Adhesion Tenacity Research Articles

Epidural Fat Tissue Is More Effective for Scar Prevention Than Conventional Subcutaneous Fat Grafting After Laminectomy in a Mouse Model.

Basic science study. The aim of this study was to examine whether epidural fat tissue (EFT) transplantation can prevent epidural adhesion after laminectomy more efficiently than subcutaneous fat tissue (SFT) transplantation. Epidural adhesion is almost inevitable after laminectomy. Although many materials have been used to prevent adhesion, none has been widely accepted. As EFT is an ectopic fat tissue located on the dura mater and there is no adhesion between EFT and the dura mater, we focused on the efficacy of EFT for adhesion prevention. We examined the differences in histology and gene expression between EFT and SFT of mice. We performed laminectomy at the 10th thoracic level and immediately transplanted EFT or SFT to the dura mater in mice. At 6 weeks after transplantation, we performed histological and gene expression analyses and evaluated the adhesion tenacity. In addition, we examined the characteristic differences between human EFT and SFT. The adipocytes of EFT were significantly smaller than those of SFT in mice and humans. The gene expression of inflammatory cytokine and fibrosis-related factors was significantly higher in SFT than in EFT. At 6 weeks after transplantation, the percentage of the remaining fat area over the dura mater was significantly greater in the EFT group than in SFT group, and the adhesion tenacity score was significantly lower in the EFT group than that in the SFT group. An RNA sequencing analysis revealed 1921 differentially expressed genes (DEGs) between human EFT and SFT, and a Gene Ontology term associated with the inflammatory response was most highly enriched in SFT. EFT has different molecular and histological profiles from SFT and EFT grafting is more effective for epidural adhesion prevention than conventional SFT transplantation after laminectomy in a mouse model.Level of Evidence: N/A.

Adhesiolysis-Related Challenges for Laparoscopic Procedures after Ventral Hernia Repair with Intraperitoneal Mesh.

Background: Laparoscopic procedures in patients with history of abdominal surgery can be challenging due to the unknown risk of postoperative adhesions (POA). The intraperitoneal onlay mesh procedures (IPOM) are frequently used for open or laparoscopic repair for incisional and ventral hernia. The risk of PoA can be increased in these patients, thus, any further laparoscopic exploration might be considered difficult. The aim of our study is to analyze the adhesiolysis-related challenges and complications in patients requiring laparoscopic surgery after IPOM ventral hernia repair. Methods: All the patients who underwent any laparoscopic procedure after open or video-assisted IPOM ventral hernia repair in Ponderas Academic Hospital from May 2011 to December 2018, were retrospectively analyzed. Two trained experts reviewed all video recordings and collected data on surgical history, adhesion location and density, dissection difficulty, interval time to release adhesions from the mesh and complications. Results: Twenty-nine patients were included into the study. There were 17 females, mean age of 58.0 +- 14.5 years, mean BMI of 28.7 +- 7.0 Kg/m2 and a median number of abdominal surgeries of 3/ patient. Risk factors for adhesion formation, other than the mesh itself were found in16 patients. The median time from the last IPOM procedure to the laparoscopic exploration was 26 months and it was related to the hernia repair technique in 21 patients and indicated for other pathologies in 8 patients.Adherences to the mesh were found in the majority of the cases (96%).The mean score of surface adhesion and adhesion tenacity was 4.0 +- 1.7 and 3.0 +- 0.8, respectively. The median time to complete the adhesiolysis to the mesh was 22 minutes. Small bowel was open during the dissection in six patients. Mesh migration was encountered in two. There were three conversions to open surgery and one to robotic surgery. History of peritonitis and septic complications at the last surgery were significantly associated with a higher rate of conversion. One surgical site infection and no mesh infection were encountered. The median postoperative hospital stay was 4 days. The 30-day postoperative mortality was nil. The median postoperative follow-up was 13 months. There are 3 recurrent incisional hernias. Conclusions: The study demonstrates that laparoscopic approach after previous IPOM is feasible but challenging. Adherences to the mesh are expected in the majority of the cases. History of peritonitis, a large number of open abdominal procedures, and septic complication at last surgery correlate with a high difficulty of adhesiolysis.

Mussel-inspired copolymer-coated polypropylene mesh with anti-adhesion efficiency for abdominal wall defect repair.

Polypropylene (PP) meshes are one of the most commonly used prosthesis materials in repairing abdominal wall defects. However, their application is usually limited due to possible serious abdominal adhesions between the mesh and the viscera. Instilling PP meshes with excellent anti-adhesion characteristics is still a formidable challenge. In this work, in order to prevent intestinal adhesion to the PP mesh, an effective method was developed to prepare anti-adhesive PP meshes, which was inspired by mussel adhesive proteins. A functional monomer, namely, dopamine methacrylamide, was first synthesized. Then, it was copolymerized with poly(ethylene glycol) methacrylate on the surface of O2-plasma-treated PP (OPP) meshes to form comb-like copolymer poly[poly(ethylene glycol) methacrylate-co-dopamine methacrylamide] (PEDMA), which was simultaneously grafted in situ on the OPP mesh surface through the catechol group of PEDMA, subsequently yielding an anti-adhesive PP mesh (OPP-g-PEDMA). The properties of PEDMA and OPP-g-PEDMA meshes were characterized by NMR, GPC, TGA, FTIR, XPS, SEM, and water contact angle measurements. NIH-3T3 cells were employed to assess the cytocompatibility of OPP-g-PEDMA in vitro. Furthermore, the rat abdominal wall defect model was used to evaluate the efficacy of adhesion prevention. The results show that OPP-g-PEDMA not only possesses fantastic biocompatibility but also satisfactory anti-adhesion property involving minimal chronic inflammation, as well as lower adhesion formation rate and adhesion tenacity scores (less than 1.0). This type of OPP-g-PEDMA mesh is a promising candidate in effectively preventing peritoneal adhesion during abdominal wall defect repair.

Efficacy of robotic versus open transversus abdominis release in a porcine model.

Transversus abdominis muscle release (TAR) combines retromuscular mesh placement with posterior component separation and muscle release. TAR is usually an open technique for abdominal wall reconstruction; however, several centers have performed this operation robotically and claim better clinical outcomes when compared to open surgery. We sought to compare robotic versus open TAR utilizing a porcine model. Animals were randomized to open versus robotic TAR with mesh placement, survived for 4weeks, then underwent diagnostic laparoscopy to assess adhesive burden and adhesion tenacity. T-peel testing was utilized to assess mesh ingrowth. The primary outcome was adhesive burden; secondary outcomes included mesh incorporation, contraction, and operative time. Nine robotic and eight open TARs were performed. Mean operative time was significantly shorter for the open cases compared to robotic cases (88.6 ± 12.9min versus 228.3 ± 46.2, p < 0.01). Operative time in the robotic arm of the study decreased over time, from 300 to 165min. No difference was seen in the mean adhesion area between the two groups. Adhesion tenacity and mesh flatness were similar. The work required to peel the mesh off surrounding tissue was significantly higher in the open TAR than in the robotic TAR group: 52.6 ± 15.5 and 32.9 ± 10.6mJ/cm2, respectively (p < 0.01). There were no differences in adhesions between the robotic and open approaches, but greater mesh contraction and ingrowth was observed in the open TAR group. Though operative time was longer in the robotic group, time dropped by about 40% from the first case to the last.

Comparative efficacy of Prolene and Prolene-Vicryl composite mesh for experimental ventral hernia repair in dogs.

In this study, efficacy of two hernia mesh implants viz. conventional Prolene and a novel Prolene-Vicryl composite mesh was assessed for experimental ventral hernia repair in dogs. Twelve healthy mongrel dogs were selected and randomly divided into three groups, A, Band C (n=4). In all groups, an experimental laparotomy was performed; thereafter, the posterior rectus sheath and peritoneum were sutured together, while, a 5 × 5 cm defect was created in the rectus muscle belly and anterior rectus sheath. For sublay hernioplasty, the hernia mesh (Prolene: group A; Prolene-Vicryl composite mesh: group B), was implanted over the posterior rectus sheath. In group C (control), mesh was not implanted; instead the laparotomy incision was closed after a herniorrhaphy. Post-operative pain, mesh shrinkage and adhesion formation were assessed as short term complications. Post-operatively, pain at surgical site was significantly less (P<0.001) in group B (composite mesh); mesh shrinkage was also significantly less in group B (21.42%, P<0.05) than in group A (Prolene mesh shrinkage: 58.18%). Group B (composite mesh) also depicted less than 25% adhesions (Mean ± SE: 0.75 ± 0.50 scores, P≤0.013) when assessed on the basis of a Quantitative Modified Diamond scale; a Qualitative Adhesion Tenacity scale also depicted either no adhesions (n=2), or, only flimsy adhesions (n=2) in group B (composite mesh), in contrast to group A (Prolene), which manifested greater adhesion formation and presence of dense adhesions requiring blunt dissection. Conclusively, the Prolene-Vicryl composite mesh proved superior to the Prolene mesh regarding lesser mesh contraction, fewer adhesions and no short-term follow-up complications.

Use of N,O-carboxymethyl chitosan to prevent postsurgical adhesions in a rabbit double uterine horn model: a randomized controlled design.

In previous studies, N,O-carboxymethyl chitosan has been shown to decrease the incidence and intensity of abdominal adhesions. In the present study, adhesions were induced in 220 rabbits using a double uterine horn model. Rabbits were randomized to receive an operation only or an operation+medical chitosan intraperitoneally. Twenty-two rabbits from each group were euthanized at one of five different times (Day 3, 7, 14, 28, or 42), and adhesion formation was given gross and histopathological scores. Reductions were observed in adhesion extent (P=0.0337) and tenacity (P=0.0271) as well as inflammation (P<0.0001) on Day 3 when medical chitosan was applied. Prior to Day 14, fibrosis was less obvious in the medical chitosan group (P< 0.0005). The tenacity scores were significantly lower in the medical chitosan group following Day 14 (P<.05), while the type scores were lower in the medical chitosan group following Day 28 (P<.03). Thus, medical chitosan decreased both the gross and the histopathological scores of the induced adhesions.

Tamoxifen for the prevention of postoperative intra-abdominal adhesions

Postoperative intra-abdominal adhesion (PIAA) is a common complication following abdominal surgeries. Up to now, no practical method or device has been proven to be the gold standard in PIAA formation prevention. This study was designed to evaluate the effects of oral and intraperitoneal tamoxifen citrate on PIAA formation prevention. A total of 48 guinea pigs weighing 300–350 g were included in four groups (12 pigs in each group). Under general anesthesia, laparotomy was performed, and a part of small bowel was abraded using wet gauze so that serosal petechiae developed on the intestinal surface for induction of peritoneal adhesion. In group 1 (control), only this adhesion induction was performed with no treatment. In the second group, 2.5 mg/kg/day tamoxifen citrate was administered by orogastric gavage postoperatively. Group 3 underwent adhesion induction and then intraperitoneal administration of 2.5 mg/kg tamoxifen citrate diluted in 10 ml of aquapura. Group 4, underwent adhesion induction and intraperitoneal administration of 2.5 mg/kg tamoxifen citrate diluted in 10 ml aquapura and then 2.5 mg/kg/day tamoxifen citrate was administered by orogastric gavage postoperatively. Pigs underwent laparotomy on the eighth postoperative day, and grading of adhesions was performed according to the Adhesion Characteristic and Adhesion Tenacity scoring system. Data were analyzed using SPSS for Windows version 16. The control group was significantly different from other groups (p < 0.008), which means usage of tamoxifen (oral or intraperitoneal or both) significantly reduced adhesion formation after laparotomy. Intraperitoneal tamoxifen (group 3) was more effective in prevention of adhesion formation than oral tamoxifen application (group 2; p = 0.006). Also, administration of both oral and intraperitoneal tamoxifen (group 4) reduced adhesions significantly (p = 0.002) in comparison with just oral one (group 2), but it made no difference (p = 0.625) with only intraperitoneal tamoxifen (group 3). This study indicated that tamoxifen significantly reduces PIAAs, and intraperitoneal application is more effective than oral administration. This study shows that preventive effects of intraperitoneal application of tamoxifen will not improve when oral tamoxifen is added postoperatively. More studies with focus on evaluation of probable side effects and also performing clinical trials for evaluating tamoxifen for preventing PIAAs are strongly suggested.

Evaluation of Soft Tissue Attachments to a Novel Intra-abdominal Prosthetic in a Rabbit Model

Laparoscopic ventral hernia repair requires placement of an intraperitoneal prosthetic. Composite mesh types have been developed to address the shortcomings of standard meshes. The authors evaluated the host reaction to intraperitoneal placement of a novel composite material. A comparison of an innovative polypropylene/polylactide composite mesh was made to parietex composite (PCO), Proceed, and DualMesh. Eighteen meshes per group were implanted on intact peritoneum in New Zealand white rabbits. The main outcome measures included the formation of visceral adhesions, adhesion tenacity, tensiometric measurements, and histological analysis. Evaluations of adhesions were made at 1, 4, and 16 weeks using a 2-mm minilaparoscopy. There were no significant differences in the mean adhesion scores between the composite mesh types at week 1 (P = .15) and week 16 (P = .06). At 4 weeks, PCO had significantly fewer adhesions when compared with the other 3 mesh types (P = .02). Adhesion tenacity was also equivalent within the group at 16 weeks (P = .06). Tensiometry and histological analysis revealed no statistically significant differences between the mesh types. Four different composite mesh types had equivalent intra-abdominal soft tissue attachments in a rabbit model after a 16-week implantation period. PCO demonstrated the lowest mean adhesion score of each mesh type. Each mesh exhibited equivalent stiffness and energy to failure after explantation. The 4 composite mesh types demonstrated the successful formation of a neoperitoneum and comparable host biocompatibility as evidenced by similar degrees of inflammation.

Polytetrafluoroethylene Membrane (Gore Preclude Vessel Guard) for Vessel Protection During Anterior Lumbar Surgery

The effects of implanting a polytetrafluoroethylene (PTFE) membrane (Gore Preclude Vessel Guard, WL Gore and Associates, Flagstaff, AZ) during anterior lumbar surgery were studied in a pig model. We investigated whether placement of a PTFE membrane between the great vessels and anterior surface of the lumbar spine would minimize adhesions. Anterior lumbar procedures continue to increase, as do revision operations. Anterior approaches remain challenging, however, because of the considerable risk of vascular injury. The risk is especially high with revision procedures because of the presence of adhesions that can hinder visualization and mobilization of vessels. Use of an anti-adhesion barrier may decrease the rate of vascular complications associated with revision surgery. Three spinal levels in 3 pigs were subjected to either discectomy, creation of a hole in the disc, or disc exposure only. In 5 of the 9 levels, a PTFE membrane was then implanted over the disc; the other 4 levels were controls. Spine segments were obtained 12 weeks later, and the tenacity of adhesions (scale of 0 to 4) and percentage of disc space covered by adhesions were assessed. The specimens were also studied histologically. Mean values for adhesion tenacity were 2.75 for control spinal levels and 0.4 for levels with a PTFE membrane (P=0.008). Mean values for adhesion coverage were 81% for control disc spaces and 15% for spaces with a PTFE membrane (P=0.008). Histologic studies showed minimal adhesions, lack of an inflammatory reaction, and vascularized connective tissue between PTFE membranes and the vena cava. In a pig model, implantation of a PTFE membrane during anterior lumbar surgery decreased the tenacity and amount of adhesions observed at necropsy. Studies of the efficacy and safety of the PTFE membrane in clinical anterior lumbar surgery are warranted.

Comparison of contracture, adhesion, tissue ingrowth, and histologic response characteristics of permanent and absorbable barrier meshes in a porcine model of laparoscopic ventral hernia repair

The objective of this study was to determine the mesh contracture, adhesion, tissue ingrowth, and histologic characteristics of a novel absorbable barrier mesh (Ventrio™ ST Hernia Patch) compared to existing permanent (Ventrio™ Hernia Patch) and absorbable barrier meshes (Sepramesh™ IP Composite and PROCEED™ Surgical Mesh). Standard laparoscopic technique was utilized to bilaterally implant meshes in 20 female Yorkshire pigs (n = 5 pigs/group). Meshes were fixated to the intact peritoneum with SorbaFix™ absorbable fixation devices. Mesh contracture, adhesion coverage, and adhesion tenacity were evaluated after 4 weeks. T-Peel testing and hematoxylin and eosin (H&E) staining were utilized to assess tissue ingrowth and host response. A significantly greater percent area contracture was demonstrated for PROCEED™ (26.9%) compared to Ventrio™ ST (8.8%), Ventrio™ (14.5%) and Sepramesh™ (9.2%). Ventrio™ ST demonstrated similar adhesion area, tenacity, and tissue ingrowth compared to all other meshes. Histological scoring revealed a comparable host inflammatory response for all meshes, with a few exceptions. A greater number of giant cells were observed in Ventrio™ ST and Sepramesh™ near the multifilament polyglycolic acid (PGA) fibers; a greater number of macrophages were observed in PROCEED™ compared to Ventrio™; and a greater number of neutrophils were observed in PROCEED™, compared to Sepramesh™ (P < 0.05). Focal areas of hemorrhage were also observed on the visceral surface of PROCEED™. Ventrio™ ST Hernia Patch demonstrated comparable contracture, adhesion, tissue ingrowth, and histologic characteristics compared to existing permanent and absorbable barrier meshes. Host inflammatory and fibrotic responses for all four meshes were minimal and representative of a biocompatible response.

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

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. 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. 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. 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.

Evaluation of intraperitoneal placement of absorbable and nonabsorbable barrier coated mesh secured with fibrin sealant in a New Zealand white rabbit model

This study aimed to evaluate the acute and chronic fixation strength of fibrin sealant (FS) as an alternative method of fixation for laparoscopic ventral hernia repair (LVHR). Representative mesh types for LVHR included one nonabsorbable barrier mesh (Composix) and three absorbable barrier meshes (Sepramesh, Proceed, and Parietex composite). Macroporous polypropylene mesh (Prolite Ultra) served as the control mesh. Three methods of fixation were used, namely, 0-polypropylene suture+FS (ARTISS 4 IU), FS alone (ARTISS), and tacks alone, to secure 3×4-cm pieces of mesh (10 of each combination) to the peritoneal surface of New Zealand white rabbit abdominal wall. After 2 h of incubation at 37 °C, specimens underwent acute testing. Subsequently, a chronic phase was completed using the aforementioned fixation methods (10 of each combination), in which two 4×4-cm pieces of mesh were secured intraperitoneally in each of 75 New Zealand white rabbits, which survived 8 weeks until they were sacrificed. A transparent grid overlay was used to measure the mesh and adhesion area. Adhesion tenacity was characterized using the Garrard adhesion scale. In both the acute and chronic samples, a 3×3-cm area of mesh-tissue interface underwent lap shear testing at a rate of 0.42 mm/s using a tensiometer (Instron 5542). The maximum load sustained by the mesh-tissue construct was recorded as the acute fixation strength in newtons (N). Data are given as means±standard error of the mean. Statistical significance (p<0.05) was determined using a one-way analysis of variance (ANOVA) with Fisher's least significant difference (LSD) posttest or a nonparametric Kruskal-Wallis test (adhesion scores). The acute fixation strength was significantly greater for all the meshes secured with either suture+FS or tacks alone than for FS alone (p<0.001 for all comparisons). All the meshes except Proceed demonstrated greater acute fixation strength with suture+FS than with tacks alone (p≤0.016). Composix achieved greater acute fixation with suture+FS than all the other meshes (p≤0.022). Acute fixation with suture + FS was greater for Parietex Composite and ProLite Ultra than for Proceed (p≤0.015). When the animals were sacrificed, 48 of 50 meshes fixed with FS alone were insufficiently affixed to the abdominal wall, which may have resulted in hernia recurrence in a hernia model. The chronic fixation strength was greater for all the mesh types with either suture+FS or tacks only than with FS alone (p≤0.0005). The chronic fixation strength was greater with suture+FS than with tacks for Proceed and ProLite Ultra (p≤0.013). Neither mesh area nor adhesion tenacity differed significantly with any mesh/fixation method combination. In a chronic rabbit model of LVHR, fixation strength with FS alone was inadequate for selected nonabsorbable and absorbable barrier-coated meshes. The acute and chronic fixation strengths of suture+FS were equivalent or superior to the fixation strength of tacks alone. Using a combination of suture and FS for mesh fixation in LVHR may provide adequate fixation while decreasing postoperative pain due to spiral titanium tacks. In this preclinical series, mesh secured to the peritoneal surface by FS alone may have led to early recurrence.

Prospective evaluation of adhesion characteristics to intraperitoneal mesh and adhesiolysis-related complications during laparoscopic re-exploration after prior ventral hernia repair

The purpose of this study was to characterize the adhesion characteristics of absorbable- and nonabsorbable-barrier-coated meshes and to report adhesiolysis-related complications during laparoscopic re-exploration after prior ventral hernia repair. Under an IRB-approved protocol, patients undergoing laparoscopic re-exploration after prior intraperitoneal mesh placement were prospectively graded intraoperatively for adhesion tenacity (0-4), adhesion surface area (0 = 0%, 10 = 100%), and ratio of adhesiolysis time to mesh surface area (min/cm(2)). Adhesiolysis-related complications were also recorded. Data are given as mean ± SD. Statistical significance (P < 0.05) was determined using the t test and Fisher's exact test. From March 2006 to March 2009, 69 patients underwent laparoscopic surgery after prior intraperitoneal mesh placement for ventral hernia repair. Previous meshes were absorbable-barrier-coated mesh (n = 18), permanent-barrier composite mesh [Composix® (n = 17)], permanent-barrier noncomposite mesh [DualMesh® (n = 14)], uncoated polypropylene mesh (n = 12), and biologic mesh (n = 8). Indications for laparoscopic re-exploration were recurrent ventral hernia (n = 58), chronic pain (n = 3), cholecystectomy (n = 3), parastomal hernia (n = 2), small bowel obstruction (n = 1), nephrectomy (n = 1), and Nissen fundoplication (n = 1). Adhesions to DualMesh were less tenacious (P < 0.05) compared to all other meshes. Surface area of adhesions to DualMesh were less (P < 0.05) than to Composix and to uncoated polypropylene mesh, but not to absorbable-barrier-coated and biologic meshes. Adhesiolysis time:mesh surface area was less (P < 0.05) for DualMesh compared to Composix, uncoated polypropylene, and biologic mesh, but not to absorbable-barrier-coated mesh. Adhesiolysis-related complications occurred in two (16.7%) (P = ns) patients with uncoated polypropylene mesh, one cystotomy and one enterotomy; both were repaired laparoscopically. There were two (16.7%) (P = ns) conversions to an open procedure: one converted patient had Composix (6.7%) and one had absorbable-barrier-coated mesh (5.9%). There were no adhesiolysis-related complications with these meshes. There were no adhesiolysis-related complications or conversions to open in the DualMesh or biologic mesh groups. Adhesion characteristics of mesh placed intraperitoneally and adhesiolysis-related complications during laparoscopic re-exploration after ventral hernia repair are associated with unique properties of the mesh and/or barrier.

Addition of nimesulide to small intestinal submucosa biomaterial inhibits postsurgical adhesiogenesis in rats

Adhesion formation is a common complication in abdominal surgery with incidence as high as 93% and small bowel obstruction a common complication. Because the extracellular matrix material, small intestinal submucosa (SIS), is commonly used in various surgical procedures, methods to inhibit adhesiogenesis are of great interest. This study was undertaken to determine if incorporation of nimesulide (NM), a selective cyclooxygenase (COX)-2 inhibitor, could reduce the extent and tenacity of intraabdominal adhesion formation associated with SIS implantation. Female Sprague-Dawley rats underwent a cecal abrasion surgical procedure to induce adhesiogenesis. Rats were either left untreated or treated by direct application over the injured cecum with polypropylene mesh (PPM); SIS; SIS containing a low dose of NM; or SIS containing a high dose of NM. Rats were euthanized 21 days later, and adhesion extent and tenacity were evaluated using standard scales (0 = minimal adhesiogenesis; 4 = severe adhesiogenesis). Addition of NM to SIS resulted in a significant (p < 0.05) reduction in adhesion extent and in a similar reduction in adhesion tenacity for SIS containing a low dose of NM. Adhesions typically extended from the abraded cecal surface to the body wall and were characterized histologically by fibrous tissue adherent to the cecal wall. In conclusion, addition of the nonsteroidal anti-inflammatory, COX-2 selective drug, NM, to SIS attenuates adhesion extent and tenacity when compared with surgical placement of SIS or PPM alone.

Non–Cross-Linked Porcine Acellular Dermal Matrices for Abdominal Wall Reconstruction

Non-cross-linked porcine acellular dermal matrices have been used clinically for abdominal wall repair; however, their biologic and mechanical properties and propensity to form visceral adhesions have not been studied. The authors hypothesized that their use would result in fewer, weaker visceral adhesions than polypropylene mesh when used to repair ventral hernias and form a strong interface with the surrounding musculofascia. Thirty-four guinea pigs underwent inlay repair of surgically created ventral hernias using polypropylene mesh, porcine acellular dermal matrix, or a composite of the two. The animals were killed at 4 weeks, and the adhesion tenacity grade and surface area of the repair site involved by adhesions were measured. Sections of the repair sites, including the implant-musculofascia interface, underwent histologic analysis and uniaxial mechanical testing. The incidence of bowel adhesions to the repair site was significantly lower with the dermal matrix (8 percent, p < 0.01) and the matrix/mesh combination (0 percent, p < 0.001) than with polypropylene mesh alone (70 percent). The repairs made with the matrix or the matrix/mesh combination, compared with the polypropylene mesh repairs, had significantly lower mean adhesion surface areas [12.8 percent (p < 0.001), 9.2 percent (p < 0.001), and 79.9 percent] and grades [0.6 (p < 0.001), 0.6 (p < 0.001), and 2.9]. The dermal matrix underwent robust cellular and vascular infiltration. The ultimate tensile strength at the implant-musculofascia interface was similar in all groups. Porcine acellular dermal matrix becomes incorporated into the host tissue and causes fewer adhesions to repair sites than does polypropylene mesh, with similar implant-musculofascia interface strength. It also inhibits adhesions to adjacent dermal matrix in the combination repairs. It has distinct advantages over polypropylene mesh for complex abdominal wall repairs, particularly when material placement directly over bowel is unavoidable.

Implantation of amniotic membrane to reduce postlaminectomy epidural adhesions

Postlaminectomy epidural adhesion is implicated as a main cause of "failed back surgery syndrome" and associated with increased risk of complications during revision surgery. Various materials acting as mechanical barriers to reduce fibroblasts infiltration into epidural space have met with limited success. In present research, amniotic membrane (AM) was studied to investigate its effects on reducing epidural scar adhesion after laminectomy in a canine model. Laminectomy sites were created at L-1, L-3, L-5, and L-7 levels in 24 adult mongrel dogs. Freeze dried AM (FAM), cross-linked AM (CAM), and autologous free fat (AFF) were implanted, respectively, at a randomly assigned site in each dog with the remaining untreated site serving as internal control. The animals were sacrificed at 1, 6, and 12 weeks postoperatively. Then, gross pathologic observation including scar amount and adhesion tenacity, qualitative histology evaluation, and quantitative histology analysis were compared. Gross observation demonstrated that scar amount and adhesion tenacity of CAM group were significantly lower in comparison with those of FAM and non-treatment groups. A white, slightly vascularized CAM layer covered the dura mater without tenacious scar adhesion. The histology analysis also indicated reduced fibroblasts infiltration and consequent epidural fibrosis, which were similar to the results of AFF group. In conclusion, the CAM is effective in reducing epidural fibrosis and scar adhesion after laminectomy in canine model. It is a promising biomaterial for future clinical applications.

Prospective Evaluation of Adhesion Formation and Shrinkage of Intra-Abdominal Prosthetics in a Rabbit Model

Laparoscopic ventral hernia repair requires an intraperitoneal prosthetic; however, these materials are not without consequences. We evaluated host reaction to intraperitoneal placement of various prosthetics and the functional outcomes in an animal model. Mesh (n = 15 per mesh type) was implanted on intact peritoneum in New Zealand white rabbits. The mesh types included ePTFE (DualMesh), ePTFE and polypropylene (Composix), polypropylene and oxidized regenerated cellulose (Proceed), and polypropylene (Marlex). Adhesion formation was evaluated at 1, 4, 8, and 16 weeks using 2-mm mini-laparoscopy. Adhesion area, adhesion tenacity, prosthetic shrinkage, and compliance were evaluated after mesh explantation at 16 weeks. DualMesh had significantly less adhesions than Proceed, Composix, or Marlex at 1, 4, 8, and 16 weeks (P < 0.0001). Marlex had significantly more adhesions than other meshes at each time point (P < 0.0001). There were no statistically significant differences in adhesions between Proceed and Composix meshes. After mesh explantation, the mean area of adhesions for Proceed (4.6%) was less than for Marlex (21.7%; P = 0.001). The adhesions to Marlex were statistically more tenacious than the DualMesh and Composix groups. Overall prosthetic shrinkage was statistically greater for DualMesh (34.7%) than for the remaining mesh types (P < 0.01). Mesh compliance was similar between the groups. Prosthetic materials demonstrate a wide variety of characteristics when placed inside the abdomen. Marlex formed more adhesions with greater tenacity than the other mesh types. DualMesh resulted in minimal adhesions, but it shrank more than the other mesh types. Each prosthetic generates a varied host reaction. Better understanding of these reactions can allow a suitable prosthetic to be chosen for a given patient in clinical practice.

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

The purpose of this study is to evaluate fixation methods for polytetrafluoroethylene (ePTFE) mesh with an in vivo model of laparoscopic ventral hernia repair. In 40 New Zealand white rabbits, a 4 x 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. 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. 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.

A randomized, prospective, controlled, multicenter clinical trial of a sprayable, site-specific adhesion barrier system in patients undergoing myomectomy

Objective To assess the safety and effectiveness of a sprayable, site-specific adhesion barrier system (SprayGel; Confluent Surgical, Waltham, MA) for reduction of adhesion formation. Design Prospective, randomized, controlled phase III trial. Setting University clinic (Kiel, Germany) and private clinic (Bordeaux, France). Patient(s) Sixty-six women aged 34.9 years (range, 23–52 years) undergoing laparoscopic or open uterine myomectomy, enrolled over a 15-month period. Intervention(s) Patients were randomized to receive either optimal surgical treatment plus adhesion barrier or optimal surgical treatment alone, followed by second-look laparoscopy. Main outcome measure(s) Initial and second-look laparoscopy procedures were assessed for incidence, extent, and severity of adhesions; all patients were followed for safety analysis. Result(s) When compared with initial surgery, the mean adhesion tenacity score of adhesions seen at second-look laparoscopy was significantly reduced in treatment patients compared with control patients (0.6 vs. 1.7, a 64.7% reduction). Mean adhesion extent score at second-look laparoscopy compared with initial surgery was 4.5 cm 2 vs. 7.2 cm 2, mean adhesion incidence score was 0.64 vs. 1.22. Of 64 patients, 40 (62.5%) returned for second-look laparoscopy. Conclusion(s) This adhesion barrier was safe, well tolerated, and demonstrated efficacy in a population of patients known to be at risk for adhesion formation. There were no adverse effects attributable to the product and no patients in whom it could not be applied.

Morphologic study of three collagen materials for body wall repair

Background The search for ideal prostheses for body wall repair continues. Synthetic materials such as polypropylene mesh (PPM) are associated with healing complications. A porcine-derived collagen-based material (CBM), small intestinal submucosa (SIS), has been studied for body wall repair. Renal capsule matrix (RCM) and urinary bladder submucosa (UBS) are CBMs not previously evaluated in this application. This is the first implant study using RCM. Materials and methods Full-thickness muscle/fascia ventral abdominal wall defects were repaired with SIS, RCM, UBS, and PPM in rats with omentum and omentectomy. A random complete block design was used to allot implant type to each of 96 rats. Healing was evaluated at 4 and 8 weeks. Adhesion tenacity and surface area were scored. Implant site dimensions were measured at implantation and necropsy. Inflammation, vascularization, and fibrosis were histopathologically scored. Data were compared by analysis of variance ( P < 0.05). Results PPM produced a granulomatous foreign body response in contrast to the organized healing of CBM implants. CBM mean scores were lower than PPM scores for adhesion tenacity, surface area, and inflammation at each follow-up time for rats with omentums ( P < 0.02). The CBMs had less tenacity and inflammation than PPM at each follow-up time in omentectomy groups ( P < 0.008). Wound contraction was greater for PPM ( P < 0.0001) for all rats. Conclusions RCM and UBS were similar to SIS invoking reduced inflammation, adhesion, and contraction compared to PPM. The fibrotic response to PPM was unique and more intense compared to CBMs. These CBM implants appear morphologically acceptable and warrant continued investigation.