Experimental evaluation of four biologic prostheses for ventral hernia repair

Thoracic wall reconstruction with Collamend® in trauma: report of a case and review of the literature

INTRODUCTION

Despite progress in reconstructive techniques, rebuilding portions of the thorax remains challenging, in particular when large resections, contamination or infection are involved. No other cases of thoracic reconstruction in trauma patients with biological prosthesis have been described since now.

METHODS

We report a case of thoracic reconstruction in highly infected field in a trauma patient. We also performed a literature review about the topic.

CONCLUSION

Collamend® demonstrated its usefulness in thoracic wall reconstruction even in trauma patients and infected fields.

Deepithelialized flap closure: an adjunct to complex ventral hernia repairs

Ventral hernias are a major surgical challenge with complications such as wound separations, infections, and recurrences contributing to patient morbidity. We describe a new adjunctive technique that may be helpful in repairing difficult ventral hernias: it involves using an appropriately chosen, redundant abdominal skin edge that is deepithelialized and used to reinforce the hernia repair. A series of 7 patients aged 23 to 84 years in whom the technique was used is presented. All patients had complete repair of their incisional ventral hernia defects without complications of infection, wound dehiscence, seroma formation, reoperation, or hernia recurrence. Furthermore, patients reported a subjective improvement in performing daily activities. Mean follow-up in this series was 19.2 months, with a range from 15.0 to 26.8 months. Advantages include the redistribution of mechanical tension, reinforcement of the midline site of greatest pressure, elimination of dead space, and staggering of suture lines to prevent direct external contamination of prosthetic material should wound dehiscence occur.

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.

A review of available prosthetic material for abdominal wall repair

Abdominal wall incisional and inguinal hernia repair can call for utilization of implants or prostheses as an alternative to simple suture techniques. The various implants can be synthetic, biologic or mixed: their physicochemical properties condition the mechanical results and the long-term outcome of the repair. The increasing number of available materials allows the surgeon to choose between a wide variety depending on the indication, the site of implantation, the surgical approach and whether the operative field is contaminated or not. With regard to evidence-based medicine, while several synthetic implants have been shown to be superior in efficacy to simple suture, other studies are underway to develop the indications for bioprostheses, in particular in contaminated fields. This review of the literature summarizes the current knowledge on synthetic and biologic implants (physicochemical characteristics, forms, indications).

Veritas® bovine pericardium for immediate breast reconstruction: a xenograft alternative to acellular dermal matrix products

BACKGROUND: The technical advantages in utilizing human acellular dermal matrix (ADM) products as pectoral extenders in immediate breast reconstruction with tissue expanders or implants are well documented in the medical literature. In this study, the authors examine a commonly used biologic xenograft product that has not yet been described in the medical literature for use in immediate breast reconstruction to determine whether a lower overall complication rate is identified compared to published data on ADM products. METHODS: A retrospective multicenter medical record review of data on 54 subjects in 93 tissue expander/implant-based, consecutive, immediate breast reconstructions from three surgeons at different institutions was performed in which Veritas® bovine pericardium was used as the biologic graft material for the pectoral extender. RESULTS: Over a 24-month period with an average of 11-month follow-up, complication rates using Veritas® in breast reconstruction for seroma formation (7.5 %), marginal skin flap necrosis (5.4 %) infection (6.5 %), and capsular contracture (0 %) were found to compare equally or favorably with statistically significant lower overall complications relative to one comparison study and lower rates of marginal skin flap necrosis relative to two comparison studies based upon previously published data from multisurgeon studies using ADM products. CONCLUSIONS: Overall complications were found to be lower with Veritas® than ADM products in comparable multisurgeon studies, though this was found to be statistically significant in only one comparison study. Level of Evidence: Level II, theraputic study.

Effects of collagen prosthesis cross-linking on long-term tissue regeneration following the repair of an abdominal wall defect

Collagen prostheses used to repair abdominal wall defects, depending on their pretreatment (noncross-linked vs. cross-linked), besides repair may also achieve tissue regeneration. We assessed the host tissue incorporation of different bioprostheses using a new tool that combines immunofluorescence confocal microscopy with differential interference contrast images, making it possible to distinguish newly formed collagen. Partial hernial defects in the abdominal wall of rabbits were repaired using cross-linked/noncross-linked bioprostheses. Expanded polytetrafluoroethylene (ePTFE) was used as control. After 14/30/90/180 days of implant, specimens were taken for microscopy, immunohistochemistry, and quantitative-reverse transcription-polymerase chain reaction to determine host tissue ingrowth and collagen I/III protein and 1a1/3a1 gene expression. Shrinkage and stress resistance were also examined. At 14 days, cross-linked prostheses had suffered significantly less shrinkage than ePTFE or noncross-linked prostheses. Significantly higher shrinkage was recorded for ePTFE in the longer term. Microscopy revealed encapsulation of ePTFE by neoformed tissue, while the bioprostheses became gradually infiltrated by host tissue. Noncross-linked prosthesis showed better tissue ingrowth, more intense inflammatory reaction and more rapid degradation than the cross-linked prostheses. At 14 days, cross-linked prostheses induced up-regulated collagen 1a1 and 3a1 gene expression, while noncross-linked only showed increased collagen III protein expression at 90 days postimplant. At 6 months, the tensile strengths of cross-linked prostheses were significantly greater compared with ePTFE. Our findings demonstrate that despite the cross-linked collagen prostheses promoting less tissue ingrowth than the noncross-linked meshes, they became gradually replaced by good quality host tissue and were less rapidly degraded, leading to improved stress resistance in the long term.

Biological implants in sphincter augmentation offer a good short-term outcome after a sphincter repair

AIM

Long-term results of the overlapping sphincter repair (OSR) have been disappointing, attributed to poor tissue quality that deteriorates with time. Biological grafts enforce tissues. The aim was to compare functional outcome and quality of life at 1 year with and without Permacol reinforcement to evaluate short-term benefit.

METHOD

From November 2007 to November 2008, women undergoing OSR using Permacol (group 1, n = 10) under institutional review board approval (safety trial) were age matched with patients from an institutional review board approved database (group 2, n = 10) who underwent the traditional OSR. Permacol mesh was placed under the two overlapped muscles. Group 2 underwent traditional repair. Preoperative and postoperative management of the groups was similar. The Fecal Incontinence Severity Index (FISI), the Cleveland Clinic Incontinence Score (CCFIS) and the Fecal Incontinence Quality of Life (FIQL) scale were used preoperatively and 1 year post-surgery.

RESULTS

No significant differences in demographics, symptom duration, number of vaginal deliveries, comorbidities and symptom severity were noted. Group 2 underwent concomitant procedures. Group 1 reported no complications. Group 2 reported urinary retention and dehiscence. A significant difference was found in preoperative and postoperative FIQL subscales of coping/behaviour between groups. However, comparing the pre and post scores, significant improvements on FISI (P = 0.02), the CCFIS (P = 0.005) and two subscales of FIQL (coping/behaviour, P = 0.02, and embarrassment, P = 0.01) were found in group 1. Patient satisfaction was higher in group 1.

CONCLUSION

Biologic tissue enhancers (Permacol) do not add morbidity. Sphincter augmentation results in significant improvement in continence and quality of life scores compared with the preoperative scores in the short term over traditional repair. Long-term studies are needed to determine if this effect is sustained.

Chest wall reconstruction using implantable cross-linked porcine dermal collagen matrix (Permacol)

BACKGROUND/PURPOSE

Chest wall reconstruction in children is typically accomplished with either primary tissue repair or synthetic mesh prostheses. Primary tissue repair has been associated with high rates of scoliosis, whereas synthetic prostheses necessitate the placement of a permanent foreign body in growing children. This report describes the use of biologic mesh (Permacol; Covidien, Mansfield, MA) as an alternative to both tissue repair and synthetic prostheses in pediatric chest wall reconstruction.

METHODS

A retrospective chart review was performed identifying patients undergoing chest wall reconstruction with biologic mesh at our tertiary referral children's hospital between 2007 and 2011. Data collection included patient demographics, indication for chest wall resection, number of ribs resected, the administration of postoperative radiation, length of follow-up, postoperative complications, and the degree of spinal angulation (preoperatively and at most recent follow-up).

RESULTS

Five patients (age, 9.0-21.7 years; mean, 15.4 years) underwent resection for primary chest wall malignancy followed by reconstruction with biologic mesh (Permacol) during the study period. There were no postoperative mesh-related complications, and none of the patients developed clinically significant scoliosis (follow-up, 1.1-2.6 years; mean 1.9 years).

CONCLUSION

Biologic mesh offers a safe and dependable alternative to both primary tissue repair and synthetic mesh in pediatric patients undergoing chest wall reconstruction.

Use of permacol in parietal and general surgery: a bibliographic review

BACKGROUND

The use of synthetic meshes on infected incisional hernias often fails and is therefore contraindicated. Biological meshes offer a novel solution. Among them, Permacol requires a bibliographic analysis of its efficacy and tolerance.

DESIGN

A bibliographic analysis was carried out on the efficacy and tolerance of Permacol in parietal and general surgery.

RESULTS

A total of 22 publications described the use of Permacol in digestive surgery. The advantages of Permacol would be usability in contaminated surgical fields, biocompatibility, no erosion of intestinal wall, and less risk of adhesions. The main drawback of Permacol is its high cost.

CONCLUSION

Even so, Permacol can play an important part in the short-term management of complex or contaminated abdominal wall defects. The lack of long-term studies and the high cost of the implant call for a medical cost-effectiveness assessment to determine the indications for Permacol in parietal and general surgery.

Current strategies and future perspectives for intraperitoneal adhesion prevention

INTRODUCTION

The formation of peritoneal adhesions still is a relevant clinical problem after abdominal surgery. Until today, the most important clinical strategies for adhesion prevention are accurate surgical technique and the physical separation of traumatized serosal areas. Despite a variety of barriers which are available in clinical use, the optimal material has not yet been found.

DISCUSSION

Mesothelial cells play a crucial physiological role in friction less gliding of the serosa and the maintenance of anantiadhesive surface. The formation of postoperative adhesions results from a cascade of events and is regulated by various cellular and humoral factors. Therefore, optimization or functionalization of barrier materials by developments interacting with this cascade on a structural or pharmacological level could give an innovative input for future strategies in peritoneal adhesion prevention. For this purpose, the proper understanding of the formal pathogenesis of adhesion formation is essential. Based on the physiology of the serosa and the pathophysiology of adhesion formation, the available barriers in current clinical practice as well as new innovations are discussed in the present review.

[Biological implants in abdominal wall hernia surgery]

Permanent synthetic materials are currently of choice for abdominal wall hernia repair. However, they are not ideal as short- and long-term complications with these have been reported. Extracellular matrix-derived biological implants (EMDBI) have emerged as a result of research and development into new materials. Several types of EMDBI have appeared in the last few years, each with its own manufacture characteristics and different from the rest. The current panorama of the xenogeneic EMDBI available in Spain is analysed, their complications, the unknown factors arising in the long-term, and the clinical experience available on incisional and inguinal hernias.

A review of patch options in the repair of congenital diaphragm defects

Repair of congenital diaphragmatic hernia (CDH) continues to pose a dilemma for the pediatric surgeon. While the management of CDH has evolved from surgical urgency to delayed repair after medical optimization with substantial improvements in mortality, morbidity continues to perplex clinicians. Significant morbidity occurs with recurrence, re-recurrence and complications such as obstructions, principally with mesh repair. When primary closure is not possible, mesh repair is indicated. While there are several non-absorbable prosthetic, absorbable biosynthetic and composite mesh types available, the ideal mesh remains elusive. In this article, we reviewed the current materials, reported advantages, and animal and clinical studies of non-absorbable prosthetic, absorbable biosynthetic and composite mesh. However, adequate comparative data are lacking, leaving a wide void for future animal models and clinical studies.

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.

Durability of biologic implants for use in hernia repair: a review

In the past 10 years, hernia repair has evolved from primarily using suture closure to using mesh repair. Synthetic mesh implants were the initial gold standard, but the rate of complications such as infection, adhesions, and erosion was higher with synthetics than has been observed with newer biologic implants. As efforts to develop the ideal implant continue, the advantages of biologics for hernia and other soft-tissue repair become increasingly apparent. Animal-sourced biologics have the potential advantage over human dermis of being more amenable to standardization, and porcine dermal collagen architecture closely resembles that of human dermis. Cross-linking the collagen adds strength and durability to the implant that facilitates healing of surgical wounds, just as endogenous collagen, which is cross-linked, has innate durability that enhances natural wound healing. This review defines and assesses durability of the acellular collagen (biologic) implant options available for hernia repair. The factors that affect wound healing-and hernia repair--are summarized. Additionally, the particular features that enhance durability are described, and durability-related clinical outcomes discussed in the literature are cited to aid clinicians in making informed surgical choices.

Acellular dermal matrix: general principles for the plastic surgeon

Acellular dermal matrix (ADM) is a recently-developed, biologically-derived product with many useful applications in plastic surgery, in both cosmetic and reconstructive procedures. While the use of ADM initially outpaced quality literature, within the past 10 years the literature on ADM has rapidly expanded. Some of these data show promising results in treating historically-challenging problems within our field; thus, an effort to clarify and summarize existing work with ADM is indicated. While subsequent articles in this supplement focus on specific applications, this article provides a general overview of the biology of, applications for, and existing literature on ADM.

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.

Abdominal ventral hernia repair with current biological prostheses: an experimental large animal model

Biologic prostheses have emerged to address the limitations of synthetic materials for ventral hernia repairs; however, they lack experimental comparative data. Fifteen swine were randomly assigned to 1 of 3 bioprosthetic groups (DermaMatrix, AlloDerm, and Permacol) after creation of a full thickness ventral fascial defect. At 15 weeks, host incorporation, hernia recurrence, adhesion formation, neovascularization, inflammation, and biomechanical properties were assessed. No animals had hernia recurrence or eventration. DermaMatrix and Alloderm implants demonstrated more adhesions, greater inflammatory infiltration, and more longitudinal laxity, but near identical neovascularization and tensile strength to Permacol. We found that porcine acellular dermal products (Permacol) contain following essential properties of an ideal ventral hernia repair material: low inflammation, less elastin and stretch, lower adhesion rates and cost, and more contracture. The addition of lower cost xenogeneic acellular dermal products to the repertoire of available acellular dermal products demonstrates promise, but requires long-term clinical studies to verify advantages and efficacy.

Evaluation of human acellular dermis versus porcine acellular dermis in an in vivo model for incisional hernia repair

Incisional hernias commonly occur following abdominal wall surgery. Human acellular dermal matrices (HADM) are widely used in abdominal wall defect repair. Xenograft acellular dermal matrices, particularly those made from porcine tissues (PADM), have recently experienced increased usage. The purpose of this study was to compare the effectiveness of HADM and PADM in the repair of incisional abdominal wall hernias in a rabbit model. A review from earlier work of differences between human allograft acellular dermal matrices (HADM) and porcine xenograft acellular dermal matrices (PADM) demonstrated significant differences (P < 0.05) in mechanical properties: Tensile strength 15.7 MPa vs. 7.7 MPa for HADM and PADM, respectively. Cellular (fibroblast) infiltration was significantly greater for HADM vs. PADM (Armour). The HADM exhibited a more natural, less degraded collagen by electrophoresis as compared to PADM. The rabbit model surgically established an incisional hernia, which was repaired with one of the two acellular dermal matrices 3 weeks after the creation of the abdominal hernia. The animals were euthanized at 4 and 20 weeks and the wounds evaluated. Tissue ingrowth into the implant was significantly faster for the HADM as compared to PADM, 54 vs. 16% at 4 weeks, and 58 vs. 20% for HADM and PADM, respectively at 20 weeks. The original, induced hernia defect (6 cm²) was healed to a greater extent for HADM vs. PADM: 2.7 cm² unremodeled area for PADM vs. 1.0 cm² for HADM at 20 weeks. The inherent uniformity of tissue ingrowth and remodeling over time was very different for the HADM relative to the PADM. No differences were observed at the 4-week end point. However, the 20-week data exhibited a statistically different level of variability in the remodeling rate with the mean standard deviation of 0.96 for HADM as contrasted to a mean standard deviation of 2.69 for PADM. This was significant with P < 0.05 using a one tail F test for the inherent variability of the standard deviation. No significant differences between the PADM and HADM for adhesion, inflammation, fibrous tissue or neovascularization were noted.

A review of available prosthetics for ventral hernia repair

OBJECTIVE

To review mesh products currently available for ventral hernia repair and to evaluate their efficacy in complex repair, including contaminated and reoperative fields.

BACKGROUND

Although commonly referenced, the concept of the ideal prosthetic has never been fully realized. With the development of newer prosthetics and approaches to the ventral hernia repair, many surgeons do not fully understand the properties of the available prosthetics or the circumstances that warrant the use of a specific mesh.

METHODS

A systematic review of published literature from 1951 to June of 2009 was conducted to identify articles relating to ventral hernia repairs and the use of prosthetics in herniorrhaphy.

RESULTS

Important differences exist between the synthetics, composites, and biologic prosthetics used for ventral hernia repair in terms of mechanics, cost, and the ideal situation in which each should be used.

CONCLUSIONS

The use of synthetic mesh remains an appropriate solution for most ventral hernia repairs. Laparoscopic ventral hernia repair has created a niche for both expanded polytetrafluoroethylene and composite mesh, as they are suited to intraperitoneal placement. Preliminary studies have demonstrated that the newer biologic prosthetics are reasonable options for hernia repair in contaminated fields and for large abdominal wall defects; however, more studies need to be done before advocating the use of these biologics in other settings.

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.

Adhesive performance of biomimetic adhesive-coated biologic scaffolds

Surgical repair of a discontinuity in traumatized or degenerated soft tissues is traditionally accomplished using sutures. A current trend is to reinforce this primary repair with surgical grafts, meshes, or patches secured with perforating mechanical devices (i.e., sutures, staples, or tacks). These fixation methods frequently lead to chronic pain and mesh detachment. We developed a series of biodegradable adhesive polymers that are synthetic mimics of mussel adhesive proteins (MAPs), composed of 3,4-dihydroxyphenylalanine (DOPA)-derivatives, polyethylene glycol (PEG), and polycaprolactone (PCL). These polymers can be cast into films, and their mechanical properties, extent of swelling, and degradation rate can be tailored through the composition of the polymers as well as blending with additives. When coated onto a biologic mesh used for hernia repair, these adhesive constructs demonstrated adhesive strengths significantly higher than fibrin glue. With further development, a precoated bioadhesive mesh may represent a new surgical option for soft tissue repair.

Comparison of Surgisis, AlloDerm, and Vicryl Woven Mesh grafts for abdominal wall defect repair in an animal model

BACKGROUND

Surgisis and AlloDerm, two biosynthetic materials, have been previously used with success in abdominal wall repairs in the setting of contaminated fields. Historically, Vicryl Woven Mesh, a synthetic material, has also been used in such settings as a temporary bridge for abdominal wall reconstruction. This study compares Surgisis and AlloDerm with Vicryl Woven Mesh with respect to tensile strength, collagen remodeling, and neovascularization using a rat hernia model.

METHODS

A prospective randomized trial of 54 Sprague-Dawley rats were assigned to the Surgisis, AlloDerm, or Vicryl Woven Mesh group with baseline, 30-day, and 60-day end points. A 1.5-cm x 5.0-cm defect was created in the right abdominis rectus muscle and repaired with an underlay bridge graft using the different treatment materials. Tensile strength was measured using an Instron tensiometer. Histologic specimens were evaluated for neovascularization, collagen deposition, and collagen organization at the 30- and 60-day time points.

RESULTS

Surgisis had significantly greater tensile strength compared to Vicryl Woven Mesh at the baseline time point (0.142 vs. 0.091 MPa, p < 0.05). There were no differences between groups tensile strength at 30 or 60 days postoperatively. The Vicryl Woven Mesh and AlloDerm groups showed increases in tensile strength at 30 days postoperatively versus baseline (p < 0.05). Vicryl Woven Mesh, Surgisis, and AlloDerm all showed increases in tensile strength at 60 days postoperatively compared to 30 days postoperatively and at baseline (p < 0.05). Surgisis and AlloDerm had significantly greater (p < 0.05) amounts of collagen deposition and organization at 30 and 60 days compared to Vicryl Woven Mesh. There was no significant difference between AlloDerm and Surgisis with respect to collagen deposition and organization. Surgisis and AlloDerm showed a significantly greater amount (p < 0.05) of neovascularization than Vicryl Woven Mesh at both time points. In addition, Surgisis had a significantly greater amount (p < 0.05) of neovascularization than AlloDerm at both 30 and 60 days.

CONCLUSION

Surgisis has increased baseline tensile strength compared to Vicryl Woven Mesh. Tensile strength in Vicryl Woven Mesh is equal to biosynthetic grafts after tissue incorporation. Biosynthetic grafts showed superior collagen deposition and organization. Surgisis mesh showed increased neovascularization over both AlloDerm and Vicryl Woven Mesh.

Visceral adhesions to hernia prostheses

PURPOSE

To report our experience with abdominal adhesion formation to various synthetic and biologic prosthetic materials in a rat ventral hernia model.

METHODS

A total of 14 prostheses, nine synthetic, four biologic, and one bioresorbable, were evaluated in the rat. Two synthetic prostheses had bioresorbable coatings and one consisted of synthetic and bioresorbable materials woven together. The model involved the removal from the midline of a 2.5 x 2.5-cm segment of full-thickness ventral abdominal wall with the test prosthetic material sewed into the defect, thus, exposing the viscera directly to one surface of the prosthesis. There were four or more rats in each group. Adhesions were assessed at autopsy 7 days after operation or later. The results were expressed as the percentage area of prosthesis surface involved.

RESULTS

All 14 of the tested prosthetic materials induced adhesions. Vicryl Mesh and the four biologic varieties had lesser overall adhesion coverage than the bare synthetic prostheses. Sepramesh developed the least adhesion coverage (15%). The two synthetic materials with bioresorbable coatings had smaller areas involved compared to bare synthetic prostheses.

CONCLUSIONS

All of the tested prostheses attracted adhesions. Biologic prostheses had smaller areas of coverage compared to synthetic prostheses. Barrier surfaces on synthetic meshes were associated with a much lesser extent of adhesion involvement.

Short-term outcomes with the use of bioprosthetics for the management of parastomal hernias

PURPOSE

This study was undertaken to determine the safety and short-term outcomes using bioprosthetics for the management of parastomal hernias.

METHODS

A retrospective review of prospectively collected data for all of the patients who underwent repair of a parastomal hernia was conducted.

RESULTS

Between April 2004 and September 2007, 20 consecutive patients had 22 parastomal hernias repaired through a midline incision using a bioprosthetic with the stoma entering the abdomen lateral to the graft. A colostomy was present in 17 patients; an ileostomy was present in 3 patients. All of the patients had parastomal hernia-related complications. Postoperatively there were no infections of the midline wound or the prosthetic, and none of the grafts were removed. There were 4 seromas (40%) that required aspiration in the 10 procedures performed before the routine placement of a drain. No incisional hernias have developed in the midline wound. There have been 2 (9%) recurrent parastomal hernias on physical examination at a median follow-up of 18 months (range, 12-54).

CONCLUSIONS

These data suggest that bioprosthetics are safe and are effective in the short term for the repair of parastomal hernias.

Porcine dermal collagen (Permacol) for chest and abdominal wall reconstruction in thoraco-omphalopagus conjoined twin separation

Each set of conjoined twins presents a unique challenge, which centers on the ability to separate and if necessary reconstruct shared organs and to achieve subsequent skin cover of the often very large residual defect after completion of the separation. This report describes the use of a bioprosthetic Permacol derived from porcine dermal collagen to reconstruct the chest and abdominal wall.

Morphological and mechanical characteristics of the reconstructed rat abdominal wall following use of a wet electrospun biodegradable polyurethane elastomer scaffold

Although a variety of materials are currently used for abdominal wall repair, general complications encountered include herniation, infection, and mechanical mismatch with native tissue. An approach wherein a degradable synthetic material is ultimately replaced by tissue mechanically approximating the native state could obviate these complications. We report here on the generation of biodegradable scaffolds for abdominal wall replacement using a wet electrospinning technique in which fibers of a biodegradable elastomer, poly(ester urethane)urea (PEUU), were concurrently deposited with electrosprayed serum-based culture medium. Wet electrospun PEUU (wet ePEUU) was found to exhibit markedly different mechanical behavior and to possess an altered microstructure relative to dry processed ePEUU. In a rat model for abdominal wall replacement, wet ePEUU scaffolds (1x2.5 cm) provided a healing result that developed toward approximating physiologic mechanical behavior at 8 weeks. An extensive cellular infiltrate possessing contractile smooth muscle markers was observed together with extensive extracellular matrix (collagens, elastin) elaboration. Control implants of dry ePEUU and expanded polytetrafluoroethylene did not experience substantial cellular infiltration and did not take on the native mechanical anisotropy of the rat abdominal wall. These results illustrate the markedly different in vivo behavior observed with this newly reported wet electrospinning process, offering a potentially useful refinement of an increasingly common biomaterial processing technique.

Management of Complex Abdominal Wall Defects Using Acellular Porcine Dermal Collagen

Multiple techniques have been used for the repair of complex abdominal wall defects after recurrent incisional hernias with varying rates of success. Primary repair has been associated with high recurrence rates, and prosthetic mesh placement is contraindicated in contaminated surgical fields. The development of biologic prostheses has changed the approach to these difficult problems. This study evaluates the management of complex abdominal wall defects using acellular porcine dermal collagen. Between August 2006 and May 2007, 18 patients underwent abdominal wall reconstruction for complex defects with acellular porcine dermal collagen (CollaMend™; Bard Inc., Warwick, RI). Patient demographics, preoperative risk factors, previous herniorrhaphy attempts, postoperative complications, recurrences, and long-term results were retrospectively reviewed. Records were reviewed at a mean follow up of 7.3 months; the recurrence rate was 44.4 per cent. A total of 38.9 per cent (seven of 18) developed a postoperative wound complications, including infection in 22.2 per cent (four of 18). All of the patients with infection required prosthesis removal as a result of encapsulation rather than incorporation of the biologic prosthesis. Acellular porcine dermal collagen has the potential for reconstruction of abdominal wall defects with postoperative wound occurrences comparable with other biologic materials. Encapsulation of the material was a major problem in cases with wound infection that required graft removal rather than local wound measures. Hernia recurrence and dehiscence of the graft were problems in noncompromised surgical fields.

Major Complications Associated With Xenograft Biologic Mesh Implantation in Abdominal Wall Reconstruction

Background. There is limited research for xenograft biologic mesh performance in the setting of infection despite widespread use and significant associated costs. Design. The authors retrospectively reviewed an FDA database for reported xenograft adverse events (AEs). All meshes were used in the setting of abdominal wall reconstruction from 1997 to 2008. Results. The authors identified 150 AEs. Permacol and Collamend comprised 75% (n = 112) of reported cases. Main AEs included acute mechanical failure (42%; n = 63), mesh disintegration (32%; n = 48), and poor mesh integration (13%; n = 20); 80% of cases were described as infected, and nearly 90% of AEs required reoperation. Conclusions . Major complications are reported to the FDA for xenograft biologic meshes. Cross-linked meshes had the most AE reports to the FDA. The intrinsic properties of meshes and how they relate to infection-related outcomes are poorly understood. The findings from this FDA database review point toward a need to carefully evaluate these products.