Does presoaking synthetic mesh in antibiotic solution reduce mesh infections? An experimental study

Durable and Robust Antibacterial Polypropylene Hernia Mesh for Abdominal Wall Defect Repair

Polypropylene (PP) mesh is commonly used in repairing abdominal wall hernia (AWH). However, the use of synthetic prosthesis comes with the risk of developing a prosthetic infection, resulting in delayed healing, secondary surgery, and potentially increased mortality. To address these issues, a facile surface functionalization strategy for PP mesh based on phytic acid (PA) and polyhexamethylene guanidine (PHMG) was constructed through a one-step co-deposition process, referred to as the PA/PHMG coating. The development of PA/PHMG coating is mainly attributed to the surface affinity of PA and the electrostatic interactions between PA and PHMG. The PA/PHMG coating could be completed within 4 h under mild conditions. The prepared PA/PHMG coatings on PP mesh surfaces exhibited desirable biocompatibility toward mammalian cells and excellent antibacterial properties against the notorious "superbug" methicillin-resistant Staphylococcus aureus (MRSA) and tetracycline-resistant Escherichia coli (TRE). The PA/PHMG-coated PP meshes showed killing ratios of over 99% against MRSA in an infected abdominal wall hernia repair model. Furthermore, histological and immunohistochemical analysis revealed a significantly attenuated degree of neutrophil infiltration in the PA/PHMG coating group, attributed to the decreased bacterial numbers alleviating the inflammatory response at the implant sites. Meanwhile, the pristine PP and PA/PHMG-coated meshes showed effective tissue repair, with the PA/PHMG coating group exhibiting enhanced angiogenesis compared with pristine PP meshes, suggesting superior tissue restoration. Additionally, PP meshes with the highest PHMG weight ratio (PA/PHMG(3)) exhibited excellent long-term robustness under phosphate-buffered saline (PBS) immersion with a killing ratio against MRSA still exceeding 95% after 60 days of PBS immersion. The present work provides a facile and promising approach for developing antibacterial implants.

pH-Responsive antibacterial metal-phenolic network coating on hernia meshes

Polypropylene (PP) mesh is widely used in hernioplasty, but it is prone to contamination by pathogenic bacteria. Here, we present an infection microenvironment-responsive metal-phenolic network (MPN) coating, which is made up of Cu2+ and tannic acid (TA) (referred to as CT coating), and is fabricated on PP meshes by layer-by-layer (LbL) assembly. The CT coating provided a robust protection for the PP mesh from pathogenic bacterial infection in a pH-responsive manner due to the pH-responsive disassembly kinetics of MPN complexes. Moreover, the PP meshes with ten CT coating cycles (PP-CT(10)) exhibited excellent stability in a physiological environment, with the killing ratio against "superbug" methicillin-resistant Staphylococcus aureus (MRSA) at pH 5.5 exceeding 99% even after 28 days of PBS (pH 7.4) immersion. In addition, the PP-CT(10) exhibited excellent in vivo anti-infective ability in a rodent subcutaneous implant MRSA infection model, and the results of histological and immunohistochemical analyses demonstrated that the reduced bacterial number alleviated the inflammatory response at implant sites. This study revealed that MPN coating is a promising strategy, which could provide a self-defensive ability for various implants to combat post-surgical infections in a pH-responsive manner.

Hernia Mesh Complications: Management of Mesh Infections and Enteroprosthetic Fistula

The potential consequences of mesh infection mandate careful consideration of surgical approach, mesh selection, and preoperative patient optimization when planning for ventral hernia repair. Intraperitoneal mesh, microporous or laminar mesh, and multifilament mesh typically require explantation, whereas macroporous, monofilament mesh in an extraperitoneal position is often salvageable. Delayed presentation of mesh infection should raise the suspicion for enteroprosthetic fistula when intraperitoneal mesh is present. When mesh excision is necessary, the surgeon must carefully consider both the risk of recurrent infection as well as hernia recurrence when deciding on single-stage definitive reconstruction versus primary closure with delayed reconstruction.

Microbiology of chronic mesh infection

PURPOSE

Mesh infection following hernia repair is one of the most dreaded complications of hernia surgery. Mesh sinus, infected seromas, mesh extrusion, and mesh-related enteric fistulas are common complications associated with synthetic mesh. This study aimed to review the microbiota of mesh infection in 100 patients submitted to mesh explantation.

METHODS

We reviewed the charts of patients presenting with a history of mesh infection lasting or arising six months or more after mesh placement. All patients who submitted to abdominal wall repair with complete removal of an infected mesh and presenting a positive culture were included. The microbiology analysis was based on positive cultures obtained from the fluids and tissues surrounding the mesh or positive cultures of the mesh. Microorganisms were divided into gram-positive or gram-negative, aerobic or anaerobic, and fungi.

RESULTS

Pure aerobic gram-positive cultures were encountered in 50% of the patients, followed by a combination of aerobic gram-positive/gram-negative (8%) and pure gram-negative cultures (6%). Anaerobes were recovered from 31% of patients. Fungi were recovered from 6%. Staphylococcus aureus was identified in 64% of cultures, with methicillin-resistant Staphylococcus aureus present in 42% and methicillin-sensitive Staphylococcus aureus in 22%. Among aerobic gram-negative infections, six (17%) were caused by multi-resistant bacteria, including Pseudomonas aeruginosa, Proteus mirabilis, Acinetobacter baumanii, Klebsiella pneumoniae complex, and Enterobacter cloacae complex.

CONCLUSION

Staphylococcus aureus plays a significant role in the pathogenesis of synthetic mesh infection. Staphylococcus aureus, isolated in 64% of cultures, accounted for most single bacterial infections and was the prevalent germ in mesh sinus and infected seromas. Gram-negative infection occurred in 35%. Anaerobes occurred in 31%, commonly encountered in polymicrobial infections. Most fungi cultures happened in patients with enteric fistulas.

The European Hernia Society Prehabilitation Project: A Systematic Review of Intra-Operative Prevention Strategies for Surgical Site Occurrences in Ventral Hernia Surgery

Background

Ventral hernia repair is one of the most commonly performed surgical procedures worldwide. To reduce the risk of complications, pre- and intra-operative strategies have received increasing focus in recent years. To assess possible preventive surgical strategies, this European Hernia Society endorsed project was launched. The aim of this review was to evaluate the current literature focusing on pre- and intra-operative strategies for surgical site occurrences (SSO) and specifically surgical site infection (SSI) in ventral hernia repair.

Methods

A systematic review was conducted and reported in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Databases used were Pubmed and Web of Science. Original retrospective or prospective human adult studies describing at least one intra-operative intervention to reduce SSO after ventral hernia repair were considered eligible.

Results

From a total of 4775 results, a total of 18 papers were considered suitable after full text reading. Prehospital chlorhexidine gluconate (CHG) scrub appears to increase the risk of SSO in patients undergoing ventral hernia repair, while there is no association between any type of surgical hat worn and the incidence of postoperative wound events. Intraoperative measures as prophylactic negative pressure therapy, surgical drain placement and the use of quilt sutures seem beneficial for decreasing the incidence of SSO and/or SSI. No positive effect has been shown for antibiotic soaking of a synthetic mesh, nor for the use of fibrin sealants.

Conclusion

This review identified a limited amount of literature describing specific preventive measures and techniques during ventral hernia repair. An advantage of prophylactic negative pressure therapy in prevention of SSI was observed, but different tools to decrease SSIs and SSOs continuously further need our full attention to improve patient outcomes and to lower overall costs.

Synthetic Mesh in Contaminated Abdominal Wall Surgery: Friend or Foe? A Literature Review

INTRODUCTION

The use of synthetic mesh in contaminated fields is controversial. In the last decade, published data have grown in this matter suggesting favorable outcomes. However, multiple variables and scenarios that influence the results still make difficult to obtain convincing recommendations.

METHODS

We performed a review of relevant available data in English regarding the use of synthetic meshes in contaminated abdominal wall surgery using the Medline database. Articles including patients undergoing ventral hernia in contaminated fields were included for analysis.

RESULTS

Most studies support the use of synthetic meshes for ventral hernia repair in contaminated fields, as they have shown lower recurrence rate and similar wound morbidity. Although no mesh seems ideal in this setting, most surgeons advocate for the use of reduced-in-weight polypropylene mesh. Sublay location of the prosthesis associated with complete fascial closure appears to offer better results in these patients. In addition, current evidence suggests that the use of prophylactic synthetic mesh when performing a stoma or for stoma reversal incisional hernias might be beneficial.

CONCLUSION

A better understanding of surgical site occurrences and its prevention, as well as the introduction of new reduced-in-weight meshes have allowed using synthetic meshes in a contaminated field. Although the use of mesh has indeed shown promising results in these patients, the surgical team should still balance pros and cons at the time of placing synthetics in contaminated fields.

Prosthetic meshes for hernia repair: State of art, classification, biomaterials, antimicrobial approaches, and fabrication methods

Worldwide, hernia repair represents one of the most frequent surgical procedures encompassing a global market valued at several billion dollars. This type of surgery usually requires the implantation of a mesh that needs the appropriate chemical, physical and biological properties for the type of repair. This review thus presents a description of the types of hernias, current hernia repair methods, and the state of the art of prosthetic meshes for hernia repair providing the most important meshes used in clinical practice by surgeons working in this area classified according to their biological or chemical nature, morphology and whether bioabsorbable or not. We emphasise the importance of surgical site infection in herniatology, how to deal with this microbial problem, and we go further into the future research lines on the production of advanced antimicrobial meshes to improve hernia repair and prevent microbial infections, including multidrug-resistant strains. A great deal of progress has been made in this biomedical field in the last decade. However, we are still far from an ideal antimicrobial mesh that can also provide excellent integration to the abdominal wall, mechanical performance, low visceral adhesion and minimal inflammatory or foreign body reactions, among many other problems.

The Use of Interlocking Polyetheretherketone (PEEK) Patient-Specific Facial Implants in the Treatment of Facial Deformities. A Retrospective Review of Ten Patients

PURPOSE

Polyetheretherketone (PEEK) is a versatile biocompatible material with a wide variety of clinical applications. Multiple-piece 3-dimensionally milled interlocking PEEK patient-specific implants are used in cases with restricted access or around vital structures. The interlocking joints reduce the number of fixation screws required by converting the multiple segments into 1 single implant. Stability of such joints is of paramount importance to prevent complications such as infection and implant extrusion. This retrospective study evaluates the clinical outcomes in the use of multiple-piece 3-dimensionally milled interlocking PEEK patient-specific implants as a treatment for various congenital and acquired facial deformities.

METHODS

Patients' records and clinical interviews were retrospectively reviewed.

RESULTS

A total of 10 patients were included; 6 of them (60%) were men. A planning cone beam scan (90%) or computed tomography scan (10%) were obtained following a standard protocol. All treatments were performed by a single surgeon, following a standardized approach. The follow-up time ranged from 11 to 61 months (mean = 37.1 months). No implant exposure, extrusion or removal were reported. Three patients (30%) experienced complications. Recurrent edema was observed in 1 patient (10%), another patient (10%) experienced bilateral mental nerve paresthesia, and the third patient (10%) had recurrent sinusitis, which was successfully treated with functional endoscopic sinus surgery without removing the implant.

CONCLUSION

Within the limitation of this study, 3-dimensionally milled interlocking PEEK patient-specific implants are safe, predictable, potentially save operative time, and readily adjustable. Extra stability and antislippage mechanism can be achieved by using the interlocking joint. Further studies on a larger cohort of patients is needed to confirm these results.

Durable and Effective Antibacterial Cotton Fabric Collaborated with Polypropylene Tissue Mesh for Abdominal Wall Defect Repair

A feasible, efficient antibacterial and anti-infective mesh for clinical abdominal wall defect repair is significant, but challenging due to the complexity of the postoperative wound environment. Herein, a simple strategy was provided to construct woven cotton fabric modified with gentamicin (Gem) via the enamine bonds. The obtained cotton fabric possessed favorable antibacterial properties against E. coli and S. aureus with the bactericidal rate of over 99.99% and could be combined with a commercial polypropylene (PP) mesh to serve as a two-layer composite mesh for abdominal wall defect repair. The antibacterial cotton layer was systematically characterized by FTIR, XPS, SEM, EDS, and mechanical measurements. The C2C12 cells and human fibroblasts were employed to assess the cytocompatibility of the composite mesh in vitro. Furthermore, the rat abdominal wall defect model was used to evaluate the efficacy of antibacterial and anti-infection properties. It was demonstrated that the two-layer composite mesh possessed favorable biocompatibility and satisfactory anti-infection properties involved in abdominal wall defect repair. Therefore, this synergetic two-layer composite mesh would out-perform surgical PP meshes in preventing infectious complications.

Contamination of hybrid hernia meshes compared to bioresorbable Phasix™ Mesh in a rabbit subcutaneous implant inoculation model

Background

Hybrid hernia meshes combine biological tissue-derived extracellular matrix with permanent or resorbable synthetic. The objective of this study was to evaluate hybrid meshes (Gore® Synecor, Zenapro™, Ovitex™ 1S Reinforced Bioscaffold Permanent, and Ovitex™ 1S Reinforced Bioscaffold Resorbable) compared to non-hybrid, bioresorbable synthetic mesh (Phasix™ Mesh) in a rabbit bacterial inoculation model.

Materials and methods

Subcutaneous pockets were bilaterally created in male, New Zealand White rabbits (n = 25). Circular meshes (3.8 cm diameter) were implanted and inoculated with 1 × 10⁶ colony forming units (CFU) of clinically-isolated methicillin-resistant Staphylococcus aureus (MRSA). A given animal received a single mesh type. Seven days post-inoculation, animals were euthanized and white material and microbial colonization were assessed by abscess scoring and CFU quantification, respectively. Non-parametric Kruskal-Wallis with Dunn's post-hoc tests compared results for different meshes.

Results

Phasix™ Mesh and Synecor exhibited significantly lower abscess scores than Zenapro™, Ovitex™ 1S Permanent, and Ovitex™ 1S Resorbable (p < 0.05). All pocket swabs for Zenapro™ and Ovitex™ meshes were positive for MRSA (100%), with 20% of Synecor and 0% Phasix™ Mesh. Microbial colonization was significantly lower for Phasix™ Mesh (0 CFU) relative to Zenapro™ (6.73 × 10⁷ CFU (median)), Ovitex™ 1S Permanent (7.87 × 10⁷ CFU) and Ovitex™ 1S Resorbable (1.45 × 10⁸ CFU), and for Synecor (0 CFU) relative to both Ovitex™ meshes. Phasix™ Mesh was the only device with no detectable abscess or microbial colonization.

Conclusion

Phasix™ Mesh demonstrated no detectable abscess or microbial colonization at 7-days post-implantation and inoculation, in contrast with four hybrid meshes, which all demonstrated colonization in a rabbit bacterial inoculation model.

Mesh implants for hernia repair: an update

INTRODUCTION

Today the use of textile meshes has become a standard for the treatment of abdominal wall hernias and for the reinforcement of any tissue repair as the strength of the implant decreases the recurrence rates. With increasing use, side effects of the textile implants became apparent, as well.

AREAS COVERED

Based on publications in Medline over the past decade, general and specific benefits, as well as risks, are discussed with the challenge to define individual risk-benefit ratios. For meshes, certain high-risk or low-risk conditions can be defined. In an attempt to eliminate mesh-related risks, quality control for medical devices has meanwhile been revised. In both the USA and the EU post-market surveillance studies are required to keep medical devices approved.

EXPERT COMMENTARY

The impact of material on the complication rate will vary depending on the patient's co-morbidity or the risks of the procedure. Even the best material can end up with disappointing results in case of poor healing or poor surgery. On the other hand, when using high-risk devices, most of the complications after excellent surgery with excellent indication can be supposed to be mesh-related. Thus, the use of low-risk devices is recommended even though its advantage may not be demonstrable in clinical studies.

Surgical site infection: the "Achilles Heel" of all types of abdominal wall hernia reconstruction

PURPOSE

Surgical site infection is the most common hospital-acquired infection in surgical patients. Recently, public health organizations have updated prevention guidelines. This review discusses surgical site infections as a complication of abdominal wall reconstruction.

METHODS

The authors reviewed guidelines on prevention of surgical site infections from the Center for Disease Control and Prevention, World Health Organization, and National Institute for Health and Care Excellence and put them into context with the relevant abdominal wall reconstruction literature. This was the subject of the Nyhus-Wantz lecture given at The International Hernia Congress on March 14, 2018 in Miami, FL and is summarized here.

RESULTS

Routine use of preoperative antibiotics in prosthetic groin hernia repair is not supported by the available literature. High-quality data on antibiotic prophylaxis in ventral (both primary and incisional) hernia repair is lacking, but it is widely utilized and may reduce SSIs. Recommended preventative strategies discussed in this manuscript include: treatment of remote site infections, perioperative normothermia and normoglycemia, avoidance of hypoxemia, antiseptic preparation of surgical team hands and patient skin, treatment of obesity, smoking cessation, correction of malnutrition, and physical conditioning.

CONCLUSION

Surgical site infections lead to significant morbidity and mortality, hernia recurrences, prolonged hospital stay, and increased hospital costs. This makes surgical site infections the "Achilles Heel" of abdominal wall reconstruction. Strict adherence to standardized guidelines and preoperative optimization of patients' risk profiles are crucial to decrease the incidence of surgical site infections.

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.

Antibiotic Irrigation of the Surgical Site Decreases Incidence of Surgical Site Infection after Open Ventral Hernia Repair

Surgical site infections (SSI) are common complications after open ventral hernia repair (OVHR), potentially requiring further intervention. Antibiotic lavage before abdominal closure has been shown to lower the incidence in intra-abdominal and soft tissue SSI. A retrospective review of OVHR was performed with mesh at Greenville Health System Hernia Center between 2008 and 2017. Patients were divided into three groups, receiving no antibiotic irrigation (Grp 1, n = 260), gentamicin alone (Grp 2, n = 263), or gentamicin 1 clindamycin (G 1 C) irrigation (Grp 3, n = 299). Differences in categorical variables among the three groups were tested using chi-squared or Fischer's exact test (for n < 5). Analysis of continuous variables was performed using analysis of variance or Kruskal-Wallis test for differences in length of stay. Logistic regression was performed using all clinically relevant variables to determine the effects of irrigation on SSI. Incidence of surgical site occurrence was significantly lower after G 1 C irrigation (Grp 1, 28.1%; Grp 2, 35.4%; Grp 3, 19.7%; P < 0.001). Incidence of SSI was significantly lower after G 1 C irrigation, but not G alone (Grp 1, 16.5%; Grp 2, 15.2%; and Grp 3, 5.4%; P < 0.001). Multivariate logistic regression demonstrated significantly increased SSI with contaminated wounds (OR 2.96; 95% confidence interval (CI) 1.39–6.21), dirty wounds (OR 3.84; 95% CI 1.49–9.69), and chronic obstructive pulmonary disease (OR 3.70; 95% CI 2.16–6.38), as expected. Use of G 1 C was an independent predictor of decreased SSI (OR 0.33; 95% CI 0.16–0.67). Irrigation with a combined G 1 C antibiotic irrigation significantly reduces the incidence of surgical site infection after OVHR with mesh.

Determination of Proper Timing for the Placement of Intra-Abdominal Mesh after Incidental Enterotomy in a Rodent Model (Rattus norvegicus)

Controversy exists regarding the appropriate timing for placement of permanent intra-abdominal mesh after inadvertent enterotomy during elective hernia repair. The aim of this study was to examine mesh placement at variable postoperative periods and the subsequent risk of infection. Fifty rodents were divided into five groups. Groups one to four underwent laparotomy, enterotomy, and repair. Physiomesh® was placed at the index operation one, three, or seven days postoperatively in Groups 1,2,3, and 4. Group 5 underwent mesh placement only. Necropsy with mesh harvest was performed seven days after placement. Cultures of mesh were obtained and Fisher's exact test was used to compare groups. Bacterial growth postsonication was identified in 30,30, 50, and 90 per cent versus 20 per cent in controls. Compared with controls, there was significantly increased risk of mesh infection when it was placed seven days after enterotomy ( P = 0.006). There was no significant difference in bacterial growth when mesh was placed at the time of enterotomy, one or three days later. The risk of bacterial contamination of permanent mesh placed immediately after inadvertent enterotomy during elective hernia repair is as safe as placing mesh at one or three days. Placing mesh at seven days significantly increased the risk of mesh contamination.

Infections associated with mesh repairs of abdominal wall hernias: Are antimicrobial biomaterials the longed-for solution?

The incidence of mesh-related infection after abdominal wall hernia repair is low, generally between 1 and 4%; however, worldwide, this corresponds to tens of thousands of difficult cases to treat annually. Adopting best practices in prevention is one of the keys to reduce the incidence of mesh-related infection. Once the infection is established, however, only a limited number of options are available that provides an efficient and successful treatment outcome. Over the past few years, there has been a tremendous amount of research dedicated to the functionalization of prosthetic meshes with antimicrobial properties, with some receiving regulatory approval and are currently available for clinical use. In this context, it is important to review the clinical importance of mesh infection, its risk factors, prophylaxis and pathogenicity. In addition, we give an overview of the main functionalization approaches that have been applied on meshes to confer anti-bacterial protection, the respective benefits and limitations, and finally some relevant future directions.

Characterization of host response, resorption, and strength properties, and performance in the presence of bacteria for fully absorbable biomaterials for soft tissue repair

PURPOSE

The objective was to evaluate the host response, resorption, and strength properties, and to assess the performance in the presence of bacteria for Phasix™ Mesh (Phasix™) and Gore® Bio-A® Tissue Reinforcement (Bio-A®) in preclinical models.

METHODS

In a rat model, one mesh (2 × 2 cm) was implanted subcutaneously in n = 60 rats. Animals were euthanized after 2, 4, 8, 12, 16, or 24 weeks (n = 5/mesh/time point), and implant sites were assessed for host inflammatory response and overall fibrotic repair thickness. In a rabbit model, meshes (3.8 cm diameter) were bilaterally implanted in subcutaneous pockets in n = 20 rabbits (n = 10 rabbits/mesh) and inoculated with 108 CFU clinically isolated methicillin-resistant Staphylococcus aureus (MRSA). One mesh type was implanted per animal. Animals were euthanized after 7 days, and implants were assessed for abscess formation, bacterial colonization, and mechanical strength.

RESULTS

In the rat study, Phasix™ and Bio-A® exhibited similar biocompatibility, although Bio-A® demonstrated a significantly greater inflammatory response at 4 weeks compared to Phasix™ (p < 0.01). Morphometric analysis demonstrated rapid resorption of Bio-A® implants with initially thicker repair sites at 2, 4, 8, and 12 weeks (p < 0.0001), which transitioned to significantly thinner sites compared to Phasix™ at 16 and 24 weeks (p < 0.0001). In the rabbit bacterial inoculation study, Phasix™ exhibited significantly lower abscess score (p < 0.001) and bacterial colonization (p < 0.01), with significantly greater mechanical strength than Bio-A® (p < 0.001).

CONCLUSIONS

Host response, resorption, repair thickness, strength, and bacterial colonization suggest a more stable and favorable outcome for monofilament, macroporous devices such as Phasix™ relative to multifilament, microporous devices such as Bio-A® over time.

Outcomes of Posterior Component Separation With Transversus Abdominis Muscle Release and Synthetic Mesh Sublay Reinforcement

OBJECTIVE

To evaluate the safety and efficacy of transversus abdominis muscle release (TAR) with retrorectus synthetic mesh reinforcement in a large series of complex hernia patients.

BACKGROUND

Posterior component separation via TAR during abdominal wall reconstruction (AWR) continues to gain popularity. Although our early experience with TAR has been promising, long-term outcomes have not been reported.

METHODS

From December 2006 to December 2014, consecutive patients undergoing open AWR utilizing TAR were identified in our prospectively maintained database and reviewed retrospectively. Main outcome measures included demographics, perioperative details, wound complications, and recurrences.

RESULTS

During the study period, 428 consecutive TAR procedures were analyzed. Mean age was 58, with mean body mass index 34.4 kg/m (range 20-65). Major comorbidities included diabetes (21%), chronic obstructive pulmonary disease (12%), and immunosuppression (3%). Mean hernia defect area was 606 cm (range 180-1280) and average mesh size was 1220 cm (range 600-4500). The majority of cases (66%) were clean, 26% were clean-contaminated, and 8% were contaminated. Eighty (18.7%) surgical-site events occurred, of which 39 (9.1%) were surgical-site infections. Three patients required mesh debridement; however, no instances of mesh explantation occurred. Of the 347 (81%) patients with at least 1-year follow-up (mean 31.5 mo), there were 13 (3.7%) recurrences.

CONCLUSIONS

Complex AWR represents a formidable surgical challenge. In this large series, we demonstrated that posterior component separation via TAR with wide synthetic mesh sublay provides a very durable repair with low morbidity, even in comorbid patients with large defects. We strongly advocate TAR as a robust addition to the armamentarium of reconstructive surgeons.

Evidence-Based Strategies to Reduce Postoperative Complications in Plastic Surgery

Reconstructive plastic surgery is vital in assisting patients with reintegration into society after events such as tumor extirpation, trauma, or infection have left them with a deficit of normal tissue. Apart from performing a technically sound operation, the plastic surgeon must stack the odds in the favor of the patient by optimizing them before and after surgery. The surgeon must look beyond the wound, at the entire patient, and apply fundamental principles of patient optimization. This article reviews the evidence behind the principles of patient optimization that are commonly used in reconstructive surgery patients.

Design Strategies and Applications of Biomaterials and Devices for Hernia Repair

Hernia repair is one of the most commonly performed surgical procedures worldwide, with a multi-billion dollar global market. Implant design remains a critical challenge for the successful repair and prevention of recurrent hernias, and despite significant progress, there is no ideal mesh for every surgery. This review summarizes the evolution of prostheses design toward successful hernia repair beginning with a description of the anatomy of the disease and the classifications of hernias. Next, the major milestones in implant design are discussed. Commonly encountered complications and strategies to minimize these adverse effects are described, followed by a thorough description of the implant characteristics necessary for successful repair. Finally, available implants are categorized and their advantages and limitations elucidated, including non-absorbable and absorbable (synthetic and biologically derived) prostheses, composite prostheses, and coated prostheses. This review not only summarizes the state of the art in hernia repair, but also suggests future research directions toward improved hernia repair utilizing novel materials and fabrication methods.

Development of a novel murine model for treatment of infected mesh scenarios

BACKGROUND

Indications regarding hernia repair after removal of previously infected prostheses remain unclear. Patients may receive staged primary repair or single-stage reconstructions, neither of which may be ideal. Although animal models have simulated contamination by direct inoculation of implants with bacteria, there remains a paucity of literature, which simulates a field following mesh infection and removal. We aimed to develop a murine model to mimic this complex scenario to allow for further testing of various implants.

METHODS

Thirty-six female CL57BL/6J mice underwent implantation of a 0.7 × 0.7 cm polyester mesh in the dorsal subcutaneous position. Wounds were closed and inoculated with 100 µL containing 1 × 10⁴ CFU of GFP-labeled MSSA. After 2 weeks, the infected mesh was removed and the cavity was copiously irrigated with saline. Mice were split into four groups: with three groups receiving new polyester, polypropylene, and porcine mesh and remaining as non-mesh controls. Mice were survived for another 2 weeks and underwent necropsy. Gross infection was evaluated at 2 and 4 weeks. Tissue homogenization and direct plating to recover GFP MSSA was completed at 4 weeks.

RESULTS

At 2 weeks, all mice were noted to have gross mesh infection. One animal died due to overwhelming infection and wound breakdown. At 4 weeks, 5/6 (83 %) control mice who did not have a second mesh implantation had full clearance of their wounds. In contrast, 9/10 (90 %) mice with re-implantation of polypropylene were noted to have pus and recovery of GFP MSSA on plating. This was also observed in 100 % of mice with polyester and porcine mesh.

CONCLUSION

Our novel murine model demonstrates that mesh re-implantation after infected mesh removal results in infection of the newly placed prosthesis, regardless of the material characteristic or type. This model lays foundation for development and investigation of implants for treatment strategies following infected mesh removal.

Tissue reaction to urogynecologic meshes: effect of steroid soaking in two different mesh models

INTRODUCTION AND HYPOTHESIS

Steroid soaking may decrease mesh-triggered inflammatory reaction in tissue. We aimed to investigate the tissue reaction to a steroid-soaked mesh material and an unsoaked mesh material in the rat model.

METHODS

Neutral and steroid-soaked type I macroporous polypropylene (PP) monofilament and polyvinylidene fluoride (PVF) mesh materials were implanted on the rectus abdominis muscle of 20 mature Wistar albino rats. Animals were divided into four groups: PP mesh with steroid (PP-S), PP mesh without steroid, PVF mesh with steroid (PVF-S), and PVF mesh without steroid. The rats were killed after 12 weeks, and histologic, immunohistochemical and electron microscopic examinations were performed. For immunohistochemical analysis, polyclonal rabbit anti-mouse CD3, rabbit anti-mouse CD68, rabbit anti-mouse CD15, and rabbit anti-mouse CD34 antibodies were used for the detection of lymphocytes, macrophages, polymorphonuclear leukocyte foreign body giant cells, and fibromyocyte stem cells, respectively. Samples were stained with hematoxylin and eosin for the histologic evaluation of inflammation and with Masson's trichrome stain for the evaluation of collagen deposition. Pore size and mesh ultrastructure were evaluated by electron microscopy.

RESULTS

Expression of CD3 was lower in the PVF, PVF-S and PP-S groups, and expression of CD34 was higher in the PVF-S and PP-S groups than in the PP groups (p < 0.05). Collagen deposition was lower in the PVF, PVF-S and PP-S groups (p < 0.05). Histologically, the intensity of inflammation was lower in the PVF-S and PP-S groups than in the PP mesh group (p < 0.05). There were no significant differences among the groups in terms of pore size and mesh ultrastructure on electron microscopic examination (p > 0.05).

CONCLUSIONS

PVF mesh induces less inflammation than PP mesh, and in both mesh types steroid soaking further decreases inflammation without changing the pore size.

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.

An in vivo analysis of Miromesh--a novel porcine liver prosthetic created by perfusion decellularization

BACKGROUND

Bioprosthetics derived from human or porcine dermis and intestinal submucosa have dense, homogenous, aporous collagen structures that potentially limit cellular penetration, undermining the theoretical benefit of a "natural" collagen scaffold. We hypothesized that Miromesh-a novel prosthetic derived from porcine liver by perfusion decellularization-provides a more optimal matrix for tissue ingrowth.

METHODS

Thirty rats underwent survival surgery that constituted the creation of a 4 × 1 cm abdominal defect and simultaneous bridged repair. Twenty rats were bridged with Miromesh, and 10 rats were bridged with non-cross-linked porcine dermis (Strattice). Ten Miromesh and all 10 Strattice were rinsed in vancomycin solution and inoculated with 10(4) colony-forming units of green fluorescent protein-labeled Staphylococcus aureus (GFP-SA) after implantation. Ten Miromesh controls were neither soaked nor inoculated. No animals received systemic antibiotics. All animals were euthanized at 90 d and underwent an examination of their gross appearance before being sectioned for quantitative bacterial culture and histologic grading. A pathologist scored specimens (0-4) for cellular infiltration, acute inflammation, chronic inflammation, granulation tissue, foreign body reaction, and fibrous capsule formation.

RESULTS

All but one rat repaired with Strattice survived until the 90-d euthanization. All quantitative bacterial cultures for inoculated specimens were negative for GFP-SA. Of nine Strattice explants, none received a cellular infiltration score >0, consistent with a poor tissue-mesh interface observed grossly. Of 10 Miromesh explants also inoculated with GFP-SA, seven of 10 demonstrated cellular infiltration with an average score of +2.7 ± 0.8, whereas sterile Miromesh implants received an average score of 0.8 ± 1.0. Two inoculated Miromesh implants demonstrated acute inflammation and infection on histology.

CONCLUSIONS

A prosthetic generated from porcine liver by perfusion decellularization provides a matrix for superior cellular infiltration compared with non-cross-linked porcine dermis.

The Effect of the Use of Synthetic Mesh Soaked in Antibiotic Solution on the Rate of Graft Infection in Ventral Hernias: A Prospective Randomized Study

Wound infections and seroma formations are important problems in ventral hernia repair operations using synthetic mesh grafts. The aim of this study was to investigate the effect of the use of synthetic mesh soaked in vancomycin solution on the rate of graft infection. The total number of subjects was 52. The subjects were randomized into 2 groups using a software program. Group 1 (n = 26) was the control group. In group 2 (n = 26), synthetic mesh was soaked in a Vancomycin solution before it was implanted. The patients were compared with respect to demographic characteristics and preoperative, intraoperative, and postoperative variables. There were no significant differences between the groups with respect to the available variables. Seroma development was significantly more common in group 2 (P < 0.041). Three patients (5.7%) developed superficial wound infection, and 9 (17%) developed surgical site infection 2-type wound-site infection. No significant difference was found between the groups in terms of infection. The use of synthetic mesh soaked in vancomycin solution had no beneficial effects on the rate of wound-site infection. Future randomized, controlled, large-scale studies using the same mesh and suture types, and meshes soaked in larger spectrum antibiotics are needed.

Inhibition of Staphylococcus aureus Adhesion to the Surface of a Reticular Heavyweight Polypropylene Mesh Soaked in a Combination of Chlorhexidine and Allicin: An In vitro Study

INTRODUCTION

Presoaking meshes for hernia repair with antiseptics prior to implantation could decrease the adhesion of microorganisms to the material surface and reduce the risk of antibiotic resistances. In this work, we evaluate chlorhexidine and allicin (natural antiseptic not yet tested for these purposes) against vancomycin as antiseptics to be used in the pretreatment of a heavyweight polypropylene mesh using an in vitro model of bacterial contamination.

METHODS

Solutions of saline, vancomycin (40 µg/mL), allicin (1,000 µg/mL), chlorhexidine (2%-0.05%) and the combination allicin-chlorhexidine (900 µg/mL-0.05%) were analyzed with agar diffusion tests in the presence of 106 CFU Staphylococcus aureus ATCC25923. Additionally, sterile fragments of Surgipro (1 cm2) were soaked with the solutions and cultured onto contaminated agar plates for 24/48/72 h. The antimicrobial material DualMesh Plus was utilized as positive control. At every time, the inhibition zones were measured and the bacterial adhesion to the mesh surface quantified (sonication, scanning electron microscopy). Cytotoxicity of the treatments was examined (alamarBlue) using rabbit skin fibroblasts.

RESULTS

The largest zones of inhibition were created by allicin-chlorhexidine. Chlorhexidine was more effective than vancomycin, and allicin lost its effectiveness after 24 h. No bacteria adhered to the surface of the DualMesh Plus or the meshes soaked with vancomycin, chlorhexidine and allicin-chlorhexidine. On the contrary, saline and allicin allowed adherence of high loads of bacteria. Vancomycin had no toxic effects on fibroblasts, while allicin and chlorhexidine exerted high toxicity. Cytotoxicity was significantly reduced with the allicin-chlorhexidine combination.

CONCLUSIONS

The use of antiseptics such as chlorhexidine, alone or combined with others like allicin, could represent an adequate prophylactic strategy to be used for hernia repair materials because soaking with these agents provides the mesh with similar antibacterial properties to those observed after soaking with vancomycin, similar to the effect of DualMesh Plus.

Gentamicin for prevention of intraoperative mesh contamination: demonstration of high bactericide effect (in vitro) and low systemic bioavailability (in vivo)

INTRODUCTION

Mesh infection is a severe complication after incisional hernia repair and occurs in 1-3 % of all open mesh implantations. For this reason, topical antimicrobial agent applied directly to the mesh is often used procedure. So far, however, this procedure lacks a scientific basis.

MATERIALS AND METHODS

Two different meshes (Parietex™, Covidien; Ultrapro™, Ethicon Johnson & Johnson) were incubated with increasing amounts of three different Staphylococcus aureus strains (ATCC 25923; Mu50; ST239) with or without gentamicin and growth ability were determined in vitro. To further address the question of the systemic impact of topic gentamicin, serum levels were analyzed 6 and 24 h after implantation of gentamicin-impregnated multifilament meshes in 19 patients.

RESULTS

None of the gentamicin-impregnated meshes showed any bacterial growth in vitro. This effect was independent of the mesh type for all the tested S. aureus strains. In the clinical setting, serum gentamicin levels 6 h after implantation of the gentamicin-impregnated meshes were below the through-level (range 0.4-2.9 mg/l, mean 1.2 ± 0.7 mg/l). After 24 h the gentamicin serum levels in all patients had declined 90-65 % of the 6 h values.

CONCLUSION

Local application of gentamicin to meshes can completely prevent the growth of even gentamicin-resistant S. aureus strains in vitro. The systemic relevance of gentamicin in the clinical controls showed to be very low, without reaching therapeutic concentrations.

Bacteria in hernia sac: an important risk fact for surgical site infection after incarcerated hernia repair

BACKGROUND

Although some recent reports have proven that incarcerated and/or strangulated hernia is not contraindication to mesh repair, there is still a common concern owing to increased rate of postoperative surgical site infection (SSI). The aim of this clinical study was to evaluate factors that increase the risk of SSI after incarcerated hernia repair, and to identify the pathogens related to SSI.

METHODS

A retrospective analysis was performed on data collected prospectively over a 4-year interval from January 2007 to December 2011. A total of 121 patients who underwent emergency surgery for incarcerated hernias were analyzed.

RESULTS

107 hernias were repaired using mesh versus 14 primary suture repairs. SSIs were observed in 9 of the 121 patients. Of 15 preoperative and intraoperative variables studied, duration of symptoms, diabetes mellitus, present of ileus, bowel resection or mesh repair performed, bacteria present in hernia sac and cloudy fluid in hernia sac were found to be significant factors predicting SSI. On multivariate analysis only bowel resection, duration of symptoms and bacteria present in hernia sac were independent variables. The most common pathogen found in hernia sac and cultured from wound drainage or swab was Escherichia coli. The strains of bacteria cultured from wound drainage or swab were same as those cultured from fluid in hernia sac in six of nine patients.

CONCLUSION

Gut-sourced E. coli is an important common organisms associated with SSI after incarcerated hernia repair. Prosthetic mesh could be used when no bowel resection is performed, duration of symptoms less than 24 h and fluid hernia sac is clear.

In vitro and in vivo characterization of a fully resorbable and composite surgical mesh

Fully resorbable and composite synthetic meshes are intended to provide advantages over nonabsorbable synthetic meshes, such as minimization of visceral adhesions and improved biocompatibility, but the inflammatory response to these materials has not previously been fully characterized. We compared resorbable and composite synthetic meshes using in vitro characterization and evaluated the host response in a nonhuman primate acute abdominal wall defect. After a 2-week in vitro incubation, resorbable synthetic mesh mechanical strength decreased to 0.12 ± 0.09 N (0.25% of initial strength), which preceded acidification and a fractured morphology at 1 month. The composite synthetic mesh strength decreased to 10.0 ± 3.2 N (41.1% of initial strength), coincident with morphological changes. In vivo, resorbable synthetic mesh elicited an intense yet transient foreign-body response, with macrophages and myofibroblasts persisting through 3 months of implantation. At 6 months, resorbable synthetic mesh was undetectable and the mesh–host tissue interface strength (14.7 ± 7.9 N) was equivalent to that of primary repair (21.4 ± 4.9 N). The composite synthetic mesh elicited a significant foreign-body response following 1 month of implantation. By 3 months, the composite synthetic mesh resorbable films had fully degraded, with foreign-body reaction localized to polypropylene fibers. By 6 months, macrophages had surrounded these polypropylene fibers, with a myofibroblast-positive capsule encircling a macrophage-rich layer. Resorbable and composite synthetic meshes may ultimately not be the most ideal biomaterials in situations where the biological response is expected to lead to a regeneration of host soft tissues.

Conservative management of an infected laparoscopic hernia mesh: A case study

INTRODUCTION

A dreaded complication of laparoscopic hernia repair is infection of the mesh. Traditionally mesh infection is managed by surgical removal of the mesh, an extensive procedure resulting in high re-herniation rates. A technique to treat such infections whilst salvaging the mesh is sorely needed. We describe a case in which a laparoscopic mesh infection was treated solely with drainage, parenteral antibiotics and antibiotic irrigation of the mesh.

PRESENTATION OF CASE

A 65 year old gentleman presented 11 months post laparoscopic repair of an inguinal hernia with malaise and an uncomfortable groin swelling. Computed tomography scanning revealed a collection surrounding the mesh which was drained and cultured to show heavy growth of Staphylococcus aureus. A pigtail drain on continuous drainage was inserted and kept in situ for 7 weeks.

The patient received one week of intravenous flucloxacillin and two gentamycin irrigations through the drain as an inpatient. He then received 6 weeks of oral flucloxacillin and bi-weekly saline flushes through the drain in the community. By 12 weeks an ultrasound scan showed resolution of the collection. At 7 months he remains clinically free from recurrence.

DISCUSSION

Here we report a novel conservative method used to treat a hernia mesh infection, preserve the mesh and avoid major surgery. Other reports exist suggesting variations in conservative methods to treat mesh infections, however ours is by far the most conservative.

CONCLUSION

Clearly, further research is required to identify which method is most effective and in which patients it is likely to be successful.