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Introduction: Despite the advantages offered by meshes, their use in abdominal wall repair can promote adhesions and damage the intra-abdominal viscera. This study was designed to assess the behavior at the peritoneal interface of several composite prostheses using sequential laparoscopy to monitor the real-time adhesion formation process., Materials and Methods: Three composite prostheses, Parietex Composite (n=8), Sepramesh (n=8) and PL-PU 99 (n=8), were used to repair 7 x 5 cm defects created in the abdominal wall of 24 New Zealand white rabbits. The area occupied by adhesions at 3, 7 and 14 days after prosthesis placement was established by tracing the adhesions onto a polyethylene template, using images obtained from sequential laparoscopy, and subjecting it to image analysis. At 14 days, the animals were sacrificed and specimens of the prostheses plus adjacent host tissue were obtained for histological and morphometric tests., Results: Adhesion formation was laparoscopically observed to stabilize between 7 and 14 days post-implant, with no increase in adhesions produced at 14 days. The Parietex and PL-PU99 meshes showed significantly lower proportions of adhesions (0.55 +/- 0.06% and 0.27 +/- 0.20% respectively) than Sepramesh (18.55 +/- 1.96%). All three composites induced similar host tissue ingrowth and mesothelialization of the peritoneal prosthetic surface., Conclusions: a) The three prostheses tested showed optimal behavior at the peritoneal interface; b) the critical period when most adhesions form is the first week after implant; c) these biomaterials are suitable for use in laparoscopic ventral hernia repair.

Background/aims: This study was designed to evaluate the extent of adhesion formation to prostheses fixed with spiral tacks and to establish whether the use of Ringer's lactate or icodextrin could prevent these adhesions., Methods: 24 New Zealand white rabbits weighing around 3,000 g were implanted with a 7 x 5 cm patch of ePTFE (DualMesh) through a midline laparotomy. The prosthesis was fixed to the intact peritoneum using spiral tacks. Three study groups were established according to whether the animals were: implanted with ePTFE fixed with spiral tacks or implanted with ePTFE fixed with spiral tacks and simultaneously administered Ringer's lactate or 4% icodextrin in the peritoneal cavity. Adhesion formation and prosthetic behavior at the prosthesis/peritoneal interface were evaluated and quantified by sequential laparoscopy performed at 3, 7 and 14 days., Results: Adhesions generally formed on the tacks and were classified as the fully integrated type. No significant differences were observed in terms of the extent of adhesions or of neoperitoneal thickness between control animals and those receiving Ringer's lactate or icodextrin., Conclusions: (a) Prosthesis-fixing tacks induced adhesions; (b) the use of substances such as icodextrin or Ringer's lactate does not seem to diminish adhesion formation, and (c) the use of icodextrin offered no benefits over that of Ringer's lactate solution., (Copyright (c) 2006 S. Karger AG, Basel.)

The component of a composite prosthesis, which makes contact with the visceral peritoneum, can be reabsorbable or non-reabsorbable, and laminar or reticular. This study was designed to determine whether the composition of this second, barrier component could improve its behavior at this interface. Abdominal wall defects in rabbits were repaired using a polypropylene prosthesis (PP), or the composites Sepramesh (PP + h) or Vicryl (PP + v). Fourteen days after surgery, the implants were evaluated by light and scanning electron microscopy, and immunohistochemistry. Prosthetic areas occupied by adhesions (PP: 71.08 +/- 5.09, PP + h: 18.55 +/- 4.96, P + v: 69.69 +/- 16.81%), neoperitoneal thickness (PP: 256.17 +/- 21.68, PP + h: 83.11 +/- 19.63, PP + v:213.72 +/- 35.90 microm) and macrophage counts (PP: 8.73 +/- 1.16, PP + h: 27.33 +/- 4.13, PP + v: 31.24 +/- 3.08%) showed significant differences (P < 0.05). The tested biomaterials induced an optimal recipient tissue infiltration. Least adhesion formation was observed on the PP + h implants. This suggests that the second component, although reabsorbable, should be smooth in structure.

In a composite prosthesis, the component placed at the peritoneal interface takes the form of a physical or chemical barrier. In this experimental study performed on the white New Zealand rabbit, several composites were examined to establish the effectiveness of these barriers at impeding adhesion formation. The biomaterials tested were two polypropylene prostheses (PP) with the physical barriers of expanded polytetrafluoroethylene or polyurethane (PP + ePTFE and PP + PU) and two prostheses (one polyester and the other PP) with the absorbable chemical barriers of polyethylene glycol/glycerol and hyaluronate, respectively (PO + gl and PP + hy). The composites were used to repair 7 x 5 cm defects created in the abdominal wall of the animals by placing the implant in contact with the visceral peritoneum and the subcutaneous tissue and fixing it to recipient tissue by 4/0 polypropylene running suture. Fourteen days after surgery the animals were sacrificed and specimens were taken for light microscopy and scanning electron microscopy. Adhesions developing at the prosthesis/visceral peritoneal interface were quantified. All the prostheses induced optimal mesothelialization. Composites with physical barriers behaved similarly in terms of provoking adhesions. However, the prostheses with chemical barriers differed in their effectiveness at preventing adhesions. Overall, the best results were obtained with the PP + PU composite., (Copyright 2005 Wiley Periodicals, Inc.)

Background: This study was designed to establish whether the spatial structure of a prosthesis conditions its behavior at the peritoneal level., Methods: Abdominal defects comprising all the wall (except skin) were created in rabbits and repaired with a laminar (DM) or reticular (CV-4) ePTFE-prosthesis. Fourteen days postimplant, specimens were obtained for scanning electron and light microscopy. Peritoneal adhesions, resistance to traction, and neoperitoneum thickness were quantified., Results: Adhesions to CV-4 were firm and integrated within surrounding tissue; only scarce adhesion formation was observed for DM. Adhesion area was significantly greater (P <0.01) in the CV-4 than in DM (7.00 +/- 2.6; 0.15 +/- 0.08 cm(2)). The neoperitoneum was organized for DM and disorganized for CV-4. This layer was significantly thicker (P <0.05) in DM than CV-4 (455 +/- 3.4; 70 +/- 3.1 microm). The CV-4 showed a greater resistance to traction than the DM (26.75 +/- 3.71; 14.11 +/- 3.71 N; P <0.05)., Conclusions: The structure of a biomaterial, rather than its chemical composition, modulates behavior at the peritoneal interface.

This study was designed to evaluate the behavior of a new composite polypropylene-polyurethane (PL-PU99) when placed in direct contact with the visceral peritoneum during the repair of an abdominal wall defect. Full-thickness abdominal wall defects (7 x 5 cm) were created in 36 anaesthetized white New Zealand rabbits. The defects were repaired with polypropylene prostheses or PL-PU99 prostheses (comprised of PL and a polyurethane sheet glued to the PL with acrylic adhesive) to establish two study groups (n = 18 each). Animals were sacrified 14, 30, or 90 days after implantation and prosthesis/surrounding tissue specimens were subjected to light and electron microscopy and morphometric analysis of the newly formed peritoneum. Immunohistochemical analysis was performed using the rabbit specific monoclonal antibody RAM-11. The biomechanical strength of the implants was also assessed. Firm adhesions were detected in the PL implants, whereas adhesions were practically non-existent in the PL-PU99 implants. The surface area covered by adhesions was greater (p < 0.01) in the PL group (7.36 vs. 0.11 cm2). The neoperitoneum formed after the implantation of a PL prosthesis was disorganized in structure, whereas that formed at the interface with the PL-PU99 prosthesis was structurally similar to the host peritoneum. The excellent performance of the PL-PU99 prosthesis shown in this study warrants further investigation into its use for the repair of abdominal wall defects when the prosthetic patch needs to be placed in contact with the intestinal loops.

The present study compared the performance of three composite prostheses used to repair abdominal wall defects in rabbits. Two of them [Parietex Compositereg (PC) and Composixreg (CS)] are commonly used in clinical practice and one was designed by the present team (PL-PU99). At 14 and 90 days postimplant, specimens were obtained for morphological, macrophage response (RAM-11) and morphometric and biomechanical analysis. The prosthetic area covered by adhesions was significantly greater (p < 0.05) in the CS group (6.83 plus minus 2.31 cm(2)) than in PC (0.11 +/- 0.02 cm(2)) or PL-PU99 (0.10 +/- 0.07 cm(2)). At 14 days, it was observed a homogeneous, organized, well-vascularized neoperitoneum that was significantly thicker (p < 0.05) in PL-PU99. Except in the CS implants, this layer was covered by a continuous mesothelium. All three composites achieved good recipient tissue integration. Highest macrophage levels were recorded at 14 days with significantly higher values in the PL-PU99 prosthesis. Biomechanical strength was significantly greater (p < 0.05) in CS at two weeks postimplant, but it was similar at 90 days. These findings suggest that the three composites show ideal integration with host tissue, along with similar biomechanical strength at 90 days, and significantly higher adhesion formation is induced by the CS prosthesis, possibly due to incomplete mesothelialization of the lower prosthetic surface., (Copyright 2002 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 63: 182--190, 2002; DOI 10.002/jbm.10123)

Objective: To compare the behaviour of two composite biomaterials in rabbit peritoneum., Design: Animal study., Setting: Faculty of Medicine, University of Alcalá, Spain., Animals: 14 white New Zealand white rabbits divided into 2 groups of 7 each., Interventions: Defects (7 x 5 cm) involving all the layers of the abdominal wall were created and repaired using Parietex Composite or Vypro prostheses. Fourteen days after implantation, prosthetic specimens were examined by microscopy, and morphometric and biomechanical analysis., Main Outcome Measures: Infection, healing, development of adhesions, and histological appearance of the interface., Results: Firm adhesions were detected after the implant of Vypro while adhesion were loose in the Parietex group. The mean (SD) prosthetic surface area covered by adhesions was significantly greater in the Vypro group 22.3 (2.8) compared with 0.2 (0.02), p <0.01). The neoperitoneum formed after the implant of Parietex was well-organised and homogeneous and covered by a typical mesothelium, while in the Vypro it was disorganised, with a rough texture composed of prosthetic filaments and nodes. The neoperitonum was thicker in the Parietex group 154.0 (5.4) compared with 50.8 (2.3), p <0.05) while higher biomechanical resistance values were recorded in the Vypro group 30.4 (1.9) compared with 15.0 (2.73), p <0.05)., Conclusions: While both biomaterials integrated well with tissue, Parietex behaved better at the peritoneal interface.

Prosthetic materials currently used to repair abdominal wall defects occasionally must be placed in direct contact with the visceral peritoneum. The prosthesis-peritoneum interface is the site of several possible problems, including the formation of adhesions and erosion of the intestinal loops, which may lead to the formation of fistulas. This investigation was designed to compare the behavior of two prosthetic biomaterials in composite form at the level of the peritoneum. Defects (7 x 5 cm) were created in the abdominal wall of 18 white New Zealand rabbits weighing approximately 2500 g. The defects (involving aponeurotic and muscular planes and the parietal peritoneum) were repaired with polypropylene (PL) + ePTFE (Preclude dura substitute) or Parietex composite (PC) prostheses. The prostheses were secured to the edges of the defect by continuous PL sutures interrupted at the corners of the implant. Three study groups were established according to the type of implant: group I (n = 6) (controls)--PL; group II (n = 6)--PL + ePTFE; and group III (n = 6)--PC. The animals were sacrificed 14 days after implant, and the prostheses were examined by light microscopy and scanning electron microscopy (SEM). The formation of adhesions at the prosthesis-visceral peritoneum interface were quantified according to a protocol previously described by us. The biomechanical resistance of the implant was evaluated using strips comprising prosthetic material and anchorage tissue. The Mann-Whitney U-test was used to compare data corresponding to each group. There was no postimplant mortality. No infection or rejection of the prosthesis was observed in any of the animals. Firm adhesions were detected in the PL implants, whereas in the PL + ePTFE and PC implants the adhesions were loose. The mean prosthetic surface areas covered by adhesions were 7.67, 0.10 and 0.19 cm2 for groups I, II, and III, respectively, showing a significant difference between values corresponding to groups I and II and to groups I and III (p < 0.05). Comparison of values recorded for groups II and III yielded no significant difference (p > 0.05). In groups II and III, the neoperitoneum was homogeneous and composed of organized and vascularized connective tissue covered by a mesoendothelium that was interrupted by accumulations of fibroblasts and white blood cells. In contrast, a disorganized neoperitoneum of rough texture was observed in the group I specimens. At times, areas of hemorrhage and necrosis corresponding to the sites of adhesion formation could be observed. Resistance to traction of composite implants (mean +/- SD: 15.72 +/- 1.32 and 15.89 +/- 2.73) was similar to that of the PL implants (15.03 +/- 2.92) (Mann-Whitney U-test, p < 0.05). It may be concluded that (1) composite prostheses show optimum behavior in terms of adhesion formation at the prosthesis-visceral peritoneum interface; (2) the neoperitoneum formed after the implant of a composite prosthesis almost physically and functionally replaces the normal peritoneum; (3) a significantly greater degree of peritoneal regeneration is achieved after implant of a PC prosthesis; and (4) there was no significant difference regarding biomechanical resistance between PL prostheses and PL + ePTFE and Parietex composites.

One of the drawbacks of using macroporous polypropylene prostheses in the repair of the abdominal wall is the formation of adhesions with the viscera. However, polytetrafluoroethylene (PTFE) has low adhesion formation, although it provides less resistance to traction in the repaired zone. The aim of the present study was to reduce the formation of adhesions to a polypropylene implant Prolene (PL) by introducing a nonporous expanded PTFE layer (Preclude Dura-Substitute) (PR) between the polypropylene prosthesis and the abdominal viscera. The scarring process and resistance to traction in the repaired zone were also evaluated. Thirty-six rabbits were divided into three groups and were treated as follows: group I, a PR patch (7 x 5 cm) was secured to the parietal peritoneum; group II, an abdominal wall defect (7 x 5 cm) was created and repaired using a PL patch; group III, an abdominal wall defect was as in group II and was repaired using a combined PR/PL prosthesis. Specimens were evaluated at 14, 30, 60, and 90 days postimplant for extent of adhesion formation and morphological analysis was performed using light and scanning electron microscopy. Biomechanical resistance of the implant was evaluated using strips comprising prosthetic material and anchorage tissue. Group I and group III prostheses showed loose adhesions only, but group II adhesions were firmly attached. The mean surface areas covered by adhesions were 0.08 cm2 (group I), 7.67 cm2 (group II), and 0.1 cm2 (group III). PR implants (group I) were encapsulated by organized tissue. In group II the formation of disorganized tissue invading the prosthesis was observed. In group III the PR impeded the growth of disorganized scar tissue and the lower surface of the implant was covered by an orderly neoperitoneum. Resistance to traction of the double implants (group III) (mean +/- SD, 33.32 +/- 0.9 N) was similar to that of the Prolene implants (group II) (33.76 +/- 0.46 N) (Mann-Whitney U test, p < 0.05). We concluded the presence of a PR layer between the PL implant and viscera greatly reduced the incidence of adhesion formation without affecting the high resistance to traction provided by the PL implant or the evolution of the scarring process.

One of the alternatives for the repair of large incisional hernias is the use of a prosthetic material. The present retrospective study relates the experience acquired for treatment of large incisional hernias (hernial orifice > 10 cm) with ePTFE prostheses. Thirty-eight massive incisional hernias were repaired using ePTFE 1 mm thick Soft Tissue Patches. Twenty-four patients received a prosthetic patch of 10 x 15 cm, 13 a patch of 15 x 20 cm, and 1 a patch of 20 x 30 cm. In 30 cases the ePTFE was sutured to the recipient tissues with a double row of polypropylene stitches. For the first eight interventions the ePTFE was secured using a single row of polypropylene sutures. Pathologic studies of biopsies from patients who had undergone surgical reintervention at 40 days, 12 months, and 48 months, respectively, were done using light microscopy, scanning electron microscopy, and immunohistochemistry with human antimacrophage antibodies KP-1. The follow-up period for all patients was between 18 and 72 months. There was no perioperative mortality. No infection or rejection of prostheses was recorded. Seroma was present in four patients. Computed tomography was performed for evaluation purposes on 10 randomly selected patients (mean postoperative delay 1-4 years) and showed the ePTFE encapsulated by newly formed tissue. One of the patients suffered from mechanical intestinal obstruction 40 days after implant and suffered a recurrence a year later. Three recurrences at the patch-recipient tissue interface where the ePTFE had been secured with a single row of polypropylene stitches were recorded after 8, 12, and 28 months. At 40 days good integration of the biomaterial was observed in the newly formed tissue. On both sides of the implant an accumulation of four to six strata of cells was appreciable. Some of them were labeled with KP-1. Cell infiltration of the prosthesis was restricted to the most exterior third of the patch. There was no colonization at the patch-recipient tissue interface. At 12 and 28 months the cell barrier had almost disappeared. KP-1-labeled macrophages were scarce. Scanning electron microscopy revealed a well defined peritoneum. It may be concluded that: (1) a double suture row is recommended to secure the prosthesis; (2) ePTFE provides an adequate substrate for the formation of scar tissue; and (3) the macrophage response induced by the ePTFE decreases with time.

The porosity of the prosthetic biomaterials used to repair defects in the abdominal wall seems to influence the tissue repair process insofar as tissue integration of the prosthetic material and the formation of adhesions with abdominal viscera are concerned. We studied the behaviour of a new type of polytetrafluoroethylene prosthesis used for the repair of abdominal wall defects. Dual Mesh (DM), which has two different faces; one face has a porosity between 30 and 60 microns, while the other is non-porous. In 20 New Zealand White rabbits, a full-thickness (except skin) 7 cm x 5 cm defect was created in the anterior abdominal wall that was repaired with DM. At 14, 30, 60 and 90 days, samples were obtained and studied by light and scanning electron microscopy. An immunohistochemical study was made with antibody anti-rabbit macrophages (RAM-11). Tensile strength was measured with an Instron tensiometer using 2-cm-wide strips obtained parallel to the shorter axis of the implant. DM induced little tissue adhesion to the material on the visceral peritoneum interface and was surrounded by organized repair tissue. The biomaterial was integrated in the repair tissue on the subcutaneous interface, but not on the peritoneal interface. The macrophage response decreased between days 14 and 90 (P < 0.001). Tensile strength increased significantly (P < 0.05) at every study period. We conclude that the DM prosthesis has little tendency to formation of visceral adhesions, the DM prosthesis was well tolerated by the receptor organism and the tensile strength of the prosthesis/receptor tissue interface increased with time.

The postimplantation peritoneal adhesions formed with some biomaterials continue to represent a serious problem when these biomaterials are placed in contact with the organs of the abdominal cavity. The objective was to test the effects of phosphatidylcholine (PC) in the attempt to modulate the adhesive process, thus improving the biomaterial/visceral peritoneum interface. We have carried out an experimental study using the New Zealand white rabbit, implanting a 7 x 5 cm2 polypropylene prosthesis into the anterior abdominal wall in such a way that it replaced all the tissue layers and was in contact with the intestinal loops. Three study groups were established: group I (control), in which only implantation of the biomaterial was performed; group II, in which the prosthesis was pretreated with a solution of PC; and group III, in which the implants were treated as in group II and the animals underwent intraperitoneal administration of 10 ml of the same solution. The animals were killed on postimplantation day 14. The total surface of the prosthesis occupied by adhesions was measured and light and scanning electron microscopy were performed to analyse the healing process. In comparison with the controls, groups II and III did not present significant differences with respect to the resistance or extension of the adhesions. The microscopic results showed a rapid formation of disorderly and well-vascularised scar tissue enveloping the entire prosthesis. Thus, PC was unable to modulate the process of adhesion formation between the prosthesis and the organs of the abdominal cavity; nor did it induce changes in the cells of sufficient importance to alter the results of the healing process in the presence of this biomaterial.

The biomaterial ePTFE is widely used in the clinical environment for vascular replacement or bypass, as well as in the repair of tissue defects, especially those involving the abdominal wall. The objective of this study was to evaluate the healing response to ePTFE prostheses implanted into a circulatory interface and a tissue interface, each in a different animal species. For vascular implants, the Sprague-Dawley rat (n = 60) was used, while the New Zealand white rabbit (n = 20) was used in the tissue replacement model. In the former, a vascular microprosthesis measuring 5 mm in length and 1 mm in internal diameter, having a porosity of 30 microns, was implanted into the common iliac artery. In the rabbit, a 7 x 5-cm fragment of ePTFE (Soft-Tissue Patch) was implanted into a defect in anterior abdominal wall that involved all the tissue layers. In this case, the prosthesis was left touching the intestinal loops. The implants were studied between 14 and 90 days of postimplantation by means of light microscopy, scanning electron microscopy, and immunohistochemistry. The latter involved the use of anti-rat (MAC-341) and anti-rabbit (RAM-11) macrophage-specific monoclonal antibodies. The behavior of the ePTFE in the different interfaces (vascular and abdominal wall) was similar with respect to the following aspects: the prosthesis presented a process of encapsulation which was more intense on the outer surface; colonization of the implant was limited to the outermost two thirds, with minimal invasion of the middle portion; colonization was absent on the edges of the prosthesis; collagenization of the interstice of the mesh occurred late; the foreign body reaction taking place on the outer surface was similar in both interfaces, with formation of a barrier consisting of macrophages and giant cells that did not penetrate the prosthesis; and, finally, in neither of the two models was vascular colonization of the PTFE prosthesis observed; rather, the angiogenic process was limited to the periprosthetic zones. The integration of the implant made of ePTFE is similar despite the differences in interfaces and the use of different animal species. The macrophage response does not determine the success or failure of the implant.

The behaviour of two biomaterials polytetrafluoroethylene (PTFE) and polypropylene (PL) has been studied, focussing especially on the macrophage response to the implant, as well as on certain aspects of the process of scar formation. A total of 24 animals (white New Zealand rabbits) received prostheses implanted into the anterior abdominal wall in such a way as to involve every layer over an area of 7 cm x 5 cm. The interfaces formed with the visceral peritoneum, subcutaneous tissue layer and the recipient muscle-aponeurotic tissue were assessed. The techniques employed were light microscopy, scanning electron microscopy and immunohistochemical methods, the latter using a monoclonal antibody specific for rabbit macrophages (RAM-11). From the results obtained, it can be seen that: (a) the structure of PL allows its total integration with the reparative tissue, while PTFE becomes encapsulated, on both the subcutaneous and the peritoneal aspects, by orderly connective tissue; (b) the macrophage response, determined on the basis of the presence of labelled macrophages, shows a similar pattern in both biomaterials; and (c) angiogenesis is very intense in the PL mesh, whereas the PTFE prosthesis undergoes almost no vascular colonization.