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Baumann & Butler
Vein grafts and arterialized vein loops provide recipient vessels in the central abdominal wall. Vein grafts can be harvested from either the upper or lower extremity as a cephalic vein graft or saphenous vein graft. For central and lower abdominal defects an
arterialized saphenous vein loop can be designed. The saphenous vein is dissected
and transected distally and then anastomosed to the superficial femoral artery or a
side branch. This technique allows delivery of the loop to the flap’s recipient site where
the loop is divided providing an arterialized afferent limb and a venous drainage efferent
limb. This technique only requires 3 anastomoses instead of 4, as is the case with direct
arterial and venous vein grafts. The main recipient vessel sites for vein grafts or arterialized vein loops are the thoracodorsal vessels; internal mammary vessels; branches of
the superficial femoral system and the deep inferior epigastric vessels can be used to
extend the reach of vein grafts to the central abdominal wall.
ABDOMINAL WALL TRANSPLANTATION
Abdominal wall transplantation represents the zenith of abdominal wall flap reconstruction. It is generally reserved for patients undergoing single-organ or multiorgan
visceral transplants in which abdominal wall closure by autologous flaps is not technically feasible or presents significant donor morbidity. Abdominal wall closure after
visceral organ transplantation is challenging in the setting of donor/recipient organ
size mismatch and/or prior recipient abdominal surgery. Transplant patients can
benefit from vascularized composite allotransplants as an additional strategy to
expand the domain of the abdominal cavity to allow for either a graft/recipient size
mismatch or inability for closure in the event of extreme intestinal edema. Although
the risks of lifelong immunosuppression potentially outweigh the benefits of abdominal
wall transplantation in healthy nontransplant patients, transplant patients are already
bound to an immunosuppressive regimen and can benefit from the addition of allograft
abdominal wall musculofascial tissue to reduce abdominal wall wound complication at
the time of transplantation.
In the setting of transplant immunosuppression, the risk of an open abdominal
wound, fascial dehiscence, septic evisceration, or fistula carries significant morbidity
and potential mortality. When conventional abdominal wall closure techniques are
insufficient, allotransplantation is performed. Extensive study of the vascular supply
of the abdominal wall has allowed design of musculofasciocutaneous flaps based
on the deep inferior epigastric (DIEP) system. These flaps can be transferred based
on either the DIEP vessels through microsurgical techniques or the external iliac for
a macrovascular anastomosis. Selvaggi and colleagues
6
describe a series of 15
abdominal wall transplants with 3 episodes of rejection salvage with modulating
immunosuppression and 2 flap losses caused by vascular thrombosis.
Pediatric transplant patients present challenges in managing graft/recipient size
mismatches and have the potential for needing advanced reconstructive options for
abdominal wall closure. Given the microsurgical challenges associated with pediatric
vessel caliber, alternative strategies for abdominal wall transplantation have been
developed. Agarwal and colleagues
transplant patients.
8,9
They design a posterior rectus sheath fascioperitoneal flap
7
described a novel flap design for pediatric liver
based on the terminal branches of the hepatic artery via the falciform ligament, which
enables transfer of the vascularized posterior sheath in continuity with the liver by
means of the falciform ligament without the requirement for additional vascular
anastomoses.
Abdominal wall transplantation is in its earliest stages. It has virtually eliminated
the issue of donor site morbidity and future advances will likely focus on improved
Soft Tissue Coverage
recipient site function. To this end, refining flap design even further to include dynamic
neurotized flap transfers that can provide stable abdominal wall contour and preserved truncal core muscular stability will represent a new era in abdominal wall
reconstruction.
REFERENCES
1. Smith PJ. The vascular basis of axial pattern flaps. Br J Plast Surg 1973;26(2):
150–7.
2. Khouri JS, Egeland BM, Daily SD, et al. The keystone island flap: use in large de-
fects of the trunk and extremities in soft-tissue reconstruction. Plast Reconstr
Surg 2011;127(3):1212–21.
3. Bui DT, Cordeiro PG, Hu QY, et al. Free flap reexploration: indications, treatment,
and outcomes in 1193 free flaps. Plast Reconstr Surg 2007;119(7):2092–100.
4. Chalfoun CT, McConnell MP, Wirth GA, et al. Free tensor fasciae latae flap for
abdominal wall reconstruction: overview and new innovation. J Reconstr Microsurg 2012;28(3):211–9.
5. Lin SJ, Butler CE. Subtotal thigh flap and bioprosthetic mesh reconstruction for
large, composite abdominal wall defects. Plast Reconstr Surg 2010;125(4):
1146–56.
6. Selvaggi G, Levi DM, Cipriani R, et al. Abdominal wall transplantation: surgical
and immunologic aspects. Transplant Proc 2009;41(2):521–2.
7. Agarwal S, Dorafshar AH, Harland RC, et al. Liver and vascularized posterior
rectus sheath fascia composite tissue allotransplantation. Am J Transplant
2010;10(12):2712–6.
8. Lee JC, Olaitan OK, Lopez-Soler R, et al. Expanding the envelope: the posterior
rectus sheath-liver vascular composite allotransplant. Plast Reconstr Surg 2013;
131(2):209e–18e.
9. Ravindra KV, Martin AE, Vikraman DS, et al. Use of vascularized posterior rectus
sheath allograft in pediatric multivisceral transplantation–report of two cases. Am
J Transplant 2012;12(8):2242–6.
1209
Biology of Biological Meshes Used in Hernia Repair
Yuri W. Novitsky, MD
KEYWORDS
Biological meshHerniaSurgeryAbdominal wallGrafts
KEY POINTS
Ideally, use of biological grafts would be more advantageous in infected and contami-
nated fields, to incorporate and integrate into the ventral abdominal wall and ultimately
to prevent recurrence. Although the use of biological meshes clearly has importance in
ventral abdominal wall surgery, significant doubts about their indications and the implications of their use have arisen.
Recent data have been disappointing on several fronts. Animal investigations have failed
to demonstrate consistent evidence of biological mesh remodeling and replacement of
biological grafts with collagen-like tissue. In addition, recent human experience has revealed that true remodeling of biologics occurs at the periphery of an implanted graft, if
at all.
Combining this evidence with disappointing clinical outcomes of biologics, particularly in
the long term, has significantly cooled off enthusiasm about biological grafts. While investigations of biological grafts are still ongoing, the traditionally proposed notion of graft remodeling as an underlying principle of biological grafts is likely not representative of
reality.
It appears that the current design of biological constructs will have to undergo significant
modifications to remain a part of the surgeon’s armamentarium in the future.
INTRODUCTION
Throughout the United States and most of the world, hernia repair continues to be the
most common surgical procedure performed by general surgeons.
1–3
Successful
repair of most hernias requires the use of a prosthetic implant for reinforcement of
the defect. Synthetic surgical meshes have been used for more than 50 years and
are the most prevalent category of meshes used today. However, synthetic materials
have been associated with a variety of complications related to foreign-body implantation. Some of the more serious adverse effects of synthetics include sensation of
Disclosures: Consultant/speaker bureau for Lifecell, CR Bard.
Department of Surgery, Case Comprehensive Hernia Center, University Hospitals Case Medical
Center, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106, USA
E-mail address: yuri.novitsky@uhhospitals.org
Surg Clin N Am 93 (2013) 1211–1215
http://dx.doi.org/10.1016/j.suc.2013.06.014 surgical.theclinics.com
0039-6109/13/$ – see front matter Ó 2013 Elsevier Inc. All rights reserved.
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Novitsky
the implant, limitation of movement, chronic pain, and, most concerning, prosthetic
infection. In addition, synthetic meshes have traditionally been thought to be contraindicated in infected or potentially contaminated fields.
4–8
Because of the need for
prosthetic implants to resist infections and to support repairs in contaminated or
potentially contaminated fields, biological meshes have been developed to take the
place of nondegradable synthetic meshes. Clearly a biological matrix that would resist
infection, while providing a durable reinforcement of a hernia repair, would be ideal for
most, if not all, repairs. This article reviews the validity of assumptions that support the
purported notion of the biological behavior of biological meshes.
BASIC CONCEPTS
One of the key factors in determining the success of the graft is its biocompatibility and
the degree of evoked host tissue response. Implanted graft can become either incorporated, resulting in neovascularization and deposition of collagen (remodeling)
throughout the material; encapsulated, with deposition of fibrotic material at the
periphery and around the graft; or resorbed/degraded, without any visible residual
evidence of the mesh.
The purported function of biologics is to serve as a regenerative framework that sup-
ports matrix remodeling and deposition of new collagen.
1–5
Factors that affect how a
given mesh is reacted upon by the recipient include tissue sourcing, different methods
of processing, decellularization, and sterilization used. Manufacturers use various proprietary methods and processing solvents that likely influence the innate biochemical
and biomolecular structure of the collagen scaffold. Subsequently, these matrix alterations likely influence foreign-body recognition and antigen presentation. The resultant
processing likely changes a variety of factors that are essential for matrix survival:
immunogenic potential, biocompatibility, and foreign-body response to each implant.
COLLAGEN CROSS-LINKING
Of all the various processing techniques used by the manufacturers, collagen crosslinking appears to have the most profound impact on tissue responses to biological
meshes. By using hexamethylenediisocyanate, carbodiimide, glutaraldehyde, or
photo-oxidizing agents,
9,10
intentional cross-linking is used to prolong the life span
of the mesh, using processing techniques that add to the 3-dimensional structure of
the collagen to, essentially, mechanically strengthen the matrix and impede degradation by collagenase. To help put this process in proper perspective, it is important to
point out that “terminally” cross-linked animal dermis is leather. Even nonintentionally
cross-linked products may undergo molecular structural changes, such as collagen
cross-linking, from g-irradiation during the sterilization process.
11
In addition, incomplete removal of chemical cross-linking agents could result in cytotoxicity from residues leaching from the mesh itself, which may induce prolonged toxic effects and
heightened cellular responses.
9,10
Although clinical circumstances requiring longterm tissue reinforcement may provide some utility for a cross-linked graft, it is clear
that such meshes display a significant immunologic disadvantage that likely translates
into poor performance in a clinical setting, especially in the face of contamination.
MESH INTEGRATION AND HOST REACTIONS
12–15
On implantation, rapid mesh integration remains an important and clearly desirable
outcome. Unfortunately, this process is poorly understood and is often difficult to
qualify and quantify. It appears that there is a cascade of events that follow initial
Biology of Biologics
mesh-host interaction. The author believes that acute inflammatory response takes
place after mesh placement in the host. This event is a necessary one in wound healing
and, obviously, is highly influential in the performance of biological mesh. The process
of ingrowth begins with mononuclear cell (macrophages and mast cell) penetration
into a mesh scaffold. Although meshes with diminished biocompatibility do not allow
for such neocellularity, grafts that are positively recognized by a host will have host
cells easily migrate from the periphery of the mesh inward. This step is often simultaneous with new proliferation of blood vessels within the graft. Once mononuclear cells
populate the graft, the typical sequence of wound-healing events likely takes place.
Mononuclear cells secrete cytokines and other signaling factors to attract fibroblasts.
Once fibroblasts arrive, new collagen synthesis and deposition take place. Of importance, this process has to occur not only at the mesh/host interface but also within the
graft itself; this would predispose a biological graft for ingrowth, incorporation, and
deposition of new collagen within the mesh. Although this sequence is appealing,
the author has not been unable to elucidate such a process in several animal models.
Moreover, recent experience with mesh explants from humans has supported the
notion that “remodeling” is not a typical event.
Inflammation appears to be a common component of host response to implanted
biological prosthetics.
6,15–17
This reaction either may aid in the integration of the
mesh via normal wound-healing mechanisms, or can induce a disproportionate inflammatory response. Such exaggerated reaction will likely result in excessive scarring,
graft encapsulation, and/or degradation.
6,15,18
The balance between appropriate
wound healing and detrimental sequelae is largely controlled by cytokines, growth factors, and other chemical signaling moleculesproduced by host macrophages at the site
of the host/mesh interface. Orenstein and colleagues
15,19
were the first to evaluate the
immunogenic potential of various human-derived and porcine-derived biological
meshes in vitro. With regard to porcine meshes, non–cross-linked porcine dermis
mesh and, to a lesser degree, porcine intestinal submucosa-derived mesh were associated with a markedly diminished cytokine production in comparison with the crosslinked porcine dermis materials. Although the exact clinical importance of the excessive
macrophage activation in vitro is unclear, this early evidence of adverse effects of
chemical cross-linking has subsequently been collaborated by several in vivo
studies.
6,13,18,20
Most recently, Petter-Puchner and colleagues12reported a pronounced foreign-body response to intraperitoneal implantation of Collamend and Surgisis in rats. Both meshes were noted to be surrounded by a broad rim of foreign-body
giant cells and granulomas. Consequently, the “biological” behavior of such grafts is
somewhat limited.
1213
BIOLOGICAL MESH REMODELING
The final and most important step in biological mesh placement is graft integration and
remodeling with deposition of new collagen and regeneration of tissue. During this
process, the implanted mesh is often resorbed by the host. Melman and colleagues
have suggested that when scaffold degradation is accompanied by cellular infiltration,
extracellular matrix (ECM) deposition, and neovascularization, it can be viewed as
remodeling. At times, however, when ECM deposition/neovascularization does not
occur, mesh is likely replaced by a scar with a resultant detriment to a hernia repair.
One of the other key factors that influence remodeling may be the rate of scaffold
degradation.
21
Almost uniform failure of absorbable meshes may be due to a fairly
rapid degradation of the graft without proper support for new ECM-component deposition. In fact, a gradual remodeling of an implanted tissue graft seems to be essential
21
1214
Novitsky
for abdominal wall repair because degradation or absorption of a scaffold not
balanced with deposition of new collagen would predispose to mesh failure.
and colleagues
16
reported that non–cross-linked grafts showed more favorable
17
Deeken
remodeling characteristics. However, remodeling in their study was not associated
with stronger reinforcement of native tissue repairs in the long term. As mentioned
earlier, these paradoxic results may be a consequence of the animal model used.
Another recent study revealed essential lack of matrix absorption and absence of
remodeling of cross-linked graft after 6 months’ implantation.
18
Of interest, most of
the Collamend matrix samples were completely degraded by bacteria from associated
wounds. The mesh samples that did not get infected were found to have no evidence
of remodeling and poor or no integration.
18
While such mesh performance may at
times result in an effective repair in the clean setting, this behavior of Collamend
can hardly be viewed as “biological” reinforcement. Instead, given its lack of integration into the host and likely resultant fibrous encapsulation, cross-linked grafts often
act as permanent foreign-body materials, similar to GoreTex–based synthetics. In
fact, the author found in his mouse model that cross-linked grafts had no evidence
of remodeling but a thick layer of fibrous encapsulation 3 months after implantation.
It appears that the balance between ECM deposition and mesh degradation is critical
for mesh remodeling and effective tissue reinforcement. Finally, although many investigators reported deposition of “new” matrix at the site of biological mesh implantations, a typical scar plate developed as a part of normal wound healing which likely
to mimicked regeneration. Truly distinguishing regenerated collagen within degraded
scaffold from fibrotic scar formation has contrived to be a tough challenge.
SUMMARY
Ideally, the use of biological grafts would be more advantageous in infected and
contaminated fields, to incorporate and integrate into the ventral abdominal wall
and ultimately to prevent recurrence. While biological meshes clearly have importance
in ventral abdominal wall surgery, significant doubts about their indications and the implications of their use have arisen. Recent data have been disappointing on several
fronts. Animal investigations have failed to demonstrate consistent evidence of biological mesh remodeling and replacement of biological grafts with collagen-like tissue. In
addition, recent human experience has revealed that true remodeling of biologics occurs at the periphery of an implanted graft, if at all. Combining this evidence with
disappointing clinical outcomes of biologics,
22
particularly in the long term, has significantly cooled off enthusiasm about biological grafts. While investigations of biological
grafts are still ongoing, the traditionally proposed notion of graft remodeling as an underlying principle of biological grafts is likely not representative of reality. It appears
that the current design of biological constructs will have to undergo significant modifications to remain a part of the surgeon’s armamentarium in the future.
REFERENCES
1. Gaertner WB, Bonsack ME, Delaney JP. Experimental evaluation of four biologic
prostheses for ventral hernia repair. J Gastrointest Surg 2007;11:1275–85.
2. Cornwell KG, Landsman A, James KS. Extracellular matrix biomaterials for soft
tissue repair. Clin Podiatr Med Surg 2009;26:507–23.
3. Rosen MJ. Biologic mesh for abdominal wall reconstruction: a critical appraisal.
Am Surg 2010;76:1–6.
4. Jansen PL, Mertens Pr P, Klinge U, et al. The biology of hernia formation. Surgery
2004;136:1–4.
Biology of Biologics
5. Jin J, Rosen MJ, Blatnik J, et al. Use of acellular dermal matrix for complicated
ventral hernia repair: does technique affect outcomes? J Am Coll Surg 2007;
205:654–60.
6. Sandor M, Xu H, Connor J, et al. Host response to implanted porcine-derived
biologic materials in a primate model of abdominal wall repair. Tissue Eng Part
A 2008;14:2021–31.
7. Marreco PR, da Luz Moreira P, Genari SC, et al. Effects of different sterilization
methods on the morphology, mechanical properties, and cytotoxicity of chitosan
membranes used as wound dressings. J Biomed Mater Res B Appl Biomater
2004;71:268–77.
8. Rueter A, Schleicher JB. Elimination of toxicity from polyvinyl trays after steriliza-
tion with ethylene oxide. Appl Microbiol 1969;18:1057–9.
9. Khor E. Methods for the treatment of collagenous tissues for bioprostheses.
Biomaterials 1997;18:95–105.
10. Schmidt CE, Baier JM. Acellular vascular tissues: natural biomaterials for tissue
repair and tissue engineering. Biomaterials 2000;21:2215–31.
11. Gouk SS, Lim TM, Teoh SH, et al. Alterations of human acellular tissue matrix by
gamma irradiation: histology, biomechanical property, stability, in vitro cell repopulation, and remodeling. J Biomed Mater Res B Appl Biomater 2008;84:205–17.
12. Petter-Puchner AH, Fortelny RH, Silic K, et al. Biologic hernia implants in exper-
imental intraperitoneal onlay mesh plasty repair: the impact of proprietary
collagen processing methods and fibrin sealant application on tissue integration.
Surg Endosc 2011;25:3245–52.
13. Butler CE, Burns NK, Campbell KT, et al. Comparison of cross-linked and non-
cross-linked porcine acellular dermal matrices for ventral hernia repair. J Am
Coll Surg 2010;211:368–76.
14. Pierce LM, Rao A, Baumann SS, et al. Long-term histologic response to synthetic
and biologic graft materials implanted in the vagina and abdomen of a rabbit
model. Am J Obstet Gynecol 2009;200:546.e1–8.
15. Orenstein SB, Qiao Y, Klueh U, et al. Activation of human mononuclear cells by
porcine biologic meshes in vitro. Hernia 2010;14:401–7.
16. Deeken CR, Melman L, Jenkins ED, et al. Histologic and biomechanical evalua-
tion of crosslinked and non-crosslinked biologic meshes in a porcine model of
ventral incisional hernia repair. J Am Coll Surg 2011;212:880–8.
17. Xu H, Wan H, Sandor M, et al. Host response to human acellular dermal matrix
transplantation in a primate model of abdominal wall repair. Tissue Eng Part A
2008;14:2009–19.
18. de Castro Bras LE, Shurey S, Sibbons PD. Evaluation of crosslinked and non-
crosslinked biologic prostheses for abdominal hernia repair. Hernia 2012;16:
77–89.
19. Orenstein SB, Qiao Y, Kaur M, et al. Human monocyte activation by biologic and
biodegradable meshes in vitro. Surg Endosc 2010;24:805–11.
20. Burns NK, Jaffari MV, Rios CN, et al. Non-cross-linked porcine acellular dermal
matrices for abdominal wall reconstruction. Plast Reconstr Surg 2010;125:
167–76.
21. Melman L, Jenkins ED, Hamilton NA, et al. Early biocompatibility of crosslinked
and non-crosslinked biologic meshes in a porcine model of ventral hernia repair.
Hernia 2011;15:157–64.
22. Rosen MJ, Krpata DM, Ermlich B, et al. A 5-Year clinical experience with single-
staged repairs of infected and contaminated abdominal wall defects utilizing biologic mesh. Ann Surg 2013;257(6):991–6.
1215
Clinical Outcomes of Biologic
Mesh:
Where Do We Stand?
Hobart W. Harris, MD, MPH
KEYWORDS
AllograftXenograftProstheticsEfficacy
KEY POINTS
The cumulative data regarding biologic mesh use on ventral hernias under contaminated
conditions do not support the claim that they are better than synthetic mesh used under
the same conditions.
Most of the available data pertain to the use of human acellular dermal matrix to repair
complex ventral hernias, a product that both experts in the field and manufacturers
now agree is inadequate for this clinical application.
The highly promoted and frequently discussed practice of placing biologic mesh in
contaminated surgical fields is being done outside of the products’ original intended
use and, in some instances, equates to off-label use of a medical device.
Biologic mesh use, even in noncontaminated conditions, is questionable when the
reported results are viewed in light of the high costs.
INTRODUCTION
Ventral hernias occur after 11% to 23% of laparotomy incisions. With 4 to 5 million laparotomies performed annually in the United States, there are an estimated 400,000
ventral hernia repairs each year, making it one of the most common procedures performed by general surgeons and adding more than $8 billion to US health care costs. A
permanent prosthetic mesh repair during a clean case in which there is no bacterial
contamination is the standard of care, yielding the best long-term results and reducing
the hernia recurrence rate by 50%.
1
The management of ventral hernias in the setting
of bacterial contamination remains, however, a major clinical challenge because
placing a permanent synthetic prosthetic into a contaminated field is generally thought
to result in an unacceptably high rate of complications, including surgical site infection, enterocutaneous fistula, and recurrent hernia formation. Therefore, until recently,
the standard of care for repairing a complex ventral hernia (eg, one that involves a
compromised surgical field in which gastrointestinal, biliary, and/or genitourinary procedures are performed or frank infection is present) was a 2-stage procedure. In the
Disclosures: The author has nothing to disclose.
Department of Surgery, UCSF, 513 Parnassus Avenue, Room S-301, Box 0104, San Francisco, CA
94143-0104, USA
E-mail address: Hobart.Harris@ucsfmedctr.org
Surg Clin N Am 93 (2013) 1217–1225
http://dx.doi.org/10.1016/j.suc.2013.06.001 surgical.theclinics.com
0039-6109/13/$ – see front matter Ó 2013 Elsevier Inc. All rights reserved.
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Harris
first stage, the contaminated portion of the surgery is completed and the abdominal
wall reconstructed using a temporary synthetic (absorbable) prosthetic. In the second
stage, after approximately 6 to 12 months have elapsed and the wound contamination
has been eliminated, the persistent ventral hernia is repaired using a permanent synthetic prosthetic. Although the 2-stage procedure is thought to reduce the risks of
infection-related complications by avoiding placement of permanent prosthetic material into a contaminated wound, it unfortunately requires patients to undergo 2 separate operations, hospitalizations, and recovery periods, during which time they often
cannot work and must endure a limited level of physical activity.
Several biomedical companies have recently introduced new biologic prosthetics
(mesh) to address the clinical challenge of treating complex ventral hernias with a
1-stage repair. Because biologic mesh is derived from living tissue, these products
are promoted as resisting infection and enabling wound healing in contaminated
surgical fields. Currently, an intriguing variety of biologic meshes, derived from
collagen-rich porcine, bovine, or human tissues, such as skin, intestinal submucosa,
or pericardium, is available for the 1-stage repair of complex ventral hernias. These
products are, however, expensive, and long-term outcome data are sparse. Furthermore, data are accumulating that question the overall clinical efficacy of such products, despite their intuitive appeal as more natural tissue replacements.
This article reviews currently available clinical data regarding the use of biologic
mesh for the 1-stage repair of incisional hernias in the setting of wound contamination.
Specifically, it attempts to answer the general question, “Should biologic mesh be
used for incisional hernia repair?”
TYPES OF BIOLOGIC MESH
Biologic meshes derived from collagen-rich tissues of human (allograft) or animal
(xenograft) origin were introduced into clinical practice in the 1990s.
2
Whereas synthetic prosthetics have been successfully used to reinforce the abdominal wall for
more than a century, biologic meshes represent the newest effort to find the ideal material for hernia repair. In theory, biologic mesh provides a 3-D scaffold of extracellular
matrix proteins that enables native cells to infiltrate and promotes neovascularization
and the regeneration of healthy connective tissue that is resistant to infection. The biologic nature of the material is thought to provide an improved ability to reintegrate with
surrounding tissues while reducing the risk of infection, erosion, extrusion, and rejection compared with the synthetic alternatives. Biologic meshes purportedly avoid
some of the complications observed with the use of synthetic mesh, but, most importantly, biologic meshes can be deployed in the setting of wound contamination, a condition for which the use of synthetic mesh is generally discouraged.
More than a dozen different biologic meshes are currently available for abdominal
wall reconstruction (Table 1). These products differ in their biologic source, processing to remove cellular components and reduce antigenicity, decontamination, size and
thickness, amount of cross-linking, storage and handling characteristics, and costs.
Although a detailed evaluation of these various differences is beyond the scope of
this article, a brief discussion of cross-linking is warranted because it is frequently
cited as a feature that has a critical impact on a prosthetic’s clinical performance.
Cross-links are covalent or ionic bonds that link one polymer chain to another, with
a resultant increase in strength of the overall material. Cross-linking in the context
of biologic mesh refers to bonds between extracellular matrix proteins, most
commonly collagen fibers. Some degree of collagen cross-linking occurs naturally;
yet, creating additional cross-links yields increased resistance to degradation by
Clinical Outcomes of Biologic Mesh
Table 1
Summary of the commercially available biologic meshes
Biologic Source Manufacturer Notes
Human acellular dermis
AlloDerm LifeCell Proprietary sterilization process
AlloMax Davol/Bard Sterilized via g-irradiation
FlexHD Ethicon Hydrated dermis packaged in ethanol solution
Porcine acellular dermis
CollaMend Bard Cross-linked collagen and elastin
Permacol Covidien Chemically cross-linked lysine/hydroxylysine residues
Strattice LifeCell Non–cross-linked, prehydrated matrix
XenMatrix Davol/Bard Proprietary dermal processing without cross-linking
Porcine intestinal submucosa
FortaGen Organogenesis Low level of cross-linking
Surgisis Cook Multiple versions marketed since 2004
Bovine acellular dermis (fetal)
SurgiMend TEI Biosciences Type III collagen-rich dermis in 1–4 mm thicknesses
Bovine pericardium
Peri-Guard Synovis Gluteraldehyde cross-linking, NaOH sterilization
Tutopatch Tutogen Proprietary chemical and mechanical sterilization
Veritas Synovis Propylene oxide capped amine technology
1219
either host or bacterial enzymes, thereby increasing mesh durability and reportedly
decreasing hernia recurrence rates. Animal data indicate that although increased
cross-linking is associated with a decreased rate of tissue degradation, it is also associated with decreased tissue integration.
3
Optimal tissue integration and mesh
strength/durability define 2 ends of a spectrum. As the amount of cross-linking in a
biologic mesh increases, so does the material’s durability, but with the trade-off of
decreased tissue integration. There is insufficient information to conclusively determine the effect of cross-linking on hernia recurrence rates, thereby rendering the
clinical importance of this specific mesh characteristic unclear.
CLINICAL OUTCOMES
The overall clinical efficacy of biologic prosthetics for the repair of incisional hernias is
unclear, despite their aggressive marketing, clinical popularity, and intuitive scientific
appeal. A review of how these products reach the marketplace and the available
clinical outcomes data is provided to help clinicians make as informed and prudent
decisions as possible when considering the use of these intriguing biomaterials.
FDA Review of Biologic Meshes
The Food and Drug Administration (FDA) is responsible for protecting and promoting
public health through the regulation and safety of food, tobacco, dietary supplements,
drugs, vaccines, biopharmaceuticals, radiation emitting devices, veterinary products,
and medical devices. Although clinicians are not expected to be experts in federal regulatory processes, the substantial difference between FDA clearance versus approval
is important. Biologic meshes can be allografts or xenografts, with each class having
a different regulatory pathway. Biologic xenografts are considered intermediate risk
(class 2) medical devices that frequently obtain the agency’s clearance via the