The structure of a biomaterial rather than its chemical composition modulates the repair process at the peritoneal level

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.     

Peritoneal Regeneration after Implant of a Composite Prosthesis in the Abdominal Wall

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 × 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.     

Effect of relaparotomy through previously integrated polypropylene and polytetrafluoroethylene experimental implants in the abdominal wall

BACKGROUND: 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. METHODS: 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. RESULTS: 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, p>0.001). 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, p<0.001). 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. CONCLUSIONS: 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.     

Peritoneal effects of prosthetic meshes used to repair abdominal wall defects: monitoring adhesions by sequential laparoscopy

BACKGROUND: The prosthetic materials currently used to repair abdominal wall defects sometimes have to be placed in contact with the visceral peritoneum. This interface is often a site of complications such as intestinal obstruction or fistulas due to adhesions. The aim of this study was to follow the process of adhesion formation in several prosthetic materials by sequential laparoscopy. MATERIAL AND METHODS: Defects (7 x 5 cm) were created in the abdominal wall of 30 New Zealand White rabbits and repaired using Surgipro polypropylene mesh (PP), Ultrapro monocryl-prolene mesh (UP), Dual Mesh expanded polytetrafluoroethylene (ePTFE), Composix (PP-ePTFE), Parietex Composite (polyester with collagen-polyethylene glycol-glycerol coating [PO-gl]), or PL-PU99 (PP-polyurethane) patches fixed to the edges of the defect by running polypropylene suture. Adhesions to the implants were laparoscopically determined at 3, 7, and 14 days after surgery. RESULTS: Percentage adhesion scores were significantly lower for ePTFE, PP-ePTFE, PO-gl, and PP-PU, compared to PP or UP. No differences were observed in adhesion scores recorded at 3, 7, and 14 days postimplant. Reticular prostheses were infiltrated by disorganized scar tissue with fibers concentric to the mesh filaments. In contrast, ePTFE implants were encapsulated by organized tissue, with fibers running parallel to the surface of biomaterial. All three composites achieved good recipient tissue integration and a homogeneous, organized, and well-vascularized neoperitoneum. CONCLUSION: At 14 days postimplant, laminar prostheses and composites showed similar results in terms of adhesion formation and integration within host tissue. Our findings suggest that both the composite prostheses and the laminar ePTFE performed very well in terms of reduced adhesion formation at the peritoneal interface.     

Tissue ingrowth and bowel adhesion formation in an animal comparative study: polypropylene versus Proceed versus Parietex Composite

Background The optimal prosthesis for laparoscopic ventral hernia repair would combine excellent parietal surface tissue ingrowth with minimal visceral surface adhesiveness. Currently, few data are available from randomized trials comparing the commercially available prostheses. Methods In a pig model designed to incite adhesions, three 10 × 15-cm pieces of mesh (Proceed, Parietex Composite [PCO], and polypropylene [PPM]) were randomly positioned intraperitoneally in each of 10 animals using sutures and tack fixation. After a 28-day survival, the amount of shrinkage, the area and peel strength of visceral adhesions, the peak peel strength, the work required to separate mesh from the abdominal wall, and a coefficient representing the adhesiveness of tissue ingrowth were averaged for each type of mesh and then compared with the averages for the other prostheses. The histologic appearance of each prosthesis was documented. Results Proceed had more shrinkage (99.6 cm²) than PCO (105.8 cm²) or PPM (112 cm²), although the difference was not statistically significant. The mean area of adhesions to PCO (11%) was significantly less than for Proceed (48%; p < 0.008) or PPM (46%; p < 0.008). Adhesion peel strength was significantly less for PCO (5.9 N) than for Proceed (12.1 N; p < 0.02) or PPM (12.9 N; p < 0.02). According to a filmy-to-dense scale of 1 to 5, adhesions were more filmy with PCO (1.7) than with PPM (2.9) or Proceed (3.7) (p < 0.007). Peak peel strength from the abdominal wall was significantly higher for PCO (17.2 N) than for Proceed (10.7 N) or PPM (10 N; p < 0.002). The histology of each prosthesis showed a neoperitoneum only with PCO. Conclusions With less shrinkage, fewer and less dense adhesions to the viscera, and significantly stronger abdominal wall adherence and tissue ingrowth at 28 days in this animal study, PCO was superior to both Proceed and PPM in all categories. Furthermore, PCO demonstrated all the favorable qualities needed in an optimal prosthesis for laparoscopic ventral hernia repair, including the rapid development of a neoperitoneum.     

Polyurethane-covered dacron mesh versus polytetrafluoroethylene DualMesh for intraperitoneal hernia repair in rats

Purpose: Abdominal hernia repair using the intraperitoneal implantation of a prosthesis requires mesh with impervious properties, such as expanded polytetrafluoroethylene (ePTFE). A newly developed polyurethane-covered polyester mesh with impervious properties has recently been introduced as a less expensive alternative to PTFE, and we compare these materials herein. Methods: The adhesion formation and stability of intraperitoneal abdominal hernia repairs with DualMesh (macroporous ePTFE mesh with a microporous component) and PolyesterComposite (the newly developed polyurethane-covered Dacron mesh) were compared in a rat model. Forty rats were randomly divided into two groups; ten animals from each group were killed after 14 days, and the other ten after 90 days. Results: The number and intensity of adhesions were comparable in the PolyesterComposite and PTFE groups. Loose adhesions were seen in 13 animals and appeared only selectively at the fixation sutures. Both PolyesterComposite and PTFE induced the formation of a smooth neoperitoneum on the intraperitoneal surface and showed a complete ingrowing of the prosthesis in the surrounding tissue. There were no significant differences between the prostheses in terms of clinical herniation pressure and hydroxyproline concentration. Conclusions: PolyesterComposite and PTFE are both suitable prostheses for intrapertoneal implantation, but PolyesterComposite is less expensive, which is an important advantage for clinical use. Received: September 27, 2001 / Accepted: January 8, 2002     

Temporary closure of the abdomen using a new composite prosthesis (PL-PU99)

BACKGROUND: Temporary abdominal wound closure is sometimes desirable when tension-free approximation of the wound edges is impractical or when reexploration is planned. METHODS: The behavior of a composite prosthesis (PL-PU99) designed by our group was evaluated as a method of temporary abdominal closure in white New Zealand rabbits. After a 7 cm long midline laparotomy, a spindle-shaped 4 cm (maximum width) by 7 cm (length) fragment of PL-PU99 was sutured to the edges of the peritoneal, muscular, and fascial abdominal tissues, so that the biomaterial remained in contact with the exterior. The PL-PU99 composite is composed of a polypropylene mesh adhered to a sheet of polyurethane with an acrylic cement. At 7 and 14 days after implant, animals were sacrificed and specimens taken for morphological, ultrastructural, morphometry of the neoperitoneum, and immunohistochemical (macrophage reaction, RAM-11) analysis. RESULTS: No death or signs of infection or rejection of the prostheses were recorded. No adhesions could be macroscopically observed between the composite and the intestinal loops. The biomaterial achieved a good seal, no leakage of fluids being detected. Fourteen days after implant, the neoperitoneum formed on the prosthesis was of an even structure and was made up of organized, vascularized connective tissue covered by an uninterrupted mesothelium. CONCLUSIONS: The PL-PU99 prosthesis shows optimal behavior at the prosthesis/visceral peritoneum interface, making it ideal for its use in the temporary closure of the abdomen. The implanted composite may also prove useful for the permanent repair of the abdominal wall.     

In vivo study of meshes implanted over the inguinal ring and external iliac vessels in uncastrated pigs

Background: The effects of placing a prosthesis directly on the internal inguinal ring and external iliac vessels in inguinal hernia repair are unknown. We compared tissue responses to five prostheses implanted in this position in uncastrated male pigs. Methods: Three types of polypropylene and two types of expanded polytetrafluoroethylene (ePTFE) mesh were implanted in 20 pigs (n= 8 for each prosthesis type). Specimens of the implants and surrounding tissue were obtained 30 and 90 days after implantation and assessed histologically. Results: The polypropylene implants had more adhesions, more surface area covered by adhesions, and more tenacious adhesions than did the ePTFE implants. Perivascular cuffing was observed in eight polypropylene and one ePTFE specimen; ossification, necrosis, and testicular venous congestion were seen in polypropylene specimens. Conclusions: Abnormal healing processes after implantation of polypropylene mesh may increase complications of the transabdominal preperitoneal and total extraperitoneal approaches in laparoscopic inguinal hernia repair, whereas the minimal response to ePTFE meshes may make them safer for use in the preperitoneal space. Received: 2 April 1997/Accepted: 8 August 1997     

A comparative study of adhesion formation and abdominal wall ingrowth after laparoscopic ventral hernia repair in a porcine model using multiple types of mesh

Background The ideal mesh for laparoscopic ventral hernia repair is not yet identified.Methods We laparoscopically placed polypropylene (PPM), expanded polytetrafluoroethylene (ePTFE), and polyester with antiadhesive collagen layer (PCO) in eight pigs using sutures and tacks for fixation. After 28-day survival, we compared adhesion formation, fibrous ingrowth, and shrinkage among the types of mesh.Results Mean area of adhesions to PCO (8.25%) was less than that to ePTFE (57.14%, p < 0.001) or PPM (79.38%, p < 0.001). Adhesions peel strength was less for PCO (2.3 N) than for PPM (16.1 N, p < 0.001) or ePTFE (8.8 N, p = 0.02). Peel strength of mesh from the abdominal wall was less for ePTFE (1.3 N/cm of mesh width) than for PCO (2.8 N/cm, p = 0.001) or PPM (2.1 N/cm, p = 0.05). ePTFE area (94.4 cm²) was less than that for PCO (118.6 cm², p < 0.001) or PPM (140.7 cm², p < 0.02).Conclusion PCO had fewer and less severe adhesions than ePTFE or PPM while facilitating excellent ingrowth of the adjacent parietal tissue.     

Laparoscopic transabdominal preperitoneal approach to place a polypropylene mesh on the abdominal wall: an experimental swine model of a technique that can be used for incisional hernia repair

Background The placement of intraabdominal polypropylene mesh entails risks of adhesions and fistulas that can be avoided by preperitoneal placement.Methods This comparative, open, experimental, prospective, randomized, and transversal study randomized pigs into two groups of 11 each for intraperitoneal (IPOM) or preperitoneal (TAPP) polypropylene mesh placement by laparoscopy. Diagnostic laparoscopy and tissue en-bloc resection was performed 28 days postoperatively for histopathologic analysis.Results The following data were observed for the two study groups: surgical time (IPOM: 35.73 ± 4.22 min; TAPP: 58.09 ± 6.28 min; p = <0.0001); adhesions (IPOM: 81.81%; TAPP: 27.27%; p = 0.032), grade III for IPOM and grade II for TAPP (p = 0.001); and interloop adhesions (IPOM: 81.81%; TAPP: 9.09%; p = 0.003). No fistulas were found in either group. The TAPP procedure showed better integration of mesh, without lesion to abdominal organs. Two complications, occurred with IPOM, and one with TAPP (p = 1.0, not significant).Conclusions The perperitoneal technique requires more time, but has fewer adhesions and less intraabdominal inflammatory response. It is a feasible technique that may diminish risks in the laparoscopic treatment of incisional hernias with polypropylene mesh.     

Ventral hernia repair using allogenic acellular dermal matrix in a swine model

Background This study was designed to assess the long-term efficacy of allogenic acellular dermal matrix (ADM) used as an interpositional graft for ventral hernia repair in a swine model.Methods We created 12×4-cm full-thickness abdominal wall defects in 22 Yucatan miniature pigs. The defect was repaired with either two 6×4-cm pieces of AlloDerm (acellular dermal matrix processed from pig skin in order to avoid a xenogenic response, LifeCell Corporation, Branchburg, NJ USA) (n=12), or expanded polytetrafluoroethylene mesh (ePTFE) (Gore-Tex, W.L. Gore & Associates, Inc., Newark, DE USA) (n=10). In six pigs, a separate 3-cm fascial incision was made, which was then suture repaired as a control for tensiometry testing. The surgical sites were evaluated at either 3 months or 9 months for the presence of a hernia, stretching of the implant, adhesions, vascularity, and biomechanical strength.Results Two hernias occurred in both the ADM and the ePTFE groups. There was minimal stretching of the implants and minimal adhesions in both groups. Fluorescein testing and histology indicated vascular ingrowth into the ADM. There was no statistical difference between the mean breaking strengths of the ADM-fascial interface (106.5 N±SD 40.1), the interface between two pieces of ADM (149.1 N±SD 76.7), and the primary fascial repair (108.1 N±SD 20.9) at 9 months. The ADM-fascial interface had a significantly higher breaking strength than that of the ePTFE-fascia interface (66.1 N±SD 30.1) (P=0.017, t-test, P=0.043 Wilcoxon rank sum test).Conclusions In this study, we were unable to demonstrate a difference between ADM and ePTFE in their ability to repair ventral hernias at 9 months in a swine model. The ADM additionally supports vascular ingrowth and exhibits increased breaking strength at the fascia-implant interface.This paper won the Fruchaud prize for best poster presentation at the American Hernia Society meeting in Orlando, Fla., USA, on February 27, 2004.This study was funded in part by an unrestricted donation to the University of Maryland Division of Plastic Surgery research fund from LifeCell Corporation. Dr. Ronald P. Silverman also has received honoraria from LifeCell Corporation as a speaker.     

Cine magnetic resonance imaging vs high-resolution ultrasonography for detection of adhesions after laparoscopic and open incisional hernia repair: a matched pair pilot analysis

Background Intraabdominal adhesions represent nonspecific complications before or after laparoscopic or open incisional hernia repair. The objective of this matched control pilot study was to display long-term adhesions noninvasively by applying functional cine magnetic resonance (MR) imaging, as compared with applying high-resolution ultrasonography (US). Methods The study group, composed of 17 consecutive patients (12 men and 5 women; mean age, 52 years), underwent laparoscopic intraperitoneal onlay mesh repair using expanded polytetrafluoroethylene (ePTFE) mesh. Their mean body mass index was 30 kg/m², and the size of the hernia was 95 cm². Another group, matched for age, gender, and type of hernia, was subjected to open abdominal wall repair using the preperitoneal sublay technique with a large-pore, low-weight polypropylene mesh. For cine MR imaging (1.5 T), section-by-section dynamic depiction of induced visceral slide throughout the entire abdomen was achieved by applying transverse or sagittal true fast imaging with steady-state precession sequences. The location and type of adhesions were compared with high-resolution ultrasonography using nine segments of the abdominal map. Results The patients subjected to laparoscopic and open incisional hernia repair were examined 16 and 28 months after surgery. The findings showed functional cine MR imaging as superior to high-resolution ultrasonography for assessing the amount of intraabdominal adhesions (n = 53 vs n = 3; p < 0.01). Most frequently, adhesions were seen between small bowel loops and the abdominal wall (n = 22), followed by bowel-to-bowel adhesions (n = 19; p < 0.05). However, adhesions between small bowel loops and the abdominal wall occurred more frequently after open mesh repair (p < 0.05). Furthermore, a strong correlation was observed between patient complaints and findings with cine MR imaging (p < 0.05). Maximum pain correlated significantly with the region of the most distinctive adhesions (p < 0.05). Conclusions Functional cine MR imaging represents a reliable noninvasive technique for detecting long-term adhesions after open and laparoscopic incisional hernia repair. The study results suggest that this approach has distinct advantages over high-resolution ultrasonography.     

Evaluation of a new composite prosthesis (PL-PU99) for the repair of abdominal wall defects in terms of 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.     

Minimal adhesions to ePTFE mesh after laparoscopic ventral incisional hernia repair: reoperative findings in 65 cases.

OBJECTIVES: Laparoscopic ventral incisional hernia repair involves intraabdominal placement of a synthetic mesh, and the possibility of formation of severe visceral adhesions to the prosthesis is a principal concern. Little clinical information based on reoperative findings is available about adhesions to biomaterials placed intraabdominally. We conducted a multiinstitutional study of adhesions to implanted expanded polytetrafluoroethylene (ePTFE) mesh at reoperation in patients who had previously undergone laparoscopic incisional hernia repair done with the same mesh implantation technique. METHODS: Nine surgeons retrospectively assessed the severity of adhesions to ePTFE mesh at reoperation in 65 patients. For each case, adhesions were assigned a score of 0 to 3, with 0 indicating no adhesions and 3 severe adhesions. RESULTS: The mean time from mesh implantation to reoperation was 420 days (range, 2 to 1739 days). No adhesions were observed in 15 cases. Forty-four cases received an adhesion score of 1, and 6 cases a score of 2; no scores of 3 were assigned. Thus, 59 patients (91%) had either no or filmy, avascular adhesions. No enterotomies occurred during adhesiolysis. CONCLUSIONS: In this large series of reoperations after laparoscopic incisional hernia repair, no or minimal formation of adhesions to implanted ePTFE mesh was observed in 91% of cases, and no severe cohesive adhesions were found. Comparative analyses of newer materials based on clinical reoperative findings are warranted to assess the safety of intraabdominally placed meshes.     

Minimal adhesions to ePTFE mesh after laparoscopic ventral incisional hernia repair: reoperative findings in 65 cases

BACKGROUND AND OBJECTIVES: Laparoscopic ventral incisional hernia repair involves intraabdominal placement of a synthetic mesh, and the possibility of formation of severe visceral adhesions to the prosthesis is a principal concern. Little clinical information based on reoperative findings is available about adhesions to biomaterials placed intraabdominally. We conducted a multi-institutional study of adhesions to implanted expanded polytetrafluoroethylene (ePTFE) mesh at reoperation in patients who had previously undergone laparoscopic incisional hernia repair done with the same mesh implantation technique. METHODS: Nine surgeons retrospectively assessed the severity of adhesions to ePTFE mesh at reoperation in 65 patients. For each case, adhesions were assigned a score of 0 to 3, with 0 indicating no adhesions and 3 severe adhesions. RESULTS: The mean time from mesh implantation to reoperation was 420 days (range, 2-1 739 days). No adhesions were observed in 15 cases. Forty-four cases received an adhesion score of 1, and 6 cases a score of 2; no scores of 3 were assigned. Thus, 59 patients (91 %) had either no or filmy, avascular adhesions. No enterotomies occurred during adhesiolysis. CONCLUSIONS: In this large series of reoperations after laparoscopic incisional hernia repair, no or minimal formation of adhesions to implanted ePTFE mesh was observed in 91 % of cases, and no severe cohesive adhesions were found. Comparative analyses of newer materials based on clinical reoperative findings are warranted to assess the safety of intraabdominally placed meshes.     

Strength of Tissue Attachment to Composite and ePTFE Grafts After Ventral Hernia Repair

Objectives:

We sought to measure the strength of tissue attachment to mesh after laparoscopic ventral hernia repair in a porcine model.

Methods:

Twelve swine had two 10-cm × 16-cm sheets of ePTFE and polypropylene/ePTFE composite mesh fixated to the abdominal wall laparoscopically. Animals were euthanized at 2, 4, 6, and 12 weeks. The strength of tissue ingrowth was measured using a lap-shear method. Data are reported as mean force in pounds.

Results:

Average surface area of adhesions to percentage of surface area was not statistically significant between the composite and ePTFE materials. For the composite material, there was a 98.7% posterior probability that the force required at 2 weeks was less than that required at 12 weeks. There was no difference in graft-abdominal wall interface strength between week 2 and week 12 for ePTFE material. Both prosthetics achieved the majority of their strength from tissue ingrowth by 2 weeks, but the composite prosthesis continued to gain strength while the strength of the ePTFE plateaued. Composite mesh demonstrated a statistically significant increase in strength between the lap-shear force, whereas no statistically significant difference occurred in the ePTFE graft. For the composite material, there was complete cellular infiltration through the entire thickness of polypropylene (approximately 500 μm) to the ePTFE layer at 2 weeks. At 2 weeks for ePTFE, the cells did not penetrate into the graft on the visceral side. On the abdominal wall side, the grooves filled with tissue, but no cellular penetration into the ePTFE occurred. No histological difference existed in cellularity.

Conclusion:

This study demonstrates that the strength of tissue ingrowth is significantly higher (P<0.05) for the composite grafts relative to the ePTFE grafts at each time point. Approximately 74% of tissue ingrowth and strength occurs by 2 weeks postoperatively for the composite pros-thesis. The ePTFE graft tissue strength peaked and plateaued by 2 weeks. This may have clinical implications for human ventral hernia repair by partly addressing the issue of graft fixation to the abdominal wall during laparoscopic ventral hernia repair.     

Effect of prosthetic material on adhesion formation after laparoscopic ventral hernia repair in a porcine model

Intraperitoneal placement of prosthetic mesh causes adhesion formation after laparoscopic incisional hernia repair. A prosthesis that prevents or reduces adhesion formation is desirable. In this study, 21 pigs were randomized to receive laparoscopic placement of plain polypropylene mesh (PPM), expanded polytetrafluoroethylene (ePTFE), or polypropylene coated on one side with a bioresorbable adhesion barrier (PPM/HA/CMC). The animals were sacrificed after 28 days and evaluated for adhesion formation. Mean area of adhesion formation was 14% (SD±15) in the PPM/HA/CMC group, 40% (SD±17) in the PPM group, and 41% (SD±39) in the ePTFE group. The difference between PPM/HA/CMC and PPM was significant (P=0.013). A new visceral layer of mesothelium was present in seven out of seven PPM/HA/CMC cases, six out of seven PPM cases, and two out of seven ePTFE cases. Thus, laparoscopic placement of PPM/HA/CMC reduces adhesion formation compared to other mesh types used for laparoscopic ventral hernia repairs.This work was presented as an oral presentation at the American Hernia Society Meeting, Tucson, Ariz. USA in May, 2002.This study was funded by a grant from Genzyme, Corp., Cambridge, Mass. USA     

Persistent posterior seroma after laparoscopic repair of ventral abdominal wall hernias with expanded polytetrafluoroethylene mesh: prevalence,independent predictors and detached tacks

Purpose

A persistent seroma located posterior to a mesh (PPS) remains a little known complication after laparoscopic ventral hernia repair (LVHR). The aim of this large case series was to analyse the prevalence and clinical course as well as identify related factors and independent predictors of PPS.

Methods

All 1288 adult patients who underwent a LVHR with an expanded polytetrafluoroethylene mesh (ePTFE) between January 2003 and July 2014 were reviewed. Those who underwent an abdominal computed tomography (CT) scan more than 3 months afterwards (n = 166) were included and their scans were analysed. The primary outcome measure was the prevalence of a PPS and its characteristics. The secondary outcome measures were identification of significantly related factors and independent predictors of PPS.

Results

A PPS was observed in 14 of 166 analysed CT scans (8.4%). Eleven patients were symptomatic; conservative treatment (wait-and-see policy) was successful in eight. Three underwent relaparoscopy with removal of a thick neoperitoneum. Several instances of tack and/or mesh detachment were identified on CT scans and during relaparoscopy. Independent predictors were: > 3 trocars (RR 5.0, 95% CI 1.6–15.8) and use of a mesh larger than > 300 cm² (RR 9.9, 95% CI 1.9–51.2).

Conclusions

A PPS is a relatively common complication after LVHR with an ePTFE mesh of usually larger hernias. A “wait-and-see” approach seems justified in most cases. Some require laparoscopic excision of the thick neoperitoneum. A PPS can cause tack and mesh detachment but the clinical consequences are unclear. Recurrences have not been observed in this series.

     

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.     

Results of laparoscopic repair of abdominal wall hernias using an ePTFE-polypropylene composite mesh

BACKGROUND: The standard technique for laparoscopic ventral hernioplasty (peritoneal onlay) reduces the recurrence rate and the rate of other complications, in particular the risk of infections. However, the procedure requires a special mesh to mitigate the risk of visceral adhesions. For this purpose an ePTFE mesh is generally used. There are limited reported clinical data regarding the long-term results and benefits of other biomaterials. STUDY DESIGN: Bard Composix mesh was used for laparoscopic ventral hernia repair. This biomaterial combines two different clinically proven materials--polypropylene with a thin layer of ePTFE--to maximize ingrowth of surrounding tissue, while mitigating the risk of visceral adhesions. Demographic, operative and postoperative data were collected and analyzed. Follow-up clinical evaluations were conducted 6-10 days, 4 weeks, and every 6 (th) month after surgery in all patients. RESULTS: Fifteen patients were involved in the study. The mean operating time was 101.2 min (64-190 min). There were no intraoperative complications or conversion to open procedure. Postoperative complications were 1 seroma, 4 cases of prolonged ileus, one tacks-site pain requiring second-look laparoscopy. Hospital discharge occurred on average 6 days (3-10 days) after surgery. The mean follow-up was 12.4 months (range 5-29 months). No late complications or hernia recurrence were observed. CONCLUSIONS: Laparoscopic prosthetic ventral hernioplasty using the composite polypropylene/ePTFE mesh offers short hospital stay and acceptable complications for primary and recurrent ventral hernias. Disadvantage of the composite mesh is the difficulty to roll this product into a sufficiently small size to permit its easy introduction into the abdominal cavity.