不同聚丙烯网用于乳房下垂矫正的生物力学研究

目的 探讨4种不同的聚丙烯网片的生物力学性能,为真皮帽法乳房缩小术中内置式乳罩的选择提供依据.方法 以实验用小型猪作动物模型,将4种不同的聚丙烯网埋置于腹部皮下,90 d后采集标本,比较其生物力学性能.结果 4种聚丙烯网在拉伸强度、应力-应变关系、应力松弛和蠕变4个方面显示出不同的生物力学特性,这显然与它们所采用的材料和编织结构不同有关.结论 应力松弛和蠕变作为网片特殊的生物力学特性在维持术后乳房正常形态上有重要意义,在内置式乳罩的选择标准中占有重要的地位.Premilene Mesh LP~(R)作为新型的轻重量、小孔径网片,在生物力学性能上优于其他网片.     

Anisotropic evaluation of synthetic surgical meshes

Introduction  

The material properties of meshes used in hernia repair contribute to the overall mechanical behavior of the repair. The anisotropic potential of synthetic meshes, representing a difference in material properties (e.g., elasticity) in different material axes, is not well defined to date. Haphazard orientation of anisotropic mesh material can contribute to inconsistent surgical outcomes. We aimed to characterize and compare anisotropic properties of commonly used synthetic meshes.     

Biomechanical properties of raw meshes used in pelvic floor reconstruction

Female urinary incontinence and pelvic organ prolapse are common conditions. The aim of this study was to assess the biomechanical properties of raw meshes commonly used in pelvic floor surgery, particularly the effects of cyclical loading on these meshes. The material properties of nine different types of surgical meshes were examined using uniaxial tensile tests. The strength and extensibility of the mesh designs differed considerably. Most mesh types exhibited curvilinear loading curves. Cyclical loading of mesh samples produced significant permanent deformation in all mesh designs. This non-recoverable extension ranged from about 8.5% to 19% strain. Hysteresis also varied considerably between materials from 30% to 85%. All mesh groups tested for their biomechanical properties displayed differences in results for failure load, stiffness, non-recoverable extension and hysteresis.     

Experimental comparison of type of Tissucol dilution and composite mesh (Parietex) for laparoscopic repair of groin and abdominal hernia: observational study conducted in a university laboratory

Purpose The primary objective of this observational study was to determine the best possible dilution of fibrin glue (Tissucol) to employ for prosthesis fixing in laparoscopic treatment of abdominal wall defects and, secondly, to assess its feasibility and safety. Materials and methods This study was carried out in a university experimental animal laboratory in accordance with all international laws, ethics regulations and quality criteria associated with animal experiments. The tests were carried out on two pigs, using four samples of mesh (Parietex). All meshes were fixed using two different Tissucol dilutions (standard with distilled water and that with calcium chloride). Follow-up evaluations were at 15 days after 30 days, with the latter consisting of traction tests and a biopsy for histological analysis. Results No post-operative complications were observed. The collagen-coated polyester meshes showed 0% adhesions, and reperitonealization had ensued after 15 days. We saw no shrinkage or migration of any of the meshes. Histopathological analyses confirmed a greater stability, greater tissue integration and the largest number of fibroblasts in meshes fixed with a 1/10 Tissucol dilution without calcium chloride. Conclusions This observational study using animals showed that the 1/10 standard dilution – not that with calcium chloride – provided the best fixation and integration and prevented the formation of intraperitoneal adhesions, provided a hydrophilic collagen film-covered mesh was used.     

A bioresorbable molding mesh for impaction grafting revision hip surgery

Impacted morselized allografts are used to treat bone loss in revision surgery. This technique depends on adequate mechanical support of the graft. Metal support devices function well, but there are disadvantages associated with the use of steel meshes. In this cadaveric, surgical simulation model we investigated the surgical and mechanical suitability of a bioresorbable molding mesh for use in impaction grafting revision surgery. Surgical feasibility was assessed, and mechanical deformation of the mesh during the surgical procedure and postoperative cyclic loading of the specimens were measured with strain gauges. All meshes were surgically usable. The exterior surface deformation of the meshes during the surgical procedure and postoperative mechanical loading did not exceed 4500 microm/m, although the meshes were not damaged in a four-point bending test in which deformations higher than 19,000 microm/m were reached. Therefore, results of this study suggest that this type of bioresorbable mesh seems to have sufficient initial mechanical properties to warrant additional preclinical in vivo study.     

An Energy-Preserving Wavelet Collocation Method for General Multi-Symplectic Formulations of Hamiltonian PDEs

In this paper, we develop a novel energy-preserving wavelet collocation method for solving general multi-symplectic formulations of Hamiltonian PDEs. Based on the autocorrelation functions of Daubechies compactly supported scaling functions, the wavelet collocation method is conducted for spatial discretization. The obtained semi-discrete system is shown to be a finite-dimensional Hamiltonian system, which has an energy conservation law. Then, the average vector field method is used for time integration, which leads to an energy-preserving method for multi-symplectic Hamiltonian PDEs. The proposed method is illustrated by the nonlinear Schrödinger equation and the Camassa-Holm equation. Since differentiation matrix obtained by the wavelet collocation method is a cyclic matrix, we can apply Fast Fourier transform to solve equations in numerical calculation. Numerical experiments show the high accuracy, effectiveness and conservation properties of the proposed method.     

Comparison of a lightweight polypropylene mesh (Optilene® LP) and a large-pore knitted PTFE mesh (GORE® INFINIT® mesh)—Biocompatibility in a standardized endoscopic extraperitoneal hernia model

Purpose  

The use of a mesh with good biocompatibility properties is of decisive importance for the avoidance of recurrences and chronic pain in endoscopic hernia repair surgery. As we know from numerous experiments and clinical experience, large-pore, lightweight polypropylene meshes possess the best biocompatibility. However, large-pore meshes of different polymers may be used as well and might be an alternative solution.     

Which mesh for hernia repair?

INTRODUCTION

The concept of using a mesh to repair hernias was introduced over 50 years ago. Mesh repair is now standard in most countries and widely accepted as superior to primary suture repair. As a result, there has been a rapid growth in the variety of meshes available and choosing the appropriate one can be difficult. This article outlines the general properties of meshes and factors to be considered when selecting one.

MATERIALS AND METHODS

We performed a search of the medical literature from 1950 to 1 May 2009, as indexed by Medline, using the PubMed search engine (<http://www.pubmed.gov>). To capture all potentially relevant articles with the highest degree of sensitivity, the search terms were intentionally broad. We used the following terms: ‘mesh, pore size, strength, recurrence, complications, lightweight, properties’. We also hand-searched the bibliographies of relevant articles and product literature to identify additional pertinent reports.

RESULTS AND CONCLUSIONS

The most important properties of meshes were found to be the type of filament, tensile strength and porosity. These determine the weight of the mesh and its biocompatibility. The tensile strength required is much less than originally presumed and light-weight meshes are thought to be superior due to their increased flexibility and reduction in discomfort. Large pores are also associated with a reduced risk of infection and shrinkage. For meshes placed in the peritoneal cavity, consideration should also be given to the risk of adhesion formation. A variety of composite meshes have been promoted to address this, but none appears superior to the others. Finally, biomaterials such as acellular dermis have a place for use in infected fields but have yet to prove their worth in routine hernia repair.     

四种聚丙烯网用于矫正乳房下垂的生物相容性研究

目的探讨外科网片的皱缩和粘连影响其作为内置式乳罩纠正轻、中度乳房下垂的术后效果，通过比较4种不同的聚丙烯网在生物相容性上的差异，找出异物反应与术后效果的关系，以便为内置式乳罩选用聚丙烯网片提供依据。方法以实验用小型诸作为动物模型，将4种不同的聚丙烯网置入腹部皮下，90d后采集标本，比较并发症、肄物反应、胶原纤维与弹力纤维的形成，并在透射电子最微镜下观察超微结构。结果4种聚丙烯网在生物相容性上存存差异。异物反应的程度决定生物相容性的差异，同时对术后乳房形态有显著的影响。结论Premilene Mesh LP作为新型的轻质量网片，生物相容性优于其他网片。     

A Third Order Conservative Lagrangian Type Scheme on Curvilinear Meshes for the Compressible Euler Equations

Based on the high order essentially non-oscillatory (ENO) Lagrangian type scheme on quadrilateral meshes presented in our earlier work [3], in this paper we develop a third order conservative Lagrangian type scheme on curvilinear meshes for solving the Euler equations of compressible gas dynamics. The main purpose of this work is to demonstrate our claim in [3] that the accuracy degeneracy phenomenon observed for the high order Lagrangian type scheme is due to the error from the quadrilateral mesh with straight-line edges, which restricts the accuracy of the resulting scheme to at most second order. The accuracy test given in this paper shows that the third order Lagrangian type scheme can actually obtain uniformly third order accuracy even on distorted meshes by using curvilinear meshes. Numerical examples are also presented to verify the performance of the third order scheme on curvilinear meshes in terms of resolution for discontinuities and non-oscillatory properties.     

What is the evidence for the use of biologic or biosynthetic meshes in abdominal wall reconstruction?

Introduction

Although many surgeons have adopted the use of biologic and biosynthetic meshes in complex abdominal wall hernia repair, others have questioned the use of these products. Criticism is addressed in several review articles on the poor standard of studies reporting on the use of biologic meshes for different abdominal wall repairs. The aim of this consensus review is to conduct an evidence-based analysis of the efficacy of biologic and biosynthetic meshes in predefined clinical situations.

Methods

A European working group, “BioMesh Study Group”, composed of invited surgeons with a special interest in surgical meshes, formulated key questions, and forwarded them for processing in subgroups. In January 2016, a workshop was held in Berlin where the findings were presented, discussed, and voted on for consensus. Findings were set out in writing by the subgroups followed by consensus being reached. For the review, 114 studies and background analyses were used.

Results

The cumulative data regarding biologic mesh under contaminated conditions do not support the claim that it is better than synthetic mesh. Biologic mesh use should be avoided when bridging is needed. In inguinal hernia repair biologic and biosynthetic meshes do not have a clear advantage over the synthetic meshes. For prevention of incisional or parastomal hernias, there is no evidence to support the use of biologic/biosynthetic meshes. In complex abdominal wall hernia repairs (incarcerated hernia, parastomal hernia, infected mesh, open abdomen, enterocutaneous fistula, and component separation technique), biologic and biosynthetic meshes do not provide a superior alternative to synthetic meshes.

Conclusion

The routine use of biologic and biosynthetic meshes cannot be recommended.

     

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.     

Polyester meshes and adhesive materials in the brain: comparative research in rats to optimize surgical strategy

OBJECT: The goal of this study was to determine the biocompatibility of polyester mesh electrode carriers for auditory brainstem implants with and without adhesives in a rat model. METHODS: Physical properties of the meshes were evaluated within the fourth ventricle region, both without (Group A) and with adhesives (muscle, Group B; oxidized regenerated cellulose [ORC], Group C; and fibrin glue, Group D). The stability of the mesh position, the healing process, and host defense reaction after 2 to 60 days were examined in series of tissue sections in which meshes were preserved in situ. The cellular reaction was further evaluated using electron microscopy. Although otherwise pliable, polyester meshes were too rigid when used with adhesives, especially fibrin glue or muscle. Also, the sharp edges of the meshes presented a risk of brainstem and cerebellar lesions. Regardless of the material, meshes induced persistent inflammatory tissue reactions characterized by numerous macrophages and foreign-body giant cells. After 14 days, the cellular response had resulted in sufficient fibroblast and collagen fiber encapsulation of the meshes and remained essentially unchanged thereafter. No influence of adhesives on the healing process was observed, and, unexpectedly, these substances did not reduce the risk of dislocation prior to adequate cellular encasement. In some rats in Groups A and C, purulent inflammation, in part with Gram-positive bacteria, occurred after 2 to 14 days. The ORC exhibited persistent swelling, introducing the risk of occlusive hydrocephalus and/or brainstem compression. CONCLUSIONS: Polyester meshes and various adhesives exhibited acceptable biocompatibility in terms of local tissue reaction. Adhesives reduced pliability of the meshes, however, and were ineffective in reducing the risk of dislocation. Handling characteristics could be improved by better mesh designs, and risk of infection could be reduced by both improved designs and surface treatment of the meshes with antibacterial agents.     

Mechanical properties of polypropylene mesh used in pelvic floor repair

The aim of this study was the comparison of the stiffness of different meshes under two types of mechanical tests. Five different mesh types were mechanically tested. The methods used consisted on uniaxial tension test (tensile stiffness) and tape ring tests, experimental continuous compression of the mesh loops (flexural stiffness). The most significant difference of tensile stiffness behaviour appears between Aris™ and TVTO™. From the analysis of the experimental data, we divided the flexural stiffness, in two main groups. The first group includes Auto Suture™ and Aris™ meshes. The two meshes seem to have a similar flexural behaviour. The second group includes TVTO™, Uretex™ and Avaulta™. The difference between these two groups is clearly evident comparing TVTO™ and Aris™. This study shows that there are significant differences on the mechanical properties between urogynecology meshes. An erratum to this article can be found at     

Mesh implants: An overview of crucial mesh parameters

Hernia repair is one of the most frequently performed surgical interventions that use mesh implants. This article evaluates crucial mesh parameters to facilitate selection of the most appropriate mesh implant, considering raw materials, mesh composition, structure parameters and mechanical parameters. A literature review was performed using the Pub Med database. The most important mesh parameters in the selection of a mesh implant are the raw material, structural parameters and mechanical parameters, which should match the physiological conditions. The structural parameters, especially the porosity, are the most important predictors of the biocompatibility performance of synthetic meshes. Meshes with large pores exhibit less inflammatory infiltrate, connective tissue and scar bridging, which allows increased soft tissue ingrowth. The raw material and combination of raw materials of the used mesh, including potential coatings and textile design, strongly impact the inflammatory reaction to the mesh. Synthetic meshes made from innovative polymers combined with surface coating have been demonstrated to exhibit advantageous behavior in specialized fields. Monofilament, largepore synthetic meshes exhibit advantages. The value of mesh classification based on mesh weight seems to be overestimated. Mechanical properties of meshes, such as anisotropy/isotropy, elasticity and tensile strength, are crucial parameters for predicting mesh performance after implantation.     

MRI Evaluation of an Elastic TPU Mesh under Pneumoperitoneum in IPOM Position in a Porcine Model

Background: The frequency of laparoscopic approaches increased in hernia surgery over the past years. After mesh placement in IPOM position, the real extent of the meshes configurational changes after termination of pneumoperitoneum is still largely unknown. To prevent a later mesh folding it might be useful to place the mesh while it is kept under tension. Conventionally used meshes may lose their Effective Porosity under these conditions due to poor elastic properties. The aim of this study was to evaluate a newly developed elastic thermoplastic polyurethane (TPU) containing mesh that retains its Effective Porosity under mechanical strain in IPOM position in a porcine model. It was visualized under pneumoperitoneum using MRI in comparison to polyvinylidenefluoride (PVDF) meshes with similar structure. Methods: In each of ten minipigs, a mesh (TPU containing or native PVDF, 10 × 20 cm) was randomly placed in IPOM position at the center of the abdominal wall. After 8 weeks, six pigs underwent MRI evaluation with and without pneumoperitoneum to assess the visibility and elasticity of the mesh. Finally, pigs were euthanized and abdominal walls were explanted for histological and immunohistochemical assessment. The degree of adhesion formation was documented. Results: Laparoscopic implantation of elastic TPU meshes in IPOM position was feasible and safe in a minipig model. Mesh position could be precisely visualized and assessed with and without pneumoperitoneum using MRI after 8 weeks. Elastic TPU meshes showed a significantly higher surface increase under pneumoperitoneum in comparison to PVDF. Immunohistochemically, the amount of CD45-positive cells was significantly lower and the Collagen I/III ratio was significantly higher in TPU meshes after 8 weeks. There were no differences regarding adhesion formation between study groups. Conclusions: The TPU mesh preserves its elastic properties in IPOM position in a porcine model after 8 weeks. Immunohistochemistry indicates superior biocompatibility regarding CD45-positive cells and Collagen I/III ratio in comparison to PVDF meshes with a similar structure.     

Optimal control of non-linear distributed parameter systems by a finite-element collocation technique

A finite-element collocation technique is proposed for solving non-linear distributed parameter system (DPS) optimal control problems. On each element, two Gaussian collocation points and Hermite approximation functions are used in the finite-element collocation technique. The numerical experience for two non-linear DPS, one involving distributed control and the other involving spatially-independent control, is reported. Optimal control of DPS can be computed with relatively low-order models when this finite-element collocation technique is used.     

Tensile properties of commonly used prolapse meshes

Introduction and hypothesis  To improve our understanding of the differences in commonly used synthetic prolapse meshes, we compared four newer generation meshes to Gynecare PS™ using a tensile testing protocol. We hypothesize that the newer meshes have inferior biomechanical properties. Methods  Meshes were loaded to failure (n = 5 per group) generating load–elongation curves from which the stiffness, the load at failure, and the relative elongation were determined. Additional mesh samples (n = 3) underwent a cyclic loading protocol to measure permanent elongation in response to subfailure loading. Results  With the exception of Popmesh, which displayed uniform stiffness, other meshes were characterized by a bilinear behavior. Newer meshes were 70–90% less stiff than Gynecare™ (p < 0.05) and more readily deformed in response to uniaxial and cyclical loading (p < 0.001). Conclusion  Relative to Gynecare™, the newer generation of prolapse meshes were significantly less stiff, with irreversible deformation at significantly lower loads.     

High-Order Positivity-Preserving Well-Balanced Discontinuous Galerkin Methods for Euler Equations with Gravitation on Unstructured Meshes

In this paper, we propose a high-order accurate discontinuous Galerkin (DG) method for the compressible Euler equations under gravitational fields on unstructured meshes. The scheme preserves a general hydrostatic equilibrium state and provably guarantees the positivity of density and pressure at the same time. Comparing with the work on the well-balanced scheme for Euler equations with gravitation on rectangular meshes, the extension to triangular meshes is conceptually plausible but highly nontrivial. We first introduce a special way to recover the equilibrium state and then design a group of novel variables at the interface of two adjacent cells, which plays an important role in the well-balanced and positivity-preserving properties. One main challenge is that the well-balanced schemes may not have the weak positivity property. In order to achieve the well-balanced and positivity-preserving properties simultaneously while maintaining high-order accuracy, we carefully design DG spatial discretization with well-balanced numerical fluxes and suitable source term approximation. For the ideal gas, we prove that the resulting well-balanced scheme, coupled with strong stability preserving time discretizations, satisfies a weak positivity property. A simple existing limiter can be applied to enforce the positivity-preserving property, without losing high-order accuracy and conservation. Extensive one- and two-dimensional numerical examples demonstrate the desired properties of the proposed scheme, as well as its high resolution and robustness.     

三氯生涂层医用聚丙烯抗菌网片的制作和性能研究

目的：探讨三氯生涂层医用抗菌聚丙烯网片的制作，研究其药物的控释性能以及网片上载前后性能。
方法：以三氯生为抗菌剂，乙烯-乙烯醇共聚物为载体，应用溶剂蒸发法，制成三氯生涂层医用抗菌聚丙烯网片。将网片分为A，B，C，D 4组，A，B，C组为三氯生涂层医用抗菌聚丙烯网片实验组，D为对照组。在电镜下观察4组网片的超微结构；测定抗菌网片不同时段的抑菌圈直径；采用浸泡法测定实验前后网片在不同时间段释放药物的抑菌效果；测定实验前后网片在横向和纵向被拉断时所能承受的最大拉力。
结果：实验组网片涂层表面均匀光滑，在生理盐水中能持续释放7 d，在1，3，5，7 d实验组抑菌圈直径明显大于对照组（P＜0.05），两组网片在不同张力下的横向及纵向所能承受的最大拉力无统计学意义。
结论：经溶剂蒸发法制备的三氯生涂层医用抗菌聚丙烯网片具有药物控释性能和明显抗菌性能，而其生物力学性能在实验前后基本不变，为临床处理无张力疝修补术后的人工补片感染问题提供一个新的方法和途经。