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

Prevention of Intraabdominal Adhesions: An Experimental Study Using Mitomycin-C and 4% Icodextrin

Background:

Intraabdominal adhesions remain a significant cause of morbidity and mortality. Moreover, intraabdominal adhesions can develop in more than 50% of abdominal operations.

Aims:

We compared the anti-adhesive effects of two different agents on postoperative adhesion formation in a cecal abrasion model.

Study Design:

Experimental animal study.

Methods:

Forty Wistar albino type female rats were anesthetized and underwent laparotomy. Study groups comprised Sham, Control, Mitomycin-C, 4% Icodextrin, and Mitomycin-C +4% Icodextrin groups. Macroscopic and histopathological evaluations of adhesions were performed.

Results:

The frequencies of moderate and severe adhesions were significantly higher in the control group than the other groups. The mitomycin-C and Mitomycin-C +4% Icodextrin groups were associated with significantly lower adhesion scores compared to the control group and 4% Icodextrin group scores (p=0.002 and p=0.008, respectively). The adhesion scores of the Mitomycin-C group were also significantly lower than those of the 4% Icodextrin group (p=0.008).

Conclusion:

Despite its potential for bone marrow toxicity, Mitomycin-C seems to effectively prevent adhesions. Further studies that prove an acceptable safety profile relating to this promising anti-adhesive agent are required before moving into clinical trials.

[The first experience of using a single-layer intra-abdominal collagen plate]

The aim of this study was to define the possibility of using a collagen substance CollGARA as a protective barrier between the polypropylene mesh implant and abdominal organs. The drug is a sterile bioabsorbable membrane consisting of refolded equine collagen. Indications--use as barrier separating adjoining tissues and organs in the areas of the abdominal cavity, where the formation of adhesions.

MATERIALS AND METHODS

Were performed 10 operations in patients with ventral hernias with different localization. 8 patients had postoperative hernia in 2--linea alba hernia. 8 patients were operated open, 2--laparoscopically. After intra-abdominal hernia repair was performed plastic mesh implant, delimiting it from the abdominal cavity membrane CollGARA. Serious complications from the abdominal cavity and the surgical wound wasnt observed.

RESULTS

The first experience with intra-abdominal plastic polypropylene mesh implant coated with collagen plate indicates the possibility of applying this method in the future.

Evaluation of three purely polypropylene meshes of different pore sizes in an onlay position in a New Zealand white rabbit model

BACKGROUND

The aim of the study was to evaluate the influence of the pore size of a polypropylene mesh on the shrinkage and elasticity of the mesh-tissue complex and the inflammatory reaction to the implant in an open onlay hernia repair.

MATERIALS AND METHODS

Twenty-one 10 × 10 cm samples of polypropylene meshes of a different pore size (3.0 × 2.8 mm-PP3, 1.0 × 0.8 mm-PP1 and 0.6 × 0.5 mm-PP.5) were implanted in an onlay position in 21 New Zealand white rabbits. After 90 days of implantation the shrinkage, elasticity and foreign body reaction (FBR) were assessed.

RESULTS

The shrinkage of PP3 was 30.6 ± 4.3 %, PP1 49.3 ± 2.9 % and PP.5 49.5 ± 2.6 %. The shrinkage of PP3 was significantly lower (PP3 × PP1 p = 0.007, PP3 × PP.5 p = 0.005), PP1 and PP.5 were similar. The elasticity was similar. The strength of FBR in mesh pores was similar. The width of foreign body granuloma layers at the mesh-tissue interface was significantly reduced with increasing pore size (inner: PP3 10.1 ± 1.2; PP1 12.5 ± 2.9; PP.5 17.4 ± 5.2 and outer: PP3 21.2 ± 2.5; PP1 30.6 ± 6.3; PP.5 60.4 ± 14.9). All differences between the widths of granuloma layers were statistically significant (p < 0.010). One animal (PP1) was excluded because of a mesh infection.

CONCLUSIONS

Implantation of polypropylene mesh of a pore size of 3 mm in an onlay position is associated with a significant reduction of shrinkage in comparison to a 1 mm pore lightweight and 0.5 mm pore heavyweight mesh. A pore size increase to 3 mm is not sufficient for an improvement of mesh-tissue complex elasticity in comparison to a 1 mm pore lightweight and 0.5 mm heavyweight mesh. Polypropylene mesh with enlarged pores to 3 mm is associated with a similar strength of FBR in mesh pores and a reduced foreign body granuloma in comparison to a 1 mm pore lightweight and 0.5 mm pore heavyweight mesh.

Nonwoven polypropylene prosthesis in large abdominal wall defects in rats

PURPOSE

To evaluate, in large abdominal wall defects surgically shaped in rats, if a synthetic polypropylene nonwoven prosthesis could be used as a therapeutic option to conventional polypropylene mesh.

METHODS

Twenty four (24) Wistar rats were enrolled into three groups. Group 1 (Simulation group) with an abdominal wall defect of 3 X 3 left untreated and Groups 2 and 3, respectively treated with a conventional polypropylene mesh and a polypropylene nonwoven (NWV) prosthesis to cover the breach. At the 45th postoperatively day, adhesion (area and strength) and vascularization of Groups 2 and 3 were evaluated. The histological preparations with Hematoxylin-Eosin, Tricromium of Masson, Pricrosirius red and polarization with birefringence, and also the structural analysis of the prostheses carried on by Thermogravimetry and Differential Scanning Calorimetry were also assessed.

RESULTS

There were no significant differences between the Groups 2 and 3.

CONCLUSION

In rats, the polypropylene nonwoven prosthesis showed to be safe and has to be considered as an alternative to conventional mesh manufactured by weaving in the treatment of great defects of the abdominal wall.

Coated meshes for hernia repair provide comparable intraperitoneal adhesion prevention

BACKGROUND

Laparoscopic incisional hernia repair with intraperitoneal mesh is associated with a certain degree of adhesion formation to the mesh. This experimental study examined the efficacy of several coated meshes for adhesion reduction.

METHODS

Five commercially available meshes with a layered coating were placed intraperitoneally in rats and followed up for 90 days: polypropylene and polyester meshes, both coated with absorbable collagen (Parietene Composite and Parietex Composite, respectively), and three polypropylene meshes respectively coated with absorbable omega-3 fatty acids (C-Qur Edge), absorbable cellulose (Sepramesh IP), and nonabsorbable expanded polytetrafluoroethylene (Intramesh T1). Uncoated polypropylene and collagen meshs (Parietene and Permacol, respectively) served as the control condition. Adhesions, incorporation, and tissue reaction were evaluated macro- and microscopically. Additionally, the development of the neoperitoneum was examined.

RESULTS

All the coated meshes performed equally well in terms of adhesion reduction. The collagen mesh performed comparably, but the uncoated polypropylene mesh performed significantly worse. The different coatings led to very differing degrees of inflammation. Ingrowth was observed only at the place of suture but was comparable for all the meshes except C-Qur Edge, which showed the weakest incorporation. Development of a neoperitoneum on the mesh surface occurred independently of whether an absorbable or nonabsorbable coating or no coating at all was present.

CONCLUSIONS

Commercially available meshes with a layered coating deliver comparable adhesion reduction. The physical presence of a layered coating between the intraperitoneal content and the abdominal wall seems to be more important than the chemical properties of the coating in adhesion formation.

Comparative evaluation of adhesions to intraperitoneally placed fixation materials: a laparoscopic study in rats: adhesions to fixation materials

After laparoscopic ventral hernia repair, the nature of the adhesions to fixation materials or to mesh had not been clarified. We examined adhesion formation specific to the fixation material in rats. We designed an experimental laparoscopy setup, and placed four intraperitoneal fixation materials on the peritoneum of rats without a mesh graft. Another group of researchers documented the incidence and intensity of postoperative adhesion formation. The adhesion scores for the nickel-titanium anchor were significantly greater than those for polylactic acid (p = 0.004), a titanium tacker (p < 0.0001), and fibrin glue (p < 0.0001). No adhesions occurred in the fibrin glue group. Fibrin glue is the preferred fixation material because it produced no postoperative adhesions. The nickel-titanium anchor produced heavy adhesions but may be applicable for recurrent hernia cases and in patients with thin abdominal walls.

Novel technique of overlaying a poly-L: -lactic acid nanosheet for adhesion prophylaxis and fixation of intraperitoneal onlay polypropylene mesh in a rabbit model

BACKGROUND

One problem with polypropylene mesh (PPM) used to repair abdominal wall hernias is dense adhesions to the visceral surface. The authors developed the biocompatible poly-L: -lactic acid (PLLA) nanosheet (thickness < 100 nm), which has the unique ability to adhere tightly to tissues but not to opposing tissues. This study investigated the antiadhesive and fixative characteristics of the PLLA nanosheet after placement of intraperitoneal onlay PPM (IPOM) overlaid with a PLLA nanosheet on intact peritoneum.

METHODS

The PLLA nanosheet was fabricated by the spin-coating method and peeling technique with polyvinyl alcohol (PVA) as a supporting film. Two 1.5-cm-square pieces of mesh were implanted on each peritoneal side of the midline incision. The mesh was fixed to the peritoneum with a suture and then overlaid with a 4-cm-square piece of Seprafilm or nanosheet. To examine the fixative property, mesh was overlaid with Seprafilm or nanosheet without a fixed suture. After 4 weeks, mesh adhesion, inflammatory reaction, fixation, and dislocation of mesh were evaluated.

RESULTS

Nanosheet-overlaid meshes were flexible and fit over the peritoneum. Adhesion was observed in 10% of the nanosheet-overlaid meshes and in 50% of the Seprafilm-overlaid meshes. The adhesion tenacity grade was significantly lower with the nanosheet-overlaid meshes (0.1 ± 0.1) than with the Seprafilm-overlaid meshes (1.0 ± 0.4) (p = 0.029), and the percentage of the adhesion area also was lower with the nanosheet-overlaid meshes (1.0 ± 1.0% vs 8.5 ± 3.2%; p = 0.037). The mean inflammatory cell counts were lower with the nanosheet-overlaid meshes (p = 0.0023). Regarding the fixative property, 37.5% of the nanosheet-overlaid meshes were fixated on the peritoneum, but no Seprafilm-overlaid mesh was fixated.

CONCLUSION

Overlaying of a PLLA nanosheet was effective for adhesion prophylaxis of intraperitoneal mesh. It also may have a possible beneficial effect on fixation of mesh.

Biocompatibility of prosthetic meshes in abdominal surgery

Surgical meshes today represent a group of implants mainly used for hernia repair. Modern hernia surgery is no longer imaginable without the application of these special biomaterials leading to millions of implantations each year worldwide. Because clinical trials are insufficient to evaluate the distinct effects of modified mesh materials in regard to tissue biocompatibility and functionality, a basic understanding of the physicochemical properties of mesh materials, as well as the underlying cause for hernia formation, is essential for a rational selection of the most appropriate device. The most important properties of meshes were found to be the type of filament, tensile strength, and experimental data, which indicate that particularly the mesh's porosity is of outstanding importance.

Comparison of three separate antiadhesive barriers for intraperitoneal onlay mesh hernia repair in an experimental model

Background

Adhesion formation is a common adverse effect in intraperitoneal onlay mesh (IPOM) surgery. Different methods of adhesion prevention have been developed, including coated meshes and separate antiadhesive barriers (SABs). In this study one type of mesh was tested with different SABs, which were fixed to the sutured mesh using fibrin sealant. The primary aim was to compare adhesion prevention between different SABs. Secondary aims were the assessment of tissue integration and evaluation of SAB fixation with fibrin sealant.

Methods

Thirty-two rats were randomized to one of three treatment groups (SurgiWrap®, Prevadh® and Seprafilm®) or a control group (no SAB). Animals were operated on with an open IPOM technique (8 per group). One macroporous polypropylene mesh per animal (2 × 2 cm) was fixed with four non-absorbable sutures. An antiadhesive barrier of 2·5 × 2·5 cm was fixed with fibrin sealant. After 30 days, adhesion formation, tissue integration, seroma formation, inflammation and vascularization were evaluated macroscopically and by histology.

Results

Prevadh® and Seprafilm® groups showed a significant reduction in adhesion formation compared with the control group. Tissue integration of the mesh was reduced in these groups. Fibrin sealant fixed the SAB to the mesh securely in all groups.

Conclusion

Prevadh® and Seprafilm® are potent materials for the reduction of adhesion formation. A potential relationship between effective adhesion prevention and impaired tissue integration of the implant was observed. Fibrin sealant proved an excellent agent for SAB fixation.

A comparison of a bovine albumin/glutaraldehyde glue versus fibrin sealant for hernia mesh fixation in experimental onlay and IPOM repair in rats

BACKGROUND

Research in hernia repair has targeted new atraumatic mesh fixation to reduce major complications such as chronic pain and adhesion formation. The efficacy and safety of two surgical adhesives, viz. Artiss® (FS, fibrin sealant containing 4 IU thrombin) and Bioglue® (AGG, bovine serum albumin/glutaraldehyde glue), were evaluated in this study. Primary study endpoints were tissue integration, dislocation, and adhesion formation. Foreign-body reaction formed the secondary study endpoint.

METHODS

Twenty-four polypropylene meshes (VM, Vitamesh®) were randomized to four groups (n = 6): two groups of onlay hernia repair (two meshes per animal) with mesh fixation by FS (O-FS) or by AGG (O-AGG), and two groups of IPOM repair (one mesh per animal) with mesh fixation by four sutures and FS (I-FS) or AGG (I-AGG). Eighteen rats underwent surgery. Follow-up was 30 days. Tissue integration, dislocation, seroma formation, inflammation, adhesion formation, and foreign-body reaction were assessed.

RESULTS

Meshes fixed with FS (O-FS, I-FS) showed good tissue integration. No dislocation, seroma formation, or macroscopic signs of inflammation were detectable. Adhesion formation of I-FS was significantly milder compared with I-AGG (P = 0.024). A moderate foreign-body reaction without active inflammation was seen histologically in O-FS and I-FS groups. Samples fixed with AGG (O-AGG, I-AGG) showed extensive scar formation. No dislocation and no seroma formation were observed. All of these samples showed moderate to severe signs of inflammation with abscess formation in the six meshes of O-AGG. Histology underlined these findings.

CONCLUSIONS

The fibrin sealant adhesive showed very good overall results of the primary and secondary outcome parameters. FS is a recommendable atraumatic fixation tool for the surgical onlay technique. AGG provides high adhesive strength, but shows low biocompatibility. Persisting active inflammation was seen in both the O-AGG and I-AGG groups, not favoring its use for these indications.

Intraperitoneal onlay mesh: an experimental study of adhesion formation in a sheep model

PURPOSE

Current hernia literature shows that the use of mesh in ventral hernia repair reduces the risk of recurrence significantly. In laparoscopic repair, the mesh is placed intraperitoneally. Accordingly, the close contact between mesh and viscera involves a risk of adhesion formation. In this experimental study, we examined the degree of de novo adhesion formation over time to currently available meshes.

METHODS

Sixteen sheep each received laparoscopic placement of four (10 x 10 cm) meshes on intact peritoneum. Two different mesh materials (coated vs. non-coated) and two different fixation devices (absorbable/non-absorbable) were investigated. (Parietex Composite, DynaMesh IPOM, ProTack and AbsorbaTack). After 3, 6, 12 and 18 months, four animals, respectively, underwent a new laparoscopy to determine the extent of adhesions to the mesh.

RESULTS

Parietex Composite significantly reduced the formation of intraabdominal adhesions compared to DynaMesh IPOM. The mean extent of adhesions increases over time without reaching a steady state within the first 12 months after laparoscopic placement.

CONCLUSIONS

This is the first long-term (18 months) experimental study on adhesion formation in sheep after laparoscopic placement of mesh and may serve as a template for future studies on meshes before marketing.

Degradation of mesh coatings and intraperitoneal adhesion formation in an experimental model

BACKGROUND

In laparoscopic ventral hernia repair a mesh is placed in direct contact with the viscera, often leading to substantial adhesions. In this experimental study the ability of different coated and uncoated meshes to attenuate adhesion formation was examined.

METHODS

Six commercially available meshes were placed intraperitoneally against a closed peritoneum in rats: Prolene (polypropylene), Timesh and Ultrapro (polypropylene composites with titanium and polyglecaprone respectively), Proceed and Parietex Composite (polypropylene and polyester meshes coated with a layer of cellulose and collagen respectively) and C-Qur (polypropylene mesh coated with a layer of omega-3 fatty acids). Adhesions and incorporation were evaluated macroscopically and microscopically after 7 and 30 days.

RESULTS

Parietex Composite and C-Qur significantly reduced adhesion formation at 7 days' follow-up compared with all other meshes. By 30 days, this effect had diminished as a significant increase in adhesions together with phagocytosis of the coating was seen for all meshes with layered coatings (Proceed, Parietex Composite and C-Qur. Incorporation was insufficient for all meshes.

CONCLUSION

The absorbable layers of Parietex Composite and C-Qur reduce adhesion formation to intraperitoneal mesh in the short term, but the effect diminishes and phagocytosis of absorbable coatings may contribute to adhesion formation.

Absence of circulating aldosterone attenuates foreign body reaction around surgical sutures

BACKGROUND AND AIMS

Adrenal hormones influence inflammatory and fibrotic activity and thereby are involved in wound-healing process. Any excess as well as any shortage of glucocorticoids leads to a delayed wound healing. Mineralocorticoids like aldosterone have a pro-fibrotic and pro-inflammatory impact; thus, reduction of circulating aldosterone should result in an attenuated inflammatory response to implanted foreign bodies.

MATERIAL AND METHODS

Eighteen rats were bilaterally adrenalectomized and substituted with dexamethasone (12 microg/kg per day) and 1% salt in their drinking water; 22 rats were sham-operated. The surgical suture material was removed after 3 weeks and analyzed for size of granuloma, ratio of collagen type I/III, apoptotic cells (terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling), expression of matrix metalloproteinase (MMP)-2, cyclooxygenase 2, tumor necrosis factor receptor 2 (TNF-R2), cluster of differentiation 68 (CD68), Ki67, and cold shock protein Y box binding protein 1 (YB-1). Cell expression was scored according to Remmele.

RESULTS

All animals developed foreign body granulomas around the sutures. Absence of circulating aldosterone after adrenalectomy (ADX) was associated with smaller granuloma size and a reduced ratio of collagen type I/III. Ki67 and MMP-2 showed the strongest expression in cells of the infiltrate around suture. In adrenalectomized rats, we observed significantly less CD68-positive macrophages and less Ki67-positive cells but no significant differences in the expression of YB-1, TNF-R2, or MMP-2. Looking for correlations and co-expressions of proteins, the number of significant Spearman correlations was reduced in the ADX group compared to controls (one and four, respectively).

CONCLUSION

The absence of circulating aldosterone attenuates inflammatory intensity around suture material. Foreign body granuloma seems to be an appropriate model to study chronic inflammatory process.

Multicentric observational cohort study evaluating a composite mesh with incorporated oxidized regenerated cellulose in laparoscopic ventral hernia repair

BACKGROUND

A variety of newly developed mesh products have recently become available to use inside the peritoneal cavity. This analysis reports the first clinical data evaluating the experience with the use of Proceed mesh in laparoscopic ventral hernia repair.

PATIENTS AND METHODS

During a 6-month period, 114 adult patients underwent a laparoscopic ventral hernia repair using an intra-abdominal placement of a Proceed mesh. The operative procedure was stratified for all centers. Perioperatively, different parameters were evaluated considering the conversion rate to open procedure, complications such as seroma and hematoma, bowel lesions, urinary retention, acute, and chronic pain, mesh infection, and recurrences.

RESULTS

The mean age of the patients was 45 years (range 19-84 years). There were no conversions to open repair and no mortality. Complications included 12 seromas/hematomas (four aspirated), chronic discomfort in two patients, and urinary retention in one patient. There have been four recurrences (3.5%), occurring 3, 4, 4, and 15 months after surgery, respectively. The mean follow-up period was 27 months (range 12-38 months). There have been no documented infections of the mesh.

CONCLUSIONS

This multicentric study documents a favorable experience using large-pore mesh in laparoscopic ventral hernia repair. There were no major complications related to the mesh. Technical advantages considering mesh handling and long-term advantages considering chronic pain might be of interest with the use of this lightweight mesh for minimally invasive ventral hernia repair.

New objective measurement to characterize the porosity of textile implants

The inflammatory and fibrotic intensity of a foreign body reaction largely depends on the porosity of the implanted material. Furthermore, the size of the pore and its geometry define the capability to allow tissue ingrowth. We present an image analysis system, which allows objectifying in two dimensions the pores' structure and geometry of textile fabrics, that are used to reinforce the abdominal wall or pelvic floor. The porosity of the textile is measured at four samples with differences in structure. The porosity decreases markedly if foreign body response is considered, leading to the definition of an "effective porosity". Because of the high stiffness of the polymer fibers the elasticity of textile implants usually result from a deformation of the pores, leading to a marked reduction of the effective porosity if a mechanical stress is applied. Further in vivo studies have to investigate, whether the preservation of a high effective porosity under stress may help to improve biocompatibility of textile implants.

Mesh migration into the esophageal wall after mesh hiatoplasty: comparison of two alloplastic materials

BACKGROUND

Hiatal mesh implantation in the operative treatment of gastroesophageal reflux disease has become an increasing therapy option. Besides clinical results little is known about histological changes in the esophageal wall.

METHODS

Two different meshes [polypropylene (PP), Prolene; polypropylene-polyglecaprone 25 composite (PP-PG), Ultrapro] were placed on the diaphragm circular the esophagus of 20 female rabbits. After three months a swallow with iodine water-soluble contrast medium for functional analysis was performed. After the animals were sacrificed, histopathological evaluation of the foreign-body reaction, the localization of the mesh relating to the esophageal wall was analyzed.

RESULTS

Sixteen rabbits survived the complete observation period of three months. After three months distinctive mesh shrinkage was observed in all animals and meshes had lost up to 50% of their original size before implantation. We found a delayed passage of the fluid into the stomach in all operated animals. There was a significant increased diameter of the outer ring of granulomas in the PP group (76.5 +/- 8.0) compared to the PP-PG group (64 +/- 8.5; p = 0.002). However, we found a mesh migration into the esophageal wall in six out of seven animals (PP) and five out of nine animals (PP-PG), respectively.

CONCLUSION

Experimental data suggest that more knowledge is necessary to assess the optimal size, structure, and position of prosthetic materials for mesh hiatoplasty. The indication for mesh implantation in the hiatal region should be carried out very carefully.

Interposition of Polyglactin Mesh Does Not Prevent Adhesion Formation Between Viscera and Polypropylene Mesh

BACKGROUND

The use of intra-peritoneal polypropylene mesh (PPM) to repair incisional hernia carries the risk of adhesions and damage to the intra-abdominal viscera. Polyglactin 910 mesh (PGM) is advocated to avoid contact between PPM and the intra-abdominal viscera. An experimental study in rats was performed to determine if interposition of a resorbable prosthesis between the PPM and viscera alters biocompatibility, adhesion formation, and herniation.

MATERIALS AND METHODS

A 2- x 3-cm abdominal wall defect was created in 80 rats. Rats were randomly assigned for repair with 2.5- x 3.5-cm PPM (n = 40) or 2.5- x 3.5-cm PPM plus polyglactin 910 mesh (PPM-PGM) (n = 40). The rats were sacrificed at 1, 2, 3, and 6 months (n = 10), and an autopsy was performed to determine herniation and adhesion rates. Mesh-fascia interface was taken for histology.

RESULTS

In the PPM group, 1 rat died before the end of the experiment, and at 6 months one of the 10 rats had a herniation. In the PPM-PGM group, two rats died before the end of the experiment, and two rats had a herniation after 1 month and three rats after 6 months. At 1, 2, and 3 months the adhesion score in the PPM group (median, 3; range, 2-3) did not differ from the score in the PPM-PGM group (median, 3; range, 2-3). Also, at 6 months the adhesion score in the PPM group (median, 2; range, 2-3) did not differ from the score in the PPM-PGM group (median, 3; range, 2-3). At microscopy a capsule was formed around the PP fibers, which matured over months in the PPM group. In the first month after implantation an inflammatory response was seen. Histology was similar in both groups, although in the early PPM-PGM group the inflammatory response was more evident.

CONCLUSION

Interposition of PGM between PPM and viscera does not alter adhesion formation nor influences herniation rate.

Differences in polypropylene shrinkage depending on mesh position in an experimental study

BACKGROUND

Polypropylene (PP) mesh is one of the most frequent materials used in hernia repair. We have experimentally evaluated the shrinkage of PP mesh depending on the place of implantation.

METHODS

In 15 New Zealand rabbits a muscular defect measuring 3 x 3 cm was created in both pararectal sides of the abdominal wall. The defect was repaired using a PP mesh measuring 5 x 3.5 cm that was placed in the right side in the sublay location and in the left side in the onlay location. Five animals were killed on the 30th, 60th, and 90th postoperative days. Macroscopic measurement and microscopic study of the prosthesis-host tissue interfaces were performed.

RESULTS

One rabbit was killed because of severe infection in the onlay mesh. Another 2 infections were tolerated in the onlay mesh side. All the prostheses were integrated in the host tissue at death. In the macroscopic evaluation the mesh areas were reduced by 25.92% on the 30th day, by 28.67% on the 60th day, and by 29.02% on the 90th day. The mesh shrinkage was greater in the onlay group than in the sublay group at the 3 time intervals. More inflammatory leukocyte and mononuclear responses also were seen in the onlay group.

CONCLUSIONS

These observations support the theory of PP mesh shrinkage as a consequence of the incorporation of the biomaterial to the scarring tissue. This shrinkage is significantly more intense if the meshes are placed in the onlay position.