Mesh Position Research Articles

Management and outcome of mesh infection after abdominal wall reconstruction in a tertiary care center

PurposeAbdominal wall reconstruction is a common surgical procedure, with a post-operative risk of mesh-associated infection of which management is poorly known. This study aims to comprehensively analyze clinical and microbiological aspects of mesh infection, treatment modalities, and associated outcomes.MethodsPatients with abdominal mesh infection were included in a retrospective observational cohort (2010-2023). Patients characteristics and management were described, and determinants for failure were assessed by logistic regression and treatment failure-free survival curve analysis (Kaplan-Meier).ResultsTwo hundred and nine patients (median age, 62 [IQR, 55-71] years) presented a mesh infection occurring within 15 (IQR, 7-31) days after surgery, mainly as an abdominal wall or deep abscess (n=189, 90.4%). Infection was polymicrobial in 89/166 (79.4%) cases, S. aureus (n=60, 36.1%), Enterobacteriaceae (n=60, 36.1%) and anaerobes (n=40, 24.1%) being the most prevalent pathogens. Surgery was performed in 130 (62.2%) patients, associated with a 13.5 (IQR, 8-21) day course of antimicrobial therapy in 172/207 (83.1%) cases. Sixty-three (30.1%) treatment failures occurred, associated with previous multiple abdominal surgeries (OR, 3.305; 95%CI, 1.297-8.425), complete mesh removal (OR, 0.145; 95%CI, 0.063-0.335) and antimicrobial therapy (OR, 0.328; 95%CI, 0.136-0.787). The higher failure rate of conservative strategies was associated with symptom duration >1 month (OR, 3.378; 95%CI, 1.089-4.005) and retromuscular mesh position (OR, 0.444; 95%CI, 0.199-0.992).ConclusionMesh infection is associated with high treatment failure rates. Complete mesh removal coupled with targeted antibiotic therapy is associated with better outcomes. Conservative treatment strategies must rely on careful patient selection based on symptom duration and mesh placement.

Laparoscopic Incisional Hernia Mesh Repair With And Without Defect Closure

Objectives: As a systematic review, the present paper is designed to compare laparoscopic incisional hernia mesh repair with or without mesh defect after evaluating the rates of recurrence, complications, and postoperative recovery. Study Design: A prospective study. Place and duration of study: From May 2024 to October 2024 General Surgery Department Jinnah Post Graduate Medical Centre Karachi. Methodology: 100 patients drawn through random sampling. Two groups of fifty patients each were operated, the first having Laparoscopic hernia repair with defect closure, the second having it without defect closure. Mesh positioning and location were aligned; follow-up extended to 12 months majoring on recurrence, bulge, and pain after surgery. Quantitative data analysis as well as qualitative data analysis included use of p-values and standard deviations for comparison between the groups. Results: Table 3 demonstrated the mean times to first recurrent event; the recurrence rate in defect closure group was 6% and in non-closure group it was 10% with p value 0.04; statistically significant. New wall formation was symmetrical in 18% of patients with defect closure and 34% without (p=0.03). The mean postoperative pain scores were also comparable (3.2± 0.6 vs 3.4 ± 0.7; p=.35; not significant). There were no postsurgical complications of the noted surgery as a whole. Conclusions: Closure of the defect in laparoscopic incisional hernia repair is associated with a lower recurrence rate and minimal bulging in comparison to non-closure laparoscopic incisional hernia repair with similar pain scores. Defect closure should be entertained for patients who desire better esthetic and clinical appearance, and the study demonstrated feasibility in patients with moderate size of hernias. Keywords: Incisional hernia, Laparoscopy, Defect closure, Mesh repair

A study of the dynamic transmission efficiency of the cycloid pin gear pair under dynamic characteristic analysis

Transmission efficiency is one of the main technical indicators for evaluating the transmission performance of a cycloid pin gear planetary reducer. The cycloid pin gear pair is a crucial component of such a reducer. When the design parameters of the cycloid pin gear pair are determined, its transmission efficiency is often considered a constant, which significantly hinders accurate calculations of the transmission efficiency of the cycloid pin gear planetary reducer. To address this issue, this paper introduces a dynamic transmission efficiency analysis method specifically tailored for the cycloid pin gear pair, grounded firmly in dynamic characteristic analysis. Firstly, a comprehensive and meticulous dynamic performance analysis method is proposed for the cycloid pin gear pair, enabling precise calculations of dynamic transmission efficiency. Secondly, an optimization framework is introduced, with a primary focus on enhancing the transmission efficiency of the cycloid pin gear pair. A transmission efficiency assessment model is established as the objective function, which takes into account the pressure angles of both the driving gear and the driven gear at the meshing position. To demonstrate the practical utility and effectiveness of these methodologies, an illustrative example is presented. The results obtained from this example underscore a remarkable improvement in the overall transmission performance of the system. This enhancement is characterized by substantial gains in transmission efficiency and effective vibration control, highlighting the significance and practicality of the proposed approaches.

Calcium sulfate-based load-bearing bone grafts with patient-specific geometry

The treatment of bone defects with complex three-dimensional geometry presents challenges in terms of bone grafting and restoration. In this paper, we propose a rapid and effective method that uses 3D printing, ceramic casting, and the incorporation of mesh reinforcement to create load-bearing bone grafts with patient-specific three-dimensional geometry. Using two types of facial bones as examples, we show that this fabrication method has a high degree of geometrical fidelity. We also experimentally study the fracture behavior of six different architectures designed for the treatment of mandibular defects, one of the principal load-bearing facial bones. These design configurations include un-reinforced calcium sulfate samples, and samples reinforced with one or two layers of stainless steel, poly (lactic acid), and poly (L-lactic acid). The results suggested a trade-off between energy dissipation and maximum load based on the position of the metal mesh in the sample. Samples reinforced with one layer of metallic mesh at their lowermost margin exhibited a 17% higher stiffness and a 21.3% higher peak load, while samples with a layer of metal mesh embedded within dissipated 16% more energy. Samples with two layers of metallic mesh demonstrated the highest improvements among all samples, dissipating 5767.85% more energy and exhibiting a peak load 145.6% higher compared to plain CS. The improvements in stiffness for SD, SL, and S2 were 3%, 21.3%, and 21.9% respectively compared to the plain ceramic. In contrast, PLA mesh improved energy dissipation by 96.71% but reduced the peak load by 29.18%, while PLLA mesh decreased both the peak load and the dissipated energy by 13.05% and 35.31%, respectively. While PLA mesh reduced stiffness by 11% compared to plain CS, PLLA mesh-reinforced samples were slightly stiffer than pure CS by 1.6%.

BN SO28 - Dual Mesh Technique in Revisional Complex Laparoscopic Repair of Recurrent Paraesophageal Hernia (PEH)

Abstract Background Mesh Augmentation in laparoscopic repair of complex PEH has been an ongoing debate with regards to its risk profile and success rate in reducing hernia recurrence.1 There have been concerns regarding the deployment of non-absorbable mesh around the hiatus resulting in erosion and stricture, which may lead to oesophagectomy or gastrectomy.2 Absorbable mesh has been introduced with appealing advantages of lower mesh-related morbidities, however its high cost and unclear long-term durability remains questionable for its role as an ideal mesh.2 Method This is the case of a 65-year-old patient with chronic reflux symptoms undergoing revisional complex laparoscopic repair of recurrent type 4 PEH. The focus of this video is using a dual mesh technique involving fixation of a non-absorbable synthetic mesh at least 15mm from the oesophageal wall, reinforced with placement of an absorbable biosynthetic mesh which is in contact with the hiatus boundary. Results With regards to position of the permanent synthetic mesh, direct contact with the oesophagogastric wall should be avoided due to complications secondary to erosions and strictures. The deployment of a second mesh of absorbable material is preferred in this patient for hiatal reinforcement to reduce risk of recurrence due to friability of adjacent tissues. Conclusion The dual mesh technique aims to overcome the limitations of both types of mesh materials while preserving their individual benefits, expectantly reducing recurrence.

Analysis of tooth root three-dimensional fatigue crack initiation, propagation, and fatigue life for spur gear transmission

The gears in aviation gear systems are susceptible to fatigue fracture due to high-speed, heavy-load, and load alternation operating conditions. Therefore, a numerical calculation model with multiple mesh positions loading form has been proposed in this paper to analyze the fatigue crack initiation and propagation behavior, and to estimate the fatigue life of these gears. The fatigue life of the gear is determined by separately calculating the fatigue crack initiation life and the fatigue crack propagation life. The tooth root fatigue stress and the fatigue initiation life are calculated by the multi-axial fatigue life prediction method with the Smith-Watson-Topper criterion and the critical plane method. Afterwards, the tooth root stress–strain field is calculated in Finite element (FE) software and the stress intensity factors of the crack tip are calculated in three-dimensional (3D) crack analysis software. Then, the tooth root fatigue crack propagation trajectory and the fatigue crack propagation life are obtained separately. Finally, the influence mechanism of the loading conditions, the geometry parameters of gears, and the initial crack positions on the tooth root fatigue crack initiation life, propagation life, and fatigue crack propagation trajectory are analyzed, and a tooth fatigue test bench is built for verifying the crack propagation trajectory.

Pooperacinių išvaržų gydymo naudojant tinklelį atokieji (daugiau negu penkerių metų) rezultatai: literatūros apžvalga

Introduction. Postoperative hernias occur in 10–15% of patients. Considering the increase in the incidence of complications with the number of operations it is crucial to choose the optimal surgical technique in order to control the complications rate. This literature review summarizes previous studies on the treatment of postoperative hernias with mesh, comparing complication and recurrence rates according to surgical technique and mesh position. Methods. A thorough search was conducted on the PubMed database to retrieve literature on recurrence, chronic pain, haematoma, seroma, and surgical site infections rates. The results were meticulously summarised and used to confidently compare open and laparoscopic surgical techniques, as well as “sublay” and “onlay/inlay” mesh positions in more than 5-year follow-up. Results. The analysis was conducted on five publications that met the selection criteria. The results showed that laparoscopically treated hernias had lower recurrence and chronic pain rates, but more frequent haematomas. The presence of wound infections, BMI >30, treatment of recurrent postoperative hernias, multiple fascia lesions, enterotomy, larger abdominal wall defect and longer operative time were observed to be associated with higher recurrence rates. The position of the sublay mesh is associated with less frequent seromas, surgical infections, and recurrence compared to the onlay/inlay position. Studies have reported the superiority of large-pore lightweight polypropylene multifilament mesh over the same heavyweight mesh in managing postoperative hernias. Lightweight mesh is linked to a lower risk of hernia recurrence and higher compliance with the abdominal wall. Conclusion. Laparoscopic surgery is associated with lower rates of recurrence and chronic pain, but a higher frequency of haematomas. The sublay mesh position is associated with lower rates of seromas, surgical infections, and recurrence.

EP281 - Outcomes of the Abdominal Wall Reconstruction in a District General Hospital

Abstract Background The aim of this study was to explore the outcomes of abdominal wall reconstruction surgery by assessing postoperative complications and recurrence. Methods This is a retrospective case series. All patients who underwent abdominal wall reconstruction between 2018 and 2023 were included and followed up for complications and recurrence till January 2024. Patient demographics, operative parameters and postoperative complications were extracted in an Excel sheet, and data analysis was performed with SPSS 27 software. Results Forty-two patients were included in this study with a median age of 61.5 (34-83) and 1.2: 1 female: male gender distribution. Moreover, 41% of the included patients had a BMI > 35, and 47.6% were smokers. The type of hernia was incisional in 50% and recurrent hernia in 31%, and the defect size was > 10 centimetres in 48% of the included cohort. The type of operation was as follows: Rives-Stoppa (50%), TAR (24%), and combined procedure (26%). additionally, only 18% had their operation laparoscopically, and the position of mesh was retro-rectus in 88% of the cases. Post-operative complications were SSI (11.9%), seroma (28.6%), haematoma (7.1%), re-operation (9.5%), entero-cutaneous fistula (2.4%), and Hernia recurrence (4.7%) at a median follow-up of 42.5 months. Length of hospital stay was < 5 days in 48% of patients. Conclusion The Component separation technique is an excellent approach to repairing complex incisional hernia with excellent results (<5% recurrence rate). Abdominal reconstruction is feasible in district general hospital settings.

581. SURGICAL TREATMENT OF ACUTE SYMPTOMATIC POST-ESOPHAGECTOMY DIAPHRAGMATIC HERNIA

Abstract Background Post esophagectomy diaphragmatic hernia (PEDH) is a rare, often asymptomatic condition, but it can also present as a life-threatening complication leading to emergency treatment. Acute onset of symptoms such as epigastric pain, shortness of breath and evidence of serious complications like strangulation, necrosis or perforation of the herniated organs represent an indication for emergency surgery. The aim of the present study is to report the experience of a tertiary care center for esophageal disease and to describe the clinical and surgical management of acute-onset PEDH treated in an emergency setting. Methods A retrospective analysis of a prospectively collected database of esophagectomies for cancer (hybrid, open, transhiatal or minimally invasive) performed at our Institution between January 2013 to June 2022 was performed. Early PEDH was defined as onset within 90 days from surgery. All patients with acute presentation of volvulus, ischemia, respiratory dysfunction or perforation were treated surgically by two expert surgeons. Results Among 357 patients, 10 had an urgent PEDH requiring surgery within 24 hours after onset of symptoms. Early PEDH was diagnosed in 5 patients (median time 4 days) and 3 of them had a concomitant diagnosis of anastomotic leak. Late hernia was treated at median time of 249 days. Organ resection was performed in 4 patients. Surgical access was laparoscopy in 8 patients, open and thoracotomy in 2. Cruroplasty was performed in 8 cases. Mortality was 0%. Recurrence was 10%. No preoperative risk factors for PEDH were identified (Table 1). Conclusions Diaphragmatic hernia could be a challenging complication after esophagectomy, that could present either as an early or late complication. Its early recognition is of paramount importance given its association with anastomotic leak or strangulation. Laparoscopic repair should be considered as the approach of choice in high-volume centers and cruroplasty with or without mesh positioning should be evaluated.

Is transvaginal mesh surgery with polytetrafluoroethylene mesh ORIHIME® feasible for anterior pelvic organ prolapse?-Randomized comparative study between ORIHIME® and Polyform™.

Transvaginal mesh surgery for pelvic organ prolapse has been widely performed in Japan, but polypropylene mesh has not been used in Japan since the banon TVM using polypropylene mesh in the United States. Currently, polytetrafluoroethylene mesh ORIHIME® is the only mesh available for TVM in Japan. Although polytetrafluoroethylene is a safe material, its low coefficient of friction and insufficient adhesion to the surrounding tissue make it difficult to maintain the mesh position when it is used in the transvaginal mesh surgery. The aim of this study was to evaluate the feasibility of TVM-A2 using ORIHIME®. One hundred cases of TVM-A2 were included in the study. The patients were randomly assigned to two groups: the ORIHIME® group (Group O) and the PolyformTM group (Group P). With 50 patients in each group, the complications and recurrences up to the fourth year were compared. Surgeries were performed using the TVM-A2 method. Statistical analysis was performed using EZR. There were no significant differences in baseline parameters between the two groups. We observed no perioperative complications, and saw one case of postoperative abscess formation in Group O, which resolved successfully after incision and drainage. The 4-year recurrence rate was significantly higher in Group O. As the recurrence rate was significantly higher in Group O, we conclude that TVM-A2 using ORIHIME® which is the same procedure as TVM-A2 using polypropylene mesh is not feasible in repairing the pelvic organ prolapse.

Crack initiation life of aviation gear pair

Abstract The gear transmission system is an important part of the aero-engine. The most serious fault is tooth root fatigue fracture. This paper mainly discusses the time of fatigue crack initiation stage of aviation gear tooth root position. The crack initiation state can be evaluated by analyzing the root stress. The static contact analysis is solved by using the generated aviation gear pair model. The maximum stress in the bending direction of gear teeth is calculated. The changing pattern of tooth root stress with meshing position is described in detail. According to the multi-axial stress fatigue theory, the surface damage parameters and fatigue life of the gear tooth root position are calculated, and the location of the crack initiation is obtained. Fatigue cracks often appear at half of the gear tooth width and near the tooth root circle.

Lateral incisional hernia. EVEREG registry analysis.

The aim of this study is to analyze the data collected on lateral incisional hernias (LIH) in the National Incisional Hernia Registry (EVEREG) and assess current practices and outcomes in LIH repair. A retrospective cohort study was conducted using LIH data recorded over 10years (2012-2022). Comorbidities, hernia characteristics, short-term complications, and recurrences were studied, along with their association with the type of approach used, either open or laparoscopic, in elective surgery. 1742 LIH cases were studied. According to the EHS classification, these included L1 409 (23.5%), L2 388 (22.3%), L3 565 (32.4%), L4 150 (8.6%) and combined 230 (13.2%). An open approach was performed in 1528 (87.7%) cases and laparoscopic in 214 (12.3%). The median age was 66 ± 12.45years, with a majority of males, 934 (53.6%). The median body mass index was 29 ± 5.18kg/m2. The most observed comorbidity was arterial hypertension (957 patients, 55%). A specialist was present in 638 interventions (56%). The 24-month follow-up was 17.9%, and recurrence in those cases was 27.2%, with a higher incidence when there was no specialist present during the intervention, onlay mesh position, and larger defect size. Surgery for LIH is common, although laparoscopic approach remains infrequent. Furthermore, it is associated with a high percentage of recurrences that increases when there is no specialist in abdominal wall surgery present.

Experimental investigation on the effects of stainless-steel mesh reinforcing layers on low-velocity impact response of hybrid thermoplastic glass fiber composites

This study aims to assess the hybridization effect on the perforation threshold of Low-Velocity Impact (LVI) in thermoplastic glass composite laminates, incorporating layers of resin-impregnated stainless-steel mesh. Reinforcing methodologies such as hybridization are recently being adopted as a practical approach to increasing the energy-absorbing capacity of polymer composites. In the current paper, a multi-step hot press lamination method has been employed to fabricate the hybrid composite laminates strengthened with stainless-steel mesh layers. Several stacking sequences, metal mesh wire sizes, orientation and position relative to the impactor have been examined under various LVI energies. It was revealed that the LVI penetration energy was increased for the thermoplastic-based composite laminates reinforced with stainless-steel mesh layers. Furthermore, the LVI penetration energy threshold was significantly influenced by the metal mesh wire size, orientation and stacking sequence. Finally, the backlight method capability was assessed to detect the after-impact interlaminar damages.

ANALYSIS OF THE MIXED ELASTOHYDRODYNAMIC LUBRICATION CHARACTERISTICS OF DOUBLE CIRCULAR ARC GEARS CONSIDERING MICRO-MORPHOLOGY

Different machining methods result in diverse morphologies on the surface of gears. Under mixed lubrication, the friction and contact behavior of the real morphology interface becomes more complex. This study aims to analyze the influence of different process tooth surface micro-morphologies on the lubrication performance of the meshing area of double circular arc gears. Focusing on elastohydrodynamic lubrication (EHL) characteristics of the double circular arc gears as the research object, the study involved measuring the three-dimensional morphology of the meshing position of the double circular arc gears. Non-Gaussian simulation technology was then used to characterize the micromorphology of the tooth surface resulting from different processes (i.e. hobbing process and skiving process). The tooth surface suction speed was determined based on the meshing characteristics of double circular arc gears. Based on the theory of point contact EHL, Reynolds equation and film thickness equation considering micromorphology were derived, and numerical solutions were obtained using the multi-grid method. A point contact EHL model for double circular arc gears was established considering the micromorphology of tooth surfaces in different processes. Results show that, the oil film pressure is positively correlated with rotational speed and torque. The oil film thickness is positively correlated with rotational speed, and negatively correlated with input torque. The negative of micro-morphology on the tooth surface on the lubrication performance could lead to an increase in pressure fluctuations and the absence of the second pressure peak. The uneven distribution of oil film and the lager roughness value could result in obvious fluctuations. The lubrication performance of the contact area in the gear hobbing process is superior to that in the gear skiving process. This study lays the foundation for further exploring the coupling characteristics between the double circular arc gear transmission system and elastic fluid dynamic lubrication. Keywords: Double circular arc gears, Point contact, Mixed EHL, Lubrication characteristics, Micro- morphology.

A first‐order hyperbolic arbitrary Lagrangian Eulerian conservation formulation for non‐linear solid dynamics

SummaryThe paper introduces a computational framework using a novel Arbitrary Lagrangian Eulerian (ALE) formalism in the form of a system of first‐order conservation laws. In addition to the usual material and spatial configurations, an additional referential (intrinsic) configuration is introduced in order to disassociate material particles from mesh positions. Using isothermal hyperelasticity as a starting point, mass, linear momentum and total energy conservation equations are written and solved with respect to the reference configuration. In addition, with the purpose of guaranteeing equal order of convergence of strains/stresses and velocities/displacements, the computation of the standard deformation gradient tensor (measured from material to spatial configuration) is obtained via its multiplicative decomposition into two auxiliary deformation gradient tensors, both computed via additional first‐order conservation laws. Crucially, the new ALE conservative formulation will be shown to degenerate elegantly into alternative mixed systems of conservation laws such as Total Lagrangian, Eulerian and Updated Reference Lagrangian. Hyperbolicity of the system of conservation laws will be shown and the accurate wave speed bounds will be presented, the latter critical to ensure stability of explicit time integrators. For spatial discretisation, a vertex‐based Finite Volume method is employed and suitably adapted. To guarantee stability from both the continuum and the semi‐discretisation standpoints, an appropriate numerical interface flux (by means of the Rankine–Hugoniot jump conditions) is carefully designed and presented. Stability is demonstrated via the use of the time variation of the Hamiltonian of the system, seeking to ensure the positive production of numerical entropy. A range of three dimensional benchmark problems will be presented in order to demonstrate the robustness and reliability of the framework. Examples will be restricted to the case of isothermal reversible elasticity to demonstrate the potential of the new formulation.

Presurgical Virtual Planning and Intraoperative Navigation with 3D-Preformed Mesh: A New Protocol for Primary Orbital Fracture Reconstruction.

This pilot study aims to evaluate the feasibility and effectiveness of computer-assisted surgery protocol with 3D-preformed orbital titanium mesh (3D-POTM), using presurgical virtual planning and intraoperative navigation in primary inferomedial orbital fracture reconstruction. Between March 2021 and March 2023, perioperative data of patients undergoing surgery for unilateral inferomedial orbital fracture treated with 3D-POTM were analyzed. Presurgical virtual planning with a Standard Triangle Language file of preformed mesh was conducted using the mirrored unaffected contralateral side as a reference, and intraoperative navigation was used. The reconstruction accuracy was determined by: correspondence between postoperative reconstruction mesh position with presurgical virtual planning and difference among the reconstructed and the unaffected orbital volume. Pre- and postoperative diplopia and enophthalmos were assessed. Twenty-six patients were included. Isolated orbital floor fracture was reported in 14 (53.8%) patients, meanwhile medial wall and floor one in 12 (46.1%) cases. The mean difference between final plate position and ideal digital plan was 0.692 mm (95% CI: 0.601-0.783). The mean volume difference between reconstructed and unaffected orbit was 1.02 mL (95% CI: 0.451-1.589). Preoperative diplopia was settled out in all cases and enophthalmos in 19 (76.2%) of 21 patients. The proposed protocol is an adaptable and reliable workflow for the early treatment of inferomedial orbital fractures. It enables precise preoperative planning and intraoperative procedures, mitigating pitfalls and complications, and delivering excellent reconstruction, all while maintaining reasonable costs and commitment times.

Thermal performance of a large-diameter thin flattened heat pipe with novel composite wick structure

Flattening large-diameter cylindrical heat pipes to fabricate thin heat pipes can significantly improve their heat transfer performance in theory, but their appropriate wick structures and thermal performance are still unclear. In this work, a novel composite wick structure sintered from spiral woven mesh and orthogonal woven mesh was developed for large-diameter thin flattened heat pipes. Their diameter and thickness were 8 and 1.0 mm, respectively. Seven types of wick structures for the experimental heat pipes were designed to investigate the effects of the length and position of the orthogonal woven mesh on the thermal performance. The results indicated that based on the spiral woven mesh, sintering the orthogonal woven mesh in the evaporator and adiabatic sections of the heat pipe can significantly improve the thermal performance. Compared with the single spiral woven mesh wick, the maximum heat transport capacity of the experimental heat pipe with optimal composite wick increased by 41.67%, and the evaporation and total thermal resistances decreased by 68.41% and 61.49%, respectively. This study provided very useful guidance for improving the thermal performance of the large-diameter thin flattened heat pipes for cooling laptops.

Reinforced tissue matrix to strengthen the abdominal wall following reversal of temporary ostomies or to treat incisional hernias.

Abdominal wall deficiencies or weakness are a common complication of temporary ostomies, and incisional hernias frequently develop after colostomy or ileostomy takedown. The use of synthetic meshes to reinforce the abdominal wall has reduced hernia occurrence. Biologic meshes have also been used to enhance healing, particularly in contaminated conditions. Reinforced tissue matrices (RTMs), which include a biologic scaffold of native extracellular matrix and a synthetic component for added strength/durability, are designed to take advantage of aspects of both synthetic and biologic materials. To date, RTMs have not been reported to reinforce the abdominal wall following stoma reversal. To evaluate the effectiveness of using an RTM to reinforce the abdominal wall at stoma takedown sites. Twenty-eight patients were selected with a parastomal and/or incisional hernia who had received a temporary ileostomy or colostomy for fecal diversion after rectal cancer treatment or trauma. Following hernia repair and proximal stoma closure, RTM (OviTex® 1S permanent or OviTex® LPR) was placed to reinforce the abdominal wall using a laparoscopic, robotic, or open surgical approach. Post-operative follow-up was performed at 1 month and 1 year. Hernia recurrence was determined by physical examination and, when necessary, via computed tomography scan. Secondary endpoints included length of hospital stay, time to return to work, and hospital readmissions. Evaluated complications of the wound/repair site included presence of surgical site infection, seroma, hematoma, wound dehiscence, or fistula formation. The observational study cohort included 16 male and 12 female patients with average age of 58.5 years ± 16.3 years and average body mass index of 26.2 kg/m2 ± 4.1 kg/m2. Patients presented with a parastomal hernia (75.0%), incisional hernia (14.3%), or combined parastomal/incisional hernia (10.7%). Using a laparoscopic (53.6%), robotic (35.7%), or open (10.7%) technique, RTMs (OviTex® LPR: 82.1%, OviTex® 1S: 17.9%) were placed using sublay (82.1%) or intraperitoneal onlay (IPOM; 17.9%) mesh positioning. At 1-month and 1-year follow-ups, there were no hernia recurrences (0%). Average hospital stays were 2.1 d ± 1.2 d and return to work occurred at 8.3 post-operative days ± 3.0 post-operative days. Three patients (10.7%) were readmitted before the 1-month follow up due to mesh infection and/or gastrointestinal issues. Fistula and mesh infection were observed in two patients each (7.1%), leading to partial mesh removal in one patient (3.6%). There were no complications between 1 month and 1 year (0%). RTMs were used successfully to treat parastomal and incisional hernias at ileostomy reversal, with no hernia recurrences and favorable outcomes after 1-month and 1-year.

Improved analytical model for calculating mesh stiffness and transmission error of helical gears considering root curve: Theoretical analysis and experiments

A modified algorithm is proposed in this study to correct time-varying mesh stiffness (TVMS) and transmission error (TE) in helical gears considering tooth root transition curve. The parametric model of helical gear is established by using the meshing principle of helical gear and hob in order to obtain the accurate tooth root transition curve. Moreover, a TE test rig is set up to compare the theoretical and experimental results. The results of the improved algorithm are very similar to the experimental results compared to the traditional model, and the relative error of TE is also small. In this study, the effect of multi-parameters (e.g. pressure angle, meshing position, transverse contact ratio, and overlap ratio) on TE are investigated by comparing theory with experimental analysis. Through the analysis of parameters, it has been established that an elevation in pressure angle leads to a decrease in TE, followed by an increase. In the event that the meshing position is situated closer to the nodal point, the TE slightly decreases. Moreover, as the transverse contact ratio and overlap ratio increase, the TVMS increases, while the TE decreases. When the overlap ratio approaches an odd multiple of 0.5, the TE displays a significant peak.

Vibration analysis of a double-row planetary gear set considering the sun gear axial position.

Double-row planetary gear set (PGS) is a common form of the PGS, which is relatively more complex than the regular PGSs. It consists of one sun gear, several long planets, several short planets, two ring gears, and one carrier. Due to the significantly wider tooth width of the long planet compared to the sun gear, the axial meshing position between the sun gear and the long planet can be adjusted. The vibrations of PGS should vary with different axial meshing positions. If the axial position of the sun gear is optimized, the vibrations of PGS can be reduced. This work establishes a dynamic model of a double-row PGS. The dynamic model considers the mesh forces of the gear pairs and the supporting forces of the bearing. The effect of the sun gear axial position on the sun gear and ring gear #2 vibrations are investigated. Finally, the recommended axial position for the sun gear is provided.