A. Lambertz

In vitro and in vivo characteristics of gentamicin‐supplemented polyvinylidenfluoride mesh materials

To reduce infection rates after mesh implantation antibiotic-coated meshes were designed. The aim of the study was to analyze biocompatibility and in vitro efficiency of a modified gentamicin-supplemented polyvinylidenfluoride mesh. Twenty rats were randomized to two groups (PVDF group and Genta group). Mesh material was implanted subcutaneously. Blood samples were taken to determine the gentamicin serum concentration. Seven and 90 days after mesh implantation, animals were euthanized. The inflammatory tissue response was characterized by analyzing the foreign body granuloma. Cellular immune response was analyzed by immunohistochemical investigations. The collagen type I/III ratio was estimated by crosspolarization microscopy. In vitro agar diffusion test, suspension test, and gentamicin release were characterized. Agar diffusion and suspension test showed efficient antibiotic effects of the mesh in vitro. Serum concentrations of gentamicin showed a peak value 1 h postoperatively with a decline within the next day. The total size of the granuloma was significantly smaller in the Genta group compared to the PVDF group at both points of time. Except of a short period of increased expression of CD68 in the Genta group after 7 days, no further difference was found analyzing cellular immune response. The collagen type I/III ratio was widely constant analyzing the two mesh types without significant differences comparing both mesh materials. A significantly decreased foreign body granuloma formation compared to the pure PVDF mesh group was found. In vitro analysis showed efficient antibiotic effects of the Gentamicin supplementation compared to the pure PVDF mesh.

Polyvinylidene Fluoride as a Suture Material: Evaluation of Comet Tail-Like Infiltrate and Foreign Body Granuloma.

Background: Biocompatibility and tissue integration of a surgical suture are decisive factors for wound healing and therefore for the success of sutures. The optimal suture material is still under discussion. Polyvinylidene fluoride (PVDF) is described to have superior properties of biocompatibility and is therefore frequently used as a mesh component. Only little information is available about its use as a suture material. The aim of this study was to evaluate the biocompatibility of PVDF as a suture material in comparison to 5 different established sutures in a rat model. Methods: In 30 male rats, a monofilamental PVDF suture (Resopren®) and 5 established control suture materials [polyester (Miralene®), polytetrafluoroethylene (Gore®), poliglecaprone (Monocryl®), polydioxanone (Monoplus®), polyglactin 910 (Vicryl®), USP size 3-0] were placed in the subcutaneous layer of the abdominal wall without knot or tension. After 3, 7 or 21 days, the abdominal walls were explanted for histopathological and immunohistochemical investigation with special regard to the size and quality of foreign body granuloma and the length of the comet tail-like infiltrate (CTI). Results: The PVDF sutures showed the smallest size of foreign body granuloma (60 ± 14 µm) and the smallest CTI length (343 ± 60 µm) of all polymers after 21 days. Only PVDF (Resopren) and polydioxanone (Monoplus) showed a significant collagen I/III ratio increase between days 3 and 21 (p = 0.009 and p = 0.016). The quality of foreign body reaction regarding inflammation, proliferation and fibrotic remodeling was similar between all suture materials. Conclusions: Our data indicate that monofilamental PVDF sutures show a favorable foreign body reaction with small granuloma sizes and CTI length in comparison to established sutures. Its use as a suture material in general surgery could therefore be extended in the future. To reinforce these findings, further clinical studies need to be conducted.

Laparotomy closure using an elastic suture: A promising approach

BACKGROUND Midline laparotomy wound failure like burst abdomen remains one of the major complications after abdominal surgery. The use of sutures with a closer resemblance to abdominal wall physiology, like elastic threads, could decrease the risk of these complications occurring. Thus, we evaluated the possibility of using a new elastic thread composed of thermoplastic polyurethane (TPU) as a suture for the closure of midline laparotomies compared to conventionally used polypropylene (PP) in a rabbit model. METHODS The elastic TPU thread was processed and tensile tests were performed. Twenty female chinchilla rabbits underwent midline laparotomy. They were randomized to a TPU and a PP group depending on the suture used for fascia closure. After 7 or 21 days, the abdominal walls were assessed macroscopically for wound healing complications and were explanted for histopathological investigation. RESULTS Tensile tests showed a mean elastic elongation of 55.5% and a sufficient material strength of the TPU thread. In animal experiments, there was no difference between the groups at 7 days; however, the TPU suture showed significantly less CD68 positive cells (p < 0.001) and a higher collagen I/III ratio (p = 0.011) than PP did after 21 days. The amount of apoptotic cells was significantly elevated in the TPU group (p = 0.007) after 21 days. No differences were found concerning granuloma size and number of Ki67-positive cells. CONCLUSIONS The newly developed TPU thread shows promising tensile characteristics. Midline laparotomy closure is feasible and safe in a rabbit model. Immunohistochemistry indicates similar biocompatibility and wound healing after implantation compared to PP after 21 days. To confirm these findings and to proof long-term capability further studies need to be conducted.

Influence of skin closure technique on surgical site infection after loop ileostomy reversal: Retrospective cohort study

BACKGROUND Intestinal stoma closure is associated with high risk of surgical site infection (SSI) at stoma reversal site. The aim of this retrospective cohort study was to determine the outcome of purse string approximation (PSA) compared to primary linear closure (PLC) of the skin after loop ileostomy reversal. METHODS Data of 140 patients operated between 2005 and 2012 were analyzed in this two-center-study to determine the outcome of patients with either PSA (n = 44) or PLC (n = 96) after loop ileostomy reversal. RESULTS Patients in the PSA group were significantly older than in the PLC group (64 ± 15 vs. 57 ± 18; p = 0.026). Cardiac diseases were significantly more present in the PSA group in comparison to the PLC group (59% vs. 38%; p = 0.017). Stoma creation was significantly more often due to malignancy in the PSA group in comparison to the PLC group (68% vs. 50%; p = 0.044). SSI occurred significantly more often in the PLC group in comparison to the PSA group (17% vs. 5%; p = 0.047). CONCLUSIONS The risk for SSI is lower in patients with PSA in comparison to patients with PLC. In order to diminish SSI we recommend performing a PSA in patients with loop ileostomy reversal.

Etiology of Appendicitis in Children: The Role of Bacterial and Viral Pathogens

ABSTRACT Background: Although acute appendicitis is the most common cause for abdominal surgery in children, its etiology is still largely unknown. The aim of this study was to evaluate the role of bacterial and viral pathogens for the etiology of appendicitis in children. Methods: Between 2000 and 2010, 277 children underwent appendectomy in our institution. On this collective, a retrospective study was performed on to identify the presence of bacterial or viral pathogens. Results: Intraoperatively, 39% of cases showed acute, 9% of cases chronic, and 41% of cases ulcerous inflammation. Bowel perforation was found in 7% of cases and four percent of the children had no inflammation of the appendix at all. Escherichia coli was the predominant bacterium with an incidence of 27.4%, followed by streptococci (9.8%). Concerning viral pathogens, adenovirus was the most common with an incidence of 5.4% followed by rotavirus (4.7%). Significant correlations between histopathological findings and present pathogens were found: in cases of bowel perforation there were significantly more infections with E. coli bacteria (32.2%, p < .001), streptococci (12.2%, p < 0.001), and Pseudomonas aeruginosa (6.7%, p < .001) whereas chronic inflammations were accompanied with a significantly elevated rate of yersinia infections (2.5%, p = .016). Acute inflammations were significantly more often associated with campylobacter (1.7%, p = .011) and oxyures infections (6.1%, p < .001). In relation to the patients’ age, a significant accumulation of different pathogens was observed. CRP- and leukocyte counts showed differences between viral and bacterial inflammations. Conclusions: Our data indicates that appendicitis in children might be triggered by bacterial and viral pathogens and that the type of pathogen directly correlates with patient age, type of inflammation, and level of inflammation values. To confirm and further evaluate these findings, additional studies need to be conducted.

Elastic mesh with thermoplastic polyurethane filaments preserves effective porosity of textile implants

In hernia surgery, meshes with small pores tend to be filled by fibrous tissue, which reduces their stretchability and causes patient complaints. Because of the inelasticity of current meshes, mechanical strain might cause pores to collapse even in large-pore mesh constructions. In this study, a mesh with elastic thermoplastic polyurethane (TPU) filaments was constructed to prevent pore size changes even under mechanical strain, and its biocompatibility in comparison with polyvinylidene fluoride (PVDF) was evaluated. A mesh was constructed using PVDF with elastic TPU filaments and mechanically tested. After midline laparotomy in 20 rabbits, we placed a 15 cm × 3 cm mesh as inlay in the defect. Animals were randomized to either the TPU or PVDF group. After 7 or 21 days, mesh expansion was measured under pneumoperitoneum, and abdominal walls were explanted for immunohistochemical investigations. In vitro, TPU meshes showed a slight reduction in effective porosity from 46% at tension-free conditions to 26% under longitudinal and to 34% under transverse strain. The nonelastic PVDF meshes showed a marked reduction in effective porosity from 70% to 7% and 52%, respectively. The TPU mesh had a breaking elongation of 101% and a tensile strength of 35 N/cm. In vivo, both meshes achieved healing of the incision without hernial defect. The TPU mesh maintained its elasticity under pneumoperitoneum. The amount of CD68-positive, Ki67-positive, and apoptotic cells was significantly lower in the TPU group after 7 and 21 days. The newly developed TPU mesh shows elasticity, structural stability, and preserved effective porosity under mechanical strain. Immunohistochemistry indicates superior biocompatibility of TPU mesh compared with PVDF after 7 and 21 days.

Biocompatibility and biomechanical analysis of elastic TPU threads as new suture material

High suture tension is one of the causes for many wound-healing problems. Constriction of tissue within the suture loops of nonelastic sutures can lead to cutting of the suture through tissues and necrosis of the tissue within these loops. The use of elastic materials in new suture types could give the material the ability to adapt tension to the tissue requirements and subsequently lead to more vital tissue within its loops. We evaluated the foreign body host response, as indicator of biocompatibility, to a new thermoplastic poly(carbonate) urethane (TPU) synthetic suture material in a rat model compared with standard nonelastic polypropylene (PP) sutures. Tissue samples were collected at 7 and 21 days, and host response was evaluated. Subsequently, suture tension curves of the new elastic sutures for the first 30 min after knotting were recorded in a pig model. The new TPU sutures showed an improved foreign body response when compared with that of PP, with a reduction in the amount of macrophages surrounding the material. Tension experiments showed a superior tension curve for TPU sutures, with a major reduction in peak suture tension when compared with that of standard PP sutures, while still retaining adequate tension after 30 min.

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

ABSTRACT 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.

Elastic TPU Mesh as Abdominal Wall Inlay Significantly Reduces Defect Size in a Minipig Model

ABSTRACT Background: The open abdomen with mesh implantation, followed by early reoperation with fascial closure, is a modern surgical approach in difficult clinical situations such as severe abdominal sepsis. As early fascial closure is not possible in many cases, mesh-mediated fascial traction is helpful for conditioning of a minimized ventral hernia after open abdomen. The aim of this study was to evaluate the clinical utilization of an innovative elastic thermoplastic polyurethane mesh (TPU) as an abdominal wall inlay in a minipig model. Methods: Ten minipigs were divided in two groups, either receiving an elastic TPU mesh or a nonelastic polyvinylidene fluoride (PVDF) mesh in inlay position of the abdominal wall. After 8 weeks, mesh expansion and abdominal wall defect size were measured. Finally, pigs were euthanized and abdominal walls were explanted for histological and immunohistochemical assessment. Results: Eight weeks after abdominal wall replacement, transversal diameter of the fascial defect in the TPU group was significantly smaller than in the PVDF group (4.5 cm vs. 7.4 cm; p = 0.047). Immunhistochemical analysis showed increased Ki67 positive cells (p = 0.003) and a higher number of apoptotic cells (p = 0.047) after abdominal wall replacement with a TPU mesh. Collagen type I/III ratio was increased in the PVDF group (p = 0.011). Conclusion: Implantation of an elastic TPU mesh as abdominal wall inlay is a promising approach to reduce the size of the ventral hernia after open abdomen by mesh-mediated traction. However, this effect was associated with a slightly increased foreign body reaction in comparison to the nonelastic PVDF.

Influence of gentamicin-coded PVDF suture material on the healing of intestinal anastomosis in a rat model

PurposeIntestinal anastomosis is a fundamental procedure in general surgery and required to restore intestinal continuity following resection. The aim of this study was to evaluate whether a gentamicin-coated polyvinylidene fluoride (PVDF) suture material has beneficial effect on anastomotic healing.MethodsNinety Sprague-Dawley rats were divided into three groups: a PVDF-suture group, a gentamicin-coated PVDF (GPVDF)-suture group and a control group using Maxon® (polyglycolid-co-trimethylene carbonate). For each animal, a colonic anastomosis was performed. Ten animals from each group were sacrificed on postoperative days 3, 5, and 14. Measurements of anastomotic bursting pressure were performed on days 3 and 5. At each time, collagen type I/III ratio, MMP 2 and MMP-9 expression and the proliferation index (Ki67) were analyzed.ResultsIn total, 90 animals underwent surgery without postoperative complications. Bursting strength in the GPVDF group was significantly elevated on day 5. Immunohistochemistry showed significant increase of the collagen type I/III ratio for PVDF and GPVDF on days 3 and 5. MMP2 was significantly increased for PVDF on days 3 and 5 and for GPVDF on day 5. The analysis of MMP9 revealed significant increase compared to control on day 3 and 5 (GPVDF) as well as on day 5 (PVDF). Staining for Ki67 revealed a significant elevation on postoperative day 3 for the PVDF and the GPVDF group.ConclusionsThe present data shows the feasibility of PVDF as suture material for colonic anastomosis and confirms the ability of gentamicin to increase the stability of colonic anastomosis when used as coating material.