIG. 11C, a
scanning electron micrograph of a cross section of a polypropylene
mesh condensed under vacuum, heat, and a force of 100 N/cm.sup.2,
magnified 70.times.. The surgical mesh thickness profile 30 is
determined by the distance between monofilament fibres 10 at the
front and back of the condensed surgical mesh. Referring to FIG.
11D, a light micrograph of a surgical mesh cross section condensed
under vacuum, heat, and a force of 100 N/cm.sup.2 shown at
10.times.. The area of void for tissue infiltration 18 is outlined
and the monofilament fibres 10 having substantially round or oval
perimeters and varying cross-sectional area 12 depending on the
plane of the section. Where monofilament fibres 10 are in direct
contact, a portion of the perimeter 16 is unavailable to contact
surrounding tissue 14.
[0107] Referring to FIGS. 12A and 12B, scanning electron
micrographs of polypropylene mesh condensed under vacuum, heat, and
a force of 125 N/cm.sup.2, magnified 35.times. and 80.times.,
respectively. Monofilament fibres 10 are used to knit the mesh into
a large pore 20 construction which permits tissue ingrowth. Stitch
loop intersections 22 are created during the knitting process.
Condensation zones 24 are readily visible. Referring to FIG. 12C, a
scanning electron micrograph of a cross section of a polypropylene
mesh condensed under vacuum, heat, and a force of 125 N/cm.sup.2,
magnified 70.times.. The surgical mesh thickness profile 30 is
determined by the distance between monofilament fibres 10 at the
front and back of the condensed surgical mesh. Referring to FIG.
12D, a light micrograph of a surgical mesh cross section condensed
under vacuum, heat, and a force of 125 N/cm.sup.2 shown at
10.times.. The area of void for tissue infiltration 18 is outlined
and the monofilament fibres 10 having substantially round or oval
perimeters and varying cross-sectional area 12 depending on the
plane of the section. Where monofilament fibres 10 are in direct
contact, a portion of the perimeter 16 is unavailable to contact
surrounding tissue 14.
[0108] Referring to FIGS. 13A and 13B, scanning electron
micrographs of polypropylene mesh condensed under vacuum, heat, and
a force of 250 N/cm.sup.2, magnified 35.times. and 80.times.,
respectively. Monofilament fibres 10 are used to knit the mesh into
a large pore 20 construction which permits tissue ingrowth. Stitch
loop intersections 22 are created during the knitting process.
Condensation zones 24 are readily visible. Referring to FIG. 13C, a
scanning electron micrograph of a cross section of a polypropylene
mesh condensed under vacuum, heat, and a force of 250 N/cm.sup.2,
magnified 70.times.. The surgical mesh thickness profile 30 is
determined by the distance between monofilament fibres 10 at the
front and back of the condensed surgical mesh. Referring to FIG.
12D, a light micrograph of a surgical mesh cross section condensed
under vacuum, heat, and a force of 250 N/cm.sup.2 shown at
10.times.. The area of void for tissue infiltration 18 is outlined
and the monofilament fibres 10 having substantially round or oval
perimeters and varying cross-sectional area 12 depending on the
plane of the section. Where monofilament fibres 10 are in direct
contact, a portion of the perimeter 16 is unavailable to contact
surrounding tissue 14.
[0109] Referring to FIGS. 14A and 14C, a light micrograph of an
H&E stained 6 mil uncondensed polypropylene mesh placed
subcutaneously in tissue for 28 days, at magnifications of
100.times. and 200.times., respectively. Monofilament fibres 10 and
the cross sectional areas therein 12 are visible. Inflammatory
cells 40 are present in surrounding tissue 14. Fewer inflammatory
cells 40 are present around monofilament fibres 10 not in direct
contact with tissue 16. Referring to FIGS. 14B and 14D, a light
micrograph of an H&E stained 6 mil polypropylene mesh condensed
under vacuum, heat, and a force of 75 N/cm.sup.2 and placed
subcutaneously in tissue for 28 days, at magnifications of
100.times. and 200.times., respectively. Monofilament fibres 10 and
the cross sectional areas therein 12 are visible. Inflammatory
cells 40 are present in surrounding tissue 14. Fewer inflammatory
cells 40 are present around monofilament fibres 10 not in direct
contact with tissue 16.
[0110] Referring to FIGS. 15A and 15C, a light micrograph of a
trichrome stained 6 mil uncondensed polypropylene mesh placed
subcutaneously in tissue for 28 days, at magnifications of
100.times. and 200.times., respectively. Monofilament fibres 10 and
the cross sectional areas therein 12 are visible. Collagen/scar
tissue formation 42 is present around the perimeter of monofilament
fibres 10 in contact with tissue 14. Referring to FIGS. 15B and
15D, a light micrograph of a trichrome stained 6 mil polypropylene
mesh condensed under vacuum, heat, and a force of 75 N/cm.sup.2 and
placed subcutaneously in tissue for 28 days, at magnifications of
100.times. and 200.times., respectively. Monofilament fibres 10 and
the cross sectional areas therein 12 are visible. Collagen/scar
tissue formation 42 is present around the perimeter of the fibres
in contact with tissue 14. The thickness of the surgical mesh
influences the amount of collagen/scar tissue formation 42 as the
body responds to an implant by filling voids. The density and
organization of the collagen/scar tissue formation is higher for
thinner implants with reduced surface area.
[0111] Preliminary studies suggest the implants described herein
have better properties than many existing devices. Some of the
parameters described below are useful in characterizing the
improvements.
[0112] Void Area Ratio=A.sub.V/A.sub.f where A.sub.f is the area of
the fibre cross sections and A.sub.V is the area of void for tissue
infiltration. This ratio is particularly important at fibre
intersections within the surgical mesh fabric because A.sub.V can
increase in these regions when a stitch loop intersection is
created. Consequently, a reduced void area is present in the
condensed surgical mesh, which can lead to reduced levels of
inflammation and scar tissue formation. The devices of the
invention can have a Void Area Ratio of 1.50 or lower, whether
calculated for the device as a whole or a portion thereof (e.g., at
stitch loop intersections or in certain regions of the surgical
mesh).
[0113] Surface Contact Ratio=P.sub.fc/P.sub.f where P.sub.fc is the
perimeter of fibres in contact with tissue for a cross section of
the surgical mesh implant and P.sub.f is the perimeter of fibre for
a cross section of the surgical mesh implant. This ratio is
particularly important at fibre intersections within the surgical
mesh fabric because the amount of fibre can increase in these
regions when a stitch loop intersection is created. For uncondensed
surgical meshes, the Surface Contact Ratio is estimated to approach
1.00 as the fibres are in direct contact only at isolated points
and the majority of the fibres present are in contact with tissue.
Reduced surface contact between the fibre and tissue is present in
the condensed surgical mesh, which can lead to reduced levels of
inflammation and scar tissue formation. The devices described
herein can have a Surface Contact Ratio of 0.80 or lower whether
calculated for the device as a whole or a portion thereof (e.g., at
stitch loop intersections or in certain regions of the surgical
mesh).
[0114] The geometry of the surface contact area of surgical mesh
can also be important. The geometry of the condensation zone within
condensed surgical meshes is more uniform and distributes force to
tissue more evenly. The value for surface contact area under a
controlled load can be measured using pressure sensitive film. The
surgical mesh is placed adjacent to a pressure sensitive film
(e.g., a film containing microcapsules that change colour under
certain loads). Film for measuring such values is available under
the trade name Prescale.TM. (Fujifilm). The surface contact area of
the condensed surgical mesh under a controlled load can be measured
in this manner. Surface contact areas for surgical meshes of a
known density can be compared at different loads. Ideally, a light
weight and low surface area surgical mesh with a low area density
would have an increase in surface contact area with tissue under a
given load to minimize irritation at isolated points. Increased
surface contact area in the outer portion of low weight surgical
meshes with improved void area ratios and surface contact ratios,
may reduce inflammation, tissue reaction, and the erosion of the
surgical mesh into adjacent tissue.
[0115] The material within the implants described herein can have
uniform or non-uniform properties. For example, one or more of the
physical attributes described above (e.g., the void area ratio or
surface contact ratio) can vary at one or more points within the
implant or along the implant's peripheral edge to improve suture or
staple retention strength. For example, where the implant is a
sheet of mesh, the periphery (e.g., about 1/8 to about 7/8 inches
around the perimeter of the device) can remain uncondensed or be
condensed to a lesser extent than the mesh within the periphery.
The strength of material along the peripheral edges (e.g., the
tensile strength), or at other selected points within the device,
may be higher to improve the physical properties in this region so
that sutures or other fixation devices do not pull out and cause
failure. The material content in these regions can also be
increased relative to that of the starting mesh to improve the
physical properties of the device (e.g., additional material can be
added to reinforce one or more points within the device). In one
embodiment, attachment points such as reinforced areas or openings
are created within the device (e.g., along the device's edge) for
receiving sutures, staples, adhesives, and the like. The attachment
points can also be used to attach separate panels to one another to
create the surgical mesh implant. Accordingly, in specific
embodiments, the devices can include means to facilitate coupling
of an attachment element to the device (e.g., an opening for
receiving an attachment element). In some instances, the device can
further include all or part of an attachment element (e.g., a
staple, suture, or adhesive) to facilitate attachment of the device
to body tissue of a patient. The adhesive can be any biological
glue or physiologically acceptable adhesive.
[0116] Alternatively, or in addition, the implant can include areas
that have been adapted to increase the coefficient of friction and
thereby inhibit the implant's movement in the tissue. Supporting
materials, which may be included to facilitate attachment to a
fastener or to generally reinforce the implant, can be shape memory
materials (e.g., shape memory alloys such as Nitinol.TM.). More
generally, any of the implants can include a shape memory material
such as Nitinol.TM. to facilitate sizing, attachment, and
implantation.
[0117] The means to maintain the device in position relative to a
patient's tissue (i.e., an engagement means) can be employed after
implantation or deployment. Where the shape of the device alone is
not sufficient to maintain its position, the engagement means can
be employed after implantation or deployment. The engagement means
can include one or more protrusions (e.g., a plurality of
protrusions arranged in a wave-like or dimple-like pattern).
Undulating elements may be in phase, with force-displacement
characteristics suitable for placement and support.
[0118] The overall shape of the implants can vary tremendously and
will be selected for use depending upon the size of the individual
to be treated and/or the tissue to be repaired. The overall length,
width, and shape of the implants can be varied and designed to
support a certain area. In one embodiment, the implant includes
separate panels that are positioned individually to support a
tissue defect. Devices made by the methods described herein can be
produced in various three-dimensional forms to facilitate placement
and sizing. Generally, the implant can be configured to conform to
the shape of the tissue requiring repair. For example, an implant
having a curvature can be used to construct a substantially conical
shape, and materials can be readily configured to extend
circumferentially around a tissue. Essentially any substantially
two-dimensional soft tissue implant can be thermoformed into a
three-dimensional shape after condensing the surgical mesh.
[0119] In one case, a portion of the biocompatible material is
movable from a delivery configuration to a deployment
configuration. Preferably the delivery configuration is of a
lower-profile than the deployment configuration. The device
comprises means to support the portion of the biocompatible
material in the deployment configuration.
[0120] Biocompatible materials useful in monofilament fibre 10 or
multifilament fibre 28 can include non-absorbable polymers such as
polypropylene, polyethylene, polyethylene terephthalate,
polytetrafluoroethylene, polyaryletherketone, nylon, fluorinated
ethylene propylene, polybutester, and silicone, or copolymers
thereof (e.g., a copolymer of polypropylene and polyethylene);
absorbable polymers such as polyglycolic acid (PGA), polylactic
acid (PLA), polycaprolactone, polydioxanone and
polyhydroxyalkanoate, or copolymers thereof (e.g., a copolymer of
PGA and PLA); or tissue based materials (e.g., collagen or other
biological material or tissue obtained from the patient who is to
receive the implant or obtained from another person or source
(e.g., an animal source)). The polymers can be of the D-isoform,
the L-isoform, or a mixture of both. An example of a biocompatible
fibre 10 suitable for producing the surgical mesh implant is
polypropylene. Non-absorbable polymers and copolymers are not
substantially resorbed by the body over time, whereas absorbable
polymers degrade, to at least some appreciable extent, over time.
Polymers and copolymers within commercially available surgical
products, including currently available surgical meshes, are
suitable for use with the present implants.
[0121] One or more layers or pieces of absorbable and
non-absorbable mesh can be joined within the implant. For example,
an implant can include a nonabsorbable material and an absorbable
material of the same size and shape as the nonabsorbable material
or a portion thereof. The absorbable material can be configured to
reduce the elasticity of the implant and can be thermally attached
to the nonabsorbable material.
[0122] In some embodiments, biocompatible material within the
implant is shaped to distribute the stabilizing and/or supporting
force exerted against tissue. The biocompatible material may
comprise a surface that distributes forces against the tissue
evenly.
[0123] Given the woven or knitted configuration of the mesh, the
devices can facilitate tissue ingrowth and/or cellular infiltration
and are porous. The pores within the devices can be arranged in
regular or irregular patterns. For example, a material can include
a plurality of pores of a first type (e.g., a first size and/or
shape) arranged into a first pattern and of a second type (e.g., a
second size or shape) arranged into a second pattern. The size of
the pores can vary, and can be greater than 50 .mu.m. In specific
embodiments, one or more of the pores in the plurality has a
diameter, measured along the longest axis of the pore, of about 10
to about 10,000 .mu.m (e.g., about 10, 50, 100, 200, 500, 1,000,
2,500, 5,000, 6,000, 7,000, 8,000, or 9,000 .mu.m). The pores can
vary in shape and, either before or after condensation, may be
essentially round, oval, hexagonal or diamond-shaped. One or more
of the pores of the plurality may be substantially the same shape
as the pores shown in FIG. 6.
[0124] The biocompatible material can have a relatively high burst
and tensile strength and can have a relatively low co-efficient of
friction. In another case, a portion of the base biocompatible
material can have a relatively high co-efficient of friction. The
devices may also comprise means to determine the magnitude and/or
direction of a force (e.g., a force applied to a portion of the
biocompatible material when in contact with a patient's tissue).
Preferably, the device comprises means to determine the magnitude
and/or direction of a force applied to the material by visual
inspection. In some embodiments, the geometrical configuration of
at least part of the portion of the biocompatible material can be
altered in response to a change in the magnitude and/or direction
of a force applied. For example, a coloured filament can be
incorporated into any of the materials to create a geometry, and
one may use an instrument to measure the magnitude and/or direction
of a force applied to the device. The soft tissue implant may
comprise areas that distribute the force transmitted to the
surrounding tissue more evenly. For example, at the fibre
intersections, raised fibres can create rough areas that increase
the force transmitted to tissue in select areas. Similarly, the
implants can include regions that have reduced cross sectional
areas, which can reduce inflammation and scar tissue build up. This
is especially true at fibre intersections where raised fibres can
increase the cross sectional area.
[0125] The thickness of the implant can also vary and can be less
than about 0.040 inches. For example, a single porous layer of mesh
within the device can be less than about 0.039 inches, 0.038
inches, 0.037 inches, 0.036 inches, 0.035 inches, 0.034 inches,
0.033 inches, 0.032 inches, 0.031 inches, 0.030 inches, 0.029
inches, 0.028 inches, 0.027 inches, 0.026 inches, 0.025 inches,
0.024 inches, 0.023 inches, 0.022 inches, 0.021 inches, 0.020
inches, 0.019 inches, 0.018 inches, 0.017 inches, 0.016 inches,
0.015 inches, 0.014 inches, 0.013 inches, 0.012 inches, 0.011
inches, 0.010 inches, 0.009 inches, 0.008 inches, 0.007 inches,
0.006 inches, 0.005 inches, 0.004 inches, 0.003 inches, 0.002
inches, or about 0.001 inch. However, a given implant can include
more than one layer of mesh or regions in which some portion of the
mesh is covered with a second layer. For example, an implant can
include a first porous biocompatible surgical mesh and a second
porous biocompatible surgical mesh, the thickness of the implant
being less than about 0.080 inches.
[0126] The implants can be produced by extruding a biocompatible
polymer into a fibre and forming a surgical mesh implant using a
textile based process. As noted, the implants are designed to
engage a tissue defect and can include a bioresorbable or
biodegradable material that will stay in position and support the
tissue defect over a predetermined time. The implants can be
produced by a number of different methods. In one embodiments, the
implants are produced by extruding a first biocompatible polymer to
form a fibre; forming a surgical mesh fabric from the fibre; heat
setting the surgical mesh fabric; applying a nonelastic
biocompatible material to the surgical mesh fabric; compressing the
surgical mesh fabric to a predetermined density; reducing the
thickness and roughness of the surgical mesh fabric; forming the
surgical mesh fabric into a three-dimensional structure; and
cutting the soft tissue implant into a predetermined shape. In this
method or any other, the method may further include the steps of
cleaning and/or sterilizing the implant. Once formed, the implants
can be packaged for sale or distribution.
[0127] Other methods include: extruding a first biocompatible
polymer to form a fibre; forming a surgical mesh fabric from the
fibre; compressing the mesh fabric for a controlled period of time
to a predetermined density using a combination of heat and
pressure; heat setting the surgical mesh fabric; reducing the
thickness and roughness of the surgical mesh fabric; forming the
surgical mesh fabric into a three-dimensional structure; and
cutting the soft tissue implant into a predetermined shape.
[0128] Other methods include: extruding a first biocompatible
polymer to form a fibre; forming a surgical mesh fabric from the
fibre; compressing the mesh fabric for a controlled period of time
to a predetermined density using a combination of heat and pressure
with a vacuum source; heat setting the surgical mesh fabric;
compressing the surgical mesh fabric to a predetermined density;
reducing the thickness and roughness of the surgical mesh fabric;
forming the surgical mesh fabric into a three-dimensional
structure; and cutting the soft tissue implant into a predetermined
shape.
[0129] Other methods include: extruding a first biocompatible
polymer to form a fibre; forming a surgical mesh fabric from the
fibre; stretching the surgical mesh fabric under a predetermined
load; heat setting the surgical mesh fabric; applying a nonelastic
biocompatible material to the surgical mesh fabric; compressing the
surgical mesh fabric to a predetermined density; reducing the
thickness and roughness of the surgical mesh fabric; forming the
surgical mesh fabric into a three-dimensional structure; and
cutting the soft tissue implant into a predetermined shape.
[0130] Other methods include: extruding a first biocompatible
polymer to form a fibre; forming a surgical mesh fabric from the
fibre; heat treating the surgical mesh fabric in a manner that
creates a mesh with varying pore dimensions; applying a nonelastic
biocompatible material to the surgical mesh fabric; compressing the
surgical mesh fabric to a predetermined density; reducing the
thickness and roughness of the surgical mesh fabric; forming the
surgical mesh fabric into a three-dimensional structure; and
cutting the soft tissue implant into a predetermined shape.
[0131] Other methods include: extruding a first biocompatible
polymer to form a fibre; forming a surgical mesh fabric from the
fibre; heat setting the surgical mesh fabric; applying a nonelastic
biocompatible material to the surgical mesh fabric; selectively
compressing the surgical mesh fabric in certain regions to a
predetermined density; reducing the thickness and roughness of the
surgical mesh fabric; forming the surgical mesh fabric into a
three-dimensional structure; and cutting the soft tissue implant
into a predetermined shape.
[0132] Other methods include: extruding a first biocompatible
polymer to form a fibre; forming a surgical mesh fabric from the
fibre; heat setting the surgical mesh fabric; applying a nonelastic
biocompatible material to the surgical mesh fabric; selectively
compressing the surgical mesh fabric to varying degrees in certain
regions to a predetermined density; reducing the thickness and
roughness of the surgical mesh fabric; forming the surgical mesh
fabric into a three-dimensional structure; and cutting the soft
tissue implant into a predetermined shape.
[0133] A soft tissue implant can be created with a surface that has
controlled texture and geometry by subjecting the mesh fabric to
the above processes while in contact with a textured surface and
shaped geometry at temperatures and pressures that are sufficient
to permanently alter the surgical mesh implant characteristics.
[0134] Medical applications for the soft tissue implant technology
described herein include but are not limited to procedures for
treating stress urinary incontinence, pelvic floor prolapse, and
hernia repair. The soft tissue implant can be produced or selected
in a variety of shapes and sizes and from a variety of materials
for a particular indication. For example, a surgeon may select a
non-absorbable implant for patients that require permanent
treatment with an implant having long-term durability and strength.
Alternatively, the surgeon may select an absorbable soft tissue
implant for patients that require temporary treatment and tissue
remodelling. Generally, absorbable implants are chosen when
possible to avoid the potential complications associated with a
permanent implant. Consistent with the properties described herein,
the surgeon can move the devices from a delivery configuration to a
deployment configuration, the delivery configuration being of a
lower-profile than the deployment configuration. Implants with a
reduced profile can be produced and implanted in a minimally
invasive fashion; as they are pliable, they can be placed or
implanted through smaller surgical incisions. As the devices are
also porous, they are expected to have improved optical properties,
allowing the surgeon to visualize underlying tissue through the
implant.
EXAMPLES
Example 1
[0135] We constructed an implant using polypropylene surgical mesh.
A section of PML Prolene Mesh (Ethicon, Somerville, N.J., USA) was
combined with a #2 SurgiPro.TM. polypropylene suture (Tyco
Healthcare, North Haven, Conn., USA) to create a composite implant.
The suture material was woven between the surgical mesh in 5 mm
increments. The assembly was brought under vacuum to 160.degree. C.
under a force of 100 N/cm.sup.2 between two layers of Apical 5 mil
polyimide film using a Lauffer RLKV 40/1 vacuum lamination press.
The surgical mesh had a thickness of 0.0193 inches before the
pressure and heat treatment and a thickness of 0.0093 inches after
the treatment. In addition, the composite assembly exhibited a
lower elasticity compared to the untreated (uncondensed) surgical
mesh.
Example 2
[0136] A section of SPMXXL Prolene Mesh (Ethicon, Somerville, N.J.,
USA) was combined with a #2 SurgiPro.TM. polypropylene suture (Tyco
Healthcare, North Haven, Conn., USA) to create a composite implant.
The suture material was woven between the surgical mesh in 5 mm
increments. The assembly was brought under vacuum to 160.degree. C.
under a force of 100 N/cm.sup.2 between two layer of Apical 5 mil
polyimide film using a Lauffer RLKV 40/1 vacuum lamination press.
The surgical mesh had a thickness of 0.0159 inches before the
pressure and heat treatment and a thickness of 0.0090 inches after
the treatment. In addition, the composite assembly exhibited a
lower elasticity compared to the original surgical mesh.
Example 3
[0137] We constructed a knitted polypropylene surgical mesh implant
using 4 mil monofilament polypropylene fibre. The fibre was
produced using Marlex HGX-030-01 polypropylene homopolymer. The
knitted surgical mesh had elasticity in the machine and transverse
directions. A warp knit was employed to give the mesh exceptional
tensile strength and to prevent runs and unravelling. A suitable
mesh is produced when employing the following pattern wheel or
chain drum arrangements: front guide bar, 1-0/1-2/2-3/2-1 and back
guide bar, 2-3/2-1/1-0/1-2. Examples 4-10 are similar. They differ
in the amount of force applied to the mesh, from 10 N/cm.sup.2 to
250 N/cm.sup.2, respectively.
Example 4
[0138] The surgical mesh implant disclosed in Example 3 was
condensation treated. The surgical mesh implant was brought to
155.degree. C. under 10 N/cm.sup.2 with vacuum between two layers
of Kapton 2 mil polyimide film using a Lauffer RLKV 40/1 vacuum
lamination press.
Example 5
[0139] The surgical mesh implant disclosed in Example 3 was
condensation treated. The surgical mesh implant was brought to
155.degree. C. under 25 N/cm.sup.2 with vacuum between two layers
of Kapton 2 mil polyimide film using a Lauffer RLKV 40/1 vacuum
lamination press.
Example 6
[0140] The surgical mesh implant disclosed in Example 3 was
condensation treated. The surgical mesh implant was brought to
155.degree. C. under 50 N/cm.sup.2 with vacuum between two layers
of Kapton 2 mil polyimide film using a Lauffer RLKV 40/1 vacuum
lamination press.
Example 7
[0141] The surgical mesh implant disclosed in Example 3 was
condensation treated. The surgical mesh implant was brought to
155.degree. C. under 75 N/cm.sup.2 with vacuum between two layers
of Kapton 2 mil polyimide film using a Lauffer RLKV 40/1 vacuum
lamination press.
Example 8
[0142] The surgical mesh implant disclosed in Example 3 was
condensation treated. The surgical mesh implant was brought to
155.degree. C. under 100 N/cm.sup.2 with vacuum between two layers
of Kapton 2 mil polyimide film using a Lauffer RLKV 40/1 vacuum
lamination press.
Example 9
[0143] The surgical mesh implant disclosed in Example 3 was
condensation treated. The surgical mesh implant was brought to
155.degree. C. under 125 N/cm.sup.2 with vacuum between two layers
of Kapton 2 mil polyimide film using a Lauffer RLKV 40/1 vacuum
lamination press.
Example 10
[0144] The surgical mesh implant disclosed in Example 3 was
condensation treated. The surgical mesh implant was brought to
155.degree. C. under 250 N/cm.sup.2 with vacuum between two layers
of Kapton 2 mil polyimide film using a Lauffer RLKV 40/1 vacuum
lamination press.
[0145] The void area ratio of the materials described in Examples
3-10 was measured according to method described previously. The
void area ratio measures the ratio of the area of the fibre cross
sections and the area of void for tissue infiltration. This ratio
was measured at fibre intersections within the surgical mesh
fabric. A reduced void area is present in the condensed surgical
mesh. It should be noted, however, that an increase in the force
applied to the monofilament surgical mesh can cause damage to the
fibres, which results in higher void area ratios.
2 Void Area Ratio Product Force (N/cm.sup.2) Void Area Ratio
Example 3 0 3.26 Example 4 10 1.74 Example 5 25 1.22 Example 6 50
0.68 Example 7 75 0.70 Example 8 100 0.56 Example 9 125 2.00
Example 10 250 1.71
[0146] The surface contact ratio of the materials described in
Examples 3-10 was measured according to the method described
previously. The surface contact ratio measures the ratio of the
perimeter of fibres in contact with tissue to the perimeter of
fibres for a cross section. This ratio was measured at fibre
intersections within the surgical mesh fabric. A reduced surface
contact area is present in the condensed surgical mesh.
3 Surface Contact Ratio Product Force (N/cm.sup.2) Surface Contact
Ratio Example 3 0 0.88 Example 4 10 0.91 Example 5 25 0.69 Example
6 50 0.70 Example 7 75 0.52 Example 8 100 0.46 Example 9 125 0.62
Example 10 250 0.76
[0147] The dimensions of the materials described in Examples 3-10,
Prolene Softm mesh, and Mersilene.TM. Mesh were measured according
to ASTM D5947-03 Standard Test Methods for Physical Dimensions of
Solid Plastics Specimens. The thickness of the materials impacts
the cross sectional area of the surgical mesh implants. In
addition, the density of the material provides a measurement to
determine the amount of material as it relates to cross sectional
area. The density should correlate to the Void Area Ratio described
above for condensed surgical mesh implants. The thickness decreases
and the density increases with an increase in the condensation
force applied per unit area.
4 Thickness Product Force (N/cm.sup.2) Thickness (cm) Prolene Soft
.TM. Mesh 0 0.040 Mersilene .TM. Mesh 0 0.024 Example 3 0 0.039
Example 4 10 0.026 Example 5 25 0.021 Example 6 50 0.019 Example 7
75 0.016 Example 8 100 0.015 Example 9 125 0.014 Example 10 250
0.011 Density Product Force (N/cm.sup.2) Density (g/cm.sup.3)
Prolene Soft .TM. Mesh 0 0.081 Mersilene .TM. Mesh 0 0.130 Example
3 0 0.086 Example 4 10 0.097 Example 5 25 0.114 Example 6 50 0.123
Example 7 75 0.143 Example 8 100 0.171 Example 9 125 0.208 Example
10 250 0.237
[0148] The burst strength of the materials described in Examples
3-10, Prolene Soft.TM. mesh, and Mersilene.TM. Mesh was measured
according to ASTM D3787-01 Bursting Strength of Textiles (Constant
Rate of Transverse). Test specimens measuring 90.0 mm wide and 90.0
mm long were loaded into a Zwick tensile test machine with a grip
to grip separation of 1.0 mm and a test speed of 305 mm/min. Burst
strength provides a measurement of the force required to rupture
the surgical mesh implants. In addition, the ratio of
density/thickness to burst strength provides a measurement of
surgical mesh implant strength as it relates to the cross sectional
area. The burst strength increased moderately with increase in the
condensation force applied per unit area up to 125 N/cm.sup.2. The
sample with a condensation force of 250 N/cm.sup.2 showed a
decrease in burst strength.
5 Burst Product Force (N/cm.sup.2) Burst (Fmax N) Prolene Soft .TM.
Mesh 0 274 Mersilene .TM. Mesh 0 129 Example 3 0 194 Example 4 10
222 Example 5 25 210 Example 6 50 225 Example 7 75 223 Example 8
100 209 Example 9 125 227 Example 10 250 195 Density/Burst Ratio
Density (g/cm.sup.3)/Burst Product Force (N/cm.sup.2) (Fmax N)
Prolene Soft Mesh 0 0.00030 Mersilene Mesh 0 0.00101 Example 3 0
0.00044 Example 4 10 0.00044 Example 5 25 0.00054 Example 6 50
0.00055 Example 7 75 0.00064 Example 8 100 0.00082 Example 9 125
0.00092 Example 10 250 0.00121
[0149] The suture retention of the materials described in Examples
3-10, Prolene Soft.TM. mesh, and Mersilene.TM. Mesh was measured
according to ASTM D882-02 Standard Test Method for Tensile
Properties of Thin Plastic Sheeting. Test specimens measuring 25.4
mm wide by 75.0 mm long were loaded into a Zwick tensile test
machine with a grip to grip separation of 3.0 mm and a test speed
of 500 mm/nin. Materials were tested in the machine and transverse
directions. Suture retention provides a measurement of the force
required to disrupt the edge of the material. The suture retention
strength was maintained with an increase in the condensation force
applied per unit area up to 75 N/cm.sup.2. The samples with a
condensation force of 100 and 125 N/cm.sup.2 showed a moderate
decrease in suture retention strength and the samples with a
condensation force of 250 N/cm.sup.2 showed a more significant
decrease.
6 Suture Machine Suture Machine Product Force (N/cm.sup.2) (Fmax N)
Prolene Soft .TM. Mesh 0 24.8 Mersilene .TM. Mesh 0 10.0 Example 3
0 21.2 Example 4 10 20.0 Example 5 25 22.4 Example 6 50 17.4
Example 7 75 20.5 Example 8 100 16.2 Example 9 125 15.6 Example 10
250 9.3 Suture Transverse Suture Transverse Product Force
(N/cm.sup.2) (Fmax N) Prolene Soft .TM. Mesh 0 28.4 Mersilene .TM.
Mesh 0 11.7 Example 3 0 21.4 Example 4 10 20.8 Example 5 25 18.8
Example 6 50 20.2 Example 7 75 20.0 Example 8 100 20.3 Example 9
125 17.3 Example 10 250 12.0
[0150] The stiffness of the materials described in Examples 3-10,
Prolene Soft.TM. mesh, and Mersilene.TM. Mesh was measured
according to ASTM D4032-94 Stiffness of Fabric by the Circular Bend
Procedure. Test specimens measuring 102.0 mm wide and 204.0 mm long
were loaded into a Zwick tensile test machine with a grip to grip
separation of 1.0 mm and a test speed of 300 mm/min. The test
measures the force required to move a specimen through a circular
area. It should be noted that stiffer materials may cause more
irritation to surrounding tissues. The stiffness values of the
condensed surgical mesh were equivalent to the uncondensed with
increase in the condensation force applied per unit area up to 125
N/cm.sup.2. The sample with a condensation force of 250 N/cm.sup.2
showed an increase in stiffness.
7 Stiffness Product Force (N/cm.sup.2) Stiffness (Fmax N) Prolene
Soft .TM. Mesh 0 3.13 Mersilene .TM. Mesh 0 0.55 Example 3 0 2.35
Example 4 10 1.90 Example 5 25 2.35 Example 6 50 2.16 Example 7 75
2.03 Example 8 100 2.37 Example 9 125 2.34 Example 10 250 2.98
[0151] The tensile strength of the materials described in Examples
3-10, Prolene Soft.TM. mesh, and Mersilene.TM. Mesh was measured
according to ASTM D882-02 Standard Test Method for Tensile
Properties of Thin Plastic Sheeting. Test specimens measuring 10.0
mm wide and 100.0 mm long were loaded into a Zwick tensile test
machine with a grip to grip separation of 50.0 mm and a test speed
of 500 mm/min. Materials were tested in the machine and transverse
directions. Tensile strength provides a measurement of the force
required to rupture the surgical mesh implants under tension. The
tensile strength was maintained with an increase in the
condensation force applied per unit area up to 75 N/cm.sup.2. The
samples with a condensation force of 100 and 125 N/cm.sup.2 showed
a moderate decrease in tensile strength and the samples with a
condensation force of 250 N/cm.sup.2 showed a more significant
decrease.
8 Tensile Machine Product Force (N/cm.sup.2) Tensile Machine (N/cm)
Prolene Soft .TM. Mesh 0 27.75 Mersilene .TM. Mesh 0 27.16 Example
3 0 21.76 Example 4 10 21.70 Example 5 25 23.14 Example 6 50 21.46
Example 7 75 24.37 Example 8 100 21.20 Example 9 125 19.94 Example
10 250 15.31 Tensile Transverse Tensile Transverse Product Force
(N/cm.sup.2) (N/cm) Prolene Soft .TM. Mesh 0 20.97 Mersilene .TM.
Mesh 0 15.04 Example 3 0 17.37 Example 4 10 16.69 Example 5 25
17.55 Example 6 50 18.02 Example 7 75 16.29 Example 8 100 16.41
Example 9 125 15.40 Example 10 250 12.39
Example 11
[0152] We constructed a knitted polypropylene surgical mesh implant
using 4 mil monofilament polypropylene fibre. The fibre was
produced using Marlex HGX-030-01 polypropylene homopolymer. A warp
knit was employed to give the mesh exceptional tensile strength and
to prevent runs and unravelling. A suitable mesh is produced when
employing the following pattern wheel or chain drum arrangements:
front guide bar, 1-0/1-2/2-3/2-1 and back guide bar,
2-3/2-1/1-0/1-2. The knitted surgical mesh had elasticity in the
machine and transverse directions. The elasticity, however, was not
uniform in the machine and transverse directions. The elasticity
was higher in the transverse direction compared to the machine
direction. To compensate for this difference, a sample measuring 33
cm in the machine direction and 45 cm in the transverse direction
was stretched to 48 cm in the transverse direction while being held
at 33 cm in the machine direction. The surgical mesh implant, while
being held under tension, was condensation treated. The surgical
mesh implant was brought to 155.degree. C. under 75 N/cm.sup.2 with
vacuum between two layers of Kapton 2 mil polyimide film using a
Lauffer RLKV 40/1 vacuum lamination press. The difference in
elasticity between the transverse and machine directions was
reduced.
[0153] A number of embodiments of the invention have been
described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention.
* * * * *