Functional and Morphologic Properties of a Modified Mesh for Inguinal Hernia Repair

Inguinal hernia repair is one of the most frequently performed operations. Next to conventional techniques, open and laparoscopic tension-free methods using mesh implants to reinforce the abdominal wall are increasingly carried out, even becoming the standard procedure in many countries. Because of the benefits of material-reduced meshes for incisional hernia repair, a new mesh modification for tension-free inguinal hernia repair has been developed. In the present study this new low-weight mesh (Vypro II) made of polypropylene and polyglactin multifilaments was compared to a common heavy-weight polypropylene mesh (Prolene) regarding their functional consequences and the morphologic tissue response. After implantation in rats as an inlay, abdominal wall mobility was recorded by three-dimensional photogrammetry and the tensile strength of the suture zone and the mesh itself was measured at 3, 21, and 90 days. Explanted tissue samples have been investigated for their histologic reaction in regard to the inflammatory infiltrate, vascularization, and connective and fat tissue ingrowth. Numbers of granulocytes, macrophages, fibroblasts, lymphocytes, and foreign giant body cells have been evaluated to reflect the quality of the tissue response. The cellular response was assessed by measuring DNA strand breaks and apoptosis (TUNEL), proliferation (Ki67), and cell stress (HSP70). The results indicated that restriction of abdominal wall mobility was significantly reduced with Vypro II compared to that seen with heavy-weight mesh modification, and the inflammatory reaction and connective tissue formation were markedly diminished. Apoptosis and cell proliferation showed considerably lowered levels, and expression of cytoprotective HSP70 was significantly increased. The present study thus confirms the benefits of material-reduced mesh modifications. The new low-weight mesh (Vypro II) could be advantageous in inguinal hernia repair.     

Functional and morphologic properties of a modified mesh for inguinal hernia repair

Inguinal hernia repair is one of the most frequently performed operations. Next to conventional techniques, open and laparoscopic tension-free methods using mesh implants to reinforce the abdominal wall are increasingly carried out, even becoming the standard procedure in many countries. Because of the benefits of material-reduced meshes for incisional hernia repair, a new mesh modification for tension-free inguinal hernia repair has been developed. In the present study this new low-weight mesh (Vypro II) made of polypropylene and polyglactin multifilaments was compared to a common heavy-weight polypropylene mesh (Prolene) regarding their functional consequences and the morphologic tissue response. After implantation in rats as an inlay, abdominal wall mobility was recorded by three-dimensional photogrammetry and the tensile strength of the suture zone and the mesh itself was measured at 3, 21, and 90 days. Explanted tissue samples have been investigated for their histologic reaction in regard to the inflammatory infiltrate, vascularization, and connective and fat tissue ingrowth. Numbers of granulocytes, macrophages, fibroblasts, lymphocytes, and foreign giant body cells have been evaluated to reflect the quality of the tissue response. The cellular response was assessed by measuring DNA strand breaks and apoptosis (TUNEL), proliferation (Ki67), and cell stress (HSP70). The results indicated that restriction of abdominal wall mobility was significantly reduced with Vypro II compared to that seen with heavy-weight mesh modification, and the inflammatory reaction and connective tissue formation were markedly diminished. Apoptosis and cell proliferation showed considerably lowered levels, and expression of cytoprotective HSP70 was significantly increased. The present study thus confirms the benefits of material-reduced mesh modifications. The new low-weight mesh (Vypro II) could be advantageous in inguinal hernia repair.     

Influence of polyglecaprone 25 (Monocryl) supplementation on the biocompatibility of a polypropylene mesh for hernia repair

Background: Supplementary polyglecaprone 25 (Monocryl) monofilaments were added to a lightweight pure monofilament polypropylene mesh (PP mesh) to improve intraoperative handling (PP+M mesh). This study was designed to evaluate the influence of this additional supplementation on the biocompatibility in a rodent animal model. Methods: Two mesh materials, a composite mesh (PP+M) and the pure polypropylene variant (PP), were compared after subcutaneous implantation in a standardized rat model. Histological analysis of the inflammatory response was performed after 28, 56 and 84 days of implantation. Material absorption, inflammatory tissue reaction, fibrosis and granuloma formation were investigated, as well as the percentage of proliferating and apoptotic cells at the interface. Results: Both mesh materials showed a slight foreign body reaction involving mainly macrophages and foreign body giant cells. Total absorption of the Monocryl filaments of the PP+M mesh occurred between 56 and 84 days of implantation. Both the inflammatory and the fibrotic reaction were decreased (n.s.) in the PP+M mesh group compared to the pure PP mesh. Whereas the percentage of proliferating cells showed no significant difference, the rate of apoptotic cells was significantly decreased in the PP+M mesh group over the whole implantation period. Conclusion: Compared to the pure polypropylene mesh, our data confirm that the use of a polypropylene mesh supplemented with absorbable Monocryl filaments is feasible without additional short-term mesh-related complications in the experimental model or negative side effects on biocompatibility.     

Mesh implants in hernia repair. Inflammatory cell response in a rat model

BACKGROUND: In the reinforcement of the abdominal wall with mesh implants, various complications including hernia recurrence, abdominal pain, seroma formation and infection are discussed to depend on the biocompatibility of the alloplastic prosthesis. Particularly macrophages, T-cells and mast cells have been shown to play a major role in the inflammatory response to biomaterials. To approach biocompatibility of surgical meshes we therefore examined the infiltrate of these cells as well as the proliferation rate in response to different clinically applied materials. MATERIALS AND METHODS: Three mesh materials (polypropylene: PP, Prolene; polyethylene terephthalate: PET, Mersilene, and polypropylene/polyglactin: PP + PG, Vypro) were compared after inlay implantation in a standardized rodent animal model. A suture-closed laparotomy served as control. After 7 and 90 days of implantation, histochemical analysis of the inflammatory response to all biomaterials was performed: macrophages (ED3), T-cells (CD3), proliferating cells (PCNA) and mast cells (Giemsa) were investigated. RESULTS: In all groups a persisting T-cell response was observed. Colonization of the interface with macrophages showed a pronounced reduction in the PP + PG-mesh group. Infiltration of mast cells at the tissue graft interface showed a time-dependent decrease in the PET- and PP + PG-mesh groups, whereas in contrast, index of mast cells increased in the PP-mesh group. At both time points, indices of proliferation were highest in the PP-mesh group. CONCLUSION: The present data confirm the development of a biomaterial-dependent chronic inflammatory response to surgical meshes with macrophages as the predominant cell type. Further research on the recruitment of inflammatory cells and in particular on the role of mast cells and their granular products should be encouraged.     

Impact of polymer pore size on the interface scar formation in a rat model

BACKGROUND: The surgical therapy of hernias is increasingly based on reinforcement with alloplastic material, in particular surgical meshes. The biological response to these foreign bodies largely depends on the selected material and its structure. In comparison to the physiological scar process following a simple abdominal wall incision, the chronic inflammation at the interface to the polymers lead to specific morphological alterations. MATERIALS AND METHODS: In the present study two meshes with different pore sizes were implanted into rats: a heavy-weight and small-pore-sized mesh (hw-mesh) made of nonabsorbable polypropylene monofilaments and a low-weight large-pore-sized mesh consisting of polypropylene and of absorbable polyglactin multifilaments (lw-mesh). A suture repair of a laparotomy served as control. After 7, 14, 21, and 90 days the mesh area was analyzed with regard to tissue and cellular response. RESULTS: Over the whole observation period morphometric analysis indicated an improved integration of the lw-mesh with reduction of both inflammation and fibrosis, whereas the hw-mesh induced an intense chronic inflammation concomitant with an intensified bridging scar reaction. On the cellular level these findings correspond to an elevated cell turnover, characterized by increased rates of apoptotic and proliferating cells. In contrast, the tissue reaction to the lw-mesh achieved levels almost similar to those of the physiological scaring process in the control group. CONCLUSION: In conclusion, the present data confirm the development of a chronic inflammatory foreign body reaction at the interface to both hw-meshes and lw-meshes; however, the use of lw-meshes showed superior tissue integration. With regard to the quite similar polymer surface the pore size appears to be of major importance in tissue reaction and for the biocompatibility of mesh structures.     

In-vitro study of the cellular response of human fibroblasts cultured on alloplastic hernia meshes. Influence of mesh material and structure]

BACKGROUND: The biocompatibility of meshes in hernia surgery seems to be influenced markedly by the amount of the selected material and its structure. Fibroblasts play a major key role during the process of mesh incorporation. This study was performed to investigate differences in cell morphology and proliferation of human fibroblasts cultured on different polypropylene meshes. METHODS: In the present in vitro study the cellular response of human fibroblasts was investigated by scanning electron microscopy (SEM), comparing three different polypropylene meshes: a newly constructed low-weight and microporous mesh (NK1), a low-weight and macroporous mesh with absorbable polyglactin filaments (Vypro), and a heavy-weight and microporous mesh (BiomeshP1). Human fibroblasts (1,5.10(5) cells) were incubated with the meshes (each 12 mm(2)) for 6 hours, 5 days, 2, 4, 6, and 12 weeks. Computer-assisted morphometry of the fibroblast/mesh surface ratio served to reflect the biological cell response. RESULTS: The Vypro mesh showed the significantly highest fibroblast density during the first 6 weeks, but cell growth was nearly exclusively limited to the polyglactin filaments. At 3 months, after reabsorption of the polyglactin, the fibroblast-coated polypropylene mesh surface was only 50% compared to NK1 and BiomeshP1. The morphologic aspect of the fibroblasts on the BiomeshP1 mesh was much more degenerative and unphysiological, compared to NK1 and Vypro, with isolated, single cells instead of a broad, connective growth. The BiomeshP1 showed a significantly higher fibroblast proliferation around the nodes of the mesh compared to the straight filaments. On the NK1 mesh fibroblasts exclusively proliferated on the filaments but not on the pressed mesh surface. CONCLUSIONS: The polymer surface and structure appears to be of major importance for the biocompatibility of meshes: human fibroblasts preferably grow on low-weight meshes, thin filaments, and mesh nodes. Heavy-weight meshes induce degenerative cell reactions. Polyglactin seems to further improve cell proliferation whereas a pressed mesh surface without pores hinders fibroblast growth.     

Titanium coating of a polypropylene mesh for hernia repair: Effect on biocompatibilty

Titanium and its alloys are used worldwide in surgery. The favorable characteristics that make this material desirable for implantation are corrosion resistance and biocompatibility. Concerning hernia repair, a mesh modification has been developed using titanium layering of a polypropylene mesh implant, which is said to lead to an improved biocompatibility compared to commercially available mesh materials. To analyze the pure effect of titanium coating, two different mesh structures were studied using a standardized animal model. The titanium-coated monofilamentous, large porous, and lightweight mesh made of polypropylene and coated with titanium (PP+T) was compared to a pure polypropylene mesh manufactured with a similar structure and amount of material serving as a control (PP). In Sprague-Dawley rats, mesh samples were placed in a subcutaneuous position. Then 56, 84, and 182 days after mesh implantation, three animals from each group were sacrificed for morphological observations (amount of inflammatory and connective tissue formation, percentages of proliferating and apoptotic cells, percentage of macrophages). Both mesh modifications investigated showed an overall good biocompatibility. Macroscopic clinical observation after implantation of up to 182 days was uneventful. The tissue response to the PP as well as to the PP+T mesh was characterized by a moderate inflammatory tissue reaction limited to the perifilamentary region as is known for low weight, large porous, and monofilamentous mesh structures. No significant improvement of biocompatibility was found when analyzing the effect of titanium coating compared to the pure polypropylene mesh structure.     

In vivo studies comparing the biocompatibility of various polypropylene meshes and their handling properties during endoscopic total extraperitoneal (TEP) patchplasty: an experimental study in pigs

Background: Polypropylene (PP) meshes are currently being used in millions of operations for hernial repair. We tested several recently modified PP meshes to evaluate them in terms of their biocompatibility and handling characteristics during minimally invasive procedures. Methods: Four different PP meshes (a heavyweight PP, Atrium; a lightweight PP incorporating absorbable polyglactic acid, Vypro II; a lightweight PP, Parietene; and a titanium-coated lightweight PP, Ti-Mesh Extralight), all implanted using the endoscopic total extrapreperitoneal (TEP) technique, were investigated in groups comprising 11 pigs each. After 94 ± 5 days, the animals were autopsied and tissue samples were studied histologically, immunohistochemically, and electron-microscopically. Results: Whereas endoscopic handling of the Vypro II mesh proved difficult, the already good properties of the Atrium mesh were significantly improved on by Parietene and the Ti-Mesh. Clear differences were also found in the shrinkage characteristics of the implant materials. In comparison with Atrium (12%), Vypro II mesh shrinkage was significantly greater (28%), whereas Parietene (7%) and Ti-Mesh (5%) incurred less shrinkage. With regard to the chronic inflammatory reaction, the titanium-coated mesh showed a significantly lower inflammatory activity (13.1% partial volume [%PV] vs 34.1%PV and 29.0%PV) than the lightweight meshes Vypro II and Parietene, but—with the exception of the monocytic (0.2 vs 9.1, 5.1, and 7.9) and B-lymphocytic reaction (1.1 vs 18.0, 11.7, and 12.2)—no significant difference was seen in comparison with Atrium. The various mediators in the extracellular matrix (matrix metalloproteinases 1 [MMP-1 transforming growth factor beta [TGF-], urokinase plasminogen activator [uPA], and type I collagen) tended to show the highest expression with Vypro II (13.6, 113.2, 132.7, and 139.5, respectively) and the lowest expression with Ti-Mesh (11.9, 68.5, 92.8, and 75.0, respectively). With regard to cell proliferation, Parietene and Ti-Mesh appeared to have slight advantages, but no differences were observed in the apoptotic rate. Conclusion: In our opinion, despite a reduction in material, Vipro II, on account of the inflammatory reaction, does not represent a true improvement over the meshes currently used for hernia repair. In comparison, the two lightweight PP patches are characterized by a more favorable foreign body reaction, with the titanium coating of the Ti-Mesh providing an additional advantage in terms of its biocompatibility.     

Persistent extracellular matrix remodelling at the interface to polymers used for hernia repair

On the one hand, recurrence rates and postoperative complications following hernia repair are supposed to be influenced by the kind of mesh material used. On the other hand, an impaired collagen metabolism and cleavage within connective tissue has been suggested as decisive factor in the pathogenesis of recurrent hernia formation. The aim of our study was, therefore, to analyze the impact of commonly used mesh materials on quality of collagen deposition, expression of collagenases (matrix metalloproteinases; MMP-1/MMP-13), and specific tissue inhibitors of MMPs (TIMPs) in an animal study. Four different mesh materials were used (Prolene = polypropylene, Mersilene = polyester, and Vypro and Vypro II = combinations of polypropylene and polyglactin) and implanted as abdominal wall replacement in 60 male Wistar rats. Mesh samples were explanted after 3, 21, and 90 days and investigated using immunohistochemistry (expression of MMP-1/MMP-13 and TIMP-1) and cross-polarization microscopy (percentage of collagen type III to overall collagen). Besides an insufficient collagen composition with an increased percentage of collagen type III, we found a complex expression of collagenases and their inhibitors combined with a persistent chronic foreign-body reaction even 90 days after implantation. Except for TIMP-1 expression, which was significantly related to a lowered amount of inflammatory (r = -0.980, p = 0.02) and connective tissue formation (r = -0.951, p = 0.049), there was no relation to the expression of collagenases (MMP-1/MMP-13) with regard to the amount of inflammatory and connective tissue formation despite partly significant differences between implanted polymers.     

Hernienchirurgie: Wachstumsverhalten humaner Fibroblasten auf alloplastischen Kunststoffnetzen

Background

The biocompatibility of meshes in hernia surgery seems to be influenced markedly by the amount of the selected material and its structure. Fibroblasts play a major key role during the process of mesh incorporation. This study was performed to investigate differences in cell morphology and proliferation of human fibroblasts cultured on different polypropylene meshes.

Methods

In the present in vitro study the cellular response of human fibroblasts was investigated by scanning electron microscopy (SEM), comparing three different polypropylene meshes: a newly constructed low-weight and microporous mesh (NK1), a low-weight and macroporous mesh with absorbable polyglactin filaments (Vypro), and a heavy-weight and microporous mesh (BiomeshP1). Human fibroblasts (1,5·10⁵ cells) were incubated with the meshes (each 12 mm²) for 6 hours, 5 days, 2, 4, 6, and 12 weeks. Computer-assisted morphometry of the fibroblast/mesh surface ratio served to reflect the biological cell response.

Results

The Vypro mesh showed the significantly highest fibroblast density during the first 6 weeks, but cell growth was nearly exclusively limited to the polyglactin filaments. At 3 months, after reabsorption of the polyglactin, the fibroblast-coated polypropylene mesh surface was only 50% compared to NK1 and BiomeshP1. The morphologic aspect of the fibroblasts on the BiomeshP1 mesh was much more degenerative and unphysiological, compared to NK1 and Vypro, with isolated, single cells instead of a broad, connective growth. The BiomeshP1 showed a significantly higher fibroblast proliferation around the nodes of the mesh compared to the straight filaments. On the NK1 mesh fibroblasts exclusively proliferated on the filaments but not on the pressed mesh surface.

Conclusions

The polymer surface and structure appears to be of major importance for the biocompatibility of meshes: human fibroblasts preferably grow on low-weight meshes, thin filaments, and mesh nodes. Heavy-weight meshes induce degenerative cell reactions. Polyglactin seems to further improve cell proliferation whereas a pressed mesh surface without pores hinders fibroblast growth.     

Comparison of adhesive properties of five different prosthetic materials used in hernioplasty.

This experimental study was designed to assess and to compare intra-abdominal adhesions following the use of five commercially available prosthetic mesh grafts in the repair if abdominal wall defects. Sixty Wistar albino rats were randomly divided into six groups (n = 10). A 2 x 1 cm defect at abdominal wall was created and defects were closed either primarily or with one of the following prosthetic mesh grafts: monofilament polypropylene, polytetrafluoroethylene, sodium hyaluronate/carboxymethylcellulose-coated polypropylene, polypropylene/polyglactin 910 composite, or resorbable hydrophilic collagen-coated multifiber polyester. The severity of adhesions was graded, tensile strengths of adhesions were measured, and histopathological grades of inflammation and fibrosis were evaluated. Polypropylene mesh resulted in more adhesion formation in comparison to primary repair and other grafts used in this study, except polypropylene/polyglactin 910 composite mesh. In addition, the highest tensile strength of omental adhesions was detected in the polypropylene group (chi2 = 26.249; p = .0001). Polyester composite mesh caused the least adhesion formation among the groups. Sodium hyaluronate/carboxymethylcellulose-coated polypropylene and polyester composite meshes revealed the highest fibrosis scores (chi2 = 50.776; p = .0001). The highest inflammatory activity was detected in the polytetrafluoroethylene mesh group (chi2 = 16.564; p = .005). Thus, sodium hyaluronate/carboxymethylcellulose-coated polypropylene and polytetrafluoroethylene meshes following polyester composite mesh were the minimal adhesion-forming grafts in this study. Disadvantages of the polytetrafluoroethylene mesh were lower fibrotic activity and higher inflammatory reaction to the graft.     

Early and late postoperative inflammatory and collagen deposition responses in three different meshes: an experimental study in rats

Purpose

Although meshes reduce abdominal hernia recurrence, they increase the risk of inflammatory complications. This study aimed to compare the early and late postoperative inflammation and collagen deposition responses induced by three meshes.

Methods

Rats were allocated into three groups. In group I, a polypropylene (PP) mesh was implanted in the abdominal wall. In groups II and III, PP + polyglactin (PP + PG) and PP + titanium (PP + TI) meshes were employed, respectively. On the seventh (7th) postoperative day, collagen deposition and inflammation were evaluated, and immunohistochemistry was performed on abdominal wall biopsies. These data were compared with those obtained on the fortieth (40th) postoperative day in a previous study.

Results

The early inflammatory responses were the same in all groups. With time, it decreased in group I (p = 0.047) and increased in group II (p = 0.003). Group I exhibited early elevated VEGF (p < 0.001), COX2 (p < 0.001), and collagen (p = 0.023) levels, and group II exhibited the most severe inflammatory tissue response. On the 40th postoperative day, the VEGF (p < 0.001) and collagen (p < 0.005) were reduced as compared with the 7th postoperative day in all groups.

Conclusions

Belatedly, the inflammatory reaction decreased in PP mesh group and increased in PP + PG mesh group. The PP mesh induced early great elevations in VEGF, COX2 and collagen levels, whereas the PP + PG mesh caused severe tissue inflammation with small elevation in these levels. PP + TI mesh induced inflammatory response levels between the others. In conclusion, the inflammatory response depends on the mesh density and also the mesh material with clinical implications.     

Partially absorbable meshes for hernia repair offer advantages over nonabsorbable meshes

BACKGROUND: The aim of this study was to establish whether new prosthetic materials with absorbable components, designed to reduce the amount of foreign material in abdominal wall repair, offer advantages over the conventional polypropylene meshes. METHODS: Seven x 5 cm defects created in the anterior abdominal wall of New Zealand white rabbits were repaired by using a nonabsorbable polypropylene prosthesis (Surgipro; Tyco, Barcelona, Spain) or 1 of 2 partially absorbable prostheses available on the market (Vypro II and Ultrapro; Johnson & Johnson, St. Stevens-Woluwe, Belgium). At 14 and 90 days after surgery, tissue/prosthesis specimens were subjected to histological studies, biomechanical strength tests, and shrinkage evaluation. RESULTS: At 90 days, the absorbable filaments of Vypro II had been completely reabsorbed, whereas Ultrapro only showed signs of biodegradation in a few zones. Host tissue infiltration and collagen I deposition in the 3 reticular meshes was optimal. Macrophage counts, mesh shrinkage, and biomechanical resistance values were similar. CONCLUSIONS: Partially absorbable prostheses perform as well as the standard polypropylene mesh and have the benefit that less foreign material remains in the recipient, without compromising mechanical resistance.     

四种聚丙烯网用于矫正乳房下垂的生物相容性研究

目的探讨外科网片的皱缩和粘连影响其作为内置式乳罩纠正轻、中度乳房下垂的术后效果，通过比较4种不同的聚丙烯网在生物相容性上的差异，找出异物反应与术后效果的关系，以便为内置式乳罩选用聚丙烯网片提供依据。方法以实验用小型诸作为动物模型，将4种不同的聚丙烯网置入腹部皮下，90d后采集标本，比较并发症、肄物反应、胶原纤维与弹力纤维的形成，并在透射电子最微镜下观察超微结构。结果4种聚丙烯网在生物相容性上存存差异。异物反应的程度决定生物相容性的差异，同时对术后乳房形态有显著的影响。结论Premilene Mesh LP作为新型的轻质量网片，生物相容性优于其他网片。     

Intraabdominal adhesion formation of polypropylene mesh Influence of coverage of omentum and polyglactin

Background Adhesions after intraabdominal surgical procedures are related to high morbidity and mortality. Biomaterials, particularly those made of polypropylene, in the intraabdominal position have to be considered as pathophysiological cofactor in a multifactorial process of adhesion formation. To investigate the adhesive potential induced by the biomaterial, an animal model was performed. In addition, the influence of coverage by omentum or a polyglactin barrier was investigated.Methods In, 18 Chinchilla rabbits the biomaterial was placed laparoscopically using the intraperitoneal onlay mesh technique. Using this model, a polypropylene–polyglactin mesh compound (PPMC) was used with three different implantation techniques: group 1, PPMC implantation without coverage (PPMC): group 2, PPMC implantation with additional omentum coverage (PPMC-O): and group 3, PPMC implantation with coverage of an absorbable polyglactin mesh (PPMC-V). The degree of adhesion formation was measured 90 days after implantation by computer-assisted planimetry. Morphometric examination followed the explantation analyzing the amount of foreign body response.Results We found a significant reduction of adhesion formation for the PPMC and PPMC-O groups compared to the PPMC-V group, in which dense adhesions were found. Morphometric investigations of the perifilamental granulomas of the pure (PPMC) group revealed a typical foreign body reaction with a mild to moderate fibrosis around all mesh fibers. However, tissue specimens of the PPMC-O and PPMC-V groups indicated a similar inflammatory reaction but significantly increased connective tissue formation around the polymer fibers compared to the pure PPMC group.Conclusion The intraabdominal placement of a pure PPMC shows a neoperitonealization and perifilamental collagenous ingrowth with almost no adhesions. Coverage with omentum (PPMC-O) or polyglactin mesh (PPMC-V) resulted in a significant increase in inflammation and perifilamentary connective tissue formation.     

Comparison of Adhesive Properties of Five Different Prosthetic Materials Used in Hernioplasty

This experimental study was designed to assess and to compare intra-abdominal adhesions following the use of five commercially available prosthetic mesh grafts in the repair if abdominal wall defects. Sixty Wistar albino rats were randomly divided into six groups (n = 10). A 2 × 1 cm defect at abdominal wall was created and defects were closed either primarily or with one of the following prosthetic mesh grafts: monofilament polypropylene, polytetrafluoroethylene, sodium hyaluronate/carboxymethylcellulose-coated polypropylene, polypropylene/polyglactin 910 composite, or resorbable hydrophilic collagen-coated multifiber polyester. The severity of adhesions was graded, tensile strengths of adhesions were measured, and histopathological grades of inflammation and fibrosis were evaluated. Polypropylene mesh resulted in more adhesion formation in comparison to primary repair and other grafts used in this study, except polypropylene/polyglactin 910 composite mesh. In addition, the highest tensile strength of omental adhesions was detected in the polypropylene group (χ² = 26.249; p =. 0001). Polyester composite mesh caused the least adhesion formation among the groups. Sodium hyaluronate/carboxymethylcellulose-coated polypropylene and polyester composite meshes revealed the highest fibrosis scores (χ² = 50.776; p =. 0001). The highest inflammatory activity was detected in the polytetrafluoroethylene mesh group (χ² = 16.564; p =. 005). Thus, sodium hyaluronate/carboxymethylcellulose-coated polypropylene and polytetrafluoroethylene meshes following polyester composite mesh were the minimal adhesion-forming grafts in this study. Disadvantages of the polytetrafluoroethylene mesh were lower fibrotic activity and higher inflammatory reaction to the graft.     

Laparoscopic evaluation of abdominal adhesions with different prosthetic meshes in rabbits.

BACKGROUND: The use of prosthetic materials to reinforce the abdominal wall is associated with a low index of recurrence; however, intraperitoneal placement of a foreign body may lead to adhesions. The present investigation was designed to determine adhesion formation with commercially available meshes implanted laparoscopically in rabbits. METHODS: Three different meshes were implanted laparoscopically in 24 rabbits: polypropylene (mesh A), polypropylene and sodium hyaluronate-carboxymethylcellulose (mesh B), and polypropylene and expanded polytetrafluoroethylene (mesh C). Sites of implantation for each mesh (the left lower quadrant, right lower quadrant, and lower midline) were randomly determined so that every rabbit had all 3 meshes implanted. All animals underwent diagnostic laparoscopy after 28 days to grade adhesions and histological analysis of inflammation. RESULTS: Adhesions were noticed in 46 of the 72 meshes implanted (64%). The number of adhesions was higher for mesh C (87.5%) compared with meshes A (62.5%) and B (41.6%). The severity of adhesions was also higher for mesh C (grade I in 14, II in 6, and III in 1) compared with mesh A (grade I in 10, II in 4, and III in 1 case) and B (all of them grade II). Histological inflammatory reaction was classified as mild in 23 cases of mesh A, 15 of mesh B, and 23 of mesh C. A moderate reaction was found in 1 case of mesh A, 4 cases of mesh B, and 1 case of mesh C. Severe reaction was induced in 5 cases of mesh B. Mesh B induced a higher inflammatory reaction compared with the other meshes. CONCLUSIONS: All meshes induced adhesions of different grades. Mesh B had fewer adhesions and more intense inflammation them did the others.     

A single-surgeon randomized trial comparing three composite meshes on chronic pain after Lichtenstein hernia repair in local anesthesia

Background Chronic pain may be a long-term problem related to operative trauma and mesh material in Lichtenstein hernioplasty. Study design Inguinal hernioplasty was performed under local anesthesia in 228 patients (232 hernias) in day-case surgery by the same surgeon and exactly by the same surgical technique. The patients were randomized to receive either a partly absorbable polypropylene–polyglactin mesh (Vypro II^R 50 g/m², 79 hernias), a lightweight polypropylene mesh (Premilene Mesh LP^R 55 g/m², 75 hernias) or a conventional densely woven polypropylene mesh (Premilene^R 82 g/m², 78 hernias). Pain, patients discomfort and recurrences of hernias were carefully followed at days 1, 7, 1 month, 1 and 2 years after surgery. Results The duration of operation (29–33 min) and the amount of local anesthetic (55–57 ml) were similar in the three groups. Two wound infections and four hematomas were detected with no difference between the meshes. Immediate pain reaction up to 1 month was statistically equal among the three meshes. After 2 years of follow-up, there were five recurrences (two in the Vypro group, one in the Premilene LP and two in the Premilene). A feeling of a foreign body, sensation of pain and patient’s discomfort were similar with all meshes. Conclusion There was no difference of pain and quality of life among a conventional polypropylene mesh, lightweight mesh or partly absorbable mesh in 2 years of follow-up, when the same surgeon operated on all patients with exactly the same technique.     

Comparison of nerve regeneration through different types of neural prostheses

Rat sciatic nerve regeneration through three synthetic neural prostheses was compared with regeneration through nerve allografts. The synthetic prostheses were either nonpermeable nonabsorbable (Silastic), permeable absorbable (polyglactin mesh), or permeable nonabsorbable (polypropylene mesh). Animals were evaluated at 10, 24, and 90 days. Functional analysis of nerve regeneration was performed by noninvasive methods: electromyography and walking tracks. Nerve tissue was examined with routine histologic and immunofluorescent techniques. A compressive neuropathy developed with the use of the Silastic implant. A neutrophilic inflammatory infiltrate was consistently associated with implantation of the polyglactin mesh. A strong connective tissue response was noted around the polypropylene mesh. Early recovery of nerve function was seen with the Silastic implants, however, overall nerve function was best in the nerve allograft and polypropylene mesh groups. Polyglactin implantation increases the local inflammatory response and should not be used for nerve anastomoses. If Silastic entubulation is used, it should be removed between 24 and 90 days.     

Adhesion formation of a polyvinylidenfluoride/polypropylene mesh for intra-abdominal placement in a rodent animal model

Background  Effective laparoscopic ventral herniorrhaphy mandates the use of an intraperitoneal mesh. Visceral adhesions and shrinkage of prosthetics may complicate repairs. The aim of this study was to compare adhesion formation, mesh shrinkage and tissue ingrowth after intra-abdominal placement of a novel two-component monofilament mesh structure made of polypropylene (PP) and polyvinylidenfluoride (PVDF) with current alternatives. Materials and methods  Forty Sprague-Dawley rats were used in this study. Mesh samples were fixed as intra-abdominal only mesh at the right lateral abdominal wall. The study groups were: PVDF+PP (polypropylene parietally and polyvinylidenfluoride viscerally), PP+Col (polypropylene with a collagenoxidized film), ePTFE (smooth surface viscerally and a textured surface parietally), and PP (a pure polypropylene mesh serving as control). The meshes were explanted after 30 days. Adhesions were scored as a percentage of explanted biomaterials’ affected surface area; prosthetic shrinkage was calculated. Foreign-body reaction to mesh materials was measured by investigating the amount of inflammatory infiltrate and fibrotic tissue formation. Results  In terms of adhesion score, the pure PP mesh showed the highest values followed by the ePTFE, PVDF+PP, and PP+Col meshes. Quantitative assessment of adhesion area revealed a significantly higher value of the pure PP mesh sample (62.0 ± 22.1%) compared with the PP+Col (26.8 ± 12.1%) and the PVDF+PP mesh (34.6 ± 8.2%). Percentage of shrinkage showed a significantly higher value of the ePTFE mesh (52.4 ± 13.9%) compared with all other mesh modifications (PP+Col 19.8 ± 13.9%, PVDF+PP 19.9 ± 7.0%, and PP 26.8 ± 9.5%). Inflammatory infiltrate was significantly reduced in the PVDF+PP mesh group compared with all other mesh samples. Conclusion  The use of the novel two-component monofilament mesh structure made of polypropylene and polyvinylidenfluoride was found to be favorable regarding adhesion formation and mesh shrinkage compared to conventional mesh materials used for intra-abdominal placement.