Karsten Junge

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.

PVDF as a new polymer for the construction of surgical meshes

Abdominal hernia repair is the most frequently performed operation in surgery. Mostly due to lowered recurrence rates mesh repairs in hernia surgery have become an integral component despite increasing mesh-related complications. Current available mesh prosthesis are made of polypropylene (PP). polyethylene-terephtalat or polytetrafluorethylene. though all of them reveal some disadvantages. The introduction of new materials seems to be advisable. Caused by supposed advantageous textile properties and tissue response two mesh modifications made of polyvinylidene fluoride (PVDF) for abdominal hernia repair were developed. In the present study the PVDF meshes were compared to a common heavy weight PP-mesh (Prolene) in regard to functional consequences and morphological tissue response. After implantation in rats as inlay for 3, 14, 21, 42 and 90 days abdominal wall mobility was recorded by three-dimensional photogrammetry. Tensile strength of the suture zone and the mesh itself were determined. Explanted tissue samples have been investigated for their histological reaction in regard to the inflammatory infiltrate. vascularisation, connective and fat tissue ingrowth. Number of granulocytes, macrophages, fibroblasts, lymphocytes and foreign giant body cells have been evaluated to reflect quality of tissue response. The cellular response was grasped by measurement of DNA strand breaks and apoptosis (TUNEL), proliferation (Ki67) and cell stress (HSP70). Analyzing the results confirmed that construction of hernia meshes made of PVDF could be an advantageous alternative to the commonly used materials due to an improved biostability. lowered bending stiffness and a minimum tissue response.

Functional and morphologic properties of a modified mesh for inguinal hernia repair.

Inguinal hernia repair is one of the most frequently performed operations. Next to conventional techniques, open and laparoscopic tension-free methods using mesh implants to reinforce the abdominal wall are increasingly carried out, even becoming the standard procedure in many countries. Because of the benefits of material-reduced meshes for incisional hernia repair, a new mesh modification for tension-free inguinal hernia repair has been developed. In the present study this new low-weight mesh (Vypro II) made of polypropylene and polyglactin multifilaments was compared to a common heavy-weight polypropylene mesh (Prolene) regarding their functional consequences and the morphologic tissue response. After implantation in rats as an inlay, abdominal wall mobility was recorded by three-dimensional photogrammetry and the tensile strength of the suture zone and the mesh itself was measured at 3, 21, and 90 days. Explanted tissue samples have been investigated for their histologic reaction in regard to the inflammatory infiltrate, vascularization, and connective and fat tissue ingrowth. Numbers of granulocytes, macrophages, fibroblasts, lymphocytes, and foreign giant body cells have been evaluated to reflect the quality of the tissue response. The cellular response was assessed by measuring DNA strand breaks and apoptosis (TUNEL), proliferation (Ki67), and cell stress (HSP70). The results indicated that restriction of abdominal wall mobility was significantly reduced with Vypro II compared to that seen with heavy-weight mesh modification, and the inflammatory reaction and connective tissue formation were markedly diminished. Apoptosis and cell proliferation showed considerably lowered levels, and expression of cytoprotective HSP70 was significantly increased. The present study thus confirms the benefits of material-reduced mesh modifications. The new low-weight mesh (Vypro II) could be advantageous in inguinal hernia repair.RésuméLa cure de hernie inguinale est une des interventions les plus pratiquées en chirurgie. A coté des techniques conventionnelles, par voie inguinale ouverte, et sous laparoscopic, des méthodes de cure sans tension, par l’intermédiaire des prothèses pour renforcer la paroi abdominale, sont pratiquées de plus en plus souvent, devenant même le standard dans beaucoup de pays. En raison des bénéfices de ce matériel, on a dévélopé une nouvelle prothèse pour la cure sans tension des hernies inguinales (Vypro II). Dans cette étude, la nouvelle prothèse à poids peu élevé (Vypro II), faite de polypropylene et de multifilaments de polyglactine, comparé à une prothèse de polypropylene ordinaire à poids élevé (Prolene) en ce qui concerne les conséquences fonctionnelles et la réponse morphologiques tissulaires. Après implantation «inlay» de la prothèse chez des rats pendant 3, 21, et 90 jours, la mobilité abdominale a été analysée en trois dimensions par photogrammétrie et on a mesuré la force de rupture entre la zone anastomotique et la prothèse. On a pratiqué un examen histologique des tissus expiantes explorant la réaction histologique eu égard à l’importance de Pinfiltrat inflammatoire, la vascularisation et l’incorporation des tissu adipeux. Le nombre de granulocytes, de macrophages, de fibroblastes, de lymphocytes et de cellules géantes en rapport avec un corps étranger a été évalué pour la qualité de la réponse tissulaire. La réponse cellulaire a été mesurée par le nombre de cassures des filaments d’ADN et le taux d’apoptose (TUNEL), la prolifération (KJ67) et le stress (HSP70) cellulaires. En analysant les résultats, la restriction de la mobilité de la paroi abdominale a été significativement réduite par rapport aux réparations par prothèse à poids élevé: la réaction inflammatoire et la formation de tissu conjonctif ont été très diminuée. L’apoptose et la prolifération cellulaire étaient considérablement plus basses alors que l’expression de la HSP70 cytoprotective a été significativement augmentée. Pour conclure, l’étude présente confirme les bénéfice des modifications de la prothèse. La nouvelle modification de la prothèse, à bas poids (Vypro II), pourrait être intéressante pour la cure de hernie inguinale.ResumenLa operación quirúrgica más frecuente es la herniorrafiahernioplastia inguinal. Junto a las técnicas convencionales con cirugía abierta o laparoscópica, la herniorrafia sin tensión mediante el empleo de prótesis, que refuerzan la pared abdominal, se emplean cada vez mas e incluso, en algunos países, estas son las técnicas utilizadas de forma estándar. Con motivo de los buenos resultados obtenidos en el tratamiento de las eventraciones con mallas estructuradas con escaso material, se ha desarrollado una nueva malla modificada (Vypro II) para la hernioplastia sin tensión de las hernias inguinales. En el presente estudio, se efectúa un estudio comparativo, entre esta nueva malla de bajo peso (Vypro II) compuesta de prolipropileno y poliglactin multifilamentoso y la malla de gran peso, utilizada habitualmente, compuesta por polipropileno (Prolene), por lo que a las respuestas funcionales y morfológicas texturales de ambos implantes se refiere. Tras su implantación “in-lay” en ratas, se estudió a los 3, 21, y 90 días la movilidad de la pared abdominal por medio de un fotográmetro tridimensional, así como la fuerza de tensión en la zona de sutura y en la misma malla; muestras explantadas de tejido se estudiaron histológicamente para valorar la reacción inflamatoria, vascularización y crecimiento, dentro de la malla, de tejido conjuntivo y graso. Para evaluar la calidad de la respuesta textural, se efectuó un recuento del número de granulocitos, macrófagos, fibroblastos, linfocitos y células gigantes a cuerpo extraño. La respuesta celular se trató de valorar midiendo: las soluciones de continuidad del ADN catenario y la apóptosis (TUNEL), la proliferación (Ki67) y agresión celular (HSP70). El análisis de los resultados demuestra que la restricción de la movilidad de la pared abdominal es significativamente menor que la observada utilizando mallas de elevado peso: la reacción inflamatoria y la formación de tejido conjuntivo fue marcadamente menor. La apóptosis y proliferación celular alcanzó niveles muy bajos y la expresión citoprotectora HSP70 aumentó significativamente. En conclusión: el presente estudio confirma el efecto beneficioso por lo que a la reducción de material, que se emplea en la confección de la malla, atañe. La nueva modificación de una malla de bajo peso (Vypro II) tiene muchas ventajas para el tratamiento quirúrgico de las hernias inguinales.

Mesh Implants in Hernia Repair Inflammatory Cell Response in a Rat Model

Background: In the reinforcement of the abdominal wall with mesh implants, various complications including hernia recurrence, abdominal pain, seroma formation and infection are discussed to depend on the biocompatibility of the alloplastic prosthesis. Particularly macrophages, T-cells and mast cells have been shown to play a major role in the inflammatory response to biomaterials. To approach biocompatibility of surgical meshes we therefore examined the infiltrate of these cells as well as the proliferation rate in response to different clinically applied materials. Materials and Methods: Three mesh materials (polypropylene: PP, Prolene®; polyethylene terephthalate: PET, Mersilene®, and polypropylene/polyglactin: PP + PG, Vypro®) were compared after inlay implantation in a standardized rodent animal model. A suture-closed laparotomy served as control. After 7 and 90 days of implantation, histochemical analysis of the inflammatory response to all biomaterials was performed: macrophages (ED3), T-cells (CD3), proliferating cells (PCNA) and mast cells (Giemsa) were investigated. Results: In all groups a persisting T-cell response was observed. Colonization of the interface with macrophages showed a pronounced reduction in the PP + PG-mesh group. Infiltration of mast cells at the tissue graft interface showed a time-dependent decrease in the PET- and PP + PG-mesh groups, whereas in contrast, index of mast cells increased in the PP-mesh group. At both time points, indices of proliferation were highest in the PP-mesh group. Conclusion: The present data confirm the development of a biomaterial-dependent chronic inflammatory response to surgical meshes with macrophages as the predominant cell type. Further research on the recruitment of inflammatory cells and in particular on the role of mast cells and their granular products should be encouraged.

Analysis of collagen-interacting proteins in patients with incisional hernias.

BackgroundIn recent years a disorder of the collagen metabolism has been suggested for the pathogenesis of abdominal wall hernias. Previous investigations of skin specimens revealed a reduction in the collagen I/III ratio and alterations in matrix metalloproteinases in patients with incisional hernias. We investigated known collagen-interacting proteins to further characterize connective tissue in these patients.Patients and methodsSkin scars from patients with either primary or recurrent incisional and recurrent inguinal hernias, as a subgroup of incisional hernias, were analyzed for overall collagen content and for the distribution of collagen types I and III by crosspolarization microscopy. The expression of collagen type V, collagen receptor discoidin domain receptor 2, matrix metalloproteinase 1, connective tissue-like growth factor, and tenascin was determined by immunohistochemistry. Mature abdominal skin scars from patients without evident hernia served as controls.ResultsPatients with recurrent incisional hernia showed lowest ratios of collagen types I to III. Contents of overall collagen and of collagen type V did not differ between the groups. In patients with either primary or recurrent incisional hernias the proportion of collagen receptor discoidin domain receptor 2 positive cells was increased. Matrix metalloproteinase 1 expression was more pronounced in patients with recurrent incisional or inguinal hernias than in controls. Connective tissue-like growth factor was significantly increased in recurrent inguinal hernia patients. The expression of tenascin was notably decreased in all hernia groups.ConclusionsThe observed alterations in the expression of collagen-interacting proteins again indicate the possibility of a fundamental connective tissue disease as the causal factor in the pathogenesis of (recurrent) incisional hernias.

Influence of polyglecaprone 25 (Monocryl) supplementation on the biocompatibility of a polypropylene mesh for hernia repair

Background: Supplementary polyglecaprone 25 (Monocryl) monofilaments were added to a lightweight pure monofilament polypropylene mesh (PP mesh) to improve intraoperative handling (PP+M mesh). This study was designed to evaluate the influence of this additional supplementation on the biocompatibility in a rodent animal model.Methods: Two mesh materials, a composite mesh (PP+M) and the pure polypropylene variant (PP), were compared after subcutaneous implantation in a standardized rat model. Histological analysis of the inflammatory response was performed after 28, 56 and 84 days of implantation. Material absorption, inflammatory tissue reaction, fibrosis and granuloma formation were investigated, as well as the percentage of proliferating and apoptotic cells at the interface.Results: Both mesh materials showed a slight foreign body reaction involving mainly macrophages and foreign body giant cells. Total absorption of the Monocryl filaments of the PP+M mesh occurred between 56 and 84 days of implantation. Both the inflammatory and the fibrotic reaction were decreased (n.s.) in the PP+M mesh group compared to the pure PP mesh. Whereas the percentage of proliferating cells showed no significant difference, the rate of apoptotic cells was significantly decreased in the PP+M mesh group over the whole implantation period.Conclusion: Compared to the pure polypropylene mesh, our data confirm that the use of a polypropylene mesh supplemented with absorbable Monocryl filaments is feasible without additional short-term mesh-related complications in the experimental model or negative side effects on biocompatibility.

A role for the collagen I/III and MMP-1/-13 genes in primary inguinal hernia?

BackgroundAbnormal collagen metabolism is thought to play an important role in the development of primary inguinal hernia. This is underlined by detection of altered collagen metabolism and structural changes of the tissue in patients with primary inguinal hernia. However, it is still unknown whether these alterations reflect a basic dysfunction of the collagen synthesis, or of collagen degradation.MethodsIn the present study, we analysed type I and type III procollagen messenger ribonucleic acid (mRNA) and MMP-1 and MMP-13 mRNA in cultured fibroblasts from the skin of patients with primary inguinal hernia, and from patients without hernia (controls) by reverse transcription polymerase chain reaction (RT-PCR) and Northern Blot.ResultsThe results indicated that the ratio of type I to type III procollagen mRNA was decreased in patients with primary hernia, showing significant differences as compared to controls (p = 0.01). This decrease was mainly due to the increase of type III procollagen mRNA. Furthermore, RT-PCR analysis revealed that the expression of MMP-1 mRNA in patients with primary hernia is equivalent to that of controls (p > 0.05). In addition, MMP-13 mRNA is expressed neither in patients with primary hernia nor in controls.ConclusionWe concluded that abnormal change of type I and type III collagen mRNAs contribute to the development of primary inguinal hernia, whereas the expressions of MMP-1 and MMP-13 mRNA appears not to be involved in the development of primary inguinal hernia. Thus, the knowledge on the transcriptional regulation of collagen in patients with primary inguinal hernia may help to understand the pathogenesis of primary inguinal hernia, and implies new therapeutic strategies for this disease.

Influence of Mesh Materials on Collagen Deposition in a Rat Model

Alterations of the extracellular matrix (ECM) with its major component collagen are increasingly discussed as possible risk factors implicated in the development of abdominal-wall herniation. Because of the widespread use of alloplastic meshes for the surgical repair of hernias, an animal study was performed to analyze the influence of various mesh materials on the quantity and quality of collagen deposition. In 60 male Sprague-Dawley rats an abdominal replacement was performed using three different kinds of mesh materials: polyester (PE), a pure polypropylene (PP), and a composite mesh made of polypropylene and polyglactin (PG). A simple fascia suture repair served as control. The count of fibroblasts, the collagen/protein ratio, the type I/III collagen ratio, and the ex-pression of basic fibroblast growth factor (b-FGF) at the interface were analyzed after 7, 21, and 90 days. The ratio of collagen to overall protein ( w g/mg) showed significant differences comparing different mesh materials (sham controls 38.44 - 16.33 w g/mg, PE 68.5 - 23.8 w g/mg, PP 101.6 - 32.3 w g/mg, PG 49.6 - 11.6 w g/mg at day 90). The ratio of collagen type I/III increased over time in all groups. However, 90 days after mesh implantation the ratio was always significantly lowered compared to the controls. No significant difference was found comparing different mesh materials. The alteration of the scar composition is closely connected to an increased b-FGF expression. b-FGF and count of fibroblasts highly correlated ( r = .95) and showed significant elevated levels compared to simple suture repair. The results of our study strongly support the notion that wound healing is affected by mesh implantation. The quality of the ECM deposition as determined by collagen type I/III ratio is impaired in general, whereas the quantity of ECM deposition is markedly influenced by the kind of mesh material.

New polymer for intra‐abdominal meshes—PVDF copolymer

PURPOSE Full tissue integration without adhesion formation is still a challenge for intra-abdominal mesh materials. Purpose of this study was to investigate the adhesive potential and fibrocollagenous ingrowth of a polymer blend of polyvinylidene fluoride and hexafluorpropylene (co-PVDF), an established suture material in vascular surgery, when placed as a mesh in the intra-abdominal position. The results were compared with a matching polypropylene (PP) mesh. METHODS In an established rabbit model, mesh implantation was performed by laparoscopy in the intraperitoneal onlay mesh technique. After 7, 21, and 90 days the degree of adhesion formation, foreign body reaction, bridging, and shrinkage of mesh area were investigated. RESULTS In the early phase after 7 and 21 days we found significantly more adhesions for PP, but no differences after 90 days. Analysis of tissue reaction showed a significantly lower fibrotic reaction for co-PVDF. The degree of shrinkage revealed no significant difference. CONCLUSION Large-pore PP and co-PVDF-meshes showed comparable good results in the intra-abdominal position, with a reduced inflammatory tissue reaction for co-PVDF. Large pore meshes should be considered an alternative for the development of intraperitoneal onlay meshes.

Biomechanical analyses of mesh fixation in TAPP and TEP hernia repair

BackgroundReliable laparoscopic fixation of meshes prior to their fibrous incorporation is intended to minimize recurrences following transabdominal preperitoneal hernia repair (TAPP) and totally extraperitoneal repair (TEP) repair of inguinal hernias. However, suture-, tack- and staple-based fixation systems are associated with postoperative chronic inguinal pain. Initial fixation with fibrin sealant offers an atraumatic alternative, but there is little data demonstrating directly whether fibrin-based mesh adhesion provides adequate biomechanical stability for repair of inguinal hernia by TAPP and TEP.MethodsUsing a newly developed, standardized simulation model for abdominal wall hernias, sublay repairs were performed with six different types of commercially available hernia mesh. The biomechanical stability achieved, and the protection afforded by the mesh–hernia overlap, were compared for three different techniques: nonfixation, point-by-point suture fixation, and fibrin sealant fixation.ResultsMesh dislocation from the repaired hernia defect was consistently seen with nonfixation. This was reliably prevented with all six mesh types when fixed using either sutures or fibrin sealant. The highest stress resistance across the whole abdominal wall was found following superficial fixation with fibrin sealant across the mesh types. There was a highly statistically significant improvement in fixation stability with fibrin sealant versus fixation using eight single sutures (p = 0.008), as assessed by the range of achievable peak pressure stress up to 200 mmHg.ConclusionsTo ensure long-term freedom from recurrence, intraoperative mesh–hernia overlap must be retained. This can be achieved with fibrin sealant up to the incorporation of the mesh – without trauma and with biomechanical stability.