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303
25. Synthetic Prosthetic Choices in Ventral Hernia Repair
MotifMESH™ (Proxy Biomedical). Because these mesh are macroporous,
neither of these products are designed for intraperitoneal use.
Coatings
Because of the adverse effects noted clinically with some of the
uncoated mesh materials, newer designs have incorporated coatings.
These meshes are sometimes noted as barrier mesh and are considered
the “second-generation” mesh, with the goal of providing a protective
layer to prevent adhesion to the intraperitoneal contents. There are many
meshes on the market that have been coated with absorbable or permanent
coatings in order to reduce the severity of the in fl ammatory response,
reduce adhesions, and lead to less fi brosis and contraction of the mesh
[ 26 ] . Table 25.1 provides a partial list of some of the currently available
coated mesh.
Studies have shown that these coatings help reduce adhesions and the
severity of the in fl ammatory response. While the short-term outcome is
promising, clinical evidence has also shown that some of the coatings are
Table 25.1. A partial list of commercially available coated mesh.
Brand Coating/mesh
C-Qur (atrium) Omega-3 fatty acid over lightweight
polypropylene
Parietex composite (covidien) Collagen-polyethylene glycol-glycerol over
PET
Proceed (ethicon) Oxidized regenerated cellulose over
polypropylene encapsulated by
polydioxanone
Sepramesh IP composite (Bard) Hydrogel layer (sodium hyaluronate,
carboxymethylcellulose, polyethylene
glycol) over polypropylene co-knitted
with polyglycolic acid fi bers
Ti-Mesh (Biomet, Inc.) Covalently bonded titanized surface over
polypropylene (light- to medium weight)
PolyPro Mesh (STS) Polyether urethane urea over polypropylene
It should be noted that some have microporous coatings which are designed for intra-
abdominal placement and others (Ti-Mesh and PolyPro Mesh) are macroporous and
could induce bowel erosion if place in the peritoneal cavity
304
S.A. Grant
unstable over time and disintegrate, thus potentially leaving the
underlying material susceptible to adhesion formation and materials
degradation [ 27 ] . Durable, longer-lasting coatings are needed for better
long-term clinical outcomes.
Resorbable Mesh Materials
An alternative to permanent synthetic mesh are the resorbable mesh.
Resorbable mesh is attractive due to their reduce risks of adhesion
formations and absence of long-term foreign body responses. The
resorbable mesh is typically composed of copolymerized forms of
polylactic acid, polyglycolic acid, polyglactin, and/or polycaprolactone.
The challenge for absorbable mesh is the degradation rate; too fast of
degradation could result in loss of mesh strength, resulting in recurrences.
Too slow of degradation could result in long-term foreign body responses.
While the number of resorbable mesh on the market is few, a new mesh
currently on the market is TIGR Matrix surgical mesh (Novus Scienti fi c).
TIGR mesh knits two polymers with different resorbable rates, a fast
and a slow degradation rate, so that that strength and integrity of the
mesh is secured while reducing in fl ammatory response. Another recently
available resorbable mesh is GORE BIO-A (W.L. Gore). This resorbable
synthetic has a faster resorption pro fi le and is microporous compared
with TIGR matrix mesh. While resorbable mesh may not be applicable
to every hernia procedure, there may be some procedures where
resorbable mesh will be the mesh of choice.
Choosing the Best Mesh
While polypropylene, PET, and PTFE make up the majority of current
hernia mesh materials, there are over 80 different types of hernia mesh
available [ 1 ] . Given that the properties of the mesh can vary considerably,
choosing the best mesh for a particular patient population and/or
procedure can be confusing. Thus, it is not surprising that investigators
have performed controlled prospective and retrospective case studies in
order to formulate different algorithms and suggestions of mesh usage
[ 28 ] . Unfortunately, there are some inherent concerns with these studies
in that there is usually not enough patient data to support the given
recommendations [ 1 ] .
305
25. Synthetic Prosthetic Choices in Ventral Hernia Repair
Since not all hernias are alike and they can differ signi fi cantly in size
and complexity, the choice of mesh should be based on risk of adhesions,
risk of infections, surgeon familiarity, cost, and patient characteristics. In
particular, patient characteristics such as BMI, diabetes, tobacco use,
second surgeries, previous hernias need to be considered. For example,
in an unpublished study performed by our group, polypropylene mesh
explanted from high BMI patients have shown more adverse foreign
body reaction than mesh explanted from low BMI patients. Studies that
take into account patient demographics need to be performed in order to
fully characterize patient-material effects and eventually be utilized to
develop algorithms that match the best mesh for a particular patient
population.
From a materials point of view, the best mesh would be one where the
engineering properties of the mesh matches the engineering properties of
the abdominal wall. For example, the tensile strength and strain of the
mesh material should be equivalent to that of the abdominal wall.
Excessive tensile strength or overengineered mesh materials may
decrease mesh fl exibility and compliance, which can result in excessive
in fl ammation and scarring. A mesh that is too rigid and is implanted in
compliant abdominal tissue, for example, could incite severe in fl ammatory
responses. Thus, the abdominal wall biomechanics need to be well
understood as well as the mechanics of the mesh materials in order to
design optimal mesh implants for hernia repair.
Many studies have investigated the abdominal wall biomechanics
[ 29 ] . For example, force-elongation response of human abdominal wall
was recently determined using tensile tests [ 29 ] . When applying an
approximately 20 kPa of abdominal pressure, a corresponding biaxial
force of about 3.4 N/mm in the transverse and 1.5 N/mm in the
longitudinal direction occurs along with a compliance ratio of about 2:1
between the longitudinal and transversal directions. When applying a
transverse and longitudinal strains both in the order of 6%, the authors
also determined that Young’s modulus in the transversal direction was
about 50 kPa while the Young’s modulus was about 20 kPa in longitudinal
direction. Studies like these can help develop mathematical models of
the abdominal wall which will assist in optimal mesh design.
There have been many studies that have investigated mesh material
properties [ 30 ] . A recent study by Deeken et al. [ 30 ] investigated
physicomechanical properties of polypropylene, PET, and PTFE hernia
mesh. While most of the mesh materials are overengineered, signi fi cant
differences in mechanical properties were found in relation to orientation
of the mesh, which highlights the need to understand mesh design,
306
S.A. Grant
particularly the weave of the mesh. The design of the weave will dictate
the shape of the interstices and thus in fl uence the overall mechanical
properties and ultimately, the foreign body response. While there are
numerous weave designs for hernia mesh that display hexagonal pores,
square pores, irregular pores, triangulated pores, etc., there has been
would elicit better clinical results. The lack of studies has resulted in a
plethora of mesh designs. In addition, the weave design will impart either
isotropic or anisotropic properties of the mesh. Isotropic mesh designs
display equal mechanical properties in any direction of applied stress,
while anisotropic mesh display different mechanical properties depending
upon the direction of applied stress. Anisotropic mesh design results in a
mesh that is stronger in one direction than in the other so that it may be
possible to initiate different complexities of the foreign body response.
In addition, when stress is applied to mesh (such as coughing, jumping),
Table 25.2. Mesh-tissue response.
Mesh physical characteristics Noted tissue responses
Interstices greater than 75 m m Allows passage of macrophages,
fi broblasts, blood vessels; reduces risk
of infection
Interstices less than 10 m m Leads to rigid scar plate formation due to
granuloma bridging; restricts passages
of macrophages that may lead to
infection
Interstices less than 1.00 mm Leads to rigid scar plate formation
Density (heavyweight vs.
lightweight)
A more severe foreign body reaction (FBR)
is noted with heavyweight mesh
Tensile strengths of synthetic mesh Almost all mesh are overengineered,
causing compliance mismatch between
the mesh and tissue that can result in
enhanced FBR
Strains at physiological loads Mesh with less strain than tissue can result
in enhanced FBR
Coating or composite type of
coating
Initial FBR is reduced, adhesions reduced,
but long-term performance needs to be
characterized
Filament diameter (smaller diameter
fi laments have more compliance,
fl exibility)
Less FBR with smaller diameter fi laments
but too small of fi laments may lead to
breakage
Isotropic or anisotropic behavior of
mesh (based on weave)
Tissue response of different mesh designs
has yet to be investigated
Pore design (hexagonal pores,
square pores, etc.)
Tissue response of different mesh designs
has yet to be investigated
307
25. Synthetic Prosthetic Choices in Ventral Hernia Repair
the mesh can change shape dramatically depending upon the weave,
which can lead to enhanced in fl ammatory and foreign body response.
Modeling of weave designs in conjunction with the biomechanics of the
abdominal wall could possibility lead to better mesh designs and thus
better clinical outcomes. Table 25.2 summarizes some of the engineered
mesh materials factors that may in fl uence tissue response.
Future of Hernia Mesh Materials
For all intents and purposes, the goal of hernia mesh is to bridge the
hernia defect while providing the mechanical strength and fi xation which
is important for repair. An ideal mesh would match the mesh material
properties to that of the tissue while eliciting favorable tissue responses
and avoiding any material changes/degradation (shrinkage, oxidation,
etc.). Unfortunately, such a mesh does not currently exist. Added to the
challenge of designing an optimal mesh is patient response to mesh
materials may be different. Implementing continuous quality improvement
projects would help in deciphering the optimal mesh design parameters
as well as targeting particular patient populations. Until an optimal mesh
can be designed, surgeons will have to rely on their own clinical
experiences in choosing the best mesh for their patients.
References
1. Brueing NK, Butler CE, Ferzoco S, Franz M, Hultman CS, Kilbridge JF, Rosen M,
Silverman RP, Vargo D. Incisional ventral hernias: review of the literature and
recommendations regarding the grading and technique of repair. Surgery. 2010;148(3):
544–58.
2. Bendavid R. Recurrences: the fault of the surgeon. In: Schumpelick V, Nyhus LM,
editors. Meshes: bene fi ts and risks. New York: Springer; 2004. p. 55.
3. Arroyo A, Garcia P, Perez F, Andreu J, Candela F, Calpena R. Randomized clinical
trial comparing suture and mesh repair of umbilical hernia in adults. Br J Surg. 2001;
88:1321–3.
4. Anthony T, Bergen PC, Kim LT, et al. Factors affecting recurrence following incisional
herniorrhaphy. World J Surg. 2000;24:95–100.
5. Tentes A, Xanthoulis AI, Mirelis CG, et al. Nuttall technique: a method for subumbilical
incisional hernia repair revised. Langenbecks Arch Surg. 2008;393:191–4.
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6. Hadad I, Small W, Dumanian GA. Repair of massive ventral hernias with the separation
of parts technique: reversal of the lost domain. Am Surg. 2009;75:301–6.
7. Milikan KW. Incisional hernia repair. Surg Clin North Am. 2003;83:1223–34.
8. Shankaran V, Weber DJ, Reed RL, Luchette FA. A review of available prosthetics for
ventral hernia repair. Ann Surg. 2011;253(1):16–26.
9. Alkhoury F, Helton S, Ippolito RJ. Cost and clinical outcomes of laparoscopic ventral
hernia repair using intraperitoneal nonheavyweight polypropylene mesh. Surg
Laparosc Endosc Percutan Tech. 2011;21(2):82–5.
10. Sailes FC, Walls J, Guelig D, Mirzabeigi M, Long WD, Crawford A, Moore JH, Copit
SE, Tuma GA, Fox J. Synthetic and biological mesh in component separations: a
10-year single institution review. Ann Plast Surg. 2010;64(5):696–8.
11. Van’t RM, Vrijland WW, Lange JF, Hop WC, Jeekel J, Bonjer HJ. Mesh repair of
incisional hernia: comparison of laparoscopic and open repair. Eur J Surg. 2002;
168(12):684–9.
12. Yavuz N, Ipek T, As A, Kapan M, Eyuboglu E, Erguney S. Laparoscopic repair of
ventral and incisional hernias: our experience in 150 patients. J Laparoendosc Adv
Surg Tech A. 2005;6:601–5.
13. Burger JWA, Luijendijk RW, Hop WCJ, Halm JA, Verdaasdonk EGG, Jeekel J. Long-
term follow-up of a randomized control trial of suture versus mesh repair of incisional
hernia. Ann Surg. 2004;240(4):578–85.
14. Luijendijk RW, Hop WC, van den Tol MP, de Lange DC, Braaksma MM, Ijzermans
JN. A comparison of suture repair with mesh repair for incisional hernia. N Engl J
Med. 2000;343:392–8.
15. Flum DR, Horvath K, Koepsell T. Have outcomes of incisional hernia repair improved
with time? A population-based analysis. Ann Surg. 2003;237:129–35.
16. Cozad M, Ramshaw BR, Grant DN, Bachman SL, Grant DA, Grant SA. Materials
characterization of explanted polypropylene, polyethylene terephthalate, and expanded
polytetra fl uoroethylene composites: spectral and thermal analysis. J Biomed Mater
Res B Appl Biomater. 2010;94:455–62.
17. Costello CR, Bachman SL, Ramshaw BR, Grant SA. Materials characterization of
explanted heavyweight polypropylene hernia meshes. J Biomed Mater Res B Appl
Biomater. 2007;83B:44–9.
18. Klinge U, Klosterhalfen B, Muller M, Ottinger AP, Schumpelick V. Shrinking of
polypropylene mesh in vivo: an experimental study in dogs. Eur J Surg. 1998;164:
965–9.
19. Gonzalez R, et al. Relationship between tissue ingrowth and mesh contraction. World
J Surg. 2005;29(8):1038–43.
20. Pierce RA, Perrone JM, Nimeri A, Sexton JA, Walcutt J, Frisella MM, Matthews BD.
120-day comparative analysis of adhesion grade and quantity, mesh contraction, and
tissue response to a novel omega-3 fatty acid bioabsorbable barrier macroporous mesh
after intraperitoneal placement. Surg Innov. 2009;16:46–54.
21. Schmidbauer S, Ladurner R, Hallfeldt KK, Mussack T. Heavy-weight versus low-
weight polypropylene meshes for open sublay mesh repair of incisional hernia. Eur J
Med Res. 2005;10(6):247–53.
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25. Synthetic Prosthetic Choices in Ventral Hernia Repair
22. Brown CN, Finch JG. Which mesh for hernia repair? Ann R Coll Surg Engl.
2010;92:272–8.
23. Weyhe D, Schmitz I, Belyaev O, Grabs R, Müller K-M, Uhl W, Zumtobel V.
Experimental comparison of mono fi le light and heavy polypropylene meshes: less
weight does not mean less biological response. World J Surg. 2006;30(8):1586–91.
24. Gemma Pascual G, Rodrıguez M, Gomez-Giln V, Garcıa-Honduvilla N, Bujan J, Bello
JM. Early tissue incorporation and collagen deposition in lightweight polypropylene
meshes: bioassay in an experimental model of ventral hernia. Surgery. 2008;144(3):
427–35.
25. Burger JWA, Halm JA, Wijsmuller AR, Raa J, Jeekal ST. Evaluation of new prosthetic
meshes for ventral hernia repair. Surg Endosc. 2006;20(8):1320–5.
26. Scheidback H, Tamme C, Tannapfel A, Lippert H, Kockerling F. In vivo studies
comparing the biocompatibility of various polypropylene meshes and their handling
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study in pigs. Surg Endosc. 2004;18(2):211–20.
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Degradation of mesh coatings and intraperitoneal adhesion formation in an experimental
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28. Eriksen JR, Gogenur I, Rosenberg J. Choice of mesh for laparoscopic ventral hernia
repair. Hernia. 2007;11:481–92.
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311
B.P. Jacob and B. Ramshaw (eds.), The SAGES Manual of Hernia Repair,
DOI 10.1007/978-1-4614-4824-2_26,
© Springer Science+Business Media New York 2013
26. Biologic Prosthetics: What Are
They and How Do They Interact
with the Body?
Gina L. Adrales and Elizabeth Honigsberg
Biologic mesh was developed to address the shortcomings of
permanent synthetic mesh, such as chronic in fl ammation and foreign
body reaction, stiffness, and mesh infection. Since the introduction of
biologic prosthetics, the market has been rife with new biologic materials
attached to largely unsupported claims of superiority and safety.
Although the status of literature on biologic mesh is improving, the
current data are comprised mainly from animal studies and level III
evidence. Over the last decade, surgeons have utilized biologic mesh in
a variety of cases including primary and recurrent hernia repair, hernia
prophylaxis, and the most widely used application, hernia repair in the
contaminated fi eld. The following chapter reviews the origin, structure,
and mechanics of biologic mesh and concludes with the current
indications and shortcomings of biologic prosthetics.
Biologic Prosthetics
Material Source
First introduced in 1999, biologic prosthetics have been implemented
broadly by the surgical community, particularly for complex abdominal
wall hernia repair. Bioprosthetics are designed to be acellular, absorbable,
three-dimensional extracellular matrices of largely type I collagen,
elastin, proteoglycans, and growth factors [ 1 ] . Biologic meshes are
312
G.L. Adrales and E. Honigsberg
derived from a variety of collagen-rich sources that differ by donor
(human, porcine, bovine) and by site (dermis, intestinal submucosa, and
pericardium). Biologic meshes are characterized broadly as allografts
(human cadaver source) or heterografts/xenografts (bovine and porcine
sources). Xenografts are regulated by the Food and Drug Administration
(FDA), whereas allografts are largely regulated by tissue banks [
2 ] .
Thirteen FDA-approved products currently are available for use and are
classi fi ed according to source material and processing (Table 26.1 ).
Material Processing
Although the basic construct of biologic mesh as a collagen scaffold
is shared by various brands of biologic mesh, the processing of the mesh
varies widely. Generally, allografts are minimally processed whereas
xenografts require additional processing to inhibit immunogenicity [ 3 ] .
Mesh manufacturing is a largely proprietary process, and as such, speci fi c
details regarding methods for decellularization, cross-linking, and
sterilization are often unclear (except what is contained in published
patents). Additionally, the sources of human dermis, in terms of donor
age and body part, are uncertain. However, each company may have
different criteria for acceptable tissue.
The tissues are procured and treated to remove cellular elements,
leaving the biologic mesh collagen scaffold. The cells are removed from
the grafts by various methods: physical means such as desiccation,
chemical processes, or enzymatic reactions. Some of the products are
terminally sterilized while others are not, resulting in variations in storage
and pre-use hydration requirements. Sterilization options include gamma
radiation, ethylene oxide, or hydrogen peroxide.
Natural cross-links of hydrogen bonds stabilize the triple helix
collagen structure present in bioprosthetics against enzymatic degradation
by collagenase. These natural cross-links weaken with time, permitting
binding of the collagenase at the receptor level and breakdown of the
collagen. This allows for remodeling and repair of the tissue. Ideally,
the collagen scaffold of the biomaterial should not degrade fully before
the host can adequately remodel the site with ingrowth of host cells.
To address the major shortcoming of biologic mesh, namely, premature
degradation and subsequent weakness and laxity, some manufacturers
elect to intentionally crosslink the mesh through chemical processing to
prevent collagenase binding at the enzyme receptor. This results in
supraphysiologic levels of covalent collagen cross-linked bonds with the
313
26. Biologic Prosthetics: What Are They and How Do They
Table 26.1. Commercially available biologic grafts.
Trade name Manufacturer Source Processing Terminal sterilization Cross-linked Handling
Allografts
AlloDerm LifeCell (Branchburg,
NJ)
Human dermis Freeze-dried, NaCl,
sodium
deoxycholate
None No 2-year shelf life
requires
refrigeration,
20–30-min
rehydration
AlloMax Davol, C.R. Bard
(Cranston, RI)
Human dermis Acetone, hyper-/
hypotonic baths,
H
2
O
2
, NaOH
Gamma radiation No
FlexHD Musculoskeletal
Tissue Foundation
(Edison, NJ,
Ethicon
(Somerville, NJ))
Human dermis Hypertonic bath Detergents,
disinfectant,
ETOH
No No need for
rehydration
Heterografts
Surgisis Cook medical
(Bloomington, IN)
Porcine
intestine
submucosa
Peracetic acid Ethylene oxide No No need for
rehydration
Strattice LifeCell (Branchburg,
NJ)
Porcine dermis E beam radiation No 2-min rehydration
FortaGen Organogenesis, Inc,
(Canton, MA)
Porcine
intestine
submucosa
Yes No need for
rehydration
(continued)