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.     

Comparison of two composite meshes using two fixation devices in a porcine laparoscopic ventral hernia repair model

Introduction Laparoscopic ventral hernia repair uses tacks to secure mesh. The mesh is designed to maximize tissue ingrowth while minimizing adhesions. We hypothesized: (1) a collagen-coated polyester mesh (PCO) will form fewer adhesions than an ePTFE-polypropylene composite (BC) and (2) absorbable tacks are equivalent to metal tacks.Methods In a porcine model of adhesion formation, three pieces of 10×15-cm mesh were placed on the anterior abdominal wall. PCO was secured with absorbable (PLA) or metal tacks (PT), BC with PT. At 28 days, adhesion formation, abdominal-wall adherence, and tissue ingrowth were analyzed.Results PCO induced fewer adhesions (14.5% vs 53.4%, P=0.007). On an adhesion scale (0–5), BC scored 3.6 vs 1.75 for PCO (P<0.03). There was no difference in adhesion strength, tack adhesions, or abdominal-wall peel force. Histology showed equal ingrowth.Conclusions PCO induces fewer adhesions than BC. There is no difference in the ingrowth of the two mesh types. The PLA achieves equivalent mesh incorporation to the PT.This work was presented at the meeting of the American Hernia Society, Orlando, Fla. USA, in February 2004     

Adhesion formation and reherniation differ between meshes used for abdominal wall reconstruction

Incisional hernia is a common surgical problem, frequently requiring prosthetic mesh repair. The demands of the ideal mesh seem conflicting; ingrowth at the mesh–fascia interface, without development of adhesions at the visceral mesh surface. Various antiadhesives combined with macroporous mesh and composite meshes were studied for prevention of adhesions to mesh and ingrowth into the fascia. In 60 rats an abdominal wall defect was created and repaired with underlay mesh. Rats were divided into six groups and treated with polypropylene mesh (PPM, control), PPM with auto-cross-linked polymers (ACP) gel, PPM with fibrinogen glue (FG), polypropylene/expanded polytetrafluoroethylene (ePTFE) mesh, polypropylene/sodium hyaluronate/carboxymethylcellulose (HA/CMC) mesh, and polypropylene-collagen/polyethylene-glycol/glycerol (CPGG) mesh. Mesh infection was assessed in the postoperative period, adhesions and reherniations were scored at sacrifice 2 months after operation, and tensile strength of the mesh–tissue interface was measured. Six rats developed mesh infection, half of them were treated with PPM/ePTFE. The PPM/HA/CMC group showed a significant reduction in the amount and severity of adhesions. In animals treated with PPM/ACP and PPM/FG, severity of adhesions was reduced as well. Reherniation rate in the PPM/ACP group was 50% and significantly higher than that in other groups. Rats in the PPM/HA/CMC had the highest tensile strength. PPM/HA/CMC approaches the demands of the ideal mesh best, having superior antiadhesive properties, no reherniation and no infection in this rat model of incisional hernia.     

Comparative evaluation of adhesion formation, strength of ingrowth, and textile properties of prosthetic meshes after long-term intra-abdominal implantation in a rabbit

BACKGROUND: Effective laparoscopic ventral herniorrhaphy usually mandates the use of an intraperitoneal prosthetic. Visceral adhesions and changes in textile characteristics of prosthetics may complicate repairs, especially long-term. The aim of this study was to compare the adhesion formation, tissue ingrowth, and textile characteristics one year after intra-abdominal placement of the commonly used prosthetic meshes. MATERIALS AND METHODS: Forty (4 x 4 cm) meshes were sutured using absorbable suture to an intact peritoneum in 20 New Zealand white rabbits. The study groups included: polypropylene (PP) [Marlex; C.R. Bard Inc, Cranston, NJ], expanded polytetrafluoroethylene (ePTFE) [DualMesh; WL Gore, Flagstaff, AZ], ePTFE and PP (ePTFE/PP) [Composix, C.R. Bard Inc], reduced weight PP and oxidized regenerated cellulose (rPP/C) [Proceed; Ethicon, Inc, Somerville, NJ]. The meshes were explanted after one year. Adhesions were scored as a percentage of explanted biomaterials' affected surface area. Prosthetic shrinkage was calculated. The strength of incorporation and mesh compliance were evaluated using differential variable reluctance transducers. Mesh ingrowth was measured as the load necessary to distract the mesh/tissue complex. Mesh compliance was calculated as the change in linear displacement of the sensors due to applied load. The groups were compared using Student's t-test and Fisher's exact test. RESULTS: ePTFE had significantly less adhesions (0%) than both ePTFE/PP (40%) and PP (80%) groups (P < 0.001). The mean area of adhesions for the rPP/C (10%) and the ePTFE/PP (14%) groups was less than that for the PP group (40%) (P = 0.02). Prosthetic shrinkage was greatest in the ePTFE (32%) group than in any other group (P = 0.001). There were no differences in mesh incorporation between the groups. At explantation, mesh compliance in the ePTFE group was superior to other meshes (P < 0.0001). The rPP/C mesh induced the smallest change in the compliance of the tissue adjacent to the mesh (P = 0.0001). CONCLUSIONS: Prosthetic materials demonstrate a wide variety of characteristics. Although exposed PP formed the most adhesions, up to 40% of the other PP-based meshes formed adhesions despite protective barriers. The ePTFE mesh did not induce adhesions and was the most compliant, however, this prosthetic's contraction was greatest. Reduced weight polypropylene (rPP/C) mesh induced the smallest change in the adjacent tissue pliability/compliance. Understanding of the long-term effects of various prosthetic materials is important to ensure an adequate hernia repair while minimizing postoperative morbidity and patient discomfort.     

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.     

Adhesion formation is reduced after laparoscopic surgery

Background: Adhesion formation after abdominal operations causes significant morbidity. Methods: Adhesion formation in pigs was compared after placement of prosthetic mesh during celiotomy (group 1), laparoscopy with large incision (group 2), and laparoscopy (group 3). After peritoneum was excised, polypropylene mesh was fixed to the abdominal wall, then to the opposite abdominal wall in the preperitoneal space followed by peritoneal closure. Adhesion area, grade, and vascularity were measured. Results: More adhesions (p < 0.02) covered intraperitoneal mesh (7.57 ± 1.89 cm²) than covered reperitonealized mesh (2.16 ± 1.13 cm²), and adhesion grade was significantly greater (p < 0.02). Adhesion areas were significantly greater in groups 1 and 2 than in group 3 (p= 0.001 and 0.03, respectively). Adhesion grade was significantly greater in groups 1 and 2 than in group 3 (p= 0.02 and p= 0.04, respectively). Groups 1 and 2 had more vascular adhesions than group 3 (p < 0.01 and p= 0.02, respectively) Conclusions: A foreign body within the peritoneum stimulates more numerous and denser adhesions. Tissue trauma distant from the site of adhesions increases their formation. A major advantage of laparoscopic surgery is decreased adhesion formation. Received: 23 January 1998/Accepted: 10 March 1998     

Evaluation of adhesion formation, mesh fixation strength, and hydroxyproline content after intraabdominal placement of polytetrafluoroethylene mesh secured using titanium spiral tacks, nitinol anchors, and polypropylene suture or polyglactin 910 suture

Background The purpose of this study is to evaluate fixation methods for polytetrafluoroethylene (ePTFE) mesh with an in vivo model of laparoscopic ventral hernia repair.Methods In 40 New Zealand white rabbits, a 4 × 4-cm ePTFE mesh (n = 80, two per animal) was attached to an intact peritoneum with polyglactin 910 (PG 910) (n = 20) or polypropylene (PP) (n = 20) suture, titanium spiral tacks (TS) (n = 20), or nitinol anchors (NA) (n = 20). Mesh was harvested at 8 and 16 weeks for fixation strength testing, adhesion assessment, and collagen (hydroxyproline) content. Fixation strength on day 0 was determined with mesh attached to harvested abdominal wall. Statistical significance was determined as p < 0.05.Results There was no difference in fixation strength between PP (39.1 N) and PG 910 (40.0 N) sutures at time zero. At week 8, PP (25.7 N) was significantly stronger (p < 0.05) than PG 910 (11.4 N) suture, but not at week 16. The fixation strength of TS and NA (day 0, 15.4 vs 7.4 N; week 8, 17.5 vs 15.3 N; week 16, 19.1 vs 13.8 N) was not significantly different. Fixation with PP suture was significantly (p < 0.05) stronger than that with TS and NA at day 0 (39.1, 15.4, and 7.4 N, respectively) but not at weeks 8 or 16. The fixation strength of suture decreased significantly (p < 0.05) from day 0 to week 16 (PP: day 0 = 39.1 N, week 8 = 25.7 N, week 16 = 21.4 N; PG 910: day 0 = 40.0 N, week 8 = 11.4 N, week 16 = 12.8 N). The fixation strength of NA and TS did not change significantly (NA: day 0 = 7.4 N, week 8 = 15.3 N, week 16 = 13.8 N; TS: week 0 = 15.4 N, week 8 = 17.5 N, week 16 = 19.1 N). There were no differences in adhesion area based on fixation device used; however, there were more (p < 0.05) mesh samples using NA with adhesions compared to TS and adhesion tenacity was greater (p < 0.05) compared to that of TS, PP, and PG. Hydroxyproline content at weeks 8 and 16 was similar for all fixation devices.Conclusions The initial fixation strength for nonabsorbable suture is significantly greater than that of the metallic fixation devices, but after 8 weeks there is no difference. Laparoscopic ventral hernia repair without transabdominal suture fixation may be predisposed to acute failure. The metallic devices have similar fixation strength, although the incidence of adhesions and tenacity of adhesions appear to be greater with the nitinol anchors. Since these devices have similar fixation strengths and most likely provide adequate supplementation to transabdominal sutures for mesh fixation after laparoscopic ventral hernia repair, their use should be based on other factors, such as their propensity for adhesions, ease of application, and cost.Paper presented at the annual meeting of the Society of American Gastrointestinal Endoscopic Surgeons (SAGES), Denver, Colorado, USA, March 31–April 3, 2004     

Assessment of adhesion formation to intra-abdominal polypropylene mesh and polytetrafluoroethylene mesh

BACKGROUND: The development of intra-abdominal adhesions, bowel obstruction, and enterocutaneous fistulas are potentially severe complications related to the intraperitoneal placement of prosthetic biomaterials. The purpose of this study was to determine the natural history of adhesion formation to polypropylene mesh and two types of polytetrafluoroethylene (ePTFE) mesh when placed intraperitoneally in a rabbit model that simulates laparoscopic ventral hernia repair. MATERIALS AND METHODS: Thirty New Zealand white rabbits were used for this study. A 10-cm midline incision was performed for intra-abdominal access and a 2 cm x 2 cm piece of mesh (n = 60) was sewn to an intact peritoneum on each side of the midline. Two types of ePTFE mesh (Dual Mesh and modified Dual Mesh, W.L. Gore & Assoc., Flagstaff, AZ) and polypropylene mesh were compared. The rate of adhesion formation was evaluated by direct visualization using microlaparoscopy (2-mm endoscope/trocar) at 7 days, 3 weeks, 9 weeks, and 16 weeks after mesh implantation. Adhesions to the prosthetic mesh were scored for extent (%) using the Modified Diamond Scale (0 = 0%, 1 50%). At necropsy the mesh was excised en bloc with the anterior abdominal wall for histological evaluation of mesothelial layer growth. RESULTS: The mean adhesion score for the polypropylene mesh was significantly greater (P < 0.05) than Dual Mesh at 9 weeks and 16 weeks and modified Dual Mesh at 7 days, 9 weeks, and 16 weeks. Fifty-five percent (n = 11) of the polypropylene mesh had adhesions to small intestine or omentum at necropsy compared to 30% (n = 6) of the Dual Mesh and 20% (n = 4) of the modified Dual Mesh. There was a significantly greater percentage (P < 0.003) of ePTFE mesh mesothelialized at explant (modified Dual Mesh 44.2%; Dual Mesh 55.8%) compared to the polypropylene mesh (12.9%). CONCLUSIONS: Serial microlaparoscopic evaluation of intraperitoneally implanted polypropylene mesh and ePTFE mesh in a rabbit model revealed a progression of adhesions to polypropylene mesh over a 16 week period. The pore size of mesh is critical in the development and maintenance of abdominal adhesions and tissue ingrowth. The macroporous polypropylene mesh promoted adhesion formation, while the microporous nature of the visceral side of the ePTFE served as a barrier to adhesions.     

Improved Biomechanical Resistance Using an Expanded Polytetrafluoroethylene Composite-Structure Prosthesis

We designed a composite-structure (laminar-reticular) prosthesis using expanded polytetrafluoroethylene (ePTFE) as the biomaterial in an attempt to improve the biomechanical resistance of the same biomaterial in the form of a single lamina. Defects (7 × 5 cm) were created in the abdominal wall of male white New Zealand rabbits (n = 24). The defects, which comprised all the wall layers except the skin, were then repaired with one of two types of ePTFE prosthesis. One was a latest generation laminar prosthesis (DualMesh, or Gore-Tex) and the other was a composite of in-house design (CV-4 mesh composite) made by suturing a mesh woven out of ePTFE thread to an ePTFE lamina. After sacrificing the animals at 14 or 90 days after surgery, implant specimens were subjected to morphologic analysis (light microscopy and scanning electron microscopy); and adhesion formation, neoperitoneal thickness, and biomechanical strength were evaluated. No significant differences were recorded between the two prosthesis regarding the consistency of adhesions or the area occupied by adhesions (DM 0.17 ± 0.06; CV-4 mesh composite 0.18 ± 0.08 cm²) (p > 0.05). Notably, improved tissue integration was achieved using the composite prosthesis; its reticular side became infiltrated by dense connective tissue that enveloped the mesh filaments. In contrast, the DM prosthesis became encapsulated by host tissue. The neoperitoneum induced by both prostheses was homogeneous and orderly, with a layer of typical mesothelial cells lining its inner surface. The thickness of the neoperitoneum was similar (p > 0.05) for the two implants (385.0 ± 3.4 vs. 390 ± 3.1 m), although significantly higher (p < 0.05) mechanical resistance values were recorded for the composite prosthesis (26.75 ± 3.71 vs. 14.11 ± 3.71 N). Our findings suggest that the use of a reticular and a laminar ePTFE layer in the same prosthesis leads to better repair and biomechanical behavior compared to the use of a single-structure laminar implant.     

Evaluation of adhesion formation and host tissue response to intra-abdominal polytetrafluoroethylene mesh and composite prosthetic mesh

BACKGROUND: The purpose of this study was to measure the extent of adhesion formation to ePTFE mesh (DualMesh, W.L. Gore & Associates, Inc, Flagstaff, AZ) and two composite prosthetic materials, ePTFE and polypropylene (Bard Composix, C.R. Bard, Inc, Murray Hill, NJ) and hyaluronic acid/carboxymethylcellulose and polypropylene (Sepramesh, Genzyme Corp, Cambridge, MA) after their intra-abdominal placement on an intact peritoneum, simulating laparoscopic ventral hernia repair, and to evaluate host tissue response to the prosthetic biomaterials. MATERIALS AND METHODS: Through a midline laparotomy, a 2 x 2 cm piece of mesh (n = 60) was sewn to an intact peritoneum on each side of a midline incision in 30 New Zealand white rabbits. Mesh adhesions were scored using a modified Diamond scale (0 = 0%, 1 = 1-25%, 2 = 26-50%, 3 >50%) at 1, 3, 9, and 16 weeks by serial microlaparoscopy (2 mm). All laparoscopic evaluations were videotaped for blinded scoring by three surgeons. Host tissue response was graded (1-4) for inflammation, tissue ingrowth, and mesothelialization. The predominant cell type (polymorphonuclear leukocytes versus foreign body giant cell) was recorded. Statistical differences (P value <0.05*) were measured using a two-tailed t test and Kruskal-Wallis test. RESULTS: The mean adhesion score was significantly (P < 0.001) less for ePTFE mesh at 1, 3, 9, and 16 weeks compared with the two composite prosthetic materials. There were no differences in the mean adhesion scores between the two biosurgical composite meshes at any of the time intervals. There were no differences in the mean score for inflammation, tissue ingrowth and mesothelialization between any of the prosthetic biomaterials. The predominant cell type on all histological evaluations was polymorphonuclear leukocytes. CONCLUSIONS: Placing ePTFE mesh (DualMesh) intra-abdominal against an intact peritoneum results in significantly fewer adhesions than the composite prosthetic meshes during a 4-month follow-up. The host tissue response is equivalent for the three prosthetic biomaterials. The long-term consequences of increased adhesion formation to the composite meshes and the ultimate biocompatibility of the nonabsorbable and absorbable barriers on the polypropylene mesh are to be determined.     

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     

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.     

Prevention of adhesion formation to polypropylene mesh by collagen coating: A randomized controlled study in a rat model of ventral hernia repair

Introduction In laparoscopic incisional hernia repair with intraperitoneal mesh, concern exists about the development of adhesions between bowel and mesh, predisposing to intestinal obstruction and enterocutaneous fistulas. The aim of this study was to assess whether the addition of a collagen coating on the visceral side of a polypropylene mesh can prevent adhesion formation to the mesh.Method In 58 rats, a defect in the muscular abdominal wall was created, and a mesh was fixed intraperitoneally to cover the defect. Rats were divided in two groups; polypropylene mesh (control group) and polypropylene mesh with collagen coating (Parieten mesh). Seven and 30 days postoperatively, adhesions and amount and strength of mesh incorporation were assessed. Wound healing was studied by microscopy.Results With Parieten mesh, the mesh surface covered by adhesions was reduced after 30 days (42% vs 69%, p = 0.01), but infection rate was increased after both 7 (p = 0.001) and 30 days (p = 0.03), compared to the polypropylene group with no mesh infections. If animals with mesh infection were excluded in the analysis, the mesh surface covered by adhesions was reduced after 7 days (21% vs 76%, p = 0.02), as well as after 30 days (21 vs 69%, p < 0.001). Percentage of mesh incorporation was comparable in both groups. Mean tensile strength of mesh incorporation after 30 days was higher with Parieten mesh.Conclusion Although the coated Parieten mesh was more susceptible to mesh infection in the current model, a significant reduction of adhesion formation was still seen with the Parieten mesh after 30 days, with comparable mesh incorporation in the abdominal wall.     

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.     

Relationship Between Tissue Ingrowth and Mesh Contraction

Contraction is a well-documented phenomenon occurring within two months of mesh implantation. Its etiology is unknown, but it is suggested to occur as a result of inadequate tissue ingrowth into the mesh and has been associated with hernia recurrence. In continuation of our previous studies, we compared tissue ingrowth characteristics of large patches of polyester (PE) and heavyweight polypropylene (PP) and their effect on mesh contraction. The materials used were eight PE and eight PP meshes measuring 10 × 10 cm². After random assignment to the implantation sites, the meshes were fixed to the abdominal wall fascia of swine using interrupted polypropylene sutures. A necropsy was performed three months after surgery for evaluation of mesh contraction/shrinkage. Using a tensiometer, tissue ingrowth was assessed by measuring the force necessary to detach the mesh from the fascia. Histologic analysis included inflammatory and fibroblastic reactions, scored on a 0–4 point scale. One swine developed a severe wound infection that involved two PP meshes and was therefore excluded from the study. The mean area covered by the PE meshes (87 ± 7 cm²) was significantly larger than the area covered by the PP meshes (67 ± 14 cm²) (p = 0.006). Tissue ingrowth force of the PE meshes (194 ± 37 N) had a trend toward being higher than that of the PP meshes (159 ± 43 N), although it did not reach statistical significance. There was no difference in histologic inflammatory and fibroblastic reactions between mesh types. There was a significant correlation between tissue ingrowth force and mesh size (p = 0.03, 95% CI: 0.05–0.84). Our results confirm those from previous studies in that mesh materials undergo significant contraction after suture fixation to the fascia. PE resulted in less contraction than polypropylene. A strong integration of the mesh into the tissue helps prevent this phenomenon, which is evidenced by a significant correlation between tissue ingrowth force and mesh size. Presented at the Southeastern Surgical Congress 2004 Meeting, Atlanta, GA, January 31–February 3, 2004 This study was sponsored by Promethian Surgical Devices, Boston, MA, USA.     

Tissue attachment strength of prosthetic meshes used in ventral and incisional hernia repair. A study in the New Zealand White rabbit adhesion model

Background: Many prosthetic materials are used in incisional hernia repair, including polypropylene (PP) and expanded polytetrafluoroethylene (ePTFE). However, PP forms severe adhesions and ePTFE has raised concerns about the adequacy of tissue attachment. Methods: The early tissue attachment strength of PP and two new forms of ePTFE (DLM and DLMC) was compared in a rabbit model (n = 12) in which disks of the three meshes (n = 8 of each material) were implanted against the abdominal wall for 3 days. Results: Tensiometer testing found that DLMC mesh had significantly greater attachment strength than PP (p = 0.02). Histologic studies indicated that this was due to cellular ingrowth. Tissue adhesions were observed with all eight PP disks, one DLMC disk, and none of the DLM disks. Conclusion: Modified forms of ePTFE mesh may provide abdominal wall repairs that are as strong or stronger than those obtained with PP, with early tissue attachment and without adhesions.     

Comparison of laparoscopic and open repair of incisional and primary ventral hernia: results of a prospective randomized study

Background Incisional hernia is an important complication of abdominal surgery. Its repair has progressed from a primary suture repair to various mesh repairs and laparoscopic repair. Laparoscopic mesh repair is a promising alternative, and in the absence of consensus, needs prospective randomized controlled trials. Methods Between April 2003 and April 2005, 66 patients with incisional, primary ventral and recurrent hernias were randomized to receive either open retrorectus mesh repair or laparoscopic mesh repair. These patients were followed up at 1-, 3-, and 6-month intervals thereafter for a mean of 12.17 months (open repair group) and 13.73 months (laparoscopic repair group). Results Lower abdominal hernias after gynecologic operations constituted the majority of the hernias (∼50%) in both groups. There was no significant injury to viscera or vessel in either group and no conversions. The defect size was 42.12 cm² in the open (group 1) and 65.66 cm² in the laparoscopic group (group 2), and the prosthesis sizes were, respectively, 152.67 cm² and 203.83 cm². The hospital stay was 3.43 days in open group and 1.47 days in laparoscopic group (p = 0.007). There was no significant difference in the pain scores between the two groups. More wound-related infectious complications occurred in the open group (33%) than in the laparoscopic group (6%) (p = 0.013). There was one recurrence in the open repair group (3%) and two recurrences in laparoscopic group (6%) (p = 0.55). Conclusions Laparoscopic repair of incisional and ventral hernias is superior to open mesh repair in terms of significantly less blood loss, fewer complications, shorter hospital stay, and excellent cosmetic outcome.     

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.     

Prospective histologic evaluation of intra-abdominal prosthetics four months after implantation in a rabbit model

Background

Placement of an intraperitoneal prosthetic is required for laparoscopic ventral hernia repair. The biocompatibility of these prosthetics determines the host’s inflammatory response, scar plate formation, tissue ingrowth, and subsequent mesh performance, including prosthetic compliance and prevention of hernia recurrence. We evaluated the host response to intraperitoneal placement of several prosthetics currently used in clinical practice.

Methods

A 4-cm × 4-cm piece of mesh was implanted on intact peritoneum in New Zealand white rabbits. The mesh types included expanded polytetrafluoroethylene (ePTFE) (DualMesh^®), ePTFE and polypropylene (Composix^®, heavyweight polypropylene), polypropylene and oxidized regenerated cellulose (Proceed^®, midweight polypropylene), and polypropylene (Marlex^®, heavyweight polypropylene). At four months, standard hematoxylin and eosin and Milligan’s trichrome stains of the mesh-tissue interaction were analyzed by three observers blinded to the mesh types. Each specimen was evaluated for scar plate formation, inflammatory response, and tissue ingrowth. Each of these three categories was graded on a standard scale of 1–4 (1 = normal tissue and 4 = severe inflammatory response). The scores were analyzed using Wilcoxon rank sum test with p < 0.05 as significant.

Results

Ten samples of each mesh type were evaluated. There was no difference in tissue incorporation between the groups. The mean scar plate formation was greater in the heavyweight polypropylene meshes than for DualMesh (p = 0.04). With Proceed, the reduction in scar plate formation compared with that for Composix and Marlex approached statistical significance (p = 0.07). The mean number of inflammatory cells was greater around the ePTFE when compared with the midweight polypropylene (p = 0.02) but equal to the other meshes.

Conclusions

The four prosthetic materials evaluated in this study demonstrate comparable host biocompatibility as evidenced by the tissue ingrowth. Scar plate formation around DualMesh was significantly less than that around Composix and Marlex. Interestingly, more inflammatory cells were noted surrounding the DualMesh which was equal to that of the heavyweight meshes. Proceed, a midweight polypropylene mesh, has the potential for improved patient tolerance compared to heavyweight polypropylene meshes based on its favorable histologic findings.     

Prevention of intraabdominal adhesions produced by polypropylene mesh

Polypropylene mesh (PPM) is widely used in ventral hernia repair, however is also associated with visceral adhesions when the mesh is exposed to intraabdominal organs. In this study, a composite mesh [ePTFE (expanded polytetrafluoroehylene) + PPM] and sodium hyaluronate/carboxymethyl cellulose (NaHA/CMC) membrane laid under PPM are evaluated in terms of adhesion formation in a rat model of ventral hernia repair. In this experimental study, a 2 x 1 cm of peritoneum and underlying muscle defect was created at the right side of the anterior abdominal wall of 37 male Wistar albino rats. These defects were repaired with 2.5 x 2 cm PPM in group 1 (n = 13), with composite mesh in group 2 (n = 12) and with PPM+NaHA/CMC in group 3 (n = 12). Rats were sacrificed after 14 days and the prosthetic materials were examined for the calculation of surface area percentage covered by adhesions, for organ involvement in the adhesions and for histological evaluation. There was a reduction in the adhesion-covered area in group 2 and group 3. Organ involvement was predominantly seen in group 1. Neoperitoneum was perfect in group 2. Fibrosis and inflammation were higher in group 1. All groups showed adhesiogenic potential to some extent. This potential was maximum with PPM. Both ePTFE and NaHA/CMC displayed similar effects in preventing adhesion formation.