The role of tissue inhibitor of metalloproteinases in the aetiology of inguinal and incisional hernias.

Inguinal and incisional hernias are the two most common types of hernias caused by abdominal wall weakness and defects in connective tissue. The structure of the extracellular matrix, mainly collagen and metalloproteinases (MMPs), and their regulators have been studied extensively and found to play a significant role in the pathophysiology of hernias. One of the regulators of MMPs, tissue inhibitor metalloproteinases (TIMPs), bind to MMPs and inhibit its activity significantly shifting the balance towards collagen synthesis rather than degradation. Due to their importance in collagen metabolism, their metabolism might be significant in the aetiology of hernias. Our study used immunohistochemical techniques to investigate the possible effects of TIMP 1 and 2 on the samples taken from the abdominal walls of patients with inguinal and incisional hernias, compared them with control patients, and reviewed the literature. In this study, samples of 90 patients (30 patients from control, inguinal hernia, and incisional hernia groups) were taken and analysed. These samples were stained with TIMP-1 Ab-2 and TIMP2 Ab-5 (Clone 3A4) antibodies and evaluated under ×100 magnification. The degree of staining was classified as (a): No staining (0), (b): Staining less than 10% (I), (c): Staining between 10% and 50% (II), (d): Staining more than 50% (III). Statistical analyses were done. No significant difference was found between groups in terms of patient demographics. Smoking and family history of hernia was not found to be associated with TIMP expression. TIMP1 expression was significantly higher in the incisional and inguinal hernia group than in the control group (P < .05), while the level of TIMP2 was higher in the control group. (P < .05). TIMP1 and TIMP2 levels did not significantly differ between incisional and inguinal hernia groups. We found significantly increased TIMP-1 levels in tissue samples from patients with hernia supporting its suggested role in hernia pathophysiology. Local alterations in MMP and TIMP levels might play a role in the pathogenesis of hernias. Thus detection of TIMP in tissues can be important for clinical use after further validation studies. In the era of molecular medicine, detecting TIMP levels in hernia patients can impact clinical practice.

Complications and Impact on Quality of Life of Vertical Rectus Abdominis Myocutaneous Flaps for Reconstruction in Pelvic Exenteration Surgery.

BACKGROUND: Pelvic exenteration for malignancy sometimes necessitates flap reconstruction. OBJECTIVE: This study's aim was to investigate flap-related morbidity. DESIGN: A prospective database was reviewed from 2003 to 2016. All medical charts, correspondence, and outpatient follow-up records up to May 2017 were reviewed. SETTINGS: This study was conducted at a tertiary referral unit. PATIENTS: Patients who underwent pelvic exenteration surgery were selected. INTERVENTIONS: Reconstruction was performed with a vertical rectus abdominis myocutaneous flap. MAIN OUTCOME MEASURES: Primary outcome was flap-related complications (short or long term >3 months). Secondary outcomes were hospital stay, readmission, mortality, and quality of life (Short Form-36, Functional Assessment of Cancer Therapy for patients with colorectal cancer). RESULTS: Of 519 patients undergoing pelvic exenteration surgery, 87 (17%) underwent flap reconstruction. Median follow-up was 20 months (interquartile range, 8-39 months). Median age was 60 years (interquartile range, 51-66). Flap-related complications were found in 59 patients (68%), with minor recipient-site complications diagnosed in 33 patients (38%). In the short term, 15 patients experienced major recipient-site complications (17%), including flap separation (n = 7) and partial (n = 3) or complete necrosis (n = 4). Flap removal was required in 1 patient. Obesity was the single independent risk factor for short-term flap-related complications (p = 0.02). Hospital admission was significantly longer in patients with short-term major flap complications (median 65 days, p < 0.001) compared with patients without or with minor complications. There was no 90-day mortality. Patients who required flap reconstruction reported lower baseline quality-of-life scores than patients without flap reconstruction, but both recovered over time. In the long term, minor flap-related complications occurred in 12 patients, and 11 patients had major donor-site complications. Fourteen patients developed major recipient-site complications (16%), including sacral collections, enterocutaneous fistulas, perineal ulcer, or hernia. LIMITATIONS: This was a retrospective analysis of prospectively collected data. CONCLUSIONS: Vertical rectus abdominis myocutaneous flaps in pelvic exenteration surgery have a high incidence of morbidity that has significant impact on hospital stay and a temporary impact on quality of life. Flap reconstruction should be used selectively in pelvic exenteration surgery. See Video Abstract at http://links.lww.com/DCR/B274. COMPLICACIONES E IMPACTO EN LA CALIDAD DE VIDA DE LOS COLGAJOS MIOCUTÁNEOS DE MUSCULO RECTO DEL ABDOMEN EN CASOS DE RECONSTRUCCIÓN DE EXENTERACIÓN PÉLVICA: La exenteración pélvica (EP) para malignidad a veces requiere reconstrucción con colgajos musculares.El propósito del presente estudio fue investigar la morbilidad relacionada con los colagajos musculares.Revisión de una base de datos prospectiva de 2003-2016. Se evaluaron todas las historias clínicas, la correspondencia y los registros de seguimiento de pacientes ambulatorios hasta mayo de 2017.Unidad de referencia terciaria.Todos aquellas personas con cirugía de exenteración pélvica.Reconstrucción con colgajo miocutáneo de musculo recto vertical del abdomen.El resultado primario fueron las complicaciones relacionadas con el colgajo (a corto o largo plazo >3 meses). Los resultados secundarios fueron la estadía hospitalaria, la readmisión, la mortalidad y la calidad de vida (QOL; SF-36, FACT-C).De 519 pacientes sometidos a EP, 87 (17%) se sometieron a reconstrucción con colgajos miocutáneos. La mediana de seguimiento fue de 20 meses (RIC 8-39 meses). La mediana de edad fue de 60 años (IQR 51-66). Se encontraron complicaciones relacionadas con el colgajo en 59 pacientes (68%), con complicaciones menores en el sitio del receptor diagnosticadas en 33 pacientes (38%). A corto plazo, quince pacientes sufrieron complicaciones mayores en el sitio del receptor (17%), incluida la separación del colgajo (n = 7), necrosis parcial (n = 3) o necrosis completa (n = 4). Se requirió la extracción del colgajo en un paciente. La obesidad fue el único factor de riesgo independiente para complicaciones relacionadas con el colgajo a corto plazo (p = 0.02). El ingreso hospitalario fue significativamente mayor en pacientes con complicaciones de colgajos mayores a corto plazo (mediana 65 días p <0.001) en comparación con pacientes sin complicaciones menores o con complicaciones menores. No hubo mortalidad a los 90 días. Los pacientes que requirieron reconstrucción con colgajo informaron puntajes de calidad de vida basales más bajos que los pacientes sin reconstrucción con colgajo, pero ambos se recuperaron con el tiempo. A largo plazo, ocurrieron complicaciones menores relacionadas con el colgajo en 12 pacientes y 11 pacientes tuvieron complicaciones mayores en el sitio donante. Catorce pacientes desarrollaron complicaciones mayores en el sitio del receptor (16%), incluidas colecciones sacras, fístulas enterocutáneas, úlceras perineales o herniación.Análisis retrospectivo de datos recolectados prospectivamente.Los colgajos miocutáneos del musculo recto vertical del abdomen en casos de cirugía de exenteración pélvica tienen una alta incidencia de morbilidad conllevando a un impacto significativo en la estadía hospitalaria y un impacto temporal en la calidad de vida. Las reconstrucciones con colgajos deben aplicarse muy selectivamente en la cirugía de exenteración pélvica. Consulte Video Resumen en http://links.lww.com/DCR/B274.

Histology and Function of the Rectus Abdominis Muscle in Patients With Incisional Hernia.

BACKGROUND: The aim of the current study was to examine different features of the rectus abdominis muscle (RA) in patients with and without a midline incisional hernia to characterize the effects of a hernia on abdominal wall skeletal muscle. MATERIAL AND METHODS: RA tissue from patients undergoing surgical repair of a large midline incisional hernia (n = 18) was compared with that from an intact abdominal wall in patients undergoing colorectal resection for benign or low-grade malignant disease (n = 18). In addition, needle biopsies were obtained from the vastus lateralis muscle (VL) of all subjects. Outcome measures were muscle fiber type and size, preoperative truncal flexion strength and leg extension power measured in strength-measure equipment, and RA cross-sectional area measured by computed tomography. RESULTS: In both the RA and VL, the fiber cross-sectional area was greater in the patients with a hernia. The RA cross-sectional area correlated significantly with the truncal flexion strength (r = 0.44, P = 0.015). Patients in the hernia group had a significantly reduced ratio between truncal flexion strength and RA cross-sectional area compared with the control group (41.3 ± 11.5 N/cm2versus 51.2 ± 16.3 N/cm2, P = 0.034). CONCLUSIONS: Anatomical displacement of the RA and lack of medial insertion in the linea alba rather than dysfunction secondary to alteration of muscle fiber structure may contribute to impairment of abdominal wall function in patients with midline incisional hernias. The study was registered at http://www.clinicaltrials.gov/(NCT02011048).

Characteristics of Trocar Site Hernia after Laparoscopic Cholecystectomy.

Trocar site hernia (TSH) is an incisional hernia occurring at the trocar insertion sites after different types of laparoscopic surgeries. The aim of this study is to present characteristics of patient and surgery series with trocar site hernia after laparoscopic cholecystectomy. A 2930 consecutive patients underwent laparoscopic cholecystectomy in two major university- affiliated hospitals from April 2014 to March 2018 and the patient followed up for variable periods of time. Retrospective medical chart review to study trocar site hernia including patient, operation, instruments, and pathologic characteristics described. Six patients had trocar site hernia (incidence 0.20%), the hernias occurred mostly at the umbilical port site after using 10 mm trocar. Risk factors included mainly obesity, female gender and use of 10 mm trocars at midline sites. TSH is more described. It occurs mostly at the umbilical port site. Major risk factors include obesity, diabetes mellitus, lengthy procedure, extension of entry site, and wound infection. Closure of fascial defect is supposed to reduce the incidence despite weak evidence.

Suturable mesh better resists early laparotomy failure in a cyclic ball-burst model.

PURPOSE: The small bites surgical technique supported by the STITCH trial has been touted as a strategy for preventing early laparotomy dehiscence through greater force distribution at the suture-tissue interface. However, this hernia prevention strategy requires an alteration in the standard closure technique that has not been widely adopted in the USA. This study seeks to determine whether incorporating a mid-weight polypropylene mesh material into a hollow-bore surgical suture material will effectively increase the force distribution at the suture-tissue interface and potentially help prevent early laparotomy dehiscence in an ex vivo model. METHODS: A cyclic stress ball-burst model was used to compare suturable mesh (0 DuraMesh™) to conventional suture. After midline laparotomy, 28 porcine abdominal wall specimens were closed with either 0 DuraMesh™ or #1 polydioxanone double-loop suture. A custom 3D-printed ball-burst test apparatus was used to fatigue the repair on a MTS Bionix Load Frame. The tissue was repetitively stressed at a physiological force of 15-120 N cycled at a rate of 0.25 Hz for a total of 1000 repetitions, followed by a load to failure, and the maximal force was recorded. RESULTS: The mean maximal force at suture pull-through was significantly higher (p < 0.0095) in the 0 DuraMesh suture group (mean: 850.1 N) compared to the 1 PDS group (mean: 714.7 N). CONCLUSION: This ex vivo study suggests that using rational suture design to improve force distribution at the suture-tissue interface may be a viable strategy for preventing the suture pull-through that drives incisional hernia.

Extraction-site incisional hernia after laparoscopic colorectal surgery: should we carry out a study about prophylactic mesh closure?

BACKGROUND: Prophylactic mesh closure has only scarcely been studied to avoid extraction-site incisional hernia after laparoscopic colorectal surgery. The aim was to analyze extraction-site incisional hernia incidence after laparoscopic colorectal surgery to assess if prophylactic mesh closure should be studied. METHODS: A retrospective analytic cohort study was conducted in patients who had undergone laparoscopic colorectal surgery with an extraction-site incision. Extraction-site incisional hernia was diagnosed during clinical examination or imaging. Risk factors for extraction-site incisional hernia were analyzed. RESULTS: Two hundred and twenty-five patients were included. More than 80% of the patients had a malignant disease. Ninety-two patients (40.9%) underwent right colectomy. Midline extraction-site incision was used in 86 (38.2%) patients. After a mean follow-up of 2.4 years, 39 (17.3%) patients developed an extraction-site incisional hernia. Midline extraction-site incision was associated with incisional hernia when compared to transverse and Pfannenstiel incision (39.5% vs. 3.6%, OR 17.5, p < 0.001). Surgery to repair an extraction-site incisional hernia was also more frequent in the group of patients with a midline incision (10.5% vs. 1.4%, OR 8.0, p = 0.002). In the multivariate analysis, incisional hernia was associated with body mass index, high blood pressure, and midline incision. CONCLUSIONS: Extraction-site incisional hernia was mainly related to midline incisions; therefore, midline incision should be avoided whenever possible. Studying prophylactic mesh closure for Pfannesnstiel or transverse incisions is needless, as these incisions have a low incisional hernia risk.

Large Incisional Hernias Increase in Size.

BACKGROUND: Patients with an incisional hernia often wait a significant period of time from the first referral to hernia surgery because of waiting lists, watchful waiting, or the need for preoperative optimization. It is unknown if hernia dimensions or patient-reported symptoms increase during this period. The aim of the study was to examine if incisional hernias increase in size during the time from initial assessment to surgical repair. MATERIALS AND METHODS: A prospective controlled trial was performed on patients referred to a regional hernia center for repair of an incisional hernia with a transverse fascial defect of >7 cm. All patients underwent computed tomography scans and answered the Hernia-Related Quality of Life Score questionnaire and International Physical Activity Questionnaire at first assessment and again 30 ± 2 wk later or immediately before hernia repair. Changes in fascial defect sizes and hernia sac volume were assessed along with the patient-reported outcomes. RESULTS: A total of 35 patients were included. The median fascial defect area increased from 117.3 cm2 (interquartile range 46.5-181.2) to 150.4 cm2 (62.5-199.0), P < 0.001, and the median hernia sac volume increased from 5.11 L (2.28-8.09) to 6.25 L (3.03-10.38), P < 0.001. There were no significant changes in the patient-reported outcomes. CONCLUSIONS: Incisional hernias expand during the period from the first assessment to actual hernia repair.

Incisional hernias following open gynecological surgery: a population-based study.

INTRODUCTION: Incisional hernia is a common and costly complication following abdominal surgery. The incidence of incisional hernia after gynecological surgery is not as well studied as that after general surgery. MATERIALS AND METHODS: The Swedish National Quality Register for Gynecological Surgery (GynOp) collects preoperative, intraoperative, and postoperative information regarding gynecological surgery. Data were extracted from 2006 to 2014. The National Patient Register (NPR) contains physicians' data from both public and private hospitals. Univariate and multivariate Cox proportional hazard analyzes were performed on risk factors. RESULTS: Between 2006 and 2014, 39,312 women undergoing open surgery were registered in GynOp. The NPR recorded 526 patients who were diagnosed with or had undergone surgery for incisional hernia. The mean follow-up was 2.8 years. Five years after surgery the cumulative incidence of incisional hernias was 2.0% (95% confidence interval 1.8-2.2%). In multivariate Cox proportional hazard analysis obesity (BMI > 30), age > 60 years, midline incision, smoking, kidney, liver, and pulmonary disease were found to predict an increased risk for incisional hernias (all p < 0.05). CONCLUSIONS: There is much to be gained if the patient can cease smoking and lose weight before undergoing abdominal surgery. The Pfannenstiel incision results in fewer incisional hernias and should be considered whenever possible.

A GP primer on incisional hernia.

BACKGROUND: Incisional hernias are often overlooked as a source of morbidity in post-surgical patients. OBJECTIVE: Drawing on evidence-based literature and personal clinical experience, this article seeks to provide information relevant to general practitioners (GPs) encountering patients with incisional hernias. DISCUSSION: Drawing on evidence-based literature and personal clinical experience, this article seeks to provide information relevant to GPs encountering patients with incisional hernias.

Sublay repair results in superior mesh incorporation and histological fibrogenesis in comparison to onlay and primary suture in an experimental rat model.

PURPOSE: To compare adhesion scores, repair strength and histological findings among sublay, onlay and primary repair incisional hernioplasty techniques. Surgical repairs were employed directly on healthy animals, without previous hernia induction, to avoid confounding factors related to hernia development. METHODS: Forty Wistar rats were divided into four groups, control, simulation, onlay and sublay. After 42 days, adhesion intensity, tensile strength of the abdominal wall and anatomopathological histological substrate were compared. RESULTS: SL group presented greater adhesion scores (p < 0.0001), higher tensiometric (p < 0.0001), and was characterized by more histiocytes, mononuclear cells, macrovacuolar granulomas and type I collagen on histological analysis. Pearson correlation between adhesions and tensiometry, and between tensiometry and neocollagenization showed a strong positive association (r = 0.8905 and 0.6757, respectively in SL group, p < 0.05). CONCLUSION: Mesh positioning in sublay compartment was followed by increased adhesion development and provides a stronger mesh-tissue attachment, in addition, resulted in a different histological profile of the inflammation/repair substrate. The intensity of these findings was directly correlated, suggesting they could be the result of a common biological phenomenon. Our findings indicate that mesh placement following the retromuscular technique generates a superior repair response, and give clues to a better understanding of the superiority of sublay repair in achieving lower recurrence rates. Characterization of the cellular and molecular elements responsible for the superiority of this technique is in our view an essential prerequisite aiming for improvements in the therapeutic options for the treatment of this disease.

Silver microparticles plus fibrin tissue sealant prevents incisional hernias in rats.

BACKGROUND: Open abdominal surgery is frequently complicated by the subsequent development of an incisional hernia. Consequently, more than 400,000 incisional hernia repairs are performed each year, adding over $15 billion per year to U.S. health-care expenditures. While the vast majority of studies have focused on improved surgical techniques or prosthetic materials, we examined the use of metallic silver microparticles to prevent incisional hernia formation through enhanced wound healing. MATERIALS AND METHODS: A rodent incisional hernia model was used. Eighty-two rats were randomly placed into two control groups (saline alone and silver microparticles alone), and three experimental groups (0 mg/cm, 2.5 mg/cm, and 25 mg/cm of silver microparticles applied with a fibrin sealant). Incisional hernia incidence and size, tensile strength, and tissue histology were assessed after 28 days. RESULTS: A significant reduction of both incisional hernia incidence and hernia size was observed between the control groups and 2.5 mg/cm group, and between the control and 25 mg/cm group by nearly 60% and 90%, respectively (P < 0.05). Histological samples showed a noticeable increase in new fibrosis in the treated animals as compared with the controls, whereas the tensile strength between the groups did not differ. CONCLUSIONS: The novel approach of using silver microparticles to enhance wound healing appears to be a safe and effective method to prevent incisional hernias from developing and could herald a new era of medicinal silver use.

Type V Collagen is Persistently Altered After Inguinal Hernia Repair.

BACKGROUND AND AIMS: Hernia formation is associated with alterations of collagen metabolism. Collagen synthesis and degradation cause a systemic release of products, which are measurable in serum. Recently, we reported changes in type V and IV collagen metabolisms in patients with inguinal and incisional hernia. The aim of this study was to determine if the altered collagen metabolism was persistent after hernia repair. MATERIAL AND METHODS: Patients who had undergone repairs for inguinal hernia (n = 11) or for incisional hernia (n = 17) were included in this study. Patients who had undergone elective cholecystectomy served as controls (n = 10). Whole venous blood was collected 35-55 months after operation. Biomarkers for type V collagen synthesis (Pro-C5) and degradation (C5M) and those for type IV collagen synthesis (P4NP) and degradation (C4M2) were measured by a solid-phase competitive assay. RESULTS: The turnover of type V collagen (Pro-C5/C5M) was slightly higher postoperatively when compared to preoperatively in the inguinal hernia group (P = 0.034). In addition, the results revealed a postoperatively lower type V collagen turnover level in the inguinal hernia group compared to controls (P = 0.012). In the incisional hernia group, the type V collagen turnover was higher after hernia repair (P = 0.004) and the postoperative turnover level was not different from the control group (P = 0.973). CONCLUSION: Patients with an inguinal hernia demonstrated a systemic and persistent type V collagen turnover alteration. This imbalance of the collagen metabolism may be involved in the development of inguinal hernias.

Development of a critical-sized ventral hernia model in the pig.

BACKGROUND: The pig is commonly used as a preclinical model for ventral hernia repair. However, no study has verified that an unrepaired surgically induced hernia (control) in the pig does not heal spontaneously but rather develops a persistent hernia. Without such verification in any given model, one cannot draw conclusions on the efficacy of the repair technique investigated. MATERIALS AND METHODS: Three surgically induced hernia models with increasing severity were created in eight pigs. These included 10-cm retrorectus partial-thickness (model 1) and 15-cm preperitoneal full-thickness (model 2) incisional defects and an 8 × 8 cm preperitoneal full-thickness excisional defect (model 3). Postoperative management included use of an abdominal binder, and in some cases, suction drainage, for 2 wk to support the repair and prevent seroma. Models were evaluated for persistence of hernia at 5 wk using clinical and radiographic assessments. RESULTS: All pigs developed clinical hernias after 2 wk of defect creation, but only models 1 and 3 had clinically persistent hernias at 5 wk. At 5 wk, the average defect area was 97 cm2 in model 1, 66 cm2 in model 2, and 245 cm2 in model 3. Dense fibrotic scarring was observed in the models with resolved hernias. CONCLUSIONS: Our results highlight the need to verify an unrepaired hernia injury model does not heal spontaneously prior to using it for hernia repair studies. The partial-thickness incisional model 1 and full-thickness excisional model 3 formed persistent hernias in pigs at 5 wk and should be further explored as models for investigating hernia repair strategies.

The 'AbdoMAN': an artificial abdominal wall simulator for biomechanical studies on laparotomy closure techniques.

PURPOSE: Incisional hernia remains a frequent complication after abdominal surgery associated with significant morbidity and high costs. Animal and clinical studies have exhibited some limitations. The purpose of this study was to develop an artificial human abdominal wall (AW) simulator in order to enable investigations on closure modalities. We hypothesized that a physical model of the human AW would give new insight into commonly used suture techniques representing a substantial complement or alternative to clinical and animal studies. METHODS: The 'AbdoMAN' was developed to simulate human AW biomechanics. The 'AbdoMAN' capacities include measurement and regulation of intra-abdominal pressure (IAP), generation of IAP peaks as a result of muscle contraction and measurements of AW strain patterns analyzed with 3D image stereo correlation software. Intact synthetic samples were used to test repeatability. A laparotomy closure was then performed on five samples to analyze strain patterns. RESULTS: The 'AbdoMAN' was capable of simulating physiological conditions. AbdoMAN lateral muscles contract at 660 N, leading the IAP to increase up to 74.9 mmHg (range 65.3-88.3). Two strain criteria were used to assess test repeatability. A test with laparotomy closure demonstrated closure testing repeatability. CONCLUSIONS: The 'AbdoMAN' reveals as a promising enabling tool for investigating AW surgery-related biomechanics and could become an alternative to animal and clinical studies. 3D image correlation analysis should bring new insights on laparotomy closure research. The next step will consist in evaluating different closure modalities on synthetic, porcine and human AW.

Abdominal wall reinforcement: biologic vs. degradable synthetic devices.

BACKGROUND: New biodegradable synthetic and biologic hernia implants have been promoted for rapid integration and tissue reinforcement in challenging repairs, e.g. at the hiatus or in contaminated wound fields. Interestingly, experimental data to support or falsify this assumption is scarce. METHODS: Synthetic (BioA®) and biologic implants (porcine and bovine collagen matrices Strattice® and Veritas®) have been tested in experimental onlay hernia repair in rats in observation periods of 30 and 60 days. The key outcome parameters were mesh integration and reinforcement of the tissue at the implant site over sutured and sealed defects as well as comparison to native abdominal wall. Macroscopic assessment, biomechanical analysis and histology with haematoxylin/eosin staining, collagen staining and van Willebrand factor staining for detection of neovascularization were performed. RESULTS: BioA® was well integrated. Although the matrices were already fragmented at 60 days follow-up, hernia sites treated with synthetic scaffolds showed a significantly enhanced tissue deflection and resistance to burst force when compared to the native abdominal wall. In porcine and bovine matrices, tissue integration and shrinkage were significantly inferior to BioA®. Histology revealed a lack of fibroblast ingrowth through mesh interstices in biologic samples, whereas BioA® was tightly connected to the underlying tissue by reticular collagen fibres. CONCLUSIONS: Strattice® and Veritas® yielded reduced tissue integration and significant shrinkage, prohibiting further biomechanical tests. The synthetic BioA® provides little inherent strength but reticular collagen remodelling led to an augmentation of the scar due to significantly higher burst force resistance in comparison to native tissue.

Prostheses size dependency of the mechanical response of the herniated human abdomen.

BACKGROUND: Hernia repairs still exhibit clinical complications, i.e. recurrence, discomfort and pain and mesh features are thought to be highly influent. The aim of this study is to evaluate the impact of the defect size and mesh type in an herniated abdominal wall using numerical models. METHODS: To do so, we have started from a FE model based on a real human abdomen geometry obtained by MRI, where we have provoked an incisional hernia of three different sizes. The surgical procedure was simulated by covering the hernia with a prostheses, and three surgical meshes with distinct mechanical properties were used for the hernia repair: an isotropic heavy-weight mesh (Surgipro @), a slightly anisotropic light-weight mesh (Optilene @) and a highly anisotropic medium-weight mesh (Infinit @). The mechanical response of the wall to a high intraabdominal pressure (corresponding to a coughing motion) was analyzed here. RESULTS: Our findings suggest that the anisotropy of the mesh becomes more relevant with the increase of the defect size. Additionally, according to our results Optilene @ showed the closest deformation to the natural distensibility of the abdomen while Infinit @ should be carefully used due to its excessive compliance.

Characteristics of the fibroplasia and collagen expression in the abdominal wall after implant of the polypropylene mesh and polypropylene/polyglecaprone mesh in rats.

PURPOSE: To compare fibroplasia and the resistance of the abdominal wall when polypropylene meshes and polypropylene/poliglecaprone are used. METHODS: Seventy-seven male Wistar rats were divided into three groups: Control Group (for resistance); Group E (polypropylene mesh); and Group U (polypropylene/poliglecaprone mesh). The animals in Groups E and U had a standard muscular and aponeurotic defect, with integral peritoneum, and correction with the mesh. Measurements were taken 4, 7, 14, 28 and 56 days after surgery. The resistance, and collagen density were studied. RESULTS: Resistance on the 56th day was similar in both meshes. The gain in resistance described an ascending curve for the polypropylene mesh and was irregular in the case of the polypropylene/poliglecaprone. Fibroplasia showed a gain in type I and type III collagen in both groups (p<0.001). Collagen III stabilized in the 14th day and collagen I continued to ascend. CONCLUSIONS: The gain in resistance of the polypropylene mesh is regular and ascending, whereas the polypropylene/poliglecaprone is not regular. The final resistance of both meshes is similar; the collagen density increases over time, and show the same inflammatory potential.

Experimental study of inflammatory response and collagen morphometry with different types of meshes.

PURPOSE: To compare an inflammation score and collagen morphometry after incisional hernia repair with four different meshes at two time points. METHODS: Four types of mesh were used to repair an abdominal wall incisional defect in Wistar rats: high-density polypropylene (HW/PP); low-density polypropylene (LW/PP); polypropylene mesh encapsulated with polydioxanone coated with oxidized cellulose (PP/CE); and expanded polytetrafluoroethylene (ePTFE). An inflammation score based on histological analysis and collagen morphometry was performed after 7 and 28 days after operation (POD). RESULTS: Compared to LW/PP group at 7 POD, HW/PP group had lower (p = 0.014) and PP/CE group had higher inflammation scores (p = 0.001). At 28 POD, higher scores were seen in all the other groups compared to the LW/PP group (HW/PP, p = 0.046; PP/CE, p < 0.001; ePTFE, p = 0.027). Comparing groups individually at 7 and 28 PODs, all demonstrated lower inflammation score values at 28 POD (HW/PP, p < 0.001; LW/PP, p < 0.001; PP/CE, p = 0.002; ePTFE, p = 0.001). At 7 POD, higher amounts of collagen were detected in ePTFE compared to HW/PP (p < 0.001) and LW/PP (p = 0.004) and in PPCE group compared to HW/PP (p = 0.022). At 28 POD, no statistically significant difference was found. Comparing groups individually at 7 and 28 PODs, HW/PP and LW/PP showed larger amounts of collagen at the 28th POD, without any statistically significant differences for the PP/CE and ePTFE groups. CONCLUSIONS: Inflammation scores decreased in all groups at 28 POD. Collagen deposition was higher for non-composite meshes at 28 POD.