bluuebunny/crossref_metadata_2025 huggingface dataset:
A Framework for Finite Element Mesh Quality Improvement and Visualization in Orthopaedic Biomechanics
Authors: Shivanna Kiran H. , Tadepalli Srinivas C. , Magnotta Vincent A. , Grosland Nicole M.
Published: July 2013

The finite element method (FEM) is an invaluable tool in the numerical simulation of biological processes. FEM entails discretization of the structure of interest into elements. This discretization process is termed finite element meshing. The validity of the solution obtained is highly dependent on the quality of the mesh used. Mesh quality can decrease with increased complexity of the structure of interest, as is often evident when meshing biologic structures. This necessitated the development/implementation of generalized mesh quality improvement algorithms.
Modeling Viscoelastic Wall Properties of Ovine Arteries
Authors: Valdez-Jasso Daniela , Haider Mansoor A. , Campbell Stephen L. , Bia Daniel , Zocalo Yanina , Armentano Ricardo L. , Olufsen Mette S.
Published: July 2013

Generation of a complete map of arterial wall mechanical properties can improve treatment of cardiovascular diseases via contributions to design of patient specific vascular substitutes used to alleviate atherosclerosis and stenoses, which are predominant in arterial pathways (i.e., abdominal aorta, carotids, or femoral arteries). Clinically useful estimation of arterial properties from patient data requires both efficient algorithms and models that are both complex enough to capture clinically important properties and simple enough to allow rapid computation. In this study, we used mechanical models accounting for both elastic and viscoelastic wall deformation to analyze how vessel properties and associated model parameters vary with artery type. It is known that for the aorta wall, deformation is dominated by nonlinear elastic dynamics, while for the smaller vessels (e.g. the carotid artery) deformation is dominated by viscoelastic responses. The latter is correlated with composition of the vessels; the aorta contains significantly less smooth muscle cells (∼40%) than the carotid artery (∼60%), and has significantly more elastin (see Fig 1).
Use of a Central Pattern Generator for Control of a Muscle-Actuated Simulation of Pedaling
Authors: Schultze Martin , Thelen Darryl G.
Published: July 2013

Muscle actuated forward dynamic simulations have provided tremendous insights into the mechanics of locomotion. However, the controllers used for large scale simulations have often been open-loop, with the muscle excitations prescribed as a function of time [1]. Due to the inherently unstable nature of bipedal movement, this means that perturbation-type analyses are often limited to short time frames after the perturbation is introduced [2]. However for many clinical problems, it would be desirable to predict how periodic locomotion reestablishes following a change to the system or perturbation from the environment.
MRI-Based Measurement of Carotid Mechanical Properties in Asymptomatic Patients
Authors: Li Zhi-Yong , Gillard Jonathan H.
Published: July 2013

Arterial mechanical property may be a potential variable for risk stratification. Large artery and central arterial compliance have been shown not only to correlate well with overall cardiovascular outcome in large epidemiological studies [1, 2] but also to correlate with coronary atherosclerotic burden as measured by conventional angiography [3]. Until recently, real-time B-mode ultrasound combined with simultaneous blood pressure measurements have been used to assess large artery compliance [4]. These techniques have an excellent temporal resolution but are unable to provide adequate spatial resolution to determine changes in vessel area as opposed to diameter and make the assumption that the vessel is perfectly round. Attempts to use MR imaging to measure large artery compliance have been published previously [5]. However, they have not utilised simultaneous blood pressure measurements during sequence acquisition. We report a technique using regular and simultaneous blood pressure measurement during 2 dimensional phase contrast magnetic resonance imaging 2DPC-MRI to determine local carotid compliance.
Excessive Shear Force at the Digits May Contribute to Unstable Grip Following Stroke
Authors: Seo Na Jin , Kamper Derek G.
Published: July 2013

Stroke is a leading cause of long-term disability in the United States and the third most frequent cause of death, following diseases of the heart and cancer [1]. Of the more than 700,000 Americans who experience a stroke each year [1], two-thirds survive [2]. Currently there are more than five million stroke survivors in the U.S. [1], many of whom have long-term motor and sensory impairments, especially in the arm and hand [3]. Studies report that 69% of patients who were admitted to a rehabilitation unit following stroke have mild to severe upper extremity dysfunction [4], and only 14% to 16% of stroke survivors with initial upper extremity hemiparesis regained near-complete motor function [3,4]. Chronic deficits following stroke are especially prevalent in the hand and therefore diminish the capacity to grasp [5]. Hand grasp has great functional importance for performing activities of daily living. The impairment in grasping significantly lowers stroke survivors’ functional independence.
Quantification of Cortical Surface Convolution in the Developing Ferret and Human Infant
Authors: Knutsen Andrew K. , Hill Jason E. , Neil Jeffrey J. , Inder Terrie E. , Bayly Philip V.
Published: July 2013

The human cerebral cortex undergoes folding from the 5th fetal month into the first post-natal year. Disturbances of folding have serious and lasting consequences, but the mechanism is not well understood. Van Essen [1] has hypothesized that axonal tension between strongly interconnected regions draws them together and induces outward folds. However, no direct measurements have confirmed this theory. As measures of shape, cortical curvature and sulcal depth changes during development can help provide insight into underlying mechanisms of growth.
Gender Bias in Pelvic Fractures: A Geometrical and Structural Assessment
Authors: Roan Esra , Janda Haden A. , Elenes Egleide Y. , Marinescu Ruxandra C.
Published: July 2013

Pelvic fractures are complex, devastating fractures in musculoskeletal trauma that account for approximately 3% of all skeletal injuries, and unfortunately, still constitute a major cause of death and disability [1, 2]. Approximately 64% of all pelvic fractures are due to motor vehicle crashes (MVC). Rowe et al. (2004) identified female gender as a significant risk factor for pelvic ring fractures resulting from MVC. Women are three times more likely than males to have a pelvic fracture due to MVC [3, 4, 5]. Body mass index (BMI) and height differences have not been recognized as risk factors and it is presumed that a possible cause of increased fracture susceptibility in women could be the geometric differences between female and male pelvises [3]. Furthermore, according to Army Medical Research, female recruits have a higher incidence of pelvis (pubis) fractures due to overuse injuries than their male counterparts [3–7].
A Novel Bioreactor for Continuous Monitoring of Force-Displacement
Authors: Lasher Richard A. , Parikh Monir K. , Hitchcock Robert W.
Published: July 2013

Current bioreactors, although suitable for various functions, are often times costly, unreliable and difficult to set up [1,2]. Unlike standard tissue culture equipment, these systems are complex and difficult to operate [1,2]. Due to these limitations our aim was to develop a bioreactor that utilizes common cell culture equipment, is easy to set up and can interrogate mechanical properties of engineered tissue in culture. Additionally, a small footprint and the ability to grow tissue in replicate were desired due to space limitations of standard laboratory incubators. The end goal of this study was to develop a reliable, robust and reproducible bioreactor capable of continuously monitoring force-displacement characteristics.
Effect of Anulus Fibrosus Repair on Lumbar Spine Biomechanics
Authors: Kode S. , Gudipally M. , Takigawa T. , Espinoza Orías A. A. , Natarajan R. , An H. S. , Andersson G. B. J. , Griffith S. L. , Inoue N.
Published: July 2013

Low back pain is sometimes related to, but not necessarily caused by, anulus fibrosus (AF) ruptures. Studies on low back pain have estimated an annual incidence of 5% and prevalence of 15% to 20% in United States alone [1]. Disc degeneration with or without herniation is frequently implicated in low back pain and sciatica, and is believed to be associated with segmental instability of the spine [2].
A Computational and Experimental Investigation Into Biomechanics of Lumbar Spine Stabilized With a Novel Posterior Dynamic Stabilization System
Authors: Kiapour Ali , Goel Vijay K. , Krishna Manoj , Koruprolu Sarath , Parikh Rachit , Mahtre Devdatt
Published: July 2013

Lumbar spinal stenosis is a progressive degenerative condition due to arthritic facet joints. Arthritic facets become inflamed and often develop osteophytes, leading to nerve compression and persistent severe back pain. When conservative treatment fails to reduce pain, surgical management may be pursued to improve the patient’s quality of life. Spinal decompression and fusion is one of the most common surgical procedures for treatment of spinal stenosis. However, fusion may result in accelerated degeneration of the adjacent motion segments and morbidity [1]. Motion preservation instrumentation is being developed to preserve motion at the involved and adjacent segments, as opposed to fusion procedure [2]. In this study, we used experimental and finite element (FE) techniques to assess and compare the biomechanics of intact spines and spines implanted with a novel posterior dynamic stabilizer device (TrueDyn™, Disc Motion Technologies, Boca Raton, FL). The effects on the adjacent segment, including motion and intra-discal pressure were analyzed.
Imaging Sarcomeres of Extensor Carpi Radialis Brevis in Humans Using Minimally Invasive Microendoscopy
Authors: Cromie Melinda J. , Sanchez Gabriel N. , Schnitzer Mark J. , Delp Scott L.
Published: July 2013

Sarcomeres are the smallest contractile elements of muscle. Muscle generates force when overlapping myosin and actin filaments within the sarcomere interact to generate force. The amount of force these interactions generate depends on sarcomere length. The range of sarcomere lengths over which a muscle normally operates in the body is an important factor in analyzing a muscle’s force generating capacity. Measurement of sarcomere lengths in vivo is limited by their small size (2–4 μm) and the inability to use fluorescent dyes in humans. We recently developed a microendoscopy system to image sarcomeres in humans via Second Harmonic Generation (SHG) [1]. Here we demonstrate the use of this microendoscopy system as a robust, minimally-invasive tool for biomechanical analysis by measuring sarcomere lengths of the forearm muscle extensor carpi radialis brevis (ECRB) in 5 human subjects.
Subpixel Texture Correlation for Contractile Behaviors of Engineered Cardiac Tissue
Authors: Wan Leo Q. , Zhang Ting , Marsano Anna , Maidhof Robert , Vunjak-Novakovic Gordana
Published: July 2013

Tissue engineering of cardiac patches has offered a great potential to provide replacement for damaged or diseased myocardium, especially with recent progress in cardiovascular differentiation of embryonic stem cells [1] and dynamic culture of cardiac constructs with electrical field and perfusion [2, 3]. Spontaneous beating is one of most important characteristics of cardiac tissue, and contractile responses under electrical field are often treated as ‘golden standard’ for evaluating engineered cardiac patches. Therefore, it is necessary to accurately measure their contractile behaviors. However, till now, in most of previous studies, the observation of cardiac contraction has been relied on naked eyes, and functional assessments of those constructs have therefore been difficult and very time-consuming.
A Computational Model of Direct Infusion Into the Rat Brain: Corpus Callosum and Hippocampus
Authors: Kim Jung Hwan , Astary Garrett W. , Mareci Thomas H. , Sarntinoranont Malisa
Published: July 2013

Despite the high therapeutic potential of many macromolecular drugs, it has proven difficult to apply them to treatment of cancer and other degenerative diseases of the central nervous system (CNS) due to low capillary permeability and low diffusivity. To overcome these barriers, recent experimental studies have shown local infusion, i.e., convection-enhanced delivery (CED), to be a promising delivery technique in the brain and spinal cord [1–3]. Predictive models of extracellular fluid flow and transport during CED would be useful for treatment optimization and planning.
A Simulator for the In Vitro Study of the Dynamics of the Aortic Valve: Design and Test
Authors: Vismara Riccardo , Comparolo Dario , Mangini Andrea , Antona Carlo , Fiore Gianfranco B.
Published: July 2013

The in vitro approach to the study of the hemodynamics of heart valves allows easier-to-control and well repeatable experimental conditions, if compared with studies on animal models. A deep, detailed insight into specific issues is possible, despite the unavoidable simplification of the physiological complexity.
Measurement of Valve Lesion Morphology and Aorta / Flow-Jet Patterns in Bicuspid Aortic Valve Patients
Authors: Barker Alex J. , Lanning Craig , Shandas Robin
Published: July 2013

Bicuspid aortic valve (BAV) patients are identified by a lesion of the tricuspid aortic leaflets in which only two ‘functional’ leaflets are visibly present. This lesion occurs in 0.5–2% of the population and is accompanied by a significant incidence of morbidity and mortality related to aortic valve dysfunction, aortic dilatation, aortic aneurysm, and aortic dissection. [1] The pathogenesis of the malformation has been postulated to be the result of a congenital or inflammatorily-mediated fusion of two of the three aortic leaflets. In addition, BAV is accompanied by a variety of heterogeneous complications and is considered a complex disease with many cofactors, the importance of which continue to be debated. Among these cofactors, the most commonly identified vascular manifestation is aortic dilatation. [1] There are two hypotheses for this manifestation: the first postulates the coexistence of BAV and genetically-based aortic fragility; the second proposes that BAV morphology and incomplete valve opening induces hemodynamic forces that influence structure and function at the aorta.
Force at Damage and Failure Decreases With Age in the Human Cadaveric Facet Capsular Ligament During Tension
Authors: Craig Kiersten M. , Quinn Kyle P. , Winkelstein Beth A.
Published: July 2013

Epidemiologic reports indicate that over 5 million nonfatal accidents occur annually, with painful injuries being the most common type of injury [1]. The cervical facet joint and its capsule are a common source of pain in these injuries [2]. Biomechanical tolerances of the cervical spine in compression, cervical motion segments in tension, and isolated spinal ligaments have all been reported to vary with age [3, 4]. Although microstructural damage has been shown to occur in the facet capsular ligament well-before the gross failure of that tissue and also has been speculated to relate to painful damage in that ligament [5], there is currently no study investigating ligament damage during tensile loading as function of age.
Changes in Tibiofemoral Joint Space Following Total Knee Arthroplasty During Weight-Bearing Knee Motion
Authors: Varadarajan Kartik M. , Moynihan Angela L. , Seon Jong Keun , Freiberg Andrew A. , Rubash Harry E. , Li Guoan
Published: July 2013

Increasing the range of knee flexion following total knee arthroplasty (TKA) remains an important objective for design of new implants and advancement of surgical techniques. With the excellent long term (10–15 year) outcome of TKA, surgeons are more confident about performing the procedure on younger, more active patients demanding increased range of knee flexion [1–3]. Numerous factors have been linked to limited flexion (<120°) following TKA, including patient factors such as preoperative range of motion, intraoperative factors such as component malposition, and implant design [1–3]. Extensor mechanism overstretching due to overstuffing of the knee joint is hypothesized to be a contributing factor limiting knee flexion [1–4]. However, no study to date has investigated the changes in tibiofemoral joint space following TKA. The aim of this study was to examine pre- and post-operative tibiofemoral joint space in a group of TKA patients during weight-bearing knee flexion and to compare it to that in the normal/healthy knee. This could help determine if changes in the proximal-distal distance between the femur and the tibia (tibiofemoral joint space) could lead to extensor mechanism overstretching and consequently limited range of flexion.
Numerical Simulation of Ultrasonic Color Blood Flow Imaging in the Carotid Artery: Comparing a 1st Order and Fully Coupled Approach
Authors: Swillens Abigail , Løvstakken Lasse , De Schryver Thomas , Torp Hans , Segers Patrick
Published: July 2013

Ultrasonic imaging is widely applied for visualization of blood flow using different imaging modalities. However, due to the inherent physical limitations of the ultrasonic imaging process, the actual flow dynamics and the information embedded in the ultrasound image do not necessarily strictly correspond. Computational fluid dynamics (CFD) can play an important role in interpreting and improving ultrasound imaging via numerical simulation of ultrasound images. For this purpose, CFD velocity data can be directly processed to mimic ultrasonic images (1st order approach) or can be further coupled to ultrasound simulation software, providing a fully coupled approach. We compared both methods for the clinically relevant case of color flow imaging of the carotid artery. We conclude that for this application, the 1st order approach leads to results lacking indispensable properties of the imaging process, i.e., (i) the imaging dynamics, and (ii) the statistical properties of the ultrasonic velocity estimator.
Influence of Loading Conditions and the Superficial Tangential Zone in Contact Models of Articular Surfaces
Authors: Owen John R. , Wayne Jennifer S.
Published: July 2013

Engineering tissue to repair articular surface defects remains a challenge. Normal zonal characteristics of articular cartilage throughout its thickness, particularly the superficial tangential zone (STZ), and normal material properties have not been reproduced in vitro in scaffolds nor in vivo in repairing defects. Without sufficient quality, such transplanted scaffolds in vivo may be doomed mechanically from the outset. The importance of the STZ in normal function [1–3] and deficient behavior of repair tissue [4–5] is well documented in the literature. Studies have modeled higher tensile properties in the STZ via transverse isotropy [6–9] or tension-compression nonlinearity [10] to better predict experimental results. Models incorporating an STZ with strain-dependent permeability [11–13] have indicated protection of underlying repairs. Permeable and impermeable rigid contact models [12] have been thought to bracket in vivo conditions. Recent efforts have been to create more complex models to better represent in vivo conditions [13]. This finite element study compares permeable and impermeable rigid contact models with a more realistic model to determine if the added complexity is warranted.
Inter-Operator Segmentation Differences Impact Wall Shear Stress Distributions in Patient-Specific Computational Fluid Dynamic Models
Authors: Campbell Ian C. , Sprague William W. , Piccinelli Marina , Veneziani Alessandro , Oshinski John N.
Published: July 2013

The link between hemodynamic forces, notably wall shear stress (WSS), and atherogenesis is well established. Patient-specific computational fluid dynamics (CFD) modeling of human vasculature has attracted recent attention because it allows investigators to determine areas at risk for plaque formation and subsequent rupture [1]. Non-invasive in vivo imaging methods such as magnetic resonance (MR) angiography allow acquisition of vascular geometry and cross-sectional velocity such that a CFD model can determine the spatial distribution of WSS. WSS may then be correlated with phenomena such as wall thickening.
Effects of Blood Rheology on Flow Topology and Blood-Vessel Interaction in Image-Based Carotid Bifurcation Numerical Model
Authors: Massai Diana , Ponzini Raffaele , Gallo Diego , Antiga Luca , Passoni Giuseppe , Montevecchi Franco Maria , Redaelli Alberto , Morbiducci Umberto
Published: July 2013

In recent years, interest is growing on compact measures for assessing the role of local hemodynamics in the pathogenesis of atherosclerosis and atherogenesis. CFD and its power in evaluating and predicting the effect of some hemodynamic variables in vascular disease is becoming a key factor in clinical research. Recently, Lee and Steinman [1] assessed the importance of blood rheology assumptions to ascertain the effect of constitutive relation for blood on local wall shear stress (WSS) and on the correlated vascular pathology. We present a preliminary in silico investigation on the sensitivity of helical flow measure with respect to the blood constitutive adopted model. Our main objective was to verify if, through the carotid bifurcation model, the rheological properties of blood significantly influence the bulk flow topology, whose evolution and stability are strictly linked to helicity. In fact helicity — an invariant in fluid dynamics — has been demonstrated to describe and reveal the global organization in a fluid flow. For this purpose several blood models (Newtonian and non-Newtonian) were implemented. A specific Lagrangian-based “bulk” flow descriptor, the Helical Flow Index (HFI) [2], was calculated in order to get a “measure” of the helical structure in the blood flow. Therefore, its sensitivity to blood rheology and hematocrit (Ht) was assessed and compared with the sensitivity of WSS based on other fluid dynamics descriptors (Time Averaged WSS, TAWSS, and Oscillating Shear Index, OSI).
Aneurysms of the Posterior Communicating Artery: Hemodynamics and Shapes
Authors: Khvostova Svetlana , Putman Christopher , Cebral Juan R.
Published: July 2013

The pathogenesis, progression and rupture of cerebral aneurysms are multi-factorial mechanisms that involve arterial hemodynamics, wall biomechanics, wall mechano-transduction or mechano-biology, and peri-aneurysmal environmental effects [1]. However, the interaction and relative importance of these factors remains poorly understood. Presumably, the geometrical shape and evolution of aneurysms are governed by the interaction between hemodynamic stimuli (wall shear stress) and the biological responses of the arterial wall. In order to better understand this interaction, the goal of this study was to characterize and relate the geometrical shapes of intracranial aneurysms at a single location, the posterior communicating artery (PComA), to blood flow patterns, wall shear stress (WSS), and clinical history of previous rupture.
Bone Marrow Adipogenesis Is Affected by Insulin-Like Growth Factor-1 Complexes
Authors: Fritton J. Christopher , Kawashima Yuki , Sun Hui , Wu Yingjie , Mejia Wilson , Courtland Hayden W. , Rosen Clifford J. , Yakar Shoshana
Published: July 2013

Fat tissue, which is composed of lipid-filled adipocytes that accumulate during aging, displaces mineralized tissue and reduces the mechanical integrity bone. Bone marrow adipocytes provide stroma for maintenance of mesencymal stem cells (MSC) and reside at sites of bone turnover (i.e., endosteal surfaces where osteoblasts form new bone), potentially influencing cell activity via a paracrine route.
A Numerical Multiscale Study of the Haemodynamics in an Image-Based Model of Human Carotid Artery Bifurcation
Authors: Gallo Diego , Ponzini Raffaele , Consolo Filippo , Massai Diana , Antiga Luca , Montevecchi Franco M. , Redaelli Alberto , Morbiducci Umberto
Published: July 2013

The initiation and progression of vessel wall pathologies have been linked to disturbances of blood flow and altered wall shear stress. The development of computational techniques in fluid dynamics, together with the increasing performances of hardware and software allow to routinely solve problems on a virtual environment, helping to understand the role of biomechanics factors in the healthy and diseased cardiovascular system and to reveal the interplay of biology and local fluid dynamics nearly intractable in the past, opening to detailed investigation of parameters affecting disease progression. One of the major difficulties encountered when wishing to model accurately the cardiovascular system is that the flow dynamics of the blood in a specific vascular district is strictly related to the global systemic dynamics. The multiscale modelling approach for the description of blood flow into vessels consists in coupling a detailed model of the district of interest in the framework of a synthetic description of the surrounding areas of the vascular net [1]. In the present work, we aim at evaluating the effect of boundary conditions on wall shear stress (WSS) related vessel wall indexes and on bulk flow topology inside a carotid bifurcation. To do it, we coupled an image-based 3D model of carotid bifurcation (local computational domain), with a lumped parameters (0D) model (global domain) which allows for physiological mimicking of the haemodynamics at the boundaries of the 3D carotid bifurcation model here investigated. Two WSS based blood-vessel wall interaction descriptors, the Time Averaged WSS (TAWSS), and the Oscillating Shear Index (OSI) were considered. A specific Lagrangian-based “bulk” blood flow descriptor, the Helical Flow Index (HFI) [2], was calculated in order to get a “measure” of the helical structure in the blood flow. In a first analysis the effects of the coupled 0D models on the 3D model are evaluated. The results obtained from the multiscale simulation are compared with the results of simulations performed using the same 3D model, but imposing a flow rate at internal carotid (ICA) outlet section equal to the maximum (60%) and the minimum (50%) flow division obtained out from ICA in the multiscale model simulation (the presence of the coupled 0D model gives variable internal/external flow division ratio during the cardiac cycle), and a stress free condition on the external carotid (ECA).
Skin Burns: Numerical Model Study of Radio Frequency Current Sources
Authors: Pearce John A. , Valvano Jonathan W.
Published: July 2013

Skin burns from radio frequency (RF) current remain an important clinical consideration. The classical studies on the kinetics of skin burns in the 1940s and 1950s [1–4] continue to be the most often cited and utilized framework for their prediction and analysis. The objective of this study was to apply numerical models to more thoroughly analyze previously-described experimental skin burns created by RF current under disk electrodes [5].
TRID Cranial Analysis During Rear Impact Simulation With MADYMO
Authors: Meyer Andrew , Fritz Jessica M. , Harris Gerald F.
Published: July 2013

Early studies of cranial kinematics were primarily limited to sagittal plane assessments of motion secondary to impact in volunteers, models, anthropometric dummies and human specimens [1]. With advances in instrumentation and imaging technology, more relevant studies of three dimensional (3-D) motion began to emerge. More complex 3-D head kinematics were first quantified with arrays of precisely positioned multi-axis accelerometers [1]. This evolution in quantitative ability has continued to the present time with the application of high speed motion capture systems and more sophisticated mathematical models.
Neural Network-Based Gait Adaptation Algorithms for Lower Limbs Active Orthoses
Authors: Gomes Marciel A. , Siqueira Adriano A. G. , Silveira Guilherme L. M.
Published: July 2013

This work deals with neural network-based gait-pattern adaptation algorithm for an active orthosis. The proposed device is developed for lower limbs and based on a commercially available orthosis, Figure 1. Active orthoses can be designed for helping physically weak or injured people during rehabilitation procedures [1]. The robotic orthosis Lokomat is being recently used for rehabilitation of patients with stroke or spinal cord injury individuals [2]. Gait-pattern adaptation algorithms are proposed by Riener, et. al [3], considering the human-machine interaction. The algorithms in Riener, et. al [3] were developed for a fixed base robotic system; they can not be applied directly in the proposed orthosis, since no stability of the gait pattern is considered. A trajectory generator for biped robots taking into account the ZMP (Zero Moment Point) criterion is presented in Huang, et al. [4]. This method presents suitable results with smooth and second-order differentiable curves.
Computational and Experimental Analysis of Calcium Triphosphate Reinforced Three Part Fracture Fixation
Authors: Feerick Emer , Kennedy Jim , Mullet Hannan , McGarry Patrick , FitzPatrick David
Published: July 2013

Complex three part proximal humerus fractures in osteoporotic patients are a particularly challenging injury to manage as the associated bone loss reduces the efficacy of standard fixation techniques. Locking plates are commonly used for three part fracture fixation. However, a clinical study conducted by Owsley et al [1] reports complications with 57% of patients over 60 years of age. In cases of severe bone loss an intramedullary (IM) bone graft implant can be used in conjunction with locking plates to improve fixation and to provide structural stability. The limited and variable availability of bone grafts mean high cost and variable material properties.
Simulation of Blood Flow in Deformable Arteries Using Subject-Specific Geometry and Variable Vessel Wall Properties
Authors: Xiong Guanglei , Figueroa C. Alberto , Xiao Nan , Taylor Charles A.
Published: July 2013

Previous efforts to simulate blood flow in patient-specific models either assumed rigid vessel walls or deformable walls with constant mechanical property [1]. We have developed a new workflow to enable blood flow and vessel dynamics simulations using subject-specific geometry and variable wall properties. The geometric model construction is based on 3D segmentation and geometric processing which greatly reduce human labor and increase the objectivity of the model. Variable wall properties are assigned to the model based on combining centerline-based and surface-based methods. This new approach was successfully applied to simulate blood flow and wall dynamics in models with abdominal, thoracic, and cerebral aneurysms.
Removal of Sulfated Glycosaminoglycans Has a Differential Effect on Permeability of Bovine Articular Cartilage as Measured by Direct Permeation and Stress Relaxation
Authors: Henninger Heath B. , Underwood Clayton J. , Ateshian Gerard A. , Weiss Jeffrey A.
Published: July 2013

Permeability is defined as the ability of a fluid to pass through a porous medium. The ease of water movement is a determinant of the interstitial fluid flow-dependent viscoelastic properties of hydrated soft tissues and also modulates transport of solutes. For articular cartilage, permeability has been quantified directly via permeation experiments and indirectly by analyzing the data from stress relaxation testing under confined compression. It is unclear whether these different methods result in consistent measurements. This further complicates quantification of the effect of an experimental treatment on permeability such as the removal of sulfated glycosaminoglycans (GAGs) [1, 2]. The objective of this study was to elucidate the impact of sulfated GAGs on the permeability of articular cartilage using direct permeation versus stress relaxation testing, and to assess any differences in permeability calculated from the two test methods.
Theoretical Evaluation of a Simple Cooling Pad Inducing Hypothermia in the Spinal Cord Following Traumatic Injury
Authors: Smith Katisha D. , Zhu Liang
Published: July 2013

Although significant damage is caused by the mechanics of the traumatic spinal cord injury (SCI), secondary injury that follows is often times even more dangerous. It occurs within the first 12–24 hours following the injury and can last up to 5–10 days, depending on the severity of the injury [1]. Secondary injury causes physiological disturbances that disrupt the body’s homeostasis like initiating a cellular inflammatory response at the injury site and increasing the release of free radicals. An overabundance of free radicals contributes to tissue ischemia, cerebral edema, and disruption of the spine-blood barrier. The use of hypothermia (<35°C) as a therapeutic agent has been shown effective in providing neuroprotection from secondary injury [2]. Research has shown the benefits of hypothermia include decreasing oxygen consumption, free radical generation, neurotransmitter release, inflammation, and metabolic demands [3–5]. Even a temperature decrease of 1–2°C can be beneficial at the cellular level [4,6]. However, these studies use techniques that can be invasive. This research evaluates the effectiveness of using a non-invasive cooling pad on the torso to reduce the spinal cord temperature by at least 2°C.
Steady Streaming in the Liquefied Vitreous Due to Saccadic Eye Movements
Authors: Stocchino Alessandro , Repetto Rodolfo , Siggers Jennifer H.
Published: July 2013

The posterior chamber of the eye has an approximately spherical shape, and is filled with vitreous humor, a transparent material with viscoelastic properties [1]. The vitreous has the mechanical roles of supporting the eye shape, promoting the adherence between the retina and the choroid, and acting as a barrier between the anterior and posterior segments of the eye that inhibits both heat diffusion and molecular transport [2]. Sometimes, particularly in elderly people, the fluid in the posterior chamber has almost Newtonian properties. This can be as a consequence of liquefaction of the vitreous humor due to synchisys (degradation of the collagenous framework of the vitreous humor), or after a vitrectomy, a surgical procedure in which the vitreous humor is replaced by tamponade fluids (typically silicone oils). Since intra-vitreal drug injection is increasingly used to treat retinal diseases, and the efficacy of this procedure depends on molecular transport processes following injection, much of the biomechanical research on the vitreous humor has focused on understanding these processes. Many authors have considered purely diffusive transport or alternatively purely advective transport due to creeping bulk flow [3,4]. However, when the vitreous is liquefied, rotational motion of the eye is also likely to induce significant fluid flow.
A New Computational Tool for Voice Analysis Based on FFT, Wavelet Transform, and Spectrogram
Authors: de Almeida Nathalee C. , Barros Jannayna D. , Soares Heliana B. , Bresolin Adriano de A. , Guerreiro Ana Maria G. , Brandao Glaucio B.
Published: July 2013

Digital signal processing techniques have been used by acoustic analysis to evaluate the voice quality of the patient, due to the simplicity and non-invasive procedures for measurements.
Chemically Defined Medium With TGF-β3 Enhances Matrix Elaboration by Nucleus Pulposus Cells Encapsulated in Novel Photocrosslinked Carboxymethylcellulose Hydrogels
Authors: Reza Anna T. , Nicoll Steven B.
Published: July 2013

Back pain is a significant clinical concern often attributed to degeneration of the intervertebral disc (IVD) and the associated dehydration of the nucleus pulposus (NP) [1]. The NP is a gel-like tissue at the center of the disc, rich in proteoglycans and type II collagen that functions to resist compressive forces through the generation of a hydrostatic swelling pressure [2]. Tissue engineering strategies may provide a viable NP replacement therapy as an alternative to current surgical procedures. However, several factors including medium formulation and scaffold selection can affect construct maturation [3]. For example, transforming growth factor-beta 3 (TGF-β3) has been shown to enhance the functional properties of tissue engineered cartilage constructs, with more pronounced results observed in serum-free conditions [3]. NP cells are commonly cultured in ionically crosslinked alginate hydrogels to maintain their phenotypic properties; however, these scaffolds have been shown to lose structural integrity over time, creating a need for an alternative biomaterial [4]. Therefore, the objective of this study was to examine the effects of medium formulation on NP cells encapsulated in novel photocrosslinked carboxymethylcellulose (CMC) hydrogels.
Adenylyl Cyclase 6 Mediates Primary Cilia-Dependent Changes in Cyclic Adenosine Monophosphate in Response to Dynamic Fluid Flow
Authors: Temiyasathit Sara , Kwon Ronald Y. , Tummala Padmaja , Quah Clarence C. , Jacobs Christopher R.
Published: July 2013

It is well accepted that fluid flow is an important mechanical signal in regulating bone structure and function. Primary cilia, which are solitary, microtubule-based organelles that extend from the centrosome into extracellular space in many cell types, have been shown to mediate fluid flow-induced osteogenic responses in MLO-Y4 osteocyte-like cells [1], however, primary cilia did not mediate increases in intracellular Ca2+ concentration [1]. Recently, we identified cAMP as a novel early signaling molecule in primary cilia-dependent mechanotransduction of fluid flow in osteocytes. Specifically, we show that MLO-Y4 osteocyte-like cells respond to oscillatory flow with a rapid decrease in intracellular levels of cAMP that is dependent on the primary cilium [2]. Adenylyl cyclase 6 (AC6) is an enzyme responsible for the synthesis of cAMP from ATP. We found that AC 6 localizes to the primary cilium of bone cells (Fig. 1). In this study, our goal was to determine whether AC6 mediates the primary cilia-dependent, flow-induced decrease in cAMP.
Mechanical Response of Rat Cortical Neurons: AFM Indentations and Preliminary Modeling
Authors: Bernick Kristin , Prévost Thibault , Socrate Simona , Suresh Subra
Published: July 2013

Traumatic brain injury (TBI) due to blast exposure is becoming increasingly prevalent in soldiers returning from war and some consider TBI to be the signature wound of the Iraq and Afghanistan conflicts [1]. Common causes are exposure to explosions of improvised explosive devices (IEDs), rocket-propelled grenades, and landmines. A study by Hoge et al found that of 2525 soldiers, 4.9% reported injuries with loss of consciousness and an additional 10.3% reported injuries with altered mental status [2]. Despite the prevalence of TBI, little is known on the epidemiology of mild TBI and on its long-term health consequences. An improved understanding of the damage mechanism and injury progression will be critical for designing better protective gear and selecting appropriate treatments.
Discrete Stress Analysis on Point-Cloud Model Derived From Medical Images
Authors: Lu Jia , Qian Jing
Published: July 2013

Pixel or voxel data from the medical images provide a point-cloud depiction for complicated anatomies that are difficult to describe in CAD geometry. Traditionally, a point-cloud model needs to be converted into finite element mesh in order to perform mechanical analysis. Although meshing generation tools have been significantly improved over the last decades, generating high quality meshes in complicated bodies remains a challenge. Recently, the authors developed a family of solid mechanics solvers that work directly on domains represented by point-clouds [1,2]. Using this method, it is possible to conduct mechanical analysis on point-cloud representations of patient-specific organs without resorting to finite element method. In this article, we describe this paradigm of analysis and demonstrate the method with numerical examples.
Fast Computation of Blood Flows in Arterial Models
Authors: Mut Fernando , Löhner Rainald , Cebral Juan
Published: July 2013

The computation of the blood flow in arterial models requires the solution of the incompressible Navier-Stokes equations [1,2]. The geometry of these models is characterized by complex branching tubular domains. The main challenge with this kind of geometries is that the convergence rate of the pressure Poisson solver is dominated by the graph depth of the computational grid. The purpose of this paper is to present a novel technique (deflated conjugate gradients algorithm) for accelerating the solution of the pressure Poisson equation that is especially suited for elongated domains.
Dynamic Mechanical Signals Delivered by Ultrasound Generate Site Specific Mediation of Bone Loss
Authors: Ferreri Suzanne , Qin Yi-Xian
Published: July 2013

Osteoporosis is a disease characterized by decreased bone mass and progressive erosion of the microstructure. As a result, bone is at higher risk for developing chronic and traumatic fractures at key skeletal sites. Therapeutic ultrasound may offer a potential non-pharmacologic, site-specific intervention for treatment of osteoporotic bone loss.
An Evaluation of the Accuracy of Computer Assisted Surgery in Preoperatively Three Dimensionally Planned Periacetabular Osteotomies
Authors: Abraham Christine , Rodriguez John , Buckley Jenni , Burch Shane , Diab Mohammad
Published: July 2013

Adults with unresolved developmental dysplasia of the hip (DDH) often warrant Pelvic Periacetabular Osteotomy (PAO). Making the correct osteotomies, and then finding the “ideal” position of the acetabular fragment is difficult, even for the experienced surgeon. Due to its 3-D nature, need for precision, and limited direct visualization of the surgical site, the PAO procedure is a good candidate for Computer Assisted Surgery (CAS). Using CAS, a virtual image is created, which is then used to navigate through the procedure in real time. Improved imaging hardware, along with intra-operative navigation systems have the potential to reduce complication rates, and lessen the learning curve in the inexperienced surgeon. PAO cuts have been made using intra-operative navigation and acetabular fragments have been positioned in pre-operative computer models. As of yet, modeled PAO cuts have not been used to navigate intraoperative cuts. Furthermore, modeled acetabular positioning has not been combined with intra-operative navigation to position fragments. The aim of this study is to prove the utility of pre-operative 3D imaging, PAO osteotomy planning and acetabular fragment positioning with computer software. These modeled images can be used to complete highly accurate and effective PAO surgeries.
Tribological Properties of Hip Implant From Atomic Force Microscopy
Authors: Duong CongTruyen , Chang JunDong , Lee SangSoo , Park Seonghun
Published: July 2013

Mechanical and tribological properties of engineering and biological materials have been investigated at micro-scale levels from Atomic Force Microscopy (AFM) [1]. Regarding the tribological properties of engineering and biological materials such as the diamond-like carbon (DLC) film [2], the TiN film [3], and the surface of middle finger [4], the significant effect of their surface roughness on the frictional coefficient has been reported. However, the contradictory result that the relationship between the surface roughness and frictional behavior of the self-assembled monolayer (SAM), the silicon ruler, and the metal evaporated (ME) tape [5] is not significant has also been reported. Therefore, the main goal of this study is to investigate the relationships between the surface roughness, the frictional coefficient, and the hardness for both the main wear and the least habitual wear regions of the cobalt-chromium metal head of the hip implant from their measurements using AFM and Hardness Testing Machine. With the additional wear measurements of the metal head, the result of this study can help to understand how the micro-scale surface structure of the metal head affects its wear.
Thermal Environmental Effect on Breast Tumor Growth
Authors: Ma Na , Liu Ping , Chen Chao , Zhang Aili , Xu Lisa X.
Published: July 2013

Tissue hypoxia is a common and important feature of rapidly growing malignant tumors and their metastases. Tumor cells mainly depend on energy production thru anaerobic glycolysis rather than aerobic oxidative phosphorylation in mitochondria [1]. Intervening the tumor metabolic process via thermal energy infusion is worthy attempting. And hyperthermia, mildly elevated local temperature above the body temperature, is one of such kind. Previously, after being heated for a short period of time, tumor glucose and lactate level increased and ATP level decreased, which suggested energy metabolism was modified following hyperthermia through increased ATP hydrolysis, intensified glycolysis and impaired oxidative phosphorylation [2]. Many researchers designed experiments to determine thermal dose in hyperthermia [3], but few focused on the relationship between tumor and energy, especially for a long-term local hyperthermia treatment. One clinical trial indicated the effective long-term hyperthermo-therapy for maintaining performance status, symptomatic improvement, and prolongation of survival time in patients with peritoneal dissemination [4].
Blood Flow Dynamic and Fluid-Structure Interaction in Patient-Specific Circle of Willis
Authors: Yuan Qi , Chen Zhen , Zhu Guangyu
Published: July 2013

Over 50% stroke is related to the cerebral artery stenosis. The most common position is in the Circle of Willis (CoW), which is composed of a single anterior communicating artery (ACoA), paired anterior cerebral arteries (ACA), paired middle cerebral arteries (MCA), internal carotid arteries (ICA), posterior communicating arteries (PCoA) and posterior cerebral arteries (PCA). Detailed knowledge of the cerebral hemodynamics is important for a variety of clinical applications [1]. There has been a significant body of research performed on blood flow in the CoW [1,2] treating the cerebral vasculature as a 2D structure. To obtain more accurate hemodynamic results, 3D models should be considered. Studies have been performed on 3D models of the CoW generated from magnetic resonance imaging (MRI) data [3,4]. However, those 3D models neglected the effects of fluid-structure interaction (FSI) between the vessel wall and blood. In this paper, a patient-specific model of CoW from CT scan data was reconstructed and FLUENT 6.1 was used to simulate the blood flow in the CoW. On a special part of CoW, a 3D FSI model for the arteries was introduced to investigate both flow and structure behaviors, as well as their interaction by ADINA 8.3.