An experimental study of the adhesive potential of different meshes

Adhesion Prevention to Polypropylene Meshes Using Combined Icodextrin Four Percent and Dimetindene Maleate

BACKGROUND

The use of surgical meshes in ventral hernia repair has significantly reduced hernia recurrence rates. However, when placed intraperitoneally prosthetic materials can trigger the development of peritoneal adhesions. The present experimental study evaluated the combined icodextrin 4% and dimetindene maleate treatment in preventing peritoneal adhesion formation to polypropylene and titanium-coated polypropylene meshes.

MATERIALS AND METHODS

Sixty female white rabbits were divided into four groups. A 2 × 2 cm piece of mesh was fixed to intact peritoneum in all animals through a midline laparotomy. A lightweight polypropylene mesh was implanted in groups 1 and 2 and a titanium-coated polypropylene mesh in groups 3 and 4. Groups 2 and 4 were treated, intraoperatively, with intravenous dimetindene maleate (0.1 mg/kg) and intraperitoneal solution of icodextrin 4% (20 mL/kg) and for the next 6 d with dimetindene maleate intramuscularly. The observation period lasted 15 d. Adhesion scores, percentage of mesh affected surface, tissue hydroxyproline levels, and tissue histopathology were examined.

RESULTS

All animals in group 1 and 57% of animals in group 3 presented postoperative adhesions. The combination of antiadhesives significantly reduced the extent and severity of adhesions as well as the hydroxyproline levels in groups 2 and 4 compared with groups 1 and 3. On microscopic evaluation, animals in group 1 exhibited higher inflammation scores compared with group 2, whereas animals in groups 2 and 4 had better mesotheliazation compared with groups 1 and 3.

CONCLUSIONS

The combined administration of icodextrin 4% and dimetindene maleate reduces the extent and severity of adhesions and may be successfully used to prevent adhesion formation after mesh intraperitoneal placement.

Newly Developed Polyglycolic Acid Reinforcement Unified with Sodium Alginate to Prevent Adhesion

Polyglycolic acid (PGA) mesh fabric is widely used for reinforcing injured tissues during surgeries. However, PGA induces chronic inflammation and adhesion. The purpose of this study is to develop PGA reinforcement “without PGA-induced adhesion.” We developed a reinforcement fabric unified with PGA mesh and alginate foam. The antiadhesive effects of sodium alginate foam and calcium alginate foam were evaluated in rats. Sodium alginate foam unified with PGA mesh fabric exhibited strong effects that limit the extent and severity of adhesion, whereas calcium alginate foam unified with PGA mesh was less effective in preventing adhesion. In the sodium alginate group, fibroblasts and collagen fibers around implanted sites were sparse and the material degraded rapidly by macrophage ingestion. Fibroblasts and collagen fibers play a major role in adhesion formation and their excessive proliferation results in postoperative adhesion. Thus, inhibiting their increase is the key in preventing PGA-induced adhesion. The reinforcement that is composed of PGA mesh unified with sodium alginate foam strongly inhibited PGA-induced adhesion and showed excellent handling during surgery and could be easily applied with a one-step procedure.

Comparison of cross-linked and non-cross-linked porcine acellular dermal matrices for ventral hernia repair

BACKGROUND

Porcine acellular dermal matrices (PADMs) have been used clinically for abdominal wall repair. The newer non-cross-linked PADMs, however, have not been directly compared with cross-linked PADMs. We hypothesized that chemical cross-linking affects the biologic host response to PADMs used to repair ventral hernias.

STUDY DESIGN

Fifty-eight guinea pigs underwent inlay repair of surgically created ventral hernias using cross-linked or non-cross-linked PADM. After animals were sacrificed at 1, 2, or 4 weeks, the tenacity of and surface area involved by adhesions to the repair sites were measured. Sections of the repair sites, including the bioprosthesis-musculofascia interface, underwent histologic analysis of cellular and vascular infiltration plus mechanical testing.

RESULTS

Compared with cross-linked PADM repairs, non-cross-linked PADM repairs had a significantly lower mean tenacity grade of adhesions at all timepoints and mean adhesion surface area at week 1. Mean cellular and vascular densities were significantly higher in non-cross-linked PADM at all timepoints. Cells and vessels readily infiltrated into the center of non-cross-linked PADM, but encapsulated cross-linked PADM, with a paucity of penetration into it. Mechanical properties were similar for the two PADMs (in isolation) at all timepoints; however, at the bioprosthesis-musculofascia interface, both elastic modulus and ultimate tensile strength were significantly higher at weeks 1 and 2 for non-cross-linked PADM.

CONCLUSIONS

Non-cross-linked PADM is rapidly infiltrated with host cells and vessels; cross-linked PADM becomes encapsulated. Non-cross-linked PADM causes weaker adhesions to repair sites while increasing the mechanical strength of the bioprosthesis-musculofascia interface at early timepoints. Non-cross-linked PADM may have early clinical advantages over cross-linked PADM for bioprosthetic abdominal wall reconstruction.

The role of bovine preserved peritoneum in rats ventral hernia: a histological evaluation

PURPOSE: To assess the role of preserved bovine parietal peritoneum as a material for hernia repair in a rat ventral hernia model. METHODS: An abdominal wall defect (15mm x 25mm) was created in Wistar male rats (n=40). Control animals (n=20) had the polypropylene (PP) mesh sutured into the defect, whereas bovine preserved peritoneum (BPP) was used in experimental group (n=20). After 7 and 28 days, the abdominal wall was taken off and histological studies of the amount of collagen by Sirius Red stain and morphometric evaluation consisted in quantitative analysis of the collagen by using specific software (Imagelab®). The Mann-Whitney, Kruskal-Wallis and ANOVA tests were applied for statistical analysis (pd"0.05). RESULTS: Histological examination revealed no difference between the BPP and PP groups (p = 0.55 NS). CONCLUSION: BPP is suitable for the closure of ventral hernias in rat model as shown by its morphological properties.

Incidence and Management of Perineal Hernia After Laparoscopic Proctectomy

Perineal hernia (PH) is formed by the protrusion of intra-abdominal viscera through a defect in the pelvic floor. This is a rare complication after conventional abdominoperineal resection, pelvic exanteration, proctectomy, and other pelvic procedures. The purpose of the present paper is to report 4 cases of PH after laparoscopic abdominoperineal resection for rectal cancer and to review literature data about the incidence, predisposing factors, and treatment of this challenging problem. When added to other 3 cases previously reported in the Brazilian series of laparoscopic surgery, this group of 7 cases comprises a PH incidence of 3.5% after rectal resection procedures. Surgical treatment is indicated only in symptomatic patients with no signs of cancer recurrence. Proposed methods of surgical repair include abdominal, perineal, or combined approaches to the hernia in association with the use of autologous tissues or prosthetic meshes. Preventive measures are represented by closure of the pelvic peritoneum whenever possible, primary perineal suture and wound care to avoid infection.

Evaluation of implant/host tissue interactions following intraperitoneal implantation of porcine dermal collagen prosthesis in the rat

An ideal prosthesis for ventral hernia repair should minimize development of postoperative adhesions. This study evaluates adhesion formation following intraperitoneal implantation of acellular porcine dermal collagen (PDC) and polypropylene (PP) mesh in 16 rats. Implant placement alternated left/right. Sacrifice (4 or 12 weeks) was randomized. Methods included adhesion grading (extent, severity, required dissection method) and histological evaluation. At 4 weeks, 7 of 8 PDC specimens and 0 of 8 PP implants were adhesion-free; results were identical at 12 weeks. Four-week adhesions were less developed than 12-week adhesions. Histology showed mononuclear cell foreign body reaction and disorganized collagen deposition for PPs compared to infiltration with neovascular channels and qualitatively less intense foreign body reaction for PDCs. PDC exhibits fewer adhesions and more favorable cellular response than PP in the rat.

Peritônio bovino conservado na correção de hérnia ventral em ratos: uma alternativa para tela cirúrgica biológica

OBJETIVO: Verificar a possibilidade de implantação e a capacidade de resistência tênsil do peritônio parietal bovino como tela cirúrgica na correção de hérnia ventral em um modelo animal de experimentação. MÉTODO: Utilizando 57 ratos machos Wistar, comparou-se o implante do peritônio bovino com a tela de polipropileno na correção de um defeito provocado na parede abdominal do animal. Após sete (sub-grupo A) e 28 (sub-grupo B) dias de observação, as peças foram retiradas e procedeu-se a avaliação da resistência à tração em Máquina Universal de Ensaios. Um grupo sem implante de material protético foi utilizado como controle nos testes de força tênsil. Os testes de Mann-Whitney e de Kruskal-Wallis foram utilizados e estabeleceu-se em 0,05 o nível para rejeição da hipótese de nulidade. RESULTADOS: Os testes de resistência à tração, com valores expressos em Newton, não mostraram diferenças estatísticas entre os grupos estudados, tanto no 7º quanto no 28º dia de pós-operatório, e ambos foram menos resistentes que a parede abdominal normal (p = 0,003). CONCLUSÃO: O peritônio parietal bovino apresentou resistência tênsil semelhante a da tela de polipropileno em um modelo de correção de hérnia ventral em ratos.

Comparative study of inflammatory response and adhesions formation after fixation of different meshes for inguinal hernia repair in rabbits

PURPOSE

Compare, in a rabbit model, the inflammatory response and adhesions formation following surgical fixation of polypropilene and Vypro mesh in the inguinal preperitoneal space.

METHODS

Fourteen male New Zealand rabbits, weighing between 2.000 to 2.500 g were used. A midline incision was made and the peritoneal cavity was exposed. The 2.0 x 1.0 cm polypropylene mesh was fixed in the left flank and secured to the margins with 3-0 prolene in a separate pattern. In the right flank, a 2.0 x 1.0 cm Vypro II mesh was sewn in the same way. After the post surgical period, the animals were again anesthetized and underwent laparoscopic approach, in order to identify and evaluate adhesions degree. Both fixed prosthesis were excised bilaterally with the abdominal wall segment, including peritoneum, aponeurosis and muscle and sent to a pathologist.

RESULTS

Operative time ranged from 15 to 25 minutes and no difficulties in applying the mesh were found. From the 14 polypropylene meshes fixed to the intact peritoneum, 11 had adhesions to the abdominal cavity (78.6%). Concerning Vypro mesh, 12 animals developed adhesions from the 14 with mesh fixation (85.7%). Histological examination of tissues harvested revealed fibroblasts, collagen, macrophages and lymphocytes between the threads of the mesh.

CONCLUSION

Polypropylene and Vypro mesh, when implanted in the peritoneal cavity of rabbits provoke similar amount of adhesions. Vypro mesh tissues had higher fibrosis resulting in better mesh incorporation to the abdominal wall.

Laparoscopic incisional hernia repair in a porcine model: what do transfixion sutures add?

BACKGROUND

The aim of this study was to evaluate the need for transfixion sutures during laparoscopic ventral hernia repair with mesh.

METHODS

Incisional hernias were created in 14 Yucatan mini-pigs. Animals were randomized to undergo laparoscopic hernia repair either with spiral tacks alone (Tacks) or with tacks and 4 Prolene transfixion sutures (Sutured) using Composix E/X mesh (Davol Inc.). At 4 weeks, exploratory laparoscopy was performed to assess the repair and score adhesions. The abdominal wall was harvested for tensile strength analysis and histologic evaluation. Continuous variables were compared using a two-tailed nonpaired t-test. Results are presented as mean +/- standard deviation.

RESULTS

The mean hernia size was 8.5 +/- 0.5 cm by 5.5 +/- 0.7 cm, with no difference between groups. The operative time was significantly longer ( p = 0.006) for the Sutured group (62.1 +/- 16.8 min) than for the Tacks group (32.3 +/- 7.0 min). The number of tacks per repair was equivalent between groups. At necropsy, the mesh in all cases was well incorporated, reperitonealized, and without evidence of migration. No hernias recurred. However, the Sutured group had a significantly ( p < or = 0.05) higher adhesion score (5.4 +/- 3.3) than the Tacks group (2.0 +/- 2.7). The tensile strength of the repair zone was no different between groups (Sutured 4.8 +/- 1.5 N/cm, Tacks 3.8 +/- 1.4 N/cm). On histologic examination, the ratio of inflammatory cells to fibroblasts was similar between groups (Sutured 0.2 +/- 0.6, Tacks 0.2 +/- 0.3). Only 82% of tacks in each group penetrated the fascia, and the depth of tack penetration was similar between groups (Sutured 3.7 +/- 0.3 mm, Tacks 3.9 +/- 0.4 mm).

CONCLUSIONS

In a porcine model, the use of transfixion sutures was associated with longer operative times and more adhesions, without improvement in tensile strength or mesh incorporation. A human clinical trial is needed to determine the optimal method of securing abdominal wall mesh.