A model for sidewall adhesions in the rabbit: reduction by an absorbable barrier

Safety and tissue remodeling assay of small intestinal submucosa meshes using a modified porcine surgical hernia model

In studies to date, meshes based on extracellular matrix (ECM) have been extensively used in clinical applications. Unfortunately, little is known about the function of the immunogenic residual, absorbable profile during the tissue repair process. Moreover, there needs to be a recognized preclinical animal model to investigate the safety and efficacy of extracellular matrix meshes. Herein, we designed and fabricated a kind of SIS mesh followed by a scanned electron micrograph characterization and tested α-Gal antigen clearance rate and DNA residual. In order to prove the biocompatibility of the SIS mesh, cell viability, chemotaxis assay and local tissue reaction were assessed by MTT and RTCA cytotoxicity test in vitro as well as implantation and degradation experiments in vivo. Furthermore, we developed a stable preclinical animal model in the porcine ventral hernia repair investigation, which using laparoscopic plus open hybridization method to evaluate tissue adhesion, explant mechanical performance, and histologic analysis after mesh implantation. More importantly, we established a semi-quantitative scoring system to examine the ECM degradation, tissue remodeling and regeneration in the modified porcine surgical hernia model for the first time. Our results highlight the application prospect of the improved porcine ventral hernia model for the safety and efficacy investigation of hernia repair meshes.

[Safety of mesh with fluoropolymer coating during intra-abdominal placement in large animals: results of the pilot study]

OBJECTIVE

When performing laparoscopic intraperitoneal hernioplasty (IPOM), endoprostheses made of fluoropolymers are often used. However, there is no data in the literature on the intra-abdominal use of inexpensive polyester prostheses with a fluoropolymer coating compared to composite implants. Thus, the aim of the pilot study was a preliminary assessment of the safety profile of FTOREX mesh endoprostheses during intra-abdominal placement in large animals.

MATERIAL AND METHODS

6 endoprostheses were installed laparoscopically intraperitoneally in each of the 3 pigs: 1) FTOREX; 2) FTOREX with a layer of carboxymethylcellulose; 3) REPEREN-16-2; 4) SYMBOTEX; 5) VENTRALIGHT ST; 6) decellularized pork peritoneum. Fixation was performed with a herniator, transfascial sutures were not used. Relaparoscopy was performed after 45 days, and withdrawal from the experiment was performed after 90 days. Performance characteristics, signs of deformation and retraction, parameters of spike formation were evaluated.

RESULTS

All the animals survived, no complications were observed. There were no clinical manifestations or behavioral reactions indicating the presence of adhesions. The most convenient to use were the SYMBOTEX and FTOREX implants (5.0 points each). By the end of the experiment, deformation and retraction were noted in both variants of the FTOREX implants and the REPEREN prosthesis. These changes were completely absent only when using the SYMBOTEX endoprosthesis. According to the number of implants with adhesions, by the end of the observation, both variants of FTOREX prostheses occupied an intermediate position between the Reference (the worst indicator) and VENTRALIGHT ST (the best indicator). However, both FTOREX endoprostheses showed the best performance among all implants in the integral assessment of adhesions, as well as in terms of parameters such as the area and appearance of adhesions, and in terms of the strength of the joints, they were second only to the VENTRALIGHT ST endoprosthesis (0.67 vs. 0.5 points). During the study, there was no reliable dependence of deformation, retraction and adhesion formation indicators on the type of implant.

CONCLUSION

The results of the pilot study showed that all the implants used did not cause any clinically significant adverse reactions or complications. FTOREX endoprostheses with their intraperitoneal installation have anti-adhesive properties that are not inferior to VENTRALIGHT ST or SYMBOTEX composite implants. However, having less rigidity, they are more often deformed and subjected to retraction.

Ultra-Fine Polyethylene Hernia Meshes Improve Biocompatibility and Reduce Intraperitoneal Adhesions in IPOM Position in Animal Models

(1) Introduction: The intraperitoneal onlay mesh technique (IPOM) is widely used to repair incisional hernias. This method has advantages but suffers from complications due to intraperitoneal adhesion formation between the mesh and intestine. An ideal mesh minimizes adhesions and shows good biocompatibility. To address this, newly developed multifilamentous polyethylene (PET) meshes were constructed from sub-macrophage-sized monofilaments and studied regarding biocompatibility and adhesion formation. (2) Methods: We investigated fine (FPET, 72 filaments, 11 µm diameter each) and ultra-fine multifilament (UFPET, 700 filaments, 3 µm diameter each) polyethylene meshes for biocompatibility in subcutaneous implantation in rats. Adhesion formation was analyzed in the IPOM position in rabbits. Geometrically identical mono-filamentous polypropylene (PP) Bard Soft® PP meshes were used for comparison. Histologic and immune-histologic foreign body reactions were assessed in 48 rats after 7 or 21 days (four mesh types, with two different mesh types per rat; n = 6 per mesh type). Additionally, two different mesh types each were placed in the IPOM position in 24 rabbits to compile the Diamond peritoneal adhesion score after the same timeframes. The biocompatibility and adhesion score differences were analyzed with the Kruskal–Wallis nonparametric statistical test. (3) Results: Overall, FPET and, especially, UFPET showed significantly smaller foreign body granulomas compared to PP meshes. Longer observation periods enhanced the differences. Immunohistology showed no significant differences in the cellular immune response and proliferation. UFPET demonstrated significantly reduced peritoneal adhesion formation compared to all other tested meshes after 21 days. (4) Conclusions: Overall, FPET and, especially, UFPET demonstrated their suitability for IPOM hernia meshes in animal models by improving major aspects of the foreign body reaction and reducing adhesion formation.

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

BACKGROUND

Currently, the lack of consensus on postoperative mesh-tissue adhesion scoring leads to incomparable scientific results. The aim of this study was to develop an adhesion score recognized by experts in the field of hernia surgery.

METHODS

Authors of three or more previously published articles on both mesh-tissue adhesion scores and postoperative adhesions were marked as experts. They were queried on seven items using a modified Delphi method. The items concerned the utility of adhesion scoring models, the appropriateness of macroscopic and microscopic variables, the range and use of composite scores or subscores, adhesion-related complications and follow-up length. This study comprised two questionnaire-based rounds and one consensus meeting.

RESULTS

The first round was completed by 23 experts (82%), the second round by 18 experts (64%). Of those 18 experts, ten were able to participate in the final consensus meeting and all approved the final proposal. From a total of 158 items, consensus was reached on 90 items. The amount of mesh surface covered with adhesions, tenacity and thickness of adhesions and organ involvement was concluded to be a minimal set of variables to be communicated separately in each future study on mesh adhesions.

CONCLUSION

The MEsh Tissue Adhesion scoring system is the first consensus-based scoring system with a wide backing of renowned experts and can be used to assess mesh-related adhesions. By including this minimal set of variables in future research interstudy comparability and objectivity can be increased and eventually linked to clinically relevant outcomes.

A peritoneal defect covered by intraperitoneal mesh prosthesis effects an increased and distinctive foreign body reaction in a minipig model

BACKGROUND

The incidence of incisional hernia is with up to 30% one of the frequent long-term complication after laparotomy. After establishing minimal invasive operations, the laparoscopic intraperitoneal onlay mesh technique (lap. IPOM) was first described in 1993. Little is known about the foreign body reaction of IPOM-meshes, which covered a defect of the parietal peritoneum. This is becoming more important, since IPOM procedure with peritoneal-sac resection and hernia port closing (IPOM plus) is more frequently used.

METHODS

In 18 female minipigs, two out of three Polyvinylidene-fluoride (PVDF) -meshes (I: standard IPOM; II: IPOM with modified structure [bigger pores]; III: IPOM with the same structure as IPOM II + degradable hydrogel-coating) were placed in a laparoscopic IPOM procedure. Before mesh placement, a 2x2cm peritoneal defect was created. After 30 days, animals were euthanized, adhesions were evaluated by re-laparoscopy and mesh samples were explanted for histological and immunohistochemichal investigations.

RESULTS

All animals recovered after implantation and had no complications during the follow-up period. Analysing foreign body reaction, the IPOM II mesh had a significant smaller inner granuloma, compared to the other meshes (IPOM II: 8.4 µm ± 1.3 vs. IPOM I 9.1 µm ± 1.3, p < 0.001). The degradable hydrogel coating does not prevent adhesions measured by Diamond score (p = 0.46). A peritoneal defect covered by a standard or modified IPOM mesh was a significant factor for increasing foreign body granuloma, the amount of CD3+ lymphocytes, CD68+ macrophages and decrease of pore size.

CONCLUSION

A peritoneal defect covered by IPOM prostheses leads to an increased foreign body reaction compared to intact peritoneum. Whenever feasible, a peritoneal defect should be closed accurately before placing an IPOM-mesh to avoid an excessive foreign body reaction and therefore inferior biomaterial properties of the prosthesis.

Conversion of extracellular ATP into adenosine: a master switch in renal health and disease

ATP and its ultimate degradation product adenosine are potent extracellular signalling molecules that elicit a variety of pathophysiological functions in the kidney through the activation of P2 and P1 purinergic receptors, respectively. Extracellular purines can modulate immune responses, balancing inflammatory processes and immunosuppression; indeed, alterations in extracellular nucleotide and adenosine signalling determine outcomes of inflammation and healing processes. The functional activities of ectonucleotidases such as CD39 and CD73, which hydrolyse pro-inflammatory ATP to generate immunosuppressive adenosine, are therefore pivotal in acute inflammation. Protracted inflammation may result in aberrant adenosinergic signalling, which serves to sustain inflammasome activation and worsen fibrotic reactions. Alterations in the expression of ectonucleotidases on various immune cells, such as regulatory T cells and macrophages, as well as components of the renal vasculature, control purinergic receptor-mediated effects on target tissues within the kidney. The role of CD39 as a rheostat that can have an impact on purinergic signalling in both acute and chronic inflammation is increasingly supported by the literature, as detailed in this Review. Better understanding of these purinergic processes and development of novel drugs targeting these pathways could lead to effective therapies for the management of acute and chronic kidney disease.

Improved tissue integration of a new elastic intraperitoneal stoma mesh prosthesis

Parastomal herniation is a frequent complication in colorectal surgery, occurring with a prevalence of 30-80%. The aim of the study was to create a new intraperitoneal colostoma mesh prosthesis (IPST) with enhanced elastic properties made with thermoplastic polyurethane (TPU) monofilaments. We performed open terminal sigmoid colostomies reinforced with either a 10 cm by 10 cm polyvinylidene fluoride (PVDF) or a new TPU/PVDF composite mesh in a total of 10 minipigs. Colostoma was placed paramedian in the left lower abdomen and IPST meshes were fixed intraperitoneal. After 8 weeks, the animals were euthanized after laparoscopic exploration and specimen were explanted for histological investigations. Implantation of a new IPST-mesh with enhanced elastic properties was feasible in a minipig model within an observation period of 8 weeks. Immunohistochemically, Collagen I/III ratio as a marker of tissue integration was significantly higher in TPU-group versus PVDF group (9.4 ± 0.5 vs. 8.1 ± 0.5, p = 0.002) with a significantly lower inflammatory reaction measured by a smaller inner granuloma at mesh-colon interface (17.6 ± 3.3 μm vs. 23 ± 5 μm, p < 0.001). A new TPU/PVDF composite mesh with enhanced elastic properties as IPST was created. Stoma surgery and especially the evaluation of the new stoma mesh prosthesis are feasible with reproducible results in an animal model. Tissue integration expressed by Collagen I/III ratio seems to be improved in comparison to standard-elastic PVDF-IPST meshes.

Comparison of coated meshes for intraperitoneal placement in animal studies: a systematic review and meta-analysis

PURPOSE

Laparoscopic intraperitoneal onlay mesh in hernia repair can result in adhesions leading to intestinal obstruction and fistulation. The aim of this systematic review is to compare the effects of mesh coatings reducing the tissue-to-mesh adhesion in animal studies.

METHODS

Pubmed and Embase were systematically searched. Animal experiments comparing intraperitoneally placed meshes with coatings were eligible for inclusion. Only studies with comparable follow-up, measurements, and species were included for data pooling and subsequent meta-analysis.

RESULTS

A total of 131 articles met inclusion criteria, with four studies integrated into one comparison and five studies integrated into another comparison. Compared to uncoated polypropylene (PP) mesh, PP mesh coated with hyaluronic acid/carboxymethyl cellulose (HA/CMC) showed significantly reduced adhesion formation at follow-up of 4 weeks measured with adhesion score of extent (random effects model, mean difference,-  0.96, 95% CI - 1.32 to - 0.61, P < 0.001, I² = 23%; fixed effects model, mean difference,- 0.94, 95% CI - 1.25 to - 0.63, P < 0.001, I² = 23%). Compared to PP mesh, polyester mesh coated with collagen (PC mesh) showed no significant difference at follow-up of 4 weeks regarding percentage of adhesion-area on a mesh, using random effects model (mean difference - 11.69, 95% CI - 44.14 to 20.76, P = 0.48, I² = 92%). However, this result differed using fixed effects model (mean difference - 25.55, 95% CI - 33.70 to - 7.40, P < 0.001, I² = 92%).

CONCLUSION

HA/CMC coating reduces adhesion formation to PP mesh effectively at a follow-up of 4 weeks, while the anti-adhesive properties of PC mesh are inclusive comparing all study data.

Elastic TPU Mesh as Abdominal Wall Inlay Significantly Reduces Defect Size in a Minipig Model

Background: The open abdomen with mesh implantation, followed by early reoperation with fascial closure, is a modern surgical approach in difficult clinical situations such as severe abdominal sepsis. As early fascial closure is not possible in many cases, mesh-mediated fascial traction is helpful for conditioning of a minimized ventral hernia after open abdomen. The aim of this study was to evaluate the clinical utilization of an innovative elastic thermoplastic polyurethane mesh (TPU) as an abdominal wall inlay in a minipig model. Methods: Ten minipigs were divided in two groups, either receiving an elastic TPU mesh or a nonelastic polyvinylidene fluoride (PVDF) mesh in inlay position of the abdominal wall. After 8 weeks, mesh expansion and abdominal wall defect size were measured. Finally, pigs were euthanized and abdominal walls were explanted for histological and immunohistochemical assessment. Results: Eight weeks after abdominal wall replacement, transversal diameter of the fascial defect in the TPU group was significantly smaller than in the PVDF group (4.5 cm vs. 7.4 cm; p = 0.047). Immunhistochemical analysis showed increased Ki67 positive cells (p = 0.003) and a higher number of apoptotic cells (p = 0.047) after abdominal wall replacement with a TPU mesh. Collagen type I/III ratio was increased in the PVDF group (p = 0.011). Conclusion: Implantation of an elastic TPU mesh as abdominal wall inlay is a promising approach to reduce the size of the ventral hernia after open abdomen by mesh-mediated traction. However, this effect was associated with a slightly increased foreign body reaction in comparison to the nonelastic PVDF.

AK03, a new recombinant fibrinogenase prevents abdominal adhesions in a rat model without systemic side effects

BACKGROUND

Abdominal adhesions are one of the most common complications after abdominal surgery, and fibrin is suspected to be a crucial component. The aim of the current study was an in vivo evaluation of a new recombinant fibrinogenase (AK03) in two animal models.

METHODS

Sixty-four rats were randomly divided into four groups (sodium chloride [NaCl], icodextrin, AK03 low dose, and AK03 high dose) and evaluated at two time endpoints. Adhesion model comprised both a visceral defect (terminal ileum) and parietal defect. Test (AK03) and control substances (NaCl and icodextrin) were administered intraperitoneally after setting the intraabdominal defects. A second dose was administered 24 h after surgery. Plasma fibrinogen values were taken at baseline and after 7 and 21 d, respectively. Rats were sacrificed after 7 or 21 d for macroscopic (Diamond score) and immunohistochemical investigations.

RESULTS

After 7 and 21 d, the Diamond score of postsurgical adhesions were significantly lower in both AK03-treated groups compared with NaCl control group (P = 0.02). There were no unspecific systemic side effects in both treatment groups and no decrease in plasma fibrinogen concentration. In none of the four groups was there any evidence for impaired wound repair. Microscopically in the area of the parietal defect, we saw less cluster of differentiation 3⁺ T-lymphocytes and cluster of differentiation 68⁺ macrophages in both groups receiving AK03 compared with the NaCl and icodextrin control groups.

CONCLUSIONS

The results of this study indicate that the new recombinant fibrinogenase AK03 effectively prevents peritoneal adhesions without causing side effects, notably systemic fibrinogen depletion, bleeding, or impaired wound repair. Due to these results, future clinical studies may be promising.

* The New Zealand White Rabbit as a Model for Preclinical Studies Addressing Tissue Repair at the Level of the Abdominal Wall

In this report, we review the use of the New Zealand White rabbit as the experimental animal for several models of abdominal wall repair. For the repair of an abdominal wall defect, such as a hernia in clinical practice, multiple types of prosthetic material exist. Before their marketing, each of these biomaterials needs to be tested in a preclinical setting to confirm its biocompatibility and appropriate behavior at the different tissue interfaces. For preclinical trials, we have always used the New Zealand White rabbit as the model owing to its ease of handling and suitable size. This size allows for laparoscopic studies designed to follow the behavior in real time of a biomaterial implanted at the peritoneal interface, a delicate interface that often gives rise to complications in human practice. The size of the rabbit also offers a sufficiently large number of implant samples to be harvested for a complete battery of tests at several time points postimplant. In this review, we first describe the models established and then provide the results obtained so far using these models to test the different types of biomaterial. We end our review with a discussion of the clinical implications of these results.

MRI Evaluation of an Elastic TPU Mesh under Pneumoperitoneum in IPOM Position in a Porcine Model

BACKGROUND

The frequency of laparoscopic approaches increased in hernia surgery over the past years. After mesh placement in IPOM position, the real extent of the meshes configurational changes after termination of pneumoperitoneum is still largely unknown. To prevent a later mesh folding it might be useful to place the mesh while it is kept under tension. Conventionally used meshes may lose their Effective Porosity under these conditions due to poor elastic properties. The aim of this study was to evaluate a newly developed elastic thermoplastic polyurethane (TPU) containing mesh that retains its Effective Porosity under mechanical strain in IPOM position in a porcine model. It was visualized under pneumoperitoneum using MRI in comparison to polyvinylidenefluoride (PVDF) meshes with similar structure.

METHODS

In each of ten minipigs, a mesh (TPU containing or native PVDF, 10 × 20 cm) was randomly placed in IPOM position at the center of the abdominal wall. After 8 weeks, six pigs underwent MRI evaluation with and without pneumoperitoneum to assess the visibility and elasticity of the mesh. Finally, pigs were euthanized and abdominal walls were explanted for histological and immunohistochemical assessment. The degree of adhesion formation was documented.

RESULTS

Laparoscopic implantation of elastic TPU meshes in IPOM position was feasible and safe in a minipig model. Mesh position could be precisely visualized and assessed with and without pneumoperitoneum using MRI after 8 weeks. Elastic TPU meshes showed a significantly higher surface increase under pneumoperitoneum in comparison to PVDF. Immunohistochemically, the amount of CD45-positive cells was significantly lower and the Collagen I/III ratio was significantly higher in TPU meshes after 8 weeks. There were no differences regarding adhesion formation between study groups.

CONCLUSIONS

The TPU mesh preserves its elastic properties in IPOM position in a porcine model after 8 weeks. Immunohistochemistry indicates superior biocompatibility regarding CD45-positive cells and Collagen I/III ratio in comparison to PVDF meshes with a similar structure.

A Novel Method for Evaluating Postoperative Adhesions in Rats

Purpose/Aim: Postoperative adhesions remain an undesirable and commonly symptomatic side effect of abdominopelvic surgeries. Animal models of postoperative adhesions typically yield heterogeneous adhesions throughout the abdominal cavity and are not easily quantified. Here we present a novel method of postoperative adhesion assessment and report its reliability and measurement error.

MATERIALS AND METHODS

A model of cecal abrasion with partial sidewall attachment was performed on female rats. After 1, 2, 4, or 7 days of recovery, the rats were euthanized and their abdominopelvic cavities were systematically evaluated for postoperative adhesions. The necropsy was recorded through the surgical microscope. Four raters were trained to use a ballot to capture key factors of the adhesions as they viewed the recordings. Their ratings were compared for measurement error and reliability (using Bland-Altman plots and intraclass correlation coefficients, respectively) and for the ability to discriminate differences in experimental groups. A subset of the data was analyzed to determine practical utility.

RESULTS

The rating system was shown to have low measurement error and high inter-rater reliability for all parameters measured. Applied practically, the system was able to discriminate groups in a manner that was expected.

CONCLUSIONS

We have developed and validated a rating system for postoperative adhesions and shown that it can detect group differences. This method can be used to quantify postoperative adhesions in rodent models.

Analysis of adhesion formation of a new elastic thermoplastic polyurethane (TPU) mesh in comparison to polypropylene (PP) meshes in IPOM position

BACKGROUND

Postsurgical adhesions severely affect the patients' quality of life causing various complications like bowel obstruction or chronic pain. Especially the implantation of alloplastic prostheses in IPOM position for hernia repair carries a high risk of adhesion formation due to the close contact between mesh and viscera. The extent of adhesions mainly depends on the type and textile characteristics of the implanted mesh. The aim of this study was to examine the degree of adhesion formation of a newly developed, elastic thermoplastic polyurethane (TPU) mesh in comparison to polypropylene (PP) meshes in IPOM position in a rabbit model.

METHODS

Sixteen female chinchilla rabbits were laparoscopically operated. Two different meshes were placed to the left and the right lower abdominal wall in IPOM position in each rabbit. After 7 or 21 days, midline laparotomy was performed, the degree of adhesion formation was examined by the Diamond score and mesh elongation was measured under a force of 3N. Finally, the abdominal walls were explanted for immunohistochemical and histopathological investigations.

RESULTS

TPU meshes showed significantly lower Diamond scores than PP meshes. After explantation, mesh elongation of the TPU mesh was significantly larger than expansion of PP under a force of 3N. Thus, the TPU mesh preserved its elastic properties after 7 and 21 days. The amount of CD68 positive, Ki67 positive and apoptotic cells within the granuloma around the fibers did not show significant differences between the study groups.

CONCLUSIONS

The newly developed TPU mesh seems to reduce peritoneal adhesion formation in IPOM position in a rabbit model compared to PP meshes after 7 and 21 days. Immunohistochemistry did not reveal differences in biocompatibility of the two meshes used.

Influence of 4% icodextrin solution on peritoneal tissue response and adhesion formation

BACKGROUND

Postoperative peritoneal adhesion formation following abdominal surgery remains a relevant surgical problem. The application of soluble physico-chemical barriers like 4% icodextrin is one approach to protect the peritoneal surface from getting linked to adhesive scar. The aim of this study was to investigate the influence of 4% icodextrin on peritoneal tissue response both of visceral and parietal peritoneum, adhesion formation and wound healing.

METHODS

40 rats were divided into two groups. After creation of an intraabdominal defect, either 4% icodextrin (Adept®) or sodium chloride was applied. Animals were sacrificed after 7 and 21 days. Adhesions were scored by an adhesion score. Furthermore, immunohistochemical investigations were conducted to determine the discrete influence of icodextrin on the parietal and visceral peritoneal tissue responses (CD68+ macrophages, CD3+ T-lymphocytes, vimentin for mesenchymal cells, HBME-1 for mesothelial cells, and as components of wound healing COX-2, C-myc, catenin).

RESULTS

Postoperative peritoneal adhesions were predominantly present in the sodium chloride group as compared to the icodextrin group (14/19 (74%) vs. 9/19 (47%); p = 0.048). The adhesion score however did not reveal any significant differences, (p = 0.614). Furthermore, the expression of vimentin in both the parietal and visceral peritoneum after 21 days was significantly lower in the icodextrin group than in the sodium chloride group (p = 0.038 and p = 0.028, respectively). No significant differences were observed for macrophages, lymphocytes, reperitonealisation or the expression of COX-2, C-myc or Catenin.

CONCLUSIONS

The intraperitoneal application of 4% icodextrin reduces adhesion formation in comparison to sodium chloride. 4% icodextrin solution reduces the inflammatory and mesenchymal infiltrate in the wounded area, thus improving the ratio of mesothel cells to mesenchymal infiltrate. As demonstrated, icodextrin is able to ameliorate the local tissue response. Further experimental studies would be done to elaborate the impact on the early response of the adaptive immune system, which may then trigger the subsequent wound healing and tissue repair.

Adhesion prevention in an intraperitoneal wound model: performance of two resorbable hemostats in a controlled study in rabbits

Adhesions, particularly in the abdominal and pelvic cavities, represent a significant clinical problem. Among other complications, they are considered the most common cause of intestinal obstructions in the Western world. The purpose of this study was to evaluate two commercially available hemostats for their ability to prevent adhesion formation in an abdominal wound model. The hemostats, a microfibrillar collagen-based composite and microporous polysaccharide spheres were used in a rabbit abdominal model. In the model the cecum was abraded and a peritoneal defect was created on the abdominal sidewall. The test materials were applied over the defects. Clinical and histological results were compared with control (no application of any hemostat at the defect site) on postoperative day 14. The results showed a significant reduction in the incidence, extent and severity of adhesions for both surgical hemostat materials compared with control. The microfibrillar collagen-based composite showed a total absence of adhesions and a high level of reperitonealization. This preclinical study suggests that the use of surgical hemostats may help to reduce or eliminate adhesions and may promote reperitonealization.

APPLICATIONS OF COLLAGEN IN MEDICAL DEVICES

Collagen is the most abundant natural protein found in living systems. While there is a whole family of different collagen types, each differing in sequence, the properties that make this protein so attractive as the building blocks for medical devices, are reflected largely by the unique fibrillar structure of the molecule, as well as defined functional regions that interact with the surrounding cells and other matrix components. As a commercial medical product, collagen can be part of the natural tissue used in the device, or it can be fabricated as a reconstituted product from animal or recombinant sources. Both types of uses have distinct properties that convey advantages and disadvantages to the end product. This review examines the chemistry and biology of collagen and describes some well-documented examples of collagen-based medical devices produced in one or other of these formats.

Tissue compression analysis for magnetically anchored cautery dissector during single-site laparoscopic cholecystectomy

INTRODUCTION

The purpose of this study was to evaluate the histological effects of dynamic abdominal wall compression using the magnetic anchoring and guidance system (MAGS) platform.

METHODS

Cholecystectomy was performed in two nonsurvival and two survival pigs using a single-site laparoscopic (SSL) approach. A deployable MAGS cautery dissector was used to perform the entire dissection in conjunction with a laparoscope and other instruments. The abdominal wall areas corresponding to the region occupied by the MAGS platform were examined grossly and microscopically for signs of tissue damage. Gallbladder dissection time was 36 min with no complications. Compressed abdominal wall thickness was 1.4 cm.

RESULTS

In all four animals, a very mild skin erythema was noted immediately postprocedure but was nonvisible within 20 min. Mild peritoneal blanching was noted in two animals, and one animal exhibited a 5-mm area of petechiae. Necropsy demonstrated no adhesions. Light microscopy documented no evidence of tissue injury for all specimens.

DISCUSSION

This study demonstrated that the use of the MAGS cautery dissector for a SSL cholecystectomy was advantageous in providing triangulation and did not result in any significant gross or microscopic tissue damage despite the thin abdominal wall of the porcine model.

N-butyl cyanoacrylate versus conventional suturing for fixation of meshes in an incisional hernia model

BACKGROUND

Chronic pain and related complications reported after the use of perforating fixation devices in hernia surgery have led to the use of tissue sealants. Fibrin sealant is a feasible option for mesh fixation; however data on cyanoacrylate glues are limited.

METHODS

32 Sprague-Dawley rats were divided into two groups and a 1.5 cm abdominal wall defect was created on each animal. The lesions were then repaired with 2 × 2 cm polypropylene meshes, fixed with n-butyl-cyanoacrylate in the first group and with polypropylene sutures in the second group. The rats were sacrificed on the 21st and 42nd days. The presence of infection, recurrence, and abdominal adhesions were evaluated, followed by biomechanical testing and histological examination.

RESULTS

No mesh infection or hernia recurrences were recorded. There was no statistically significant difference between neither the adhesion scores nor the mean broken pressure of the two groups. Cyanoacrylate sealing was found equivalent to suturing in terms of tissue ingrowth, fibrosis, inflammatory infiltration, abscess formation, and necrosis. Furthermore, cyanoacrylate resulted in less foreign body reaction.

CONCLUSIONS

Mesh fixation by cyanoacrylate may be considered as an alternative to suture fixation.

Tissue anti-adhesion potential of biodegradable PELA electrospun membranes

The most commonly used anti-adhesion device for separation and isolation of wounded tissues after surgery is the polymeric membrane. In this study, a new anti-adhesion membrane from polylactide-polyethylene glycol tri-block copolymer (PELA) has been synthesized. The synthesized copolymers were characterized by gel permeation chromatography and (1)H nuclear magnetic resonance spectroscopy. PELA membrane was prepared by electrospun. The prepared copolymer membranes were more flexible than the control poly-d-l-lactic acid (PDLLA) membrane, as investigated by the measurements of glass transition temperature. Its biocompatibility and anti-adhesion capabilities were also evaluated. In vitro cell adhesions on the PELA copolymer membrane and PDLLA membrane were compared by the culture of mouse fibroblasts L929 on the surfaces. For in vivo evaluation of tissue anti-adhesion potential, the PDLLA and PELA copolymer membranes were implanted between cecum and peritoneal wall defects of rats and their tissue adhesion extents were compared. It was observed that the PELA copolymer membrane was very effective in preventing cell or tissue adhesion on the membrane surface, probably owing to the effects of hydrophilic polyethylene glycol.

Use of barrier products in the prevention of adhesion formation following surgery

Postoperative adhesion formation is a significant health-care problem with no universally accepted method of prevention. Barrier methods of prevention have been extensively tested and licensed, and this article examines the evidence.

Peritoneal adhesions: facing the enemy

BACKGROUND

Postsurgical adhesions severely affect the quality of life of millions of people worldwide. Numerous attempts have been made to prevent or reduce the incidence of peritoneal adhesions, but with limited success.

DATA SOURCES

An extensive Medline search, textbooks, scientific reports and scientific journals are the data sources. We also reviewed reference lists in all articles retrieved in the search as well as those of major texts regarding postsurgical intraperitoneal adhesion formation.

CONCLUSIONS

A multifactorial approach including minimizing tissue injury, prophylactic antibiotic usage to reduce infectious morbidity, and biochemical agents with or without biomechanical barriers will reduce the amount and severity of adhesions. However, further research is needed to establish the safety, effectiveness and also the cost/benefit ratio of these substances in human subjects.

Innovative barriers for peritoneal adhesion prevention: liquid or solid? A rat uterine horn model

OBJECTIVE

To compare the effects of solid barriers (PDLA membrane and foil, Interceed), innovative barrier solutions (Adept and Hyalobarrier Gel, phospholipid emulsion), and Ringer's lactate solution in preventing postsurgical peritoneal adhesions in the rat.

DESIGN

Prospective, randomized experimental study.

SETTING

Rat model in an academic research environment.

ANIMAL(S)

Female, nonpregnant Wistar rats.

INTERVENTION(S)

Standardized surgical injuries were applied to the parietal and visceral peritoneum and the uterine horns. The barrier agents were applied and the wound was closed. A second-look laparoscopy was performed 31 days after surgery to assess adhesion formation.

MAIN OUTCOME MEASURE(S)

Severity and extent of adhesion formation assessed using a multidimensional adhesion scoring system.

RESULT(S)

Significantly fewer postsurgical adhesions were seen after treatment with Adept, Hyalobarrier Gel, Interceed, PDLA membrane, and phospholipid emulsion than after Ringer's lactate solution. Severe, clinically relevant adhesions were not observed after Hyalobarrier Gel and in only one animal after Adept.

CONCLUSION(S)

Both solid and liquid barriers can prevent adhesions. Hydroflotation formulas, such as Adept and Hyalobarrier Gel, avoid suture-induced adhesions, are easy to use, and their protective effects are evenly distributed. They are suitable for adhesion prevention after multifocal trauma in rats, and require further testing in the everyday clinical situation.

Prevention of adhesion to prosthetic mesh in incisional ventral hernias: comparison of different barriers in an experimental model

BACKGROUND

The purpose of this study was to compare the intra-abdominal adhesion formation following ventral hernia repair by using oxidized regenerated cellulose (ORC) as a barrier underneath polypropylene mesh (PPM), and sodium hyaluronate/carboxymethylcellulose (HA/CMC)-coated PPM.

METHODS

A ventral abdominal defect was created in each of 30 male rats which were divided into three groups. In group 1 (control) the defect was repaired with PPM; in group 2 ORC was laid over the viscera and the defect was repaired with PPM, and in group 3 HA/CMC-coated PPM was used for the repairing procedure. On the 28th postoperative day all the rats were sacrificed and adhesions were evaluated by laparoscopic exploration followed by histopathological examination.

RESULTS

Animals treated with ORC and PPM, and HA/CMC-coated PPM showed significantly less adhesions than the control group (p = 0.026) and the intra-abdominal adhesions of the rats in these two groups were significantly easier to release than in the control group (p = 0.001). There was no significant difference between the ORC and HA/CMC groups.

CONCLUSIONS

ORC used together with PPM is as effective as HA/CMC-coated PPM and ORC can be used as an adhesion barrier in intra-abdominal hernia repair.

Experimental study evaluating the effect of a barrier method on postoperative intraabdominal adhesions

The purpose of this animal study was to determine if tissue glue-coated collagen sponge is an effective barrier method to prevent localized adhesions in a modified rabbit sidewall model. Rabbits were divided into two groups and underwent laparotomy with subsequent creation of a cecal wound according to the rabbit sidewall model. Rabbits of group I (treatment group; n = 10) were treated with a TachoComb H patch placed on the defect, whereas group II animals (control group; n = 6) did not receive further treatment. All animals were sacrificed 2 weeks postoperatively and adhesions were evaluated using special adhesion score. A further six rabbits underwent TachoComb H application at the cecum to investigate the histological changes during a course of 12 weeks. The average adhesion scores were significantly (P < 0.05) reduced in the treatment group compared to the controls. Histologically the TachoComb H patch was surrounded by granulation tissue without signs of infection. Tissue glue-coated collagen sponge (TachoComb H) is effective to prevent localized intraabdominal adhesions in the modified rabbit sidewall model.

The whole truth: comparative analysis of diaphragmatic hernia repair using 4-ply vs 8-ply small intestinal submucosa in a growing animal model

BACKGROUND

Diaphragmatic reconstruction remains a challenging problem. There is limited information concerning the use of small intestinal submucosa (SIS) in congenital diaphragmatic hernia repair. A canine model was used to evaluate the use of a SIS patch in diaphragmatic reconstruction.

METHODS

Eleven beagle puppies (1.6-4.2 kg, 8 weeks old) underwent left subcostal laparotomy, central left hemidiaphragm excision (2 x 7 cm, 50% loss), and reconstruction with a 4-ply group I (n = 5) or 8-ply group II (n = 6) SIS patch. Chest radiographs were taken at time of operation and 3 and 6 months postoperatively. Animals were killed at 6 months. Adhesion formation (both pleural and abdominal), gross visual evaluation of the patch, and histology were compared.

RESULTS

In group I (4-ply), 1 animal died at 3 months from patch deterioration accompanied by stomach herniation that resulted in respiratory failure. In the 4 remaining animals, chest radiographs showed no evidence of herniation or eventration. On physical examination, there was no evidence of chest wall deformity. During gross surgical examination, the 4-ply patches showed thinning, multiple defects, and liver herniation in 3 animals. In 1 pup, the patch was thickened, intact, well incorporated at the repair site, and adherent to the liver and spleen. In group II (8-ply), 1 animal died of cardiopulmonary failure in the early postoperative period. In the other 5 animals, chest radiographs showed evidence of eventration in 1. On gross examination the patch adhered to the liver in all 5 surviving animals. In 4, the patches were thickened, viable, but had some shrinkage. One patch pulled away from the native diaphragm laterally; however, no visceral herniation was present. In the 1 animal with eventration, there was no evidence of a patch. Adhesion scores (AS) were graded and determined by the sum of extent (0-4), type (0-4), and tenacity (0-3). Average abdominal AS in group I was 5.6 +/- 0.8 vs 10.2 +/- 0.2 (P = .079) for group II. Average lung AS was 0.6 +/- 0.6 in group I vs 3.8 +/- 1.1 (P = .0476) for group II. Histological examination showed group II patches had greater collagen deposition with central calcification and mild inflammation within the residual graft, whereas group I patches were much thinner and were composed of granulation tissue without evidence of residual graft.

CONCLUSIONS

These data indicate that 8-ply SIS repair of diaphragmatic defects was superior (80%; 4/5 to 4-ply, 20%; 1/5, success). Organ adherence appears to be necessary for neovascularization of the SIS composite. Eight-ply grafts appear to be more durable and persist for a longer period, which may improve neovascularization. Long-term follow-up to evaluate remodeling characteristics of the patch material is required.

Comparaison des adhérences postopératoires après lymphadénectomies para-aortiques par laparotomie avec versus sans Intergel

INTRODUCTION

Advanced cancers of the cervix are treated by external radiotherapy within range limits which depend on the para-aortic ganglion metastases found during surgical staging. The presence of postoperative intraperitoneal adhesions increases the risk of postradical enteritis. The aim of this study is to investigate the efficacy of an anti-adhesive substance (Intergel) undergoing para-aortic lymphadenectomy by laparotomy.

MATERIALS AND METHODS

We conduced a prospective, randomized study on 60 pigs divided into 2 groups (with and without Intergel) undergoing para-aortic lymphadenectomy by laparotomy to compare the efficacy of an anti-adhesive substance using an adhesion scoring system based on density and surface area in question.

RESULTS

There was no difference between the 2 groups in terms of duration of surgery, number of ganglia removed, postoperative mortality and per and postoperative morbidity, especially the adhesion process.

CONCLUSION

Administration of an anti-adhesive substance such as Intergel does not reduce the adhesion process after para-aortic lymphadenectomy in animals. However, perhaps we can not interpret these results because of the too much quantity of anti-adhesive substance for the animal weight, and because of the too precocious control.

Effects of oxidized regenerated cellulose on the expression of extracellular matrix and transforming growth factor-beta1 in human peritoneal fibroblasts and mesothelial cells

OBJECTIVE

The purpose of this study was to evaluate the potential biologic effects of oxidized regenerated cellulose, which has been shown in multiple human in vivo studies to reduce postoperative adhesion development, on the messenger RNA levels of transforming growth factor-beta1, type I collagen, type III collagen, and fibronectin.

STUDY DESIGN

The oxidized regenerated cellulose was dissolved in saline solution and added to confluent, monolayer cultures of human normal fibroblasts and mesothelial cells. Control cells were maintained in media alone at the same pH. After 24 hours of treatment, total RNA was extracted from all cells. Real-time reverse transcription-polymerase chain reaction was performed to determine the relative change in messenger RNA levels of type I, type HI collagen, fibronectin, transforming growth factor-beta1, and beta-actin (housekeeping gene) in response to the oxidized regenerated cellulose treatment (n=4 cultures). Student t tests were performed for each cell type, which compared oxidized regenerated cellulose-treated cells to control cells. Calculated power for the statistically significant findings ranged from 65% to 100%.

RESULTS

Transforming growth factor-beta1 messenger RNA was elevated by the oxidized regenerated cellulose treatment in the mesothelial cells by 13% (control cells, 0.562+/-0.022; oxidized regenerated cellulose-treated cells, 0.636+/-0.014; P=.03). In normal fibroblasts, transforming growth factor-beta1 messenger RNA was slightly, but not significantly, decreased in oxidized regenerated cellulose-exposed normal fibroblasts compared with controls (control cells, 0.622+/-0.062; oxidized regenerated cellulose-treated cells, 0.609+/-0.006; P=.85). Type I collagen was found to be increased by exposure to oxidized regenerated cellulose in both mesothelial cells and normal peritoneal fibroblasts. Type I collagen was increased by 23% in mesothelial cells (control cells [0.587+/-0.018] vs oxidized regenerated cellulose-treated cells [0.722+/-0.010], P=.002), and 27% in normal fibroblasts (control cells, 0.522+/-0.018, oxidized regenerated cellulose-treated cells, 0.665+/-0.009; P=.001). However, messenger RNA levels of type III collagen and fibronectin (other representative molecules of the extracellular matrix) were not altered significantly by oxidized regenerated cellulose application in vitro.

CONCLUSION

Oxidized regenerated cellulose influences the expression of factors that are accepted commonly to be associated with adhesiogenesis. Oxidized regenerated cellulose increased the expression of transforming growth factor-beta1 in mesothelial cells and type I collagen in mesothelial cells and normal peritoneal fibroblasts. Minimization of these oxidized regenerated cellulose-induced molecular changes, if they occur in vivo, may improve the ability of oxidized regenerated cellulose to reduce postoperative adhesion development.

Modulation of the expression of tissue plasminogen activator and its inhibitor by hypoxia in human peritoneal and adhesion fibroblasts

OBJECTIVE

To determine whether normal peritoneal and adhesion fibroblasts express tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI-I) and whether their expression is regulated by oxygen.

DESIGN

Prospective experimental study.

SETTING

University medical center.

PATIENT(S)

Cultures of human fibroblasts established from peritoneal and adhesion tissues. Hypoxia treatment of the primary cultured fibroblasts.

MAIN OUTCOME MEASURE(S)

We have used the multiplex reverse transcription polymerase chain reaction (RT-PCR) technique to determine the effect of hypoxia on the expression of tPA and PAI-I in normal peritoneal (NPF) and adhesion (ADF) fibroblasts. Cultures of NPF and ADF were exposed to hypoxia (2% O(2)) for 24 hours. RNA was extracted from cells and subjected to multiplex RT-PCR to quantitate relative changes in mRNA levels of tPA and PAI-I in response to hypoxia treatment.

RESULT(S)

Basal tPA mRNA levels are present in both NPF and ADF and were 45% higher in NPF than ADF. Hypoxia decreased tPA in both NPF and ADF by 74% and 95%, respectively. Basal PAI-I mRNA levels were 64% higher in ADF than in NPF. Hypoxia increased PAI-I mRNA levels by 67% and 53% in NPF and ADF, respectively.

CONCLUSION(S)

Plasminogen activator activity (PAA) of the peritoneum does not solely reside in the mesothelial cells, as previously identified, but also exists within fibroblasts, thus providing the potential to resolve postoperative fibrinous collections even at sites at which the mesothelial cells have been injured, removed, or destroyed. Furthermore, PAA in fibroblasts is regulated by oxygen; creation of a hypoxic state markedly attenuates PAA, thereby leading to adhesion development.

Evaluation of the antiadhesion potential of UV cross-linked gelatin films in a rat abdominal model

Among five kinds of rat adhesion models tested, the following model was selected. The epigastric vein 2.5 cm from the midline of the abdomen was cut by sharp scissors, and the lateral side of the cut epigastric vein was ligated using a 3-0 silk suture. This model could be easily prepared and gave a rate of adhesion formation of 90%, which was useful for screening antiadhesive materials. For the kinetic study of tissue adhesion in this model, an injured site was covered with a non-degradable poly(vinyl alcohol) (PVA) film. The incidence rate of adhesion was 18%, when the PVA film covered the injured site for 2 days. This suggests that an antiadhesive barrier should cover the injured site for at least 2 days. The antiadhesion efficacy of cross-linked gelatin films were evaluated using this adhesion model. The UV cross-linked gelatin film which was designed to exist for 2 days but to disappear at day 3 in the rat abdominal cavity showed the highest antiadhesion efficacy.

Risk of small bowel obstruction after the ileal pouch-anal anastomosis

OBJECTIVE

To determine the incidence of small bowel obstruction (SBO), to identify risk factors for its development, and to determine the most common sites of adhesions causing SBO in patients undergoing ileal pouch-anal anastomosis (IPAA).

METHODS

All patients undergoing IPAA at Mount Sinai Hospital were included. Data were obtained from the institution's database, patient charts, and a mailed questionnaire. SBO was based on clinical, radiologic, and surgical findings. Early SBO was defined as a hospital stay greater than 10 or 14 days because of delayed bowel function, or need for reoperation or readmission for SBO within 30 days. All patients readmitted after 30 days with a discharge diagnosis of SBO were considered to have late SBO.

RESULTS

Between 1981 and 1999, 1,178 patients underwent IPAA (664 men, 514 women; mean age 40.7 years). A total of 351 episodes of SBO were documented in 272 (23%) patients during a mean follow-up of 8.7 years (mean 1.29 episodes/patient). Fifty-four patients had more than one SBO. One hundred fifty-four (44%) of the SBOs occurred in the first 30 days; 197 (56%) were late SBOs. The cumulative risk of SBO was 8.7% at 30 days, 18.1% at 1 year, 26.7% at 5 years, and 31.4% at 10 years. The need for surgery for SBO was 0.8% at 30 days, 2.7% at 1 year, 6.7% at 5 years, and 7.5% at 10 years. In patients requiring laparotomy, the obstruction was most commonly due to pelvic adhesions (32%), followed by adhesions at the ileostomy closure site (21%). A multivariate analysis showed that when only late SBOs were considered, performance of a diverting ileostomy and pouch reconstruction both led to a significantly higher risk of SBO.

CONCLUSIONS

The risk of SBO after IPAA is high, although most do not require surgical intervention. Thus, strategies that reduce the risk of adhesions are warranted in this group of patients to improve patient outcome and decrease healthcare costs.

TNP-470 inhibits intraabdominal adhesion formation

BACKGROUND/PURPOSE

Angiogenesis plays an integral role in wound healing and tissue remodeling. The authors hypothesized that inhibition of angiogenesis would reduce intraabdominal adhesion formation.

METHODS

In 98 C57BL6/J mice, a 2-cm midline laparotomy was performed and a 5 mm2 SILASTIC (Dow Corning, Midland, MI) patch fixed to the right side of the peritoneum. Mice were injected with normal saline (n = 54) or TNP-470, an inhibitor of angiogenesis (n = 44; 30 mg/kg every other day over 6 days before surgery until 10 days after surgery). Animals were killed on postoperative days 10, 15, 35, and 55. Adhesions to the SILASTIC (Dow Corning) patch were scored based on their extent, type, and tenacity. Angiogenesis was quantified digitally as the area of vascularized peritoneum over the patch.

RESULTS

At day 10, when TNP-470 was stopped, the percentage of vascularized peritoneum over the patch was less in treatment animals than in controls (P = .004). At day 35, the patch in treatment animals was completely covered by vascularized peritoneum, similar to controls. Adhesions in TNP-470 animals were reduced at day 10 compared with controls (P<.05) and remained reduced off treatment at day 55.

CONCLUSIONS

Angiogenesis appears to play an important role in the development of intraabdominal adhesions, because the extent of early neovascularization correlates with adhesion formation. Perioperative treatment with TNP-470, a potent endothelial cell inhibitor, reduced vessel ingrowth over the patch and was associated with a sustained reduction in adhesion formation.

MRI of marked dural sac compression by surgicel in the immediately postoperative period after uncomplicated lumbar laminectomy

PURPOSE

Our purpose was to determine what represents normal findings on MR examinations of the lumbar spine in the immediately postoperative period following lumbar laminectomy with retained Surgicel.

METHOD

MR examinations were performed immediately following lumbar laminectomy in 10 patients referred for symptoms of spinal stenosis. All had Surgicel retained against the dura and were doing well postoperatively without suggestion of adverse symptoms. Images were obtained within 4 days of surgery, most within 24 h.

RESULTS

In 9 of 10 patients, severe dural tube compression was present, greater than that evident on preoperative studies.

CONCLUSION

Marked spinal canal compression can be a normal finding in the immediately postlaminectomy period in patients with retained Surgicel. There is a lack of correlation between apparent mass effect on the thecal sac and adverse effect. The MR appearance in such instances is not significant in the absence of compressive clinical symptomatology.

Effect of different barriers of oxidized regenerated cellulose (ORC) on cecal and sidewall adhesions in the presence and absence of bleeding

Adhesion formation after bowel surgery is a significant problem. The objective of this study was to evaluate two adhesion barriers composed of oxidized regenerated cellulose (ORC) in a model of bowel surgery, with and without bleeding. Ceca of female New Zealand White rabbits were abraded with gauze and a 3 x 5 cm patch of peritoneum and underlying muscle was excised from the right sidewall. Animals were randomized to receive no treatment, INTERCEED Barrier (Ethicon, Inc.), or neutralized INTERCEED (nTC7). ORC fabrics were applied to the excision site. Seven days later the percentage of the site and length of cecum with adhesions were estimated. The study was replicated in the presence of blood by nicking small vessels near the site sufficient to saturate the fabrics with blood. With hemostasis, the percentage of the sidewall with adhesions was reduced (p < .01) from 63.2 +/- 14.7% in controls (n = 6) to 4 +/- 2.7% with INTERCEED Barrier (n = 6) and 3 +/- 1.2% (n = 5) with nTC7. With bleeding, however, control (n = 5) levels of adhesions (67 +/- 17.5%) were reduced significantly with nTC7 (5.5 +/- 4%, n = 4; p < .01), but not INTERCEED Barrier (34.2 +/- 18.4%, n = 4). Similar trends were observed when the extent of adherent cecum was examined, since the cecum was the main site of adherence to the sidewall. However in the presence of blood, there was no effect of INTERCEED Barrier on cecal adhesions. We conclude that with hemostasis, both absorbable fabrics of ORC reduced adhesion formation between the injured cecum and abdominal sidewall. The effectiveness of INTERCEED Barrier, but not nTC7, was reduced but not eliminated in the presence of bleeding. This confirms similar observations in models of gynecologic surgery.

The comparison of gonadotropin-releasing hormone agonist therapy and intraperitoneal Ringer's lactate solution in prevention of postoperative adhesion formation in rat models

OBJECTIVE

To evaluate gonadotropin-releasing hormone agonists (GnRH-a) therapy and intraperitoneal Ringer's lactate solution (RL) for the prevention of postsurgical adhesion formation in rat models.

STUDY DESIGN

Forty rats were randomized into four groups: Group I was the control; in group II, RL was applied at the surgery; group III and IV received preoperative subcutaneous injections of the GNRH-a leuprolide acetate and only the diluent of the GNRH-a respectively. A standard lesion was created over the uterus of each rat. Adhesions were scored at relaparotomy 3 weeks later. Analysis of variance (Kruskal-Wallis) and Mann-Whitney U-tests were used for the statistical evaluation.

RESULTS

The average adhesion scores were 2.7+/-0.26, 1.4+/-0.27, 0.9+/-0.18, and 2.5+/-0.34 in groups I, II, III, and IV respectively. There were significant differences between the scores of groups I and II (P<0.01), groups I and III (P<0.001), groups II and IV (P<0.05), and groups III and IV (P<0.01); but not between the scores of groups II and III, and groups I and IV (P>0.05).

CONCLUSION

GNRH-a was successful in reducing postoperative adhesion formation but was not superior to intraperitoneal RL.

Adhesion formation of the parietal and visceral peritoneum: an explanation for the controversy on the use of autologous and alloplastic barriers?

OBJECTIVE

To compare formation of adhesions after injury to both parietal and visceral peritoneum and to determine the benefit of autologous transplants and alloplastic barriers in adhesion prevention.

DESIGN

Experimental prospective animal study and prospective randomized clinical study.

SETTING

An academic research environment.

PATIENT(S)

Forty women undergoing laparoscopy for endometriosis treatment.

INTERVENTION(S)

In 60 rats, either the visceral or parietal peritoneum was injured and covered with autologous peritoneal transplants in half of the animals. The formation of adhesions was assessed 21 days postoperatively. In women, adhesions were evaluated 3 months after surgery with or without placement of alloplastic barriers on visceral lesions.

MAIN OUTCOME MEASURE(S)

Adhesions evaluated according to a scoring system.

RESULT(S)

Adhesions after injury of the visceral peritoneum in rats were significantly more severe than those from the parietal peritoneum. Autologous peritoneal transplants led to fewer adhesions especially after serosal injuries. Female volunteers treated with alloplastic barrier material showed less severe adhesions than the control group.

CONCLUSION(S)

The present data indicate that the potential to form adhesions is significantly higher in visceral than in parietal peritoneal lesions. The development of adhesions after injury to the visceral peritoneum could be reduced by a synthetic barrier material.

In vivo evaluation of a collagenous membrane as an absorbable adhesion barrier

An absorbable membrane made from purified, pepsin-soluble collagen was compared to Interceed, an absorbable cellulose-based product, and to a control group for effectiveness in inhibiting the formation of adhesions between peritoneal surface injuries in adult rats. An adhesion scoring system was used to evaluate and compare the performance of the test materials with the control group in regard to the extent, tenacity, and type of any adhesions evident at 28 days following surgery. The collagen group performed significantly better (p < 0.05) than either the Interceed or control groups, showing fewer, less extensive adhesions. The collagen membranes resulted in either no or weak adhesions between the body wall and caecum. Adhesions in the Interceed group were quite variable and characterized by a marked peritoneal reaction in the caecal and body walls adjacent to adhesions. Control samples were characterized by close, dense fibrotic adhesions between the caecum and body wall. Both of the test materials showed some deficiencies in respect to their physical and handling properties that could be further improved for this indication.

Effects of physical barriers in prevention of adhesions: an incisional hernia model in rats

BACKGROUND

Adhesion formation between viscera and mesh is almost inevitable following incisional hernia repair with prosthetic mesh. Such adhesions may lead to intestinal obstruction and enterocutaneous fistulae formation and make further laparotomies extremely difficult. Sodium carboxymethylcellulose (SCMC) and Interceed TC7 (oxidized regenerated cellulose) as physical barriers have been shown to be effective in reducing postoperative adhesions.

MATERIALS AND METHODS

To evaluate the effects of SCMC and Interceed TC7, we used an incisional hernia model in rats. A ventral abdominal defect (15 x 25 mm) was created in each of 36 male rats which were then divided into three equal groups. In Group I (control) the defect was repaired with polypropylene mesh (PPM) only; in Group II the defect was repaired after a layer of Interceed TC7 was laid over the viscera with Interceed TC7-covered PPM; in Group III the defect was repaired after a layer of SCMC was laid over the viscera with SCMC-coated PPM. Six of the animals from each group were sacrificed at Postoperative Day 7 and the adhesions were scored. The remaining 6 were sacrificed at Day 30 and histological evaluation was made in addition to the adhesion score.

RESULTS

Animals in the SCMC-treated group developed significantly less adhesions (P = 0.0002) compared with control and Interceed TC7-treated groups. However, histological analysis revealed poor fibroblast proliferation with impaired wound healing in the SCMC group.

CONCLUSION

SCMC prevented adhesion formation but seriously impaired wound healing, and Interceed TC7 was ineffective in preventing adhesion in this model.

Comparison of covalently and physically cross-linked polyethylene glycol-based hydrogels for the prevention of postoperative adhesions in a rat model

A covalently and a physicochemically cross-linked hydrogel, both based primarily on polyethylene glycol and both formed in situ, were compared side by side in a rat uterine horn devascularization and serosal injury model for efficacy in adhesion prevention. The primary difference between the two materials was the nature of their cross-linking. The covalently cross-linked hydrogel was a photopolymerized polyethylene glycol-co-lactic acid diacrylate, and the physically cross-linked hydrogel was a polyethylene glycol-co-polypropylene glycol, Poloxamer 407. In the surgical model employed, application of the covalently cross-linked hydrogel reduced the extent of adhesion formation from 75 +/- 10% in the control group to 16 +/- 6% (mean +/- s.d., P < 0.001). Application of the physically cross-linked hydrogel reduced adhesion formation to 38 +/- 19% (P < 0.01). Retention of the two hydrogels upon the site of application was also evaluated. The covalently cross-linked hydrogel formed a continuous barrier upon the uterine horns for more than 4 d, while the physicochemically cross-linked hydrogel was present upon the uterine horns for less than 2 d. This difference in retention was probably the cause of the difference in efficacy and may be attributed to the nature of the cross-linking.