Mesh Locations Research Articles

Observational study of complex abdominal wall reconstruction using porcine dermal matrix: How have outcomes changed over 14 years?

BackgroundOur center has adopted many evidence-based practices to improve outcomes for complex abdominal wall reconstruction with porcine dermal matrix. This study analyzed outcomes over time using porcine dermal matrix in complex abdominal wall reconstruction. MethodsProspective, tertiary hernia center data was examined for patients undergoing complex abdominal wall reconstruction with porcine dermal matrix. Early (2008–2014) and Recent (2015–2021) cohorts were defined by dividing the study interval in half. Multivariable analyses of wound complications and recurrence were performed. ResultsComparing 117 Early vs 245 Recent patients, both groups had high rates of previously repaired hernias (76.1% vs 67.4%; P = .110), Centers for Disease Control and Prevention class 3 or 4 wounds (76.0% vs 66.6%; P = .002), and very large hernia defects (320 ± 317 vs 282 ± 164 cm2; P = .640). Recent patients had higher rates of preoperative botulinum injection (0% vs 21.2%; P < .001), posterior component separation (15.4% vs 35.5%; P < .001), and delayed primary closure (23.1% vs 38.8%; P < .001), but lower rates of concurrent panniculectomy (32.3% vs 27.8%; P = .027) and similar anterior component separation (29.1% vs 18.2%; P = .060). Most mesh was placed preperitoneal (74.4% vs 93.3%; P < .001). Recent patients had less inlay (9.4% vs 2.1%; P < .01) and other mesh locations as fascial closure rate increased (88.0% vs 95.5%; P < .001). Over time, there was a decrease in wound complications (42.1% vs 14.3%; P < .001), length of stay (median [interquartile range]:8 [6–13] vs 7 [6–9]; P = .003), and 30-day readmissions (32.7% vs 10.3%; P < .001). Hernia recurrence decreased (10.3% vs 3.7%; P = .016) with mean follow-up of 2.8 ± 3.2 and 1.7 ± 1.7 years, respectively.Respective multivariable models(odds ratio, 95% confidence interval) demonstrated an increased risk of wound complications with diabetes (2.65, 1.16–5.98; P = .020), panniculectomy (2.63, 1.21–5.73; P = .014), and anterior component separation (5.1, 1.98–12.9; P < .001), with recurrence risk increased by wound complication (3.8, 1.4-2-7.62; P = .032). ConclusionPorcine dermal matrix in complex abdominal wall reconstruction performs well with low recurrence rates. Internal assessment and implementation of evidence-based practices improved outcomes such as length of stay, wound complications, and recurrence rate.

Prophylactic Mesh Reinforcement for Prevention of Midline Incisional Hernias: A Publication Bias Adjusted Meta-analysis.

To systematically review the published literature on the use of prophylactic mesh reinforcement of midline laparotomy closures for prevention of VIH. VIH are common complications of abdominal surgery. Prophylactic mesh has been proposed as an adjunct to prevent their occurrence. PubMed, Embase, Scopus, and Cochrane were reviewed for RCTs that compared prophylactic mesh reinforcement versus conventional suture closure of midline abdominal surgery. Primary outcome was the incidence of VIH at postoperative follow-up ≥24 months. Secondary outcomes included surgical site infection and surgical site occurrence (SSO). Pooled risk ratios were obtained through random effect meta-analyses and adjusted for publication bias. Network meta-analyses were performed to compare mesh types and locations. Of 1969 screened articles, 12 RCTs were included. On meta-analysis there was a lower incidence of VIH with prophylactic mesh [11.1% vs 21.3%, Relative risk (RR) = 0.32; 95% confidence interval (CI) = 0.19-0.55, P < 0.001), however, publication bias was highly likely. When adjusted for this bias, prophylactic mesh had a more conservative effect (RR = 0.52; 95% CI = 0.39-0.70). There was no difference in risk of surgical site infection (9.1% vs 8.9%, RR = 1.08, 95% CI = 0.82-1.43; P = 0.118), however, prophylactic mesh increased the risk of SSO (14.2% vs 8.9%, RR = 1.57, 95% CI = 1.19-2.05; P < 0.001). Current RCTs suggest that in mid-term follow-up prophylactic mesh prevents VIH with increased risk for SSO. There is limited long-term data and substantial publication bias.

Polypropylene Mesh Complications in the Sublay Position After Abdominally Based Breast Reconstruction: Les complications des treillis de polypropylène en sous-couche après une reconstruction mammaire par voie abdominale

Introduction: Abdominal wall morbidity after microsurgical breast reconstruction is an important consideration for patients and surgeons. Previous studies are limited by multiple mesh locations or types. In this study, we evaluate specifically subfascial polypropylene mesh placement to determine a more definitive complication rate and basis for objective comparison. Methods: A retrospective review was performed for patients undergoing microsurgical breast reconstruction at our institution by 3 surgeons from 2015 to 2018. All patients with sublay placement of polypropylene mesh were included. Patient demographics, medical comorbidities, type of reconstruction, and postoperative abdominal wall complications were recorded. Results: A total of 114 flaps were performed on 81 patients who met the inclusion criteria. Of these, 48 were deep inferior epigastric artery (DIEP) flaps (42%), 43 were MS-2 TRAM flaps (37.8%), 20 were muscle sparing (MS-1) transverse rectus abdominus muscle (TRAM) flaps (17.5%), and 3 were free TRAM flaps (2.6%). Average follow-up was 392 days (range: 29-1191). Average body mass index was 30.7. No patients developed hernias. Two patients (2.5%) complained of post-operative bulges, neither of which required operative treatment. Two patients experienced superficial abdominal wall infection, one of which required admission and intravenous antibiotics. Ten patients (12.3%) had abdominal incision dehiscence, 3 of which required operative intervention. There were no cases of mesh exposure, contamination, or removal. Conclusion: Polypropylene mesh is safe and effective, with subfascial placement resulting in low morbidity and low rates of bulge/hernia formation after microsurgical breast reconstruction. Consideration should be given to using polypropylene mesh for fascial repairs after microsurgical breast reconstruction, particularly in high-risk populations.

Effect of velocity shear on the performance and structural response of a small-scale horizontal axis tidal turbine

The focus of this paper is to investigate the effect of velocity shear on the performance and structural response of a turbine using ANSYS Workbench. CFD simulations are performed for a small-scale threebladed horizontal axis turbine in a uniform and velocity shear environment. The turbine diameter is 0.28 m and operates in a free stream velocity of 0.5 m/s. The steady state and transient CFD analysis results are validated with published data. Results for the turbine performance coefficients from the steady state and transient CFD analysis differed by 3% and 1.2%, respectively, from the previously published data. One-way FSI analysis is carried out in ANSYS Workbench by connecting ANSYS CFX and ANSYS static structural analysis systems to evaluate the effect of velocity shear on blades’ equivalent stress and deformation. For the FSI analysis, the steady state solution data are transferred and mapped at FEA mesh locations using ANSYS CFD-Post mapping. Results from the FSI analysis show that deformation of the turbine blades increases in a velocity shear environment compared to uniform flow.

Skeletal mesh animation driven by few positional constraints

AbstractIn this paper, we propose a whole animation pipeline for data‐driven character animation. Considering that the traditional animation pipeline, including skeleton reconstruction from markers, rigging, and retargeting, is subject to potential loss of information and precision, our objective is to control in real time articulated meshes from a low number of positional constraints. Our method is based on an efficient deformation technique that integrates into a volumetric control structure the high‐resolution mesh, the skeleton, and relevant marker locations. An iterative optimization method, which preserves both geometric characteristics, segment lengths and joint limits, is applied to this structure. We show the ability of our system to interactively animate and deform high‐resolution models from few positional constraints while keeping all the details of the movement.

Intensity control of individual DBD plasma filament. II. Fundamental physical mechanism

Filamentary volume dielectric barrier discharge (DBD) produces patterned plasma structures that are currently being explored for reconfigurable metamaterial applications. Previous work has demonstrated control of the presence and intensity of a single DBD plasma filament (within an array of filaments) by biasing a low voltage needle electrode. The results were attributed to redistributed charge inside the DBD due to the modified electric field created by the needle electrode. In the present work, results from a 3D electrodynamic field simulation bolster this argument. Results show that increasing needle bias voltage causes changes in the transverse electric field structure, resulting in redistribution and build-up of surface charge at the needle location. This reduces the needle plasma filament intensity and eventually extinguishes the filament. Specifically, extinguishment of the filament corresponds with the following transitions in the field profile: (1) the applied longitudinal electric field profile along the needle lies below that of the adjacent mesh filament; (2) the surface charge on the dielectric at the needle and adjacent mesh locations is equal; and (3) the transverse electric field reverses direction and forces charge toward the needle location. The calculated surface charge on the dielectric barrier agrees with experimentally measured filament light intensity to within 8%, in agreement with theoretical predictions. Analysis of the data and trends suggests a method for predicting filament pattern formation and reducing the necessary voltage bias.

A Proximal Straining Mesh Location Is Associated With De Novo Stress Urinary Incontinence After Transobturator Mesh Procedures.

The purpose of this study was to explore the association between mesh location and de novo stress urinary incontinence (SUI) after transvaginal mesh procedures. We retrospectively analyzed a database of women who had received transvaginal mesh procedures for stage III or greater cystocele according to the Pelvic Organ Prolapse Quantification system. Only data for women who neither reported SUI preoperatively nor had received concomitant anti-incontinence surgery were included for analyses. The mesh location was investigated by sonography via the percentage of the urethra covered by mesh, defined as the number calculated by dividing the portion of the urethral length covered by mesh (the distance from the bladder neck to the point of the urethra, which was indicated by an imaginary line at the level of the lower [caudal] mesh end and perpendicular to the urethra) by the total urethral length (the distance from the bladder neck to the external urethral meatus) in the sagittal plane. The resting, straining, coughing, and squeezing mesh locations of women who did (n = 29) and did not (n = 54) report SUI at the 12-month follow-up were compared. At the 12-month follow-up, women who reported SUI had a significantly smaller straining percentage of the urethra covered by mesh (mean ± SD, 28.5% ± 9.6%) compared with continent women (35.2% ± 15.8%), indicating a more proximal straining mesh location. Sonography is useful in investigating the location of the transvaginal mesh. De novo SUI after transvaginal mesh procedures is associated with a more proximal straining mesh location.

Convergence Analysis of the mimetic Finite Difference Method for Elliptic Problems with Staggered Discretizations of Diffusion Coefficients

We study the convergence of the new family of mimetic finite difference schemes for linear diffusion problems recently proposed in [K. Lipnikov, G. Manzini, J. D. Moulton, and M. Shashkov, J. Comput. Phys, 305 (2016), pp. 111--126]. In contrast to the conventional approach, the diffusion coefficient enters both the primary mimetic operator, i.e., the discrete divergence, and the inner product in the space of gradients. The diffusion coefficient is therefore evaluated on different mesh locations, i.e., inside mesh cells and on mesh faces. Such a staggered discretization may provide the flexibility necessary for future development of efficient numerical schemes for nonlinear problems, especially for problems with degenerate coefficients. These new mimetic schemes preserve symmetry and positive-definiteness of the continuum problem, which allow us to use efficient algebraic solvers such as the preconditioned conjugate gradient method. We show that these schemes are inf-sup stable and establish a priori error...

Using field inversion to quantify functional errors in turbulence closures

A data–informed approach is presented with the objective of quantifying errors and uncertainties in the functional forms of turbulence closure models. The approach creates modeling information from higher-fidelity simulations and experimental data. Specifically, a Bayesian formalism is adopted to infer discrepancies in the source terms of transport equations. A key enabling idea is the transformation of the functional inversion procedure (which is inherently infinite-dimensional) into a finite-dimensional problem in which the distribution of the unknown function is estimated at discrete mesh locations in the computational domain. This allows for the use of an efficient adjoint-driven inversion procedure. The output of the inversion is a full-field of discrepancy that provides hitherto inaccessible modeling information. The utility of the approach is demonstrated by applying it to a number of problems including channel flow, shock-boundary layer interactions, and flows with curvature and separation. In all these cases, the posterior model correlates well with the data. Furthermore, it is shown that even if limited data (such as surface pressures) are used, the accuracy of the inferred solution is improved over the entire computational domain. The results suggest that, by directly addressing the connection between physical data and model discrepancies, the field inversion approach materially enhances the value of computational and experimental data for model improvement. The resulting information can be used by the modeler as a guiding tool to design more accurate model forms, or serve as input to machine learning algorithms to directly replace deficient modeling terms.

Mesh Location in Open Ventral Hernia Repair: A Systematic Review and Network Meta-analysis.

There is no consensus on the ideal location for mesh placement in open ventral hernia repair (OVHR). We aim to identify the mesh location associated with the lowest rate of recurrence following OVHR using a systematic review and meta-analysis. A search was performed for studies comparing at least two of four locations for mesh placement during OVHR (onlay, inlay, sublay, and underlay). Outcomes assessed were hernia recurrence and surgical site infection (SSI). Pairwise meta-analysis was performed to compare all direct treatment of mesh locations. A multiple treatment meta-analysis was performed to compare all mesh locations in the Bayesian framework. Sensitivity analyses were planned for the following: studies with a low risk of bias, incisional hernias, by hernia size, and by mesh type (synthetic or biologic). Twenty-one studies were identified (n = 5,891). Sublay placement of mesh was associated with the lowest risk for recurrence [OR 0.218 (95% CI 0.06-0.47)] and was the best of the four treatment modalities assessed [Prob (best) = 94.2%]. Sublay was also associated with the lowest risk for SSI [OR 0.449 (95% CI 0.12-1.16)] and was the best of the 4 treatment modalities assessed [Prob (best) = 77.3%]. When only assessing studies at low risk of bias, of incisional hernias, and using synthetic mesh, the probability that sublay had the lowest rate of recurrence and SSI was high. Sublay mesh location has lower complication rates than other mesh locations. While additional randomized controlled trials are needed to validate these findings, this network meta-analysis suggests the probability of sublay being the best location for mesh placement is high.

Standardised unfold map of the left atrium: regional definition for multimodal image analysis

Background Atrial fibrillation (AF) can be treated by catheter ablation to electrically isolate the pulmonary veins (PVs) from the left atrial (LA) body. To guide the procedure, an anatomical representation of the LA is usually visualised by an electroanatomical mapping system. As a follow-up, late gadolinium enhancement MR sequences can be obtained to assess the extent of ablation delivery. However, visual analysis and quantification is timeconsuming with poor reproducibility. Unfold maps offer advantages over 3D surfaces for visualisation of imaging information while providing a common reference space for inter-subject comparison. We have developed a method to automatically map multimodal information onto a standardised unfold map (SUM) of the LA. We use the SUMs to compare force and scar information from the same patient. Methods Ten patients underwent ablation procedure for AF. The intra-procedure anatomical surfaces containing force measurements from the CARTO system were exported. Six months after the procedure, the patients underwent a cardiac MRI scan in order to quantify the extent of postablation injury. The scan included 3D whole heart (3DWH) and 3D late enhancement (3DLE) sequences. The LA was segmented from the 3DWH datasets using a multi-atlas fusion approach. The segmentations were manually corrected when necessary to generate a high fidelity result. The LA segmentation initialised a 3DLE scar extraction algorithm based on maximum intensity projection. We extracted a surface mesh from the LA segmentation and mapped the 3DLE intensity values to corresponding surface mesh locations. To standardise the resulting surfaces, we automatically clipped the mitral plane and the PVs 10mm distal to the ostia. To bring each mesh to the average mesh space, we computed a landmark based affine transformation using the PV end points and the mitral centroid. We applied this transformation to each patient’ sm esh and performed surface matching via currents. After surface registration, we projected the scar and force values of each patient onto the average mesh. The average mesh was unfolded using a fast surface parameterisation technique developed for texture mapping. The mapping method enables the constraint of the parameterisation to fit a predefined template.

Design of Node Locations for Indoor Wireless Mesh Network

In literatures, the performance of Wireless Mesh Network (WMN) has been analyzed by assuming the same quality for each hop. However, this assumption is hardly true in practice due to the physical obstructions of wireless link, especially for an indoor environment. Therefore, this paper revisits the analysis of WMN performance by taking the effect of physical obstructions into account instead of assuming an equally deterministic property for each hop. These obstructions cause the degradation of signal strength which relatively decrease the success rate oftransmission between hop to hop. This paper examines these physical concerns through the measured results and then the design of node locations can be achieved. Moreover, it is well known that the analysis of throughput in WMN has indicated the impact of near-far mesh locations. However, these examinations have neglected the quantity of user accessibility. Therefore, this paper presents the effect of user accessibility in terms of traffic intensity on WMN throughput. The simulations provide a substantial remark to realize the effect of physical obstruction and traffic intensity on designing WMN node locations.

Fourth order compact implicit method for the Maxwell equations with discontinuous coefficients

We consider fourth order accurate compact schemes for numerical solutions to the Maxwell equations. The same mesh stencil is used as in the standard Yee scheme. In particular extra information over a wider stencil is not required. This has several advantages. First, it is relatively easy to modify an existing code based on the Yee algorithm to make it fourth order accurate. Second, a staggered mesh, without additional mesh locations, makes the boundary treatment easier since some of the quantities are located inside the domain rather than on the boundary. Also, a staggered grid system gives a lower error than a similar non-staggered system. The extension to dielectric materials is presented. This uses a compact implicit smoothing operator to redefine the piecewise constant dielectric coefficients.

Catch characteristics of commercial gill‐nets in a nearshore fishery in central New Zealand

Commercial gill‐nets of three mesh sizes (3.5”, 4.5”, 5.5” diagonal measure) were joined into a single net 300 m long and 5 m high, and set at three localities (New Plymouth, Palliser Bay, Bay of Plenty) in the lower North Island, New Zealand. The nets were bottom‐set in shallow (9–26 m depth) and deep (35–100 m depth) water, mostly for 16 h, to test the effects of mesh size on the species composition and sizes of fish caught. In 17 sets, 3284 fish of 55 species were caught. Across all species, larger fish were caught in deep water and at the two largest mesh sizes. The species caught and proportional composition of the catches varied both between locations and mesh sizes. Overall, there were important differences between mesh sizes, depths, and locations in the species composition and size distribution of gill‐net catches, as well as a wide range of species and sizes caught within single sets. Indications are that effective targeting of individual species at the nearshore‐pelagic interface may be confounded by bycatch.