META Score: An International Consensus Scoring System on Mesh-Tissue Adhesions.

BACKGROUND: Currently, the lack of consensus on postoperative mesh-tissue adhesion scoring leads to incomparable scientific results. The aim of this study was to develop an adhesion score recognized by experts in the field of hernia surgery. METHODS: Authors of three or more previously published articles on both mesh-tissue adhesion scores and postoperative adhesions were marked as experts. They were queried on seven items using a modified Delphi method. The items concerned the utility of adhesion scoring models, the appropriateness of macroscopic and microscopic variables, the range and use of composite scores or subscores, adhesion-related complications and follow-up length. This study comprised two questionnaire-based rounds and one consensus meeting. RESULTS: The first round was completed by 23 experts (82%), the second round by 18 experts (64%). Of those 18 experts, ten were able to participate in the final consensus meeting and all approved the final proposal. From a total of 158 items, consensus was reached on 90 items. The amount of mesh surface covered with adhesions, tenacity and thickness of adhesions and organ involvement was concluded to be a minimal set of variables to be communicated separately in each future study on mesh adhesions. CONCLUSION: The MEsh Tissue Adhesion scoring system is the first consensus-based scoring system with a wide backing of renowned experts and can be used to assess mesh-related adhesions. By including this minimal set of variables in future research interstudy comparability and objectivity can be increased and eventually linked to clinically relevant outcomes.

Abdominal wall reinforcement: biologic vs. degradable synthetic devices.

BACKGROUND: New biodegradable synthetic and biologic hernia implants have been promoted for rapid integration and tissue reinforcement in challenging repairs, e.g. at the hiatus or in contaminated wound fields. Interestingly, experimental data to support or falsify this assumption is scarce. METHODS: Synthetic (BioA®) and biologic implants (porcine and bovine collagen matrices Strattice® and Veritas®) have been tested in experimental onlay hernia repair in rats in observation periods of 30 and 60 days. The key outcome parameters were mesh integration and reinforcement of the tissue at the implant site over sutured and sealed defects as well as comparison to native abdominal wall. Macroscopic assessment, biomechanical analysis and histology with haematoxylin/eosin staining, collagen staining and van Willebrand factor staining for detection of neovascularization were performed. RESULTS: BioA® was well integrated. Although the matrices were already fragmented at 60 days follow-up, hernia sites treated with synthetic scaffolds showed a significantly enhanced tissue deflection and resistance to burst force when compared to the native abdominal wall. In porcine and bovine matrices, tissue integration and shrinkage were significantly inferior to BioA®. Histology revealed a lack of fibroblast ingrowth through mesh interstices in biologic samples, whereas BioA® was tightly connected to the underlying tissue by reticular collagen fibres. CONCLUSIONS: Strattice® and Veritas® yielded reduced tissue integration and significant shrinkage, prohibiting further biomechanical tests. The synthetic BioA® provides little inherent strength but reticular collagen remodelling led to an augmentation of the scar due to significantly higher burst force resistance in comparison to native tissue.

Fabrication of silk mesh with enhanced cytocompatibility: preliminary in vitro investigation toward cell-based therapy for hernia repair.

Recent studies have demonstrated that combining cells with meshes prior to implantation successfully enhanced hernia repair. The idea is to create a biologic coating surrounding the mesh with autologous cells, before transplantation into the patient. However, due to the lack of a prompt and robust cell adhesion to the meshes, extensive in vitro cultivation is required to obtain a homogenous cell layer covering the mesh. In this context, the objective of this publication is to manufacture meshes made of silk fibres and to enhance the cytoadhesion and cytocompatibility of the biomaterial by surface immobilization of a pro-adhesive wheat germ agglutinin (lectin WGA). We first investigated the affinity between the glycoprotein WGA and cells, in solution and then after covalent immobilization of WGA on silk films. Then, we manufactured meshes made of silk fibres, tailored them with WGA grafting and finally evaluated the cytocompatibility and the inflammatory response of silk and silk-lectin meshes compared to common polypropylene mesh, using fibroblasts and peripheral blood mononuclear cells, respectively. The in vitro experiments revealed that the cytocompatibility of silk can be enhanced by surface immobilization with lectin WGA without exhibiting negative response in terms of pro-inflammatory reaction. Grafting lectin to silk meshes could bring advantages to facilitate cell-coating of meshes prior to implantation, which is an imperative prerequisite for abdominal wall tissue regeneration using cell-based therapy.

Erratum to: The impact of hydrophobic hernia mesh coating by omega fatty acid on atraumatic fibrin sealant fixation.

Erratum to: Hernia DOI 10.1007/s10029-014-1304-y. The authors would like to notify readers that unfortunately, Fig. 1 and associated captions are incorrectly published in the original publication. The correct figure and legend are given here.

The future of stem cell therapy in hernia and abdominal wall repair.

INTRODUCTION: Stem cell therapies have been proposed in preclinical trials as new treatment options in abdominal wall repair. MATERIALS AND METHODS: This work lists sources of feasible cell lines and the current status of literature and provides a cautious outlook into future developments. Special attention was paid to translational issues and practicabilty in a complex field. CONCLUSION: Cell-based therapies will play a role in the clinical setting in the future. Regulatory and ethical issues need to be addressed as well as the proof of cost-effectiveness.

The impact of hydrophobic hernia mesh coating by omega fatty acid on atraumatic fibrin sealant fixation.

BACKGROUND: Fibrin sealant (FS) is a safe and efficient fixation method in open intraperitoneal hernia repair. While favourable results have been achieved with hydrophilic meshes, hydrophobic (such as Omega fatty acid coated) meshes (OFM) have not been specifically assessed so far. Atrium C-qur lite(®) mesh was tested in rats in models of open onlay and intraperitoneal hernia repair. METHODS: 44 meshes (2 × 2 cm) were implanted in 30 male Sprague-Dawley rats in open (n = 2 meshes per animal) and intraperitoneal technique (IPOM; n = 1 mesh per animal). Animals were randomised to four groups: onlay and IPOM sutured vs. sealed. Follow-up was 6 weeks, sutured groups serving as controls. Evaluation criteria were mesh dislocation, adhesions and foreign body reaction. RESULTS: FS provided a reliable fixation in onlay technique, whereas OFM meshes dislocated in the IPOM position when sealed only. CONCLUSION: FS mesh fixation was safe with OFM meshes in open onlay repair. Intraperitoneal placement of hydrophobic meshes requires additional fixation and cannot be achieved with FS alone.

A comparison of Progrip(®) and Adhesix (®) self-adhering hernia meshes in an onlay model in the rat.

BACKGROUND: Atraumatic fixation is a key element of modern hernia repair. Two different concepts of self-adhering meshes were directly compared in this study. Adhesix(®) (AH) is coated with polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP), whereas Parietene Progrip(®) (PP) relies on the mechanical principle of micro grips made of polylactic acid (PLA). These meshes are the main competitors in the field. METHODS: AH and PP were tested in Sprague-Dawley rats at 14 and 90 days. Four groups were operated (n = 8 animals per group). Two meshes were implanted per animal in an operation model of onlay hernia repair. Dislocation, tissue integration and foreign-body reaction were evaluated. RESULTS: AH dislocated significantly more frequently (every second mesh) at both time points of observation than PP. Tissue integration was good with PP and could not be reliably assessed in AH due to frequent dislocation. Histologic examination revealed only a mild foreign body reaction in all groups. CONCLUSIONS: In our hands, PP (mechanical grip fixation) was superior to hydrogel fixation with PEG and PVP in AH in an onlay model. The reason for dislocation of AH requires further clarification as well as the impact of long-term degradation of the PLA grips.

Ultrasound biomicroscopy (UBM) and scanning acoustic microscopy (SAM) for the assessment of hernia mesh integration: a comparison to standard histology in an experimental model.

BACKGROUND: Mesh integration is a key parameter for reliable and safe hernia repair. So far, its assessment is based on histology obtained from rare second-look operations or experimental research. Therefore, non-invasive high-resolution imaging techniques would be of great value. Ultrasound biomicroscopy (UBM) and scanning acoustic microscopy (SAM) have shown potential in the imaging of hard and soft tissues. This experimental study compared the detection of mesh integration, foreign body reaction and scar formation in UBM/SAM with standard histology. MATERIALS AND METHODS: Ten titanized polypropylene meshes were implanted in rats in a model of onlay repair. 17 days postoperative animals were killed and samples were paraffin embedded for histology (H&E, Cresyl violet) or processed for postmortem UBM/SAM. The observation period was uneventful and meshes appeared well integrated. RESULTS: Relocation of neighboring cross-sectional levels could easily be achieved with the 40-MHz UBM and granulation tissue could be distinguished from adjacent muscle tissue layers. The spatial resolution of approximately 8 µm of the 200-MHz UBM system images was comparable to standard histology (2.5-5× magnification) and allowed a clear identification of mesh fibers and different tissue types, e.g., scar, fat, granulation, and muscle tissues, as well as vessels, abscedations, and foreign body giant cell clusters. CONCLUSION: This pilot study demonstrates the potential of high-frequency ultrasound to assess hernia mesh integration non-invasively. Although the methods lack cell-specific information, tissue integration could reliably be assessed. The possibility of conducting UBM in vivo advocates this method as a guidance tool for the indication of second-look operations and subsequent elaborate histological analyses.

Biologic hernia implants in experimental intraperitoneal onlay mesh plasty repair: the impact of proprietary collagen processing methods and fibrin sealant application on tissue integration.

BACKGROUND: Biologic implants have been recommended for reinforcement in routine and challenging hernia repair. However, experimental and clinical studies have reported adverse effects (e.g., slow implant integration and pronounced foreign body reaction). To evaluate the impact of different material processing methods (cross-linking vs. non-cross-linking of collagen) and implant design, four different biologic hernia implants were compared directly in experimental intraperitoneal onlay mesh plasty (IPOM). Tissue integration, shrinkage, and foreign body reaction were primary outcome parameters. METHODS: In this study, 48 Sprague-Dawley rats were randomized to four treatment groups. Open IPOM repair was performed. One peritoneal defect per animal was covered with 2 × 2 cm patches of cross-linked or non-cross-linked implants including CollaMend (n = 12), Peripatch (n = 12), Surgisis (n = 12), and Tutomesh (n = 12). In half of the animals, fibrin sealant was applied for additional fixation and to cover sutures. The observation period was 60 days. The primary outcome parameters were implant integration, shrinkage, and foreign body reaction. Macroscopic and histologic assessments were performed. RESULTS: The integration of implants was insufficient in all the groups. The implants could be detached easily from the underlying tissue, and the penetration of fibroblasts and vessels was limited to the perforations. Foreign body reaction was pronounced with CollaMend and Surgisis, leading to persistent granulomatous inflammation. Shrinkage was excessive with Surgisis, whereas Tutomesh and Peripatch yielded sufficient anti-adhesion and elicited no foreign body reaction. CONCLUSION: At 2 months, cross-linked and non-cross-linked biologic hernia implants were poorly integrated. Cross-linking led to a more pronounced foreign body reaction. Less inflammatory response may reduce local complications, but did not enhance implant integration in this study.

Comparison of three separate antiadhesive barriers for intraperitoneal onlay mesh hernia repair in an experimental model.

BACKGROUND: Adhesion formation is a common adverse effect in intraperitoneal onlay mesh (IPOM) surgery. Different methods of adhesion prevention have been developed, including coated meshes and separate antiadhesive barriers (SABs). In this study one type of mesh was tested with different SABs, which were fixed to the sutured mesh using fibrin sealant. The primary aim was to compare adhesion prevention between different SABs. Secondary aims were the assessment of tissue integration and evaluation of SAB fixation with fibrin sealant. METHODS: Thirty-two rats were randomized to one of three treatment groups (SurgiWrap, Prevadh and Seprafilm) or a control group (no SAB). Animals were operated on with an open IPOM technique (8 per group). One macroporous polypropylene mesh per animal (2 × 2 cm) was fixed with four non-absorbable sutures. An antiadhesive barrier of 2·5 × 2·5 cm was fixed with fibrin sealant. After 30 days, adhesion formation, tissue integration, seroma formation, inflammation and vascularization were evaluated macroscopically and by histology. RESULTS: Prevadh and Seprafilm groups showed a significant reduction in adhesion formation compared with the control group. Tissue integration of the mesh was reduced in these groups. Fibrin sealant fixed the SAB to the mesh securely in all groups. CONCLUSION: Prevadh and Seprafilm are potent materials for the reduction of adhesion formation. A potential relationship between effective adhesion prevention and impaired tissue integration of the implant was observed. Fibrin sealant proved an excellent agent for SAB fixation.

A comparison of a bovine albumin/glutaraldehyde glue versus fibrin sealant for hernia mesh fixation in experimental onlay and IPOM repair in rats.

BACKGROUND: Research in hernia repair has targeted new atraumatic mesh fixation to reduce major complications such as chronic pain and adhesion formation. The efficacy and safety of two surgical adhesives, viz. Artiss® (FS, fibrin sealant containing 4 IU thrombin) and Bioglue® (AGG, bovine serum albumin/glutaraldehyde glue), were evaluated in this study. Primary study endpoints were tissue integration, dislocation, and adhesion formation. Foreign-body reaction formed the secondary study endpoint. METHODS: Twenty-four polypropylene meshes (VM, Vitamesh®) were randomized to four groups (n = 6): two groups of onlay hernia repair (two meshes per animal) with mesh fixation by FS (O-FS) or by AGG (O-AGG), and two groups of IPOM repair (one mesh per animal) with mesh fixation by four sutures and FS (I-FS) or AGG (I-AGG). Eighteen rats underwent surgery. Follow-up was 30 days. Tissue integration, dislocation, seroma formation, inflammation, adhesion formation, and foreign-body reaction were assessed. RESULTS: Meshes fixed with FS (O-FS, I-FS) showed good tissue integration. No dislocation, seroma formation, or macroscopic signs of inflammation were detectable. Adhesion formation of I-FS was significantly milder compared with I-AGG (P = 0.024). A moderate foreign-body reaction without active inflammation was seen histologically in O-FS and I-FS groups. Samples fixed with AGG (O-AGG, I-AGG) showed extensive scar formation. No dislocation and no seroma formation were observed. All of these samples showed moderate to severe signs of inflammation with abscess formation in the six meshes of O-AGG. Histology underlined these findings. CONCLUSIONS: The fibrin sealant adhesive showed very good overall results of the primary and secondary outcome parameters. FS is a recommendable atraumatic fixation tool for the surgical onlay technique. AGG provides high adhesive strength, but shows low biocompatibility. Persisting active inflammation was seen in both the O-AGG and I-AGG groups, not favoring its use for these indications.