Long term comparative evaluation of two types of absorbable meshes in partial abdominal wall defects: an experimental study in rabbits.

PURPOSE: Synthetic prosthetic materials that are fully absorbable seek to reduce the host foreign body reaction and promote host tissue regeneration. This preclinical trial was designed to analyse, in the long term, the behaviour of two prosthetic meshes, one synthetic and one composed of porcine collagen, in abdominal wall reconstruction. METHODS: Partial defects were created in the abdominal walls of New Zealand rabbits and repaired using a synthetic absorbable mesh (Phasix™) or a non-crosslinked collagen bioprosthesis (Protexa™). After 3, 6, 12 and 18 months, specimens were recovered for light microscopy and collagen expression analysis to examine new host tissue incorporation, macrophage response and biomechanical strength. RESULTS: Both materials showed good host tissue incorporation in line with their spatial structure. At 18 months postimplant, Protexa™ was highly reabsorbed while the biodegradation of Phasix™ was still incomplete. Collagenization of both materials was good. Macrophage counts steadily decreased over time in response to Phasix™, yet persisted in the collagen meshes. At 18 months, zones of loose tissue were observed at the implant site in the absence of herniation in both implant types. The stress-stretch behaviour of Phasix™ implants decreased over time, being more pronounced during the period of 12-18 months. Nevertheless, the abdominal wall repaired with Protexa™ became stiffer over time. CONCLUSION: Eighteen months after the implant both materials showed good compatibility but the biodegradation of Phasix™ and Protexa™ was incomplete. No signs of hernia were observed at 18 months with the stress-stretch relations being similar for both implants, regardless of the more compliant abdominal wall repaired with Protexa™ at short term.

Efficacy of antimicrobial agents delivered to hernia meshes using an adaptable thermo-responsive hyaluronic acid-based coating.

PURPOSE: Mesh-related infection is a critical outcome for patients with hernia defect stabilized with synthetic or biological meshes. Even though bioactive meshes loaded with antibiotics or antiseptics are slowly emerging in the market, the available solutions still lack versatility. Here, we proposed a polymer solution, i.e., hyaluronic acid-poly(N-isopropylacrylamide) (HApN), which forms a hydrogel to be used as coating for meshes only when it reaches body temperature. METHODS: We assessed how the gelation of HApN was influenced by the incorporation of different antibiotic and antiseptic formulations, and how this gel can be used to coat several mesh types. The impact of the coating on the elastic behavior of a macroporous mesh was tested under cyclic elongation condition. Finally, we selected two different coating formulations, one based on antibiotics (gentamicin + rifampicin) and one based on antiseptic (chlorhexidine) and tested in vitro their antimicrobial efficacies. RESULTS: HApN can be used as carrier for different antimicrobial agents, without having a strong influence on its gelation behavior. Porous or dense meshes can be coated with this polymer, even though the stability was not optimal on macroporous meshes such as Optilene when pores are too large. HApN loaded with drugs inhibited in vitro the growth of several Gram-positive and Gram-negative bacteria. CONCLUSION: Compared to the available technologies developed to endow meshes with antibacterial activity, the proposed HApN offers further versatility with potential to prevent mesh-related infection in hernioplasty.

Experimental study on the use of a chlorhexidine-loaded carboxymethylcellulose gel as antibacterial coating for hernia repair meshes.

PURPOSE: Biomaterials with an antimicrobial coating could avoid mesh-associated infection following hernia repair. This study assesses the use of a chlorhexidine-loaded carboxymethylcellulose gel in a model of Staphylococcus aureus mesh infection. METHODS: A 1% carboxymethylcellulose gel containing 0.05% chlorhexidine was prepared and tested in vitro and in vivo. The in vitro tests were antibacterial activity (S. aureus; agar diffusion test) and gel cytotoxicity compared to aqueous 0.05% chlorhexidine (fibroblasts; alamarBlue). For the in vivo study, partial abdominal wall defects (5 × 2 cm) were created in New Zealand white rabbits (n = 15) and inoculated with 0.25 mL of S. aureus (106 CFU/mL). Defects were repaired with a lightweight polypropylene mesh (Optilene) without coating (n = 3) or coated with a carboxymethylcellulose gel (n = 6) or chlorhexidine-loaded carboxymethylcellulose gel (n = 6). Fourteen days after surgery, bacterial adhesion to the implant (sonication, immunohistochemistry), host tissue incorporation (light microscopy) and macrophage reaction (immunohistochemistry) were examined. RESULTS: Carboxymethylcellulose significantly reduced the toxicity of chlorhexidine (p < 0.001) without limiting its antibacterial activity. While control and gel-coated implants were intensely contaminated, the chlorhexidine-gel-coated meshes showed a bacteria-free surface, and only one specimen showed infection signs. The macrophage reaction in this last group was reduced compared to the control (p < 0.05) and gel groups. CONCLUSIONS: When incorporated in the carboxymethylcellulose gel, chlorhexidine showed reduced toxicity yet maintained its bactericidal effect at the surgery site. Our findings suggest that this antibacterial gel-coated polypropylene meshes for hernia repair prevent bacterial adhesion to the mesh surface and have no detrimental effects on wound repair.

Biomechanical and histologic evaluation of two application forms of surgical glue for mesh fixation to the abdominal wall.

The use of an adhesive for mesh fixation in hernia repair reduces chronic pain and minimizes tissue damage in the patient. This study was designed to assess the adhesive properties of a medium-chain (n-butyl) cyanoacrylate glue applied as drops or as a spray in a biomechanical and histologic study. Both forms of glue application were compared to the use of simple-loose or continuous-running polypropylene sutures for mesh fixation. Eighteen adult New Zealand White rabbits were used. For mechanical tests in an ex vivo and in vivo study, patches of polypropylene mesh were fixed to an excised fragment of healthy abdominal tissue or used to repair a partial abdominal wall defect in the rabbit respectively. Depending on the fixation method used, four groups of 12 implants each or 10 implants each respectively for the ex vivo and in vivo studies were established: Glue-Drops, Glue-Spray, Suture-Simple and Suture-Continuous. Biomechanical resistance in the ex vivo implants was tested five minutes after mesh fixation. In vivo implants for biomechanical and histologic assessment were collected at 14 days postimplant. In the ex vivo study, the continuous suture implants showed the highest failure sample tension, while the implants fixed with glue showed lower failure sample tension values. However, the simple and continuous suture implants returned the highest stretch values. In the in vivo implants, failure sample tension values were similar among groups while the implants fixed with a continuous running suture had the higher stretch values, and the glue-fixed implants the lower stretch values. All meshes showed good tissue integration within the host tissue regardless of the fixation method used. Our histologic study revealed the generation of a denser, more mature repair tissue when the cyanoacrylate glue was applied as a spray rather than as drops.

In vitro assessment of an antibacterial quaternary ammonium-based polymer loaded with chlorhexidine for the coating of polypropylene prosthetic meshes.

PURPOSE: This study assesses the use of an absorbable polymer loaded with chlorhexidine (CHX) as an antibacterial coating for polypropylene (PP) meshes employed in hernia repair. METHODS: The polymer N,N-dimethyl-N-benzyl-N-(2-methacryloyloxyethyl) ammonium bromide was loaded with CHX (1 % w/w). Fragments (1 cm2) of Optilene® Mesh Elastic were coated either with the unloaded (POL) or CHX-loaded polymer (POL-CHX). Uncoated fragments (PP) served as controls. The release kinetics of the POL-CHX coating was monitored by HPLC. Sterile fragments were placed on agar plates previously contaminated with 106 CFU of Staphylococcus aureus (Sa) ATCC25923, Staphylococcus epidermidis (Se) ATCC12228, or Escherichia coli (Ec) ATCC25922 and incubated at 37 °C for 1/2/7 days. At each time point, inhibition halos were measured and bacterial adhesion to the meshes quantified by sonication and scanning electron microscopy. Coating cytotoxic effects were examined on cultured fibroblasts. RESULTS: The polymer coating gradually released CHX over 3 days. Inhibition halos were produced only around the POL-CHX-coated meshes and these were significantly smaller for Ec than Sa or Se (p < 0.01). While POL-CHX prevented bacterial adhesion to the mesh, the reduced bacterial yields over time were observed for the POL-coated versus control PP meshes (p < 0.001). By day 7, only Ec remained attached to the surface of control meshes. The POL coating was not cytotoxic, yet POL-CHX reduced the viability of cultured fibroblasts. CONCLUSIONS: When loaded with the antiseptic CHX, this quaternary ammonium-based polymer coating released its contents in a controlled manner indicating its potential prophylactic use to reduce the risk of infection following PP mesh implantation.

Biomechanical and morphological study of a new elastic mesh (Ciberlastic) to repair abdominal wall defects.

The aim of this study was to conduct a preclinical evaluation of the behaviour of a new type of abdominal LW prosthesis (Ciberlastic), which was designed with a non-absorbable elastic polyurethane monofilament (Assuplus, Assut Europe, Italy) to allow greater adaptability to mechanical area requirements and higher bio-mimicking with the newly formed surrounding tissues. Our hypothesis was that an increase in the elasticity of the mesh filament could improve the benefits of LW prostheses. To verify our hypothesis, we compared the short- and long-term behaviour of Ciberlastic and Optilene(®) elastic commercial meshes by repairing the partially herniated abdomen in New Zealand White rabbits. The implanted meshes were mechanically and histologically assessed at 14 and 180 days post-implant. We mechanically characterized the partially herniated repaired muscle tissue and also determined mesh shrinkage at different post-implant times. This was followed by a histological study in which the tissue incorporation process was analysed over time. The new prosthesis designed by our group achieved good behaviour that was similar to that of Optilene(®), one of the most popular LW prostheses on the market, with the added advantage of its elastic property. The mechanical properties are significantly lower than those of the polypropylene Optilene(®) mesh, and the new elastic mesh meets the basic mechanical requirements for positioning in the abdominal wall, which was also demonstrated by the absence of recurrences after implantation in the experimental model. We found that the growth of a connective tissue rich in collagen over the hernial defect and the proper deposit of the collagen fibres in the regenerated tissue substantially modified the original properties of the mesh, thereby increasing its biomechanical strength and making the whole tissue/mesh stiffer.

Tissue integration and inflammatory reaction in full-thickness abdominal wall repair using an innovative composite mesh.

PURPOSE: When composite meshes are used in abdominal wall repair, seroma formation may persist and delay the desired integration leading to recurrence. This study compares tissue integration and inflammatory response in abdominal wall repair with composites with different absorbable synthetic barriers. METHODS: Full-thickness defects created in the abdominal wall of rabbits were repaired using polypropylene prosthesis or the following composites: Physiomesh™ (Phy); Ventralight™ (Vent) and "new composite mesh" (Ncm) not yet used clinically in humans. The collected seroma was evaluated for IFN-γ/IL-4 by ELISA. Tissue integration, anti- (IL-13/TGFß-1/IL-10/IL-4) and pro-inflammatory (TNF-α/IL-6/IFN-γ/VEGF) cytokine mRNA expression and TGFß/VEGF immunolabeling were evaluated at 14 and 90 days post-implant. RESULTS: Seroma was observed in 10 of 12 Phy/Vent and 4 of 12 Ncm. Wound fluid IFN-γ showed a time-dependent significant increase in Vent and tendency to decrease in Ncm, while all composites exhibited IL-4 upward trend. Prostheses were fully infiltrated by an organized connective tissue at end time although the area had shown prior seroma. A stable mesothelium was developed, except in adhesion areas. Vent/Phy displayed a significant increase in TNF-α/IFN-γ-mRNA over time. Significant decrease in VEGF mRNA was observed in Phy/Ncm, while a significant increase of TGFß-1 mRNA was evident in all composites over time. Ncm exhibited the highest TGFß protein expression area at short term and the greatest percentage of VEGF positive vessels at end time. CONCLUSION: Ncm could be an appropriate candidate to improve clinical outcome showing the lower development of seroma and optimal tissue integration with minimal pro-inflammatory cytokine response over time and consistent pro-wound healing cytokine expression.

Biaxial Mechanical Evaluation of Absorbable and Nonabsorbable Synthetic Surgical Meshes Used for Hernia Repair: Physiological Loads Modify Anisotropy Response.

The aim of this study was to obtain information about the mechanical properties of six meshes commonly used for hernia repair (Surgipro(®), Optilene(®), Infinit(®), DynaMesh(®), Ultrapro™ and TIGR(®)) by planar biaxial tests. Stress-stretch behavior and equibiaxial stiffness were evaluated, and the anisotropy was determined by testing. In particular, equibiaxial test (equal simultaneous loading in both directions) and biaxial test (half of the load in one direction following the Laplace law) were selected as a representation of physiologically relevant loads. The majority of the meshes displayed values in the range of 8 and 18 (N/mm) in each direction for equibiaxial stiffness (tangent modulus under equibiaxial load state in both directions), while a few achieved 28 and 50 (N/mm) (Infinit (®) and TIGR (®)). Only the Surgipro (®) mesh exhibited planar isotropy, with similar mechanical properties regardless of the direction of loading, and an anisotropy ratio of 1.18. Optilene (®), DynaMesh (®), Ultrapro (®) and TIGR (®) exhibited moderate anisotropy with ratios of 1.82, 1.84, 2.17 and 1.47, respectively. The Infinit (®) scaffold exhibited very high anisotropy with a ratio of 3.37. These trends in material anisotropic response changed during the physiological state in the human abdominal wall, i.e. T:0.5T test, which the meshes were loaded in one direction with half the load used in the other direction. The Surgipro (®) mesh increased its anisotropic response (Anis[Formula: see text] = 0.478) and the materials that demonstrated moderate and high anisotropic responses during multiaxial testing presented a quasi-isotropic response, especially the Infinit(®) mesh that decreased its anisotropic response from 3.369 to 1.292.

Bacterial adhesion to biological versus polymer prosthetic materials used in abdominal wall defect repair: do these meshes show any differences in vitro?

PURPOSE: Although clinical data suggest the similar performance of collagen-based biological prosthetic materials to some polymer materials, the use of a biomesh for abdominal hernia repair in a setting of infection is controversial. This in vitro study compares the adhesion of two Staphylococcus strains to polymer and biological meshes. METHODS: Sterile fragments of Optilene(®) (Op), Surgipro™ (Surg), Preclude(®) (Precl), TIGR(®) (TIGR), Bio-A(®) (BioA), Permacol™ (Perm), Surgisis(®) (SIS), and Tutomesh(®) (Tuto) were inoculated with 10(6) CFU of S. aureus (Sa) or S. epidermidis (Se) (n = 18 per strain per mesh). The first five meshes are polymer materials while Perm, SIS and Tuto are biomeshes. After 24/48 h of incubation, bacterial adhesion was examined by sonication, scanning electron microscopy (SEM) and light microscopy. RESULTS: Sa and Se showed a high affinity for the absorbable meshes (TIGR, BioA, Perm, SIS, Tuto) (p < 0.001). Precl yielded the lowest bacterial loads (p < 0.001). Surg, Precl and BioA underwent no substantial change over time, while Op (p < 0.001) and TIGR (p < 0.05) showed decreasing bacterial loads during incubation. The Sa-contaminated biomeshes behaved similarly while biomeshes inoculated with Se returned higher bacterial yields at 48 h, especially SIS (p < 0.001). SEM and light microscopy observations revealed planktonic bacteria and biofilms on the polymer surface and bacterial niches in biomesh pores. CONCLUSIONS: Within 48 h of contamination, the absorbable polymer and biological meshes exhibited high bacterial loads. Given their lower affinity for both bacterial strains, the conventional non-absorbable polymer materials could be better candidates for use in contaminated surgical fields.

Extraperitoneal and intraperitoneal behavior of several biological meshes currently used to repair abdominal wall defects.

BACKGROUND: This study compares the behavior of several cross- and noncrosslinked biomeshes (Permacol®, CollaMend®, Surgisis®, Tutomesh®, and Strattice®) currently used for abdominal wall repair when implanted intraperitoneally and extraperitoneally. Material and Methods. Intraperitoneal (IP) implants were fixed on the parietal peritoneum and partial abdominal wall defects (EP) were repaired using each of the biomeshes, in the rabbit abdominal wall. After 90 days of implant, the biomeshes were examined to assess biomesh degradation, collagen I and III expression (Sirius red staining) and the host macrophage response (immunohistochemistry). Results. Following implant, the thinner noncrosslinked biomeshes Tutomesh and Surgisis, were almost fully degraded in both models. In contrast, Strattice behavior was similar to crosslinked biomeshes, showing negligible degree of degradation. This mesh also showed high expression of collagen I, similar to the crosslinked. The noncrosslinked materials elicited lower macrophage counts, significantly so for Strattice. In IP and EP models, Permacol showed similarly high macrophages while counts were lower for CollaMend and Surgisis in the EP model. Conclusions. The intra or extraperitoneal implant of the different meshes did not affect host tissue incorporation or mesh degradation. The crosslinked biomeshes induced a more intense macrophage response regardless of their IP or EP location.

Intraperitoneal behaviour of a new composite mesh (Parietex™ Composite Ventral Patch) designed for umbilical or epigastric hernia repair.

INTRODUCTION: The most common treatment option for ventral and umbilical hernias is the implant of a prosthetic mesh. This study compares the behaviour of a new mesh, Parietex™ Composite Ventral Patch (Ptx), with two commercially available meshes, Ventralex™ ST Hernia Patch and Proceed™ Ventral Patch. MATERIALS AND METHODS: The following meshes were tested in a umbilical-hernia repair model using 54 rabbits: Ventralex™ ST Hernia Patch (Vent) (Bard Davol Inc., USA); Proceed™ Ventral Patch (PVP) (Ethicon, USA) and Ptx (Covidien, Sofradim, France) (n = 18 each). At 3, 7 and 14 days postimplantation, peritoneal behaviour and adhesion formation were assessed by sequential laparoscopy. Adhesions were scored for consistency and quantified by image analysis. The animals were euthanized at 2 (n = 27) and 6 weeks (n = 27) postsurgery. Mesothelial cover of meshes and tissue ingrowth were determined by scanning and light microscopy. RESULTS: Seroma was observed in 1/18 Vent, 7/18 PVP and 4/18 Ptx, mainly between the implant and subcutaneous tissue. Firm omental adhesions between the mesh and parietal peritoneum were noted in 2/9 Vent, 6/9 PVP and 3/9 Ptx at 2 weeks and in 3/9 Vent, 5/9 PVP and 1/9 Ptx at 6 weeks. Three (out of 9) encapsulated PVP implants showed "tissue-integrated" adhesions affecting the intestinal loops. No differences between implants were detected in the surface area occupied by adhesions at 2 weeks, though at 6 weeks, percentages were significantly higher (p < 0.01; Mann-Whitney U test) for PVP compared to Ptx or Vent. At this time point, Ptx and Vent showed good host tissue incorporation and optimal mesothelialization. CONCLUSIONS: The PVP implants showed greater adhesion formation than the other materials. Postimplantation behaviour was comparable for Ptx and Vent including scarce adhesion formation and optimal mesothelialization. Regarding tissue integration, Ptx showed greater long-term collagenization of the neoformed tissue.

Short- and long-term biomechanical and morphological study of new suture types in abdominal wall closure.

To perform an abdominal-wall closure, a continuous suture is the preferred method. The suture materials that are most commonly employed in abdominal surgery are polypropylene and polydioxanone. However, in recent times, new products have been marketed, such as non-absorbable polyurethane with elastic properties (Assuplus(®), Assut Europe, Italy) and absorbable barbed polydioxanone (Filbloc(®), Assut Europe, Italy). The purpose of this study was to compare the ability of those against the standard polypropylene (Surgipro(TM), Covidien, USA) and polydioxanone (Assufil(®), Assut Europe, Italy) to mimic the biomechanical behavior of the abdominal wall closure. Comparison of the sutures was made first with the materials alone and later in a laparotomy closure of a rabbit abdomen, used as an animal model. The biomechanical analysis consisted of uniaxial tensile tests of threads and sutured samples of the animal abdomen. In the latter case, results were analyzed at short- (21days) and long- (180days) term intervals after the surgery. The morphology studies and collagen expression of the samples were also investigated. The results determined that polydioxanone and polypropylene sutures showed a linear elastic behavior, with barbed polydioxanone as the most compliant suture and polyurethane as the stiffest. The sutured samples showed a statistically significant loss of resistance, measured as the load needed to perform a certain stretch, when compared with the corresponding control tissue. Analysis of the stress-stretch curves showed that elastic polyurethane was the only suture able to reproduce the mechanical behavior of healthy tissue in the short term, while the rest of the sutures remained less stiff. This coincides with the expression of type I collagen observed in this group at this point in the study. In the long term, there was no difference among the sutures, and none was able to mimic control behavior.

Computational framework to model and design surgical meshes for hernia repair.

Surgical procedures for hernia surgery are usually performed using prosthetic meshes. In spite of all the improvements in these biomaterials, the perfect match between the prosthesis and the implant site has not been achieved. Thus, new designs of surgical meshes are still being developed. Previous to implantation in humans, the validity of the meshes has to be addressed, and to date experimental studies have been the gold standard in testing and validating new implants. Nevertheless, these procedures involve long periods of time and are expensive. Thus, a computational framework for the simulation of prosthesis and surgical procedures may overcome some disadvantages of the experimental methods. The computational framework includes two computational models for designing and validating the behaviour of new meshes, respectively. Firstly, the beam model, which reproduces the exact geometry of the mesh, is set to design the weave and determine the stiffness of the surgical prosthesis. However, this implies a high computational cost whereas the membrane model, defined within the framework of the large deformation hyperelasticity, is a relatively inexpensive computational tool, which also enables a prosthesis to be included in more complex geometries such as human or animal bodies.

Postimplantation host tissue response and biodegradation of biologic versus polymer meshes implanted in an intraperitoneal position.

BACKGROUND: This study compared the in vitro and in vivo behaviors at the peritoneal interface of a new polymer material (Bio-A) and of two biologic non-cross-linked materials (Tutomesh [Tuto] and Strattice [St]), all biodegradable. METHODS: Omentum mesothelial cells from rabbits were seeded onto the three prosthetic materials tested. At 1, 4, 8, 16, and 24 h after implantation, mesothelial cover was performed using a scanning electron microscope (SEM). In the in vivo study, 3 × 3 cm mesh fragments were placed on the parietal peritoneum of the same rabbits and fixed at the four corners with individual stitches. The implants were randomized such that six fragments of each material were implanted in nine animals (2 per animal). Adhesion formation was quantified by sequential laparoscopy and image analysis 3, 7, and 14 days after implantation. The animals were killed at 90 days, and the meshes were subjected to microscopy and immunohistochemistry. RESULTS: The in vitro mesothelial cover was significantly greater for St than for Bio-A at each time point. The percentage of cover for St was also higher than for Tuto 16 and 24 h after seeding and higher for Tuto than for Bio-A at all time points. Compared with the biologic meshes, significantly higher adhesion percentages were recorded for Bio-A. At 90 days after implantation, differences in absorption measured as percentage of reduction in mesh thickness were detected among all the meshes. The least absorbed was St. The neoperitoneum thickness was significantly greater for the biologic meshes than for the polymer mesh, although this variable also differed significantly between St and Tuto. Macrophage counts were higher for Bio-A than for the biologic meshes. CONCLUSIONS: Greater mesothelial cover was observed in vitro for St. In vivo, adhesion formation and the macrophage response induced by Bio-A were greater than those elicited by the biologic materials. Bio-A and Tuto showed substantial biodegradation compared with St.

Long term behavior of biological prostheses used as abdominal wall substitutes.

BACKGROUND: Despite their degradation in the host organism, the benefits of collagen bioprostheses remain unclear. This study addresses the absorption and long-term host tissue incorporation of several collagen biomeshes. MATERIAL AND METHODS: Partial ventral hernial defects created in the abdominal wall of rabbits were repaired using the crosslinked meshes Permacol® or CollaMend®, or the non-crosslinked Surgisis®, Tutomesh® or Strattice®. After 90 and 180 days of implant, morphological studies and morphometric analysis of the thickness of the meshes were performed. Immunofluorescence confocal microscopy combined with differential interference contrast (DIC) imaging was used to distinguish newly formed collagen from that comprising the mesh. The macrophage response was examined by immunohistochemistry. RESULTS: At 90 days, the thinner non-crosslinked biomeshes Tutomesh and Surgisis were more fully degraded with much of their collagen replaced with loose connective tissue. By 180 days, both implants had been practically fully absorbed. In contrast, in Strattice only the outermost third was infiltrated by neoformed tissue. On both surfaces of the crosslinked meshes, a fibrous capsule with host cells lining its perimeter was observed at both time points, though at 180 days these cells had penetrated the mesh interior. At both implant times, Strattice showed the higher expression of collagen type I while collagen III expression was similar for all the meshes. The non-crosslinked materials elicited lower macrophage counts at both time points, significantly so for Strattice. The macrophage response decreased over time for all the meshes but Surgisis. CONCLUSIONS: Strattice, the thicker, more compacted non-crosslinked mesh showed the best balance between tissue incorporation and absorption while eliciting a minimal foreign-body reaction in the long-term.

Short-term behavior of different polymer structure lightweight meshes used to repair abdominal wall defects.

BACKGROUND: While lightweight (LW) polypropylene (PP) meshes are been used for hernia repair, new prosthetic meshes also of low-density and with large pores have recently been introduced composed of other polymer materials. This study compares the behavior in the short-term of two macroporous LW prosthetic materials, PP and non-expanded PTFE. METHODS: Partial defects were created in the lateral wall of the abdomen in New Zealand White rabbits and then repaired using a LW PP mesh or a new monofile, LW PTFE mesh. At 14 days postimplant, shrinkage and tissue incorporation, gene and protein expression of neo-collagens (qRT-PCR/immunofluorescence), macrophage response (immunohistochemistry) and biomechanical strength were determined. RESULTS: Both meshes induced good host tissue ingrowth, yet the macrophage response was significantly greater for the PTFE implants (p⟨0.05). Collagen 1/3 mRNA expression was greater for the PP mesh but differences lacked significance. Similar patterns of collagen I and III protein expression were observed in the neoformed tissue infiltrating the two meshes. After 14 days of implant, tensile strengths were also similar, while elastic modulus values were higher for the PTFE mesh (p⟨0.05). CONCLUSIONS: In the short term, host collagen deposition and biomechanical performance seemed unaffected by the polymer structure of the implanted mesh. In contrast, the inflammatory response to mesh implant produced at this early time point was more intense for the PTFE.

Understanding the passive mechanical behavior of the human abdominal wall.

The aim of this work is to present a methodology to model the passive mechanical behavior of the human abdomen during physiological movements. From a mechanical point of view, it is possible to predict where hernia formation is likely to occur since the areas that support higher stresses can be identified as the most vulnerable ones. For this purpose, a realistic geometry of the human abdomen is obtained from magnetic resonance imaging. The model defines different anatomical structures of the abdomen, including muscles and aponeuroses, and anisotropic mechanical properties are assigned. The finite element model obtained from the geometric human model, which includes initial strains, is used to simulate the anisotropic passive behavior of the healthy human abdomen under intra-abdominal pressure. This study demonstrates that the stiffest structures, namely aponeuroses and particularly the linea alba, are the structures that perform the most work in the abdomen. Thus, the linea alba is the most important unit contributing to the mechanical stability of the abdominal wall.