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

Living scaffolds: surgical repair using scaffolds seeded with human adipose-derived stem cells

BACKGROUND

Decellularized porcine small intestinal submucosa (SIS) is a biological scaffold used surgically for tissue repair. Here, we demonstrate a model of SIS as a scaffold for human adipose-derived stem cells (ASCs) in vitro and apply it in vivo in a rat ventral hernia repair model.

STUDY DESIGN

ASCs adherence was examined by confocal microscopy and proliferation rate was measured by growth curves. Multipotency of ASCs seeded onto SIS was tested using adipogenic, chondrogenic, and osteogenic induction media. For in vivo testing, midline abdominal musculofascial and peritoneal defects were created in Sprague-Dawley rats. Samples were evaluated for tensile strength, histopathology and immunohistochemistry.

RESULTS

All test groups showed cell adherence and proliferation on SIS. Fibronectin-treated scaffolds retained more cells than those treated with vehicle alone (p < 0.05). Fresh stromal vascular fraction (SVF) pellets containing ASCs were injected onto the SIS scaffold and showed similar results to cultured ASCs. Maintenance of multipotency on SIS was confirmed by lineage-specific markers and dyes. Histopathology revealed neovascularization and cell influx to ASC-seeded SIS samples following animal implantation. ASC-seeded SIS appeared to offer a stronger repair than plain SIS, but these results were not statistically significant. Immunohistochemistry showed continued presence of cells of human origin in ASC-seeded repairs at 1 month postoperation.

CONCLUSION

Pretreatment of the scaffold with fibronectin offers a method to increase cell adhesion and delivery. ASCs maintain their immunophenotype and ability to differentiate while on SIS. Seeding freshly isolated SVF onto the scaffold demonstrated that minimally manipulated cells may be useful for perioperative surgical applications within the OR suite. We have shown that this model for a "living mesh" can be successfully used in abdominal wall reconstruction.

Rectopexy for Rectal Prolapse

INTRODUCTION

Ventral mesh rectopexy (VMR) is a recognized treatment for posterior compartment pelvic organ prolapse (POP). The aim of this review is to provide a synopsis of the evidence for biological mesh use in VMR, the most widely recognized surgical technique for posterior compartment POP.

METHODS

A systematic search of PubMed was conducted using the search terms "VMR," "ventral mesh rectopexy," or "mesh rectopexy." Six studies were identified.

RESULTS

About 268/324 patients underwent ventral rectopexy using biological mesh with a further 6 patients having a combination of synthetic and biological mesh. Recurrence was reported in 20 patients; however, 6 were from studies where data on biological mesh could not be extracted. There are no RCTs in VMR surgery and no studies have directly compared types of biological mesh. Cross-linked porcine dermal collagen is the most commonly used mesh and has not been associated with mesh erosion, infection, or fistulation in this review. The level of evidence available on the use of biological mesh in VMR is of low quality (level 4).

CONCLUSION

Ventral mesh rectopexy has become prevalent for posterior compartment POP. The evidence base for its implementation is not strong and the quality of evidence to inform choice of mesh is poor.

Engineered composite fascia for stem cell therapy in tissue repair applications

A critical challenge in tissue regeneration is to develop constructs that effectively integrate with the host tissue. Here, we describe a composite, laser micromachined, collagen-alginate construct containing human mesenchymal stem cells (hMSCs) for tissue repair applications. Collagen type I was fashioned into laminated collagen sheets to form a mechanically robust fascia that was subsequently laser micropatterned with pores of defined dimension and spatial distribution as a means to modulate mechanical behavior and promote tissue integration. Significantly, laser micromachined patterned constructs displayed both substantially greater compliance and suture retention strength than non-patterned constructs. hMSCs were loaded in an RGD-functionalized alginate gel modified to degrade in vivo. Over a 7 day observation period in vitro, high cell viability was observed with constant levels of VEGF, PDGF-β and MCP-1 protein expression. In a full thickness abdominal wall defect model, the composite construct prevented hernia recurrence in Wistar rats over an 8-week period with de novo tissue and vascular network formation and the absence of adhesions to underlying abdominal viscera. As compared to acellular constructs, constructs containing hMSCs displayed greater integration strength (cell seeded: 0.92 ± 0.19 N/mm vs. acellular: 0.59 ± 0.25 N/mm, p=0.01), increased vascularization (cell seeded: 2.7-2.1/hpf vs. acellular: 1.7-2.1/hpf, p<0.03), and increased infiltration of macrophages (cell seeded: 2021-3630 μm(2)/hpf vs. acellular: 1570-2530 μm(2)/hpf, p<0.05). A decrease in the ratio of M1 macrophages to total macrophages was also observed in hMSC-populated samples. Laser micromachined collagen-alginate composites containing hMSCs can be used to bridge soft tissue defects with the capacity for enhanced tissue repair and integration.

STATEMENT OF SIGNIFICANCE

Effective restoration of large soft tissue defects caused by trauma or treatment complications represents a critical challenge in the clinic. In this study, a novel composite construct was engineered and evaluated for stem cell delivery and tissue repair. Laser micromachining was used to fabricate patterned, microporous constructs designed with pores of defined size and distribution as a means to tune mechanical responses, accommodate and protect incorporated cells, and enhance tissue integration. The construct was embedded within an engineered alginate gel containing hMSCs. Upon repair of a full thickness abdominal wall defect in a rat model, the composite construct modulated host innate immunity towards a reparative phenotypic response, promoted neovascularization and associated matrix production, and increased the strength of tissue integration.

Comparison of Porcine Small Intestinal Submucosa versus Polypropylene in Open Inguinal Hernia Repair: A Systematic Review and Meta-Analysis

Background

A systematic review and meta-analysis was performed in randomized controlled trials (RCTs) to compare porcine small intestinal submucosa (SIS) with polypropylene in open inguinal hernia repair.

Method

Electronic databases MEDLINE, Embase, and the Cochrane Library were used to compare patient outcomes for the two groups via meta-analysis.

Result

A total of 3 randomized controlled trials encompassing 200 patients were included in the meta-analysis. There was no significant difference in recurrence (P = 0.16), hematomas (P = 0.06), postoperative pain within 30 days (P = 0.45), or postoperative pain after 1 year (P = 0.12) between the 2 groups. The incidence of discomfort was significantly lower (P = 0.0006) in the SIS group. However, the SIS group experienced a significantly higher incidence of seroma (P = 0.03).

Conclusions

Compared to polypropylene, using SIS in open inguinal hernia repair is associated with a lower incidence of discomfort and a higher incidence of seroma. However, well-designed larger RCT studies with a longer follow-up period are needed to confirm these findings.

Biologic mesh versus synthetic mesh in open inguinal hernia repair: system review and meta-analysis

BACKGROUND

Biologic meshes are mostly used for abdominal wall reinforcement in infected fields, but no consensus has been reached on its use for inguinal hernia repairing. The purpose of this study was to compare biologic mesh with synthetic mesh in open inguinal herniorrhaphy.

METHODS

A systematic literature review and meta-analysis was undertaken to identify studies comparing the outcomes of biologic mesh and synthetic mesh in open inguinal hernia repair. Published studies were identified by the databases PubMed, EMBASE and the Cochrane Library.

RESULTS

A total of 382 patients in five randomized controlled trials were reviewed (179 patients in biologic mesh group; 203 patients in synthetic mesh group). The two groups did not significantly differ in chronic groin pain (P = 0.06) or recurrence (P = 0.38). The incidence of seroma trended higher in biologic mesh group (P = 0.03). Operating time was significantly longer with biologic mesh (P = 0.03). There was no significant difference in hematomas (P = 0.23) between the two groups.

CONCLUSIONS

From the data of this study, biologic mesh had no superiority to synthetic mesh in open inguinal hernia repair with similar recurrence rates and incidence of chronic groin pain, but higher rate of seroma and longer operating time. However, this mesh still needs to be assessed in a large, multicentre, well-designed randomized controlled trial.

Mesh herniorrhaphy with simultaneous colorectal surgery: a case-matched study from the American College of Surgeons National Surgical Quality Improvement Program

BACKGROUND

The aim of this study is to evaluate the impact of concurrent mesh herniorrhaphy on short-term outcomes of colorectal surgery by using a large, nationwide database.

METHODS

Patients who underwent simultaneous ventral hernia repair (VHR) and colorectal surgery between 2005 and 2010 were identified from the American College of Surgeons National Surgical Quality Improvement Program. Patients who underwent VHR with mesh repair were case matched with patients who underwent VHR without mesh based on the type of colorectal procedure, diagnosis, and American Society of Anesthesiologists score.

RESULTS

Two hundred sixty-two patients who underwent VHR with mesh were case matched with 524 patients who underwent VHR without mesh. Mean operating time was significantly longer in patients who underwent VHR with mesh (195.8 ± 98.7 vs 164.3 ± 84.4 minutes, P < .001). Postoperative morbidity (P = .58), mortality (P = .27), superficial surgical site infection (SSI) (P = .14), deep SSI (P = .38), organ space SSI (P = .17), wound disruption (P > .99), reoperation (P = .48), and length of hospital stay (P = .71) were comparable between the groups.

CONCLUSION

The American College of Surgeons National Surgical Quality Improvement Program data suggest that VHR with mesh does not increase 30-day mortality, medical or surgical morbidity in colorectal surgery setting.

Use of a porcine dermal collagen implant for contaminated abdominal wall reconstruction in a 105-year-old woman: a case report and review of the literature

INTRODUCTION

Repair of contaminated abdominal wall defect in a geriatric patient is a challenge for the surgeon. We present the case of the oldest patient (105-years old) to successfully undergo a single-stage repair of a contaminated abdominal wall defect with a Permacol™ implant.

CASE PRESENTATION

A 105-year-old Caucasian woman presented to our emergency room with a clinical and radiological diagnosis of small bowel obstruction due to prior operative adhesions. She underwent laparotomy with small bowel resection and primary closure of her abdomen. There was total eventration of her bowel through the suture line 9 days after surgery. She underwent a second laparotomy that revealed no signs of peritonitis or turbid fluid. Her abdomen was closed with a 15 × 10 cm Permacol™ implant sutured sublay with prolene sutures. Her postoperative period was unremarkable. After a follow-up period of 3 years and 2 months, there was no sign of recurrent hernia or wound contamination.

CONCLUSION

We suggest that Permacol™ mesh can be considered an efficient alternative to primary closure or synthetic mesh in geriatric patients with contaminated abdominal wall defects.

Characterisation and comparison of the host response of 6 tissue-based surgical implants in a subcutaneous in vivo rat model

BACKGROUND

Hernia repair often involves fascial augmentation using biologic prostheses. Small processing changes during preparation modulate host tissue response, which influence material efficacy and longevity. In this pilot study, a rat model was used to determine the specific influence of tissue origin, decellularisation treatment and 1,6-hexamethylene diisocyanate (HMDI) cross-linking.

METHODS

Materials (1 cm2) were implanted subcutaneously into 6-week-old Wistar rats (4 materials per animal, n=6/material per time point) for 2, 5, 7, 14 and 28 days. Histologic processing was carried out after resin infiltration, observing classical histopathology and pathologic indexing. Materials comprised 6 tissue-based grafts covering both experimental and commercial porcine decellularised dermal and small intestinal submucosal materials.

RESULTS

Subcutaneous delivery of biologics demonstrated material-specific inflammatory/host responses. Controlled variations of the PermacolTM manufacturing process showed sodium dodecyl sulfate (SDS) was the most proinflammatory decellularisation reagent, and HMDI cross-linking had no effect on host response. All materials remained recoverable after 28 days, although SurgisisTM had partially resorbed.

CONCLUSION

Differences in host responses exist between biologic implants for hernia repair in this rat model. It is postulated that these modifications are induced during processing and may have an effect on the clinical outcome of hernia repair.

To cross-link or not to cross-link? Cross-linking associated foreign body response of collagen-based devices

Collagen-based devices, in various physical conformations, are extensively used for tissue engineering and regenerative medicine applications. Given that the natural cross-linking pathway of collagen does not occur in vitro, chemical, physical, and biological cross-linking methods have been assessed over the years to control mechanical stability, degradation rate, and immunogenicity of the device upon implantation. Although in vitro data demonstrate that mechanical properties and degradation rate can be accurately controlled as a function of the cross-linking method utilized, preclinical and clinical data indicate that cross-linking methods employed may have adverse effects on host response, especially when potent cross-linking methods are employed. Experimental data suggest that more suitable cross-linking methods should be developed to achieve a balance between stability and functional remodeling.

Decellularization and cell seeding of whole liver biologic scaffolds composed of extracellular matrix

The definitive treatment for patients with end-stage liver disease is orthotropic transplantation. However, this option is limited by the disparity between the number of patients needing transplantation and the number of available livers. This issue is becoming more severe as the population ages and as the number of new cases of end-stage liver failure increases. Patients fortunate enough to receive a transplant are required to receive immunosuppressive therapy and must live with the associated morbidity. Whole organ engineering of the liver may offer a solution to this liver donor shortfall. It has been shown that perfusion decellularization of a whole allogeneic or xenogeneic liver generates a three-dimensional ECM scaffold with intact macro and micro architecture of the native liver. A decellularized liver provides an ideal transplantable scaffold with all the necessary ultrastructure and signaling cues for cell attachment, differentiation, vascularization, and function. In this review, an overview of complementary strategies for creating functional liver grafts suitable for transplantation is provided. Early milestones have been met by combining stem and progenitor cells with increasingly complex scaffold materials and culture conditions.

Surgical approach to abdominal wall defects: history and new trends

We briefly outline the history of hernia surgery development from the Ebers Papyrus to modern prosthetic repairs. The rapid evolution of anatomical, physiological and pathogenetic concepts has involved the rapid evolution of surgical treatments. From hernia sack cauterization to sack ligation, posterior wall repair (Bassini), and prosthetic reinforcement there has been an evident improvement in surgical treatment results that has stimulated surgeons to find new technical solutions over time. The introduction of prosthetic repair, the laparoscopic revolution, the impact of local anesthesia and the diffusion of day surgery have been the main advances of the last 50 years. Searching for new gold standards, the introduction of new devices has also led to new complications and problems. Research of the last 10 years has been directed to overcome prosthetic repair complications, introducing every year new meshes and materials. Lightweight meshes, composite meshes and biologic meshes are novelties of the last few years. We also take a look at future trends.

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

Background

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

Methods

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

Results

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

Conclusion

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

Surgical relevance

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

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

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

Rectus abdominis muscle malignant fibrous histiocytoma causing a large abdominal wall defect: reconstruction with biological mesh

Malignant fibrous histiocytoma (MFH) is a common soft tissue sarcoma usually involving limbs and retroperitoneum. MFH of the rectus abdominis muscle is extremely rare. Surgery in similar cases leads to large abdominal wall defects needing reconstruction. Biological and synthetic laminar absorbable prostheses are available for the repair of hernia defects in the abdominal wall. They share the important feature of being gradually degraded in the host, resulting the formation of a neotissue. We herein report the case of an 84-year-old man with MFH of the rectus abdominis muscle which was resected and the large abdominal wall defect was successfully repaired with a biological mesh.

Evaluation of a porcine dermal collagen (permacol) implant for abdominal wall reconstruction in a pediatric multitrauma patient

The presence of a contaminated surgical field in abdominal wall defects caused by trauma presents a challenge for surgeons. Both primary suture and synthetic meshes are strongly discouraged as surgical treatments in such cases. We describe the use of a porcine dermal collagen (Permacol) implant in an eight-year-old patient with multiple injuries. Three months after discharge, the child remains well with good cosmetic results. He is free of pain and has returned to full activity levels with complete wound closure and without any evidence of residual hernia. In conclusion, our experience indicates that the use of Permacol can be considered an efficient technique for reconstructing an infected abdominal wall defect of a pediatric multitrauma patient.

Porcine dermis implants in soft-tissue reconstruction: current status

Soft-tissue reconstruction for a variety of surgical conditions, such as abdominal wall hernia or pelvic organ prolapse, remains a challenge. There are numerous meshes available that may be simply categorized as either synthetic or biologic. Within biologic meshes, porcine dermal meshes have come to dominate the market. This review examines the current evidence for their use and the limitations of knowledge. Although there is increasing evidence to support their safety, long-term follow-up studies that support their efficacy are lacking. Numerous clinical trials that remain ongoing may help elucidate their precise role in soft-tissue reconstruction.

A retrospective study evaluating the use of Permacol™ surgical implant in incisional and ventral hernia repair

BACKGROUND

The outcome of incisional and ventral hernia repair depends on surgical technique, patient, and material. Permacol™ surgical implant (crosslinked porcine collagen) has been used for over a decade; however, there are few data on outcomes. This study is the largest retrospective multinational study to date to evaluate outcomes with Permacol™ surgical implant in the repair of incisional and ventral hernias.

METHODS

Data were collected retrospectively on 343 patients treated for 213 incisional and 130 ventral hernias. Data evaluated included patient demographics, wound classification, surgical technique, morbidity, and recurrence rates.

RESULTS

Median follow-up time was 649 days (max: 2857), median age 57 years (range 23-91), and BMI 32 kg/m(2) (range 17.6-77.8). Two or more comorbidities were present in 70% of patients. Open surgery was performed in 220 (64%) patients. Permacol™ surgical implant was used as an underlay (250), sublay (39), onlay (37), or inlay (17). Surgical techniques included component separation (89; 25.9%), modified Stoppa technique (197; 57.4%), and Rives-Stoppa (17; 5.0%). CDC Surgical Wound Classification was Class I (190), Class II (103), Class III (28), and Class IV (22). Complications were seen in 40.5% (139) of the patients, with seroma (19%) and wound infection (15%) as the most common. Mesh removal occurred in 1 (0.3%) patient. Kaplan-Meier analysis demonstrated that the probabilities for hernia recurrence at one, two, and three years were 5.8%, 16.6%, and 31.0%, respectively.

CONCLUSIONS

Permacol™ surgical implant was shown to be safe with relatively low rates of hernia recurrence.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01214252 (http://www.clinicaltrials.gov).

Fascia lata allografts as biological mesh in abdominal wall repair: preliminary outcomes from a retrospective case series

BACKGROUND

The use of biological meshes in management of infected abdominal hernias or in abdominal fields at high risk of infection (potentially contaminated or with relevant comorbidities) is well established. Available products include xenogenic patches or decellularized dermal allografts. Despite their biomechanical features, banked fascial allografts have not been investigated yet in this setting. The authors evaluated the safety and effectiveness of banked fascia lata allografts as biological meshes in abdominal wall repair.

METHODS

A consecutive series of patients affected by abdominal wall defects and who were candidates for repair by means of a biological mesh and treated in the authors' institution with banked fascia lata allografts were reviewed retrospectively. Data from clinical and instrumental follow-up evaluations up to 48 months (average, 23 months) were analyzed.

RESULTS

Twenty-one patients (aged 1 to 86 years) with abdominal wall defects resulting from traumatic (n = 1), neoplastic (n = 6), or multiple previous laparotomies (n = 14) were treated from January of 2008 to October of 2012. Operations had no relevant postoperative complications. At clinical/instrumental follow-up examinations, no major signs of recurrence, laxity, infection of grafts, or other related pathologic symptoms were recorded. Three patients suffered from temporary minor complications (e.g., wound seroma, partial cutaneous dehiscence). At instrumental (computed tomographic scan or magnetic resonance imaging) evaluations, the neofascial tissue appeared stable until medium-term follow-up (3 to 6 months), later being gradually degraded and apparently replaced by host tissue.

CONCLUSION

According to limited preliminary outcomes, banked fascia lata allografts seem to provide a biocompatible, safe, and effective alternative to other biological meshes.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

WSES guidelines for emergency repair of complicated abdominal wall hernias

Emergency repair of complicated abdominal hernias is associated with poor prognosis and a high rate of post-operative complications.A World Society of Emergency Surgery (WSES) Consensus Conference was held in Bergamo in July 2013, during the 2nd Congress of the World Society of Emergency Surgery with the goal of defining recommendations for emergency repair of abdominal wall hernias in adults. This document represents the executive summary of the consensus conference approved by a WSES expert panel.

Collagen-Based Substrates with Tunable Strength for Soft Tissue Engineering

Through the use of mechanical reinforcement of collagen matrices, mechanically strong and compliant 3D tissue mimetic scaffolds can be generated that act as scaffolds for soft tissue engineering. Collagen has been widely used for the development of materials for repair, augmentation or replacement of damaged or diseased tissue. Herein we describe a facile method for the layer-by-layer fabrication of robust planar collagen fiber constructs. Collagen gels cast in a phosphate buffer were dried to form dense collagen mats. Subsequent gels were layered and dried atop mats to create multilayer constructs possessing a range of tunable strengths (0.5 - 11 MPa) and stiffness (1 - 115 MPa). Depending on processing conditions and crosslinking of constructs, strain to failure ranged between 9 to 48%. Collagen mats were constructed into hernia patches that prevented hernia recurrence in Wistar rats.

Staged management of the open abdomen and enteroatmospheric fistulae using split-thickness skin grafts

BACKGROUND

Management of the open abdomen with polyglactin 910 mesh followed by split-thickness skin grafts allows safe, early closure of abdominal wounds. This technique can be modified to manage enteroatmospheric fistulae. Staged ventral hernia is performed in a less inflamed surgical field.

METHODS

A retrospective review was performed of 59 consecutive patients who underwent abdominal skin grafting for open abdominal wounds from 2001 to 2011.

RESULTS

The median length of follow-up was 215 days. Thirty-one percent of patients presented with preexisting enteroatmospheric fistulae, and 41% required polyglactin 910 mesh placement before skin grafting. Partial or complete skin graft failure occurred in 7 patients. Four patients required repeat skin grafting. All patients ultimately achieved abdominal wound closure, and none developed de novo fistulae.

CONCLUSIONS

With proper technique, skin grafting of the open abdomen with a planned ventral hernia repair is a safe and effective alternative to delayed primary closure.

The in vivo evaluation of tissue-based biomaterials in a rat full-thickness abdominal wall defect model

Hernias are defects in which an anatomical fascia is breached resulting in ectopic positioning of an organ into an orifice which routinely does not contain it. Intervention often involves repositioning translocated organs and repair of damaged fascia using exogenous grafts. Despite hernia prevalence, repairs can still fail due to postoperative complications, such as chronic pain and decreased mobility. This study compared repair capacities and characterized the foreign body response elicited by a number of hernia repair grafts to deduce their bulk inflammatory properties while also concluding the point in their fabrication when these are inferred. Materials derived from human dermis (Alloderm(®) ), porcine dermis (Permacol™, patch A, patch D and Strattice(®) ), porcine small-intestinal submucosa (Surgisis™) and a synthetic (multifilament Surgipro™) were implanted into a rat full-thickness abdominal wall excision model, incubated for up to 2 years and characterized histopathologically. Surgisis™ resorbed the fastest of the materials tested (1-3 months) resulting in a mechanically stable parietal peritoneum. Decellularization using sodium dodecyl sulfate (patch A) stimulated a large early inflammatory response which ultimately may have contributed to increased resorption of porcine dermal matrix however the remaining materials typically persisted throughout the 2-year incubation. Cross-linking porcine dermis using 1,6-hexamethylene disocyanate (vs. an identical noncross-linked counterpart) showed no difference in cell recruitment or material integration over 2 years. Typically Strattice(®) and Alloderm(®) recruited larger early populations of cells than Permacol™; however, over extended periods of time in vivo this response normalized.

Porcine incisional hernia model: Evaluation of biologically derived intact extracellular matrix repairs

We compared fascial wounds repaired with non-cross-linked intact porcine-derived acellular dermal matrix versus primary closure in a large-animal hernia model. Incisional hernias were created in Yucatan pigs and repaired after 3 weeks via open technique with suture-only primary closure or intraperitoneally placed porcine-derived acellular dermal matrix. Progressive changes in mechanical and biological properties of porcine-derived acellular dermal matrix and repair sites were assessed. Porcine-derived acellular dermal matrix–repaired hernias of additional animals were evaluated 2 and 4 weeks post incision to assess porcine-derived acellular dermal matrix regenerative potential and biomechanical changes. Hernias repaired with primary closure showed substantially more scarring and bone hyperplasia along the incision line. Mechanical remodeling of porcine-derived acellular dermal matrix was noted over time. Porcine-derived acellular dermal matrix elastic modulus and ultimate tensile stress were similar to fascia at 6 weeks. The biology of porcine-derived acellular dermal matrix–reinforced animals was more similar to native abdominal wall versus that with primary closure. In this study, porcine-derived acellular dermal matrix–reinforced repairs provided more complete wound healing response compared with primary closure.

Outcome of Abdominal Wall Hernia Repair with Permacol™ Biologic Mesh

The use of biologic mesh in abdominal wall operations has gained popularity despite a paucity of outcome data. We aimed to review the experience of a large healthcare organization with Permacol™. A retrospective study was conducted of patients who underwent abdominal hernia repair with Permacol™ in 14 Southern California hospitals. One hundred ninety-five patients were analyzed over a 4-year period. Operations included ventral/incisional hernia repairs, ostomy closures, parastomal hernia repairs, and inguinal hernia repairs. In 50 per cent of the patients, Permacol™ was used to reinforce a primary fascial repair and in 50 per cent as a fascial bridge. The overall complication rate was 39.5 per cent. The complication rate was higher in patients with infected versus clean wounds, body mass index (BMI) 40 kg/m2 or greater versus BMI less than 40 kg/m2, in patients with prior mesh repair, and when mesh was used as a fascial bridge. With a mean follow-up of 2.1 years, morbid obesity was associated with a higher recurrence. To date this is the largest study on the use of Permacol™ in abdominal wall hernia repair. In our patient population undergoing heterogeneous operations with a majority of wounds as Class II or higher, use of Permacol™ did not eliminate wound morbidity or prevent recurrence, especially in morbidly obese patients.

Cellular response to a novel fetal acellular collagen matrix: implications for tissue regeneration

Introduction. PriMatrix (TEI Biosciences Inc., Boston, MA, USA) is a novel acellular collagen matrix derived from fetal bovine dermis that is designed for use in partial- and full-thickness wounds. This study analyzes the cellular response to PriMatrix in vivo, as well as the ability of this matrix to facilitate normal tissue regeneration. Methods. Five by five mm squares of rehydrated PriMatrix were implanted in a subcutaneous fashion on the dorsum of wild-type mice. Implant site tissue was harvested for histology, immunohistochemistry (IHC), and flow cytometric analyses at multiple time points until day 28. Results. PriMatrix implants were found to go through a biological progression initiated by a transient infiltrate of inflammatory cells, followed by mesenchymal cell recruitment and vascular development. IHC analysis revealed that the majority of the implanted fetal dermal collagen fibers persisted through day 28 but underwent remodeling and cellular repopulation to form tissue with a density and morphology consistent with healthy dermis. Conclusions. PriMatrix implants undergo progressive in vivo remodeling, facilitating the regeneration of histologically normal tissue through a mild inflammatory and progenitor cell response. Regeneration of normal tissue is especially important in a wound environment, and these findings warrant further investigation of PriMatrix in this setting.

Clinical outcomes of biologic mesh: where do we stand?

After review and evaluation of current clinical data, including significant wound complications, a noteworthy failure rate at 1 year, and high product costs, it is difficult to support the continued use of biologic meshes in incisional hernia repair outside of well-designed and rigorously conducted clinical trials. An industry-sponsored, publicly available registry of biologic prosthetic use for ventral hernia repairs is needed. This straightforward mandate, if properly constructed and implemented, would significantly expand knowledge regarding how these intriguing biomaterials are used and their overall clinical efficacy, thus yielding a more robust basis for the continued use of biologic prosthetics in hernia repair than is currently available.

Synthetic or biological mesh use in laparoscopic ventral mesh rectopexy--a systematic review

AIM

Laparoscopic ventral mesh rectopexy (VMR) is a surgical option for internal and external rectal prolapse with low perioperative morbidity and low recurrence rates. Use of synthetic mesh in the pelvis may be associated with complications such as fistulation, erosion and dyspareunia. Biological meshes may avoid these complications, but the long-term outcome is uncertain. Debate continues as to which type of mesh is optimal for laparoscopic VMR.

METHOD

A literature search was performed of electronic databases including MEDLINE, Embase and Scopus (2000-12). Studies describing outcomes relating to the mesh were included for review. Only English language studies were included.

RESULTS

Thirteen observational studies reported the outcome of 866 patients following laparoscopic VMR. Eleven reported the outcome using synthetic mesh with a median follow-up ranging from 7 to 74 months. Two studies reported the outcome with biological mesh with a median follow-up of 12 months. Pooled analysis of the studies demonstrated that 767 patients had a repair with synthetic mesh and 99 with a biological implant. There was no difference in recurrence (3.7 vs 4.0%, P = 0.78) or mesh complications (0.7 vs 0%, P = 1.0%) between synthetic and biological mesh repair.

CONCLUSION

Biological meshes appear to be as effective as synthetic meshes in the short term for laparoscopic VMR. Mesh complication rates are low in both groups. Long-term follow-up is required to ascertain if these findings persist.

Short-term in vivo biological and mechanical remodeling of porcine acellular dermal matrices

The purpose of this study was to assess the biological revitalization and mechanical integrity of Strattice^™ Reconstructive Tissue Matrix, a porcine-derived acellular dermal matrix, in vivo over time. We expanded the traditional subcutaneous model to incorporate biologic matrix scaffolds large enough to allow evaluation of mechanical properties in addition to the assessment of histological changes. Hematoxylin and eosin histology staining was used to evaluate cellular and tissue changes, and a mechanical testing frame was used to measure the ultimate tensile stress and Young’s modulus of the implanted material over time. Cell infiltration and blood vessel formation into the porcine-derived acellular dermal matrix were evident at 2 weeks and increased with implantation time. Mechanical remodeling resulted in an initial decrease in ultimate tensile stress, not associated with cell infiltration, followed by a significant increase in material strength, concurrent with histological evidence of new collagen synthesis. Young’s modulus followed a similar trend.

Abdominal wall defect repair with biological prosthesis in transplanted patients: single center retrospective analysis and review of the literature

The risk of fascial dehiscence, wound infection and incisional hernias in organ recipients is higher. Retrospective analysis of our departments database, checking the last 12 years (2000-2012), and of the literature (1966-2012) were conducted. In our database we found seven patients: five liver (71.4 %), one kidney (14.3 %), one multivisceral (14.3 %); five males (71.4 %), two females (28.6 %). Five (71.4 %) were operated in urgency setting and two in ordinary setting (28.6 %). The mean/median number of laparotomies before the incisional hernia is of 2.1/1 (range 1-5). In five patients swine intestinal submucosa (71.4 %) have been used and in two porcine dermal collagen (28.6 %). The mean/median age was 48.3/52 years (range 18-61). The mean/median body mass index was 26.7/27 (range 19-34). The mean/median for follow-up after intervention was 40.1/33 months (range 50-21). Recurrence rate was 14.3 %. Complication rate was 28.6 %. Adding the present report, the literature reports 70 cases. 20 % of prosthesis have been implanted inlay, 25.7 % underlay, in 5.7 % intraperitoneal and in 48.6 % were not specified. The mean age ranges from 0.7 to 48.3 years. Kidney, liver, pancreas, bowel and multivisceral transplant are reported. Porcine dermal collagen has been implanted in 24.3 %, human dermal collagen in 51.4 % and swine intestinal submucosa in 24.3 %. The immunosuppression regimens comprehend variable associations of tacrolimus, steroids, mycophenolate mofetil, sirolimus, thymoglobulin, azathioprine/basiliximab and daclizumab. The mean follow-up is 16.2 months. The mean complication rate is 9.4 %. Biological prosthesis seems to be useful and safe in abdominal wall repair surgery in transplanted patients.

Porcine dermal collagen (Permacol) for redo bladder exstrophy closure

This report describes the use of a biosynthetic graft (Permacol) derived from porcine dermal collagen to reconstruct the abdominal wall of a 2-year-old boy with classic bladder exstrophy. The child had undergone 2 previous failed attempts at closure.

What would surgeons like from materials scientists?

Surgery involves the repair, resection, replacement, or improvement of body parts and functions and in numerous ways, surgery should be considered human engineering. There are many areas in which surgical materials could be improved, but surgeons are generally unaware of materials available for use, while materials scientists do not know what surgeons require. This article will review some of the areas where surgeons and materials scientists have interacted in the past and will discuss some of the most pressing problems which remain to be solved. These include better implant materials for hernia repair, breast reconstruction, the treatment of diabetes, vascular stenting and reconstruction, and electrical pacing devices. The combination of tissue engineering and nanomaterials has great potential for application to nearly every aspect of surgery. Tissue engineering will allow cells or artificial organs to be grown for specific uses while nanotechnology will help to ensure maximal biocompatibility. Biosensors will be combined with improved electrodes and pacing devices to control impaired neurological functions.

Reconstruction of abdominal wall musculofascial defects with small intestinal submucosa scaffolds seeded with tenocytes in rats

The repair of abdominal wall defects following surgery remains a difficult challenge. Although multiple methods have been described to restore the integrity of the abdominal wall, there is no clear consensus on the ideal material for reconstruction. This study explored the feasibility of in vivo reconstruction of a rat model of an abdominal wall defect with a composite scaffold of tenocytes and porcine small intestinal submucosa (SIS). In the current study, we created a 2×1.5 cm abdominal wall defect in the anterolateral abdominal wall of Sprague-Dawley rats, which were assigned into three groups: the cell-SIS construct group, the cell-free SIS scaffold group, and the abdominal wall defect group. Tenocytes were obtained from the tendons of rat limbs. After isolation and expansion, cells (2×10(7)/mL) were seeded onto the three-layer SIS scaffolds and cultured in vitro for 5 days. Cell-SIS constructs or cell-free constructs were implanted to repair the abdominal wall defects. The results showed that the tenocytes could grow on the SIS scaffold and secreted corresponding matrices. In addition, both scaffolds could repair the abdominal wall defects with no hernia recurrence. In comparison to the cell-free SIS scaffold, the composite scaffold exhibited increased vascular regeneration and mechanical strength. Furthermore, following increased time in vivo, the mechanical strength of the composite scaffold became stronger. The results indicate that the composite scaffold can provide increased mechanical strength that may be suitable for repairing abdominal wall defects.

Massive traumatic abdominal hernia repair with biologic mesh

Traumatic abdominal wall hernias (TAWHs) are rare. They can arise from either high or low impact trauma and can be associated with significant associated injury. We present the case of a 27-year-old male involved in a high-impact road traffic accident resulting in a TAWH. He sustained significant disruption to the abdominal wall and sustained injuries to the thoracic cage. Operative management was undertaken with a porcine dermal collagen mesh, using a bridge technique.

Biological materials in colorectal surgery: current applications and potential for the future

Biological materials are increasingly used in abdominal surgery for ventral, pelvic and perineal reconstructions, especially in contaminated fields. Future applications are multi-fold and include prevention and one-step closure of infected areas. This includes prevention of abdominal, parastomal and pelvic hernia, but could also include prevention of separation of multiple anastomoses, suture- or staple-lines. Further indications could be a containment of infected and/or inflammatory areas and protection of vital implants such as vascular grafts. Reinforcement patches of high-risk anastomoses or unresectable perforation sites are possibilities at least. Current applications are based mostly on case series and better data is urgently needed. Clinical benefits need to be assessed in prospective studies to provide reliable proof of efficacy with a sufficient follow-up. Only superior results compared with standard treatment will justify the higher costs of these materials. To date, the use of biological materials is not standard and applications should be limited to case-by-case decision.

The role of biologic meshes in abdominal wall reconstruction

There are unacceptably high rates of recurrence following surgery for incision hernia repair using suture repair techniques in isolation. As the reconstruction of abdominal walls has expanded with complex surgery, the materials used as adjuncts to support the repair have changed. In the article we review the current use of biologic meshes in abdominal wall reconstruction and the techniques used.

A scientific evidence for the efficacy of biologic implants for soft tissue reconstruction

The challenges and complications arising from abdominal surgery frequently necessitate soft tissue reconstruction or augmentation. Soft tissue repair generally has been revolutionised by the introduction of synthetic meshes, but their use is contra-indicated in contaminated or infected fields. Biologic materials derived from devitalised allo- or xenogeneic tissues have been proposed as a safer alternative to synthetics and provide an extracellular scaffold necessary for the in-growth of new blood vessels and infiltration of native stromal cells. We review the scientific evidence behind commercially available biologic prostheses in relation to the impact of tissue source, manufacturing processes and supplemental cross-linking on in vitro and in vivo (animal model and clinical) performance. Cross-linked meshes exhibit increased resistance to collagenase activity and degradation whilst still allowing tissue in-growth. Mesh durability may be the most important characteristic in determining optimal clinical outcomes, particularly in the context of the increased collagenase activity seen in contaminated or infected fields. Of all the biologic meshes currently available, HDMI cross-linked acellular porcine dermis has been associated with the best clinical outcomes in contaminated or infected fields.

Italian Biological Prosthesis Work-Group (IBPWG): proposal for a decisional model in using biological prosthesis

Introduction

Indications for repair of abdominal hernia are well established and widely diffused. Controversies still exist about the indication in using the different prosthetic materials and principally about the biological ones.

Material and methods

In February 2012, the Italian Biological Prosthesis Work-Group (IBPWG), counting a background of 264 biologic implants, met in Bergamo (Italy) for 1-day meeting with the aim to elaborate a decisional model on biological prosthesis use in abdominal surgery.

Results

A diagram to simplify the decisional process in using biologics has been elaborated.

Conclusion

The present score represents a first attempt to combine scientific knowledge and clinical expertise in order to offer precise indications about the kind of biological mesh to use.