Prevention of adhesions to polypropylene mesh in a traumatized bowel model

BACKGROUND: Polypropylene mesh (PPM) is an effective material for the repair of abdominal wall defects, but has a tendency to induce dense adhesions when in contact with viscera. Seprafilm (Genzyme Corp, Cambridge, MA), a bioresorbable membrane, has been shown to reduce adhesion formation after midline closures in humans and to PPM in animals. Given the increased inflammatory response expected with surgical trauma, its efficacy under surgical conditions has been questioned. STUDY DESIGN: A prospective, randomized, blinded study was conducted using a rabbit model. Standardized abdominal wall defects were created in three groups of New Zealand white rabbits. The cecum was deserosalized to simulate the effects of trauma. The abdominal defect was then repaired with PPM. In the control group, no Seprafilm was used. In the first experimental group Seprafilm was placed between the mesh and the abdominal viscera. In the second experimental group Seprafilm was placed over the deserosalized area and between the mesh and abdominal viscera. Animals were sacrificed at 30 days and adhesions were categorized and quantified using digital image analysis of inked specimens. The strength of incorporation was also determined. RESULTS: The formation of adhesions between the viscera and mesh repair was dramatically reduced in both experimental groups compared with the control group. The incidence of visceral adhesions was reduced by 80% in the single film group (p = 0.0004) and 90% in the double film group (p = 0.00008). The reduction in surface area of adhesions was 96.4% in the single film group (p = 0.000019) and 99.4% in the double film group (p = 0.00002). Omental adhesions were reduced by 30% but this did not achieve statistical significance. Strength of incorporation was not adversely affected in either group. CONCLUSIONS: Seprafilm is highly effective in preventing adhesions to PPM. This effect was not diminished by the presence of visceral trauma and its resultant inflammatory response. The use of Seprafilm does not adversely affect tissue incorporation. Clinical trials are warranted to determine if the protective effects of Seprafilm demonstrated in this study are applicable in the clinical setting.     

Prevention of adhesions to polypropylene mesh in a rabbit model

The purpose of this study was to develop a quantitative model for evaluating adhesion formation and to determine whether Seprafilm (HAL-F) bioresorbable membrane (Genzyme Corp., Cambridge, MA) is effective in preventing adhesions to polypropylene mesh (PPM). PPM has been shown to be an effective material for the repair of abdominal wall defects. One disadvantage of PPM is its tendency to form dense adhesions when in contact with abdominal viscera. HAL-F, a sodium hyaluronate/carboxymethylcellulose absorbable membrane, has been shown to prevent adhesion formation after midline closures. Its efficacy in preventing adhesions to PPM has not been examined previously. A 5 x 7-cm anterior abdominal wall defect was created in 24 New Zealand White rabbits. This defect was then repaired with PPM. In the experimental group, a 5 x 7-cm piece of HAL-F was placed between the mesh and the abdominal viscera. At 30 days, the animals were killed and adhesions were categorized and quantified using digital image analysis of inked specimens. The strength of mesh incorporation into surrounding tissues was also examined using an Instron tensiometer. The formation of adhesions between the viscera and mesh repair was significantly reduced by the use of HAL-F. The surface area involved for bowel adhesions was reduced 94 per cent (P = 0.00132). The strength of incorporation was not adversely affected. HAL-F is highly effective in preventing adhesions to PPM, without adversely effecting the strength of mesh incorporation.     

Seprafilm reduces adhesions to polypropylene mesh

BACKGROUND: Adhesions to polypropylene mesh used for abdominal wall hernia repair may eventuate in intestinal obstruction or enterocutaneous fistula. A Seprafilm Bioresorbable Membrane translucent adhesion barrier has been shown to inhibit adhesions. This investigation was designed to determine if Seprafilm alters abdominal visceral adhesions to polypropylene mesh. METHODS: A 2.5-cm square abdominal muscle peritoneal defect was created and corrected with polypropylene mesh. Mesh alone was used in 17 rats. In another 17, the Seprafilm membrane was applied between the viscera and the mesh. Five animals had the bioresorbable membrane placed in the subcutaneous space and between the mesh and the viscera. Laparoscopy was performed 7, 14, and 28 days later to evaluate adhesions as a percentage of mesh surface involved. RESULTS: Polypropylene mesh alone was associated with adhesions in every rat. The average area involved was 90%, the minimum was 75%. Adhesions were present within 24 hours and progressed up to 7 days with no change thereafter. When the Seprafilm barrier was used, the mean area involved was 50%. In 16 such rats, the area involved was smaller than any control animal. No adhesions formed in 5 animals. Scanning electron microscopy demonstrated a mesothelial cell layer covering the mesh after 4 weeks. CONCLUSIONS: The use of the Seprafilm adhesion barrier resulted in a significant reduction of adhesion formation to polypropylene mesh (P <.001).     

Prevention of adhesion to prosthetic mesh: comparison of different barriers using an incisional hernia model

OBJECTIVE: To assess whether use of antiadhesive liquids or coatings could prevent adhesion formation to prosthetic mesh. SUMMARY BACKGROUND DATA: Incisional hernia repair frequently involves the use of prosthetic mesh. However, concern exists about development of adhesions between viscera and the mesh, predisposing to intestinal obstruction or enterocutaneous fistulas. METHODS: In 91 rats, a defect in the muscular abdominal wall was created, and mesh was fixed intraperitoneally to cover the defect. Rats were divided in five groups: polypropylene mesh only (control group), addition of Sepracoat or Icodextrin solution to polypropylene mesh, Sepramesh (polypropylene mesh with Seprafilm coating), and Parietex composite mesh (polyester mesh with collagen coating). Seven and 30 days postoperatively, adhesions were assessed and wound healing was studied by microscopy. RESULTS: Intraperitoneal placement of polypropylene mesh was followed by bowel adhesions to the mesh in 50% of the cases. A mean of 74% of the mesh surface was covered by adhesions after 7 days, and 48% after 30 days. Administration of Sepracoat or Icodextrin solution had no influence on adhesion formation. Coated meshes (Sepramesh and Parietex composite mesh) had no bowel adhesions. Sepramesh was associated with a significant reduction of the mesh surface covered by adhesions after 7 and 30 days. Infection was more prevalent with Parietex composite mesh, with concurrent increased mesh surface covered by adhesions after 30 days (78%). CONCLUSIONS: Sepramesh significantly reduced mesh surface covered by adhesions and prevented bowel adhesion to the mesh. Parietex composite mesh prevented bowel adhesions as well but increased infection rates in the current model.     

Evaluation of sepramesh biosurgical composite in a rabbit hernia repair model

BACKGROUND: In cases such as incisional hernia repair, polypropylene mesh (PPM) can be exposed to the underlying viscera and cause adhesions to the mesh. In this study, a composite prosthesis that was designed to be less susceptible to adhesion formation than PPM was evaluated in a rabbit incisional hernia repair model. MATERIALS AND METHODS: A 5 x 7-cm full-thickness defect was created in the abdominal wall of 30 female New Zealand White rabbits. Ten animals each were repaired with PPM, Bard Composix (PP/ePTFE), or Sepramesh biosurgical composite-a polypropylene mesh coated on one side with chemically modified sodium hyaluronate and carboxymethylcellulose (HA/CMC). The animals were sacrificed after 28 days and the overall performance, including adhesion formation and tissue integration by histology and mechanical testing, was evaluated. RESULTS: In the Sepramesh group, there was a significant reduction in the percentage of surface area covered by adhesions and a significant increase in the percentage of animals with no adhesions compared to standard materials. The tissue integration strength and overall cellular response were similar in all groups. A partially remesothelialized peritoneal surface was often apparent overlying the Sepramesh implant. CONCLUSIONS: Sepramesh biosurgical composite effectively repaired abdominal wall defects in rabbits and reduced adhesion development to the mesh compared to the use of a PPM and a PP/ePTFE composite.     

Prevention of intraabdominal adhesions produced by polypropylene mesh

Polypropylene mesh (PPM) is widely used in ventral hernia repair, however is also associated with visceral adhesions when the mesh is exposed to intraabdominal organs. In this study, a composite mesh [ePTFE (expanded polytetrafluoroehylene) + PPM] and sodium hyaluronate/carboxymethyl cellulose (NaHA/CMC) membrane laid under PPM are evaluated in terms of adhesion formation in a rat model of ventral hernia repair. In this experimental study, a 2 x 1 cm of peritoneum and underlying muscle defect was created at the right side of the anterior abdominal wall of 37 male Wistar albino rats. These defects were repaired with 2.5 x 2 cm PPM in group 1 (n = 13), with composite mesh in group 2 (n = 12) and with PPM+NaHA/CMC in group 3 (n = 12). Rats were sacrificed after 14 days and the prosthetic materials were examined for the calculation of surface area percentage covered by adhesions, for organ involvement in the adhesions and for histological evaluation. There was a reduction in the adhesion-covered area in group 2 and group 3. Organ involvement was predominantly seen in group 1. Neoperitoneum was perfect in group 2. Fibrosis and inflammation were higher in group 1. All groups showed adhesiogenic potential to some extent. This potential was maximum with PPM. Both ePTFE and NaHA/CMC displayed similar effects in preventing adhesion formation.     

Effects of seprafilm on peritoneal fibrinolytic system

BACKGROUND: There is a high incidence of adhesions after ventral hernia repair with polypropylene mesh. The purpose of the present study was to evaluate the efficacy of Seprafilm in the prevention of adhesion formation and effect on peritoneal fibrinolytic activity. METHODS: An incisional hernia model was created in rats. In the experimental group Seprafilm was placed between polypropylene mesh and abdominal organs. On the 14th day adhesions were evaluated and tissue plasminogen activator (tPA), urokinase plasminogen activator (uPA), plasminogen activator inhibitor (PAI) type 1 and 2 were measured in peritoneal biopsy specimens. Results: Adhesions were significantly reduced in the Seprafilm group (P = 0.002). Nevertheless, there were no difference between the two groups in levels of tPA, PAI-1 and PAI-2. However, the levels of uPA were significantly decreased in the Seprafilm group. CONCLUSIONS: The adhesion preventive effect of Seprafilm is not directly related in peritoneal fibrinolytic activity. Instead, the physical properties (barrier, hydroflotation and sliconizing effect) of the membrane are primarily responsible for adhesion prevention.     

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.     

Prevention of adhesions to polypropylene mesh

BACKGROUND: Polypropylene mesh used to repair abdominal wall hernias routinely induces dense adhesions if there is direct contact between the mesh and the viscera. Adhesions may lead later to difficult reoperation, intestinal obstruction, or enteric fistula. STUDY DESIGN: A 2.5-cm square defect was surgically created in the rat abdominal wall and replaced with: 1) polypropylene mesh, 2) Sepramesh (SM), or 3) SM plus Seprafilm. Each group included 20 animals. Adhesion area as a percent of the mesh surface was subjectively quantitated by means of laparoscopy and at sacrifice. Evaluations varied from 7 to 28 days after mesh placement. Tissues were harvested at intervals for scanning electron microscopy. RESULTS: Adhesions were complete by day 7, with no change in area thereafter. Adhesion-free mesh surfaces were found on scanning electron microscopy to be carpeted with mesothelial cells from day 5 on. Polypropylene mesh alone induced adhesions in all rats (20/20). The mean area involved was 92%. With SM, 9 of 20 were adhesion-free. The mean area was 15%. When Seprafilm was added to SM, minimal adhesions developed in 5 of 20 rats, the mean area being 2%. Four of the five were single point omental attachments. CONCLUSIONS: 1) Sepramesh alone reduces polypropylene mesh adhesions by roughly three-quarters. 2) Sepramesh plus Seprafilm nearly eliminates such visceral adhesions. 3) Mesothelial cell coverage of polypropylene mesh confers adhesion resistance.     

Seprafilm reduces adhesions to polypropylene mesh and increases peritoneal hydroxyproline

Polypropylene mesh is an effective and widely used material in repairing abdominal wall defects, but it causes dense adhesions when in contact with abdominal viscera directly. As a consequence of this process intestinal obstruction and enterocutaneous fistula may develop. The purpose of the present study was to determine whether Seprafilm, a bioresorbable translucent membrane, reduces abdominal visceral adhesions to polypropylene mesh and whether Seprafilm has any effects on peritoneal tissue hydroxyproline levels. Twenty-six adult Wistar rats were used. A full-thickness abdominal wall defect was created and cecal abrasions were created to induce adhesion formation in each animal. All of the abdominal defects were repaired with polypropylene mesh. In addition a Seprafilm membrane was laid over the abdominal viscera in the Seprafilm group (n = 13). The abdominal cavity was evaluated for adhesion formation, and peritoneal biopsies were taken for the measurement of tissue hydroxyproline levels at the 14th day. The use of Seprafilm resulted in significant reduction in the adhesion formation (P = 0.002) and a significant increase in peritoneal hydroxyproline level (P < 0.0001). These findings demonstrate that the increase of peritoneal hydroxyproline levels caused by Seprafilm might play a role on the antiadhesive effects of Seprafilm.     

Adhesion formation and reherniation differ between meshes used for abdominal wall reconstruction

Incisional hernia is a common surgical problem, frequently requiring prosthetic mesh repair. The demands of the ideal mesh seem conflicting; ingrowth at the mesh–fascia interface, without development of adhesions at the visceral mesh surface. Various antiadhesives combined with macroporous mesh and composite meshes were studied for prevention of adhesions to mesh and ingrowth into the fascia. In 60 rats an abdominal wall defect was created and repaired with underlay mesh. Rats were divided into six groups and treated with polypropylene mesh (PPM, control), PPM with auto-cross-linked polymers (ACP) gel, PPM with fibrinogen glue (FG), polypropylene/expanded polytetrafluoroethylene (ePTFE) mesh, polypropylene/sodium hyaluronate/carboxymethylcellulose (HA/CMC) mesh, and polypropylene-collagen/polyethylene-glycol/glycerol (CPGG) mesh. Mesh infection was assessed in the postoperative period, adhesions and reherniations were scored at sacrifice 2 months after operation, and tensile strength of the mesh–tissue interface was measured. Six rats developed mesh infection, half of them were treated with PPM/ePTFE. The PPM/HA/CMC group showed a significant reduction in the amount and severity of adhesions. In animals treated with PPM/ACP and PPM/FG, severity of adhesions was reduced as well. Reherniation rate in the PPM/ACP group was 50% and significantly higher than that in other groups. Rats in the PPM/HA/CMC had the highest tensile strength. PPM/HA/CMC approaches the demands of the ideal mesh best, having superior antiadhesive properties, no reherniation and no infection in this rat model of incisional hernia.     

Application of Adcon-P or Seprafilm in consecutive laparotomies using a murine model

BACKGROUND: Intraabdominal administration of antiadhesive products may reduce postoperative adhesions. We compared two barriers, Adcon-P (Gliatech, Cleveland, Ohio) and Seprafilm (Genzyme, Cambridge, Massachusetts), in a relaparotomy murine model to evaluate whether using them during the first and second laparotomy reduces adhesion formation better than using them only during the relaparotomy. METHODS: One-hundred and fifty mice underwent cecal abrasion, followed by complete adhesiolysis and cecal abrasion 21 days later. All were sacrified 21 days after the second operation. The mice (30 to a group) received Adcon-P in both surgeries (AA), Seprafilm in both surgeries (SS), Adcon-P in the second surgery (CA), Seprafilm in the second surgery (CS), or neither barrier (CC). Difficulty of adhesiolysis was blindly assessed with a 6-point scoring system and sites of adhesions were determined with a yes/no questionnaire. RESULTS: The AA group had lower adhesiolysis score than SS, CS, and CC groups, and had fewer adhesions over cecum and between cecum and intra-peritoneal fat than all other groups. The numbers of the animals had adhesions between the cecum and abdominal wall were similar between the treatment groups. No difference was observed between SS and CS groups in any analysis. CONCLUSIONS: Using Adcon-P starting with the first laparotomy more effectively reduce adhesion formation and difficulty of adhesiolysis. Using Seprafilm only in the relaparotomy is as effective as using it in both laparotomies. Adcon-P is more effective in preventing adhesions to different sites than Seprafilm except to the abdominal wall under the midline incision.     

Prevention of adhesion formation to polypropylene mesh by collagen coating: A randomized controlled study in a rat model of ventral hernia repair

Introduction In laparoscopic incisional hernia repair with intraperitoneal mesh, concern exists about the development of adhesions between bowel and mesh, predisposing to intestinal obstruction and enterocutaneous fistulas. The aim of this study was to assess whether the addition of a collagen coating on the visceral side of a polypropylene mesh can prevent adhesion formation to the mesh.Method In 58 rats, a defect in the muscular abdominal wall was created, and a mesh was fixed intraperitoneally to cover the defect. Rats were divided in two groups; polypropylene mesh (control group) and polypropylene mesh with collagen coating (Parieten mesh). Seven and 30 days postoperatively, adhesions and amount and strength of mesh incorporation were assessed. Wound healing was studied by microscopy.Results With Parieten mesh, the mesh surface covered by adhesions was reduced after 30 days (42% vs 69%, p = 0.01), but infection rate was increased after both 7 (p = 0.001) and 30 days (p = 0.03), compared to the polypropylene group with no mesh infections. If animals with mesh infection were excluded in the analysis, the mesh surface covered by adhesions was reduced after 7 days (21% vs 76%, p = 0.02), as well as after 30 days (21 vs 69%, p < 0.001). Percentage of mesh incorporation was comparable in both groups. Mean tensile strength of mesh incorporation after 30 days was higher with Parieten mesh.Conclusion Although the coated Parieten mesh was more susceptible to mesh infection in the current model, a significant reduction of adhesion formation was still seen with the Parieten mesh after 30 days, with comparable mesh incorporation in the abdominal wall.     

Effective prevention of adhesions with hyaluronate

HYPOTHESIS: Hyaluronate sodium in the form of a bioresorbant membrane reduces the development of intra-abdominal adhesions frequently found after implantation of synthetic mesh in the context of surgical hernia repair. DESIGN: The effect of hyaluronate on the formation of adhesions was evaluated when applied laparoscopically as a bioresorbant membrane to protect the peritoneal surface of a synthetic mesh. SETTING: Experimental animal model. INTERVENTIONS: A peritoneal defect 5 cm in diameter was bilaterally created in the abdominal wall of each of 9 pigs by laparoscopy. A polypropylene mesh was fixed with clips onto these defects on both sides. In each of the animals, only on one side, the synthetic mesh was also covered by a hyaluronate membrane. MAIN OUTCOME MEASURES: The incidence and severity of adhesions (grade 0-4, where 0 indicates no adhesion; 1, filmy avascular adhesions; 2, vascular adhesions; 3, cordlike fibrous adhesions; and 4, plain fibrous adhesions) were determined after 45 days, comparing treated and untreated sides by autopsy results and histological features. RESULTS: Adhesions, mainly grades 3 and 4, occurred in 7 of the 9 animals in those meshes not covered by hyaluronate; 2 untreated animals did not develop adhesions. On the other hand, only 1 of the 9 animals developed adhesions (grade 2) at the mesh concealed by the hyaluronate membrane. CONCLUSIONS: The bioresorbant hyaluronate membrane significantly reduced the formation of peritoneal adhesions (1-sided sign test, P<.05) induced by the insertion of a polypropylene mesh, when compared with the contralateral implants not protected by hyaluronate. Thus, hyaluronate membranes are efficient for reducing the incidence of peritoneal adhesions.     

Fewer Intraperitoneal Adhesions With Use of Hyaluronic Acid–Carboxymethylcellulose Membrane: A Randomized Clinical Trial

OBJECTIVE: To assess the effectiveness of bioresorbable Seprafilm membrane in preventing abdominal adhesions in a prospective clinical randomized multicenter trial. SUMMARY BACKGROUND DATA: Adhesions occur frequently after abdominal operations and are a common cause of bowel obstruction, chronic abdominal pain, and infertility. To reduce the formation of adhesions, a mechanical barrier composed of hyaluronic acid and carboxymethylcellulose was developed, preventing adherence of tissues after abdominal surgery. METHODS: Between April 1996 and September 1998, all patients requiring a Hartmann procedure for sigmoid diverticulitis or obstructed rectosigmoid were randomized to either intraperitoneal placement of the antiadhesions membrane under the midline during laparotomy and in the pelvis, or as a control. Direct visual evaluation of the incidence and severity of adhesions was performed laparoscopically at second-stage surgery for restoration of the continuity of the colon. RESULTS: A total of 71 patients were randomized; of these, 42 could be evaluated. The incidence of adhesions did not differ significantly between the two groups, but the severity of adhesions was significantly reduced in the Seprafilm group both for the midline incision and for the pelvic area. Complications occurred in similar numbers in both groups. CONCLUSIONS: Seprafilm antiadhesions membrane appears effective in reducing the severity of postoperative adhesions after major abdominal surgery, although the incidence of adhesions was not diminished. The authors recommend using Seprafilm when relaparotomy or second-look intervention is planned. Long-term studies are needed to assess the cost-effectiveness and value of Seprafilm in preventing bowel obstruction, chronic abdominal pain, and infertility.     

Dried human amniotic membrane as an antiadherent layer for intraperitoneal placing of polypropylene mesh in rats

Background

Intraabdominal peritoneal onlay polypropylene (PP) mesh repair of incisional hernia has the potential risk of adhesions, bowel obstructions, and intestinal fistulae. Fresh or cryopreserved human amniotic membrane (HAM) has been tested as an antiadherent layer in animals, with excellent outcomes. However, it has disadvantages: it is difficult to handle, and it is expensive to store. Another processing method is available: drying in a laminar flow hood and gamma irradiation. Because this method impairs the membrane’s cell viability, it may affect its antiadherent properties. However, such properties may also result from the collagen matrix and its basement membrane, which remain after drying. The aim of the present study was to asses dried irradiated HAM in adhesion prophylaxis in rats.

Methods

Twenty-four female rats were randomized into two groups. In the first group (control group), PP meshes were placed in the intraabdominal space, and in the second group (treatment group), PP meshes coated with HAM were used. Animals were killed on day 30 after surgery. Adhesions and parietal prosthetic incorporation were assessed macroscopically and expressed as the average percentage of the covered area. The portion of the abdominal wall was then resected for histological testing.

Results

The treatment group had a significantly higher percentage of adhesions and parietal incorporation compared with the control group (p = 0.003). Histological testing showed a higher inflammatory response in the treatment group, with an intense foreign body reaction.

Conclusions

Dried irradiated HAM does not prevent adhesion formation in intraabdominal peritoneal onlay PP mesh repair in rats. Any use of this biomaterial in adhesion prophylaxis must be undertaken respecting graft cell viability as much as possible.     

Comparison of Prosthetic Materials in Incisional Hernia Repair

Purpose Incisional hernias are not uncommon after abdominal surgery, but their repair is associated with a high risk of complications, including adhesions and recurrence. Many different types of meshes and adhesion barriers have been developed in an attempt to overcome these problems, some of which we have assessed in a rat model.Methods We made a full-thickness 1.5 × 2.5-cm abdominal wall defect in 30 Sprague-Dawley rats, which were divided into three groups according to the materials used for repair: 2 × 3-cm polypropylene mesh (group 1); expanded polytetrafluoroethylene (PTFE) with double-layer polypropylene mesh (group 2); or polypropylene mesh with oxidized cellulose adhesion barriers (group 3). We assessed adhesion formation, tensile strength, and histopathologic findings.Results The mean adhesion scores were 3.3, 1.3, and 0.7, in groups 1, 2, and 3, respectively (P < 0.001). The area involved by adhesions was significantly greater in group 1 than in groups 2 or 3 (P < 0.01, P < 0.05), but there was no significant difference between groups 2 and 3 (P < 0.05). The tensile strength in group 2 was less than that in groups 1 or 3 (P < 0.01, P < 0.05), but there was no significant difference between groups 1 and 3 (P > 0.05).Conclusion Although there was less adhesion formation with PTFE and oxidized cellulose, PTFE not only impaired the tensile strength, but also induced fibrosis and inflammation. An oxidized cellulose adhesion barrier can be safely used in incisional hernia repair to prevent intra-abdominal adhesions.     

Bioabsorbable membrane prevents adhesions to polypropylene mesh in rats

Summary Most of mesh materials used in the repair of ventral hernias lead to considerable adhesion formation. In this study we evaluated the effects of a bioabsorbable membrane composed of carboxymethylcellulose and hyaluronic acid (HA membrane) on adhesion formation in the presence of a polypropylene mesh used to repair an incisional hernia model in rats. We repaired the defects either primarily or by polypropylene mesh. The abdominal surface of the repairs were then covered by a piece of HA membrane in randomly selected groups. The presence and grade of adhesions to the repair or mesh were recorded on the 8th day. Tissue specimens were analyzed for the extent of mesothelial and collagenous tissue growth and the degree of inflammation. Dense adhesions developed on all of the defects repaired by polypropylene mesh alone. The HA membrane decreased adhesions significantly when used as a supplement over the mesh (p < 0.01). Histopathologically, the HA membrane further retarded mesothelial growth over the mesh, and decreased vascular proliferation, inflammatory cell infiltration (p < 0.01) and collagen content of the wound (p < 0.05). In our rat model, the HA membrane prevented most of the adhesions that would be expected to occur on the mesh. It decreased the local infiltration of white cells and neovascularization. The HA membrane seemed to be a suitable physical barrier in rats against adhesion formation without compromising the wound healing. However, these findings need to be confirmed in humans.     

Modified technique for parastomal hernia repair in patients with intractable stoma-care problems

OBJECTIVE: Although stoma relocation is generally the first choice of treatment for parastomal hernia, a repair using polypropylene prosthetic mesh is sometimes employed in cases of parastomal hernia recurrence. Use of this mesh, however, has been associated with a high risk of bowel erosion, adhesions formation, and fistulization. We therefore began to use expanded polytetrafluoroethylene (ePTFE) mesh to perform an onlay parastomal hernia repair. Our initial clinical experience with this procedure is described. PATIENTS AND METHODS: Sixteen patients aged 39-70 years with intractable stoma problems underwent a modified intra-abdominal onlay technique with implantation of a large (26 x 36 cm) sheet of ePTFE mesh. RESULTS: During a median follow-up of 29 months (range, 5-52 months), no mesh-related bowel erosion, fistulization, or adhesion formation were observed. Two patients had a recurrence of the hernia due to technical failure. Re-operation in one of these resulted in wound dehiscence and removal of the contaminated mesh. Another patient developed intestinal obstruction postoperatively. The mesh was removed, and a gastrointestinal stromal tumour was found. Finally, a nonmesh related small bowel erosion required removal of the mesh in one patient. All other patients had full relief of symptoms. CONCLUSION: The modified onlay technique using a large sheet of ePTFE prosthetic mesh is a feasible option for treatment of parastomal hernia recurrence. Possible advantages of the procedure include stoma preservation, strengthening of the abdominal wall, and a reduced risk of recurrence, contamination, fistulization, and bowel adhesions and erosion.     

Interposition of polyglactin mesh does not prevent adhesion formation between viscera and polypropylene mesh

BACKGROUND: The use of intra-peritoneal polypropylene mesh (PPM) to repair incisional hernia carries the risk of adhesions and damage to the intra-abdominal viscera. Polyglactin 910 mesh (PGM) is advocated to avoid contact between PPM and the intra-abdominal viscera. An experimental study in rats was performed to determine if interposition of a resorbable prosthesis between the PPM and viscera alters biocompatibility, adhesion formation, and herniation. MATERIALS AND METHODS: A 2- x 3-cm abdominal wall defect was created in 80 rats. Rats were randomly assigned for repair with 2.5- x 3.5-cm PPM (n = 40) or 2.5- x 3.5-cm PPM plus polyglactin 910 mesh (PPM-PGM) (n = 40). The rats were sacrificed at 1, 2, 3, and 6 months (n = 10), and an autopsy was performed to determine herniation and adhesion rates. Mesh-fascia interface was taken for histology. RESULTS: In the PPM group, 1 rat died before the end of the experiment, and at 6 months one of the 10 rats had a herniation. In the PPM-PGM group, two rats died before the end of the experiment, and two rats had a herniation after 1 month and three rats after 6 months. At 1, 2, and 3 months the adhesion score in the PPM group (median, 3; range, 2-3) did not differ from the score in the PPM-PGM group (median, 3; range, 2-3). Also, at 6 months the adhesion score in the PPM group (median, 2; range, 2-3) did not differ from the score in the PPM-PGM group (median, 3; range, 2-3). At microscopy a capsule was formed around the PP fibers, which matured over months in the PPM group. In the first month after implantation an inflammatory response was seen. Histology was similar in both groups, although in the early PPM-PGM group the inflammatory response was more evident. CONCLUSION: Interposition of PGM between PPM and viscera does not alter adhesion formation nor influences herniation rate.