Mesh Position Research Articles

Teaching the transrectus sheath preperiotneal mesh repair: TREPP in 9 steps

BackgroundThe preperitoneal mesh position seems preferable to reduce the number of patients with postoperative chronic pain after inguinal hernia surgery. The transrectus sheath preperitoneal mesh repair (TREPP) is gaining popularity. Teaching a new technique requires a standardized approach to achieve an optimal learning curve. The aim of this paper was to provide a step-by-step teaching module for hernia surgeons learning the TREPP. MethodsLiterature was critically reviewed and the forthcoming nine surgical steps of the new TREPP technique and its rationale are described in this article. The TREPP hernia repair technique is illustrated with an online education video and three photos of the anatomical landmarks and the proposed mesh position of TREPP. ResultsThe nine steps of TREPP are described extensively and the critical steps are presented in a standardized way for surgical educational purposes. Also the rationale and technical considerations of inguinal hernia experts are presented. DiscussionTREPP may be a promising technique for groin hernia surgery. To date there have been no major complications with the TREPP repair which is currently the subject of a RCT. The learning curve of TREPP is being investigated and teaching of this technique requires standardization for trainee surgeons. ConclusionTREPP potentially merges the advantages of a preperitoneal positioned mesh with an open technique. Initial results are promising and TREPP seems to be applicable in different hospitals in the Netherlands. Since the start of an active teaching program, TREPP has been introduced and accepted well by dedicated hernia surgeons in other hospitals in the Netherlands and Europe.

Virtual stenting workflow with vessel-specific initialization and adaptive expansion for neurovascular stents and flow diverters

Endovascular intervention using traditional neurovascular stents and densely braided flow diverters (FDs) have become the preferred treatment strategies for traditionally challenging intracranial aneurysms. Modeling stent and FD deployment in patient-specific aneurysms and its flow modification results prior to the actual intervention can potentially predict the patient outcome and treatment optimization. We present a clinically focused, streamlined virtual stenting workflow that efficiently simulates stent and FD treatment in patient-specific aneurysms based on expanding a simplex mesh structure. The simplex mesh is generated using an innovative vessel-specific initialization technique, which uses the patient’s parent artery diameter to identify the initial position of the simplex mesh inside the artery. A novel adaptive expansion algorithm enables the acceleration of deployment process by adjusting the expansion forces based on the distance of the simplex mesh from the parent vessel. The virtual stenting workflow was tested by modeling the treatment of two patient-specific aneurysms using the Enterprise stent and the Pipeline Embolization Device (commercial FD). Both devices were deployed in the aneurysm models in a few seconds. Computational fluid dynamics analyses of pre- and post-treatment aneurysmal hemodynamics show flow reduction in the aneurysmal sac in treated aneurysms, with the FD diverting more flow than the Enterprise stent. The test results show that this workflow can rapidly simulate clinical deployment of stents and FDs, hence paving the way for its future clinical implementation.

Analysis of bulk temperature field and flash temperature for locomotive traction gear

Sliding velocity variation for gear meshing surface was researched based on theories of gear tribology, heat transfer and Hertz contact, and a model of contact stress considering friction force was derived. The model design process culminated in a comparison of theoretical values and simulated values. Heat flux of friction for different meshing positions and the convective heat transfer coefficient at gear tooth surface and tooth face were initially calculated accurately. The finite element method was then adopted to establish the gear bulk temperature field model and, after the steady state temperature field of the locomotive traction gear was obtained, the distribution law of the steady-state temperature for the gear teeth was analyzed. Transient thermal analysis on the gear was implemented utilizing the steady-state thermal analysis to obtain the transient temperature field of the locomotive traction gear. Applying the Blok flash temperature criterion, theoretical value of the transient temperature rise for the gear tooth surface was calculated. Comparison of the simulation values and the theoretical values for the transient temperature rise indicated that the theoretical values were higher than the simulation values as the Blok flash temperature criterion considers the heat conduction only in the direction vertical to the tooth surface and disregards heat conduction in other directions. The simulation results were then concluded to be superior in practicality and accuracy.

Transabdominal midline reconstruction by minimally invasive surgery: technique and results.

The introduction of the minimally invasive approach changed the way abdominal surgery was carried out. Open suture and mesh reinforcement in ventral hernia repair used to be the surgeon's choice of procedure. Although the laparoscopic approach, with defect bridging and mesh fixation, has been described since 1993, the procedure remains largely unchanged. Evidence shows that defect closure and retro-muscular mesh positioning have the best outcomes and are the best surgical practice. We therefore aimed to develop and demonstrate a procedure which combined the good results of open surgery using the Rives-Stoppa principles, particularly in terms of recurrence, with all the benefits of minimally invasive surgery. Between October 2012 and February 2014, 15 post-bariatric surgery patients underwent laparoscopic midline incisional hernia repair. The peritoneal cavity was accessed through a 5-mm optical view cannula at the superior left quadrant. A suprapubic and two right and left lower quadrant cannulas were inserted for inferior access and dissection. The defect adhesions were released. The whole midline was closed with an endoscopic linear stapler, including the defect, from the lower abdomen, 4 cm below the umbilicus, until the epigastric region, including posterior sheath mechanical suturing and cutting in the same movement. A retrorectus space was created in which a retro-muscular mesh was deployed. Fixation was done using a hernia stapler against the posterior sheath from the peritoneal cavity to the abdominal wall muscles. Selection was based on xifo-umbilical incisional midline hernias post open bariatric surgery. Pregnant women, cancer patients, or patients with clinical contraindications were excluded. The patients mean age was 51.2 years (range 39-67). Four patients were men and eleven women. Two had well-compensated fibromyalgia, four had diabetes, and five had hypertension. The mean BMI was 29.5 kg/m2 (range 23-31.6). Surgery was performed successfully in all cases through four ports; the number of incisional hernias was 3 ± 2, with a mean maximum width of 3.75 cm (range 2.1-9) and maximum length of 14 cm (7.5-20.5). The mean surgical time was 114.3 min (range 85-170), and the median hospital stay was 1.4 days. No intra-operative or immediate post-operative complication or death occurred. One patient had a seroma treated conservatively 1 week after surgery and another had a retro-muscular infection treated with percutaneous drainage. CT-Scans made before and after the procedure, showed total closure of the defect. QOL questionnaire showed satisfaction, acceptance, and no complaints. Although the study involved a small number of patients, it has proved the technique to be feasible, easy to perform, and have the combined benefits of laparoscopic and open surgery. The results, shown by CT-scan, peri-operative, and QOL findings, were good.

Mesh-Airtight-Preperitoneum: a simple method for confirming mesh placement in transabdominal preperitoneal repair of inguinal hernia.

We devised a method for confirming the position of mesh placed during transabdominal preperitoneal repair (TAPP) of an inguinal hernia. The preperitoneum is sufficiently detached, and the mesh is fixed in place as usual. Before completely closing the peritoneum, pressure is applied from outside the body and inside the abdominal cavity to remove as much air as possible from the detached preperitoneum; the peritoneum is then sutured using a V-Loc(TM) closure device so that it does not constrict. By releasing the pressure all at once, the airtightness of the preperitoneum is maintained, and the position of the mesh can be observed through the translucent peritoneum. This method, called Mesh-Airtight-Preperitoneum (MAPP), could become widely used as a simple technique for confirming mesh position in TAPP. J. Med. Invest. 63: 270-273, August, 2016.

はすば歯車のトロコイド干渉が歯面強度に及ぼす影響（歯すじ誤差, クラウニング及び歯先修整の影響）

It is of practical importance to accurately evaluate the influence of tooth surface deviation and modification on the tooth surface strength of transmission gears. In this study, gear surface fatigue endurance tests were carried out with pairs of helical gears having various helix deviation, crowning and tip relief. The results showed that some damages on the tooth surface occurred unexpectedly earlier under certain conditions of these tooth flanks than the fatigue life predicted with a conventional design method based on Herzian pressure on the tooth surface. After observations of the tooth surfaces, it was found that the damages were caused by trochoidal interference, and the influence of the trochoidal interference on the occurrence of the damage was different in the meshing position, namely, the beginning of meshing and the end of meshing. The trochoidal interference in the beginning of meshing was much injurious to the occurrence of the damage. The tooth surface strength of transmission gears needs to be evaluated taking into consideration the occurrence of the damage caused by the trochoidal interference, because the conventional design method of tooth surface strength has a risk to overestimate the tooth surface strength. Therefore, the author discusses a new method combining the tooth surface temperature with the Herzian pressure to predict the occurrence of the damage caused by the trochoidal interference for a practical gear design.

Parametric studies of lubrication performance of a helical gear pair with non-Newtonian fluids

In this paper, Thermal elastohydrodynamic lubrication (TEHL) model of a helical gear pair is proposed to study contact performance during the whole meshing period. Effects of working conditions and design parameters on lubrication performance, i.e. film thickness, pressure, temperature, friction coefficient, etc. are investigated. Influence of thermal effect and non-Newtonian effect are evaluated through a detailed study on three characteristic meshing positions. Results show that, the thermal effects and non-Newtonian fluid both have significant effects on the lubrication performance of the helical gear pair, especially in high speed, heavy load cases. The effects of normal pressure angle, helix angle and module on lubrication performance along the line of action are discussed.

Chronic pain after TEP inguinal hernia repair, does MRI reveal a cause?

Persistent pain is a known side effect after TEP inguinal repair disabling 2-5% of patients. A standardized diagnostic work-up so far is not available. MRI is a diagnostic tool in the work-up of inguinal hernias. In the present study the yield of MRI in evaluating chronic pain after TEP hernia repair is addressed. In our database patients receiving an MRI scan for groin pain lasting more than 3 months after TEP inguinal hernia repair were identified. A checklist with potential pathologic findings was filled out for each groin by two blinded observers. Findings in painful, pain-free and unoperated groins were compared and statistical analysis done based upon their relative incidences. Cohen's kappa coefficients were calculated to determine interobserver agreement. Imaging studies of 53 patients revealed information regarding 106 groins. Fifty-five groins were painful after the initial operation, 12 were pain-free postoperatively and 39 groins were not operated. None of the predefined disorders was observed statistically more often in the patients with painful groins. Only fibrosis appeared more prevalent in patients with chronic pain (P = 0.11). Interobserver agreement was excellent for identifying the mesh (κ = 0.88) and observing bulging or a hernia (κ = 0.74) and was substantial for detecting fibrosis (κ = 0.63). In 40% of the patients, MRI showed a correct mesh position and observed nothing else than minor fibrosis. A wait and see policy resolved complaints in the majority of the patients. In 15 % of the patients, MRI revealed treatable findings explanatory for persisting groin pain. For patients with post-TEP hernia groin pain, MRI is useful to confirm a correct flat mesh position and to identify possible not operation-related causes of groin pain. It is of little help to identify a specific cause of groin repair-related pain.

An embedded approach for immiscible multi‐fluid problems

SummaryAn embedded formulation for the simulation of immiscible multi‐fluid problems is proposed. The method is particularly designed for handling gas–liquid systems. Gas and liquid are modeled using the Eulerian and the Lagrangian formulation, respectively. The Lagrangian domain (liquid) moves on top of the fixed Eulerian mesh. The location of the material interface is exactly defined by the position of the boundary mesh of the Lagrangian domain. The individual fluid problems are solved in a partitioned fashion and are coupled using a Dirichlet–Neumann algorithm. Representation of the pressure discontinuity across the interface does not require any additional techniques being an intrinsic feature of the method. The proposed formulation is validated, and its potential applications are shown. Copyright © 2015 John Wiley & Sons, Ltd.

The influence of mesh misalignment on the dynamic characteristics of helical gears including sliding friction

Due to either elastic deformations or errors in the manufacturing or assembling of gears, shafts, bearings and their housings, it is an inevitable consequence that mesh misalignment between teeth occurs. The change in length of the contact line or the change in load distribution along the length of the contact line induced by mesh misalignment causes changes in the dynamic characteristics of helical gears. There is currently no satisfactory solution for the modeling and calculation of the internal excitation in helical gears with mesh misalignment and sliding friction that would reveal the changes in the dynamic characteristics. In this study, an improved calculation method of friction excitation is proposed based on the time-varying length of the contact line and the time-varying friction coefficient model in helical gears. By considering the change in the mesh position and the change in the length of the contact line or the change of the displacement error along the contact line induced by mesh misalignment, the time-varying sliding friction force and the dynamic mesh force may be obtained. An eight degree-of-freedom analytical helical gear pair model is developed by incorporating the time-varying sliding friction force and dynamic mesh force and considering the mesh misalignment. By assuming a constant mesh stiffness density along the contact line, the rules governing the variation of the dynamic response are obtained using simulations of helical gear pair examples with different friction coefficient models and mesh misalignment. The developed analytical model provides a new method for the study of excitation characteristics in helical gears with mesh misalignment.

Dynamic intermittent strain can rapidly impair ventral hernia repair

Ventral hernia repair fails frequently despite advanced mesh inserting surgery. A model for dynamic intermittent straining (DIS) of ventral hernia repairs was developed. The influence of phospholipids, position, overlap, fixation and tissue quality of various meshes on the durability of hernia repair was studied.DIS comprises the repetition of submaximal impacts delivered via a hydraulically driven plastic containment. Pig tissues simulate a ventral hernia with a standardized 5cm defect. Commercially available meshes strengthened with tacks, glue and sutures were used to bridge this defect in an underlay (IPOM) or sublay (retromuscular) position starting with a 5cm overlap in all directions. We tested 35 different ways of ventral hernia repair with up to 425 submaximal intermittent dynamic impacts until mesh dislocation occurred 10 times or a maximum of 4000 impacts each were withstood.The likelihood of a failing repair was related to the mesh, the lubricants, the position, the overlap, the fixation and the tissue quality. Most meshes dislocated easily and required fixation. One of the meshes tested was stable without fixation with a 5cm overlap and failed after reducing the overlap. Phospholipids exerted a strong influence on the biomaterial tested. The sublay position was about 10% more durable in comparison to the IPOM position. DIS revealed distinct degrees of stability with primarily stable, intermediate and primarily unstable repairs.Based on the DIS results available, the currently used ventral hernia repair options can be classified. In the future, DIS investigations can improve the durability of hernia repair.

Finite element modeling and analysis of planetary gear transmission based on transient meshing properties

Planetary gear trains are widely applied in various transmission units. Whether strengths of all gears are accurately calculated or not can affect reliability of the entire system significantly. Strength calculation method for planetary gear trains usually follows the method for cylindrical gears, in which the worst meshing positions for both contact stress and bending stress cannot be determined precisely, and calculation results tend to be conservative. To overcome these shortcomings, a kinematics analysis for a planetary gear train is firstly performed, in which the influence of relative speed is investigated. Then the finite element strength analysis of a planetary gear train based on its transient meshing properties is carried out in ANSYS. Time–history curves of contact and bending stresses of sun gear, planetary gears and ring gear are respectively obtained. Also the accurate moment and its corresponding position of the maximum stress are precisely determined. Finally, calculation results of finite element method (FEM) and traditional method are compared in order to verify the effectiveness. Simulation and comparison show the stability of the proposed method in this paper. Researches in this paper establish the foundations for fatigue analysis and optimization for a planetary gear train.

The Use of Mesh in Laparoscopic Large Hiatal Hernia Repair: A Survey of European Surgeons.

The aim of this study was to evaluate the current opinion of the individual European surgeons on the use of mesh in large hiatal hernia repair. A Web-based questionnaire was e-mailed to European upper gastrointestinal surgeons identified by the European Association for Endoscopic Surgery. The questionnaire was completed by 165 surgeons. Mesh is routinely applied by 24 respondents (14.5%), selectively by 128 (77.6%), never used by 11 (6.7%), and 2 failed to respond. A polypropylene mesh is used by 81 (52.6%), polyester by 24 (15.6%), PTFE by 12 (7.8%), ePTFE by 49 (31.8%), and biomesh by 43 respondents (27.9%). A vast variation in mesh configuration and positioning is used. Esophageal erosions were encountered by 33 (20.0%) and esophageal stenosis due to dense fibrosis by 34 (20.6%). The results of this survey are very instructive for the individual surgeons throughout the world as these illustrate how colleagues in Europe handle the controversial issues in large hiatal hernia repair.

Risk factors for wound morbidity after open retromuscular (sublay) hernia repair

Retrorectus repairs (RR) of abdominal wall hernias are growing in popularity, yet wound morbidity and predictors in this context have been characterized poorly. Models aimed at predicting wound morbidity typically do not control for technique and/or location of mesh. Our aim was to describe wound morbidity and risk factors specifically in the context of RR hernia repair. Our hypothesis was that the incidence of wound morbidity with mesh sublay would be less than predicted by a model that does not control for mesh position. Consecutive RR hernia repairs with at least a 90-day follow-up were identified in our prospective database and analyzed. The primary outcome measures were the incidence of surgical-site occurrence (SSO) and surgical-site infection (SSI) via modern, standardized definitions. For predictors of SSO, statistical analysis was performed with univariate analysis, χ(2), and logistic regression as well as multivariate regression. A total of 306 patients met the inclusion criteria. Eighty-four SSOs identified in 72 (23.5%) patients included 48 (15.7%) SSIs, 14 (4.6%) instances of wound cellulitis, 12 (3.9%) skin dehiscences, 6 (2.0%) seromas, and 4 (1.3%) hematomas but no instances of mesh excision or fistula formation. Treatment entailed antibiotics alone in 30 patients, 14 bedside drainage procedures, 9 radiographically assisted drainage procedures, and 10 returns to the operating room for debridement. After multivariate analysis, diabetes (OR 2.41), hernia width >20 cm (OR 2.49), and use of biologic mesh (OR 2.93) were statistically associated with the development of a SSO (P < .05). Notably, the mere presence of contamination was not independently associated with wound morbidity (OR 1.83, P = .11). SSO and SSI rates anticipated by a recent risk prediction model were 50-80% and 17-83%, respectively, compared with our actual rates of 20-46% and 7-32%. Based on a large cohort of patients, we identified factors contributing to SSOs specifically for RR hernia repairs. Paradoxically, biologic mesh was an independent predictor of wound morbidity. The development of clinically important mesh complications and rates of wound morbidity less than anticipated by recent predictive models suggest that the retromuscular (sublay) mesh position may be more advantageous.

MP11-17 USING TRANSLABIAL ULTRASOUND AS AN EFFECTIVE TOOL TO VISUALIZE MESH EROSION INTO THE URETHRA AND BLADDER

You have accessJournal of UrologyImaging/Radiology: Uroradiology II1 Apr 2015MP11-17 USING TRANSLABIAL ULTRASOUND AS AN EFFECTIVE TOOL TO VISUALIZE MESH EROSION INTO THE URETHRA AND BLADDER Seth A. Cohen, Karoly A. Viragh, Leah Y. Nakamura, Anne L. Ackerman, Patkawat Ramart, Diana C. Kang, Judy M. Choi, Ja-Hong Kim, Steven S. Raman, and Shlomo Raz Seth A. CohenSeth A. Cohen More articles by this author , Karoly A. ViraghKaroly A. Viragh More articles by this author , Leah Y. NakamuraLeah Y. Nakamura More articles by this author , Anne L. AckermanAnne L. Ackerman More articles by this author , Patkawat RamartPatkawat Ramart More articles by this author , Diana C. KangDiana C. Kang More articles by this author , Judy M. ChoiJudy M. Choi More articles by this author , Ja-Hong KimJa-Hong Kim More articles by this author , Steven S. RamanSteven S. Raman More articles by this author , and Shlomo RazShlomo Raz More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2015.02.398AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Mesh grafts are commonplace for the repair of stress urinary incontinence in women. Women presenting with complications necessitating mesh removal will at times require excision, including a delicate dissection and reconstruction. Preoperative cystoscopy is not always informative in situations of previous partial mesh removal. Ultrasound can yield accurate information for location and position of mesh, which may impact surgical plan and patient expectations. This investigation sought to determine the sensitivity of translabial ultrasound for visualizing mesh erosion of the urethra and/or bladder. METHODS We retrospectively analyzed data from a database of mid-urethral sling patients who underwent translabial ultrasound and mesh removal, identifying those with erosion of the urethra and/or bladder documented intraoperatively. Patients with previous placement of additional mesh-products were excluded from the study. We reviewed the preoperative translabial ultrasound interpretations and calculated the sensitivity for ultrasound to identify mesh erosion. The translabial ultrasounds were performed with a standard technique each time including: images taken in the sagittal, coronal, and axial dimensions, dynamic phase (including cough, strain, Kegel), along with a 3-dimensional reconstruction. We classified the findings into extraluminal (mesh not touching the urethra or bladder), intramural (mesh is in continuity with the wall of the urethra or bladder), or intraluminal (mesh is protruding into the lumen). If mesh was found in the intramural or intraluminal position, it was included in the erosion category. RESULTS 200 patients with suburethral mesh slings underwent translabial ultrasound and mesh excision between 2007 and 2013. 17 were found to have intraoperative erosion of the urethra and/or bladder. Mean age of this cohort at time of mesh removal was 54.67 years old. Sensitivity of translabial ultrasound for erosion was 12/17 (70.5%). Position of mesh at time of ultrasound: 29% were extraluminal or not well visualized, 35% were intramural, and 35% were intraluminal. CONCLUSIONS Translabial ultrasound is effective at visualizing mesh in the urethra and bladder. This study can increase the yield of preoperative counseling for a patient undergoing mesh removal. Subclassification of the mesh position may allow us to more robustly grade the extent of erosion in the future. © 2015 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 193Issue 4SApril 2015Page: e125-e126 Advertisement Copyright & Permissions© 2015 by American Urological Association Education and Research, Inc.MetricsAuthor Information Seth A. Cohen More articles by this author Karoly A. Viragh More articles by this author Leah Y. Nakamura More articles by this author Anne L. Ackerman More articles by this author Patkawat Ramart More articles by this author Diana C. Kang More articles by this author Judy M. Choi More articles by this author Ja-Hong Kim More articles by this author Steven S. Raman More articles by this author Shlomo Raz More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

MP81-08 HOW WELL CAN UROLOGY TRAINEES DETECT SUBURETHRAL MESH USING TRANSLABIAL ULTRASOUND IN COMPARISON TO A RADIOLOGIST?

INTRODUCTION AND OBJECTIVES: Suburethral mesh implantation for stress urinary incontinence can result in erosion, extrusion, infection, pain, and irritative voiding symptoms. Surgical mesh removal can be challenging when operative records are not available, portions of mesh have been removed, mesh position has changed, or it’s not palpated on physical exam. Translabial ultrasonography is a diagnostic tool that can detect synthetic mesh. The purpose of this study was to compare a group of Urology trainees’ and a radiologist’s ability to identify pelvic landmarks, localize and assess completeness of suburethral mesh. METHODS: Eight urology trainees received a 15-minute lecture on anatomical landmarks and techniques of translabial ultrasound as well as instruction on detection of suburethral mesh. The trainees then reviewed 18 different US studies. Trainees were asked a total of 126 questions including identification of anatomical planes, pelvic structures in different planes, mesh presence, disruption of mesh, and its location along the urethra. The overall correct response rate of all questions was compared to a Board-certified radiologist specialized in translabial ultrasound, which served as our control. The radiologist and trainees were blinded to patient history, clinical, and operative findings. RESULTS: Overall, trainees answered correct on average 83.9% (105/126) of all questions compared to the radiologist 94.4% (119/126; p1⁄40.023). Per category the average trainee was able to correctly identify the anatomical plane in 94.4% (17/18) of questions, detect presence or absence of mesh in 95.8% (17/18), determine mesh disruption in 83.3% (15/18), correctly identify pelvic anatomical structures in 83.3% (15/18), and determine location of mesh in correspondence to the urethra in 72.2 % (13/18). CONCLUSIONS: Urology trainees can learn in a reasonable time how to identify anatomical landmarks on translabial ultrasound and consistently detect the presence of suburethral mesh. Translabial ultrasound can be utilized by urologists to aid in preoperative planning for mesh removal or clinical diagnostics for symptomatic mesh.

Three-dimensional analysis of implanted magnetic-resonance-visible meshes.

Our primary objective was to develop relevant algorithms for quantification of mesh position and 3D shape in magnetic resonance (MR) images. In this proof-of-principle study, one patient with severe anterior vaginal wall prolapse was implanted with an MR-visible mesh. High-resolution MR images of the pelvis were acquired 6 weeks and 8 months postsurgery. 3D models were created using semiautomatic segmentation techniques. Conformational changes were recorded quantitatively using part-comparison analysis. An ellipticity measure is proposed to record longitudinal conformational changes in the mesh arms. The surface that is the effective reinforcement provided by the mesh is calculated using a novel methodology. The area of this surface is the effective support area (ESA). MR-visible mesh was clearly outlined in the images, which allowed us to longitudinally quantify mesh configuration between 6 weeks and 8 months after implantation. No significant changes were found in mesh position, effective support area, conformation of the mesh's main body, and arm length during the period of observation. Ellipticity profiles show longitudinal conformational changes in posterior arms. This paper proposes novel methodologies for a systematic 3D assessment of the position and morphology of MR-visible meshes. A novel semiautomatic tool was developed to calculate the effective area of support provided by the mesh, a potentially clinically important parameter.

Contact between Logarithmic Crowned Teeth of Spur Gear Transmission

Gear tooth modification such as lead crowning can reduce stress concentration at the edges of the gear teeth; therefore prolong the fatigue life of gears. A logarithmical lead profile was applied on spur gears and the surface coordinate equation of logarithmic crowned tooth for manufacturing was established. On the basis of the contact mechanics model, the deformation equation of compatibility and load equilibrium equation were solved with an iterative numerical algorithm, and the corresponding programs were developed in Matlab to calculate the distributions of contact stress and von Mises stress field inside the subsurface layer at any meshing position. The numerical results of some typical examples show that the level of stress concentration before modification changes with the engaging locations of the gear teeth, and so does the amount of logarithmic modification along the line of contact, which can completely eliminate the edge effects of tooth surface at every meshing position during the spur gear transmission process, and thus improves the fatigue resistance of gear teeth surfaces.

A fully implicit combined field scheme for freely vibrating square cylinders with sharp and rounded corners

We present a fully implicit combined field scheme based on Petrov–Galerkin formulation for fluid–body interaction problems. The motion of the fluid domain is accounted by an arbitrary Lagrangian–Eulerian (ALE) strategy. The combined field scheme is more efficient than conventional monolithic schemes as it decouples the computation of ALE mesh position from the fluid–body variables. The effect of corner rounding is studied in two-dimensions for stationary as well as freely vibrating square cylinders. The cylinder shapes considered are: square with sharp corners, circle and four intermediate rounded squares generated by varying a single rounding parameter. Rounding of the corners delays the primary separation originating from the cylinder base. The secondary separation, seen solely for the basic square along its lateral edges, initiates at a Reynolds number, Re between 95 and 100. Imposition of blockage lowers the critical Re marking the onset of secondary separation. For free vibrations without damping, Re range is 100–200 and mass ratio, m∗ of each cylinder is 10. The rounded cylinders undergo vortex-induced motion alone whereas motion of the basic square is vortex-induced at low Re and galloping at high Re. The flow is periodic for vortex-induced motion and quasi-periodic for galloping. The lower branch and desynchronization characterize the response of rounded cylinders. For the square cylinder, the components of response are the lower branch, desynchronization and galloping. Removal of the sharp corners of square cylinder drastically alters the flow and vibration characteristics.

Radiofrequency-shielding Effect of a Titanium Mesh Implanted for Cranioplasty.

After cranioplasty with a titanium mesh, radiofrequency (RF)-shielding images appear during magnetic resonance (MR) imaging. To clarify their influence, we evaluated the effect of mesh position, phase-encoding direction, and type of coil employed. On a 1.5-tesla MR imager, we placed a titanium mesh board (100 × 100 × 0.8 mm) on the surface of a cubic phantom to mimic a human brain and used a quadrature coil and an 8-channel neurovascular coil to measure nonuniformity, signal decay ratio, and the B1 map. Nonuniformity was 6.7 times higher at the quadrature head coil and 1.6 times higher at the neurovascular coil when the mesh was on the phantom's right side or anterior to it than when it was on its superior end or absent. The profile of the signal decay ratio increased by 1.9% mm(-1) from 0 to 40 mm from the mesh side to the base value at the quadrature head coil when the mesh was on the phantom's right side and 0.9% mm(-1) from 0 to 80 mm at the neurovascular coil when the mesh was on the phantom's right side or anterior to it. The quadrature head coil showed greater incline of the profile when the mesh was on the right in coronal and axial views and no notable change in the profile in coronal and sagittal views when the mesh was on the superior end. In the B1 map, the flip angle was lower when the mesh was nearer. The response to the RF-shielding effect from a titanium mesh depends on the location of the mesh and the RF coil used but not on the phase-encoding direction.