Influence of implantation interval on the long-term biocompatibility of surgical mesh

Prediction of successful revision surgery for mesh-related complaints after inguinal hernia and pelvic organ prolapse repair

PURPOSE

With this retrospective case series, we aim to identify predictors for reduction of pain after mesh revision surgery in patients operated for inguinal hernia or pelvic organ prolapse with a polypropylene implant. Identifying these predictors may aid surgeons to counsel patients and select appropriate candidates for mesh revision surgery.

METHODS

Clinical records before and after mesh revision surgery from 221 patients with chronic postoperative inguinal pain (CPIP) and 59 patients with pain after pelvic organ prolapse (POP) surgery were collected at two experienced tertiary referral centers. Primary outcome was patient reported improvement of pain after revision surgery. A multivariable logistic regression model was used to specify predictors for pain reduction.

RESULTS

The multivariable logistic regression was performed for each patient group separately. Patients with CPIP had higher chances of improvement of pain when time between mesh placement and mesh revision surgery was longer, with an OR of 1.19 per year. A turning point in chances of risks and benefits was demonstrated at 70 months, with improved outcomes for patients with revision surgery ≥ 70 months (OR 2.86). For POP patients, no statistically significant predictors for reduction of pain after (partial) removal surgery could be identified.

CONCLUSION

A longer duration of at least 70 months between implantation of inguinal mesh and revision surgery seems to give a higher chance on improvement of pain. Caregivers should not avoid surgery based on a longer duration of symptoms when an association between symptoms and the location of the mesh is found.

Different cellular and immunohistochemical abdominal wall cicatrization parameters evaluation in comparison with sublay, onlay, and ipom technique in an experimental rat model

PURPOSE

Incisional hernia (IH) occurs when there is a partial or complete solution of continuity of a fascia previously incised. Systematic reviews demonstrate that surgical treatment of IHs with the use of meshes are approximately 16%. Meta-analyses have demonstrated the superiority of mesh placement using sublay technique, but without a pathophysiological explanation. Thus, we aim to evaluate the different techniques of mesh positioning in an experimental model.

METHODS

Fifty rats were distributed into five groups; control; simulation (SM)-submitted to laparotomy only; onlay-the mesh was positioned in onlay fashion; retromuscular (SL)-the mesh was positioned in a sublay fashion; intraperitoneal (IPOM)-positioning of the mesh adjacent to the transversalis fascia, inside the cavity. After 60 days, adhesions, tensiometry, histology, and immunohistochemistry were addressed.

RESULTS

The IPOM group had the most adhesions, together with the SL group, with significantly relevant results. The SL group had higher values of tensiometric evaluation, while the IPOM group had the lowest mean in the tensiometry evaluation, being even lower than the SM group. Regarding histological and immunohistochemical findings, the SL group had a higher pixel number count compared to the groups, with statistical significance, in addition to higher expression of polymorphonuclear infiltrate and CD68 markers.

CONCLUSION

The mesh positioning in sublay compartment is associated with the development of more pronounce minimum tensile force required for detaching the surrounding abdominal wall tissues it was incorporated. The intensity of these findings correlates to the different histological and immunohistochemical profiles observed following each repair, since SL group was characterized by a higher proportion of collagen, inflammatory, and reparative elements. Characterizing these pro-healing elements and its counterparts will allow the development of new therapeutic tools which could be added to the still far-from-ideal current therapeutic options for IH treatment.

A Cell-free Biodegradable Synthetic Artificial Ligament for the Reconstruction of Anterior Cruciate Ligament in a Rat Model

Traditional Anterior Cruciate Ligament (ACL) reconstruction is commonly performed using an allograft or autograft and possesses limitations such as donor site morbidity, decreased range of motion, and potential infection. However, a biodegradable synthetic graft could greatly assist in the prevention of such restrictions after ACL reconstruction. In this study, artificial grafts were generated using "wet" and "dry" electrospinning processes with a biodegradable elastomer, poly (ester urethane) urea (PEUU), and were evaluated in vitro and in vivo in a rat model. Four groups were established: (1) Wet PEUU artificial ligament, (2) Dry PEUU artificial ligament, (3) Dry polycaprolactone artificial ligament (PCL), and (4) autologous flexor digitorum longus tendon graft. Eight weeks after surgery, the in vivo tensile strength of wet PEUU ligaments had significantly increased compared to the other synthetic ligaments. These results aligned with increased infiltration of host cells and decreased inflammation within the wet PEUU grafts. In contrast, very little cellular infiltration was observed in PCL and dry PEUU grafts. Micro-computed tomography analysis performed at 4 and 8 weeks postoperatively revealed significantly smaller bone tunnels in the tendon autograft and wet PEUU groups. The Wet PEUU grafts served as an adequate functioning material and allowed for the creation of tissues that closely resembled the ACL.

Sublay repair results in superior mesh incorporation and histological fibrogenesis in comparison to onlay and primary suture in an experimental rat model

PURPOSE

To compare adhesion scores, repair strength and histological findings among sublay, onlay and primary repair incisional hernioplasty techniques. Surgical repairs were employed directly on healthy animals, without previous hernia induction, to avoid confounding factors related to hernia development.

METHODS

Forty Wistar rats were divided into four groups, control, simulation, onlay and sublay. After 42 days, adhesion intensity, tensile strength of the abdominal wall and anatomopathological histological substrate were compared.

RESULTS

SL group presented greater adhesion scores (p < 0.0001), higher tensiometric (p < 0.0001), and was characterized by more histiocytes, mononuclear cells, macrovacuolar granulomas and type I collagen on histological analysis. Pearson correlation between adhesions and tensiometry, and between tensiometry and neocollagenization showed a strong positive association (r = 0.8905 and 0.6757, respectively in SL group, p < 0.05).

CONCLUSION

Mesh positioning in sublay compartment was followed by increased adhesion development and provides a stronger mesh-tissue attachment, in addition, resulted in a different histological profile of the inflammation/repair substrate. The intensity of these findings was directly correlated, suggesting they could be the result of a common biological phenomenon. Our findings indicate that mesh placement following the retromuscular technique generates a superior repair response, and give clues to a better understanding of the superiority of sublay repair in achieving lower recurrence rates. Characterization of the cellular and molecular elements responsible for the superiority of this technique is in our view an essential prerequisite aiming for improvements in the therapeutic options for the treatment of this disease.

Polyvinylidene Fluoride Alters Inflammatory Responses by Activation-induced Cell Death in Macrophages

Carbon nanotubes (CNTs) are nanomaterials that have been employed in generating diverse materials. We previously reported that CNTs induce cell death in macrophages, possibly via asbestosis. Therefore, we generated CNT-attached polyvinylidene fluoride (PVDF), which is an established polymer in membrane technology, and then examined whether CNT-attached PVDF is immunologically safe for medical purposes compared to CNT alone. To test this, we treated RAW 264.7 murine macrophages (RAW cells) with CNT-attached PVDF and analyzed the production of nitric oxide (NO), a potent proinflammatory mediator, in these cells. RAW cells treated with CNT-attached PVDF showed reduced NO production in response to lipopolysaccharide. However, the same treatment also decreased the cell number suggesting that this treatment can alter the homeostasis of RAW cells. Although cell cycle of RAW cells was increased by PVDF treatment with or without CNTs, apoptosis was enhanced in these cells. Taken together, these results indicate that PVDF with or without CNTs modulates inflammatory responses possibly due to activation-induced cell death in macrophages.

Histological response to platelet-rich plasma added to polypropylene mesh implemented in rabbits

Introduction:

The platelet-rich plasma (PRP) is part of a set of biotechnologies, providing some growth factors that promote repair of different tissues. The polypropylene meshes (PPM) are applied in the correction of abdominal defects, pelvic floor and urinary incontinence, however, they induce many significant complications, as a result of an inappropriate inflammatory response.

Purpose:

To investigate the changes caused by PRP associated with the implantation of PPM in the abdomen of female rabbits, in the production of collagen I and III and the inflammatory infiltrate (ININ).

Materials and Methods:

We performed implant meshes with and without PRP in adult rabbits (n=30) and euthanasia at 7, 30 and 90 days. Two plates were prepared from each animal and analyzed in five different fields. The ININ was evaluated by quantification of inflammatory cells using hematoxylin-eosin and the collagen by Sirius red method. The results were analyzed applying the Wilcoxon, Kruskal-Wallis, Junckheere and Friedmann tests.

Results:

There was a significant difference in the number of inflammatory cells between the groups with and without PRP (p=0.01) at 90 days. There was increased production of collagen I, III and total with the use of PRP, at seven days.

Conclusion:

The PPM coating with PRP was associated with increased ININ at the implant area, and an increasing trend during the process of tissue repair. The PPM coated with PRP was related to increased concentration of collagen I, collagen III and the concentration of total collagen increased after seven days of implantation.

Long-term retromuscular and intraperitoneal mesh size changes within a randomized controlled trial on incisional hernia repair, including a review of the literature

Abstract

Purpose Ingrowth of fibroblasts in a polypropylene mesh may cause contraction and a later recurrence. We assessed mesh contraction in intraabdominal and retromuscular implantation after incisional hernia repair.

Methods

A cohort of patients within an RCT on laparoscopic (LHR) versus open hernia repair (OHR) had their mesh borders marked with metal clips. X-ray was performed on postoperative day 1 and after 1 year. Total length, width, and dislocation were measured. A tacker fixated large-pore polypropylene mesh was used in LHR, and a retromuscular small-pore heavy-weight mesh was sutured to the midline in OHR. Patient’s pain was assessed before surgery and after 1 year.

Results

For analysis 37/47 patients remained: 20 LHR and 17 OHR. Hernia defect area was median 41 cm² in LHR and 25 cm² in OHR (p < 0.140). Implanted mesh size was 300 cm² for LHR and 240 cm² for OHR (p < 0.341). After 1 year the mesh area decreased by 4.4% and 0.5% in LHR and OHR, respectively (p < 0.063). Longitudinal distance decreased by 2.8% in LHR and by 2.6% in OHR (p < 0.269). Transverse distance decreased by 1.6% in LHR but increased by 3.1% in OHR (p < 0.005). Dislocation was seen in four LHR and one OHR. Two recurrent and one port-site hernia were diagnosed after LHR. Measurements between observers were identical in 58% and consensus was made in the remainder. Pain was not correlated to mesh area change.

Conclusions

Mesh contraction after 1 year is not a clinical issue for an intraperitoneal large-pore mesh or a retromuscular small-pore mesh. It is not correlated to postoperative pain.

Evaluation of a fully absorbable poly-4-hydroxybutyrate/absorbable barrier composite mesh in a porcine model of ventral hernia repair

Background

The objective of this study was to evaluate the mechanical and histological properties of a fully absorbable poly-4-hydroxybutyrate/absorbable barrier composite mesh (Phasix™ ST) compared to partially absorbable (Ventralight™ ST), fully absorbable (Phasix™), and biologically derived (Strattice™) meshes in a porcine model of ventral hernia repair.

Methods

Bilateral abdominal surgical defects were created in twenty-four Yucatan pigs, repaired with intraperitoneal (Phasix™ ST, Ventralight™ ST) or retromuscular (Phasix™, Strattice™) mesh, and evaluated at 12 and 24 weeks (n = 6 mesh/group/time point).

Results

Prior to implantation, Strattice™ demonstrated significantly higher (p < 0.001) strength (636.6 ± 192.1 N) compared to Ventralight™ ST (324.3 ± 37.1 N), Phasix™ ST (206.9 ± 11.3 N), and Phasix™ (200.6 ± 25.2 N). At 12 and 24 weeks, mesh/repair strength was significantly greater than NAW (p < 0.01 in all cases), and no significant changes in strength were observed for any meshes between 12 and 24 weeks (p > 0.05). Phasix™ mesh/repair strength was significantly greater than Strattice™ (p < 0.001) at 12 and 24 weeks, and Ventralight™ ST mesh/repair strength was significantly greater than Phasix™ ST mesh (p < 0.05) at 24 weeks. At 12 and 24 weeks, Phasix™ ST and Ventralight™ ST were associated with mild inflammation and minimal–mild fibrosis/neovascularization, with no significant differences between groups. At both time points, Phasix™ was associated with minimal–mild inflammation/fibrosis and mild neovascularization. Strattice™ was associated with minimal inflammation/fibrosis, with minimal neovascularization at 12 weeks, which increased to mild by 24 weeks. Strattice™ exhibited significantly less neovascularization than Phasix™ at 12 weeks and significantly greater inflammation at 24 weeks due to remodeling.

Conclusions

Phasix™ ST demonstrated mechanical and histological properties comparable to partially absorbable (Ventralight™ ST) and fully resorbable (Phasix™) meshes at 12 and 24 weeks in this model. Data also suggest that fully absorbable meshes with longer-term resorption profiles may provide improved mechanical and histological properties compared to biologically derived scaffolds.

Clinical Implantation with the novel D-13 prosthesis for inguinal hernioplasty: A retrospective cohort study

INTRODUCTION

Using a mesh to repair inguinal hernias is now a standard procedure that is widely accepted as superior to primary suture repair. Although a variety of meshes are available, individual meshes may have their own unattractive features. This retrospective study examines the efficacy of our originally designed D-13 prosthesis, which is used in patients with inguinal hernias.

METHODS

A total of 305 patients who underwent a herniorrhaphy between January 2009 and March 2011 were included in this study. The recurrent rate, chronic pain and feeling of a foreign body were examined at a 3-year follow-up. The D-13 prosthesis, made from clear polypropylene monofilament mesh, was originally designed by the first author of this study and constructed with the upper and lower pieces of polypropylene mesh having different shapes and sizes. Both pieces are linked together by a connector.

RESULTS

The mesh is well tolerated. At a 3-year follow-up, only two patients had a foreign body sensation at the operative site, and three patients had recurrent hernias.

CONCLUSION

The unique design of the D-13 prosthesis with two pieces of mesh provided encouraging long-term outcome for hernia recurrence, chronic pain and the feeling of a foreign body.

Characterisation of the cellular infiltrate in the foreign body granuloma of textile meshes with its impact on collagen deposition

PURPOSE

As part of the foreign body reaction, mesh filaments are surrounded by an infiltrate of inflammatory cells. Though macrophages are considered as being predominant, little is known about the origin of other cells.

METHODS

On 55 meshes explanted from humans, we characterised the cells in the inflammatory infiltrate of the granuloma by immunohistochemistry using 10 cellular markers: CD3+ lymphocytes, CD4+ T helper cells, CD8+ cytotoxic T cells, CD20+ B lymphocytes, CD34+ stem cells, CD45R0+ leucocytes, CD68+ macrophages, Mib1 for proliferation, Vimentin for mesenchymal origin, and Desmin for myocytes. Collagen deposits were analysed after staining with Sirius Red.

RESULTS

More than 80 % of the cells in the infiltrate showed a positive expression of CD68, CD8, CD45R0 and Vimentin. CD4 and Desmin were seen in 30-80 % of the cells, unaffected by material or time. A score summarising the expression of all markers positively correlated significantly with an increased percentage of collagen type III (green) in the mesh wound. The analysis of collagen deposits was only affected to a small degree by size of area for investigation.

CONCLUSIONS

At the vicinity of the mesh filaments, the accumulated inflammatory cells represent a mixture of cells of various origins. The high expression of at least four markers requires co-expression of different surface markers and thus confirms the existence of multiple transition forms instead of dominance of just macrophages. This offers new options for interventions to attenuate the inflammatory reaction of mesh implants.

In vitro and in vivo characterization of a fully resorbable and composite surgical mesh

Fully resorbable and composite synthetic meshes are intended to provide advantages over nonabsorbable synthetic meshes, such as minimization of visceral adhesions and improved biocompatibility, but the inflammatory response to these materials has not previously been fully characterized. We compared resorbable and composite synthetic meshes using in vitro characterization and evaluated the host response in a nonhuman primate acute abdominal wall defect. After a 2-week in vitro incubation, resorbable synthetic mesh mechanical strength decreased to 0.12 ± 0.09 N (0.25% of initial strength), which preceded acidification and a fractured morphology at 1 month. The composite synthetic mesh strength decreased to 10.0 ± 3.2 N (41.1% of initial strength), coincident with morphological changes. In vivo, resorbable synthetic mesh elicited an intense yet transient foreign-body response, with macrophages and myofibroblasts persisting through 3 months of implantation. At 6 months, resorbable synthetic mesh was undetectable and the mesh–host tissue interface strength (14.7 ± 7.9 N) was equivalent to that of primary repair (21.4 ± 4.9 N). The composite synthetic mesh elicited a significant foreign-body response following 1 month of implantation. By 3 months, the composite synthetic mesh resorbable films had fully degraded, with foreign-body reaction localized to polypropylene fibers. By 6 months, macrophages had surrounded these polypropylene fibers, with a myofibroblast-positive capsule encircling a macrophage-rich layer. Resorbable and composite synthetic meshes may ultimately not be the most ideal biomaterials in situations where the biological response is expected to lead to a regeneration of host soft tissues.

Retrieval study at 623 human mesh explants made of polypropylene - impact of mesh class and indication for mesh removal on tissue reaction

Textile meshes frequently are implanted in the abdominal wall to reinforce a hernia repair. However, revisions for mesh associated complications confirm that these devices are not completely free of risk. Explanted devices offer an opportunity to define the impact of mesh structure on tissue response. This retrieval study analyses the tissue reaction to 623 polypropylene mesh samples (170 class 1 with large pores, and 453 class 2 with small pores) explanted for pain, infection, or recurrence. Histopathological assessment included morphometry of inflammatory infiltrate (IF) and connective tissue (CT), and of collagen 1/3 ratio. Half of the meshes were removed after more than 23 month. Despite large inter-individual differences removal for infection showed more IF than for pain or recurrence with significant correlation of IF with CT. Class 1 meshes with large pores showed less IF, CT, fistula formation, calcification, and bridging than class 2 meshes with small pores. Meshes removed for recurrence showed a lowered collagen 1/3 ratio in 70%. Large pore class 1 meshes showed an improved tissue response and may be considered as favorable to prevent inflammatory side effects. The presence of lowered collagen 1/3 ratio in most of the samples with recurrences stresses the relevance of an intact healing process. Late manifestation of complications demands long-lasting follow-up. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2013.

A systematic review of randomised control trials assessing mesh fixation in open inguinal hernia repair

PURPOSE

The technique for fixation of mesh has been attributed to adverse patient and surgical outcomes. Although this has been the subject of vigorous debate in laparoscopic hernia repair, the several methods of fixation in open, anterior inguinal hernia repair have seldom been reviewed. The aim of this systematic review was to determine whether there is any difference in patient-based (recurrence, post-operative pain, SSI, quality of life) or surgical outcomes (operative time, length of operative stay) with different fixation methods in open anterior inguinal hernioplasty.

METHODS

A literature search was performed in PubMed, EMBASE and the Cochrane Library databases. Randomised clinical trials assessing more than one method of mesh fixation (or fixation versus no fixation) of mesh in adults (>18 years) in open, anterior inguinal hernia repair, with a minimum of 6-month follow-up and including at least one of the primary outcome measures (recurrence, chronic pain, surgical site infection) were included in the review. Secondary outcomes analysed included post-operative pain (within the first week), quality of life, operative time and length of hospital stay.

RESULTS

Twelve randomised clinical trials, which included 1,992 primary inguinal hernia repairs, were eligible for inclusion. Four studies compared n-butyl-2 cyanoacrylate (NB2C) glues to sutures, two compared self-fixing meshes to sutures, four compared fibrin sealant to sutures, one compared tacks to sutures, and one compared absorbable sutures to non-absorbable sutures. The majority of the trials were rated as low or very low-quality studies. There was no significant difference in recurrence or surgical site infection rates between fixation methods. There was significant heterogeneity in the measurement of chronic pain. Three trials reported significantly lower rates of chronic pain with fibrin sealant or glue fixation compared to sutures. A further three studies reported lower pain rates within the first week with non-suture fixation techniques compared to suture fixation. A significant reduction in operative time, ranging form 6 to 17.9 min with non-suture fixation, was reported in five of the studies. Although infrequently measured, there were no significant differences in length of hospital stay or quality of life between fixation methods.

CONCLUSIONS

There is insufficient evidence to promote fibrin sealant, self-fixing meshes or NB2C glues ahead of suture fixation. However, these products have been shown to be at least substantially equivalent, and moderate-quality RCTs have suggested that both fibrin sealant and NB2C glues may have a beneficial effect on reducing immediate post-operative pain and chronic pain in at-risk populations, such as younger active patients. It will ultimately be up to surgeons and health-care policy makers to decide whether based on the limited evidence these products represent a worthwhile cost for their patients.

Comparison of long-term biocompability of PVDF and PP meshes

BACKGROUND

Abdominal hernia repair is the most frequently performed operation in surgery. Mesh repair in hernia surgery has become an integral component. Although meshes made of PVDF are already in clinical use, so far no data of long-term biocompability are available.

METHODS

In this study a PVDF mesh was compared to a polypropylene mesh with regard to its long-term biocompatibility. A total of 28 rats were randomized to two groups. Mesh material was implanted subcutaneously; animals were euthanized seven days and six months postoperatively. The quantity of inflammatory tissue response was characterized by measuring the diameter of the foreign body granuloma. Furthermore quality of cellular immune response (T-lymphocytes, macrophages, and neutrophils), and inflammation (COX-2) was analyzed by immunohistochemistry. Furthermore the collagen type I/III ratio was determined.

RESULTS

Macrophages, T-lymphocytes, neutrophiles, and COX-2 declined significantly up to six months postoperatively in comparison to day 7 for both PVDF and PP meshes, and in both groups the collagen ratio increased significantly in the course of time. PVDF meshes showed a foreign body granuloma size significantly reduced compared to PP (7 days: 20 ± 2 μm vs. 27 ± 2 μm; 6 months 15 ± 2 μm vs. 22 ± 3 μm; p < .001). However no significant differences were found analyzing cellular response six months postoperatively.

CONCLUSIONS

Our current data suggest that even in the long-term course after six months and despite a higher effective surface of the PVDF samples it showed a smaller foreign body granuloma than with PP whereas the cellular response was similar.

Infections associated with prosthetic repairs of abdominal wall hernias: pathology, management and results

PURPOSE

To analyse clinical and demographic factors of patients who suffered infection of the surgical site requiring mesh removal as a complication of prosthetic repairs, details of the hernioplasties in which meshes were implanted and their management and outcomes.

METHODS

Factors related to infection (demographic variables and characteristics of the repairs and mesh utilised) and the management before proceeding to mesh removal were obtained from patient charts. Collected specimens (meshes and tissues) from 32 consecutive patients were cultured and observed microscopically. The outcomes after mesh removal were prospectively evaluated.

RESULTS

Twenty-two patients underwent incisional hernioplasties and ten inguinal hernioplasties; most of the procedures took a long time, and 28 patients presented early wound complications (seroma or haematoma). During the “implantation–removal” interval, some conservative treatments, such as drainages or sinus resection, were attempted under local anaesthesia. Twenty-two meshes were totally removed (nine after partial extraction); in the remaining ten cases partially removal was successful. Most of the meshes (24) were made of multi-filament polypropylene; microscopic observation of neighbouring tissues showed leucocyte infiltration, giant cell reaction, disorganisation of the collagen fibres and abscedation. Treatment of 32 patients required 51 operations. Following mesh removal, there were six recurrences and two fistulas of the bowel. The average follow-up was 40 months (30–97).

CONCLUSIONS

Most of the infections requiring mesh removal were related to prolonged repair operations that presented untreated early postoperative wound complications. Partial extraction of meshes frequently leads to failures and complications. Surgical exploration should be performed under general anaesthesia to accomplish complete mesh extraction.

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.

Clinicopathological study of patients requiring reintervention after sacrocolpopexy with xenogenic acellular collagen grafts

PURPOSE

We describe the operative and histopathological findings of patients requiring reintervention because of symptomatic vault prolapse or graft related complications following sacrocolpopexy using xenografts.

MATERIALS AND METHODS

A total of 13 patients underwent secondary sacrocolpopexy because of failure (8) or vaginal revision (5) because of a graft related complication after the initial sacrocolpopexy with porcine dermal collagen (9) or small intestinal submucosa (4). Outcome measures were operative findings and histology of specimens obtained at reintervention. Sections were semiquantitatively scored for the presence of infection, foreign body reaction and fibrosis by a pathologist blinded to the outcome and graft type.

RESULTS

Reinterventions for failure and graft related complications were performed a median of 33 and 15 months, respectively, after the initial operation. Pathology of porcine dermal collagen failures (6) revealed local degradation associated with a minimal foreign body reaction. Porcine dermal collagen remnants were surrounded by minimal fibrosis and neovascularization. Small intestinal submucosa implants of failures (2) were entirely replaced by collagen rich and moderately vascularized connective tissue. Pathology of 3 erosions (all 3 porcine dermal collagen) revealed a locally degraded implant that was surrounded by histiocytes and a polymorphonuclear infiltrate. Pathology of 2 early infections, both small intestinal submucosa, revealed a massive polymorphonuclear infiltration with the implant material remodeled and replaced by loose connective tissue.

CONCLUSIONS

In these clinical recurrences porcine dermal collagen implants were usually locally degraded but still recognizable several years after implantation. Small intestinal submucosa implants were fully replaced by connective tissue. Therefore, the cause of recurrence remains unclear. Porcine dermal collagen erosions displayed features of infection and degradation.

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.

Mesh for hernia repair

Randomized control trials may be inappropriate

Immunohistochemical analysis of host reaction to heavyweight-, reduced-weight-, and expanded polytetrafluoroethylene (ePTFE)-based meshes after short- and long-term intraabdominal implantations

BACKGROUND

Prosthetic meshes induce a variety of inflammatory changes in the host, which may lead to excessive scarring with detrimental clinical consequences, especially in the long term. This study aimed to characterize the degree of short- and long-term inflammatory changes induced by common prosthetic meshes.

METHODS

Twenty 4 x 4-cm samples each of expanded polytetrafluoroethylene (ePTFE), heavyweight polypropylene (hPP), ePTFE/heavyweight polypropylene (ePTFE/hPP), and reduced-weight polypropylene/regenerated cellulose (rPP) were implanted intraperitoneally in 40 rabbits for 4 or 12 months. After explantation, samples of mesh/tissue complex were analyzed for the degrees of cellular apoptosis (enzyme-linked immunoassay [ELISA]) and cellular turnover (mouse monoclonal antibody).

RESULTS

In the short term, the degree of apoptosis in the hPP mesh was significantly higher than in the ePTFE and rPP groups. Similarly, it was higher in the ePTFE/hPP group than in either the ePTFE or the rPP group. The amount of Ki-67-positive cells was significantly higher in the hPP group than in the ePTFE or rPP group. The cell turnover in the ePTFE/hPP group was similar to that in the hPP group, but significantly higher than in either the ePTFE or the rPP group. The rPP group, in turn, had a higher Ki-67 score than the ePTFE group. In the long term, both the degree of apoptosis and Ki-67 positivity were significantly lower in the rPP and ePTFE groups than in either the ePTFE/hPP or the hPP group. A significant decrease in Ki-67 scores between the short and long-term groups was found only in the rPP group.

CONCLUSION

In the short term, heavyweight polypropylene-based meshes were associated with significantly higher cell proliferation and death. A significantly higher degree of apoptosis and cell turnover were associated with heavyweight polypropylene-based meshes even 1 year after implantation, indicating ongoing inflammation and scar remodeling. On the other hand, ePTFE and reduced-weight polypropylene meshes were associated with nearly physiologic levels of inflammatory markers. Overall, an exaggerated and persistent host foreign body response to heavyweight polypropylene-based meshes indicates poor biocompatibility, with potential detrimental clinical sequela.

In vivo evaluation of a new composite mesh (10% polypropylene/90% poly-L-lactic acid) for hernia repair

The increasing use of mesh insertion for groin hernia repair is dashed by a worrying prevalence of chronic pain frequently related as a reaction to the biomaterial implantation. Thus, new biocompatible prosthesis, designed as a composite material associating polypropylene (PP) and long-term absorbable material, are now under development. In the present study, the typical commercially available Prolene mesh has been compared to two new meshes designed with 3-fold less PP, either alone (light PP) or associated with poly-L-lactic acid (PP-PLA) accounting for 90% of the mesh weight. These PP-mesh variants were implanted in an extraperitoneal position within the abdominal wall of 90 rats. Mesh adhesion and size were determined at autopsy 2, 4 and 8 weeks after implantation (10 animals per group) and morphometric parameters of the host tissues by light microscopy. Prolene and light PP-meshes presented intra-corporeal shrinkage and tissue adhesion, both more pronounced with light-PP, whilst PP-PLA meshes were not affected in spite of a strongest fibrosis. In contrast to Prolene and even more with light PP meshes, inflammation and cell-mediated immune responses were reduced without occurrence of angiogenesis or oedema. All these findings advocate together for a better tolerance of this new composite biomaterial, more likely due to a low macrophage response that appeared statistically correlated to the absence of mesh shrinkage and to a decreased adhesion to the tissue. On the basis of these experimental observations, it could be expected that the better tolerance of this composite biomaterial may avoid both long-term pain and recurrence when used as plug in groin hernia repair.

Immune response against polyester implants is influenced by the coating substances

The aim of this study was to evaluate the influence of the coating of polymer implants upon the individual humoral immune response to the polymer matrix. Intramuscular implantation and explantation of samples from three different polyester vascular prostheses coated with collagen, gelatin, or human serum albumin was performed in LEW.1A rats and subsequently compared to sham operated control animals. Antibodies in serum samples were detected by means of enzyme immunoassays employing particles of pure polyester and the respective prosthesis, or solid phase bound coating substances as targets. In contrast to the controls, all animals with implants demonstrated a high antipolyester antibody response with a broad individual variability graduated according to the prosthesis coatings: gelatin > albumin > collagen. This was further significantly increased after the second implantation/first explantation and declined following the last explantation. Only animals with albumin-coated implants revealed specific antibodies to the coating as well as the strongest overall immunological reaction against the prosthesis already on day 8. Specificity of polymer antibodies was demonstrated by competitive inhibition of median antibody binding. Our results showed a specific immune reaction as a result of the applied polymer, which varied due to the surface-coating and individual factors.

The biology behind fascial defects and the use of implants in pelvic organ prolapse repair

Implant materials are increasingly being used in an effort to reduce recurrence after prolapse repair with native tissues. Surgeons should be aware of the biology behind both the disease as well as the host response to various implants. We will discuss insights into the biology behind hernia and abdominal fascial defects. Those lessons from "herniology" will, wherever possible, be applied to pelvic organ prolapse (POP) problems. Then we will deal with available animal models, for both the underlying disease and surgical repair. Then we will go over the features of implants and describe how the host responds to implantation. Methodology of such experiments will be briefly explained for the clinician not involved in experimentation. As we discuss the different materials available on the market, we will summarize some results of recent experiments by our group.

Collagen foil (TissuFoil E) reduces the formation of adhesions when using polypropylene mesh for the repair of experimental abdominal wall defects

BACKGROUND AND AIMS

Polypropylene meshes (PPMs) are routinely used in the treatment of incisional hernias to achieve a tension-free closure of the abdominal wall. Severe adhesions are a common cause of intestinal obstruction, or even intestinal fistulas. Using a porcine model, we investigated whether applying a collagen foil (CF) to the undersurface of a PPM will reduce adhesion formation.

METHODS

In ten domestic pigs (20-25 kg), a median laparotomy was performed. In each animal the abdominal wall was reconstructed using three types of closure: simple closure by a running suture (control), PPM only, and PPM covered with CF (PPM-CF). After 6 weeks, the abdominal wall with adherent tissue was resected en bloc for macroscopic (quality and quantity of adhesion formation) and histological work-up.

RESULTS

The PPM-CF showed significantly less severe (1.9 vs 3.0 according to a scoring system), and also less extended (23.8 vs 55.9% total coverage of the mesh), adhesions to the resected abdominal wall. Histological examination revealed fewer and less severe inflammatory reactions, necrosis, and foreign body reactions for the mesh and CF (PPM-CF).

CONCLUSION

To combine meshes with the anti-adhesion properties of a CF may be another option to achieve more physiological and more tolerable prosthetic materials.

The new 4DDome prosthesis: an original light and partially absorbable composite mesh for hernia repair

INTRODUCTION

The use of non-absorbable meshes for the repair of inguinal hernias has become standard; however, these meshes have been associated with complications including long-term postoperative pain. To this end, a new partially absorbable composite mesh has been developed, and the aim of this study was to investigate its efficacy in animal and human trials.

MATERIALS AND METHODS

Sixty male Wistar rats were used to evaluate the behavior of the newly designed composite mesh. Composite meshes were implanted in the extra-peritoneal plane for 2, 4 and 8 weeks and compared to a standard polypropylene mesh. Forty patients with symptomatic inguinal hernias were treated using a new 4DDome designed prosthesis. Follow-up was by clinical and ultrasound examination at 1, 6 and 12 months.

RESULTS

The animal study demonstrated that the inflammatory reaction associated with the new composite mesh was significantly lower than a standard polypropylene mesh, characterized by a lower macrophage infiltrate (P < 0.001). The mesh did not shrink over the 8-week period, unlike the polypropylene mesh (P < 0.05). The human study showed that there were three minor postoperative complications, no recurrences and the mesh was well tolerated. Follow-up with serial ultrasound showed that at 10 days and 1 month the dome was clearly visible in position; however, by 6 months it had flattened out, been partially absorbed and become incorporated into the repair.

CONCLUSION

These experimental and clinical studies have validated the concept of the new 4DDome composite mesh. It was well tolerated and was associated with good short-term results. The combination of the dome shape and the new composite mesh means that less polypropylene is required and represents a significant advance in anterior hernia repair.

Incisional hernia: challenge of re-operations after mesh repair

BACKGROUND AND AIMS

The widespread use of meshes for the repair of incisional hernia is currently followed by an increasing number of re-operations. The incidence of incisional hernia recurrence after mesh repair varies between 3 and 32%. The problem of mesh failure and options for another surgical intervention seem rather unattended.

METHODS

We present our experience of 77 re-operations after previous mesh repair that were performed between 1995 and 2004 out of a total of 1,070 operations for incisional hernia. The retrospective analysis focused on recurrence in relation to location, material of the previous mesh repair and the surgical procedure to resolve the problem.

RESULTS

The locations of the preceding meshes were epifascial as onlays (n=23), retromuscular as sublays (n=46), within the defect as inlays (n=6) or intraperitoneally (n=2). The direction of the incision was vertical medial (n=41) or horizontal crossing the linea semilunaris (n=36). Recurrences after median incisional hernia mesh repair mainly occurred at the cranial border of the mesh subxiphoidal. Except for two patients, all recurrences manifested at the margin of the enclosed mesh.

CONCLUSIONS

Re-operation after previous mesh repair is a surgical challenge. The type of revision procedure has to consider the position and material of the previous mesh. In our clinic recurrences, heavyweight polypropylene meshes were mostly treated with mesh exchange and lightweight polypropylene meshes could be treated by extension with a second mesh. In contrast to suture techniques, deficient mesh repairs are more evidently related to technical problems.

Modifications in the production of cytokines and growth factors in drainage fluids following mesh implantation after incisional hernia repair

BACKGROUND

The aim of this study was to evaluate changes in the production of some cytokines (interleukins [ILs]-6, -10, -1, and -1ra), vascular endothelial growth factor, and beta-fibroblast growth factor after polypropylene mesh implantation.

METHODS

Twenty female patients were divided into 2 groups. In 1 group, hernia repair was performed with conventional sutures (CR), whereas in the other group polypropylene mesh (MR) was used. Growth factors and cytokines production was analyzed in wound drain fluids based on the amount produced during 24 hours.

RESULTS

IL-1 increased substantially in MR patients on postoperative days 1 and 2. IL1-ra and IL-10 production was always significantly higher in CR patients. IL-6 production did not show any considerable difference between the 2 groups. Vascular endothelial growth factor production was significantly higher in the MR than the CR group at all time points, whereas beta-fibroblast growth factor production was higher in the MR than the CR group only on postoperative day 1.

COMMENTS

Our data suggest that different surgical procedures induce various levels of inflammation and that implantation of prostheses significantly stimulates the inflammatory response.

The lightweight and large porous mesh concept for hernia repair

In modern hernia surgery, there are two competing mesh concepts which often lead to controversial discussions, on the one hand the heavyweight small porous model and on the other, the lightweight large porous hypothesis. The present review illustrates the rationale of both mesh concepts and compares experimental data with the first clinical data available. In summary, the lightweight large porous mesh philosophy takes into consideration all of the recent data regarding physiology and mechanics of the abdominal wall and inguinal region. Furthermore, the new mesh concept reveals an optimized foreign body reaction based on reduced amounts of mesh material and, in particular, a significantly decreased surface area in contact with the recipient host tissues by the large porous model. Finally, recent data demonstrate that alterations in the extracellular matrix of hernia patients play a crucial role in the development of hernia recurrence. In particular, long-term recurrences months or years after surgery and implantation of mesh can be explained by the extracellular matrix hypothesis. However, if the altered extracellular matrix proves to be the weak area, the decisive question is whether the amount of material as well as mechanical and tensile strength of the surgical mesh are really of significant importance for the development of recurrent hernia. All experimental evidence and first clinical data indicate the superiority of the lightweight large porous mesh concept with regard to a reduced number of long-term complications and particularly, increased comfort and quality of life after hernia repair.

Comparison of host response to polypropylene and non-cross-linked porcine small intestine serosal-derived collagen implants in a rat model

OBJECTIVE

To compare the host response, architectural integration and tensile strength of polypropylene and porcine small intestine submucosa-derived implants in a rat model.

DESIGN

Experimental study.

SETTING

Center for Surgical Technologies, Faculty of Medicine, Katholieke Universiteit Leuven, Belgium.

SAMPLE

Forty-eight adult male Wistar rats weighing 220-250 g randomised to receive either implant.

METHODS

Full thickness abdominal wall defects were primarily repaired with polypropylene mesh (Marlex) (MX group) or porcine small intestine submucosa (Surgisis) (SIS group). Animals were sacrificed at 7, 14, 30 and 90 days after implantation.

MAIN OUTCOME MEASURES

The presence of herniation, infection and intra-peritoneal adhesions. Change in thickness and tensile strength of implant. Histopathological and immunohistochemical appearances of inflammatory response and collagen deposition.

RESULTS

Implants from the SIS group showed a short term increase in thickness in the first 14 days. Formation of adhesions was significantly more intense in the MX group at 30 days, and more extensive in the SIS group at 90 days. Tensile strength increased over time in both groups but was significantly lower in the SIS group than the MX group at 30 days. Implants in the MX group showed a more pronounced inflammatory response and more pronounced new vessel formation than the SIS group. Collagen formation was initially more fibrous and better organised in the MX group but became greater in the SIS group at 90 days.

CONCLUSIONS

Biologically derived implant material induced a less pronounced inflammatory response and differences in collagen deposition. At 30 days tensile strength was weaker in the biological implant group but was equivalent by 90 days. These differences may have implications for the in vivo performance of the materials.

In vivo comparison of suburethral sling materials

In vivo tissue responses were compared for three commercially available polypropylene suburethral slings that differ markedly in fabric structure and in size of resulting interstices and pores. All three elicited the same basic inflammatory response; however, individual fabric structures produced distinct differences in tissue formation within each mesh. The presence of numerous, closely spaced, small diameter filaments prevented formation of extensive fibrous connective tissue within two slings (ObTape and IVS Tunneller mesh). The much larger diameter monofilament and open knit structure of the Monarc sling permitted the most extensive fibrous tissue integration. These differences may be of interest to physicians considering clinical use.

Acute inflammatory response after inguinal and incisional hernia repair with implantation of polypropylene mesh of different size

BACKGROUND

The purpose of this study was to assess the modifications of interleukin (IL)-6, C-reactive protein (CRP), leukocytes and fibrinogen after implantation of polypropylene mesh.

METHODS

Thirty-six patients were included in this study and divided into two groups. To the first group were allocated patients affected by inguinal hernia and undergoing conventional repair (subgroup Ia) or hernioplasty with 40-cm(2) polypropylene mesh (subgroup Ib). To the second group were allocated patients affected by incisional hernia and undergoing conventional repair (subgroup IIa) or incisional hernia repair with 400-cm(2) polypropylene mesh (subgroup IIb). Peripheral venous blood samples were collected 24 h before surgery and then 6, 24, 48 and 168 h postoperatively.

RESULTS

We present evidence that serum levels of IL-6, CRP, leukocytes and fibrinogen were significantly increased postoperatively in all subgroups compared with their baseline values. In particular, the production of inflammatory mediators was higher in subgroups Ib vs Ia and IIb vs IIa. Comparing the entities of the inflammatory responses among various groups we found that it was clear that they were similar in subgroups Ib and IIa, and that the highest were in subgroup IIb and the lowest in subgroup Ia.

CONCLUSION

The data show that conventional inguinal and incisional hernia repair induces an inflammatory response, which is smaller than that observed if both operations are carried out with polypropylene meshes. Furthermore, the results suggest that a larger mesh is associated with a higher production of inflammation mediators.

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.

The Lichtenstein repair for groin hernias

The Lichtenstein tension-free mesh repair opened a new era in groin hernia repair. Without the risk of serious morbidity, it is now readily performed using local anesthesia in patients previously considered unsuitable for surgery. Fears of serious complications related to mesh implantation have proved to be without foundation. As a local anesthetic day care technique without the need for complex and expensive instrumentation, overall costs can be kept to a minimum without compromising the safety or the long-term success of the procedure. It is a straightforward technique to learn, with high patient acceptability and an exceedingly low recurrence rate. At present it must be considered the gold standard of groin hernia repair.