bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of Retinal Stent Using Finite Element Analysis
Authors: Rusovici R. , Dalli D. , Mitra K. , Calhoun M. , Mazzocchi R. , Grace M.
Published: January 2014

The retina is a light-sensitive tissue layer that lines the inside of the eye and relays visual information directly to the brain via the optic nerve. Retinal detachment occurs when the retina is lifted or pulled from its physiological location. This condition can result in partial or total vision loss. Retinal detachmentis a leading cause of permanent vision loss.
Longitudinal Effect of Pressure Drop on the Intima-Media Thickening of the Venous Segment of the Arteriovenous Fistula
Authors: Rajabi-Jaghargh Ehsan , Krishnamoorthy Mahesh K. , Banerjee Rupak K.
Published: January 2014

Venous stenosis is one of the primary causes of the arteriovenous fistula (AVF) maturation-failure and is characterized by vasoconstriction and significant intima-media thickening (IMT). Although the hemodynamic endpoints are believed to play a crucial role in the pathogenesis of venous stenosis, the exact mechanism behind this is unclear. Our hypothesis is that the changes in the pressure drop over time (Δp′) can influence the remodeling factors in AVFs: changes in luminal diameter (ΔDh) and IMT. Curved (C-AVF; n = 3) and straight (S-AVF; n = 3) AVFs were created between the femoral arteries and veins of 3 pigs. CT-scan and ultrasound were utilized to numerically evaluate the flow field, and thus pressure drop in AVFs at 2D (D: days), 7D, and 28D post-surgery. For each AVF, IMT was also measured at 4 histological blocks along the vein. For the C-AVF, the pressure drop consistently decreased over time (from 18.32 mmHg at 2D to 4.58 mmHg at 28D), while opposite trend was found for the S-AVF (from 12.91 mmHg at 2D to 24.49 mmHg at 28D). The Δp′ was negative at all the histology blocks for C-AVF which showed the reduction in the resistance over time due to dilation (positive ΔDh) and outward hypertrophy of the venous segment (positive ΔDh/IMT). In contrast, Δp′ was mostly positive for the S-AVF which showed the increase in the resistance due to vasoconstriction (negative ΔDh) and inward hypertrophy (negative ΔDh/IMT). Thus, measuring Δp′ at the successive post-surgery time points can provide important information on the remodeling behavior of AVFs. Also, creating AVFs in a surgical configuration that can result in negative Δp′ and thus favorable remodeling could influence the life expectancy of the dialysis patients.
Anti-Adhesions Properties of Polyelectrolyte Complex Based Films
Authors: Verma Devendra , Previtera Michelle , Schloss Rene , Langrana Noshir
Published: January 2014

Adhesions are abnormal fibrous connections between tissues and can occur following virtually any type of surgery (1). They are often painful and can severely disrupt normal organ function. The incidence of adhesions following surgery is very high; some estimate an incidence as high as 80%. Thus, the prevention of adhesions has the potential to save the healthcare market billions of dollars and improve the lives of hundreds of thousands of patients.
A Virtual Test Bench to Study Transport Phenomena in 3D Porous Scaffolds Using Lattice Boltzmann Simulations
Authors: Pennella Francesco , Gentile Piergiorgio , Deriu Marco A. , Gallo Diego , Schiavi Alessandro , Ciardelli Gianluca , Lorenz Eric , Hoekstra Alfons G. , Audenino Alberto , Morbiducci Umberto
Published: January 2014

In tissue engineering (TE), scaffolds are widely used to provide a suitable and native-like environment for cell growth, organization, and proliferation. Microstructure of TE scaffolds is fundamental to the cell attachment and in-depth penetration, in conjunction with biological factors as cell seeding and nutrients supply. In particular, several studies have established that an adequate transport of nutrient through the scaffold is fundamental for culturing cells [1]. Hence, the easiness at which fluids/species move through the scaffold and friction forces exherted from fluid motion, have a marked impact in TE processes [2]. Mass transport through scaffolds is a phenomenon that can be described at different scales, the molecular level (nanoscale), the single-pore dimension level (microscale) and the whole-sample level (macroscale). In this work we present a virtual test bench where realistic 3D models of porous TE scaffolds are reconstructed from micro-CT images and the transport phenomena through them is simulated in silico by applying the Lattice Boltzmann Method (LBM). The final aim is to create an effective in silico tool suitable to study and optimize transport phenomena of porous scaffolds. The application of the LBM is justified by its versatility in simulating flows in irregular porous media (i.e. simplicity of handling complex boundaries) and in providing insights into transport properties such as permeability [3–4] and physical quantities as the shear stress, which are barely achievable experimentally [2]. Here, the virtual tool is applied to evaluate the performance of three biomimetic bioactive glass/polymer composite porous scaffolds for bone tissue regeneration with well-known mechanical and chemical properties, but never characterized in terms of transport phenomena. The in silico results are macroscopically validated in terms of permeability (kC) by comparison with experimental permeability (kE) measurements obtained by means of a dedicated test bench, very recently proposed for the characterization of porous media [5].
Initial Assessment of Effects of Diabetes and Advanced Age on the Construction and Efficacy of Human Adipose-Derived Stem Cell-Based Tissue Engineered Blood Vessels
Authors: Krawiec Jeffrey T. , Phillippi Julie A. , Philips Brian J. , Hong Yi , Wagner William R. , St. Croix Claudette , Watkins Simon C. , Gleason Thomas G. , Rubin J. Peter , Vorp David A.
Published: January 2014

Tissue engineering, the use of a biodegradable scaffold with incorporation of a cellular source, particularly with mesenchymal stem cells (MSCs) has shown great promise in developing blood vessel grafts 1. Vascular tissue engineering not only combats the important clinical need for bypass grafts but also has the potential to advance current approaches by limiting intimal hyperplasia, thrombosis, and extended cell culture times 2–5. However, despite significant progress in this field, many preclinical evaluations of tissue engineered blood vessels (TEBVs) utilize cells from donor bases that are either non-human or from humans that are healthy 1. It is therefore unclear if cells from compromised donor populations are able to function effectively as the cellular component of TEBVs. This is particularly important for MSC-based TEBVs as they rely heavily on cellular processes to remodel in vivo to a native-like structure, with the current hypothesis being that MSCs stimulate the migration of smooth muscle cells (SMCs) from the adjacent vascular walls 6,7. While some studies have noted that cellular dysfunction exists with the presence of certain conditions 8–11, it is critically important for the field of TEBVs to evaluate human cells, specifically those from patients at high risk for cardiovascular disease such as diabetics and those of advanced age.
Problem Based Learning Biomechanics Lab: Running Shoes: Friend or Foe
Authors: George Stephanie M.
Published: January 2014

The problem based learning (PBL) model of learning inherently provides an environment in which students can practice real world biomedical engineering utilizing cutting edge tools. The independent nature of the model promotes leadership and lifelong learning behaviors because the students are responsible for their learning and progress. The open-endedness of the problems encourages creativity and innovation as the students are allowed to define the direction and scope of the project. Since PBL is a team approach, students will become familiar with diversity of thought but also diversity in learning and problem solving styles. The proposed case will be on a much grander scale than anything the students have previously experienced. The activities will reinforce material from lecture and previous courses as well as teach the problem solving process.
Biomechanical Performance of Metallic and Bioabsorbable Interference Screw for Tibial Graft Fixation in ACL Reconstruction
Authors: Moré Ari Digiacomo Ocampo , Pizzolatti André Luiz Almeida , Fancello Eduardo , Roesler Carlos Rodrigo de Mello
Published: January 2014

Background: The interference screw is widely used to fix the graft in the tibial portion in anterior cruciate ligament (ACL) reconstruction. However, there is no evidence of what type of screws, if metallic or bioabsorbable, have the better mechanical performance. Methods: Twenty porcine tibias, 10 for metallic and 10 for bioabsorbable screw, were submitted to cyclic loading between 50 N to 250 N for 1000 cycles at 1 Hz. For devices that not failed during cyclic loading, a tensile test to failure was performed at strain rate of 50 mm/min. Results: There were no differences in the stiffness and ultimate failure load between metallic and bioabsorbable screw. Conclusion: There is no difference in biomechanical performance between metallic and bioabsorbable screw.
Tibio-Femoral Contact Force During Gait: An Iterative Method Using EMG-Constrained Multi-Body Simulation and Finite Element Analysis
Authors: Pianigiani Silvia , De Groote Friedl , Scheys Lennart , Gillen Pierre , Labey Luc , Innocenti Bernardo , Jonkers Ilse
Published: January 2014

In this study, we present an innovative methodology (Figure 1) to calculate patient specific tibio-femoral (TF) contact forces by integrating medical image data, 3D skin-mounted marker trajectories, ground reaction forces, electromyography (EMG) data and finite element analysis (FEA). The muscle redundancy problem is solved through an EMG-constrained optimization approach. Calculated muscle forces are input to a FEA to calculate TF contact forces. Kinematics of the degrees of freedom (DOFs) of the knee that cannot be accurately assessed from the trajectories of skin-mounted markers, are estimated using a novel iterative procedure which combines muscle force calculation with dynamic FEA. The presented methodology is applied to analyze TF contact forces of a walking trial performed on an instrumented treadmill of which the speed was sequentially ramped up and down. The results presented in this abstract will be validated against the in-vivo measured TF contact forces.
Functional Consequences of Glucose and Oxygen Deprivation in Engineered MSC-Based Cartilage Constructs
Authors: Farrell Megan J. , Shin John , Mauck Robert L.
Published: January 2014

Clinical implementation of stem cell-based cartilage repair techniques has been limited by the inability of these cells to produce cartilaginous tissue equivalent to that produced by native chondrocytes. We have recently shown that while bulk mechanical properties of mesenchymal stem cell (MSC)-laden constructs are lower than chondrocyte-laden constructs, MSCs can in fact produce tissue that matches or exceeds the biochemical and mechanical properties produced by chondrocytes in regions where there is maximal nutrient supply [1]. We also noted that in the central regions of constructs, where nutrient and oxygen availability is lowest (due to consumption through the construct depth), MSC viability was markedly lower than in the outer regions and drastically lower than the center of chondrocyte-laden constructs maintained similarly. These data suggest that MSCs can achieve a high anabolic functionality when they undergo chondrogenesis (via the provision of TGF-β3) and in doing so can produce tissue of equivalent or greater properties than chondrocytes. However, unlike chondrocytes, MSCs appear thrive only when they are provided with a sufficient nutrient supply. To further delineate the role of microenvironmental stressors [2, 3, 4] on MSC viability and functional capacity, we evaluated the impact of glucose and oxygen deprivation, in the presence and absence of TGF-β, during long term culture. Furthermore, since MSC isolation procedures result in a heterogeneous cell population [5,6], we investigated whether different clonal populations respond to these microenvironmental stressors in a distinct fashion.
The Use of Plantar Insole Pressure Sensors to Predict the Free Torque Produced at the Shoe-Surface Interface During Internal Rotation of the Body Relative to a Planted Foot
Authors: Weaver Brian T. , Fitzsimons Kathleen A. , Braman Jerrod E. , Haut Roger C.
Published: January 2014

High ankle sprains are commonly associated with injury to the distal tibiofibular syndesmotic ligaments and represent a more disabling problem for athletes than other ankle sprains [1]. This injury is associated with excessive internal rotation of the body relative to a planted foot [2]. Torsional traction between the shoe and the playing surface is a factor in these injuries [3].
Finite Element Human Body Model Thorax Response Validation With Matched Experimental Tests
Authors: Danelson Kerry A. , Gaewsky James P. , Golman Adam J. , Stitzel Joel D.
Published: January 2014

Finite Element Models (FEMs) are increasingly used to evaluate occupant response and safety system effectiveness in automotive safety research.[1, 2] These models are validated against experimental tests with known results to evaluate the model’s ability to predict the occupant response. The FEM used for this study was the Total HUman Model for Safety (THUMS). The occupant thorax model has already been validated in three basic thorax loading conditions.[3] The hypothesis of this study was if the model had been successfully validated in these simplified configurations, additional loading conditions that involve a more complex load path should also follow the experimental response.
Towards Engineering Whole Bones
via Endochondral Ossification
Authors: Sheehy Eamon J. , Vinardell Tatiana , Buckley Conor T. , Kelly Daniel J.
Published: January 2014

Tissue engineering applications aim to replace or regenerate damaged tissues through a combination of cells, three-dimensional scaffolds, and signaling molecules [1]. The endochondral approach to bone tissue engineering [2], which involves remodeling of an intermittent hypertrophic cartilaginous template, may be superior to the traditional intramembranous approach. Naturally derived hydrogels have been used extensively in tissue engineering applications [3]. Mesenchymal stem cell (MSC) seeded hydrogels may be a particularly powerful tool in scaling-up engineered endochondral bone grafts as the low oxygen conditions that develop within large constructs enhance in vitro chondrogenic differentiation and functional development [4]. A key requirement however, is that the hydrogel must allow for remodeling of the engineered hypertrophic cartilage into bone and also facilitate vascularization of the graft. The first objective of this study was to compare the capacity of different naturally derived hydrogels (alginate, chitosan, and fibrin) to generate in vivo endochondral bone. The secondary objective was to investigate the possibility of engineering a ‘scaled-up’ anatomically accurate distal phalange as a paradigm for whole bone tissue engineering.
Tumor Geometry and SAR Distribution Generated From MicroCT Images for Tumor Temperature Elevation Simulation in Magnetic Nanoparticle Hyperthermia
Authors: LeBrun Alexander , Manuchehrabadi Navid , Attaluri Anilchandra , Ma Ronghui , Zhu Liang
Published: January 2014

Previous investigations in magnetic nanoparticle hyperthermia for cancer treatments have demonstrated that particle size, particle coating, and magnetic field strength and frequency determine its heating generation capacity. However, once the nanoparticles are manufactured, the spatial distribution of the nanostructures dispersed in tissue dominates the spatial temperature elevation during heating. 1–3 Therefore, understanding the distribution of magnetic nanoparticles in tumors is critical to develop theoretical models to predict temperature distribution in tumors during hyperthermia treatment. An accurate description of the nanoparticle distribution and the tumor geometry will greatly enhance the simulation accuracy of the heat transfer process in tumors, which is crucial for generating an optimal temperature distribution that can prevent the occurrence of heating under-dosage in the tumor and overheating in the healthy tissue. Recently studies by our group have demonstrated that the nanoparticle concentration distribution in tumors can be visualized via microCT image due to the density elevation of the presence of magnetic nanoparticles. 4 The problem is the intensive memory requirements to directly import the microCT images to numerical simulation software packages such as COMSOL. Although commercial software packages exist to handle detailed entities inside tumors, they are very expensive to purchase. In addition, having very small entities at the micrometer level inside the tumor geometry may provide challenge to numerical simulation software to accept the generated geometry.
A Novel Flexor Tendon Repair Device: Biomechanical Testing in Cadaver Tendon and In-Vivo Verification Using a Rabbit Model
Authors: Reese Shawn P. , Kubiak Eric N.
Published: January 2014

The digital flexor tendons of the hand, including the flexor digitorum profundus (FDP), are responsible for enabling finger flexion and gripping. Injuries involving a partial or complete laceration to the digital flexor tendons are common and associated with a high incidence of morbidity [1]. The current state of the art for flexor tendon repair is the use of two or more core sutures in combination with an epitendinous circumferential suture. There are inherent limitations to suture based methods, including a high level of skill required to perform the suture repair, increased surgical time and the tendency for sutures to strangulate the tissue (creating local tissue ischemia). Suture based repairs often result in sub-optimal clinical outcomes, with reported failure rates ranging from 4%–10% [2]. In order to address these limitations, a novel non-suture based repair device has been developed. The objectives of this study were twofold. The first objective was to determine the gapping strength of the device in cadaver FDP tendons so that comparisons could be made to values reported in the literature for suture based repairs. The second objective was to determine the in-vivo capability of the device to facilitate tendon repair, relative to a suture control, in a rabbit model at a five week time point.
Influence of Exercise Condition on Tissue Blood Temperature Using Whole Body Model
Authors: Zachariah Swarup A. , Paul Anup K. , Banerjee Rupak K. , Zhu Liang
Published: January 2014

Predicting thermal responses of the human body accurately during different exercise conditions is of increasing importance. Computing changes in the core body temperature (T c) during exercise require detailed modeling of both the body tissue temperature and the time-dependent blood temperature. Predicting changes in T c is challenging because the model needs to respond effectively to the changes in perfusion or sweating. Our study was to demonstrate the ability of a recently developed whole body heat transfer model. It simulates the tissue-blood interaction to predict the thermal response of the human body under different exercise intensities. The cases simulated were of a human being walking on a treadmill at 0.9, 1.2 and 1.8 m/s for 30 minutes. It was shown that T c was effectively regulated within 0.17 °C of the steady state value of 37.23 °C for the three cases by means of adjusting the cardiac output; varying between 15 to 25 liters per minute.
Meniscal Allografts: Biomechanical Consequences of Different Methods of Fixation
Authors: Wang Hongsheng , Chen Tony , Gee Albert , Hutchinson Ian , Stoner Kirsten , Warren Russell , Maher Suzanne
Published: January 2014

Complete removal of the meniscus (meniscectomy) often leads to early-onset of osteoarthritis due to changes in contact mechanics 1,2. To counteract these changes, the removed meniscus is often replaced with an allograft. Many variables can affect the surgical outcome of meniscal transplantation (bone geometry, graft size, fixation technique, level of activity, limb alignment, etc.) 3,4,5. Among them, the method of fixation is the most readily controlled. Two commonly used techniques are: (i) trans-osseous suture fixation via bone plugs, where bone plugs are machined at the anterior and posterior horns of the graft and implanted into appropriately sized tibial bone tunnels, and (ii) suture fixation at the meniscal horns, where the sutures are drawn through tibial bone tunnels and tied over a bone-bridge. But the mechanical consequences of these fixation techniques, specifically, how they affect knee mechanics are unclear.
High Performance Microfluidic-Based DNA Isolation Chip
Authors: Darabi Jeff
Published: January 2014

Magnetic separation is one of the effective ways to separate specific biological entities such as DNA/RNA, bacteria, and cells from their native environment for subsequent downstream analysis. The process involves the labeling of the desired biological entity with magnetic beads followed by separating the tagged entities via a magnetic separation device. In conventional tube-based magnetic separation, magnetically labeled biological entities are retained on the inner wall of the tube by applying an external magnet, while the supernatant is decanted off. Removing the tube from the magnetic field enables resuspension of the target entity. Although widely used, there are limitations to the conventional magnetic separation method. For example, there is a significant sample loss due to multiple sample handling, washing, and transfer. In addition, manual magnetic separation systems are labor intensive and their effectiveness is user-dependent.
Automated Hexahedral Mesh Generation in a Complex Vascular Tree: The Extended Treemesh Method
Authors: Bols Joris , De Santis Gianluca , Degroote Joris , Verhegghe Benedict , Segers Patrick , Vierendeels Jan
Published: January 2014

Numerical analysis of the cardiovascular system can provide medical researchers with information that cannot (easily) be measured in a clinical setting and may contribute to a better comprehension and insight into the pathophysiology of cardiovascular diseases. In addition, numerical models offer a computational environment in which both new and existing medical procedures and devices can be tested and optimized, which is both cost effective and patient friendly. The continuous improvement of computational methods, computational power and medical imaging techniques strengthens the general belief that computational models will eventually find their way into clinical practice, what can be seen in todays trend toward more realistic patient-specific models. This new trend brings along more complex geometries and larger computational domains for which the quality of the corresponding meshes can become a bottle neck for the image-based analysis, both in computation time as in accuracy of the solution. Therefore, the Treemesh method has been developed by De Santis et al. [1], an algorithm to generate high-quality hexahedral meshes in a multi-block structured way. However, when the geometry becomes too complicated, a high-quality Treemesh for the fluid domain can become hard to generate. In this work, the extended Treemesh (XTreemesh) method has been developed, an algorithm to auto-generate a high-quality unstructured hexahedral mesh for both the fluid domain and the structural domain of complex image-based vascular tree geometries.
A Multiscale Approach to Modeling the Passive Mechanical Contribution of Cells in Tissues
Authors: Lai Victor K. , Hadi Mohammad F. , Tranquillo Robert T. , Barocas Victor H.
Published: January 2014

In addition to their obvious biological roles in tissue function, cells often play a significant mechanical role through a combination of passive and active behaviors. Phenomenological and continuum modeling approaches to understand tissue biomechanics have included improved constitutive laws that incorporate anisotropy in the extracellular matrix (ECM) and/or cellular phenomenon, e.g, [1]. The lack of microstructural detail in these models, however, limits their ability to explore the respective contributions and interactions between different components within a tissue. In contrast, structural approaches attempt to understand tissue biomechanics by incorporating microstructural details directly into the model, e.g., the tensegrity model [2], cellular solids models [3], or biopolymer models [4]. Research in our group focuses on developing a comprehensive model to predict the mechanical behavior of soft tissues via a multiscale approach, a technique that allows integration of the microstructural details of different components into the modeling framework. A significant gap in our previous models, however, is the absence of cells. The current work represents an improvement of the multiscale model via the addition of cells, and investigates the passive mechanical contribution of cells to overall tissue mechanics.
Phosphotungstic Acid Diffusion in Porcine Ocular Tissue for MicroCT Shape Reconstruction
Authors: Pyne Jeff D. , Danford Forest L. , Vande Geest Jonathan P.
Published: January 2014

For any ocular research involving finite element analysis, measurement of sample geometry is an important step that determines the accuracy of subsequent results. A shape reconstruction method using diffused Phosphotungstic Acid (PTA) within ocular samples for measurement with a microCT device will be presented here. With all finite element modeling, the material properties of the tissue must be determined using techniques such as digital image correlation (DIC) [1]. With this technique, the limitations for displacement measurement accuracy are the size of non-altering markers and camera resolution. This means that only certain material points can be tracked and the non-tracked material points must be interpolated in finite element models. Along with this interpolation, techniques for thickness measurements across the ocular tissue such as using calipers or a pachymeter [2] typically only give values at a small quantity of points while the thickness changes continuously across the tissue. The PTA staining will provide the advantage of internal geometry as well as external shape to give thickness across the entire sample. While these other techniques provide repeatable results, we believe the PTA method presented here for geometry acquisition provides accurate shape reconstruction of the tissue for finite element applications. The purpose of this study was to quantify the depth of penetration of PTA in porcine scleral samples as a function of PTA concentration and time.
Validation of Digital Image Correlation Techniques for Strain Measurement in Biomechanical Test Models
Authors: Rogge Renee D. , Small Scott R. , Archer Derek B. , Berend Michael E. , Ritter Merrill A.
Published: January 2014

Many previous biomechanical studies of bone and bone substitutes have estimated strains in these materials using strain gages. The purpose of this study was to compare digital image correlation (DIC) strain measurements to those obtained from strain gages in order to assess the applicability of DIC technology to common biomechanical testing scenarios. Compression and bending tests were conducted on aluminum alloy, polyurethane foam, and laminated polyurethane foam specimens. Results showed no significant differences in the principal strain values (or the variances) between strain gage and DIC measurements on the aluminum alloy and laminated polyurethane foam specimens. There were significance differences between the principal strain measurements of the non-laminated polyurethane foam specimens, but the deviation from the theoretical results was similar for both measurement techniques. In summary, DIC techniques provide similar results to those obtained from strain gages and also provide full field strain results.
Examination of Geometric Effects on Stress Wave Propagation and Applications in Football Helmet Design
Authors: Johnson Kyle , Trim M. W. , Horstemeyer Mark F. , Prabhu R.
Published: January 2014

A recent study of college and high school football players demonstrated that 5.1% sustained at least one concussion in a single season. Considering the number of individuals that participate in football in the United States, this percentage equates to a staggering number [1]. The information and attention dealing with concussions and traumatic brain injury (TBI) has greatly increased recently, and represents a need for more advanced helmets that can eliminate concussions as well as other forms of TBI. In order to obtain this goal, lessons can be learned from high speed impacts in nature, particularly the shock-mitigating effects of the bighorn sheep’s (or ram’s) horn and woodpecker’s hyoid bone. For instance, during fights between male bighorn sheep, the rams clash together at speeds up to 5.5 m/s, causing forces up to 3400 N [2]. Even while undergoing these tremendous forces, the animals are rarely injured, which leads to the notion that the horn geometry plays a role in mitigating the shock wave. The woodpecker’s hyoid bone extends around the skull in a spiral shape. It aids the woodpecker in extending its tongue and helps bypass vibrations generated from drumming, which protects the brain from shock [3]. Does the reoccurrence of this curious (tapered spiral) shape throughout nature have some significance in regards to energy dissipation and shock absorption abilities inherent to its geometry? Answering this was the primary goal of this study.
Manifestations of Primary Blast-Induced Ocular Trauma
Authors: Reilly Matthew A. , Sherwood Daniel , Watson Richard , Gray Walt , Sponsel William E. , Thoe Kimberly , Lund Brian , Glickman Randolph
Published: January 2014

Prevalence of ocular trauma in battlefield injury has increased significantly in recent years. The majority of such injuries are due to improvised explosive devices. While impact-induced injuries are relatively well characterized, little is known regarding the effects of primary blast. We exposed porcine eyes to a simulated blast using a shock tube to correlate the blast overpressure with various trauma manifestations.
Effect of Thermosensitive Hydrogel Injection on Mechanical Behavior of Porcine Myocardium
Authors: Wang Bo , Bertucci Robbin , Li Zhenqing , Prabhu Raj , Williams Lakiesha , Guan Jianjun , Liao Jun
Published: January 2014

Myocardial infarctions (MI) afflict approximately 1.1 million individuals in the United States each year and exhibit an increasing prevalence worldwide due to the improvement of economic levels. Injection therapies for MI using biodegradable biomaterials with/without cells have been recognized to stabilize and preserve mechanical properties in the infarcted area in pre-clinical animal models. Recently, thermally responsive hydrogels, which can be injected from a syringe below 37 °C and then solidified at body temperature, are considered an attractive material for injection therapy.[1] The advantages of using an injectable hydrogel lie in its high moldability, capability of filling irregular shaped defects, and ability to be delivered to the in vivo environment by limited surgical invasion. However, it is still not very clear how the injection of thermosensitive hydrogel affects local tissue structure and mechanics. Thus, the goal of this study is to investigate possible alterations in myocardial structure and mechanical behavior after hydrogel injection using a well-controlled in vitro model.
A Coupled Model of LV Growth and Mechanics Applied to Pressure Overload Hypertrophy
Authors: Farrar G. E. , Veress A. I.
Published: January 2014

Hypertension currently affects approximately one third the population in the United States, and represents a major economic burden on the health care system with an estimated annual direct and indirect cost of $50.6 billion [1]. In the case of systemic hypertension, the left ventricle (LV) must work against increased pressure load to pump blood to the body. Over time, this excessive work causes hypertrophy of the myocardium (thickening of the myofibers). While initially a compensatory mechanism, hypertrophy can eventually lead to heart failure (HF) [2]. Predictive modeling of the hypertrophic growth will lead to a better understanding of the disease mechanisms, which in turn has the potential to lead to better treatment strategies.
Development of Electromagnetic Stimulation System to Aid Patients Suffering From Vocal Fold Paralysis
Authors: Burks William Garret , Jaramillo Paola , Leonessa Alexander
Published: January 2014

Vocal fold paralysis affects approximately 7.5 million Americans. Paralysis can be caused by numerous conditions, including head, neck or surgical trauma, endotracheal intubation, neurological conditions, cancer, tumors, just to mention a few. Currently, vocal fold paralysis treatment involves surgery and voice therapy. The vocal folds are composed of a three part material stretched along the larynx, which enables frequency change. Intrinsic laryngeal muscles coordinate the motion of vocal folds during respiration, vocalization, and aid in airway protection. Sensory information is carried by the Superior Laryngeal Nerve (SLN) and the Recurrent Laryngeal Nerve (RLN). Injury to the RLN results in paralysis of all laryngeal muscles excluding the cricothyroid muscle [1]. Although optimal larynx reinnervation has been extensively researched and implemented to improve voice paralysis [2], voice electrotherapy offers an alternative to effectively stimulate the larynx muscles for voice production, breathing and airway protection. One of the main causes of voice disorders is neurological in nature and causes abnormal vocal fold vibration. Of particular importance to this research is paralysis due to RLN injury, which causes acute temporary paralysis [3]. Currently, invasive electrical stimulus is used to activate muscle function; however, abnormal activation of muscle patterns causes muscles to function out of synchronization resulting in low vocal output [4]. For this reason, our work focuses on the development of an effective electromagnetic stimulation system to aid patients with unilateral vocal fold paralysis by stimulating the RLN and in turn reinnervating the adequate laryngeal muscles involved in the vocal fold motion for the purposes of sound vocalization, respiration, and airway protection. So far, a proof of principle has been developed and evaluated to assess the system’s feasibility. The preliminary experiments have been conducted using BioMetal Fibers (BMF) (Toki Corporation, Japan), which are fiber-like solid state actuators designed to contract and extend similar to muscles. BMF contracts when stimulated through a current generated in this case through an electromagnetic field.
Patient-Specific Valve Dynamics Using 3D Fluid-Structure Interaction Modeling: Comparison Between Bicuspid and Tricuspid Aortic Valves
Authors: Govindarajan V. , Mousel J. , Vigmostad S. C. , Udaykumar H. S. , Levack M. M. , Gorman J. H. , Jackson B. M. , Gorman R. C. , Chandran K. B.
Published: January 2014

Aortic valve diseases such as congenital bicuspid aortic valve (BAV) and progressive calcification in tricuspid valves affect the hemodynamics in the aortic arch. In addition to leaflet calcification, BAVs are associated with other ailments such as aortic coarctation, aneurysm and dissection [1]. It has also been observed that progressive calcification is accelerated in the case of BAVs compared to normal tricuspid valves. While it is not yet known whether the geometric distortion in BAVs is the main cause of calcification [2] in these valves, the distortion in the leaflets may give rise to altered stresses during the deformation processes which might play a role in accelerating the calcification process in BAVs. In addition, the altered flow caused by the change in geometry could alter the local fluid stresses during the opening phase, which might affect the endothelial lining of the aortic wall. Analyzing and comparing BAV and tricuspid aortic valves as a fluid-structure interaction problem will help determine the stress distribution on the leaflets during opening phase, and enable the examination of altered flow dynamics in the ascending aorta. In this study, the opening phase of a patient-specific bicuspid aortic valve is analyzed at physiological conditions and compared with the opening phase of a tricuspid aortic valve.
Contrasting the Thrombotic Phenotype of Donor-Matched Endothelial Outgrowth Cells and Endothelial Cells
Authors: Glynn Jeremy J. , Hinds Monica T.
Published: January 2014

Despite the increasing burden of cardiovascular disease, vascular tissue engineering strategies have had limited success in achieving long-term patency in grafts less than 4 mm in diameter. Graft failure is often due to occlusion by thrombosis or intimal hyperplasia. Recognizing the capacity of endothelial cells (ECs) to properly coordinate these processes in vivo, much research has investigated the use of ECs to line the lumens of vascular grafts to improve patency (Zilla et al. 1994). However, the limited availability of autologous ECs and the donor site morbidity resulting from EC harvest has limited the clinical potential of these cellularized constructs.
Wall Stress Estimation of Human Heart Under the Effect of High Accelerations
Authors: Jamshidi Masood , Ahmadian Mohammad Taghi
Published: January 2014

Human body is constantly under the influence of acceleration loads in environments such as combat flying. This study investigates the effect of body acceleration on human heart function by using finite element analysis. The nonlinear mechanical behavior of myocardium is modeled by Yeoh hyperelastic model. Stress-strain curves of myocardium are determined based on uniaxial compression tests on bovine heart samples. Nonlinear least square curve fitting is conducted in order to obtain material parameters. Heart geometrical modeling in three-dimension is done by segmentation of cardiac MRI images. Obtained material coefficients are assigned to the constructed heart model and appropriate pressure and acceleration loads are considered. By application of finite element method, stress distributions are calculated. Results indicate average stress in the internal wall of left ventricle is increased by 9.4% from 15.9 to 17.4kPa as the acceleration increases from +1G to +6G.
Hemodynamic and Structural Implications of Asymmetric Deployment of Transcatheter Aortic Valves: An In Vitro Study
Authors: Gunning Paul S. , Saikrishnan Neelakantan , Yoganathan Ajit P. , McNamara Laoise M.
Published: January 2014

Aortic stenosis is an age related degenerative disease of the aortic valve that causes narrowing of the valve and aortic regurgitation [1]. Transcatheter Aortic Valve (TAV) implantation is a percutaneous alternative to open heart surgery, which allows for the treatment of a cohort of patients for whom conventional surgery is deemed excessively risky due to high postoperative mortality rates or pre-existing illness [2].
Effects of Cytoskeletal Tension on Chick Dorsal Root Ganglia
Authors: Omar Hamzeh W. , Sundararaghavan Harini G.
Published: January 2014

About 50,000 cases of peripheral nerve injuries occur annually [1] resulting in patient pain or loss of touch. Methods of repairing peripheral nerve gaps is essential for aiding in patient recovery. During development, growth, and joint movement, nerves are exposed to mechanical tension that is hypothesized to aid in their growth. Neurons can grow less than .5–1 mm/day but are known to grow up to ∼3 cm/day during development, theorized from factors of stretch on cell cytoskeleton during growth [2,3]. Our focus was to investigate the effects of mechanical strain on nerve growth. We fabricated biodegradable, electrospun, polycaprolactone (PCL) scaffolds to create three-dimensional, nanofibrous networks for Dorsal Root Ganglia (DRG) neuron extension and growth. To test the effects of scaffold stretch and tension on DRG growth, scaffolds were stretched using a custom scaffold stretcher. DRG growth was investigated for 3mm changes in scaffold length on days 0 and 1 of DRG development. Further investigation of DRG growth on day 2 and 3 as well as stretches of 6 and 9mm are being performed. In addition, an incremental stretch test for total stretches of 3, 6, and 9mm will be performed.
Humeral Torsion and Shoulder Biomechanics: Comparison of a Novel Ultrasonographic Technique and the Computed Tomography Benchmark
Authors: Thurston Bryan , Thigpen Chuck , Bailey Lane , Shanley Ellen , Desjardins John , Kissenberth Michael , Sauers Eric , Harman Melinda
Published: January 2014

Bone remodeling is a function of the stress applied to the bone. In the case of the glenohumeral (GH) joint, an initial external rotation of the humerus (retrotorsion) at birth derotates with age, as normal processes are anterior to the shoulder, such that the humerus is comparatively internally rotated (anterotorsion) by adulthood 1,2. However, in the case of certain athletes, such as pitchers, an overhead throwing motion has been shown to resist the anterotorsion process by means of strong, external torque around the humeral growth plate 3,4.
The Impact of Boundary Conditions on Surface Curvature Measurements of Polypropylene Mesh in Response to Uniaxial Loading
Authors: Barone William R. , Amini Rouzbeh , Maiti Spandan , Moalli Pamela , Abramowitch Steven
Published: January 2014

Pelvic organ prolapse (POP) is defined as the descent of the pelvic organs into the vaginal canal. POP is a widespread condition among women, with a 7% lifetime risk for a single operation1. For surgical treatment, polypropylene mesh is often implanted to restore support to the pelvic organs. However, up to 20% of those who undergo surgery with mesh will require repeat operations for recurrent symptoms or complications2. One of the most common complications is mesh erosion3. Erosion is characterized by degeneration of the native vaginal tissue in contact with the mesh, resulting in the mesh migrating through the vagina. Though the cause of mesh erosion is undefined, surgeons have described this complication by the appearance of mesh “contraction”, “buckling”, “wrinkling”, and/or “bunching”. Some have even described this as an “accordion effect”.
Effects of Channel Size and Shear Rate on Platelet Margination
Authors: Mehrabadi Marmar , Aidun Cyrus K. , Ku David N.
Published: January 2014

When an arterial wall is injured, white clots form rapidly to prevent blood loss. In addition to hemostasis, under pathophysiological conditions, white clots can occlude atherosclerotic arteries. Such occlusive clots can cause ischemic cardiac arrest in less than an hour[1, 2]. Determining the predominant rate limiting processes governing thrombosis growth rate can guide us in identifying patients at increased risk of atherothrombosis.
Prediction of Interference Free Positions of the Humeral Implant in Preparation of Joint Replacement Procedures
Authors: Mostafavi Kamal , Tutunea-Fatan O. Remus , King Graham J. W. , Johnson James A.
Published: January 2014

Advanced simulation techniques in computer-assisted surgery is not only the key element towards development of computer based systems for optimized implant design, but they will also allow surgeons to reliably replace the damaged joints, even when significant bone loss has occurred. Since the main objective of the surgical procedure is to accurately replicate the native articulation of the elbow, the overall success of the joint arthroplasty is decisively influenced by the preoperative planning procedure aiming to establish the presence of a feasible position of the implant that will essentially cause a minimal malalignment of the prosthetic flexion-extension (FE) axis of the joint with respect to the native one. Any malalignment between native and artificial axes will eventually alter the kinematics of the joint and will lead to implant failures.
Whole Eye Model for Estimating Accommodation-Induced Strains in the Trabecular Meshwork
Authors: Reilly Matthew A. , Wilkes Robert
Published: January 2014

Recent work has shown that cyclic stresses from accommodation may induce changes in resistance to aqueous outflow through the trabecular meshwork. We developed a finite element model of the whole globe to examine changes in stress due to radial forces produced by the ciliary muscle. The mean equivalent stresses in the trabecular meshwork decreased significantly during accommodation.
Design of a Domestic Weighing Device for Wheelchair Users
Authors: Sherrod Brandon , Collins Jarrod , Johnson Austin , Haynes Josh , Eberhardt Alan , Feldman Dale
Published: January 2014

This design effort is the result of the capstone senior design project to create an affordable weighing device for wheelchair users. There are 3.3 million individuals in the Unites States that require a wheelchair for mobility aid. 1 Wheelchair use is associated with a number of health problems that are related to weight gain such as heart disease, diabetes, and stroke; however, few wheelchair users can afford currently available home-use wheelchair scales to monitor their weight. 2 Most wheelchair users must go to clinics, hospitals, or other healthcare facilities equipped with expensive wheelchair scales to monitor their weight. Previous studies have shown that consistent self-monitoring of weight is critical in preventing weight gain. 3 There exists a need for a way to measure wheelchair user weight in a home setting in an accurate manner that is user-friendly, portable, and affordable.
Generating Random Fiber Network Topologies That Mimic Previously Characterized Networks
Authors: Hadi Mohammad F. , Barocas Victor H.
Published: January 2014

Fibrous proteins, such as collagen and elastin, form the underlying structure of many soft tissues. These proteins form micrometer-scale networks of varying topology that play a role in governing the mechanics of tissues at larger length scales [1]. The relationship between a network’s topology and its mechanics, however, are poorly understood. This disconnect presents an important challenge in constructing realistic multiscale models of tissues informed by collagen network micrographs and subsequently reconstructed networks [2]. Accurate multiscale simulations may require thousands to millions of such unique networks. It is imperative that a method be developed to generate random networks that are functionally similar to ones derived experimentally. In the current study, we present a probabilistic method for generating de novo networks that mimic the mechanical properties of previously characterized networks. We chose Delaunay and Voronoi networks as model targets because they have been used successfully to model the mechanics of collagenous tissues [3] and since their topologies are well characterized. Understanding the role of topology in network mechanics is fundamental to building improved models of the mechanics of fibrous soft tissues — models that can aid in the rational design of engineered tissues or that can help assess the mechanical impact of damage or disease on native tissues.