Human Peritoneal Membrane Controls Adhesion Formation and Host Tissue Response Following Intra-Abdominal Placement in a Porcine Model

Comparative study of fibrosis induced by Marlex®, Parietex Composite®, Vicryl® and Ultrapro® meshes1

PURPOSE

To evaluate the fibrosis induced by four different meshes: Marlex®, Parietex Composite®, Vicryl® and Ultrapro®.

METHODS

Histological cutouts of abdominal wall were analyzed with polarized light 28 days after the meshes implants and colorized by picrosirius to identify the intensity of collagen types I and III, and their maturation index.

RESULTS

When the four groups were compared, the total collagen area analyzed was bigger in groups A and D, with no difference between them. The collagen type I density was bigger in group A, with an average of 9.62 ± 1.0, and smaller in group C, with an average of 3.86 ± 0.59. The collagen type III density was similar in groups A, B and C, and bigger in group D. The collagen maturation index was different in each of the four groups, bigger in group A with 0.87, group B with 0.66, group D with 0.57 and group C with 0.33 (p = 0.0000).

CONCLUSION

The most prominent fibrosis promotion in the given meshes was found on Marlex® (polypropylene mesh) and the Parietex Composite® (non-biodegradable polyester); the collagen maturation index was higher in the Marlex® mesh, followed by Ultrapro®, Parietex Composite® and Vicryl® meshes.

Characteristics of the fibroplasia and collagen expression in the abdominal wall after implant of the polypropylene mesh and polypropylene/polyglecaprone mesh in rats

PURPOSE

To compare fibroplasia and the resistance of the abdominal wall when polypropylene meshes and polypropylene/poliglecaprone are used.

METHODS

Seventy-seven male Wistar rats were divided into three groups: Control Group (for resistance); Group E (polypropylene mesh); and Group U (polypropylene/poliglecaprone mesh). The animals in Groups E and U had a standard muscular and aponeurotic defect, with integral peritoneum, and correction with the mesh. Measurements were taken 4, 7, 14, 28 and 56 days after surgery. The resistance, and collagen density were studied.

RESULTS

Resistance on the 56th day was similar in both meshes. The gain in resistance described an ascending curve for the polypropylene mesh and was irregular in the case of the polypropylene/poliglecaprone. Fibroplasia showed a gain in type I and type III collagen in both groups (p<0.001). Collagen III stabilized in the 14th day and collagen I continued to ascend.

CONCLUSIONS

The gain in resistance of the polypropylene mesh is regular and ascending, whereas the polypropylene/poliglecaprone is not regular. The final resistance of both meshes is similar; the collagen density increases over time, and show the same inflammatory potential.

The use of Vicryl mesh in a porcine model to assess its safety as an adjunct to posterior fascial closure during retromuscular mesh placement

BACKGROUND

Posterior component separation has become a common approach to complex abdominal wall reconstructions. This technique includes creation of an extraperitoneal retromuscular space for subsequent large synthetic mesh reinforcement. In certain cases, when complete restoration of "posterior" layer is precluded by significant tissue loss/damage, one proposed strategy is to replace the posterior fascia with an absorbable synthetic polyglactin (Vicryl) mesh. However, the safety of this strategy to prevent mesh-related visceral complication is unknown. Herein, we aimed to characterize mesh-viscera adhesion profiles and host tissue response of synthetic mesh either exposed directly to the viscera, or protected with Vicryl mesh.

METHODS

Using adult Yorkshire pigs, 5 × 5 cm pieces of mesh were secured to the intact peritoneum in each of the four quadrants (n = 6 pigs, 24 mesh samples). The study groups were Vicryl (V), Marlex (M), Softmesh (S), Marlex + Vicryl construct (MV), Softmesh + Vicryl construct (SV). The self-made composite meshes were then implanted with the Vicryl side facing the exposed viscera. The pigs were survived for 60 days. At necropsy, grossly, the extent and tenacity of visceral adhesions were evaluated using established scales. Histologically, all specimens for fibrous encapsulation on the visceral surface of the mesh were reviewed by an experienced pathologist blind to meshes used.

RESULTS

At necropsy, all Vicryl meshes were completely resorbed. The mean adhesion and tenacity scores for M and MV were 1.8 and 1.1 (P > 0.05), 2.0 and 1.5 (P > 0.05), respectively; while the mean adhesion extent scores and tenacity scores for S and SV were 2.0 and 1.2 (P > 0.05), 2.0 and 1.7 (P > 0.05). No significant difference in adhesion extent and tenacity was observed between Synthetic and Vicryl composite mesh groups. Histologically, Marlex + Vicryl mesh and Softmesh + Vicryl mesh constructs had thicker fibrous capsules than the corresponding unprotected Marlex and Soft mesh implants. Furthermore, visceral adhesions in the composite groups were noted to be to the fibrous capsule and not synthetic mesh itself.

CONCLUSION

Utilization of the absorbable polyglactin (Vicryl) mesh as a separating layer between a synthetic mesh and intestines, did not reduce adhesions across various mesh types and composites. Histologically, however, a thick fibrous capsule replaced the Vicryl mesh and may be an important layer to prevent intestinal erosion into retromuscular synthetic meshes.

Prospective repair of Ventral Hernia Working Group type 3 and 4 abdominal wall defects with condensed polytetrafluoroethylene (MotifMESH) mesh

BACKGROUND

Treatment of clean-contaminated and contaminated ventral hernia defects remains controversial. Newer prosthetic materials may play an important role in these patients.

METHODS

Ten patients with Ventral Hernia Working Group types 3 and 4 were prospectively enrolled and subsequently treated with direct supported repairs with condensed fenestrated polytetrafluoroethylene mesh. The primary outcome was hernia occurrence at 1 year after surgery. Secondary outcomes included surgical site infection, surgical site occurrence, medical complications, pain, and other patient-reported outcomes.

RESULTS

There were no immediate postoperative infections and one minor postoperative hematoma treated in the office. One patient required delayed mesh removal 9 months after placement. Importantly, the mesh removal procedure was straightforward because of the material properties of the mesh. Of the 9 patients still with mesh, there were no hernia recurrences at the repair site with one full year of follow-up.

CONCLUSION

Contaminated and clean-contaminated abdominal wall defects can be effectively and durably treated with condensed polytetrafluoroethylene mesh.

Pilot study evaluating the efficacy of AlloMEM™ for prevention of intraperitoneal adhesions and peritoneal regeneration after loop ileostomy

OBJECTIVE

This study was designed to evaluate the feasibility of AlloMEM™, a novel lyophililzed human peritoneal membrane, at peritoneal reconstitution, and decreasing adhesion formation after temporary loop ileostomy.

METHODS

In a pilot study, ten patients had AlloMEM™ used during elective formation of a temporary diverting loop ileostomy for benign or malignant colorectal disease. A blinded investigator and the operating surgeon analyzed the change in adhesion formation and peritoneal remodelling using ileostomy mobilization time and a 5-point adhesion scale grading intra-abdominally and at the subcutaneous and fascial levels.

RESULTS

The mean body mass index was 31 [standard deviation (SD) 5.6], and 40 % of patients had previous abdominal surgery. Ileostomies were reversed after a mean 14 weeks (SD 6.0). The mean ileostomy mobilization time was 27.2 min (SD 12.0). From baseline to ileostomy reversal, there were significant increases in adhesions at the subcutaneous (p = 0.0002) and fascial levels (p = 0.0024). The increased subcutaneous adhesions were associated with improved peritoneal remodeling. There was no significant increase in adhesions from baseline to ileostomy reversal at the intra-abdominal points (p = 0.9393) or around the ileostomy site (p = 0.6128). The median hospital length of stay was 2.6 days (range, 2-3). A single adverse event related to product packaging led to redesign of the packaging process.

CONCLUSIONS

Use of AlloMEM™ in ileostomy closures suggested improvement in adhesions around the fascia and promotion of peritoneal remodeling. AlloMEM™ was safe, feasible, and easy to use in this pilot study. Comparative research is needed to assess the outcomes with this novel product.

Current strategies and future perspectives for intraperitoneal adhesion prevention

INTRODUCTION

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

DISCUSSION

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

Intraperitoneal adhesions--an ongoing challenge between biomedical engineering and the life sciences

Peritoneal adhesions remain a relevant clinical problem despite the currently available prophylactic barrier materials. So far, the physical separation of traumatized serosa areas using barriers represents the most important clinical strategy for adhesion prevention. However, the optimal material has not yet been found. Further optimization or pharmacological functionalization of these barriers could give an innovative input for peritoneal adhesion prevention. Therefore, a more complete understanding of pathogenesis is required. On the basis of the pathophysiology of adhesion formation the main barriers currently in clinical practice as well as new innovations are discussed in the present review. Physiologically, mesothelial cells play a decisive role in providing a frictionless gliding surface on the serosa. Adhesion formation results from a cascade of events and is regulated by a variety of cellular and humoral factors. The main clinically applied strategy for adhesion prevention is based on the use of liquid or solid adhesion barriers to separate physically any denuded tissue. Both animal and human trials have not yet been able to identify the optimal barrier to prevent adhesion formation in a sustainable way. Therefore, further developments are required for effective prevention of postoperative adhesion formation. To reach this goal the combination of structural modification and pharmacological functionalization of barrier materials should be addressed. Achieving this aim requires the interaction between basic research, materials science and clinical expertise.