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Synthetic Mesh Choices
Sean B. Orenstein, MD and Yuri W. Novitsky, MD, FACS
1. Introduction to Synthetic Mesh Materials
C HAPT E R
19
for Surgical Repair
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2. Mesh Characteristics (Table 19-1)
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Modern herniorrhaphy relies on the use of prosthetic implants to allow for tension-free
repairs of hernia defects. Such widespread use of mesh implants has greatly reduced the
incidence of hernia recurrence. Surgeons continuously seek the ideal mesh—pliable and
durable with chemical inertness and limited immunogenicity. Synthetic meshes have been
used for over half a century, since Dr. Francis Usher popularized the use of polypropylene in the late 1950s. However, only recently have there been any changes in their original design. Current manufacturing techniques involve modifications of mesh polymers,
reduction in fiber density, increase in pore size, and combinations of the above in attempts
to create an “ideal mesh” to replace native fascia during hernia repair.
1. Material
Polypropylene constitutes the most common polymer used in surgical meshes. It is highly
durable and has been proved successful in hernia repairs for over 50 years. Because of
unraveling at the edges when cut, current meshes are typically knitted instead of woven.
While still popular because of its strength, durability, and pliability, polypropylene meshes
are not without their drawbacks. Traditional polypropylene induces a strong inflammatory
reaction upon implantation. Such inflammation can lead to excessive fibrosis, loss of pliability, and chronic pain. Additionally, when exposed to bowel, uncoated polypropylene
may lead to extensive adhesions and/or fistulas.
Polyester is a hydrophilic polymer incorporated into meshes. It has been manufactured as
a 2-dimensional (flat) sheet or a 3-dimensional sheet to allow for greater incorporation of
host tissues. One of the advantages of polyester is its pliability, which allows the surgeon to
easily manipulate and fixate the mesh to the conformations of the abdominopelvic walls.
Polyester is unique in its hydrophilic nature; however, the clinical relevance of this feature remains unknown. Like polypropylene, unprotected polyester can lead to significant
inflammatory reactions with ensuing fibrosis, adhesions, and fistulas.
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Chapter 19 • Synthetic Mesh Choices for Surgical Repair 323
Table 19-1 Synthetic Mesh Characteristics
MATERIAL MESH PRODUCT MANUFACTURER MESH CHARACTERISTICS
Standard Meshes
Polypropylene Prolene Ethicon
Heavyweight – 105 g/m
Marlex C.R. Bard Heavyweight – 95 g/m
Microporous – 0.6 mm
Trelex Boston Scientific Heavyweight – 95 g/m
Microporous – 0.6 mm
ProLite Atrium Midweight – 85 g/m
Microporous – 0.8 mm
ProLite Ultra Atrium Lightweight – 50 g/m
Microporous – 0.75 mm
Prolene Soft Ethicon Lightweight – 45 g/m
Macroporous – 2.4 mm
Soft Mesh C.R. Bard Lightweight – 44 g/m
Macroporous – 6.3 mm
Visilex Mesh C.R. Bard Macroporous – 2.5 mm
Polyester Parietex TET Covidien 3-D mesh
Midweight – 80 g/m
Macroporous – 1.8 × 1.5 mm
Mersilene Ethicon 2-D mesh
Heavyweight, Macroporous
Polytetrafluoroethylene (PTFE) Infinit W.L. Gore Macroporous
Standard Composite Meshes
Polypropylene with poliglecaprone Ultrapro Ethicon Lightweight – 28-40 g/m
Macroporous – 2.0-4.0 mm
Polypropylene with polyglactin Vypro II Ethicon Lightweight – 35 g/m
Anti-adhesion Composite Meshes
Expanded polytetrafluoroethylene (ePTFE) Dualmesh W.L. Gore (solid laminar sheet)
2-sided: Micro- and macroporous*
Dulex
C.R. Bard (solid laminar sheet)
2-sided: Micro- and macroporous*
Polypropylene mesh and ePTFE Composix E/X C.R. Bard Heavyweight, microporous polypro-
pylene (abdominal wall surface) and
microporous ePTFE (anti-adhesion)
Composix L/P C.R. Bard Lightweight, macroporous polypro-
pylene (abdominal wall surface) and
microporous ePTFE (anti-adhesion)
Ventralex C.R. Bard Mesh designed for small defects (e.g.,
umbilical, port site hernias)
Polypropylene mesh + poliglecaprone coating Physiomesh Ethicon Lightweight*
Macroporous – 3 mm
Polypropylene and polyglycolic acid (PGA) mesh +
carboxymethylcellulose-sodium hyaluronate-polyethylene
Sepramesh C.R. Bard Heavyweight – 101 g/m
Microporous – 0.35 mm
glycol (CMC-HA-PEG) coating
Polypropylene and polyglycolic acid (PGA) mesh +
carboxymethylcellulose-sodium hyaluronate-polyethylene
Ventralite C.R. Bard Lightweight – 54 g/m
Microporous – 0.4 mm
glycol (CMC-HA-PEG) coating
Polypropylene mesh with oxidized regenerated cellulose
(ORC) coating
Proceed Ethicon Lightweight – 50 g/m
Macroporous – 2.5 mm
Polypropylene mesh + omega-3 fatty acid coating C-Qur Atrium Midweight – 85 g/m
Microporous – 0.8 mm
C-Qur Lite Atrium Lightweight – 50 g/m
Microporous – 0.75 mm
3-D Polyester + collagen-polyethylene glycol (PEG) coating Parietex Composite Covidien Midweight – 80 g/m
Macroporous – 1.8 × 1.5 mm
Biodegradable Meshes
Polyglycolic acid:trimethylene carbonate (PGA:TMC) Bio-A W.L. Gore 3D Matrix
Polyglactin Vicryl Ethicon *
*Information not available.
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324 Section VI • Mesh Choices
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2. Weight and Density
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Polytetrafluoroethylene (PTFE) is a carbon and fluorine-based synthetic hydrophobic poly-
mer most commonly recognized in nonstick cookware (Teflon). Laminar or “expanded”
polytetrafluoroethylene (ePTFE) biomaterials for use in hernia repair (Dualmesh, W.L.
Gore) were introduced in 1983. PTFE is a strong and relatively inert biomaterial; it is flexible and soft with resultant ease of handling of the mesh. Until recently, PTFE-based mesh
has been manufactured as solid sheets of expanded PTFE with both microporous and
macroporous (corrugated) surfaces to allow anti-adhesion and tissue ingrowth properties,
respectively. Dualmesh also can be coated with a silver chlorhexadine layer (Dualmesh
Plus, W.L. Gore) to impede mesh infectability.
Newer PTFE-based monofilament mesh (Infinit, W.L. Gore) uses a knitted configuration
instead of a solid laminar sheet. This modification was designed to promote tissue ingrowth
and mesh integration during extraperitoneal implantation.
Studies have shown that traditional “heavyweight” meshes demonstrate four times the
tensile and burst strength of the native abdominal wall. As a result, traditional meshes may
be overengineered for use in most hernia repairs. The latest generation of meshes has been
designed to reduce the amount of implanted prosthetic material. These so-called lightweight meshes are manufactured with thinner filaments and/or larger pore sizes resulting
in markedly reduced mesh “weights,” measured in grams per m2. Such reduction (>50%)
in prosthetic weight potentially allows for a reduced inflammatory reaction, more flexibility, and improved compliance, especially in the long-term.
3. Porosity
Chapter 19 • Synthetic Mesh Choices for Surgical Repair 325
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4. Anti-adhesion Barrier
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In addition to reducing fiber caliber and density, increasing the distance between the mesh
fibers also contributes to overall foreign body reduction. Following implantation, each
mesh fiber is surrounded by some degree of inflammation and fibrosis. Microporous mesh
induces significant perifilamentous fibrosis that tends to blend together, creating a scar
plate. As pore size is increased between fibers, less bridging fibrosis may be observed, with
subsequent reduced scar plate formation. This results in improved fluid transport across
the mesh, theoretically lessening seroma formation. Marlex is considered a microporous
mesh, with a pore size of 0.6 mm. Ultrapro, one of the most macroporous meshes, contains
pore sizes ranging from 2 to 4 mm (diagonal-shaped pores).
The advent of laparoscopic surgery necessitated development of so-called composite meshes.
The principal benefit of these meshes is the ability to strategically place them intraperitoneally to impede adhesion formation on one side while promoting tissue ingrowth on
the other side. While most intraperitoneal meshes incorporate two layers of materials,
Dualmesh (W.L. Gore and Associates, Flagstaff, AZ, USA) is manufactured by the fusion of
two layers of ePTFE. A macroporous layer is corrugated and roughened to promote tissue
ingrowth. This is paired with a microporous layer, which is best suited for the visceral surface by allowing for minimal and filmy adhesions. Accordingly, the smooth microporous
layer is designed to face the peritoneal cavity and the rough macroporous side is to be
placed against the abdominal wall to allow for tissue incorporation.
The ability of ePTFE to resist adhesion formation is also used in Composix EX (C.R. Bard,
Cranston, NJ, USA). This mesh type includes a smooth microporous layer of ePTFE under
a layer of standard polypropylene. The smooth ePTFE surface is positioned toward the
abdominal contents and serves as a protective interface against the bowel. The polypropylene side faces the abdominal wall to be incorporated into the native peritoneum and fascial
tissue. Although it still remains popular, many surgeons have recently been reluctant to
use this product because of fear of potential exposure of polypropylene to the abdominal viscera, stemming from technical errors at implantation or excessive shrinkage of the
ePTFE layer, with resultant increase in adhesion formation and other serious intestinal
complications.
The layers of most other composite meshes consist of a synthetic material and an anti-
adhesion polymer. The peritoneal layer (tissue ingrowth side) is composed of a typical
polypropylene or polyester sheet. Visceral (nonadhesive) surfaces consist of various chemical polymer-based coatings. Today, such coatings include omega-3 fatty acids (C-Qur),
poliglecaprone (Physiomesh), hyaluronic acid (Sepramesh), polyethylene glycol (Parietex),
and oxidized regenerated cellulose (Proceed), among others. These coatings are intended
to persist until neoperitoneum has covered the mesh, typically within 10 to 14 days after
implantation. However, such absorbable adhesion barriers may be damaged by handling
of the mesh during implantation, thus reducing its anti-adhesive properties.
326 Section VI • Mesh Choices
5. Absorbable, Partially Absorbable, and Biodegradable Meshes
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The aforementioned meshes are composed of permanent polymers; however, varieties of
permanent meshes contain absorbable materials. The addition of absorbable fibers such
as polyglactin (Vicryl, Ethicon, Inc) in Vypro composite meshes (Ethicon, Inc) or poliglecaprone (Monocryl, Ethicon, Inc) in Ultrapro adds stiffness to the composite mesh. This
feature is particularly important for the lighter weight meshes to improve mesh handling
during implantation, while reducing the overall foreign material within the patient after
complete resorption of the extra fibers occurs.
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Bio-A (W.L. Gore and Associates) represents the first biodegradable synthetic mesh sheet.
Its intended function is more akin to a biologic mesh prosthetic than a typical knit synthetic mesh, as its biodegradable scaffold is gradually replaced by native collagen. Composed of polyglycolic acid and trimethylene carbonate (similar to a PDS suture material), it
resorbs in approximately 3-6 months. Although this material has a proven record in staple/
suture line reinforcement and hiatal repairs, its efficacy in reinforcement of tensile forces
during abdominal wall reconstructions remains unclear.
3. Clinical Implications of Biomaterials
1. Material Type:
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Polyester, polypropylene, and PTFE remain the three most common synthetic substrates
used for mesh. Although tissue reactions of biomaterials vary greatly in the literature, our
recent experience in rodent experiments demonstrated that the polyester-based mesh was
the greatest inducer of inflammation and appeared to impose a severe chronic foreign
body reaction. While the polypropylene meshes displayed significant inflammation and
some foreign body reaction, the severity was strikingly less when compared to polyester.
Compared to the knit meshes in our study, integration of the laminar ePTFE mesh within
tissues was met more with heavy fibrosis and encapsulation instead of integration. This
has been seen in other in vivo studies and clinically, with excised samples of previously
implanted ePTFE demonstrating significant fibrosis. In addition, decreased neovascularization seen in our study may have further predisposed ePTFE mesh to a diminished
biocompatibility. Heavy fibrosis and encapsulation may lead to mesh shrinkage. Overall,
we found polypropylene to exhibit the highest degree of tissue biocompatibility followed
by ePTFE and, finally, polyester. The clinical implications of these findings are not entirely
clear, and no randomized controlled trials have evaluated these materials in a comparative
fashion.
2. Material Weight
Chapter 19 • Synthetic Mesh Choices for Surgical Repair 327
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Most prosthetics, although chemically inert, generate an intense host inflammatory reac-
tion. The host response to implanted prosthetic biomaterials follows a cascading sequence
of events (coagulation, inflammation, angiogenesis, epithelialization, fibroplasia, matrix
deposition, and contraction) with a resultant formation of dense connective tissue at the
site of implantation. Although this may have an important positive role in mesh incorporation, the increased amount of connective tissue does not necessarily translate to strength
and durability of the hernia repair. A rigid scar plate resulting from pronounced perifilamentous fibrosis and deposition of collagen fibers contributes to the loss of prosthetic
pliability. In the long-term, such acquired stiffness of mesh products contributes to the
changes in compliance of both the hernia site and the whole abdominal wall. Clinically,
this decrease in compliance can lead to a sensation of stiffness and result in both physical discomfort and significant limitations in the activities of daily living in many patients.
The deleterious foreign body effects of synthetic meshes have been linked to the amount
of foreign body implanted. As a result, a goal of modern mesh manufacturers has been
the development of prosthetic implants that are able to meet the tensile demands of the
abdominal wall while limiting the foreign body burden at the site of the repair. Similar to
our previous experience, as well as that of other investigators, our laboratory recently confirmed that lightweight and midweight polypropylene mesh displayed a marked reduction
in fibrosis and foreign body reaction when compared to the heavyweight polypropylene.
Beyond doubt, reduction of the overall “weight” of the mesh implant is associated with a
significant increase in biocompatibility of the prosthetic.
The clinical evidence for the benefits of this theoretical improvement is evolving. In a
recent randomized trial of inguinal herniorrhaphies, the use of lightweight mesh reduced
the foreign body sensation to less than half of that reported with standard densely woven
polypropylene mesh. In addition, physically active patients reported significantly less pain
on exercise. In another series of hernia patients, a reduction of paresthesia from 58%
in the heavyweight group to 4% in the lightweight group was noted. More recently, the
most compelling evidence for the benefits of lightweight mesh to date was published.
In a double-blinded, prospective series of hernia patients with bilateral inguinal defects,
both traditional and lightweight meshes were implanted with each patient being their own
control. One hundred percent of patients were able to point out correctly the side with a
lightweight mesh. The patients reported overall significant decrease in mesh sensation and
pain at the site of implantation. Overall, it appears that the implantation of lightweight
polypropylene mesh results in decreased chronic discomfort and reduced restriction of
physical activities while providing more than adequate strength for the reinforcement of
hernia repairs. It is important to point out, however, that the use of lightweight meshes as a
“bridge” should probably be avoided as it may lead to excessive bulging and, rarely, central
mesh failures. Therefore, we have adopted a policy of highly selective use of lightweight
products. For laparoscopic ventral hernia repairs without defect closure, for rare cases of
“bridging” of defects during open ventral herniorrhaphies, and during laparoscopic repairs
of moderate to large direct inguinal hernias, we advocate the use of midweight or traditional meshes to ensure a durable repair.
328 Section VI • Mesh Choices
3. Microporous vs. Macroporous mesh:
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Although the significance of mesh porosity has been suggested, until recently we found
limited objective evidence linking pore size to biocompatibility. It does appear, however,
that a great deal of importance lies with the fibrotic reactions that take place between the
mesh fibers or fiber bundles. With smaller mesh pores, the fibrosis that surrounds each
mesh fiber bridges with the fibrosis of adjacent mesh fibers. We found that macroporous
meshes contain a “neutral zone” between mesh fibers free of any foreign body and resultant
decrease in host inflammatory response and fibrosis. In fact, when comparing three different polypropylene meshes, we found that biocompatibility was clearly proportional to
the pore size of the mesh. Additionally, the large pore “neutral zones” allow for local tissue
ingrowth while reducing chronic inflammation across the entire mesh.
Macroporous meshes appear to also demonstrate increased ability to resist infection. Recent
European studies demonstrated safe use of macroporous meshes in clean-contaminated
and even contaminated fields. Rapid mesh incorporation is likely a key contributor to
these observations of decreased mesh infection. Additionally, larger pores may improve
fluid transport across the mesh due to a decrease in flow resistance. This, in turn, leads
to more efficient fluid removal, as well as nutrient and oxygen transport, possibly leading
to a reduction in postoperative seromas and faster healing. Overall, there are markedly
improved tissue reactions, decreased fibrosis, and likely decreased infectability in meshes
with larger pore sizes.
4. Other Considerations
1. Anisotropy
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The material properties of meshes contribute to the overall mechanical behavior of the
repair of hernia defects. While the differing elasticity of meshes when pulled in different
directions (i.e. anisotropy) has not been well defined to date, ongoing studies show that
many commonly used meshes have up to 20-fold differences in their stretchability when
pulled in perpendicular directions. This may factor into the success of abdominal wall
repairs, as the native abdominal wall is roughly twice as elastic in the vertical (craniocaudal) axis versus the horizontal axis. As a result, mesh implantation may need to be strategic
in order to address the differences in both the textile properties of the prosthetic and the
physiologic properties of the abdominal wall. However, proper mesh marking to guide
surgeons in properly orienting mesh during implantation is lacking (nor is it required) in
nearly all products on the market today.
2. Pre-shaped mesh
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Chapter 19 • Synthetic Mesh Choices for Surgical Repair 329
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Selected References
Cobb WS, Kercher KW, Heniford BT: The argument for lightweight polypropylene mesh in hernia repair, Surg Innov 12:63–69, 2005.
Junge K, Klinge U, Rosch R, Klosterhalfen B, Schumpelick V: Functional and morphologic properties of a modified mesh for inguinal
hernia repair, World J Surg 26:1472–1480, 2002.
Lichtenstein IL, Shulman AG, Amid PK, Montllor MM: The tension-free hernioplasty, Am J Surg 157:188–193, 1989.
Nilsson E, Haapaniemi S, Gruber G, Sandblom G: Methods of repair and risk for reoperation in Swedish hernia surgery from 1992 to
1996, Br J Surg 85:1686–1691, 1998.
Novitsky YW, Harrell AG, Hope WW, Kercher KW, Heniford BT: Meshes in hernia repair, Surg Technol Int 16:123–127, 2007.
Saberski ER, Orenstein SB, Novitsky YW: Anisotropic evaluation of synthetic surgical meshes, Hernia 15(1):47–52, 2011.
Usher FC, Ochsner J, Tuttle LL Jr: Use of marlex mesh in the repair of incisional hernias, Am Surg 24:969–974, 1958.
In an effort to accommodate abdominopelvic contours during repair, preformed meshes
are available. These meshes are typically used in inguinal repairs and assist surgeons to
laparoscopically place a mesh over the myopectineal orifice without the buckling effect
that may occur when using a flat piece of mesh. In addition, preformed plugs may be used
to “occlude” an indirect inguinal defect. Clear-cut clinical benefits of preshaped meshes
have not been established to date.