Adverse effects of porcine small intestine submucosa implants in experimental ventral hernia repair

Abdominal wall hernia repair: from prosthetic meshes to smart materials

Hernia reconstruction is one of the most frequently practiced surgical procedures worldwide. Plastic surgery plays a pivotal role in reestablishing desired abdominal wall structure and function without the drawbacks traditionally associated with general surgery as excessive tension, postoperative pain, poor repair outcomes, and frequent recurrence. Surgical meshes have been the preferential choice for abdominal wall hernia repair to achieve the physical integrity and equivalent components of musculofascial layers. Despite the relevant progress in recent years, there are still unsolved challenges in surgical mesh design and complication settlement. This review provides a systemic summary of the hernia surgical mesh development deeply related to abdominal wall hernia pathology and classification. Commercial meshes, the first-generation prosthetic materials, and the most commonly used repair materials in the clinic are described in detail, addressing constrain side effects and rational strategies to establish characteristics of ideal hernia repair meshes. The engineered prosthetics are defined as a transit to the biomimetic smart hernia repair scaffolds with specific advantages and disadvantages, including hydrogel scaffolds, electrospinning membranes, and three-dimensional patches. Lastly, this review critically outlines the future research direction for successful hernia repair solutions by combing state-of-the-art techniques and materials.

The evaluation of functional small intestinal submucosa for abdominal wall defect repair in a rat model: Potent effect of sequential release of VEGF and TGF-β1 on host integration

Ineffective vessel penetration and extracellular matrix (ECM) remodeling are responsible for the failure of porcine small intestinal submucosa (SIS)-repaired abdominal wall defects. Combined growth factors could be used as directing signals in a nature-mimicking strategy to improve this repair through mesh functionalization. In this work, vascular endothelial growth factor (VEGF) and transforming growth factor β1 (TGF-β1) were incorporated into a silk fibroin membrane via coaxial aqueous electrospinning to exploit their benefits of biological interactions. The membrane was sandwiched into the SIS bilayer as a functional mesh to repair partial-thickness defects in a rat model. Membrane characterization demonstrated that the core-shell structure ensured the independent distribution and sequential release of two regulators and protection of their bioactivities, which were confirmed by cell viability and protein expression. The mesh was further assessed to facilitate vasculature formation and collagen secretion in vitro, and exhibited better host integration than VEGF- or TGF-β1-containing mesh and developed reinforced mechanical properties compared with the VEGF-containing mesh after 28 days in vivo. Determination of the underlying biological interactions revealed that rapid VEGF release promotes angiogenesis and collagen secretion but initially potentiates the inflammatory response. Sustained TGF-β1 release at relatively low concentrations promoted VEGF for vessel permeation and maturation and steadily induced ECM remodeling under milder foreign body reactions. The functionalization of SIS improves repair by sufficient integration with timely remodeling and helps elucidate the related regulatory interactions.

An observational pilot study using a purified reconstituted bilayer matrix to treat non-healing diabetic foot ulcers

Diabetic foot ulcers (DFUs) have significant clinical impact and carry a substantial economic burden. Patients with DFUs that are refractory to standard wound care are at risk for major complications, including infection and amputation and have an increased risk of mortality. This study evaluated the safety and preliminary efficacy of a novel decellularised purified reconstituted bilayer matrix (PRBM) in treating DFUs. Ten diabetic patients with refractory wounds that failed to heal after at least 4 weeks of standard wound care were studied in this Institutional Review Board approved trial. Ten consecutive wounds were treated weekly with the PRBM for up to 12 weeks. At each weekly visit, the wound was evaluated, photographed, and cleaned, followed by application of new graft if not completely epithelialised. Assessment included measurement of the wound area and inspection of the wound site for signs of complications. The primary outcome measure was wound closure, as adjudicated by independent reviewers. Secondary outcomes included assessment of overall adverse events, time to closure, percent area reduction, and the cost of product(s) used. Nine of 10 patients achieved complete wound closure within 4 weeks, and 1 did not heal completely within 12 weeks. The mean time to heal was 2.7 weeks. The mean wound area reduction at 12 weeks was 99%. No adverse events nor wound complications were observed. These early clinical findings suggest that the PRBM may be an effective tool in the treatment of diabetic foot ulcers.

An Immunopathological Evaluation of the Porcine Cholecyst Matrix as a Muscle Repair Graft in a Male Rat Abdominal Wall Defect Model

With the increasing use of animal-based biomaterials for regenerative medical applications, the need for their safety assessment is paramount. A porcine cholecyst-derived scaffold (CDS), intended as a muscle repair graft, prepared by a nondetergent/enzymatic method was engrafted in a rat abdominal wall defect model. Host tissue–scaffold interface samples were collected 2, 8, and 16 weeks postimplantation and evaluated by histopathology, immunohistochemistry, and electron microscopy. The nature of the tissue reaction was compared with those induced by a jejunum-derived scaffold (JDS) prepared by the same method and a commercial-grade small intestinal submucosa (CSIS) scaffold. A study of the immunopathological response in major lymphoid tissues and immunophenotyping for M1 and M2 macrophages was performed at the host tissue–scaffold interface. Further, “irritancy scores” for CDS and JDS were determined using CSIS as the reference material. Both CDS and JDS appeared to be potential biomaterials for muscle grafts, but the former stimulated a skeletal muscle tissue remodeling response predominated by M2 macrophages. The data support the notion that biomaterials with similar biocompatibility, based on local tissue response on implantation, may cause differential immunogenicity. Additionally, CDS compared to JDS and CSIS was found to be less immunotoxic.

In vivo investigation of tissue-engineered periosteum for the repair of allogeneic critical size bone defects in rabbits

Aim: The aim of the study was to evaluate the efficacy of tissue-engineered periosteum (TEP) in repairing allogenic bone defects in the long term. Materials & methods: TEP was biofabricated with osteoinduced rabbit bone marrow mesenchymal stem cells and porcine small intestinal submucosa (SIS). A total of 24 critical sized defects were created bilaterally in radii of 12 New Zealand White rabbits. TEP/SIS was implanted into the defect site. Bone defect repair was evaluated with radiographic and histological examination at 4, 8 and 12 weeks. Results: Bone defects were structurally reconstructed in the TEP group with mature cortical bone and medullary canals, however this was not observed in the SIS group at 12 weeks. Conclusion: The TEP approach can effectively restore allogenic critical sized defects, and achieve maturity of long-bone structure in 12 weeks in rabbit models.

Liquid antiadhesive agents for intraperitoneal hernia repair procedures: Artiss® compared to CoSeal® and Adept® in an IPOM rat model

BACKGROUND

Adhesion formation remains an important issue in hernia surgery. Liquid agents were developed for easy and versatile application, especially in laparoscopy. The aim of this study was to compare the antiadhesive effect of fibrin sealant (FS, Artiss^®), Icodextrin (ID, Adept^®) and Polyethylene glycol (PEG, CoSeal^®) alone and in combination and to evaluate the resulting effect on tissue integration of the mesh.

METHODS

A total of 56 Sprague-Dawley rats were operated in open IPOM technique. A middleweight polypropylene mesh of 2 × 2 cm size was implanted and covered with 1: FS, 2: ID, 3: PEG, 4: FS + ID, 5: FS + PEG, 6: PEG + ID, 7: control group, uncovered mesh (n = 8 per treatment/control). Observation period was 30 days. Macroscopic and histological evaluation was performed.

RESULTS

Severe adhesions were found in group 2 (ID), group 6 (PEG + ID) and the controls. Best results were achieved with FS alone or FS + ID. Mesh integration in the treatment groups was reduced in comparison with the control group. This is a new finding possibly relevant for the outcome of intraperitoneal mesh repair. Group 6 (PEG + ID) showed an impairment of tissue integration with <50 % of the mesh surface in seven samples.

CONCLUSION

FS alone and in combination with ID yielded excellent adhesion prevention. ID alone did not show significant adhesion prevention after 30 days. Tissue integration of FS-covered meshes was superior to ID or PEG alone or combined. PEG did show adhesion prevention comparable to FS but evoked impaired tissue integration. So Artiss^® is among the most potent antiadhesive agents in IPOM repair.

Extracellular matrix-based biomaterial scaffolds and the host response

Extracellular matrix (ECM) collectively represents a class of naturally derived proteinaceous biomaterials purified from harvested organs and tissues with increasing scientific focus and utility in tissue engineering and repair. This interest stems predominantly from the largely unproven concept that processed ECM biomaterials as natural tissue-derived matrices better integrate with host tissue than purely synthetic biomaterials. Nearly every tissue type has been decellularized and processed for re-use as tissue-derived ECM protein implants and scaffolds. To date, however, little consensus exists for defining ECM compositions or sources that best constitute decellularized biomaterials that might better heal, integrate with host tissues and avoid the foreign body response (FBR). Metrics used to assess ECM performance in biomaterial implants are arbitrary and contextually specific by convention. Few comparisons for in vivo host responses to ECM implants from different sources are published. This review discusses current ECM-derived biomaterials characterization methods including relationships between ECM material compositions from different sources, properties and host tissue response as implants. Relevant preclinical in vivo models are compared along with their associated advantages and limitations, and the current state of various metrics used to define material integration and biocompatibility are discussed. Commonly applied applications of these ECM-derived biomaterials as stand-alone implanted matrices and devices are compared with respect to host tissue responses.

Remodeling of Noncrosslinked Acellular Dermal Matrices in a Rabbit Model of Ventral Hernia Repair

Background: Bioprostheses represent a significant advance in the abdominal wall reconstruction since they become degraded until their complete elimination in the recipient organism. This study examines remodeling in the host of three noncrosslinked porcine dermal collagen biomeshes: Strattice™ (St; LifeCell Corp.), XCM Biologic® Tissue Matrix (XCM; Synthes CMF) and Protexa® (Pr; Deco Med S.R.L.). Methods: Partial ventral hernia defects created in New Zealand White rabbits were repaired using the biomeshes that were placed in an inlay, preperitoneal position. At 14 and 90 days after implantation, explants were assessed in terms of their host tissue incorporation by morphological studies, collagen gene/protein expression (quantitative real-time PCR/immunofluorescence), macrophage response (immunohistochemistry) and biomechanical strength. Results: There were no cases of mortality or infection. Among our macroscopic findings, the mesh detachment detected in one third of the Pr implants at 90 days was of note. The host tissue response to all the biomeshes was similar at both time points, with a tendency observed for their encapsulation. There were no appreciable signs of mesh degradation. The extent of host tissue infiltration and collagenization was greater for St and Pr than for XCM. Macrophages were observed in zones of inflammation and tissue infiltration inside the mesh. XCM showed a greater macrophage response at 90 days (p < 0.05). Improved tensile strength was observed for St (p < 0.05) over Pr and unrepaired defects. Conclusions:St showed the best behavior, featuring good collagenization and tensile strength while also inducing a minimal foreign body reaction.

Bovine fetal collagen reinforcement in a small animal model of hernia with component repair

BACKGROUND

Component separation is a surgical strategy used to achieve abdominal wall reconstruction for patients with significant ventral hernias. With an increasing number of variations in procedural techniques and materials, the development of a small animal model of this surgery would allow for the controlled evaluation of variables with analytics not available in human clinical studies. To test this model, we investigated the reinforcement of these component repairs in rats with a bovine fetal collagen (BFC) scaffold.

METHODS

Fifty Sprague Dawley rats were randomized into either component repair alone or BFC reinforced component repair. At time points up to 1 y, these groups were evaluated for hernia formation, strength of repair, strength of mesh-muscle interface, and histology of the repair site.

RESULTS

Anterior component separation was achievable and reproducible in this small animal model. Significantly fewer hernias were found in BFC reinforced repairs. The change in transverse abdominal length was lower for reinforced repairs indicating less external oblique retraction, and reinforced repairs were consistently stronger than controls through 1 y. BFC was revascularized and repopulated with host cells but not rapidly degraded.

CONCLUSIONS

This small animal model of hernia repair with anterior component separation was effective in evaluating the reinforcement of a hernia repair with mesh. It may be useful in future work for the controlled, comparative investigation of different repair techniques and mesh materials in anterior component separation hernia repairs. Additionally, bovine fetal collagen was found to effectively reinforce component repairs and undergo an assimilation process including rapid revascularization and repopulation with host cells followed by gradual extracellular matrix remodeling.

Blood vessel matrix seeded with cells: a better alternative for abdominal wall reconstruction-a long-term study

PURPOSE

The aim of this study was to present abdominal wall reconstruction using a porcine vascular graft seeded with MSC (mesenchymal stem cells) on rat model.

MATERIAL AND METHODS

Abdominal wall defect was prepared in 21 Wistar rats. Acellular porcine-vascular grafts taken from aorta and prepared with Triton X were used. 14 aortic grafts were implanted in place, of which 7 grafts were seeded with rat MSC cells (Group I), and 7 were acellular grafts (Group II). As a control, 7 standard polypropylene meshes were used for defect augmentation (Group III). The assessment method was performed by HE and CD31 staining after 6 months. The mechanical properties have been investigated by Zwick&Roell Z0.5.

RESULTS

The strongest angiogenesis and lowest inflammatory response were observed in Group I. Average capillaries density was 2.75, 0.75, and 1.53 and inflammatory effect was 0.29, 1.39, and 2.72 for Groups I, II, and III, respectively. The means of mechanical properties were 12.74 ± 1.48, 7.27 ± 1.56, and 14.4 ± 3.7 N/cm in Groups I and II and control, respectively.

CONCLUSIONS

Cell-seeded grafts have better mechanical properties than acellular grafts but worse than polypropylene mesh. Cells improved mechanical and physiological properties of decellularized natural scaffolds.

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.

Decellularized allogeneic and xenogeneic tissue as a bioscaffold for regenerative medicine: factors that influence the host response

Biologic scaffold materials composed of mammalian extracellular matrix (ECM) are prepared by decellularization of source tissues harvested from either humans (allogeneic) or a variety of other (xenogeneic) species. These matrix scaffold materials are commonly regulated and used as surgical mesh materials for applications such as ventral hernia repair, musculotendinous tissue reconstruction, dura mater replacement, reconstructive breast surgery, pelvic floor reconstruction, and the treatment of cutaneous ulcers, among others. The clinical results for these applications vary widely for reasons which include characteristics of the source tissue, methods and efficacy of tissue decellularization, and methods of processing/manufacturing. However, the primary determinant of success or failure in the clinical setting is the response of the host to these implanted biologic scaffold materials. It is logical to question why any non-self biologic material, particularly a xenogeneic material, would not elicit an early and aggressive adverse immune response. The present manuscript briefly describes the known mechanisms by which these biologic scaffold materials can facilitate a constructive remodeling response, the known causative factors of an adverse response, and provides a general discussion of the role of the macrophage in determining outcome.

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.

The use of porcine small intestine submucosa implants might be associated with a high recurrence rate following laparoscopic herniorrhaphy

BACKGROUND/PURPOSE

The efficacy of porcine small intestine submucosa (SIS) implants in hernia repair has rarely been reported and remained elusive. We herein report our experience to further elucidate the efficacy of SIS mesh in herniorrhaphy.

METHODS

Between June 2008 and October 2009, a total of 82 patients with 125 inguinal hernias undergoing endoscopic total extraperitoneal (TEP) herniorrhaphy were included. Seventy patients (with 108 hernias) had traditional polypropylene and 12 patients (with 17 hernias) had SIS mesh repair. Postoperative complications and recurrence rates were compared between the two meshes.

RESULTS

The demographics between two groups were similar. All operations were performed smoothly with laparoscopy, and the postoperative courses were uneventful. After a median follow-up of 18 months, five (7%) in the polypropylene group and three (25%) in the SIS group had chronic pain (p = 0.09). Five of 17 (29.4%) hernia repairs in the SIS group had an ipsilateral recurrence, compared to no recurrence in the polypropylene group. In the five cases, the second laparoscopy revealed the SIS mesh had been totally degraded and there was no obvious fibrotic tissue in the previous mesh sites.

CONCLUSION

Our data suggest that the use of SIS mesh in endoscopic TEP herniorrhaphy might be associated with a high recurrence rate. The second look laparoscopy in these recurrent cases revealed slow and inadequate integration of host tissue. More evidence is still required to further evaluate the efficacy of SIS mesh in endoscopic TEP herniorrhaphy.

Effect of surgical wound classification on biologic graft performance in complex hernia repair: an experimental study

BACKGROUND

Despite relatively sparse data regarding their outcomes in the setting of infection, biologic grafts have gained rapid acceptance by the surgical community for complex hernia repair. These materials are heterogeneous in their procurement and processing techniques, which may ultimately have an impact in their ability to withstand infection. The objective of this study is to evaluate the impact of varying levels of contamination on biologic graft performance in a chronic ventral hernia animal model.

METHODS

Four commonly applied biologic grafts were used in the repair of a chronic ventral hernia rat model (n = 218). Each material was repaired in the setting of 1 of 4 surgical wound classifications (clean, clean contaminated, contaminated, dirty infected) with Staphylococcus aureus as our inoculum agent. After a 30-day survival, repairs underwent quantitative cultures, histological, and biomechanical testing.

RESULTS

Marked differences were observed in biologic graft bacterial burden, biomechanical and histological responses at 30 days. Persistent bacterial burden varied among the biologic grafts and increased with increasing wound contamination (P < .05). Delays in wound healing were observed in the contaminated and dirty infected setting (P < .05). Increasing infection weakened the biomechanical strength of repairs (P < .05).

CONCLUSION

The degree of bacterial contamination at the time of repair affected the rates of bacterial clearance, wound-healing ability, and subsequent repair strength. Material source and processing techniques might alter graft durability, biocompatibility, and ability to clear bacteria in a contaminated field. Clinical trials are warranted in contaminated settings.

Properties comparison of intraperitoneal hernia meshes in reconstruction of the abdominal wall: animal model study

Modern methods of hernia tension free treatment use very wide range of modern biomaterials. Most of them are used transabdominal. For the best and most convenient treatment of large hernias would be a mesh suitable for intraperitoneal use with low adhesion ability to internal organs.THE AIM OF THE STUDY was to compare three types of intraperitoneal meshes. MATERIAL AND METHODS. The study compared three types of intraperitoneal meshes. Sub-chronic (14 days) and chronic (90 days) macro-and microscopic examination were performed on rats (n = 69). Properties of the polypropylene mesh (PLP), Dynamesh®-iPOM and polypropylene covered with chitosan (PLP+chitosan) were evaluated and compared. RESULTS. It has been shown that the test meshes differ slightly during the healing process.

CONCLUSION

The PLP+chitosan mesh had the best biocompatible features of them all.

Biological meshes: a review of their use in abdominal wall hernia repairs

PURPOSE

Biological meshes are mostly used in infected fields within complex abdominal wall hernia repairs. There is no consensus, however, on the most appropriate material to be used in a given situation.

METHODS

A literature review of published articles reporting the utilization of biological meshes in ventral/incisional hernia repair was conducted. Data were analyzed to compare the recurrence rates obtained with biological meshes.

MAIN FINDINGS

Only a few prospective comparative studies were identified. Most publications relate to AlloDerm®, Permacol™ and Surgisis™ with data from other meshes insufficient to draw conclusions. AlloDerm has a 0-100% recurrence rate among studies. It compares poorly with Surgisis and results in an unfavorable outcome when used as a 'bridge prosthesis'. Permacol has consistent recurrence rates of 0-15%, whatever the patients' profiles or the context of infected fields, when considering the most relevant studies. The Surgisis results are more conflicting: the mesh exhibits low recurrence rates in clean fields, but in infected fields the recurrence rate is up to 39%.

CONCLUSION

Taken together, these studies suggest that the cross-linked mesh, Permacol has the lowest failure rate and the longest time to failure, particularly in contaminated or infected fields. However, this data should be confirmed by large prospective randomized studies.

Transthoracic repair of an incarcerated diaphragmatic hernia using hexamethylene diisocyanate cross-linked porcine dermal collagen (Permacol)

It is the general surgeon who commonly repairs paraesophageal hernias nowadays, and they are repaired laparoscopically, making the performance of thoracotomy relatively rare. Whether to use prosthetic materials to repair the hiatus is still under debate, as is the question of which material to use, if any. We report a case of a 38-year-old man who had a large, incarcerated paraesophageal hernia. He had a past history of extensive abdominal surgery for exomphalos, which rendered any abdominal surgical approach a high-risk procedure. We therefore decided to proceed with thoracotomy and repair of the hiatus with hexamethylene diisocyanate (HMDI) cross-linked porcine dermal collagen. He made a good recovery with no complications.

Evaluation of crosslinked and non-crosslinked biologic prostheses for abdominal hernia repair

Introduction

Abdominal wall defects and incisional hernias represent a challenging problem. Currently, several commercially available biologic prostheses are used clinically for hernia repair. We compared the performance and efficacy of two non-crosslinked meshes in ventral hernia repair to two crosslinked prostheses in a rodent model.

Methods

Animals were divided into 12 groups (4 matrix types and 3 termination time-points per matrix). A ventral defect was carefully created and overlapped with the biologic prosthesis.

Results

Major complications were seroma induction (3 mesh types), implant extrusion (1 mesh type), severe inflammatory and immune responses (non-crosslinked mesh), fibrosis and mineralisation (3 mesh types). After inflammation resolution, 3 of the matrices tested supported hernia healing but with marked tissue and temporal differences. AlloDerm^®* and Surgisis Gold™ showed tissue reactivity with the host and a rapid rate of matrix remodelling. Bard CollaMend™^* Implant proved to be inept for hernia repair under the conditions tested. Permacol™ biological implant integration with host tissue increased over time, supporting hernia healing with strength of tissue, and appears to be a safe prosthetic material for ventral hernia repair based on the results of this rodent study.

Bacterial clearance of biologic grafts used in hernia repair: an experimental study

BACKGROUND

Biologic grafts used in ventral hernia repair are derived from various sources and undergo different post-tissue-harvesting processing, handling, and sterilization techniques. It is unclear how these various characteristics impact graft response in the setting of contamination. We evaluated four materials in an infected hernia repair animal model using fluorescence imaging and quantitative culture studies.

METHODS

One hundred seven rats underwent creation of a chronic hernia. They were then repaired with one synthetic polyester control material (n = 12) and four different biologic grafts (n = 24 per material). Biologic grafts evaluated included Surgisis (porcine small intestinal submucosa), Permacol (crosslinked porcine dermis), Xenmatrix (noncrosslinked porcine dermis), and Strattice (noncrosslinked porcine dermis). Half of the repairs in each group were inoculated with Staphylococcus aureus at 10(4) CFU/ml and survived for 30 days without systemic antibiotics. Animals then underwent fluorescence imaging and quantitative bacterial studies.

RESULTS

All clean repairs remained sterile. Rates of bacterial clearance were as follows: polyester synthetic 0%, Surgisis 58%, Permacol 67%, Xenmatrix 75%, and Strattice 92% (P=0.003). Quantitative bacterial counts had a similar trend in bacterial clearance: polyester synthetic 1×10(6) CFU/g, Surgisis 4.3×10(5) CFU/g, Permacol 1.7×10(3) CFU/g, Xenmatrix 46 CFU/g, and Strattice 31 CFU/g (P=0.001). Fluorescence imaging was unable to detect low bacterial fluorescence counts observed on bacterial studies.

CONCLUSION

Biologic grafts, in comparison to synthetic material, are able to clear a Staphylococcus aureus contamination; however, they are able to do so at different rates. Bacterial clearance correlated to the level of residual bacterial burden observed in our study. Post-tissue-harvesting processing, handling, and sterilization techniques may contribute to this observed difference in ability to clear bacteria.

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.

Adverse effects of polyvinylidene fluoride-coated polypropylene mesh used for laparoscopic intraperitoneal onlay repair of incisional hernia

BACKGROUND

Polyvinylidene fluoride-coated polypropylene meshes have been developed specifically for intraperitoneal onlay mesh repair. They combine a macroporous design with biomechanical characteristics compatible with the abdominal wall and are reported to have favourable antiadhesive properties. This retrospective study reports complications related to one of these materials, DynaMesh.

METHODS

Twenty-nine patients underwent intraperitoneal onlay mesh repair with DynaMesh at one of two hospitals. Patients characteristics, surgical procedures and postoperative analgesia were comparable at both sites.

RESULTS

Six patients developed DynaMesh-related complications that required surgical reintervention by laparotomy within 1 year of operation. Surgical reintervention was for adhesions in five patients and the mesh had to be explanted in three. One mesh was explanted because of early infection. Adhesions to DynaMesh were found in two patients who had surgery for unrelated reasons.

CONCLUSION

Laparoscopic intraperitoneal onlay DynaMesh repair was associated with a high rate of complications.

Animal model of chronic abdominal hernia in rabbit

PURPOSE

To create a feasible animal model of hernia that should be reliable to test the different types of mesh and/or surgical technique.

METHODS

Thirty six male New Zealand albino rabbits were submitted to surgical procedure to provoke a standard hole in the abdominal wall. A metallic frame measuring 3 cm length and 1 cm width was allocated longitudinally on the umbilicus scar and the comprehensive three squared centimeters area was resected. A continuous 4.0 polyamide was performed to closure the subcutaneous and skin.

RESULTS

During three weeks a score of signals/symptoms was performed to evaluate the wound and clinical conditions. No death or severe complications occurred. In the 3rd week the hernia ring and visceral adhesions were evaluated. Soft omental adherences were present in the hernial sac in all animals. The area of hernia ring ranged from 32.1+/-5.5 to 35.6+/-3.1 squared centimeter and the maximum was 39 cm(2) and the minimum was 30 cm(2). The model results in protrusion which was similar to a human incisional hernia with hernia sac, visceral adhesions and fibrous healing ring.

CONCLUSION

The model was more reliable to test further techniques or mesh on hernia repair.

The feasibility of FS mesh fixation by a transgastric approach--an important benefit in future NOTES procedures?

BACKGROUND

Preserving the integrity of the abdominal wall is a major benefit in NOTES procedures. It may result in a decrease of postoperative (postOP) pain, infection, and port site hernia. This experimental study on intra-peritoneal onlay mesh (IPOM) repair was designed to apply meshes by a transgastric access (TGA) and to use a combination of transfascial sutures and fibrin sealant as fixation.

MATERIALS AND METHODS

Four abdominal wall defects were created by TGA under laparoscopic control in five nonsurvival and three survival pigs (4, 11, and 22 d observation period). Titanized polypropylene meshes were fixed transfascially by four polypropylene sutures using a "suture passer" device. Meshes were additionally fixed with 0.2 mL of fibrin sealant (FS) by an endoscopic application. TGA was closed with endoclips in the nonsurvival model and with laparoscopic suturing in survival pigs.

RESULTS

The three survival pigs were euthanized on the d 4, 11, and 22 postOP. The macroscopic evaluation revealed excellent integration of the meshes without signs of shrinkage, dislocation, or inflammation. Histology confirmed macroscopic findings.

CONCLUSIONS

Our findings confirm that IPOM repair of ventral hernia in an experimental NOTES hybrid procedure is feasible. This study also demonstrates the technical feasibility and the potential advantages of FS mesh fixation to further reduce trauma to the abdominal wall following the key principles of the NOTES approach.

A porcine-derived acellular dermal scaffold that supports soft tissue regeneration: removal of terminal galactose-alpha-(1,3)-galactose and retention of matrix structure

Sub-optimal clinical outcomes after implantation of animal-derived tissue matrices may be attributed to the nature of the processing of the material or to an immune response elicited in response to xenogeneic epitopes. The ability to produce a porcine-derived graft that retains the structural integrity of the extracellular matrix and minimizes potential antigenic response to galactose-alpha-(1,3)-galactose terminal disaccharide (alpha-Gal) may allow the scaffold to support regeneration of native tissue. Dermal tissue from wild-type (WT-porcine-derived acellular dermal matrix [PADM]) or Gal-deficient (Gal(-/-) PADM) pigs was processed to remove cells and DNA while preserving the structural integrity of the extracellular matrix. In addition, the WT tissue was subjected to an enzymatic treatment to minimize the presence of alpha-Gal (Gal-reduced PADM). Extracellular matrix composition and integrity was assessed by histological, immunohistochemical (IHC), and ultrastructural analysis. In vivo performance was evaluated by implantation into the abdominal wall of Old World primates in an exisional repair model. Anti-alpha-Gal activity in the serum of monkeys implanted subcutaneously was assessed by ELISA. Minimal modification to the extracellular matrix was assessed by evaluation of intact structure as demonstrated by staining patterns for type I and type VII collagens, laminin, and fibronectin similar to native porcine skin tissues. Explants from the abdominal wall showed evidence of remodeling, notably fibroblast cell repopulation and revascularization, as early as 1 month. Serum ELISA revealed an initial anti-alpha-Gal induction that decreased to baseline levels over time in the primates implanted with WT-PADM, whereas no or minimal anti-Gal activity was detected in the primates implanted with Gal(-/-) PADM or Gal-reduced PADM. The combination of a nondamaging process, successful removal of cells, and reduction of xenogeneic alpha-Gal antigens from the porcine dermal matrix are critical for producing a material with the ability to remodel and integrate into host tissue and ultimately support soft tissue regeneration.

Multicentric observational cohort study evaluating a composite mesh with incorporated oxidized regenerated cellulose in laparoscopic ventral hernia repair

BACKGROUND

A variety of newly developed mesh products have recently become available to use inside the peritoneal cavity. This analysis reports the first clinical data evaluating the experience with the use of Proceed mesh in laparoscopic ventral hernia repair.

PATIENTS AND METHODS

During a 6-month period, 114 adult patients underwent a laparoscopic ventral hernia repair using an intra-abdominal placement of a Proceed mesh. The operative procedure was stratified for all centers. Perioperatively, different parameters were evaluated considering the conversion rate to open procedure, complications such as seroma and hematoma, bowel lesions, urinary retention, acute, and chronic pain, mesh infection, and recurrences.

RESULTS

The mean age of the patients was 45 years (range 19-84 years). There were no conversions to open repair and no mortality. Complications included 12 seromas/hematomas (four aspirated), chronic discomfort in two patients, and urinary retention in one patient. There have been four recurrences (3.5%), occurring 3, 4, 4, and 15 months after surgery, respectively. The mean follow-up period was 27 months (range 12-38 months). There have been no documented infections of the mesh.

CONCLUSIONS

This multicentric study documents a favorable experience using large-pore mesh in laparoscopic ventral hernia repair. There were no major complications related to the mesh. Technical advantages considering mesh handling and long-term advantages considering chronic pain might be of interest with the use of this lightweight mesh for minimally invasive ventral hernia repair.

Fibrin sealant (Tissucol) enhances tissue integration of condensed polytetrafluoroethylene meshes and reduces early adhesion formation in experimental intraabdominal peritoneal onlay mesh repair

BACKGROUND

The laparoscopic intraabdominal peritoneal onlay mesh repair (IPOM) is a common technique for the reinforcement of multiple ventral hernias or defined defects after laparotomies. However, the placement of synthetic meshes in the intraabdominal cavity can be associated with severe complications. Adhesions frequently originate from the implant and protruding parts of fixation devices, presenting a serious clinical problem with potentially detrimental consequences. This study was designed to assess the impact of fibrin sealing with Tissucol (FS; Baxter, Vienna, Austria) on adhesion formation to condensed polytetrafluoroethylene meshes (Motif Meshes, MM; Proxy Biomedical, Galway, Ireland) as well as on tissue integration of these implants in experimental IPOM repair in rats. It was tested whether FS application allowed the reduction of sutures for mesh fixation without increasing the risk of mesh dislocation.

MATERIALS AND METHODS

Sixteen rats were assigned to the implantation of MM with four nonresorbable sutures (Synthofil; Ethicon, Norderstedt, Germany) with additional fibrin coating with 0.2 mL FS or to MM fixation with six nonresorbable sutures without FS (n = 8 per group). MM with 2 cm in diameter were implanted in open IPOM by a laparatomy. The observation period of 17 days ensured assessment of adhesions after the full degradation of FS. Adhesions were rated with the score suggested by Vandendael. Histology was performed.

RESULTS

All eight MMs without FS sealing elicited severe (grade III) adhesions, whereas fibrin-sealed MM were rated mild in 1, moderate in 5, and severe in 2 cases. The superior finding in the FS group was statistically significant. Impaired integration of sutured-only MM was observed in four cases, whereas all FS-sealed MM were well integrated.

CONCLUSIONS

FS improves the tissue integration, reduces early adhesion formation to cPTFE implants, and allows reduction of perforating fixation devices in experimental IPOM repair.

Experimental evaluation of four biologic prostheses for ventral hernia repair

PURPOSE

To evaluate two bioprostheses derived from bovine pericardium, one cross-linked (Peri-Guard) and the other non-cross-linked (Veritas), and to compare them with Alloderm and Permacol for abdominal wall repair.

METHODS

The four prostheses were tested in acute and chronic hernia models. Prostheses were either sutured to the edge of the abdominal wall defect (inlay) or secured as an underlay with surgical tacks. Evaluation at 3 and 6 months included adhesion formation, defect area size and thickness, tensile strength, and histology.

RESULTS

Mean adhesion coverage area ranged from 25 to 31%. The two cross-linked materials, Permacol and Peri-Guard, showed greater tensile strength. Significant defect contraction followed repair with Veritas, whereas Alloderm stretched. All prostheses had cellular ingrowth and neovascularization by 3 months. No significant differences were found in prosthesis to abdominal wall breaking strength. Operative site infection occurred in six animals (5 Peri-Guard, 1 Veritas), and overlying skin ulceration in six others (6 Peri-Guard).

CONCLUSIONS

Permacol provided a strong and durable repair for up to six months. Peri-Guard was equally strong but prone to infection and to skin ulceration. With time, Veritas and Alloderm lost tensile strength associated with marked thinning and with hernia-like bulging in the case of Alloderm.

Abdominal wall repair using human acellular dermis

BACKGROUND

The surgical repair of abdominal wall defects that cannot be closed primarily in contaminated fields is a difficult problem. The use of nonabsorbable synthetic materials usually is contraindicated in this setting because of the risk for colonization and chronic infection of the mesh. In this study we sought to determine the safety and efficacy of implanted human acellular dermal graft for abdominal wall reconstruction.

METHODS

The records of all patients (n = 20) who underwent a repair of an abdominal wall defect with human acellular dermal graft at a Veteran Affairs hospital were reviewed retrospectively. Patient demographics, complications, and hernia recurrence were recorded.

RESULTS

There were 15 perioperative complications in 11 patients: 6 graft dehiscences, 1 evisceration, 2 postoperative intra-abdominal bleeds, 5 bacterial graft infections, and 1 death. Patients with heart disease, American Society of Anesthesiologists classification of 4, and/or dirty wounds were more likely to have perioperative complications. The median follow-up period was 9.4 months (range, 2-16 mo), during which 6 hernia recurrences were noted.

CONCLUSIONS

Human acellular dermis use is safe in abdominal wall reconstructions in contaminated surgical wounds.

Adverse effects associated with the use of porcine cross-linked collagen implants in an experimental model of incisional hernia repair

BACKGROUND

Porcine cross-linked collagen (PermaCol, PCL; TSL, Aldershot, United Kingdom) has been proposed as permanent biomaterial in incisional hernia repair. We evaluated the biocompatibility of PCL in an established animal model.

MATERIAL AND METHODS

In 10 Sprague Dawley rats, two hernias per animal were created in the abdominal wall left and right of the linea alba (1.5 cm in diameter), and the peritoneum was spared. The lesions were left untreated for 10 days, until incisional hernias developed. These defects were covered with non-perforated (out-of-the-box, n = 12) or perforated (modified; n = 8) PCL (2 x 2 cm). In a first step, 12 non-perforated implants were tested in a short-term observation period of 17 days. Eight of these non-perforated implants were fibrin sealed (0.3 mL, Tissucol; Baxter, Vienna, Austria), whereas four non-perforated implants were sutured with non-resorbable material. In a second step, perforations were added as modification to PCL to facilitate drainage of fluids, cell ingrowth, and transgression of fibrin sealant. All perforated implants were fibrin sealed and included in a long-term observation period of 3 months. The observation periods allowed the evaluation of the complete degradation of the fibrin sealant fixation after 2 weeks and of the implant integration in a chronic timeframe. Implant sites were analyzed macroscopically and histologically.

RESULTS

All PCL samples elicited strong local inflammation with signs of foreign body reaction. Integration of perforated PCL appeared limited after 3 months. Three animals had to be euthanized prior to intended time points because of transcutaneous migration of implants.

CONCLUSIONS

In an experimental model of incisional hernia repair, PCL does not integrate well in the abdominal wall and shows poor biocompatibility.