Experimental study on synthetic and biological mesh implantation in a contaminated environment

A novel surgical solution to impossible fascial closure due to contaminated abdominal cavities: A case report

Introduction

Chronic, large, and old incisional hernias often lead to surgical complications and major hindrances during emergent laparotomies. The most challenging stages of the laparotomy in such cases occur during opening and fascial closure.

Case presentation

This article explains the novel surgical technique employed for the complex abdominal closure upon concluding an emergent laparotomy on a 68-year-old female patient. This innovative technique is appropriate for patients with contaminated abdominal cavities and scant fascia who require abdominal operations in cases where biological mesh is not available or is not a viable option.

Conclusion

This surgical technique can help surgeons restrict abdominal contents and organs (particularly the bowel loops) and prevent migration out of the abdominal cavity during the early post-operative stages, hence, reducing post-surgical complications. The discussed surgical technique ensures that the abdominal fascia defect is limited using skin flaps. This defect later develops into a small hernia sac within a few weeks. Patients then need to have a secondary delayed elective operation on this significantly smaller sized hernia for repair using synthetic mesh.

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In repairing large hernias, if there is no contamination, the best method is to repair with mesh.

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In the presence of contamination and small hernia, initial repair seems reasonable.

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If there is a large hernia, the use of biological mesh is a good option if possible.

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In our country, due to the existence of sanctions in such circumstances, using the proposed method can be a good alternative.

Human Primary Dermal Fibroblasts Interacting with 3-Dimensional Matrices for Surgical Application Show Specific Growth and Gene Expression Programs

Several types of 3-dimensional (3D) biological matrices are employed for clinical and surgical applications, but few indications are available to guide surgeons in the choice among these materials. Here we compare the in vitro growth of human primary fibroblasts on different biological matrices commonly used for clinical and surgical applications and the activation of specific molecular pathways over 30 days of growth. Morphological analyses by Scanning Electron Microscopy and proliferation curves showed that fibroblasts have different ability to attach and proliferate on the different biological matrices. They activated similar gene expression programs, reducing the expression of collagen genes and myofibroblast differentiation markers compared to fibroblasts grown in 2D. However, differences among 3D matrices were observed in the expression of specific metalloproteinases and interleukin-6. Indeed, cell proliferation and expression of matrix degrading enzymes occur in the initial steps of interaction between fibroblast and the investigated meshes, whereas collagen and interleukin-6 expression appear to start later. The data reported here highlight features of fibroblasts grown on different 3D biological matrices and warrant further studies to understand how these findings may be used to help the clinicians choose the correct material for specific applications.

Hernia recurrence and infection rate in elective complex abdominal wall repair using biologic mesh

Background

Elective complex ventral hernia repairs, done using synthetic mesh in patients with comorbidities, can result in mesh related complications such as hernia recurrence or infection. We studied hernia recurrence and surgical site occurrences after elective complex repairs in predominately clean cases using biologic mesh and examined the impact of several comorbidities.

Methods

A retrospective chart review was completed on patients who underwent elective repair with biologic mesh in clean/clean-contaminated settings between 2012 and 2015 with a minimum of 1-year follow-up. Multiple comorbid conditions, including diabetes, chronic obstructive pulmonary disease, steroid use, smoking history and previous hernia repairs were identified. Post-operative complications including recurrence and infections were ruled out by computed tomography, clinical exam, and/or by telephone survey.

Results

40 patients were identified. 85% (n = 34) had class 1 wounds. 25% (n = 10) experienced a hernia recurrence. 10% (n = 4) of patients developed postoperative infection, none required mesh explantation or re-operation. No statistically significant association was found between the comorbidities assessed and recurrence/infection rates.

Conclusions

We present the first study analyzing clinical outcomes of complex ventral hernia repairs using biologic mesh in predominately clean settings. This study being non-comparative limits definitive conclusions, but our aim is to add to the growing literature on biologic mesh to help future researchers performing comparative trials of synthetic versus biologic meshes.

Comparative study of four different types of intraperitoneal mesh prostheses in rats

Purpose:

To compare four types of mesh regarding visceral adhesions, inflammatory response and incorporation.

Methods:

Sixty Wistar rats were divided into four groups, with different meshes implanted intraperitoneally: polytetrafluoroethylene (ePTFE group); polypropylene with polydioxanone and oxidized cellulose (PCD); polypropylene (PM) and polypropylene with silicone (PMS). The variables analyzed were: area covered by adhesions, incorporation of the mesh and inflammatory reaction (evaluated histologically and by COX2 immunochemistry).

Results:

The PMS group had the lowest adhesion area (63.1%) and grade 1 adhesions. The ePTFE and PM groups presented almost the total area of their surface covered by adherences (99.8% and 97.7% respectively) The group ePTFE had the highest percentage of area without incorporation (42%; p <0.001) with no difference between the other meshes. The PMS group had the best incorporation rate. And the histological analysis revealed that the inflammation scores were significantly different.

Conclusions:

The PM mesh had higher density of adherences, larger area of adherences, adherences to organs and percentage of incorporation. ePTFE had the higher area of adherences and lower incorporation. The PMS mesh performed best in the inflammation score, had a higher incorporation and lower area of adherences, and it was considered the best type of mesh.

Non-Cross-Linked Collagen Mesh Performs Best in a Physiologic, Noncontaminated Rat Model

BACKGROUND

In laparoscopic incisional hernia repair, direct contact between the prosthesis and abdominal viscera is inevitable and may lead to adhesions. Despite the large variety of mesh prosthesis, little is known about their in vivo behavior. Biological meshes are considered to have many advantages, but due to their price they are rarely used. A rat model was used to assess biological and conventional synthetic meshes on their in vivo characteristics.

DESIGN

One-hundred twenty male Wistar rats were randomized into five groups of 24 rats. A mesh was implanted intraperitoneally and fixated with nonresorbable sutures. The following five meshes were implanted: Parietene (polypropylene), Permacol (cross-linked porcine acellular dermal matrix), Strattice (non-cross-linked porcine acellular dermal matrix), XCM Biologic (non-cross-linked porcine acellular dermal matrix), and Omyra Mesh (condensed polytetrafluoroethylene). The rats were sacrificed after 30, 90, or 180 days. Incorporation, shrinkage, adhesions, abscess formation, and histology were assessed for all meshes.

RESULTS

All animals thrived postoperatively. After 180 days, Permacol, Parietene, and Omyra Mesh had a significantly better incorporation than Strattice ( P = .001, P = .019, and P = .037 respectively). After 180 days, Strattice had significantly fewer adhesions on the surface of the mesh than Parietene ( P < .001), Omyra Mesh ( P = .011), and Permacol ( P = .027). After 30 days, Permacol had significantly stronger adhesions than Strattice ( P = .030). However, this difference was not significant anymore after 180 days. After 180 days, there was significantly less shrinkage in Permacol than in Strattice ( P = .001) and Omyra Mesh ( P = .050).

CONCLUSION

Based on incorporation, adhesions, mesh shrinkage, and histologic parameters, Strattice performed best in this experimental rat model.

A critical review of the in vitro and in vivo models for the evaluation of anti-infective meshes

BACKGROUND

Infectious complications following mesh implantation for abdominal wall repair appear in 0.7 up to 26.6% of hernia repairs and can have a detrimental impact for the patient. To prevent or to treat mesh-related infection, the scientific community is currently developing a veritable arsenal of antibacterial meshes. The numerous and increasing reports published every year describing new technologies indicate a clear clinical need, and an academic interest in solving this problem. Nevertheless, to really appreciate, to challenge, to compare and to optimize the antibacterial properties of next generation meshes, it is important to know which models are available and to understand them.

PURPOSE

We proposed for the first time, a complete overview focusing only on the in vitro and in vivo models which have been employed specifically in the field of antibacterial meshes for hernia repair.

RESULTS AND CONCLUSION

From this investigation, it is clear that there has been vast progress and breadth in new technologies and models to test them. However, it also shows that standardization or adoption of a more restricted number of models would improve comparability and be a benefit to the field of study.

Prophylactic, Synthetic Intraperitoneal Mesh Versus No Mesh Implantation in Patients with Fascial Dehiscence

BACKGROUND

Primary closure of post-operative facial dehiscence (FD) is associated with a high incidence of recurrence, revisional surgery, and incisional hernia. This retrospective study compares outcomes of implantation of non-absorbable intra-abdominal meshes with primary closure of FD. The outcomes of different mesh materials were assessed in subgroup analysis.

METHODS

A total of 119 consecutive patients with FD were operated (70 mesh group and 49 no mesh group) between 2001 and 2015. Primary outcome parameter was hernia-free survival. Secondary outcome parameters include re-operations of the abdominal wall, intestinal fistula, surgical site infections (SSI), and mortality. Kaplan-Meier analysis for hernia-free survival, adjusted Poisson regression analysis for re-operations and adjusted regression analysis for chronic SSI was performed.

RESULTS

Hernia-free survival was significantly higher in the mesh group compared to the no mesh group (P = 0.005). Fewer re-operations were necessary in the mesh group compared to the no mesh group (adjusted incidence risk ratio 0.44, 95% confidence interval [CI] 0.20-0.93, P = 0.032). No difference in SSI, intestinal fistula, and mortality was observed between groups. Chronic SSI was observed in 7 (10%) patients in the mesh group (n = 3 [6.7%] with polypropylene mesh and 4 [28.6%] with polyester mesh). The risk for chronic SSI was significantly higher if a polyester mesh was used when compared to a polypropylene mesh (adjusted odds ratio 8.69, 95% CI 1.30-58.05, P = 0.026).

CONCLUSION

Implantation of a polypropylene but not polyester-based mesh in patients with FD decreases incisional hernia with a low rate of mesh-related morbidity.

Characteristics of different mesh types for abdominal wall repair in an experimental model of peritonitis

BACKGROUND

The use of synthetic mesh to repair a potentially contaminated incisional hernia may lead to higher failure rates. A biological mesh might be considered, but little is known about long-term results. Both biological and synthetic meshes were investigated in an experimental model of peritonitis to assess their characteristics in vivo.

METHODS

Male Wistar rats were randomized into five groups and peritonitis was induced. A mesh was implanted after 24 h. Five meshes were investigated: Permacol™ (cross-linked collagen), Strattice™ (non-cross-linked collagen), XCM Biologic^® (non-cross-linked collagen), Omyra^® Mesh (condensed polytetrafluoroethylene) and Parietene™ (polypropylene). The rats were killed after either 30, 90 or 180 days. Incorporation and shrinkage of the mesh, adhesion coverage, strength of adhesions and histology were analysed.

RESULTS

Of 135 rats randomized, 18 died from peritonitis. Some 180 days after implantation, both XCM Biologic^® and Permacol™ had significantly better incorporation than Strattice™ (P = 0·003 and P = 0·009 respectively). Strattice™ had significantly fewer adhesions than XCM Biologic^® (P = 0·001) and Permacol™ (P = 0·020). Thirty days after implantation, Permacol™ had significantly stronger adhesions than Strattice™ (P < 0·001). Shrinkage was most prominent in XCM Biologic^® , but no significant difference was found compared with the other meshes. Histological analysis revealed marked differences in foreign body response among all meshes.

CONCLUSION

This experimental study suggested that XCM Biologic^® was superior in terms of incorporation, macroscopic mesh infection, and histological parameters such as collagen deposition and neovascularization. There must be sufficient overlap of mesh during placement, as XCM Biologic^® showed a high rate of shrinkage. Surgical relevance The use of synthetic mesh to repair a potentially contaminated incisional hernia is not supported unequivocally, and may lead to a higher failure rate. A biological mesh might be considered as an alternative. There are few long-term studies, as these meshes are expensive and rarely used. This study evaluated the use of biological mesh in a contaminated environment, and investigated whether there is an ideal mesh. A new non-cross-linked biological mesh (XCM Biologic^® ) was evaluated in this experiment. The new non-cross-linked biological mesh XCM Biologic^® performed best and may be useful in patients with a potentially contaminated incisional hernia.

Anti-inflammatory coatings of hernia repair meshes: A pilot study

The current prevalence of postoperative chronic pain from hernioplasty procedures employing polymer mesh is close to 30%. Most of the researchers agree that oxidative stress, resulting from the release of oxidants and enzymes during acute inflammatory response, is a key factor in the development of posthernioplasty complications. This results in both the decrease of the biomechanical properties and stiffening of the polymer fibers of the mesh, leading to chronic pain. Moreover, enhanced activity of inflammatory cells can lead to an excessive deposition of connective tissue around the implant. In this study polypropylene hernia repair meshes coated with vitamin E (α-tocopherol), a known antioxidant, were prepared and characterized. The absorption isotherm of vitamin E on the mesh was characterized and a release profile study yielded a promising results, showing sustained release of the drug over a 10-day period. An animal study was conducted, and histological analysis five weeks after implantation exhibited a reduced host tissue response for a modified mesh as compared to a plain mesh, as evidenced by a higher mature collagen to immature collagen ratio, as well as lower level of fatty infiltrates, neovascularization and fibrosis in the case of modified mesh. These results support the use of α-tocopherol as a potential coating in attempt to reduce the extent of postoperative inflammation, and thereby improve long-term outcomes of hernioplasty. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 589-597, 2018.

A clinically relevant in vivo model for the assessment of scaffold efficacy in abdominal wall reconstruction

An animal model that allows for assessment of the degree of stretching or contraction of the implant area and the in vivo degradation properties of biological meshes is required to evaluate their performance in vivo. Adult New Zealand rabbits underwent full thickness subtotal unilateral rectus abdominis muscle excision and were reconstructed with the non-biodegradable Peri-Guard^®, Prolene^® or biodegradable Surgisis^® meshes. Following 8 weeks of recovery, the anterior abdominal wall tissue samples were collected for measurement of the implant dimensions. The Peri-Guard and Prolene meshes showed a slight and obvious shrinkage, respectively, whereas the Surgisis mesh showed stretching, resulting in hernia formation. Surgisis meshes showed in vivo biodegradation and increased collagen formation. This surgical rabbit model for abdominal wall defects is advantageous for evaluating the in vivo behaviour of surgical meshes. Implant area stretching and shrinkage were detected corresponding to mesh properties, and histological analysis and stereological methods supported these findings.

Surgical mesh for ventral incisional hernia repairs: Understanding mesh design

Surgical mesh has become an indispensable tool in hernia repair to improve outcomes and reduce costs; however, efforts are constantly being undertaken in mesh development to overcome postoperative complications. Common complications include infection, pain, adhesions, mesh extrusion and hernia recurrence. Reducing the complications of mesh implantation is of utmost importance given that hernias occur in hundreds of thousands of patients per year in the United States. In the present review, the authors present the different types of hernia meshes, discuss the key properties of mesh design, and demonstrate how each design element affects performance and complications. The present article will provide a basis for surgeons to understand which mesh to choose for patient care and why, and will explain the important technological aspects that will continue to evolve over the ensuing years.

Surgical mesh for ventral incisional hernia repairs: Understanding mesh design

Surgical mesh has become an indispensable tool in hernia repair to improve outcomes and reduce costs; however, efforts are constantly being undertaken in mesh development to overcome postoperative complications. Common complications include infection, pain, adhesions, mesh extrusion and hernia recurrence. Reducing the complications of mesh implantation is of utmost importance given that hernias occur in hundreds of thousands of patients per year in the United States. In the present review, the authors present the different types of hernia meshes, discuss the key properties of mesh design, and demonstrate how each design element affects performance and complications. The present article will provide a basis for surgeons to understand which mesh to choose for patient care and why, and will explain the important technological aspects that will continue to evolve over the ensuing years.

Mesh Infection and Hernia Repair: A Review

BACKGROUND

The use of a prosthetic mesh to repair a tissue defect may produce a series of post-operative complications, among which infection is the most feared and one of the most devastating. When occurring, bacterial adherence and biofilm formation on the mesh surface affect the implant's tissue integration and host tissue regeneration, making preventive measures to control prosthetic infection a major goal of prosthetic mesh improvement.

METHODS

This article reviews the literature on the infection of prosthetic meshes used in hernia repair to describe the in vitro and in vivo models used to examine bacterial adherence and biofilm formation on the surface of different biomaterials. Also discussed are the prophylactic measures used to control implant infection ranging from meshes soaked in antibiotics to mesh coatings that release antimicrobial agents in a controlled manner.

RESULTS

Prosthetic architecture has a direct effect on bacterial adherence and biofilm formation. Absorbable synthetic materials are more prone to bacterial colonization than non-absorbable materials. The reported behavior of collagen biomeshes, also called xenografts, in a contaminated environment has been contradictory, and their use in this setting needs further clinical investigation. New prophylactic mesh designs include surface modifications with an anti-adhesive substance or pre-treatment with antibacterial agents or metal coatings.

CONCLUSIONS

The use of polymer coatings that slowly release non-antibiotic drugs seems to be a good strategy to prevent implant contamination and reduce the onset of resistant bacterial strains. Even though the prophylactic designs described in this review are mainly focused on hernia repair meshes, these strategies can be extrapolated to other implantable devices, regardless of their design, shape or dimension.

Experimental study of the characteristics of a novel mesh suture

Background

The failure of sutures to maintain tissue in apposition is well characterized in hernia repairs. A mesh suture designed to facilitate tissue integration into and around the filaments may improve tissue hold and decrease suture pull‐through.

Methods

In vitro, the sutures were compared for resistance to pull‐through in ballistics gel. In vivo, closure of midline laparotomy incisions was done with both sutures in 11 female pigs. Tissue segments were subsequently subjected to mechanical and histological testing.

Results

The mesh suture had tensile characteristics nearly identical to those of 0‐polypropylene suture. Mesh suture demonstrated greater resistance to pull‐through than standard suture (mean(s.d.) 4·27(0·42) versus 2·23(0·48) N; P < 0·001) in vitro. In pigs, the ultimate tensile strength for repaired linea alba at 8 days was higher with mesh suture (320(57) versus 160(56) N; P < 0·001), as was the work to failure (24·6(14·2) versus 7·3(3·7) J; P < 0·001) and elasticity (128(9) versus 72(7) N/cm; P < 0·001) in comparison with 0‐polypropylene suture. Histological examination at 8 and 90 days showed complete tissue integration of the mesh suture.

Conclusion

The novel mesh suture structure increased the strength of early wound healing in an experimental model.

Prospective repair of Ventral Hernia Working Group type 3 and 4 abdominal wall defects with condensed polytetrafluoroethylene (MotifMESH) mesh

BACKGROUND

Treatment of clean-contaminated and contaminated ventral hernia defects remains controversial. Newer prosthetic materials may play an important role in these patients.

METHODS

Ten patients with Ventral Hernia Working Group types 3 and 4 were prospectively enrolled and subsequently treated with direct supported repairs with condensed fenestrated polytetrafluoroethylene mesh. The primary outcome was hernia occurrence at 1 year after surgery. Secondary outcomes included surgical site infection, surgical site occurrence, medical complications, pain, and other patient-reported outcomes.

RESULTS

There were no immediate postoperative infections and one minor postoperative hematoma treated in the office. One patient required delayed mesh removal 9 months after placement. Importantly, the mesh removal procedure was straightforward because of the material properties of the mesh. Of the 9 patients still with mesh, there were no hernia recurrences at the repair site with one full year of follow-up.

CONCLUSION

Contaminated and clean-contaminated abdominal wall defects can be effectively and durably treated with condensed polytetrafluoroethylene mesh.

The prevention of colorectal anastomotic leakage with tissue adhesives in a contaminated environment is associated with the presence of anti-inflammatory macrophages

BACKGROUND

Colorectal anastomoses created in a contaminated environment result in a high leakage rate. This study investigated whether using anastomotic sealants (TissuCol(®), Histoacryl(®) Flex, and Duraseal(®)) prevents leakage in a rat peritonitis model.

STUDY DESIGN

Sixty-seven Wistar rats were divided into control and experimental groups (TissuCol, Histoacryl, and Duraseal groups). Peritonitis was induced 1 day before surgery with the cecal ligation puncture model. On day 0, colonic anastomosis was constructed with sutures and then sealed with no adhesive (control group) or one select adhesive (experimental groups). Bursting pressure, abscess formation, and adhesion severity were evaluated on day 3 or day 14. Hematoxylin and eosin staining and immunohistochemical staining for CD4, CD8, CD206, and iNOS were performed.

RESULTS

On day 3, bursting pressures of the TissuCol group (120.1 ± 25.3 mmHg), Histoacryl group (117.3 ± 20.2 mmHg), and Duraseal group (123.6 ± 35.4 mmHg) were significantly higher than the that of the control group (24.4 ± 31.7 mmHg, p < 0.001). Abscesses around the anastomosis were found in the control group (6/7) and Duraseal group (2/9) but not in the TissuCol group or Histoacryl group. A higher number of CD206+ cells (M2 macrophages), a lower number of iNOS+ cells (M1 macrophages), a higher M2/M1 index, and a higher CD4+/CD8+ index were seen at the anastomotic site in all experimental groups compared with the control group on day 3. On day 14, abscesses were only found in the control group. Adhesion severity in the Duraseal group was significantly lower than that in the control group (p = 0.001).

CONCLUSIONS

Anastomotic sealing using TissuCol(®), Histoacryl(®) Flex, or Duraseal(®) seems to be an effective and safe option to prevent leakage in contaminated colorectal surgery. The presence of large numbers of anti-inflammatory macrophages seems to be involved in preventing the leakage.

Effects of macroporous monofilament mesh on infection in a contaminated field

BACKGROUND

The aim of this study was to evaluate whether the type of the mesh and proper surgical technique can influence the outcome of a tension-free hernia repair in a contaminated filed.

MATERIALS AND METHODS

This study was based on the model of bacterial peritonitis in rats induced with a mixture composed of Escherichia coli and Bacteroides fragilis. Two animals were used as a control group without induced peritonitis and 10 animals with mesh implanted inside of the peritoneal cavity. For the 20 animals in the studied group, bacterial fluid was applied into the abdominal cavity together with the mesh implantation. In 10 cases, the mesh was fixed flatly upon the surface of the peritoneum; in the other 10, the mesh was rolled and then fixed within the peritoneal cavity. After 5 weeks, the animals were operated on again, and the meshes, the peritoneal fluid and, if present, any granulomas were taken for bacterial cultivation.

RESULTS

The results of the bacterial cultivation of the material from the control group (without mesh) and from the rats with flatly fixed mesh were almost completely negative (0/10 and 1/10, respectively). In 9 out of 10 rats that were exposed to the rolled mesh for 5 weeks, the colonisation of meshes with both B. fragilis and E. coli was found (p < 0.0198).

CONCLUSIONS

When properly fixed, flat mesh, even in a contaminated field, may allow for a proper mesh healing and does not influence the ability to cure bacterial peritonitis in an animal model. A bad surgical technique, such as inadequately positioned or rolled mesh, may cause persistent peritoneal bacteraemia.

Properties of novel composite meshes in chest wall reconstruction: A comparative animal study

PURPOSE

Novel composite meshes routinely used in laparoscopic hernia repair reportedly lead to fewer and less dense visceral adhesions and may provide a viable alternative in thoracic surgery as well.

METHODS

A total of 15 adult domestic pigs underwent full thickness chest wall resection and reconstruction with Parietene (polypropylene composite; PTE, n = 5), Parietex (polyester composite; PTX, n = 5) or Bard (purely polypropylene, n = 5) mesh. After an observation period of 90 days all animals were sacrificed, intrathoracic adhesions classified via thoracoscopy (VATS), meshes explanted and peak peal strength required for lung/mesh separation recorded.

RESULTS

Adhesions assessed through VATS-exploration were strongest in the PTX-Group while PTE and BM showed comparable results. Tensiometric analyses of peak peal strength confirmed lower values in BM than for PTE and PTX. Both composite materials showed good overall bioincorporation with post-surgical perigraft-fibrosis being strongest in BM.

CONCLUSION

We consider composite grafts a suitable alternative for chest wall reconstruction. They are characterized by good overall biointegration and limited perigraft-fibrosis, thus potentially facilitating redo-procedures, even though a hydrophilic coating per se does not appear to prevent intrathoracic adhesion formation.

In vitro model to study the biomaterial-dependent reaction of macrophages in an inflammatory environment

Background

Macrophages play an important role in the reaction to biomaterials, which sometimes have to be used in a surgical field at risk of contamination. The macrophage phenotype in reaction to biomaterials in an inflammatory environment was evaluated in both an in vivo and in vitro setting.

Methods

In the in vivo setting, polypropylene (PP) biomaterial was implanted for 28 days in the contaminated abdominal wall of rats, and upon removal analysed by routine histology as well as immunohistochemistry for CD68 (marker for macrophages), inducible nitric oxide synthase (iNOS – a marker for proinflammatory M1 macrophages) and CD206 (marker for anti-inflammatory M2 macrophages). For the in vitro model, human peripheral blood monocytes were cultured for 3 days on biomaterials made from PP, collagen (COL), polyethylene terephthalate (PET) and PET coated with collagen (PET+COL). These experiments were performed both with and without lipopolysaccharide and interferon γ stimulation. Secretion of both M1- and M2-related proteins was measured, and a relative M1/M2 index was calculated.

Results

In vivo, iNOS- and CD206-positive cells were found around the fibres of the implanted PP biomaterial. In vitro, macrophages on both PP and COL biomaterial had a relatively low M1/M2 index. Macrophages on the PET biomaterial had a high M1/M2 index, with the highest increase of M1 cytokines in an inflammatory environment. Macrophages on the PET+COL biomaterial also had a high M1/M2 index.

Conclusion

Macrophages in an inflammatory environment in vitro still react in a biomaterial-dependent manner. This model can help to select biomaterials that are tolerated best in a surgical environment at risk of contamination.

Surgical relevance

Biomaterials in an environment at risk of contamination are often not tolerated owing to a high risk of postoperative infection, which may ultimately lead to removal of the biomaterial.

An in vitro model with primary human macrophages was used to provide insight into the acute reaction of macrophages to a biomaterial in an inflammatory environment simulated with lipopolysaccharide and interferon γ. The reaction of macrophages in such an inflammatory environment was still biomaterial-dependent.

This in vitro model can be used to study the reaction of macrophages to different biomaterials in an inflammatory environment in more detail, and thereby help to select biomaterials that are tolerated best in a surgical environment at risk of contamination.

Use of a Bioprosthetic Mesh in Complex Hernia Repair

Background. Implantation of synthetic meshes for reinforcement of abdominal wall hernias can be complicated by mesh infection, which often requires mesh explantation. The risk of mesh infection is increased in a contaminated environment or in patients who have comorbidities such as diabetes or smoking. The use of biological prostheses has been advocated because of their ability to resist infection. Initial results, however, have shown high hernia recurrence rates and wound occurrences. The objective of the present study is to evaluate early and mid-term outcomes in the largest French series that included 43 consecutive complex abdominal hernias repaired with biological prostheses. Materials and methods. Retrospective observational study of a prospective collected data bank. Patient demographics, history of previous repairs, intraoperative findings and degree of contamination, associated procedures, postoperative prosthetic-related complications, and long-term results were retrospectively reviewed. Results. There were 25 (58%) incisional, 14 parastomal, and 4 midline hernia repairs. Hernias were considered “clean” (n = 5), “clean-contaminated” (n = 19), “contaminated” (n = 12), or “dirty” (n = 7). Wound-related morbidity occurred in 17 patients; 4 patients needed reoperation for cutaneous necrosis or abscess. Smoking was the only risk factor associated with wound complication ( P = .022). No postoperative wound events required removal of the prosthesis. There were 4 hernia recurrences (9%). A previous attempt at repair ( P = .018) and no complete fascia closure ( P = .033) were associated with hernia recurrence. Conclusions. This study demonstrated that the use of bioprothesis in complex hernia repair allowed successful single-stage reconstruction. Wound-related complications were frequent. Cost-benefit analyses are important to establish the validity of these findings.