Mesh Reinforcement Research Articles

Boosting Nitrate to Ammonia Electroconversion through Hydrogen Gas Evolution over Cu-foam@mesh Catalysts.

The hydrogen evolution reaction (HER) is often considered parasitic to numerous cathodic electro-transformations of high technological interest, including but not limited to metal plating (e.g., for semiconductor processing), the CO2 reduction reaction (CO2RR), the dinitrogen → ammonia conversion (N2RR), and the nitrate reduction reaction (NO3-RR). Herein, we introduce a porous Cu foam material electrodeposited onto a mesh support through the dynamic hydrogen bubble template method as an efficient catalyst for electrochemical nitrate → ammonia conversion. To take advantage of the intrinsically high surface area of this spongy foam material, effective mass transport of the nitrate reactants from the bulk electrolyte solution into its three-dimensional porous structure is critical. At high reaction rates, NO3-RR becomes, however, readily mass transport limited because of the slow nitrate diffusion into the three-dimensional porous catalyst. Herein, we demonstrate that the gas-evolving HER can mitigate the depletion of reactants inside the 3D foam catalyst through opening an additional convective nitrate mass transport pathway provided the NO3-RR becomes already mass transport limited prior to the HER onset. This pathway is achieved through the formation and release of hydrogen bubbles facilitating electrolyte replenishment inside the foam during water/nitrate co-electrolysis. This HER-mediated transport effect "boosts" the effective limiting current of nitrate reduction, as evidenced by potentiostatic electrolyses combined with an operando video inspection of the Cu-foam@mesh catalysts under operating NO3-RR conditions. Depending on the solution pH and the nitrate concentration, NO3-RR partial current densities beyond 1 A cm-2 were achieved.

Anatomic and functional results of ventral biological mesh rectopexy for posterior pelvic floor disorders.

Ventral mesh rectopexy (VMR) is the gold standard for rectal prolapse surgery, but the type of mesh reinforcement is still a matter of debate. The aim of this study was to assess the anatomic and functional results of a single center cohort of patients receiving ventral rectopexy with biological mesh compared to a reference group who had implantation of synthetic mesh. We also assessed the predictive factors for recurrence. Seventy patients (2015-2021) were included in the biological mesh group and were compared to a reference group of 345 patients operated on with a synthetic mesh (2004-2017). In the biological mesh group, the mean age of patients was 65 years (53-72). The main disorders of the posterior pelvic floor were rectal prolapse (30 cases) or rectocele (37 cases). Two patients had solitary rectal ulcer syndrome and one had internal prolapse. VMR was performed by a laparoscopic approach with robotic assistance in 93%. After a median follow-up of 12 (4.5-23) months, the anatomic recurrence rate was 10%. The median satisfaction score assessed in a telephone interview by a semi-quantitative scale from 0 to 10 was 7. Compared to the synthetic group, neither the morbidity rate (Dindo>2) (0.6% synthetic versus 1.4% biological mesh), nor the recurrence rate (12% synthetic versus 10% biological (ns) with an average interval of 13.5 versus 14 months, respectively) were statistically significantly different. VMR with biological mesh represents an alternative to synthetic mesh. Despite its resorbable nature, biological mesh does not seem to increase the risk of recurrence and offers satisfying functional results after a medium term follow-up.

Anterior reconstruction of the esophageal hiatus: a novel approach for the repair of large diaphragmatic hernias

Introduction: Paraesophageal hernias (PEH) often require surgical repair. The standard approach, primary posterior hiatal repair, has been associated with a high recurrence rate. Over the past few years, we have developed a new approach for repairing these hernias, which we believe restores the original anatomy and physiology of the esophageal hiatus. Our technique includes anterior crural reconstruction with routine anterior mesh reinforcement and fundoplication. Objective: To determine the safety and the clinical success of anterior crural reconstruction with routine mesh reinforcement. Material and methods: Data were collected retrospectively on 178 consecutive patients who had a laparoscopic repair of a symptomatic primary or recurrent PEH between 2011 and 2021 using the above technique. The primary outcome was clinical success, and the secondary outcome was 30 days of major complications and patient satisfaction. This was assessed by imaging tests, gastroscopies, and clinical follow-up. Results: Mean follow-up was 65 (SD 37.1) months. No intraoperative or 30 days postoperative mortality or major complications were recorded. Recurrence rate requiring a re-operation was 8.4% (15/178). Radiological and gastroenterological evidence of minor type 1 recurrence was 8.9%. Conclusion: This novel technique is safe with satisfactory long-term results. The outcome of our study will hopefully motivate future randomized control trials.

Flexural behavior of structure of laminated cementitious composites with different types of mesh reinforcements

In this study, 17 plates of cementitious ferrocement composite structure reinforced with two types of fabrics (jute and polypropylene) derived from biaxially oriented jute and polypropylene canvas with three reference unreinforced plates are experimentally investigated. The aim was to increase the flexural load carrying capacity and ductility of unreinforced laminated composite. The matrix was prepared using a ratio of 1:2:0.3 (Portland cement: sand: fly ash) by weight and water-to-cementitious material ratios (w/cm) of 0.4, 0.5, and 0.6. In accordance with ASTM C1609 procedure, the structural behavior of studied laminated composites with a size of 450 × 100 × 25 mm under a four-point load configuration, including first crack, maximum post cracking strength or modulus of rupture (MOR), deflection, toughness, crack pattern, and failure modes, are investigated with the effectiveness of type of fiber and the number of fabric layer reinforcements. The results indicate that types of fiber and number of layers of fiber have a significant effect on enhancement of resistance, strength, and ductility of the cementitious material mortars. The results showed that the first cracking strength generally decreased as the number of fibric layers increased. In comparison to the reference plates, the first cracking strength decreased by 92.8, 83.0, and 34.3% for plates reinforced with polypropylene fiber at 0.4 w/cm, as layer number increased from zero to six, eight, and ten, respectively. The post-flexural strength of the jute fiber-reinforced plates increased as layer number increased relative to the reference plate, whereas this was completely the opposite for polypropylene fiber-reinforced plates. The maximum flexural strength was 10.82 MPa for plates reinforced with jute fabrics whereas polypropylene fibers had a maximum flexural strength of 5.21 MPa. The post flexural strength of plates reinforced with jute fiber increased for w/cm ratio of 0.6 by 2.1, 68.0, and 78.4%, whereas it dropped for plates reinforced with polypropylene fiber by 6.7, 9.0, and 53.6% as layer number increased from zero to six, eight, and ten, respectively. Polypropylene fiber reinforced plates have a wider crack width than jute fiber reinforced plates and the effect of increasing layer number was not clear, but it did generally reduce crack spacing. A comparison of the maximum post-cracking strength against the first cracking strength indicated that jute fiber plates exhibited deflection hardening behavior, while the behavior was completely reversed for plates reinforced with PP fiber, whose curve behavior was softening deflection. The maximum deflection recorded 18.5 mm, and the energy absorption and deflection capabilities of jute fabric reinforced composites have both improved with layer number increased. Conversely, for polypropylene fabric reinforced composites, where the maximum deflection was 21 mm and the deflection and energy absorption capacity decreased as layer number increased. However, laminates made of polypropylene fabrics displayed significantly weaker bonds than jute fabric laminates, resulting in the appearance of horizontal cracks that separated the Polypropylene laminate layers and spread towards both supports emphasized by SEM test. As a result, the indices described in ASTM C1608 specifications cannot be generalized to the behavior of such materials for such a curve because, based on the experimental data, the calculated residual strength ratio exceeded 100% in only three plates. The toughness values in the composites suggest that this eco-friendly, ductile composite has a promising future in the construction industry.

Biosynthetic Mesh Reconstruction after Abdominoperineal Resection for Low Rectal Cancer: Cross Relation of Surgical Healing and Oncological Outcomes: A Multicentric Observational Study.

Local wound complications are among the most relevant sequelae after an abdominoperineal resection (APR) for low rectal cancer. One of the proposed techniques to improve the postoperative recovery and to accelerate the initiation of adjuvant chemotherapy is the mesh reinforcement of the perineal wound. The aim of the current study is to compare the surgical and oncological outcomes after APR performed with a biosynthetic mesh reconstruction versus the conventional procedure. From 2015 to 2020, in two tertiary centres, the surgical outcomes, the wound events (i.e., surgical site infections, wound dehiscence and the complete healing time) and the oncological outcomes (i.e., time length to start adjuvant chemo-radiotherapy, an over 8-week delay in chemotherapy and the recurrence rate) were retrospectively analysed in patients undergoing APR reinforced with biosynthetic mesh (Group A) and conventional APR (Group B). Results Sixty-one patients were treated with APR (25 in Group A and 36 in Group B). Patients in Group A presented lower time for: healing (16 versus 24 days, p = 0.015), inferior perineal wound dehiscence rates (one versus nine cases, p = 0.033), an earlier adjuvant therapy start (26 versus 70 days, p = 0.003) and a lower recurrence rate (16.6% vs. 33.3%, p = 0.152). In our series, the use of a biosynthetic mesh for the neo-perineum reconstruction after a Miles' procedure has resulted in safe, reproducible results affected by limited complications, guarantying a rapid start of the adjuvant therapy with clear benefits in oncological outcomes. Further randomized clinical trials with long-term follow-up are needed to validate these results.

The utilization of an absorbable mesh after ostomy reversal does not decrease incisional hernia rates

BackgroundPostoperative ostomy reversal hernias are common and can create strain on the healthcare system.There is little literature evaluating the utilization of absorbable mesh following ostomy reversal. The effect on subsequent hernia rates at our institution has not been evaluated. We examine if the addition of absorbable mesh decreases the postoperative hernia rate in our patient population. MethodsWe performed a retrospective review of all ileostomy and colostomy reversals. Patients were divided into two groups based on whether an absorbable mesh was used at ostomy closure or not. ResultsHernia recurrence rates were lower in the group that had mesh reinforcement (8.96%) vs the group that did not receive a mesh (14.8%) though this was not statistically significant (p = 0.233). ConclusionProphylactic use of an absorbable biosynthetic mesh did not alter the rate of incisional hernia rates following ostomy reversal in our cohort of patients.

V-007 Robotic repair of a bilateral recurrent groin hernia in a kidney transplant patient

Abstract Aim Due to the increased frequency of kidney transplantations and the high incidence of inguinal hernia in men, the coincidence of both features is not uncommon. Material & Methods A 58-year-old male patient with a history of a kidney transplantation in the right fossa due to bilateral shrivel kidneys, presented with a bilateral recurrent incisional hernia. Two years before he had an anterior bilateral groin hernia repair; a Liechtenstein repair on the left side and a partial preperitoneal repair with mesh reinforcement on the right side. Results The case was approached via a robot assisted TAPP (transabdominal preperitoneal) procedure to perform the preperitoneal dissection of the myopectineal orifices. At the region of the right inguinal hernia, the normal anatomy was distorted, due to the extraperitoneal course of the donor ureter which was freed accordingly. A partial mesh excision of the previous mesh was performed. The preperitoneal dissection area was covered with a self-gripping mesh. The postoperative course was uneventful. Conclusions The extraperitoneal course of the ureter in a kidney transplant patient challenges the surgical repair of an inguinal hernia. In primary groin hernias an anterior approach seems best suited, but in case of a recurrence after a previous anterior approach, a laparoscopic approach is a possible though challenging surgical option.

V-017 LAPAROSCOPIC TRANSVERSUS ABDOMINIS RELEASE (L-TAR) VIA TOTALLY EXTRAPERITONEAL REPAIR (TEP)

Abstract Aim Posterior component separation via transversus abdominis release (TAR) allows the treatment of complex incisional hernias, although it is associated with high morbidity rates. In recent years, the laparoscopic TAR was introduced, showing the benefits of the minimally invasive surgery such as less postoperative pain, less surgical site infection, and a shorter hospital stay. When compared to the transabdominal preperitoneal (TAPP) approach, the Totally Extraperitoneal Repair (TEP) technique avoids entry into the abdominal cavity, making it a suitable strategy for patients with previous abdominal surgeries. Material & Methods We present the case of a 68-year-old male with three previous umbilical repairs, one of them with mesh. He consulted for a recurrent umbilical hernia associated with a large weakness on the abdominal wall in the left flank. He complained that it increased in size and significantly altered his quality of life. Computed tomography scan revealed weakness and atrophy of the abdominal wall muscles in the left anterolateral area, which measured 22×10×15 centimeters. Surgical repair was decided and a TEP-TAR technique with mesh reinforcement was performed to restore the abdominal wall anatomy. Results The patient had an uneventful postoperative course and was discharged 36 hours after surgery. No recurrence was observed at 6 months. Conclusions Complex abdominal wall defects are challenging. The use of minimally invasive advanced techniques is feasible and safe, making it a suitable tool for the management of this type of cases.

V-020 Botulinum Toxin: not just aesthetics anymore

Abstract Introduction Surgical repair of recurrent abdominal incisional hernia can be challenging. The aim should be a tension-free, mesh reinforced midline fascial closure. Different methods have been described to achieve this primary fascial closure. Botulinum toxin (BT) is a neurotoxin that when injected into muscle tissue, causes a temporary flaccid muscle paralysis. This effect can be applied to the lateral abdominal wall muscles, thereby facilitating midline rectus muscles re-approximation and defect closure. Clinical Case We present a case of a 58 year old female, with a history of right hemicolectomy and ileostomy, that underwent subsequent stoma closure one year after. She presented with a 12 cm defect width incisional hernia and right rectus muscle atrophy. We demonstrate the preoperative injection of BT using the Zielinski technique in a consultation room with no need for patient monitoring or anesthesia. Four weeks later, the patient underwent open repair with bilateral transversus abdominis release and retromuscular mesh reinforcement. The defect was closed without tension and the postoperative period was uneventful. Patient was discharged on postoperative day 4. Conclusion Preoperative BT injection as a selective muscle chemical component paralysis is a safe, easy to perform and effective technique that aims to counteract the chronic muscle retraction observed in large ventral hernias. BT in combination with advanced ventral hernia repair techniques, may help provide the crucial extra tissue mobility required to achieve primary closure, with the added advantage of less postoperative pain, thereby contributing to early patient discharge.

P-047 REDUCING THE RISK OF MESH EROSION IN A MODIFIED RETROMUSCULAR SUGARBAKER TECHNIQUE FOR PARASTOMAL HERNIA REPAIR

Abstract Aim Modified retromuscular Sugarbaker procedure (SP) is a promising approach for parastomal hernia repair. However, its potential complications, including the risk of mesh erosion, encourages us to develop other techniques of mesh placement. We propose an addition to this parastomal retromuscular mesh reinforcement. Materials and Methods We present the case of a 53 year old-woman, with a history of proctocolectomy with end ileostomy due to anal adenocarcinoma, undergoing emergency surgery due to parastomal hernia incarceration. Sugarbaker repair was performed placing inlay composite mesh fixed with reabsorbable tackers. Subsequently, the patient was admitted for recurrent parastomal hernia and midline ventral hernia surgery. Results We performed a modified retromuscular SP as described by Pauli in 2016. After midline laparotomy, hernia content was reduced and extensive retromuscular dissection with transversus abdominis release (TAR) performed, placing a wide retromuscular polypropylene mesh prior to closing parastomal fascial defect. Stoma was parietalized from lateral to medial in an S-shaped configuration. We placed a segment of bioabsorbable mesh covering the parietalized stoma to avoid direct contact with the polypropylene mesh. No recurrence was detected 3 months after surgery, pending reassessment at 6 months. Conclusions This repair provides the benefits of an open posterior component separation with TAR, maintaining the biomechanics of a functional abdominal wall, whilst offering the advantages of mesh reinforcement in a modified Sugarbaker configuration. Our experience with this novel technique seems promising. Rate of mesh erosion is yet to be defined and requires long-term studies before widespread adoption, with special concern on mesh placement.

OC-121 TRANSVERSUS ABDOMINIS RELEASE (TAR) IN CONTAMINATED FIELDS

Abstract Aim Complex abdominal wall reconstructions in contaminated fields is a controversial topic. Although some prefer a staged approach, others advocate performing a single surgery even associating bowel and colon resections with synthetic mesh reinforcement. We aimed to evaluate and compare results of Transversus Abdominis Release (TAR) in clean and contaminated fields. Material & Methods A consecutive series of patients undergoing TAR for complex incisional hernias between 2014 and 2022 with a minimum of 6-month follow-up was included. The cohort was divided into 2 groups according to the Modified Hernia Grading System of the Ventral Hernia Working Group (VHWG): G1, Grade 1 (low risk) and Grade 2 (comorbid); and G2: Grade 3 (contaminated). Demographics, operative and postoperative variables were analyzed and compared. Results A total of 69 TAR repairs were performed; 54 (78,3%) were included in G1 and 15 (21,7%) in G2. There were no differences in overall morbidity at 30 postoperative days (G1 19% vs G2 27%; p=NS). Surgical Site Infection (SSI) was significantly higher in G2 (G1 11,1% vs G2 46,6%; p=0,01), however Surgical Site Occurrence Requiring Procedural Intervention (SSOPI) was similar in both groups (G1 5,5% vs G2 11,1%; p=NS). No mesh removal was recorded. After 31 ± 10 months follow-up, the recurrence rate was 2.9% (2 patients). Conclusions TAR technique is feasible and safe for the treatment of complex hernias in contaminated fields. Although an increase in SSI rate might be observed, most cases are superficial without the need for invasive procedures.

P-070 ROLE OF MESH AUGMENTATION IN TRAM FLAP DEFECTS AFTER BREAST RECONSTRUCTION: LITERATURE REVIEW

Abstract Aim The aim of this study was to assess the problem of hernia occurrence in patients after transverse rectus abdominis flap in breast reconstructive surgery and the influence of using donor site reinforcement with mesh to prevent bulging and hernia. Method Literature searches were performed using databases, using key terms to include related articles in the last ten years. Results Out of 65 articles found by the research, 7 articles included in this review, risk factors were identified as obesity, smoking, unipedicule vs bipedicle, mesh vs non-mesh repair. 5 of the included articles involved retrospective study with 6 to 160 patients and follow up period 6 to 48 months, one double blinded study and one was cost utility study retrospective. it is showed that TRAM reconstruction associated with hernia in 18% and 63% had abdominal bulging. using mesh reinforcement reducing bulging 2% to 6% and hernia to 1% to 2%, Consideration should be given particularly in high-risk populations. Conclusion Although the literature about the best way to deal with TRAM defect has not been published yet, this review shows the important of mesh augmentation, it magnified the effect of that on patient with high risk for hernia or bulging.

Flexural performance of concrete beams internally reinforced with steel, geogrid and GFRP meshes

The focus of this study is to evaluate the internal reinforcement effect using different material meshes on the flexural capacity of concrete beams. For this purpose, eleven experimental reinforced concrete beams were tested under four-point bending. The beams were all made of normal concrete with a 150 × 200 mm2 rectangular cross-section and a length of 1200 mm. The conventional flexure and shear steel bar reinforcements were identical for the eleven beams. The reference beam was made without any internal mesh reinforcement, while the rest ten beams were reinforced with three different types of mesh materials, which were incorporated in different numbers of layers and different configurations. The used meshes were steel, geogrid and glass-fiber reinforced polymer (GFRP). One beam with U-shape mesh was made from each material, with the mesh wrapping the stirrups and extending vertically for 50 mm. In the experimental program, failure mode, load-deflection relationship, load capacity and ductility were the main characteristics that have been investigated. The test results showed that the percentage increase in the failure load capacity of the composite beams was approximately 3–25% compared to the reference beam. Furthermore, the beams with U-shape mesh configuration exhibited 17% increase in the load capacity comparing with their straight mesh counterparts. Similarly, the ductility index showed higher percentage improvement approximately 82–136% when layer number increased from 1 to 3 layers.

Endoscopic treatment of diastasis recti: Training method and literature review

Endoscopic treatment of diastasis rectus abdominis offers the possibility of correcting the condition without complete abdominoplasty. The purpose of this study was to develop a training method on fresh cadavers models based on a literature review on this surgery. The endoscopic procedure considered involved the insertion of a 10mm suprapubic trocar and of 5mm trocars in each iliac fossae. The muscle suture is done using running barbed suture. The surgery was performed on eight fresh cadavers to estimate the learning curve for this intervention, which was estimated with the CUSUM method. A systematic literature review in the PubMed database was performed, and 20 articles that met the inclusion criteria were analyzed. The learning curve threshold was reached after 6 operations and can be separated into two phases. The most common complication of this surgery is seroma, it is encountered in 3 to 27% of cases according to the studies. Diastasis recurrence is rare, occurring in less than 2% of cases. In comparison, open surgical treatment of diastasis recti is associated with a higher risk of hematoma, skin necrosis and longer operating times. Recurrence rates are similarly low after open and endoscopic repair. Mesh reinforcement is indicated in cases of diastasis wider than 5cm, diastasis recurrence, severe musculoaponeurotic laxity, or hernia larger than 1cm. The data in the literature indicate that laparoscopic surgery is an efficient and safe approach to correct diastasis of the rectus muscles and can be offered by plastic surgeons to selected patients.

Giant hiatal hernia: A review of the clinical presentation, surgical technique, and operative video

Introduction: Giant hiatal hernia represents 0.3–15% of all hiatal hernia. Its complication such as the strangulation of the stomach are life-threatening. Therefore, in most of the cases it must be surgically handled. Case Report: We report the case of a 74-year-old patient with giant hiatal hernia. He presented with sub-acute symptoms (e.g., vomiting, appetite loss, and hematemesis). Considering the symptomatology and complementary tests, we decided to perform a laparoscopic hernia repair using mesh reinforcement. We provided a commented operative video to describe the surgical procedure. We then discussed the surgical technique and decided how to conduct a safe and efficient repair. Conclusion: A surgical approach is the recommended treatment in most giant hiatal hernia due to its life-threatening complications. The technique should be tailored to the patient. Although there is no consensus whether to use a mesh reinforcement, we believed that a cautious mesh placement should be considered when the crura are of poor quality. Surgeons should also be cautious with the fundoplicature and the risk of stricture, therefore we propose the systematic use of a tube to test the passage in the esophago-gastric junction.

15. Comparative Analysis of Abdominoplasty with and without Concurrent Hernia Repair: An Assessment of a Reconstructive Problem in a Cosmetic Patient Population

PURPOSE: The risks and benefits of performing small fat-containing ventral or umbilical hernia repair (HR) during cosmetic abdominoplasty remains a reconstructive and aesthetic challenge for plastic surgeons. This study aimed to compare clinical outcomes in patients undergoing abdominoplasty with concurrent HR and abdominoplasty alone. METHODS: Patients (2015-2021) who underwent abdominoplasty with and without a concurrent HR by a single surgeon were identified. Patients were stratified by concurrent HR. All hernia patients underwent primary fascial repair, without the use of mesh reinforcement. Demographics, surgical site occurrences (SSO) and cosmetic complications, including delayed healing and necrosis, were assessed. Risk adjusted modeling was utilized to compare HR with clinical outcomes. RESULTS: One-hundred and eleven patients underwent abdominoplasty, 67 (60.4%) had concurrent HR. No significant difference in demographics was identified between groups including mean BMI (HR=27.5 kg/m2 and No HR= 26.7 kg/m2, P=0.79), and number of previous repairs (P=0.31). After a mean follow-up of 1.4 years, hernia recurrence rate was 3% (n=2), which was exclusive to umbilical defects. After controlling for demographics, there was no difference in risk of SSO (OR 1.02 [0.31-3.36] P=0.978), cosmetic complications (OR 0.80 [0.14-4.57] P=0.805), readmissions (6.06% vs. 0%, P=0.336), reoperations (18.18% vs. 3.03%, P=0.299), or procedure length (-7.23 minutes [-29.40-14.93] P=0.522), compared to patients who underwent abdominoplasty alone. CONCLUSION: Abdominoplasty with concurrent HR can be performed safely and effectively, with no increase in adverse outcomes or cosmetic complications. The value of mesh-free HR with abdominoplasty is the ability to achieve an enhanced aesthetic and mitigate long-term abdominal morbidity.

Safety Evaluation of Plain Concrete Lining Considering Deterioration and Aerodynamic Effects

With an increase in the service time of high-speed railway tunnels, various defects caused by construction-quality defects in the secondary lining begin to appear. How to evaluate the safety of such tunnels and take countermeasures is very important for the safe operation of tunnels. Based on the load-structure method and a numerical simulation, this paper studied the short-term and long-term safety of the missing section of anti-crack reinforcement mesh in the plain concrete lining of a high-speed railway mountain tunnel. The short-term safety evaluation considered the influence of negative pressure caused by aerodynamic effects. The long-term safety evaluation considered the combined influence of the surrounding rock and concrete deterioration and the negative pressure and concrete fatigue damage caused by aerodynamic effects. The results showed that under the negative pressure generated by aerodynamic effects, the minimum tensile safety factor of the lining in the defective section increased by 3.8%, while the minimum compressive safety factor of the lining decreased by 7.9%. The negative pressure generated by the aerodynamic effects had little impact on the short-term safety of the lining in the defective section. During the long-term safety evaluation, the overall safety of the defective section decreased significantly, and the minimum tensile and minimum compressive safety factors of the lining decreased by 59.4% and 66.8%, respectively. The calculation results for the initial design do not meet the long-term design requirements and cannot guarantee the long-term safe operation of the tunnel. Finally, two new strengthening methods of galvanized steel mesh-short bolts and galvanized corrugated steel plate-short bolts were proposed to strengthen the defective section of the concrete lining, so as to improve the ultimate bearing capacity and toughness of the plain concrete lining structure.

BOCHDALEK HERNIA IN ADULTS: A CASE SERIES OF A RARE DEFECT

Diaphragmatic hernias are more common among neonates and infants. Smaller defects may remain asymptomatic in childhood and present later in adult life. Congenital diaphragmatic hernias in adults are usually asymptomatic or may present with symptoms arising due to mass effect on the lungs and/or due to dysfunction of herniated organs. The omentum and transverse colon commonly appear in the herniated sac. However, larger defects in the diaphragm may also cause other parts of the intestine, spleen, and kidney (of either side) to herniate into the thoracic cavity. We present a case series of three adults with left-sided Bochdalek hernia, which was noted as an incidental finding. The size of the defects in the left hemidiaphragm in all the cases were large enough, 74.0mm, 57.0mm and 62.0mm respectively, to cause significant herniation of abdominal structures. During the operative treatment, we preferred the abdominal approach in all the cases: in case one and three for better reduction of organs and repair of the large defect; and in case two as obstruction of the bowel was suspected. The defect in case one and three was repaired by mesh reinforcement while in case two, a primary repair of the defect was done with sutures followed by fixation of mesh over it. Congenital diaphragmatic hernia in adults almost always necessitates surgical repair of the defect to avoid complications like strangulation or incarceration of the herniated structures.

Experimental and numerical investigation of transient dynamic response on reinforced concrete tunnels against repeated impact loads

An attempt has been made to study the transient dynamic response of small scale reinforced concrete tunnels against repeated impact loads. A total of four semi-cylindrical tunnels of M25 grade concrete having length, base width and thickness as 1.2, 0.5 and 0.05 m were prepared and tested against the mass of the impactor of 104 kg. The reinforcement mesh of ∅6 mm with 60 mm c/c spacing was used. The specimens were kept at the earth's surface which defines the boundary conditions proximity to the actual tunnels. The yield stress of the steel bars was 415 MPa and the resulting percentage reinforcement was 0.4%. The RCC tunnel rests on a soil bed that has a specific weight of 1850 kg/m3. The drop height against samples 1 and 2 was 1.5 and 2.3 m, respectively, whereas samples 3 and 4 were studied against a 3 m drop height under repeated loading. The experimental results were recorded in terms of impact force, residual displacement and damage pattern. It was observed that sample 1 offered resistance up to five hits whereas samples 2 and 3 were found to offer resistance up to four and two hits, respectively. The numerical investigations were performed using the ABAQUS/EXPLICIT software and the concrete, reinforcement steel and the soil element were modelled by using the Concrete Damaged Plasticity model, Johnson-cook model, and Drucker-Prager model, respectively. The results obtained from the simulations were found in good agreement with the experimental results of samples 2 and 3. However, the numerical results of sample 1 were able to complete up to the fourth hit and simulation on the fifth hit was not performed due to the complete loss of concrete material stiffness at the fourth hit. Further, the simulations were conducted considering parameters such as varying length and base width of the tunnel in order to predict the damage intensity of the tunnel. The Mises stresses were found reduced with an increase of the tunnel length up to 3 m, thereafter the same was found to increase with the increase of tunnel length, however, the deformation in the tunnel was found to decrease with an increase in the length of the tunnel. It was also concluded that the tunnel base width is an important parameter that affects the Mises stress resulting in global stability to the structure and further restricting the stress concentration to a localized failure.

Comparison of Outcome between Ostomy Closure with Permanent Synthetic Mesh and Conventional Technique without Mesh to Prevent Incisional Hernia

Background: Stomal site incisional hernia is a common complication following ostomy closure. Prophylactic mesh reinforcement of the fascial defect is typically not considered due to the contaminated nature of the case. The effectiveness of prophylactic mesh placement at the time of stoma closure is unknown because of fear of mesh infection and subsequent wound complications. Purpose: To compare the results obtained by placing synthetic mesh in the stoma site during closure with conventional technique without mesh to prevent incisional. Patients and Methods: Prospective interventional study had been designed to compare the outcome of permanent synthetic mesh placement at the time of ostomy closure. Total 45 patients were selected purposively who were candidates for ostomy closure and presented at the Department of Colorectal Surgery, Bangabandhu Sheikh Mujib Medical University (BSMMU) from April 2019 to September 2020 and divided into two groups (no mesh and mesh). In the mesh group, permanent synthetic mesh (ProleneTM – Polypropylene) was placed. Primary outcome, incisional stomal hernia was assessed at regular follow-up for one year along with associated morbidities. Results: The primary outcome of this study i.e. incisional hernia (stomal site) was observed among 1 (4.8%) patients at 4th week, 3 (14.3%) at 3rd month, 7 (33.3%) at 6th month and 8 (38.1%) at 12th month follow-up in no mesh group. And, only 1 patient at 6th month and 12th month follow-up had hernia in the mesh group (Figure 3). There was no difference statistically between no mesh and mesh groups at 4th week and 3rd month but significant difference found at 6th and 12th month follow-up (p=0.280, p=0.344, p=0.033 and p=0.017, respectively). Conclusion: Prophylactic placement of permanent polypropylene mesh during ostomy closure placement significantly reduced the rate of incisional hernia without any additional morbidity. Placement of mesh was found to be both safe and effective.