Degradation, infection and heat effects on polypropylene mesh for pelvic implantation: what was known and when it was known

Potentiality of Antibacterial Gels for the Prophylactic Coating of Hernia Repair Prosthetic Materials

Prosthetic mesh infection constitutes one of the major postsurgical complications following abdominal hernia repair. Antibacterial coatings represent a prophylactic strategy to reduce the risk of infection. This study assessed the in vitro response of two antibacterial gels made of 1% carboxymethylcellulose (CMC) functionalized with an antiseptic (chlorhexidine, CHX) or an antibiotic (rifampicin, RIF), developed for the coating of polypropylene (PP) meshes for hernia repair. Fragments of a lightweight PP mesh (1 cm2) presoaked in the unloaded or drug-loaded CMC (0.05% CHX; 0.13 mg/mL RIF) were challenged with 106 CFU/mL Staphylococcus aureus (Sa) and methicillin-resistant S. aureus (MRSA). Agar diffusion tests, sonication, turbidimetry, crystal violet staining, scanning electron microscopy and cell viability assays (fibroblasts, mesothelial cells) were performed to evaluate the response of the gels. Both compounds-especially the RIF-loaded gel-exerted a biocidal effect against gram-positive bacteria, developing wide inhibition halos, precluding adhesion to the mesh surface, and hampering bacterial survival in culture. The antibiotic gel proved innocuous, while lower viability was found in cells exposed to the antiseptic (p < 0.05). Together with their fast, affordable, convenient processing and easy application, the results suggest the potential effectiveness of these drug-loaded CMC gels in providing meshes with an antibacterial coating exhibiting great biocide performance.

Analyzing material changes consistent with degradation of explanted polymeric hernia mesh related to clinical characteristics

BACKGROUND

Proposed mechanisms that potentially contribute to polypropylene mesh degradation after in vivo exposure include oxidizing species and mechanical strains induced by normal healing, tissue integration, muscle contraction, and the immediate and chronic inflammatory responses.

METHODS

This study explores these potential degradation mechanisms using 63 mesh implants retrieved from patients after a median implantation time of 24 months following hernia repair surgery (mesh explants) and analysis of multivariate associations between the material changes and clinical characteristics. Specifically, polypropylene mesh degradation was characterized in terms of material changes in surface oxidation, crystallinity and mechanical properties, and clinical characteristics included mesh placement location, medical history and mesh selection.

RESULTS

Compared to pristine control samples, subsets of mesh explants had evidence of surface oxidation, altered crystallinity, or changed mechanical properties. Using multivariate statistical approach to control for clinical characteristics, infection was a significant factor affecting changes in mesh stiffness and mesh class was a significant factor affecting polypropylene crystallinity changes.

CONCLUSIONS

Highly variable in vivo conditions expose mesh to mechanisms that alter clinical outcomes and potentially contribute to mesh degradation. These PP mesh explants after 0.5 to 13 years in vivo had measurable changes in surface chemistry, crystallinity and mechanical properties, with significant trends associated with factors of mesh placement, mesh class, and infection.

Host-biomaterial interactions in mesh complications after pelvic floor reconstructive surgery

Polypropylene (PPL) mesh is widely used in pelvic floor reconstructive surgery for prolapse and stress urinary incontinence. However, some women, particularly those treated using transvaginal PPL mesh placement for prolapse, experience intractable pain and mesh exposure or extrusion. Explanted tissue from patients with complications following transvaginal implantation of mesh is typified by a dense fibrous capsule with an immune cell-rich infiltrate, suggesting that the host immune response has a role in transvaginal PPL mesh complications through the separate contributions of the host (patient), the biological niche within which the material is implanted and biomaterial properties of the mesh. This immune response might be strongly influenced by both the baseline inflammatory status of the patient, surgical technique and experience, and the unique hormonal, immune and microbial tissue niche of the vagina. Mesh porosity, surface area and stiffness also might have an effect on the immune and tissue response to transvaginal mesh placement. Thus, a regulatory pathway is needed for mesh development that recognizes the roles of host and biological factors in driving the immune response to mesh, as well as mandatory mesh registries and the longitudinal surveillance of patients.

An assessment of the toxicity of polypropylene microplastics in human derived cells

Environmental pollution caused by plastic waste is a growing global problem. Discarded plastic products and debris (microplastic particles) in the oceans detrimentally affect marine ecosystems and may impact human. Humans are exposed to plastic debris via the consumption of seafood and drinking water, contact with food packaging, or inhalation of particles. The accumulation of microplastic particles in humans has potential health risks such as cytotoxicity, hypersensitivity, unwanted immune response, and acute response like hemolysis. We investigated the cellular responses of secondary polypropylene microplastics (PP particles) of approximately ~20 μm and 25-200 μm in different condition and size to normal cells, immune cells, blood cells, and murine immune cells by cytokine analysis, ROS assay, polarization assay and proliferation assay. We found that PP particles showed low cytotoxicity effect in size and concentration manner, however, a high concentration, small sized, DMSO method of PP particles stimulated the immune system and enhanced potential hypersensitivity to PP particles via an increase in the levels of cytokines and histamines in PBMCs, Raw 264.7 and HMC-1 cells.

Bioerosion of Synthetic Sling Explants

This study was performed to investigate the changes over time in polypropylene (PP) mesh explants from women with stress urinary incontinence originally treated with a midurethral PP sling. Following Institutional Review Board (IRB) approval, 10 PP explants removed for pain or obstructive symptoms between January and June 2016 were analyzed through various techniques to determine the degradation of the material in vivo. Exclusion criteria were exposed or infected mesh sling or sling in place for less than six months. One pristine control was studied for comparison. The explant samples were analyzed with scanning electron microscopy to visualize the surface defects as well as infrared spectroscopy and energy dispersive X-ray spectroscopy to determine if the degradation was oxidative in nature. The results show qualitative and quantitative bioerosion over the surface of the explant samples and an increase in the content of oxygen pointing toward oxidative degradation occurring in vivo.

Is vaginal mesh a stimulus of autoimmune disease?

BACKGROUND

Polypropylene mesh has been used as a means of reinforcing weak tissues in women with pelvic organ prolapse and stress urinary incontinence.

OBJECTIVE

We sought to investigate a potential link between the development of systemic/autoimmune disorders and synthetic polypropylene mesh repairs.

STUDY DESIGN

New York State Department of Health Statewide Planning and Research Cooperative System data were utilized to conduct this retrospective cohort study. Adult women undergoing surgery for pelvic organ prolapse with vaginally implanted mesh from January 2008 through December 2009 in inpatient and ambulatory surgery settings in New York State were identified. Two separate control cohorts were created to compare outcomes, including a screening colonoscopy cohort and a vaginal hysterectomy cohort for benign gynecologic conditions (without pelvic organ prolapse repair or sling). Patients in the mesh cohort were individually matched to the control cohorts based on demographics, comorbidities, and procedure date. The development of systemic/autoimmune disease was determined before and after matching for 1-year, 2-year, 3-year, and entire follow-up (up to 6 years until December 2014) and differences between groups were evaluated.

RESULTS

A total of 2102 patients underwent mesh-based pelvic organ prolapse surgery from January 2008 through December 2009. In the control cohorts, 37,298 patients underwent colonoscopy and 7338 underwent vaginal hysterectomy. When patients were matched based on demographics, comorbidities, and procedure time, mesh-based surgery was not associated with an increased risk of developing autoimmune disease at any of the evaluated time periods.

CONCLUSION

Mesh-based vaginal surgery was not associated with the development of systemic/autoimmune diseases. These data refute claims against mesh as a cause of systemic disease.

Type IIIb Endoleak Associated With an Infected Thoracoabdominal Endograft

We present a 63-year-old male patient who presented with vague abdominal pain after an endoluminal thoracoabdominal aneurysm repair. He was found to have an infected endograft and an associated type IIIb endoleak. We believe that the infection contributed to the fabric degradation along the endograft and resulted in an expanding endoleak. Graft explantation was not performed because of the patient's multiple comorbidities, and the endoleak was treated with an additional stent graft and suppressive antibiotics. Endograft infection may lead to endograft degradation and associated leak. Therefore, an infectious etiology, although rare, should be considered when evaluating a delayed type IIIb endoleak.

Novel Bioceramic Urethral Bulking Agents Elicit Improved Host Tissue Responses in a Rat Model

Objectives. To test the physical properties and host response to the bioceramic particles, silica-calcium phosphate (SCPC10) and Cristobalite, in a rat animal model and compare their biocompatibility to the current clinically utilized urethral bulking materials. Material and Methods. The novel bulking materials, SCPC10 and Cristobalite, were suspended in hyaluronic acid sodium salt and injected into the mid urethra of a rat. Additional animals were injected with bulking materials currently in clinical use. Physiological response was assessed using voiding trials, and host tissue response was evaluated using hard tissue histology and immunohistochemical analysis. Distant organs were evaluated for the presence of particles or their components. Results. Histological analysis of the urethral tissue five months after injection showed that both SCPC10 and Cristobalite induced a more robust fibroblastic and histiocytic reaction, promoting integration and encapsulation of the particle aggregates, leading to a larger bulking effect. Concentrations of Ca, Na, Si, and P ions in the experimental groups were comparable to control animals. Conclusions. This side-by-side examination of urethral bulking agents using a rat animal model and hard tissue histology techniques compared two newly developed bioactive ceramic particles to three of the currently used bulking agents. The local host tissue response and bulking effects of bioceramic particles were superior while also possessing a comparable safety profile.

Biomechanical, Topological and Chemical Features That Influence the Implant Success of an Urogynecological Mesh: A Review

Synthetic meshes are normally used to treat several diseases in the field of urogynecological surgery. Not-optimal selection of mesh and/or its not-correct implant may increase patient's pain and discomfort. The knowledge of mechanical behaviour and topological and chemical properties of a mesh plays a fundamental role to minimize patient's suffering and maximize the implant success. We analysed several papers reporting the meshes application for urogynecological pathologies, to extrapolate the principal parameters that normally are used to characterise the biomechanical, topological, and chemical properties, and to verify their influence on implant success. In this way we want demonstrate that, knowing these features, it is possible to foresee the success of a mesh implant. This review shows that the application of a mesh strictly depends on elastic modulus, failure load, porosity and pore size, filament diameter, polymer weight, and crystallinity. To increase the success of the implant and to help choice of optimal mesh for a clinical need, two indexes have been proposed for comparing, in an easier way, the mechanical performance of different commercially available meshes.

Surgical mesh for ventral incisional hernia repairs: Understanding mesh design

Surgical mesh has become an indispensable tool in hernia repair to improve outcomes and reduce costs; however, efforts are constantly being undertaken in mesh development to overcome postoperative complications. Common complications include infection, pain, adhesions, mesh extrusion and hernia recurrence. Reducing the complications of mesh implantation is of utmost importance given that hernias occur in hundreds of thousands of patients per year in the United States. In the present review, the authors present the different types of hernia meshes, discuss the key properties of mesh design, and demonstrate how each design element affects performance and complications. The present article will provide a basis for surgeons to understand which mesh to choose for patient care and why, and will explain the important technological aspects that will continue to evolve over the ensuing years.

Surgical mesh for ventral incisional hernia repairs: Understanding mesh design

Surgical mesh has become an indispensable tool in hernia repair to improve outcomes and reduce costs; however, efforts are constantly being undertaken in mesh development to overcome postoperative complications. Common complications include infection, pain, adhesions, mesh extrusion and hernia recurrence. Reducing the complications of mesh implantation is of utmost importance given that hernias occur in hundreds of thousands of patients per year in the United States. In the present review, the authors present the different types of hernia meshes, discuss the key properties of mesh design, and demonstrate how each design element affects performance and complications. The present article will provide a basis for surgeons to understand which mesh to choose for patient care and why, and will explain the important technological aspects that will continue to evolve over the ensuing years.

Degradation of polypropylene in vivo: A microscopic analysis of meshes explanted from patients

Polypropylene meshes, originally introduced for hernia repair, are presently utilized in several anatomical sites. Several million are implanted annually worldwide. Depending on the device, up to 10% will be excised to treat complications. The excised meshes can provide material to study the complications, however, they have remained underutilized over the last decades and the mechanisms of complications continue to be incompletely understood. The fundamental question as to whether polypropylene degrades in vivo is still debated. We have examined 164 excised meshes using conventional microscopy to search for features of polypropylene degradation. Four specimens were also examined by transmission electron microscopy. The degraded material, detected by its ability to absorb dyes in the degradation nanopores, formed a continuous layer at the surface of the mesh fibers. It retained birefringence, inclusions of non-degraded polypropylene, and showed ability to meld with the non-degraded fiber core when heated by the surgical cautery. Several features indicated that the degradation layer formed in vivo: inflammatory cells trapped within fissures, melting caused by cautery of excision surgery, and gradual but progressive growth of the degradation layer while in the body. Cracking of the degraded material indicated a contribution to clinically important mesh stiffening and deformation. Chemical products of degradation need to be analyzed and studied for their role in the mesh-body interactions. The described methods can also be used to study degradation of other materials. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 237-248, 2017.

The influence of mesh topology in the abdominal wall repair process

The tissue integration and the formation of adhesions in the repair of abdominal wall defects are principally led to the topology and the mechanical properties of implanted prosthesis. In this study we analyzed the influence of the topology of the meshes for abdominal wall repair, made of polypropylene (PP), evaluating its ability to prevent and to minimize the formation of adhesions, and to promote tissue ingrowth. Two series of in vivo studies were performed. In the first, two types of PP meshes, a lightweight macroporous mesh (LWM) and a heavyweight microporous mesh (HWM) were compared with determine the optimal porosity for tissue integration. In the second, a composite mesh, Clear Mesh Composite (CMC), made of a LWM sewn on a PP planar smooth film, was compared with a PP planar film, to demonstrate how two different topologies of same material are able to induce different tissue integration with the abdominal wall and different adhesion with internal organs. In both studies, the prostheses were implanted in Wistar rats and histological analysis and mechanical characterization of tissue coupled with the implants were performed. LWM showed better host tissue ingrowth in comparison to HWM. CMC prosthesis showed no adhesions to the viscera and no strong foreign body reaction, moreover its elasticity and anisotropy index were more similar to that of natural tissue. These results demonstrated that the surface morphology of PP surgical meshes allowed to modulate their repair ability. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1220-1228, 2016.

Evaluation of surgical instrument handling on polypropylene mesh using scanning electron microscopy

INTRODUCTION AND HYPOTHESIS

To evaluate the effect of surgical instruments handling on polypropylene mesh using scanning electron microscopy (SEM).

METHODS

We applied different surgical instruments, including a few robotic ones, to pieces of polypropylene mesh. SEM was used to evaluate the morphological changes with this intervention.

RESULTS

Straight hemostat, laparoscopic atraumatic grasper, laparoscopic needle driver, and robotic instruments (Bipolar forceps, Cadiere forceps, PK dissecting forceps and SutureCut) were applied to the mesh. SEM images of tool-affected mesh regions in specimens handled by different instruments along with the images of intact mesh were obtained. Average mesh fiber diameters, as well as the average parameters characterizing instrument-affected regions, were measured. There was substantial widening of the fibers in specimens handled by hemostat or a needle holder. An elliptical but much longer and narrower tool marking with more surface roughness was observed in mesh handled by a grasper. A ∼25-μm-wide and ∼200-μm-long strap was split on one side from the core of the fiber caused by Cadiere.

CONCLUSIONS

There are morphological changes to polypropylene mesh caused by instrument handling. These changes are different depending on the instrument used. These alterations vary from changes in the surface creating roughness of the fiber, compression of the mesh with narrowing of the fiber in at least one direction or actual splitting or pitting of the fiber. Since there are no data regarding the effect of these morphological changes to the ultimate functioning of the mesh, surgeons should minimize mesh handling by instruments.

Fiber-based tissue engineering: Progress, challenges, and opportunities

Tissue engineering aims to improve the function of diseased or damaged organs by creating biological substitutes. To fabricate a functional tissue, the engineered construct should mimic the physiological environment including its structural, topographical, and mechanical properties. Moreover, the construct should facilitate nutrients and oxygen diffusion as well as removal of metabolic waste during tissue regeneration. In the last decade, fiber-based techniques such as weaving, knitting, braiding, as well as electrospinning, and direct writing have emerged as promising platforms for making 3D tissue constructs that can address the abovementioned challenges. Here, we critically review the techniques used to form cell-free and cell-laden fibers and to assemble them into scaffolds. We compare their mechanical properties, morphological features and biological activity. We discuss current challenges and future opportunities of fiber-based tissue engineering (FBTE) for use in research and clinical practice.

Tissue engineering as a potential alternative or adjunct to surgical reconstruction in treating pelvic organ prolapse

INTRODUCTION AND HYPOTHESIS

Cell-based tissue engineering strategies could potentially provide attractive alternatives to surgical reconstruction of native tissue or the use of surgical implants in treating pelvic organ prolapse (POP).

METHODS

Based on a search in PubMed, this review focuses on candidate cell types, scaffolds, and trophic factors used in studies examining cell-based tissue engineering strategies to treat POP, stress urinary incontinence (SUI), and the closely related field of hernias.

RESULTS

In contrast to the field of SUI, the use of cell-based tissue engineering strategies to treat POP are very sparsely explored, and only preclinical studies exist.

CONCLUSION

The available evidence suggests that the use of autologous muscle-derived cells, fibroblasts, or mesenchymal stem cells seeded on biocompatible, degradable, and potentially growth-promoting scaffolds could be an alternative to surgical reconstruction of native tissue or the use of conventional implants in treating POP. However, the vagina is a complex organ with great demands of functionality, and the perfect match of scaffold, cell, and trophic factor has yet to be found and tested in preclinical studies. Important issues such as safety and economy must also be addressed before this approach is ready for clinical studies.

Tissue engineering as a potential alternative or adjunct to surgical reconstruction in treating pelvic organ prolapse

INTRODUCTION AND HYPOTHESIS

Cell-based tissue engineering strategies could potentially provide attractive alternatives to surgical reconstruction of native tissue or the use of surgical implants in treating pelvic organ prolapse (POP).

METHODS

Based on a search in PubMed, this review focuses on candidate cell types, scaffolds, and trophic factors used in studies examining cell-based tissue engineering strategies to treat POP, stress urinary incontinence (SUI), and the closely related field of hernias.

RESULTS

In contrast to the field of SUI, the use of cell-based tissue engineering strategies to treat POP are very sparsely explored, and only preclinical studies exist.

CONCLUSION

The available evidence suggests that the use of autologous muscle-derived cells, fibroblasts, or mesenchymal stem cells seeded on biocompatible, degradable, and potentially growth-promoting scaffolds could be an alternative to surgical reconstruction of native tissue or the use of conventional implants in treating POP. However, the vagina is a complex organ with great demands of functionality, and the perfect match of scaffold, cell, and trophic factor has yet to be found and tested in preclinical studies. Important issues such as safety and economy must also be addressed before this approach is ready for clinical studies.

Ventral hernia repair with synthetic, composite, and biologic mesh: characteristics, indications, and infection profile

BACKGROUND

A variety of mesh materials are available for ventral hernia repair (VHR), each with a unique set of characteristics. Surgeons are offered an ever-expanding selection of products, making a review of the available materials timely.

METHODS

Current surgical literature is reviewed to describe the different types of synthetic mesh, the indications for the use of each type, their relative risks of infection, and other benefits and shortcomings. We also review clinical studies demonstrating outcomes, efficacy, and use of the meshes in different surgical settings, including laparoscopic hernia repair and special situations such as infection or large abdominal wall defects.

RESULTS

Three main types of prosthetic mesh are available. Synthetic mesh, such as polypropylene (PP) or polyester, is characterized by high tensile strength and vigorous tissue ingrowth, but is unsuitable for intra-abdominal placement because of its tendency to induce bowel adhesions. Composite, or barrier-coated, mesh is a dual-sided prosthetic having a synthetic parietal side to promote a strong repair and a visceral surface that repels tissue ingrowth and decreases adhesion formation. Biologic mesh is a collagen-based human, porcine, or bovine scaffold that may be implanted in the extra- or intra-peritoneal position. Biologic mesh is used frequently in the setting of infected or contaminated surgical incisions.

CONCLUSIONS

Synthetic PP mesh is an appropriate, durable material for extra-peritoneal placement in uncomplicated, clean VHR. Expanded polytetrafluoroethylene and composite meshes are suitable for intraperitoneal placement during laparoscopic VHR. Biologic meshes may be appropriate for contaminated fields or other special situations, but there is no consensus on when or how to use them.

Complications following the use of alloplastic materials in urogynecological surgery

STUDY DESIGN

118 patients, who were admitted from 2005 to 2008 to our department due to complications following mesh implantation, were included in a retrospective survey. We investigated patient symptoms, findings and subsequent patient management. There was a re-evaluation of symptoms in a follow-up eight weeks after the revision procedure. Data from our urogynecological file archive were used.

RESULTS

The main complaints were de novo urgency, pain and recurrent urinary tract infections. The main findings were mesh erosion and infections including abscess formations and osteomyelitis. Before being admitted to our department, 42 patients (35.6%) had already undergone at least one intervention. Surgery to overcome complications was performed in our unit after an average time of 27 months. In most cases, mesh removal was necessary.

CONCLUSIONS

Surgeons need to be aware of potential mesh complications, which should be managed in referral centres as soon as symptoms arise and should be documented in registers. There is a need for more prospective randomised studies on complications arising from surgery.