scholarly journals Deformation of Transvaginal Mesh in Response to Multiaxial Loading

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
William R. Barone ◽  
Katrina M. Knight ◽  
Pamela A. Moalli ◽  
Steven D. Abramowitch
Keyword(s):  
Computational Model ◽  
Complex Loading ◽  
Pelvic Organ ◽  
Synthetic Mesh ◽  
Transvaginal Mesh ◽  
Complication Rates ◽  
Multiaxial Loading ◽  
Loading Conditions ◽  
In Vivo Loading

Synthetic mesh for pelvic organ prolapse (POP) repair is associated with high complication rates. While current devices incorporate large pores (>1 mm), recent studies have shown that uniaxial loading of mesh reduces pore size, raising the risk for complications. However, it is difficult to translate uniaxial results to transvaginal meshes, as in vivo loading is multidirectional. Thus, the aim of this study was to (1) experimentally characterize deformation of pore diameters in a transvaginal mesh in response to clinically relevant multidirectional loading and (2) develop a computational model to simulate mesh behavior in response to in vivo loading conditions. Tension (2.5 N) was applied to each of mesh arm to simulate surgical implantation. Two loading conditions were assessed where the angle of the applied tension was altered and image analysis was used to quantify changes in pore dimensions. A computational model was developed and used to simulate pore behavior in response to these same loading conditions and the results were compared to experimental findings. For both conditions, between 26.4% and 56.6% of all pores were found to have diameters <1 mm. Significant reductions in pore diameter were noted in the inferior arms and between the two superior arms. The computational model identified the same regions, though the model generally underestimated pore deformation. This study demonstrates that multiaxial loading applied clinically has the potential to locally reduce porosity in transvaginal mesh, increasing the risk for complications. Computational simulations show potential of predicting this behavior for more complex loading conditions.

The Effect of Muscle Loading on Internal Mechanical Parameters of the Lumbar Spine: A Finite Element Study

2011 ◽  
Author(s):  
Benjamin C. Gadomski ◽  
John Rasmussen ◽  
Christian M. Puttlitz
Keyword(s):  
Annulus Fibrosus ◽  
Critical Role ◽  
Complex Loading ◽  
Tissue Level ◽  
Mechanical Parameters ◽  
Loading Conditions ◽  
Additional Stability ◽  
Muscle Loading ◽  
Pure Moment

The human spine experiences complex loading in vivo; however, simplifications to these loading conditions are commonly made in computational and experimental protocols. Pure moments are often used in cadaveric preparations to replicate in vivo loading conditions, and previous studies have shown this method adequately predicts range of motion behavior (1, 2). It is unclear what effect pure moment loading has on the tissue-level internal mechanical parameters such as stresses in the annulus fibrosus and facet contact parameters. Recent advances in musculoskeletal modeling have elucidated previously unknown quantities of the musculature recruitment patterns such as times, forces, and directions. The advancements are especially relevant in cases of surgical intervention because the spinal musculature has been reported to play a critical role in providing additional stability to the spine when defects such as discectomy and nucleotomy are involved (2). Thus, the aim of the study was to determine the importance of computational loading conditions on the resultant global ranges of motion, as well as the tissue-level predictions of annulus fibrosus stresses, and facet contact pressures, forces, and areas.

scholarly journals Computational simulation of fracture behaviour in auxetic cellular structure by multiaxial loading

2019 ◽  
Vol 300 ◽  
pp. 03001
Author(s):  
Branko Nečemer ◽  
Janez Kramberger ◽  
Nejc Novak ◽  
Srečko Glodež
Keyword(s):  
Computational Model ◽  
Cellular Structure ◽  
Computational Models ◽  
Fracture Behaviour ◽  
Computational Simulation ◽  
Tangential Direction ◽  
Multiaxial Loading ◽  
Loading Conditions ◽  
Normal Contact ◽  
Auxetic Structure

A computational simulation of fracture behaviour in auxetic cellular structure, subjected to multiaxial loading is presented in this paper. A fracture behaviour of the 3D (three-dimensional) chiral auxetic structure under multiaxial loading conditions was studied. The computational models were used to study the geometry effect of the unit cell on the Poisson’s ratio and fracture behaviour of the analysed chiral auxetic structure. A 3D computational model was built using FEM-code LS DYNA. The discrete computational model of chiral auxetic structure was built using beam finite elements. The lattice model of the analysed auxetic structure was positioned between rigid plates and assembled in a way to simulate a hydro-compression loading conditions. Between the contacting surfaces interactions in normal (contact) and tangential direction (friction) with the node-to-surface approach were simulated. A developed computational model offers insight in the fracture behaviour of considered auxetic cellular structure and helps to better understanding their crushing behaviour under impact multiaxial loading.

Characterizing the Ex-Vivo Mechanical Properties and Corresponding In-Vivo Impact of Synthetic Urogynecological Meshes

2011 ◽  
Author(s):  
Andrew J. Feola ◽  
Pamela Moalli ◽  
Suzan Stein ◽  
Zegbeh Jallah ◽  
Jon Shepherd ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Abdominal Wall Hernia ◽  
The United States ◽  
Pelvic Organ ◽  
Synthetic Mesh ◽  
Scientific Data ◽  
Societal Costs ◽  
Large Numbers

Pelvic organ prolapse and urinary incontinence are common conditions in women that significantly diminish quality of life. With roughly 225,000–280,000 women requiring surgery each year in the United States alone, societal costs are over a billion dollars annually (1). While repair with synthetic mesh products have become the surgical treatment of choice, these meshes require very little premarket testing because they are based on previously approved abdominal wall hernia products (510K devices). Thus, there is little scientific data on the efficacy of meshes for gynecological surgery. Moreover, with the recent FDA warning citing large numbers of unreported complications in patients, there is growing concern about the use of gynaecological mesh, especially for transvaginal placement (2). Thus, there is a need to examine the ex-vivo properties of these meshes and relate them to their in-vivo function and outcomes for gynecological applications.

Experimental and Computational Modeling of Joint and Ligament Mechanics

2004 ◽  
Vol 20 (4) ◽  
pp. 450-474 ◽  
Author(s):  
Richard E. Debski ◽  
Shon P. Darcy ◽  
Savio L-Y. Woo
Keyword(s):  
Computational Models ◽  
Soft Tissues ◽  
Experimental Studies ◽  
Complex Loading ◽  
External Loading ◽  
Spring Model ◽  
Loading Conditions ◽  
Rehabilitation Protocols ◽  
Force Moment

Quantitative data on the mechanics of diarthrodial joints and the function of ligaments are needed to better understand injury mechanisms, improve surgical procedures, and develop improved rehabilitation protocols. Therefore, experimental and computational approaches have been developed to determine joint kinematics and the in-situ forces in ligaments and their replacement grafts using human cadaveric knee and shoulder joints. A robotic/universal force-moment sensor testing system is used in our research center for the evaluation of a wide variety of external loading conditions to study the function of ligaments and their replacements; it has the potential to reproduce in-vivo joint motions in a cadaver knee. Two types of computational models have also been developed: a rigid body spring model and a displacement controlled spring model. These computational models are designed to complement and enhance experimental studies so that more complex loading conditions can be examined and the stresses and strains in the soft tissues can be calculated. In the future, this combined approach will improve our understanding of these joints and soft tissues during in-vivo activities and serve as a tool to aid surgical planning and development of rehabilitation protocols.

scholarly journals Efficacy and patient satisfaction of pelvic organ prolapse reduction using transvaginal mesh: A Canadian perspective

2018 ◽  
Vol 12 (10) ◽  
Author(s):  
Mélanie Aubé ◽  
Marilyne Guérin ◽  
Caroline Rhéaume ◽  
Le Mai Tu
Keyword(s):  
Pelvic Organ Prolapse ◽  
Pelvic Organ ◽  
Class Action ◽  
Transvaginal Mesh ◽  
Mesh Exposure ◽  
Complication Rates ◽  
Medical Chart Review ◽  
Repeat Operation ◽  
Canadian Perspective ◽  
Report Data

Introduction: Due to U.S Food and Drud Administration warnings and class-action lawsuits, the use of transvaginal mesh for pelvic organ prolapse surgery is controversial. We report data from two Canadian centres, focusing on recurrence and reoperation rates, complication rates, and patient satisfaction.Methods: A retrospective medical chart review was performed. Patients were also invited to a long-term followup clinic for a complete questionnaire and gynecological exam. Patients unable to present to clinic for followup had the option to answer the questionnaire via telephone.Results: A total of 334 patients were operated between 2000 and 2013. Median followup was 38 months for questionnaire and 36 months for physical exam. Thirty-seven patients (11.1%) required repeat operation, including 17 for recurrent prolapse and 10 for mesh exposure; 98.8% of patients reported feeling subjectively improved by their prolapse surgery.Conclusions: Midterm results are satisfactory and patient subjective satisfaction is high following transvaginal mesh repair of pelvic organ prolapse.

Characterization of Fatigue Crack Propagation Under Complex Biaxial Loading

2016 ◽  
Author(s):  
Rajesh Kumar Neerukatti ◽  
Siddhant Datta ◽  
Aditi Chattopadhyay ◽  
Nagaraja Iyyer ◽  
Nam Phan
Keyword(s):  
Fatigue Crack ◽  
Crack Growth ◽  
Biaxial Loading ◽  
Biaxial Tension ◽  
Fatigue Behavior ◽  
Complex Loading ◽  
Fatigue Tests ◽  
Multiaxial Loading ◽  
Loading Conditions ◽  
Phase Out

Metallic aerospace components are subject to a variety of uniaxial and multiaxial loading conditions and therefore, characterizing and predicting the fatigue crack growth is of paramount importance to the aerospace industry. The fatigue behavior of metallic materials has been researched over the years and well understood under uniaxial loading conditions. However, aerospace structures are often subject to multiaxial loading and there are a very few studies reported on this topic. In this paper, extensive in-plane biaxial tension-tension fatigue tests were performed on an Al7075-T651 cruciform specimen under varying load conditions such as in-phase, out-of-phase and miniTWIST loading. The fatigue life and crack growth rate were evaluated and fractography was performed to understand the microscale crack initiation and growth under these complex loading conditions.

Estimation of In Vivo ACL Force Changes in Response to Increased Weightbearing

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Ali Hosseini ◽  
Thomas J. Gill ◽  
Samuel K. Van de Velde ◽  
Guoan Li
Keyword(s):  
Imaging System ◽  
Cruciate Ligament ◽  
Valuable Insight ◽  
Loading Conditions ◽  
Noninvasive Technique ◽  
Biomechanical Behavior ◽  
In Vivo Loading ◽  
Full Body

Accurate knowledge of in vivo anterior cruciate ligament (ACL) forces is instrumental for understanding normal ACL function and improving surgical ACL reconstruction techniques. The objective of this study was to estimate the change in ACL forces under in vivo loading conditions using a noninvasive technique. A combination of magnetic resonance and dual fluoroscopic imaging system was used to determine ACL in vivo elongation during controlled weightbearing at discrete flexion angles, and a robotic testing system was utilized to determine the ACL force-elongation data in vitro. The in vivo ACL elongation data were mapped to the in vitro ACL force-elongation curve to estimate the change in in vivo ACL forces in response to full body weightbearing using a weighted mean statistical method. The data demonstrated that by assuming that there was no tension in the ACL under zero weightbearing, the changes in in vivo ACL force caused by full body weightbearing were 131.4±16.8 N at 15 deg, 106.7±11.2 N at 30 deg, and 34.6±4.5 N at 45 deg of flexion. However, when the assumed tension in the ACL under zero weightbearing was over 20 N, the change in the estimated ACL force in response to the full body weightbearing approached an asymptotic value. With an assumed ACL tension of 40 N under zero weightbearing, the full body weight caused an ACL force increase in 202.7±27.6 N at 15 deg, 184.9±22.5 N at 30 deg, and 98.6±11.7 N at 45 deg of flexion. The in vivo ACL forces were dependent on the flexion angle with higher force changes at low flexion angles. Under full body weightbearing, the ACL may experience less than 250 N. These data may provide a valuable insight into the biomechanical behavior of the ACL under in vivo loading conditions.

Effects of pregnancy on cardiac function and myosin enzymology in the rat

1987 ◽  
Vol 252 (4) ◽  
pp. H846-H850 ◽  
Author(s):  
P. M. Buttrick ◽  
T. F. Schaible ◽  
A. Malhotra ◽  
S. Mattioli ◽  
J. Scheuer
Keyword(s):  
Cardiac Function ◽  
Cardiac Contractility ◽  
Volume Overload ◽  
Loading Conditions ◽  
Protein Biochemistry ◽  
Rat Hearts ◽  
Velocity Relationship ◽  
Force Velocity ◽  
In Vivo Loading

Previous studies of cardiac function during pregnancy, while suggesting that this condition is associated with improved myocardial contractility, have been biased by the altered in vivo loading conditions. Therefore, we have investigated intrinsic cardiac function and contractile protein biochemistry during pregnancy in isolated rat hearts under controlled loading conditions. Animals were impregnated and studied after 1 and 3 wk and 2-3 days postpartum (gestation 21 days). The data show that hearts from pregnant animals (at 3 wk) had improved contractile performance as manifested by an 11% increase in fractional shortening, a 20% increase in velocity of circumferential fiber shortening, and an upward-shifted force-velocity relationship. These findings were paralleled by a 16% increase in Ca2+-activated myosin and an 11% increase in actin-activated ATPase activities. Thus pregnancy in the rat is associated with slightly improved cardiac contractility and biochemistry. This may relate directly to the hormonal status of the pregnant animal or to the effects of chronic volume overload.

Outcomes and Postoperative Complications of Robot-Assisted Laparoscopic Hysterosacropexy: Initial Experience

2015 ◽  
Vol 95 (1) ◽  
pp. 44-49 ◽  
Author(s):  
Maria Angela Cerruto ◽  
Carolina D'Elia ◽  
Francesca Maria Cavicchioli ◽  
Stefano Cavalleri ◽  
Matteo Balzarro ◽  
...  
Keyword(s):  
Uterine Prolapse ◽  
Pelvic Organ ◽  
Consecutive Series ◽  
Complication Rates ◽  
Early Complications ◽  
Robot Assisted ◽  
Female Patients ◽  
The Mean ◽  
Record Review

Background: Pelvic organ prolapse is a common condition, affecting about 50% of women with children. The aim of our study was to evaluate results and complication rates in a consecutive series of female patients undergoing robot-assisted laparoscopic hysterosacropexy (RALHSP). Materials and Methods: We performed a medical record review of female patients with uterine prolapse who had consecutively undergone RALHSP from February 2010 to 2013 at our department. Results: Fifteen patients were included in the analysis. All patients had uterine prolapse stage ≥II and urodynamic stress urinary incontinence. The mean age was 58.26 years. According to the Clavien-Dindo system, 4 out of 15 patients (26.6%) had grade 1 early complications and 1 patient had a grade 2 complication. At a median follow-up of 36 months, there was a significant prolapse relapse rate of 20% (3/15). Conclusion: In our hands RALHSP is easy to perform, with satisfying mid-term outcomes and a low complication rate.

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