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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 (p0.01) 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.

Resumen Introduccion Disenamos dos tipos de protesis, utilizando un unico biomaterial (politetrafluoroetileno expandido [PTFEe]), con la finalidad de demostrar que las diferencias estructurales entre ambas producian distintos comportamientos en la interfaz peritoneal. Material y metodos Se crearon defectos abdominales de 7 x 5 cm, en conejos macho (Nueva Zelanda), que comprendian todos los planos de la pared, excepto la piel. Para la reparacion se utilizaron dos protesis de PTFEe disenadas por nuestro grupo: una reticular (CV-4-mesh) y otra de tipo composite (PTFEe- composite). Se obtuvieron muestras a 14 y 90 dias postimplante para su estudio morfologico, ultrastructural, formacion adherencial, espesor del neoperitoneo y comportamiento biomecanico. Resultados El area ocupada por las adherencias fue significativamente mayor (p Conclusiones Cambios en la estructura de un mismo biomaterial modulan el comportamiento en la interfaz peritoneal.

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.

Resumen Introduccion Las protesis macroporosas, tipo polipropileno (PL), empleadas para la reparacion de defectos en la pared abdominal, tienen en algunas ocasiones que ser implantadas en contacto con el peritoneo visceral. La interfase protesis/peritoneo visceral puede generar problemas en cuanto a formacion adherencial con posibilidad de formacion de fistulas. El objetivo del presente trabajo ha sido realizar un estudio sobre el comportamiento en esta interfase de una nueva protesis disenada en forma de composite (PL-PU99) por nuestro grupo de investigacion. Material y metodos Se han empleado 30 animales (conejo blanco Nueva Zelanda) de un peso aproximado entre 2.000 y 2.500 g. Se crearon defectos de 7×5 cm en la pared anterior del abdomen que comprendian todos los planos (aponeurotico, muscular y peritoneo parietal), siendo reparados los mismos con protesis de PL y PL-PU99. La piel que quedo cubriendo la protesis fue cerrada con una sutura de polipropileno 3/0. La protesis PL-PU99 es un composite formado por tres componentes: una protesis de PL de un poro de 1 mm y una lamina de poliuretano (colocada en contacto con el peritoneo visceral), unidas ambas por un pegamento acrilico. Se establecieron dos grupos de estudio: grupo I (n = 15) o control, implantes de PL, y grupo II (n = 15), implantes de PL-PU99. Los animales fueron sacrificados a los 14, 30 y 90 dias de la intervencion quirurgica. Se efectuaron estudios a microscopia optica, electronica de barrido (SEM) y transmision (MET), inmunohistoquimica y morfometria del neoperitoneo. Asimismo, se cuantificaron las adherencias en la interfase protesis/peritoneo visceral. El estudio biomecanico se realizo con un tensiometro Instron (TT-DM-1118). El analisis estadistico se efectuo empleando los test de la t de Student-Newman- Keuls y la U de Mann-Whitney. Resultados No hubo mortalidad en los animales intervenidos ni presencia de infeccion o rechazo de los implantes. Las adherencias fueron firmes en los implantes de PL y practicamente inexistentes en los de PL-PU99. La superficie cubierta por adherencias fue de 7,18 ± 1,11 y 0,11 ± 0,02 cm2, respectivamente, para los grupos I y II, existiendo diferencias significativas entre ambos grupos (p Conclusiones a) la protesis PL-PU99 tiene un comportamiento optimo en cuanto a formacion adherencial, en la interfase protesis/peritoneo visceral; b) el neoperitoneo formado con esta protesis sustituye casi fisica y funcionalmente al peritoneo normal, y c) la resistencia biomecanica obtenida no presenta diferencias entre el grupo control y el grupo objeto de estudio.

This paper presents an innovative procedure, capable to automatically generate virtual environments which are applicable to art galleries, museums or similar facilities, and suitable for web-based promotions of artists and their works. The presented system is part of the outcome of an interdisciplinary research for low-cost and platform independent solutions to combine art with virtual reality with the aim to promote artist works through new interaction metaphors which include dynamic 3D visualization of works of art with associated structured multimedia information.

Poor mechanical properties of biological tissue are known to cause wear, leading to the failure of cardiac bioprostheses made of calf pericardium. Different chemical agents such as sodium dodecyl sulfate (SDS) are presently being tested as possible inhibitors of the calcification process. The objective of this report was to determine the mechanical behavior of calf pericardium treated with SDS for 24 h and the influence of the suture on the mechanical properties of the tissue. Forty-eight samples were tested: 24 subjected to a standard treatment with glutaraldehyde (12 sewn with 4/0 silk suture thread) and 24 incubated with SDS for 24 h (12 sewn with the same suture thread). Each sutured and non-sutured sample was cut into two strips to yield paired samples. All were subjected to tensile stress to breaking point. The mean stress at breaking point in the non-sutured series treated with glutaraldehyde alone was 16.42 and 13.85 MPa depending on the region of the pericardium, while in the sutured samples subjected to glutaraldehyde the mean stress was 7.50 and 7.63 MPa, respectively, differences which were statistically significant (p = 0.03 and p = 0.003, respectively) when the means for non-sutured samples from equivalent regions treated with glutaraldehyde were compared. The stress at breaking point was lower in the SDS-treated series, ranging between 2.60 and 3.56 MPa. The mathematical functions that govern the stress/strain or deformation were obtained. In the series of pericardium treated with SDS, deformations of 10% were produced with stresses of under 0.4 MPa, an outcome that is intolerable from the constructive point of view. We established a regression model that enabled us to determine the mechanical behavior of a sutured sample by testing a contiguous piece of tissue, with a high correlation coefficient (r \gt 0.99). We consider this finding to be of interest in the selection of pericardium for use in the construction of leaflets for cardiac bioprostheses.

This study was designed to establish whether the spatial structure of a prosthesis conditions its behavior at the peritoneal level.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.Adhesions to CV-4 were firm and integrated within surrounding tissue; only scarce adhesion formation was observed for DM. Adhesion area was significantly greater (P0.01) 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 (P0.05) 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; P0.05).The structure of a biomaterial, rather than its chemical composition, modulates behavior at the peritoneal interface.

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 (p0.05) 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 (p0.05) 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 (p0.05) 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.

To compare the behaviour of two composite biomaterials in rabbit peritoneum.Animal study.Faculty of Medicine, University of Alcalá, Spain.14 white New Zealand white rabbits divided into 2 groups of 7 each.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.Infection, healing, development of adhesions, and histological appearance of the interface.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), p0.01). 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), p0.05) while higher biomechanical resistance values were recorded in the Vypro group 30.4 (1.9) compared with 15.0 (2.73), p0.05).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 (p0.05). Comparison of values recorded for groups II and III yielded no significant difference (p0.05). 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, p0.05). 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.

The appearance of new pathologies affecting abdominal organs after implant of a prosthesis to repair an abdominal wall defect may necessitate reintervention. The aim of this study was to compare the behavior of two types of biomaterial widely used in clinical practice, polypropylene (PL) and polytetrafluoroethylene (ePTFE), after a second laparotomy involving the implant. The behavior, in terms of tensile resistance and integration with tissues, of intact prostheses was compared to that of prostheses subjected to opening and repair.A defect (7x5 cm) involving all tissue layers was created in the anterior abdominal wall of 24 male New Zealand rabbits. These defects were repaired with a reticular, macroporous PL mesh (Marlex, Bard Card., Madrid, Spain) or a laminar, micro/macroporous ePTFE prosthesis (Mycro Mesh, W.L. Gore, Flagstaff, AZ) of similar size to the defect. Four study groups were established: Intact PL/Intact ePTFE (n = 6 each): animals implanted with a PL or ePTFE prosthesis and sacrificed 90 days after implant; Repaired PL/Repaired ePTFE (n = 6 each): animals implanted with a PL or ePTFE prosthesis subjected to midlongitudinal relaparotomy through the center of the prosthesis 90 days postimplant, followed by repair with continuous polypropylene 4/0 suture. Animals in repaired groups were sacrificed 90 days after the second intervention. Specimens comprised of prosthesis and neoformed tissue were subjected to light and scanning electron microscopy. In addition, 2 cm-wide strips, consisting of the prosthesis and anchorage tissue, were subjected to biomechanical analysis using an Instron tensiometer (Instron, Canton, MA). The results obtained were statistically compared using the Mann-Whitney U-test.The intact PL implants were fully infiltrated by dense, disorganized, well-vascularized scar tissue with fibers concentric to the mesh monofilaments. The appearance of the repaired PL prostheses was similar, with establishment of neoformed tissue in repaired areas of the prosthesis such that both cut edges of the prosthesis were joined together. In contrast, intact ePTFE prostheses were encapsulated by organized tissue with fibers running parallel to the surface of the biomaterial. Repaired ePTFE prostheses including sutured areas were similarly encapsulated. But the edges of the sutured middle area did not fuse. Tensile resistance values of intact and repaired PL prostheses were similar (intact, mean, 34.78 Newtons; repaired, mean, 34.74N, p0.001). Tensile resistance values of intact ePTFE implants were significantly different to those of the repaired ePTFE prostheses (intact, mean, 22.64N; repaired, mean, 17.21N, p0.001). Breakage of both types of PL specimen strips was restricted to recipient tissue while breakage of intact ePTFE specimens occurred in the areas of anchorage to the abdominal wall. Rupture of repaired ePTFE specimens took place in the sutured central areas of the prostheses.We conclude that relaparotomy through an existing PL prosthesis previously integrated with the abdominal wall does not affect the tissue integration process or the tensile resistance of the implant. When the relaparotomy involves an ePTFE prosthesis, however, although the repair process itself is unaffected, significant loss in tensile strength is incurred. In addition, relaparotomy through both types of biomaterial is likely to result in the neoformation of adhesions in the areas of the prosthesis subjected to opening and repair but, in general, the number of adhesions formed in the presence of intact or repaired polypropylene implants was larger than that observed with the use of ePTFE.

Currently one of the most widely used prosthetic materials in the repair of abdominal wall defects, is expanded polytetrafluoroethylene (ePTFE). It has been suggested that its behavior with respect to the reparative process may depend on its structure. The aim of the present study was to evaluate the effect of the structure of 3 ePTFE prostheses on the scarring process in an abdominal-wall-defect experimental model. The prostheses employed were the Soft Tissue Patch (STP) which is laminar in structure, Mycro Mesh (MM) which is multilaminar with perforations, and the Dual Mesh (DM) prosthesis which has one non-porous surface. Abdominal wall defects (7 x 5 cm) were created in 36 New Zealand rabbits and repaired using fragments of STP, MM and DM. Follow-up periods were 14, 30, 60 and 90 days post-implant. At these times prostheses were macroscopically examined for the presence of infection and/or rejection and the formation of adhesions to abdominal viscera. Specimens were also taken for microscopic analysis (optical and scanning electron) and for immunohistochemical analysis using the rabbit macrophage-specific monoclonal antibody RAM-11. Labelled macrophage counts were performed at each follow-up session. No cases of infection or rejection were found. Loose adhesions between prosthesis and underlying viscera were observed in 2 of the STP, 4 of the MM and 2 of the DM implants. STP and DM implants were progressively encapsulated by organized connective tissue on both peritoneal and subcutaneous surfaces. Cellular colonization was observed on both STP surfaces and on the porous surface of the DM although no more than a third of the biomaterial was penetrated by cells in either case. Colonization was very slight at prosthesis anchorage points. MM implants differed only in the formation of connective tissue bridges in perforated areas, and cellular infiltration in interlaminar spaces. Macrophage response was similar in the 3 prostheses with a reduction in RAM-11 labelled cells (p0.05) between 14 and 90 days post-implant. We conclude: a) the 3 types of PTFE prosthesis induced low incidence of adhesion formation between biomaterial and viscera; b) integration mechanism of the 3 prostheses were similar and culminated with the encapsulation of the PTFE by the neoformed tissue; c) the macrophage response induced by the 3 prostheses was similar to that of any reparative process in the absence of biomaterial.

Currently one of the most widely used prosthetic materials in the repair of abdominal wall defects, is expanded polytetrafluoroethylene (ePTFE). It has been suggested that its behavior with respect to the reparative process may depend on its structure. The aim of the present study was to evaluate the effect of the structure of 3 ePTFE prostheses on the scarring process in an abdominal-wall-defect experimental model. The prostheses employed were the Soft Tissue Patch (STP) which is laminar in structure, Mycro Mesh (MM) which is multilaminar with perforations, and the Dual Mesh (DM) prosthesis which has one non-porous surface. Abdominal wall defects (7x5cm) were created in 36 New Zealand rabbits and repaired using fragments of STP, MM and DM. Follow-up periods were 14, 30, 60 and 90 days post-implant. At these times prostheses were macroscopically examined for the presence of infection andlor rejection and the formation of adhesians to abdominal viscera. Specimens were also taken for microscopic analysis (optical and scanning electron) and for immunohistochemical analysis using the rabbit macrophage-specific monoclonal antibody RAM-11. Labelled macrophage counts were performed at each follow-up session. No cases of infection or rejection were found. Loose adhesions between prosthesis and underlying viscera were observed in 2 of the STP, 4 of the MM and 2 of the DM implants. STP and DM implants were progressively encapsulated by organized connective tissue on both peritoneal and subcutaneous surfaces. Cellular colonization was observed on both STP surfaces and on the porous surface of the DM although no more than a third of the biomaterial was penetrated by cells in either case. Colonization was very slight at prosthesis anchorage points. MM implants differed only in the formation of connective tissue bridges in perforated areas, and cellular infiltration in interlaminar spaces. Macrophage response was similar in Offprint requests 10: Prof. J. Buján, Department of Morphological Sciences and Surgery, Faculty of Medicine, University of Alcalá de Henares, Crta. Madrid-Barcelona, km 33.600, 28871 -Alcalá de Henares, Madrid, Spain the 3 prostheses with a reduction in RAM-11 labelled cells (p

Two types of prosthetic material used for repairing hernial defects of the abdominal wall were compared: Mycro Mesh and Marlex. Mycro Mesh (MM) is a new polytetrafluoroethylene product of layered, microporous structure. Macroscopically, it presents regularly distributed, 2-mm orifices that perforate the biomaterial. Marlex (PL) is a well-known polypropylene mesh product with a macroporous structure.In 24 white New Zealand rabbits, a full-thickness (except skin) 5 x 7-cm defect was created in the anterior wall of the abdomen. Defects were repaired with either MM (n = 12) or PL (n = 12) implants and studied at 14, 30, 60, and 90 days after implantation. Samples of the interfaces between prosthesis and subcutaneous tissue, visceral peritoneum, and receptor tissue, respectively, were studied. Samples were processed for optical microscopy and scanning electron microscopy (SEM). An immunohistochemical study was made using RAM-11, a monoclonal antibody specific for rabbit macrophages. The tensile strength of the repairs was made using an Instron tensiometer on 2-cm wide transversal strips that included the prosthesis and its anchor zones to the receptor tissue.The formation of adhesions between the prosthesis and intestine was important with the PL implants but not with the MM implants. Optical microscopy and SEM showed formation of an organized connective tissue surrounding the MM implants. At 90 days, compact bridges of connective tissue linked the tissue on the subcutaneous and peritoneal sides of the prosthesis. The PL implants became integrated into a disorganized, highly vascularized connective tissue. The intensity of the macrophage response was similar in both prostheses and decreased between days 14 and 90 (Student-Newman-Keuls test p = 0.01). The tensile strength of the PL implants was greater than that of the MM implants. At 90 days, the tensile strength of the PL implants was mean equals 33.11 N and of the MM implants, mean equals 22.65 N (Mann-Whitney test p0.001).The tissue integration of the PL and MM implants differed; fewer visceral adhesions formed on MM than on PL; the macrophage reaction was not determinant of the success of failure of either biomaterial; and the tensile strength of the prosthesis-receptor tissue interface was much greater in the PL implants than in the MM implants.