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

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.

[Oligometastasized colorectal cancer-modern treatment strategies]. / Oligometastasierung beim kolorektalen Karzinom ­ moderne Therapiekonzepte.

BACKGROUND: The prognosis of colorectal cancer in UICC stage IV has been improved in the last decades by improvements in interdisciplinary treatment. MATERIAL AND METHODS: Treatment strategies for oligometastasized colorectal cancer are developing more and more into an individualized treatment. An overview of the current literature of modern treatment concepts in oligometastasized colorectal cancer UICC stage IV is given. RESULTS: Surgery still has the supreme mandate in resectable colorectal liver metastases, as neoadjuvant and adjuvant treatment strategies to not provide any benefits for these patients. In marginal or non-resectable stages systemic treatment is superior in these patients depending on the prognostic parameters. Also in curative settings local treatment options should be considered as a reasonable additive tool. An interesting treatment approach for isolated liver metastases and non-resectable colorectal cancer is liver transplantation. CONCLUSION: Irrespective of new developments in treatment strategies for metastasized colorectal cancer, resection of colorectal liver metastases remains the gold standard whenever possible.

Long-term outcome and quality of life after initial and repeat resection of colorectal liver metastasis: A retrospective analysis.

BACKGROUND: Repeat hepatectomy is a widely accepted treatment for patients with recurrent colorectal liver metastasis (CRLM). The aim of this study was to compare initial and repeat hepatic resection concerning overall survival, prognostic factors and postoperative quality of life. METHODS: Data on patients who underwent initial or repeat hepatic resection for CRLM between 2010 and 2016 were prospectively collected and retrospectively evaluated. Follow-up data, EORTC QLQ-C30 and QLQ-LMC21 questionnaire results for quality of life (QoL) evaluation were analyzed. RESULTS: 160 patients at a median age of 62.8 ± 11.8 years were analyzed. 122 were initially resected and 38 underwent a repeat hepatic resection. Disease-free survival (DSF) was superior in the initial resection group (p < 0.001), while there was no difference in overall survival (OS) (p = 0.288). BMI >30 (p = 0.012), extrahepatic tumor manifestation (p = 0.037), >1 CRLM manifestation (p = 0.009), and perioperative chemotherapy (p = 0.006) in the initial resection group and primary left colon tumor (p = 0.001) in the repeat resection group were identified as prognostic factors in multivariate Cox regression analysis. EORTC QLQ-LMC-21 module symptom score displayed an increased occurrence of a dry mouth in the initial hepatectomy group (p = 0.003). EORTC QLQ-C30 general functioning and symptom scores showed no difference. CONCLUSION: Repeat hepatic resection for CRLM is as effective as primary surgical treatment in terms of OS and QoL. Patients should be selected carefully concerning prognostic factors as DFS is decreased after repeat hepatic resection.

Impact of Preoperative Three-Dimensional Computed Tomography Cholangiography on Postoperative Resection Margin Status in Patients Operated due to Hilar Cholangiocarcinoma.

INTRODUCTION: The purpose of this study was to analyse the value of 3-dimensional computed tomography cholangiography (3D-ERC) compared to conventional retrograde cholangiography in the preoperative diagnosis of hilar cholangiocarcinoma (HC) with special regard to the resection margin status (R0/R1). PATIENTS AND METHODS: All hepatic resections performed between January 2011 and November 2013 in patients with HC at the Department of General, Visceral and Transplant Surgery of the RWTH Aachen University Hospital were analysed. All patients underwent an ERC and contrast-enhanced multiphase CT scan or a 3D-ERC. RESULTS: The patient collective was divided into two groups (group ERC: n = 17 and group 3D-ERC: n = 16). There were no statistically significant differences between the two groups with regard to patient characteristics or intraoperative data. Curative liver resection with R0 status was reached in 88% of patients in group ERC and 87% of patients in group 3D-ERC (p = 1.00). We could not observe any differences with regard to postoperative complications, hospital stay, and mortality rate between both groups. CONCLUSION: Based on our findings, preoperative imaging with 3D-ERC has no benefit for operative planning and R0 resection status. It cannot replace the exploration by an experienced surgeon in a centre for hepatobiliary surgery.

Risk factors for morbidity after appendectomy.

INTRODUCTION: The aim of the present study was to evaluate the risk factors for postoperative complications after an appendectomy with special regard to both the time period from hospital admission to operation and night time surgery. PATIENTS AND METHODS: Patients who underwent an appendectomy due to acute appendicitis and were admitted to the University Hospital Aachen between January 2003 and January 2014 were included in this retrospective analysis. Regarding the occurrence of postoperative complications, patients were divided into the following two groups: the group with complications (group 1) and the group without complications (group 2). RESULTS: Of the 2136 patients who were included in this study, 165 patients (group 1) exhibited complications, and in 1971 patients (group 2), no complications appeared. After a univariate logistic regression analysis, six predictors for postoperative complications were found and are described as follows: (1) complicated appendicitis (odds ratio (OR) 4.8 (3.46-6.66), p < 0.001), (2) operation at night (OR 1.62 (1.17-2.24), p = 0.004), (3) conversion from laparoscopic to open access (OR 37.08 (12.95-106.17), p < 0.001), (4) an age > 70 years (OR 6.00 (3.64-9.89), p < 0.001), (5) elevated CRP (OR 1.01 (1.01-1.01), p < 0.001) and (6) increased WBC count (OR 1.04 (1.01-1.07), p = 0.003). After multivariate logistic regression analysis, a significant association was demonstrated for complicated appendicitis (1.88 (1.06-3.32), p < 0.031), conversion to open access (OR 16.33 (4.52-58.98), p < 0.001), elevated CRP (OR 1.00 (1.00-1.01), p = 0.017) and an age > 70 years (OR 3.91 (2.12-7.21), p < 0.001). The time interval between hospital admission and operation was not associated with postoperative complications in the univariate and multivariate logistic regression analyses, respectively. However, the interaction between complicated appendicitis and the time interval to operation was significant (OR 1.024 (1.00-1.05), p = 0.028). CONCLUSION: Based on our findings, surgical delay in the case of appendicitis and operation at night did not increase the risk for postoperative complications. However, the mean waiting time was less than 12 h and patients aged 70 years or older were at a higher risk for postoperative complications. Furthermore, for the subgroup of patients with complicated appendicitis, the time interval to surgery had a significant influence on the occurrence of postoperative complications. Therefore, the contemporary operation depending on the clinical symptoms and patient age remains our recommendation.

Surgical sutures: coincidence or experience?

BACKGROUND: Knotting sutures by hand is still important in daily surgical routine, especially laparotomy closure. The expectation is that hand suturing relies on the experience and subjective estimation of the surgeon. The aim of this study was to investigate whether hand suturing tension is reproducible and if surgical experience influences reproducibility. METHODS: At the annual Congress of the German Association of Surgery, 118 surgeons performed repetitive sutures on a standardized and certified measuring device simulating the final knot of a fascial closure. Each surgeon was asked to perform five identical single knots in a row using the suture tension that each considered ideal. Tension during knotting was measured in Newtons. The surgeons were divided into five subgroups based on surgical experience: group 1, <1 year; group 2, 2-5 years; group 3, 6-10 years; group 4, 11-20 years; and group 5, >30 years. RESULTS: The tension measured at the end of knotting ranged from 0.19 to 10 N. The mean suture tension at endpoint was 3.88 N for group 1 and slightly higher in the other groups, but not significantly different. The overall mean suture tension was 5.43 N and did not correlate with surgical experience. Suture tension was not reproducible. CONCLUSION: Sequential suture tension varied, even among experienced surgeons. The ideal tissue-dependent suture tension has not been defined. Measured values appear to be intuitive, relying on individual feeling rather than the level of experience.

[Rectal perforation : A rare complication following radiotherapy]. / Rektumperforation : Eine seltene Komplikation nach Strahlentherapie.

BACKGROUND: Radiotherapy in the treatment of prostate cancer is well established. Intestinal complications following radiotherapy are divided into acute and chronic toxicity. Chronic complications like perforation and fistula formation to the rectum are rare and difficult to treat. MATERIALS AND METHODS: In case of chronic radiotherapy complications and particularly chronic fistula formation to the rectum, evidence is low. Therefore, an overview of the available literature of surgical therapy strategies is given. RESULTS: Options for the treatment of acute intestinal toxicity are established and therapy algorithms exist. Therapy of acute rectal perforation covers primary suture repair with or without diversion stoma as well as primary rectal resection with or without primary restoring bowel continuity. In chronic rectal lesions and particularly in fistula formation to the rectum, abdominal treatment strategies are preferred with additional interposition of an omental flap or vascularized muscle flap. CONCLUSION: Although evidence for surgical therapy strategies of the rare chronic rectourethral and rectovesical fistula is low, treatment is a real interdisciplinary challenge and should be provided in a specialized center.

[Video-assisted retroperitoneal debridement : Minimally invasive treatment and long-term results for necrotizing pancreatitis]. / Videoassistiertes retroperitoneales Débridement : Minimalinvasive Therapie und Langzeitverlauf bei nekrotisierender Pankreatitis.

BACKGROUND: Among patients with necrotizing pancreatitis 15-20% develop infected necrosis, which entails mortality rates of up to 20%. Particularly driven by the results of the Dutch Pancreatitis Study Group there has been a paradigm change from open necrosectomy to step-up treatment with initial percutaneous and/or endoscopic drainage followed, if necessary, by minimally invasive retroperitoneal debridement. AIM OF THE STUDY: Description of case series in which patients underwent video-assisted retroperitoneal debridement (VARD) including follow-up focused on quality of life. METHODS: Systematic cohort study including all patients who underwent a VARD procedure at the Department of General, Visceral and Transplantation Surgery at Aachen University Hospital from 2011 to 2015. Quality of life was recorded using the EORTC QLQ-C 30 questionnaire and compared to a representative sample of the German general population. RESULTS: The VARD procedure was performed in 9 cases, although in 1 case conversion to an open approach due to an acute bleeding was necessary. There was no 30-day and 60-day mortality following VARD. During the postoperative stay no patient required specific treatment for surgical complications. In particular, no enterocutaneous fistula or organ perforation was observed. Regarding the quality of life score there was no significant difference concerning the global health status, compared to the sample from the general population. DISCUSSION: Our data reinforce that a step-up approach in patients with necrotizing pancreatitis is a feasible and safe treatment procedure. For the first time, we could demonstrate satisfactory results in a long-term follow-up including QOL.

[Oligometastasized stage IV colorectal cancer : Surgical resection and local ablative procedures]. / Oligometastasierung beim kolorektalen Karzinom im Stadium IV : Chirurgie und lokal ablative Verfahren.

BACKGROUND: By the intensified combination of systemic, surgical and local ablative therapies a significant improvement in therapy results for metastasized colorectal cancer has been achieved in the last decade. Downstaging with subsequent resection is nowadays a standard for oligometastasized primarily unresectable colorectal cancer. MATERIAL AND METHODS: The value of combining resection and local ablation is unclear; therefore, this article gives an overview of the available literature dealing with the combination of surgery and local ablative methods for oligometastasized stage IV colorectal cancer. RESULTS: The best results were obtained following surgical resection alone. Whereas nowadays cryoablation is of minor importance, the most successful results are achieved following local ablative methods by radiofrequency and microwave ablation. In the future irreversible electroporation will be the most promising local ablative method. A combination of surgical resection and local ablation appears to be rational in patients if an R0 resection can be achieved. CONCLUSION: Surgical resection of colorectal liver metastases is the gold standard for oncological therapy whenever possible. The rational combination of non-curative surgical resection and local ablation should be considered in the context of a multimodal therapeutic strategy, particularly in patients with primarily resectable disease.

Analysis of adhesion formation of a new elastic thermoplastic polyurethane (TPU) mesh in comparison to polypropylene (PP) meshes in IPOM position.

BACKGROUND: Postsurgical adhesions severely affect the patients' quality of life causing various complications like bowel obstruction or chronic pain. Especially the implantation of alloplastic prostheses in IPOM position for hernia repair carries a high risk of adhesion formation due to the close contact between mesh and viscera. The extent of adhesions mainly depends on the type and textile characteristics of the implanted mesh. The aim of this study was to examine the degree of adhesion formation of a newly developed, elastic thermoplastic polyurethane (TPU) mesh in comparison to polypropylene (PP) meshes in IPOM position in a rabbit model. METHODS: Sixteen female chinchilla rabbits were laparoscopically operated. Two different meshes were placed to the left and the right lower abdominal wall in IPOM position in each rabbit. After 7 or 21 days, midline laparotomy was performed, the degree of adhesion formation was examined by the Diamond score and mesh elongation was measured under a force of 3N. Finally, the abdominal walls were explanted for immunohistochemical and histopathological investigations. RESULTS: TPU meshes showed significantly lower Diamond scores than PP meshes. After explantation, mesh elongation of the TPU mesh was significantly larger than expansion of PP under a force of 3N. Thus, the TPU mesh preserved its elastic properties after 7 and 21 days. The amount of CD68 positive, Ki67 positive and apoptotic cells within the granuloma around the fibers did not show significant differences between the study groups. CONCLUSIONS: The newly developed TPU mesh seems to reduce peritoneal adhesion formation in IPOM position in a rabbit model compared to PP meshes after 7 and 21 days. Immunohistochemistry did not reveal differences in biocompatibility of the two meshes used.

Treatment of symptomatic aberrant subclavian arteries.

OBJECTIVE: The aim of this study is to present experience with 10 patients with symptomatic aberrant subclavian artery (ASA) and aneurysm of ASA who underwent surgical treatment. METHODS: From 2008 to 2011 10 patients with symptomatic aberrant subclavian artery (mean age 60 years [range 24-90 years]) were studied. Symptoms were dysphagia (n = 7), dyspnea (n = 4), acute chest pain (n = 1), respiratory distress syndrome (n = 1), superior cava syndrome, and shock (n = 1). Six patients had aneurysm formation of the ASA (mean diameter of 7.1 cm [range 3.0-12.4 cm]; rupture [n = 1], dissection [n = 1]). All data were analyzed retrospectively. RESULTS: Treatment was performed as a hybrid procedure in eight patients. This included thoracic endoluminal graft exclusion with revascularization of the ASA, a pure endovascular procedure with two occluders in one patient, and an open procedure in one patient with ligation of the aberrant artery through a thoracotomy. Three patients died during the early postoperative period owing to pulmonary complications. All three suffered from a symptomatic aneurysm, and two were treated as an emergency procedure. Median follow-up was 20 months (range 12-49 months). CONCLUSION: A symptomatic ASA and its associated aneurysmal formation should be excluded after diagnosis. In most cases, a hybrid procedure consisting of thoracic endografting and revascularization of the ASA is feasible.

Colonic wall changes in patients with diverticular disease - is there a predisposition for a complicated course?

BACKGROUND: The aim of this study was to evaluate colonic wall changes and enteric neuropathy in patients with either uncomplicated (UDD) or complicated diverticular disease (CDD). Furthermore, we evaluated the presence of an anatomic sphincter at the rectosigmoid junction (RSJ). METHODS: Samples of colonic tissue from fifteen patients with UDD, fifteen patients with CDD and fifteen patients as control were collected. Collagen quotient I/III was measured with the Sirius-red test, expression of MMP-1, MMP-13, innervation (S100), proliferation (Ki67) and apoptosis (TUNEL) in the colonic wall were investigated by immunohistochemical studies. Furthermore, measurements of the different layers were performed to investigate the RSJ. RESULTS: Patients with either UDD or CDD had lower collagen I/III quotients compared to the control group, significant for CDD (p = 0.007). For MMP-1 and MMP-13 only a slight increase for patients with CDD was found. The percentage of proliferating (Ki67) and apoptotic (TUNEL) cells was significantly higher for patients with CDD than in the control group (p = 0.016; p = 0.037). Upon investigating the S100-expression a significant reduce in glial cells density was found in the myenteric and mucosal plexus for both groups (UDD and CDD) compared to the control group. Measurements of the different colon layers oral, aboral and at the RSJ revealed equal values. CONCLUSIONS: This study has shown that colonic wall changes and enteric neuropathy seem to play a role in the pathogenesis of colonic diverticulosis. None of our results suggest a predisposition for a complicated diverticular disease. Furthermore, the presence of an anatomic sphincter at the rectosigmoid junction could not be detected.

Postoperative outcome in premature infants with open abdomen.

BACKGROUND: Premature infants treated with laparostomy in the first days of their life represent a group of complex patients with high morbidity and mortality rates. Laparostomy is a surgical treatment method in which the peritoneal cavity is opened anteriorly and deliberately left open, hence often called "open abdomen". The aim of this study was to analyze crucial factors influencing the postoperative outcome of premature infants treated this way. METHODS: Between March 2002 and August 2012, we treated 40 premature infants with a median gestational age of 29 weeks (range from 24 to 34 weeks) with open abdomen in our institution. Their data were analyzed retrospectively. They were divided into two groups depending on in-hospital survival. RESULTS: Indications for surgery were ileus (n = 16), spontaneous intestinal perforation (n = 11), gastroschisis (n = 8) and necrotizing enterocolitis (NEC, n = 5). The overall in-hospital mortality was 43 % (17 of 40 patients). Postoperative anemia was the only significant factor influencing mortality rates in our patients (10 vs. 14 patients; p = 0.028). Neither the indication of surgery, nor week of gestation, nor birth weight had any significant influence on postoperative survival. Twenty-one of the 23 surviving patients reached fascia closure. CONCLUSIONS: In our study, outcome of premature infants with open abdomen in the first days of their life seems to depend more on an operation and a postoperative course without complications than on the preoperative conditions of the children. Postoperative anemia seems to be a significant negative prognostic marker. Patients reaching fascia closure mainly survive.

Influence of intraoperative radiotherapy (IORT) on perioperative outcome after surgical resection of rectal cancer.

BACKGROUND: Intraoperative radiotherapy (IORT) for locally advanced or recurrent rectal cancer as an integral part of multimodal treatment might be an option to reduce local cancer recurrence. The aim of the present study was to determine the influence of IORT on the postoperative outcome and complications rates in the treatment of patients with adenocarcinoma of the rectum in comparison to patients with rectum resection only. METHODS: A total of 162 patients underwent operation for International Union against Cancer stage III/IV rectal cancer or recurrent rectal cancer at our surgical department between 2004 and 2012. They were divided into two groups depending on whether they received IORT or not. General patient details, tumor, and operation details, as well as perioperative major and minor complications, were registered and compared. RESULTS: Of the 162 patients treated for stage III/IV rectal cancer, 52 underwent rectal resection followed by IORT. Complication rates were similar in the two groups. Operative time was significantly longer in the IORT group (248 ± 84 vs 177 ± 68 min; p < 0.001). No significant differences were found concerning anastomotic leakage rate, hospital stay, or wound infection rate. CONCLUSIONS: Intraoperative radiotherapy appears to be a safe treatment option in patients with locally advanced or recurrent rectal cancer with acceptable complication rates. The effect on local recurrence rate has to be estimated in long-term follow-up.

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.

Suture-free and mesh reinforced small intestinal anstomoses: a feasibility study in rabbits.

INTRODUCTION: Anastomotic leakage still remains a major complication in general surgery. Beside general risk factors, the ideal method of anastomotic technique has not been found until now. The aim of the present study was to analyze wound healing in suture-free small intestine anastomoses using fibrin glue with and without mesh-reinforcement. METHODS: Laparotomy and four different types of small bowel anastomoses were performed in 32 chinchilla rabbits. Standard hand-sewn anastomoses (CG), suture-free glued anastomoses (FG) with and without mesh reinforcement using two different types of meshes [Vicryl-mesh (VM) and Surgisis (SM)]. Animals were sacrificed after 5 and 21 days. Bursting pressure, collagen type I/III ratio, and matrix-metalloproteinase 2, 9, and 13 were analyzed. RESULTS: None of the animals died due to an anastomotic leakage. All animals in the long term group with Surgisis mesh died due to a mechanical bowel obstruction based on a distinctive stenosis of the anastomosis. The bursting pressures did significantly differed in animals with fibrin glue alone compared to animals with Vicryl-mesh reinforcement (p < 0.05). Histological examination revealed statistically significant differences (p < 0.05) in the values for MMP-2 (VM < SM), MMP-9 (VM < CG), and MMP-13 (CG < SM, VM < FG, and VM < SM). However, collagen type I/III ratios were not significantly different between groups. CONCLUSIONS: Our results suggest that a mesh reinforced glued anastomosis is technically feasible. Furthermore, mesh-reinforcement using VM increased the integrity and simplified the technique of suture-free anastomoses.

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.

Comparison of long-term biocompability of PVDF and PP meshes.

BACKGROUND: Abdominal hernia repair is the most frequently performed operation in surgery. Mesh repair in hernia surgery has become an integral component. Although meshes made of PVDF are already in clinical use, so far no data of long-term biocompability are available. METHODS: In this study a PVDF mesh was compared to a polypropylene mesh with regard to its long-term biocompatibility. A total of 28 rats were randomized to two groups. Mesh material was implanted subcutaneously; animals were euthanized seven days and six months postoperatively. The quantity of inflammatory tissue response was characterized by measuring the diameter of the foreign body granuloma. Furthermore quality of cellular immune response (T-lymphocytes, macrophages, and neutrophils), and inflammation (COX-2) was analyzed by immunohistochemistry. Furthermore the collagen type I/III ratio was determined. RESULTS: Macrophages, T-lymphocytes, neutrophiles, and COX-2 declined significantly up to six months postoperatively in comparison to day 7 for both PVDF and PP meshes, and in both groups the collagen ratio increased significantly in the course of time. PVDF meshes showed a foreign body granuloma size significantly reduced compared to PP (7 days: 20 ± 2 µm vs. 27 ± 2 µm; 6 months 15 ± 2 µm vs. 22 ± 3 µm; p < .001). However no significant differences were found analyzing cellular response six months postoperatively. CONCLUSIONS: Our current data suggest that even in the long-term course after six months and despite a higher effective surface of the PVDF samples it showed a smaller foreign body granuloma than with PP whereas the cellular response was similar.

Impact of pressure and gas type on adhesion formation and biomaterial integration in laparoscopy.

BACKGROUND: Laparoscopic mesh repair of inguinal and incisional hernias has been widely adopted. Nevertheless, knowledge about the impact of pneumoperitoneum on mesh integration is rare. The present study investigates pressure and gas-dependent effects of pneumoperitoneum on adhesion formation and biomaterial integration in a standardized animal model. METHODS: Laparoscopic intraperitoneal onlay mesh implantation (IPOM) was performed in 32 female chinchilla rabbits using CO(2) or helium for pneumoperitoneum. Intra-abdominal pressures were 3 or 6 mmHg. Animals were killed after 21 days, and the abdominal wall was explanted for subsequent histopathological examinations. Adhesions were assessed qualitatively with a scoring system, and the adhesion surface was analyzed semiquantitatively by planimetry. Infiltration of macrophages (CD68), expression of matrix metalloproteinase 13 (MMP-13), and cell proliferation (Ki67) were analyzed at the mesh to host interface by immunohistochemistry. The collagen type I/III ratio was analyzed by cross-polarization microscopy to determine the quality of mesh integration. RESULTS: After 21 days, perifilamental infiltration with macrophages (CD68) and percentage of proliferating cells (Ki67) were highest after 6 mmHg of CO(2) pneumoperitoneum. The extent of adhesions, as well as the expression of MMP-13 and the collagen type I/III ratio, were similar between groups. CONCLUSIONS: Our experiments showed no pressure or gas-dependent alterations of adhesion formation and only minor effects on biomaterial integration. Altogether, there is no evidence for a clinically negative effect of CO(2) pneumoperitoneum.