A. Öttinger

Modified mesh for Hernia repair that is adapted to the physiology of the abdominal wall

OBJECTIVE To develop a new mesh for hernia repair that is adapted to the physiological forces. DESIGN Animal experiment. SETTING Surgical Department of the RWTH-Aachen. ANIMALS Wistar rats MAIN OUTCOME MEASURES Textile analysis, tensile strength, bending stiffness, histology and morphometry. RESULTS After textile analysis of commercially available meshes in clinical use we defined the physiological forces and constructed a new mesh (Soft Hernia Mesh, SHM) based on a combination of non-absorbable polypropylene and absorbable polyglactin 910. The amount of non-absorbable material could be reduced to < 30% compared with Marlex while still guaranteeing the necessary pulling force of 16 N/cm. Improvements of the hosiery structure improved the symmetrical distribution of the retaining forces in all directions. Compared with the considerable restriction of the abdominal wall mobility by Prolene (polypropylene) and Mersilene (polyester) meshes there was no increase in the bending stiffness after the implantation of the new mesh. Histological examination showed a pronounced reduction of the inflammatory reaction in the tissues, and the collagen bundles were orientated merely around the mesh filaments instead of forming a scar plate that completely embedded the mesh. CONCLUSION Different meshes caused specific histological reactions with changes of their mechanical properties after implantation in rodents. A new mesh with a reduced amount of polypropylene showed both less inflammation and less restriction in the mobility of the abdominal wall though it exceeded the required tensile strength of 16 N/cm.

Shrinking of Polypropylene Mesh in vivo: An Experimental Study in Dogs

OBJECTIVE To assess the extent of shrinkage of meshes used for hernia repair. DESIGN Experimental study in dogs. SETTING University hospital, Germany and University Research Centre, Moscow. ANIMALS 10 dogs had monofilament polypropylene meshes that weighed 95 g/m2 (Marlex) or multifilament reduced polypropylene meshes combined with polyglactin 910 that weighed 55 g/m2 (Soft Hernia Mesh) implanted for either 3 or 6 months. MAIN OUTCOME MEASURES Histological appearance and radiological assessment of the position and area of the mesh. RESULTS After 4 weeks the area of mesh in the monofilament group was reduced from to 139 (11) to 75 (8) cm2 (54%) and that of the multifilament from 116 (18) to 77 (20) cm2 (66%). The multifilament mesh with the reduced amount of polypropylene showed less inflammatory response and less shrinkage. The mesh did not seem to have moved. CONCLUSION Meshes that contain a lot of polypropylene shrink to about 30%-50% of their original size after 4 weeks, requiring an overlap of at least 3 cm if implanted subfascially. Reduction in the polypropylene content decreases both the inflammatory response and the shrinkage. Meshes with big pores are less likely to fold and improve compatibility.

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.

The Influence of Inguinal Mesh Repair on the Spermatic Cord: A Pilot Study in the Rabbit

The permanent implantation of a polypropylene mesh during inguinal hernia repair causes chronic inflammatory changes in the surrounding tissue. We investigated the effect of this foreign body reaction on the structures of the spermatic cord in the rabbit. Eight Chinchilla rabbits underwent unilateral inguinal hernia repair by the Lichtenstein technique using Marlex (n = 4) orUltrapro (n = 4) mesh. The contralateral side was operated upon using the Shouldice repair. Three animals served as controls. Three months after operation we analyzed testicular size, testicular temperature, and arterial perfusion by excitation light of a 780-nm laser after injection of 0.5 mg/kg indocyanin green. Histological evaluation included spermatogenesis (Johnsen score) and foreign-body reaction. Testicular volume increased about 10% after each operation. The decrease of arterial perfusion and testicular temperature was more significant after mesh repair than following Shouldice operation. After mesh implantation we found fewer seminiferous tubules classified as Johnsen 10 (Marlex: 51.3%, Ultrapro: 45.0%) than after Shouldice repair (63.8%) or in the controls (65.8%). The spermatic cord showed a typical foreign-body reaction at the interface between mesh and surrounding tissue, which was not detectable after Shouldice repair. Preserved cremasteric muscle fibers protected the structures of the spermatic cord. The inflammatory foreign-body reaction of the surrounding tissue induced by the inguinal prosthetic mesh includes the structures of the spermatic cord. This may have an influence also on spermatogenesis. Therefore, we recommend strict indications for implantation of a prosthetic mesh during inguinal hernia repair.

Modification of collagen formation using supplemented mesh materials

BackgroundFormation of recurrent inguinal and incisional hernia shows an underlying defect in the wound healing process. Even following mesh repair an altered collagen formation and insufficient mesh integration has been found as main reason for recurrences. Therefore the development of bioactive mesh materials to achieve a local modification of the scar formation to improve patients outcome is advisable.MethodsThirty-six male Wistar rats were used within this study. A Mersilene ® mesh sample was implanted after midline skin incision and subcutaneous preparation. Before implantation mesh samples were incubated for 30 minutes with either one of the following agents: doxycycline, TGF-beta 3, zinc-hydrogeneaspartate, ascorbic acid, hyaluronic acid. Incubation with a physiologic 0.9 % NaCl solution served as control. Seven and 90 days after mesh implantation 3 animals from each group (n = 6) were sacrificed for morphological observations. Collagen quantity and quality was analyzed measuring the collagen/protein as well as the collagen type I/III ratio.ResultsFollowing an implantation interval of 90 days supplementation with doxycycline (39.3 ± 7.0 µg/mg) and hyaluronic acid (34.4 ± 5.8 µg/mg) were found to have a significantly increased collagen/protein ratio compared to implantation of the pure Mersilene ® mesh samples (28.3 ± 1.9 µg/mg). Furthermore, an overall increase of the collagen type I/III ratio was found in all groups indicating scar maturation over time. However, no significant differences were found after 7 and 90 days of implantation comparing collagen type I/III ratio of supplemented mesh samples and control group.ConclusionsIn summary, we found an influence of supplemented mesh materials on collagen deposition. However, the investigated bioactive agents with reported influence on wound healing were not associated with an improved quality in scar formation.

Zinc deficiency impairs wound healing of colon anastomosis in rats

BackgroundAnastomotic leakage is a relevant surgical complication. The aim of the study was to investigate the influence of a controlled preoperative zinc deficiency on the extracellular matrix composition of colon anastomosis.Materials and methodsForty male Wistar rats were randomized to either a zinc deficiency group (n = 20) or a control group (n = 20). In each animal, a transverse colonic end-to-end anastomosis was performed. On postoperative day 7, the surface of the mucosal villi, expression of matrix metalloproteinases (MMP) 2, 8, 9, and 13, and both the number of proliferating cells (Ki67) and apoptotic cells, as well as the collagen types I/III ratio were analyzed. Within the anastomotic area the mesenterial region and the antimesenterial region were analyzed separately.ResultsIn each group, one anastomotic leakage was detected. Expression of both MMP 2, 9, and 13 was significantly higher, and expression of Ki67 was significantly reduced in the zinc deficient group both mesenterial and antimesenterial. The collagen types I/III ratio was reduced in the zinc deficiency group by trend, without statistical significance neither mesenterial nor antimesenterial. Likewise, zinc deficiency affected neither the expression of MMP 8 nor the rate of apoptotic cells, respectively. Analyses of the surface of the mucosal villi revealed no significant differences comparing the groups with neither mesenterial nor antimesenterial.ConclusionsOur study constitutes the known negative effect of zinc deficiency on wound healing. Zinc deficiency significantly increased the activity of MMPs (2, 9, and 13), caused a reduced collagen type I/III ratio, and delayed cell proliferation and quality of intestinal wound healing.

Influence of Postoperative Epidural Analgesia with Bupivacaine onIntestinal Motility, Transit Time, and Anastomotic Healing

Epidural application of bupivacaine hasbeen suggested to have a sympatholytic effect on spinal reflexmechanisms that shortens postoperative paralysis and leads to animproved transit time. The influence on anastomitic healing remainscontroversial. Laparotomy was performed in eight dogs. A short segmentof the distal colon was resected and five electrodes were fixed on theserosa to measure the myoelectric activity (e.g., Migrating MyoelectricComplex—MMC). After operation a peridural catheter was placed betweenL7 and the sacral crest. One milliliter of bupivacaine 0.25% for each3 kg of body weight was injected every 4 hours. Barium pellets coatedin wax were placed into the stomach to allow radiographicrepresentation of transit time. After 5 days the colon anastomosis wasresected to measure the bursting pressure. In the peridural analgesiagroup (PDA) we found one small bowel intussusception and one coveredanastomotic leakage. Postoperative PDA led to early and severemyoelectric activity but did not influence the time until the first MMCoccurred (44 ± 0.8 h, PDA; 44.6 ± 1.5 h,control). Neither the transit time to the colon (50.2 ± 1.9h, PDA; 51.7 ± 5.5 h, control) nor the anastomotic healingwas influenced (bursting pressure: 176 ± 21.1 mmHg, PDA; 152± 27.7 mmHg, control). Postoperative epidural analgesia withbupivacaine shortens intestinal paralysis. Early myoelectric activitywith a lack of propulsive activity can cause complications like smallbowel intussusception. Hence early postoperative enteral nutritionafter epidural analgesia is risky. Because the influence of epiduralanalgesia on propulsive motility remains unclear, it seems reasonableto recommend its limited use in colon surgery.

Colon interposition for esophageal replacement: isoperistaltic or antiperistaltic? Experimental results

BACKGROUND Isoperistaltic colon is preferred to antiperistaltic colon for esophageal replacement, but experimental data do not exist to support this practice. METHODS In 7 dogs a 20 cm long colon loop was interposed between the skin and the small bowel, isoperistaltically in 3 dogs and antiperistaltically in 4 dogs. Three months later five strain-gauges were implanted and evacuation was investigated by motility testing, barium studies, and scintigraphy. RESULTS Motility recording showed normal colon motility in the excluded loops. Quiescent states (duration 40.2 +/- 13.6 minutes) were followed by contractile states (duration 7.5 +/- 2.4 minutes, frequency 3.3 +/- 0.6 per minute). The main peristaltic direction of isoperistaltic loops was isoperistaltic, and the main peristaltic direction of antiperistaltic loops was antiperistaltic. Evacuation took place exclusively during the contractile status. Half time emptying was more rapid in isoperistaltic loops (35 +/- 11 vs 69 +/- 16 minutes). The content of antiperistaltic loops was held back by antiperistaltic activity. Application of oatmeal porridge into the loops shortened the quiescent status from 40.2 to 13.2 +/- 4.8 minutes. CONCLUSIONS The colon graft for esophageal replacement is an active system. Food is stored during the quiescent states and evacuated during the contractile states. The original peristaltic direction is preserved so that retroperistalsis in antiperistaltic loops may lead to patient discomfort and pulmonary complications.

Laparoskopie versus laparotomie

We performed laparoscopy (n = 7) or laparotomy (n = 7) for exploration of the small intestine, cecal resection with Endo-GIA or TA-30, deserosation of 2 cm2 of the abdominal wall and resection of the omenturn majus in dogs. After 8 days all dogs were re-examined and the adhesions were quantified by computer-aided measurement. Laparoscopic operations were followed by significantly (P < 0.001) fewer adhesions. After conventional operations extensive adhesions to the abdominal incision and interenteric adhesions were found, together with frequent conglomerates of adhesions, intestinal kinkings or adhesive bands. Identical manipulations, such as cecal resection or deserosation of the lateral abdominal wall, led to the same frequency and severity of adhesions in both groups. Based on our results, the risk of adhesion-related complications may be reduced by the laparoscopic approach.ZusammenfassungAn Hunden wurden laparoskopisch (n = 7) bzw. per Laparotomie (n = 7) nach Exploration des Dünndarms eine Zäkalpolresektion mit Endo-GIA bzw. TA-30 durchgeführt, 2 cm2 der lateralen Bauchwand deserosiert und ein Netzzipfel reseziert. Am B. postoperativen Tag wurden alle Tiere relaparotomiert und die entstandenen Adhäsionen rechnergestützt vermessen. Das Ausmaß der Adhäsionen nach laparoskopischen Eingriffen war signifikant (P < 0,01) geringer. Ausgedehnte Adhäsionen zur Laparotomiewunde und zwischen den Darmschlingen bedingten größere Adhäsionsflächen nach Laparotomie. Konglomeratadhäsionen, adhäsionsbedingte Darmabknickungen und Briden fanden sich häufiger nach konventionellen Operationen. Identische Manipulationen wie Zäkalresektion und Deserosierung der lateralen Bauchwand führten nach laparoskopischen und konventionellen Eingriffen zum gleichen Adhäsionsausmaß. Aufgrund unserer Ergebnisse ist das Risiko adhäsionsbedingter Komplikationen nach laparoskopischen Operationen insgesamt geringer als nach identischen konventionellen Eingriffen einzuschätzen.

Large-Pore PDS Mesh Compared to Small-Pore PG Mesh

ABSTRACT Background: Currently, absorbable meshes are used as temporary closure in case of laparostoma. Unfortunately the multifilament polyglycolic acid (PG) meshes with small pores reveal little elasticity acting rather as a fluid barrier than permitting drainage of intra-abdominal fluids. Therefore, a new mesh was constructed of absorbable polydioxanon monofilaments (PDS) with increased porosity and longer degradation time. Material and Methods: For evaluation of the tissue response the new PDS mesh was implanted as abdominal wall replacement in each five rats for 7, 21, or 90 days, respectively, and compared to a PG mesh. Histological analysis included HE staining with measurement of the size of the granuloma and immunoshistochemistry for TUNEL, Ki67, TNF-R2, MMP-2, YB1, FVIII, gas6, AXL. Parameters for neovascularization and nerve ingrowth were analyzed. Results: The inflammatory and fibrotic tissue reaction is attenuated with PDS in comparison to PG, e.g., the size of the granuloma was smaller with less cell turnover, and less remodeling as represented by, e.g., reduction of apoptosis, expression of MMP-2, or TNF-R2. The number of ingrowing nerves and vessels explored via AXL, gas6, and factor VIII was increased in the PDS mesh. Conclusion: The results from the present investigation showed that a mesh can be constructed of monofilament PDS that induce significant less inflammatory and fibrotic reaction, however permits fluid drainage and preserves elasticity.