bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite Element Analysis of a Close Head Axonal Injury Model: Relating Brain Tissue Biomechanics to Skull Deformation
Authors: Mao Haojie , Zhang Liying , Yang King H. , King Albert I. , Pál J’ozsef , Gallyas Ferenc
Published: March 2014

Biomechanical responses of a rat brain in a new weight-drop model were investigated by comparing histological results against finite element model predictions. This graded axonal injury rat model differed from others because of its utilization of intact skull without global angular motion to confound data analyses. Results demonstrated that the maximum principal strain and the compressive strain along the impact direction best correlated the experimentally observed injury locations while the shear strain did not have positive correlation.
Understanding Biological Structures Through Exploring the Mechanical Response of Cell-Like Systems
Authors: Zhang Ying , LeDuc Philip R.
Published: March 2014

The actin cytoskeleton provides mechanical support for the cell and influences activities such as cancer metastasis and chemotaxis. While their mechanical responses have been studied in vivo and in vitro, understanding the link between these two forms remains challenging. To explore this gap and further understand cell structure, we reconstructed the cell cytoskeleton in a membrane-like spherical liposome to mimic the cellular environment; this enables an artificial “cell like” system. Through this approach, we are pursuing a path to compare in vitro mechanics from a polymer physics perspective of individual actin filaments with the in vivo mechanics of a living cell [1]. A living cell contains many organelles, which are in a highly packed environment and require significant organization to function. The actin cytoskeleton provides both structural and organizational regulation that is essential for cellular response. Here, we first encapsulated G-actin into giant unilamellar vesicles through an electroformation technique and then polymerized them into actin filaments (F-actin) within individual vesicles. To probe their conformation, we visualized these vesicles with fluorescence and laser scanning confocal microscopy. We then used a tapping mode atomic force microscopy to determine the mechanical properties of these cell-like systems. These results provide insight into a wide range of fields and studies including polymer physics, cell biology, and biotechnology.
The Effects of the Inhibition of Connexin 43 on Pre-Osteoblasts and Their Response to Mechanical Stimulation
Authors: Joiner Danese M. , Daley Ethan L. H. , Goldstein Steven A.
Published: March 2014

It is well established that bone can adapt to the demands of daily mechanical usage. Mechanical loading can result in bone formation depending on the magnitude, duration, and frequency. Unloading, which can occur during bed rest, micro-gravity exposure and a variety of clinical conditions, can result in bone resorption. In vitro studies have demonstrated that osteoblasts and osteocytes respond to mechanical stimulation, especially oscillatory fluid shear stress. Mechano-responses have included increases in inter- and intra-cellular communication through gap junctions and soluble factors such as nitric oxide and prostaglandin E2 [1]. Bone cell gap junctions are primarily comprised of connexin 43 (Cx43). Mice lacking Cx43 have an osteopenic phenotype and when subjected to cyclic 4 pt. bending loads have an increased tibia bone marrow area [2, 3]. These observations may represent altered cell signaling. To investigate the role of Cx43 in cell signaling and bone mechanotransduction the Cx43 gene was silenced in MC3T3-E1 pre-osteoblast cells subjected to oscillatory fluid shear stress.
Portable Pneumatic Power-Harvesting Ankle-Foot-Orthosis
Authors: Chin Robin , Hsiao-Wecksler Elizabeth T. , Loth Eric , Alleyne Andrew , Manwaring Scott , Shorter K. Alex , Tyson Serena N. , Kogler Géza
Published: March 2014

In this paper, we present a novel ankle-foot-orthosis (AFO) design that controls ankle motion by providing a plantarflexion stop with free dorsiflexion during gait. The biomechanical controls are accomplished with a unique application of a cam-follower design that uses pneumatic power harvested via an air bellow embedded into the insole of the AFO (Figure 1). This portable design is self-contained and does not require any external power source to provide for the plantarflexion stop locking mechanism. It is the first step in a series of untethered fluid-powered orthotic devices.
Initial Investigation of Reduced Wall Shear Stress in the Pulmonary Arteries of Hypertension Patients Using Phase Contrast MRI
Authors: Barker Alex J. , Lanning Craig , Ivy Dunbar , Shandas Robin
Published: March 2014

A number of concomitant factors are thought to contribute to an increase in the mean pulmonary arterial pressure (MPAP) of pulmonary arterial hypertension (PAH) patients, such as increased pulmonary vascular resistance (PVR), increased blood flow (due to septal defects), and a decrease in wall distensibility.[1] This is in contrast to the normal pulmonary circuit, which is characterized by compliant artery walls and a low PVR, resulting in a low MPAP with little flow and pressure wave reflection. The influence of pathologic MPAP’s on proximal hemodynamic factors such as artery size, flow pulse waveforms, and wall shear stress (WSS) is unclear. Since these factors are known pathophysiological stimuli in the production of molecules that alter vascular tone and matrix properties,[2] we set out to quantify the geometry, flow, and WSS of the left, right and main pulmonary arteries (LPA, RPA, & MPA) of control and PAH patients using phase-contrast magnetic resonance imaging (PC-MRI).
Effect of Ageing on Elastin Functionality in Human Cerebral Arteries
Authors: Fonck E. , Feigl G. G. , Fasel J. , Sage D. , Unser M. , Rüfenacht D. A. , Stergiopulos N.
Published: March 2014

The ageing process affects elastin, a key component of the arterial wall integrity and functionality. Elastin may play an important role in cerebral vessels because elastin degradation is linked to cerebrovascular disease [1]. The goal of this study is to assess the biomechanical properties of human cerebral arteries, their composition and geometry, with particular focus on the functional alterations of elastin in cerebral arteries due to ageing.
Using Flow Waveform Approximations for Aortic Wave Reflection and Pulse Transit Time Assessment: A Critical Evaluation
Authors: Kips Jan G. , Rietzschel Ernst R. , De Buyzere Marc L. , Gillebert Thierry C. , Van Bortel Luc M. , Segers Patrick
Published: March 2014

The arterial blood pressure waveform can be considered as the composite of a forward pressure wave, travelling from the heart to the periphery, and of a reflected pressure wave, travelling backwards towards the heart. Early return of this reflected wave boosts systolic blood pressure, increasing the load on the heart and widening the amplitude of the pressure pulse, factors that have been shown to increase cardiovascular risk.
Subject Specific In-Vivo CFD Estimated Aortic WSS: Comparison Between Manual and Automated Segmentation Methods
Authors: Renner Johan , Gårdhagen Roland , Karlsson Matts
Published: March 2014

When making computational fluid dynamics (CFD) based estimations of wall shear stress (WSS) in the human aorta, medical image converting processes to 3D geometries are important as the result is strongly dependent on the quality of the geometry [1]. The image interpretation process or segmentation can be more or less automated; however in clinical work today the gold standard is to manually interpret the medical image information. This combined magnetic resonance imaging (MRI) and CFD method aims to estimate WSS in human arteries in-vivo as WSS is strongly linked to atherosclerosis [2]. More or less automated segmentation has been used in previous studies but normally based on a stack of 2D individually segmented slices which is combined into a 3D model [3]. The aim of this work is to compare manual 2D and automatic 3D segmentations.
FEM Voxel Modeling of the Tubular Embryonic Chick Heart for Finite Strain Analysis
Authors: Young Jonathan M. , Beecher Eric M. , Filas Benjamen A. , Taber Larry A. , Perucchio Renato
Published: March 2014

Significant progress has been made in the study of the developmental biomechanics of the embryonic chick heart through the use of the finite element method (FEM) [1, 2, 3]. Our work focuses on the geometry of the Hamburger-Hamilton stages 9–12 embryonic chick heart, approximately the time when the heart begins to function and undergoes drastic morphological changes, such as c-looping. Our objective is to devise a method for building an accurate 3D solid FEM mesh used for nonlinear analysis of the myocardium (MY) and cardiac jelly (CJ). The models are based on the extraction of voxels from optical coherence tomography (OCT) images of an arrested developing heart. To alleviate the problem of jagged edges introduced by the hexahedral voxel structure, we present a method for geometric smoothing and mesh coarsening. The performance of the voxel and smoothed models are tested given physiological loading conditions (pressure, biological growth, muscle contraction), to ascertain which model should be used for modeling the c-looping process.
Comparison of Outflow Condition Models on the Effect of Wall Shear Stress Distribution in Patient Specific Coronary Trees
Authors: van der Giessen Alina G. , Gijsen Frank J. H. , Wentzel Jolanda J. , Groen Harald C. , van der Steen Anton F. W. , van de Vosse Frans N.
Published: March 2014

It is well established that atherosclerosis originates in low wall shear stress (WSS) regions near bifurcations and in curved segments of the coronary tree [1]. WSS also seems to influences plaque progression and destabilization, which explains the large interest in accurate assessment of the WSS.
Mechanical Properties of the Porcine Coronary Artery
Authors: van den Broek Chantal N. , Rutten Marcel M. , van de Vosse Frans N.
Published: March 2014

Knowledge of mechanical properties of living arteries is important to understand vascular function during health, disease and intervention. A mechanical model of the vascular tree would facilitate the development of (balloon-)catheters and stents.
Real-Time Continuous Monitoring of Sub-Dermal Tissue Stresses Under the Ischial Tuberosities in Individuals With Spinal Cord Injury
Authors: Linder-Ganz Eran , Yizhar Ziva , Siev-Ner Itzhak , Gefen Amit
Published: March 2014

Individuals with a spinal cord injury (SCI) are susceptible to deep tissue injury (DTI) which is a pressure-related-necrosis that onsets in the gluteus muscles under the ischial tuberosities (IT). The condition may exacerbate to widespread tissue necrosis and sepsis [1], but early detection is currently not feasible because the injury starts and progresses under intact skin. In SCI patients, local elevated mechanical strains and stresses are formed around the IT, and are not relieved through motion [2]. The excessive tissue strains and stresses, combined with ischemia and hindered diffusion, induce and promote muscle cell death [3]. Recently, we developed a real-time, patient-specific finite element (FE) modeling method and experimental system with a clinical orientation of providing early detection of sub-dermal mechanical conditions that potentially lead to DTI. We presented this system and initial data from healthy adults during the 2006 Summer Bioengineering Conference [4]. Herein, we provide, for the first time, data from trials in an individual with SCI monitored by the system, which indicates that mechanical conditions in gluteus muscles of SCI patients are substantially distinct from those of control subjects.
Quantitation of Laminin Adsorbed Onto Polydimethylsiloxane Surfaces Using Various Treatment Protocols
Authors: Lee Hae-Jeong , Matos Marvi A. , Pakstis Lisa , Cicerone Marcus T. , Dunkers Joy P.
Published: March 2014

There is considerable interest in how cells respond to mechanical stimuli, from the ligands used to transmit the stimulus to the signaling pathways initiated and the proteins expressed upon phenotype change [1]. Previous work focused on the evaluation of the quality of the extracellular matrix (ECM) coating and cell proliferation [2]. Our focus is the characterization of a flexible polymeric substrate, treated with ECM, used to induce tensile strain on cells. In this work, we expand our physical characterization of the protein modified polydimethylsiloxane (PDMS) surface by quantifying the coverage of laminin on PDMS, plasma-treated PDMS, and PDMS treated with plasma and aminopropyltrimethoxysilane (APTMS) (Silane_70 protocol) using X-ray reflectivity.
Cervical Laminoplasty Construct Stability: A Finite Element Study
Authors: Tadepalli Srinivas C. , Kallemeyn Nicole A. , Shivanna Kiran H. , Smucker Joseph , Fredericks Douglas C. , Grosland Nicole M.
Published: March 2014

Cervical laminoplasty is one of many modern techniques utilized in the management of cervical myelopathy. In the United States cervical spondylotic myelopathy (CSM) has been classically treated with multilevel decompression and fusion. Furthermore, multi-level anterior cervical decompression and fusion (ACDF), via disectomies or corpectomies, and multi-level cervical laminectomy and fusion have been well described [1]. In the last decade cervical laminoplasty has grown in popularity as a non-fusion alternative that allows multi-level cervical decompression.
An Experimental Study of Transport Properties of Ceramic Membranes for Use in Hemodialysis
Authors: Huang Zhonping , Attaluri Anil C. , Belwalkar Amit , Van Geertruyden William , Gao Dayong , Misiolek Wojciech
Published: March 2014

Hemodialysis (HD) remains the primary treatment modality for the management of renal failure patients. Hemodialysis membranes play an important role in renal replacement therapy (RRT). HD is an extracorporeal blood clean process where the major mass transfer mechanism is diffusion. This therapy is mainly effectual for low molecular weight (LMW) solutes (such as urea and creatinine) removal or clearance for which diffusive mass transfer is a swift process. There is an increase in the removal of middle molecular weight (MMW) solutes (such as β2-microglobulin) when high flux membranes are available. Hemodiafiltration (HDF) is a treatment where the convective mass transfer accolades with diffusive mass transfer to increase the solute clearance efficacy, specifically for MMW solutes. The convective mass transfer is reliant on the amount of fluid exchanged. Toxin removal efficiency of HDF significantly depends on the porosity, pore size, pore distribution and surface area of the membrane [1, 2]. Although newly developed high flux polysulfone membranes have high MMW solute clearance, the non-uniform pore size and pore distribution is the main contributors to the albumin loss. Previous studies by Huang et al.[3], showed that nanoporous alumina sheet membranes have uniform pore size (∼ 10nm), high hydraulic permeability, uniform pore distribution and excellent pore structure with uniform channels. It was predicted that these membranes would have high molecular removal capacity. Therefore, in this study, experiments were performed to generate the data of intrinsic membrane properties such as hydraulic permeability, sieving coefficient and solute diffusive permeability for the alumina tubular membranes. Results were also compared to current polyethersulfone (PES) dialysis membranes.
Endoscope Shape-Tracker Based on Embedded Fluorescent Dyes in an Optical Fiber
Authors: Gavalis Robb M. , Xing Hua , Wong Peter Y. , Lilge Lothar , Cao Caroline G. L.
Published: March 2014

Endoscopes are used in medicine to inspect inside the body without having to perform open surgery on the patient. The current gold standard for screening and diagnosing colorectal cancer and inflammatory bowel disease is the colonoscopy. This procedure uses a flexible endoscope to inspect the wall of the large intestine, from the rectum to the caecum, for cancerous or precancerous lesions. This screening is very important since early detection of colon cancer is 85–95% successfully treated. Unfortunately, there is only a 30% compliance rate for colonoscopies in the United States. This lack of compliance is due largely in part to the uncomfortable nature of the procedure, caused by the fact that the stiff scope is difficult to manipulate in the non-rigid colon, leading to “looping” of the scope (see Fig. 1), and that the clinician is essentially navigating in near blind conditions during the procedure.
The Role of Stress Concentrations in the Bone Cement Mantle
Authors: Hoey David , Carette Didier , O’Reilly Peter , Taylor David
Published: March 2014

Acrylic bone cement is a porous biomaterial with many applications across both the medical and dental fields. In orthopaedics, it is used in the fixation of artificial implants where it forms a mechanical bond between the implant and the surrounding tissue. Bone cement is prepared during surgery by mixing a polymer powder and a liquid monomer. The mixture is then inserted into the body in a dough-like state, setting around the implant. Due to the manner in which the cement is prepared and inserted, the material tends to contain defects. Porosity arises in the cement due to trapped air and evaporation of the monomer during the mixing process. Larger defects of various shapes occur as a result of trapped debris, incomplete filling of the space, premature solidification and shrinkage: these are all similar to causes of defects in castings and injection-mouldings [1]. Even without these defects, stress concentrations can arise due to protrusion of bone into the cement as well as the geometry of the hip implant. High stresses can occur in the cement close to the femoral stem, the magnitudes of which are dependant of the cross-section of the stem and other design features [2].
Cryoinjury of a Contractile Tissue-Equivalent: In Vitro Experiments
Authors: Elkhalil H. , Bischof J. C. , Barocas V. H.
Published: March 2014

Cryosurgery, the minimally-invasive destruction of undesirable tissues by freezing, is an attractive technique for treating diseases where tight control over lesion size and minimal scar tissues are crucial, such as cancer and dermatologic disorders (1, 2). Unlike hyperthermic (high temperature) treatments, cryosurgery maintains the integrity of the extracellular matrix (ECM) while destroying the cells of the tissue. The undamaged ECM results in a unique wound healing process, which, compared to most injuries, leads to a better tissue recovery. Thus, cryosurgery has been of great interest in many clinical fields and has been studied extensively. However, numerous questions remain.
Lumbar Spine Loads in Low- and Moderate-Speed Rear-End Collisions
Authors: Fisher Jacob L. , Bove Robert T. , Moore Tara L. A.
Published: March 2014

Much attention has been given to the motions of and the forces and moments exerted upon the cervical spine during rear-end collisions, often in the interest of understanding so-called whiplash injuries in low-speed collisions and serious or fatal neck injuries in higher speed collisions. In contrast, lumbar spine loads are seldom recorded in rear-end collisions. For example, it has become common to place instrumented anthropomorphic test devices (ATDs) in vehicles during FMVSS 301 Fuel System Integrity rear-end impacts. Since the mid-1990s, upper neck loads have been measured during these tests, and, more recently, lower neck load data have been collected as well [1]. Lumbar spine loads, in contrast, are generally not recorded [1].
Effect of Rate of Blood Flow Through Large Blood Vessels on HIFU Temperature Rise
Authors: Dasgupta Subhashish , Hariharan Prasanna , Myers Matthew R. , Banerjee Rupak K.
Published: March 2014

High Intensity Focused Ultrasound (HIFU) shows considerable promise as a minimally-invasive technique for tumor ablation. A typical HIFU procedure involves focusing of acoustic energy in a small region, with the absorbed acoustic energy causing localized rise in tissue temperature. Temperature rise of the order of 40–60°C is achieved within seconds, causing immediate cell necrosis in the targeted region.
Accuracy and Precision of a Control System for an Elbow Joint Simulator
Authors: Schimoler Patrick J. , Vipperman Jeffrey S. , Kuxhaus Laurel , Budny Daniel D. , Flamm Angela M. , Baratz Mark E. , Miller Mark Carl
Published: March 2014

Joint motion simulators (JMS’s) have been developed for many applications enabling the repeatable testing of prostheses, scientific investigations of joint mechanics and the study of surgical procedures.[1–4] Although Morrey has reported that radial head implants have lower post-operative satisfaction than other joint implants[5] and Dunning has examined several issues with radial heads, many problems remain.[6] It is therefore beneficial to develop a simulator capable of evaluating radial head implants. A robust simulator can also provide the ability to test soft tissue strains at the elbow and compare control schemes that may elucidate the body’s means of controlling multiaxial multimuscle systems.
New Method for the Determination of the Diffusion Tensor of Solutes in Tissues by FRAP Technique
Authors: Travascio Francesco , Gu Weiyong
Published: March 2014

Diffusion is an important transport mechanism for nutrition supply into avascular cartilaginous tissues, such as intervertebral disc [1].
Noninvasive Measurement of Brachial Wall Mechanics During Flow-Mediated Vasodilation Using 2D Ultrasound Strain Tensor Imaging
Authors: Mahmoud Ahmed M. , Stapleton Phoebe A. , Frisbee Jefferson C. , Mukdadi Osama M.
Published: March 2014

Atherosclerosis has become one of the contributing factors of cardiovascular diseases. Endothelial dysfunction is considered a key factor in the development of atherosclerosis [1]. Flow-mediated vasodilatation (FMD) measurement in brachial and other conduit arteries has become a common method to asses the endothelial function in vivo [2]. Fluid shear-stress increases due to blood flow increases, thus stimulating endothelial cell production and release of nitric oxide, a potent endogenous vasodilator. The mechanical behavior of the arterial wall during vasodilatation is considered an indication for endothelial health. In FMD measurement, the endothelium-dependent variation in arterial diameter in response to reactive ischemia-induced hyperemia is measured by comparing the luminal diameter of the brachial artery before and after the ischemia of the forearm induced by pressurizing a cuff [3]. Ultrasound imaging modalities has been widely used in the FMD analysis as a noninvasive low-cost tool, which can be used to track the arterial diameter change with time. Most of the FMD measurements in the literature are based on tracing the vessel wall boundary manually. Since this process is time consuming and may introduce human errors, automatic measurement techniques have been implemented [3,4]. These techniques utilize image processing algorithms to identify the edges of arterial walls, and then calculate the relative displacement change with time.
Using Injury Tolerance Data to Reconstruct Accidents
Authors: Moore Tara L. A. , Bove Robert T.
Published: March 2014

In order to determine what occurred in an injury-producing event, such as a motor vehicle accident or a fall, it is essential to understand both the environment in which the event occurs and the specifics of the injuries. Information about the environment can then be used as part of the biomechanical analysis to determine how the person moves, what structures they may have contacted and the severity of any contacts, which can then be used to determine the expected injuries. Another approach is to begin with the injury specifics, determine what type of mechanical loading is necessary to cause that injury, and finally assess what environmental factors would lead to that loading.
Vasculogenic Potential of Porcine Endothelial Colony Forming Cells
Authors: Lan Sheeny K. , Prater Daniel N. , Jamison Russell D. , Ingram David A. , Yoder Mervin C. , Wagoner Johnson Amy J.
Published: March 2014

The natural healing process cannot restore form and function to critical size bone defects without the presence of a graft to support and guide tissue regeneration [1]. Critical size bone defects in humans are typically on the order of centimeters or larger [2]. Thus, a major limitation of synthetic grafts or bone tissue engineering constructs is the lack of vascularization to support cell viability after placement in vivo [3]. Cells that participate in bone regeneration, must reside within 150–200 microns of a blood supply in order to gain proper nutrients and to eliminate waste [4]. Consequently, a tissue engineering construct of a clinically relevant size cannot rely on diffusion for transport of nutrients and waste. Previous research has shown that blood vessels can infiltrate scaffolds, but the overall process is too slow to prevent death of cells located in the center of a construct [5].
Metabolite Transport Inside Channeled Porous Scaffolds for Haematopoietic Stem Cell Culture: A Computational Study
Authors: Cantini Marco , Fiore Gianfranco B. , Redaelli Alberto , Soncini Monica
Published: March 2014

Porous polymeric materials play a key role in regenerative medicine, serving as three-dimensional scaffolds for cell culture. Hence, the definition of their micro-architecture should be regarded as a pivotal design issue, that has to be wittingly addressed while engineering a cell culture system. Computational fluid dynamics techniques (CFD) appear to be very valuable in this respect, since they have been appreciably applied in recent literature as a means to analyze fluid dynamics and mass transport inside scaffold or bioreactor models [1]; moreover, leading researchers in tissue engineering have acknowledged the role of numerical methodology in the issue of defining optimal flow conditions for three-dimensional dynamic culture systems.
Fluid Flow and Particle Dispersion in Acini During Asynchronous Ventilation
Authors: Chhabra Sudhaker , Prasad Ajay K.
Published: March 2014

The human lung comprises 24 generations of dichotomously branching tubes known as bronchi [1]. Functionally, these generations can be categorized as: (1) conducting airways which are non-alveolated and comprise the first 16 generations, and (2) the acini which consist of flexible, alveolated airways and are responsible for gas exchange. The alveoli are the most important units of the human respiratory system and provide large surface area (about 70–80 m2) for efficient gas exchange; oxygen diffuses into the blood through the alveolar epithelium, whereas carbon dioxide diffuses in the opposite direction from the blood to the lung.
Role of Membrane and Cortex Mechanics in Microrheology Measurements and Flow-Induced Cell Injury
Authors: Dailey Hannah L. , Ricles Laura M. , Ghadiali Samir N.
Published: March 2014

Certain serious illnesses, including pneumonia and the acute respiratory distress syndrome (ARDS), can lead to fluid accumulation in the lung and obstruction of the small pulmonary airways. Fluid in the lungs inhibits gas exchange and patients may require mechanical ventilation, which can expose the lung to mechanical stresses that exacerbate the existing injury and result in additional fluid accumulation. Recent improvements in ventilation protocols (e.g. low lung volume ventilation) have improved ARDS treatment, but mortality rates remain high (30–40%).
The Mechanism of Pulse Pressure Affecting the Permeability of Arteries
Authors: Yao Qingping , Hayman Danika M. , Dai Qiuxia , Lindsey Merry L. , Han Hai-Chao
Published: March 2014

Arteries are subjected to a pulsatile pressure centered on a constant mean pressure in vivo. This oscillating pressure may increase due to atherosclerotic and age-related wall stiffening, or may be disrupted by the use of cardiopulmonary bypass machines and ventricular assist devices. Previous research has reported that restoration of pulsatile flow improves microcirculation and blood flow to the organs, however little is known about how pulsatile pressure affects the vasculature.
Effects of Anatomical Frame Definitions on Repeatability of Knee Joint Translation Measurement During Walking
Authors: Gao Bo , Abdelhalim Hussein , Zheng Naiquan (Nigel)
Published: March 2014

Human body movement analysis using stereophotogrammetry has been widely applied in understanding the normal function and pathological conditions of human knee joint. To reconstruct the 3-dimensional (3D) position and orientation of bones from markers placed on body surface, the spatial relationship between anatomical frames and skin marker clusters needs to be identified [1]. Since the determination of anatomical landmark (AL) locations in general lacks accuracy and precision, anatomical frames defined based on ALs are subject to uncertainty. This is a major issue in human movement analysis and its effects on knee rotation kinematics determination have been studied [1]. However, few studies have investigated the effects of uncertainty of anatomical definition on translation measurement of knee join. Although knee translations are secondary motions with only small magnitudes, they are regarded with great clinical significance. On the other hand, translation measurement is more sensitive to definitions of origin positions in addition to axis directions of the anatomical frames. In this work, we studied the effects of three different anatomical frame definitions (neutral standing, prediction method and functional method) on knee joint translation measurement during level walking. The repeatability of translation measurement among three sessions was compared among the three anatomical definition methods.
Modeling the Finite Deformation Anisotropic Viscoelastic Behavior of the Cornea
Authors: Nguyen Thao D. , Jones Reese E. , Boyce Brad L.
Published: March 2014

This paper presents the development of a finite element model for the cornea as a first step towards a physiologically based model to study the role of cornea and sclera biomechanics in glaucoma. We developed a finite-deformation anisotropic constitutive model of the cornea that considers the effects of the fibrilar microstructure on the viscoelastic stress response. The model was base on the hypothesis that the dominant mechanism for the tensile viscoelastic behavior of the cornea is the viscoelastic stretching of the collagen lamellae. This approach yielded two main results. First, the viscoelastic properties of the cornea are derivable directly from the viscoelastic properties of the collagen fibrils and proteoglycan matrix. Second, the anisotropy in the stress response and creep response are determined solely by the arrangement collagen lamellae, which depends on orientation and material position. This allows the model parameters that determines anisotropy to be obtained from microstructural characterizations, such as the X-ray diffraction experiments of Meek and coworkers [1], while the model parameters that determines viscoelasticity to be determined from mechanical experiments. For this initial work, the viscoelastic parameters were fitted to the uniaxial tensile strip tests [2] and inflation tests with digital image correlation (DIC) [3] of bovine cornea performed by our group. Since microstructural characterizations are not available for bovine cornea, we used the data of Aghamohammadzadeh et. al. [1] for the human cornea.
In Vivo Contrast-Enhanced MR Imaging for Direct Infusion Into Rat Peripheral Nerve
Authors: Chen Xiaoming , Astary Garrett W. , Mareci Thomas H. , Sarntinoranont Malisa
Published: March 2014

Direct infusion of therapeutic agents into the spinal cord provides a promising way to treat traumatic injury and intrinsic diseases of the spinal cord, which may cause paralysis and other neurological deficits. Direct infusion into the spinal cord involves complex invasive surgery since the spinal cord is well protected by the vertebral bone. Instead, infusion directly into peripheral nerves is of interest since it provides a remote delivery site to the spinal cord, requiring less invasive surgery and reducing the risk of spinal cord injury during surgery. It may also allow targeting of specific neurons at nerve root entry. Previous studies have shown [1, 2] that transport in peripheral nerves is anisotropic with a preferred direction parallel to the fiber tracts. A large-scale longitudinal spread of molecular agents may be obtained and spread of molecular agents into the spinal cord may be possible.
Functional Mobility Testing: A Novel Method To Establish Human-System Interface Design Requirements
Authors: England Scott A. , Benson Elizabeth A. , Rajulu Sudhakar
Published: March 2014

Across all fields of human-system interface design it is vital to posses a sound methodology dictating the constraints on the system based on the capabilities of the human user. These limitations may be based on strength, mobility, dexterity, cognitive ability, etc. and combinations thereof. Data collected in an isolated environment to determine, for example, maximal strength or maximal range of motion would indeed be adequate for establishing not-to-exceed type design limitations, however these restraints on the system may be excessive over what is basally needed. Resources may potentially be saved by having a technique to determine the minimum measurements a system must accommodate.
Intervertebral Disc Function Is Restored in an In Vivo Model of Chronic Nucleus Pulposus Glycosaminoglycan Reduction
Authors: Boxberger John I. , Auerbach Joshua D. , Sen Sounok , Dodge George R. , Elliott Dawn M.
Published: March 2014

Reduced nucleus pulposus glycosaminoglycan (GAG) content is one of the earliest clinically detectable changes during the course of intervertebral disc degeneration [1,2]. Depletion of nucleus GAG by small percentages consistent with this early loss has been experimentally linked to altered motion segment mechanical function, and thus, potentially increases the risk of damage accumulation directly due to elevated stresses and strains and through altered cellular function [3]. Recently, our laboratory has established an in vivo model in a rat lumbar disc which moderately decreases nucleus GAG to levels observed in early human degeneration. In this model, GAG loss is accompanied by a state of hypermobility at both 4 and 12 weeks post treatment [4], potentially making the disc susceptible to mechanical failure. The objective of this study was to determine the long term effects of nucleus GAG depletion and to determine if altered discs demonstrate hallmark features of disc degeneration. We hypothesized that GAG will remain depleted 24 weeks post treatment, potentially decreasing to lower levels, and further that geometrical and mechanical changes consistent with degeneration will be observed.
Enhancing Cell Migration in Collagen Gels by Modulating Collagen Adhesivity
Authors: Monteiro Gary A. , Sundararaghavan Harini G. , Fernandes Anthony V. , Shreiber David I.
Published: March 2014

The organized movement of cells is critical during tissue morphogenesis and wound healing. While different tissue cells use distinct mechanisms for migration, the underlying biophysical balance of adhesive and tractional forces for effective migration is similar. The extracellular matrix provides the structural framework through which a cell can migrate. In particular, collagen is an abundant and ubiquitous ECM protein that supports cell migration. The excellent biocompatibility and physiological relevance of collagen have made it a primary material for tissue engineered regenerative therapies and in vitro studies with tissue equivalents.
Specimen-Specific Verification of Predicted TKR Mechanics During Simulated Deep Flexion Loading Conditions
Authors: Baldwin Mark A. , Clary Chadd W. , Maletsky Lorin P. , Rullkoetter Paul J.
Published: March 2014

Verified computational models of total knee replacement serve as the primary design-phase tool for parametric analysis of implant geometry. Previously, dynamic finite element models of the Kansas Knee Simulator (KKS) were developed and tibiofemoral (TF) and patellofemoral (PF) kinematic predictions were verified by comparison with experimental measurements [1,2]. In this prior work, the implants were mounted in metallic fixtures to assess the ability of the model to accurately predict the TF and PF kinematics without the additional complexity of variable cadaver specimens and soft-tissue constraint. The next step in the systematic model verification procedure was to verify kinematic predictions with multiple specimen-specific models. Specifically, the objectives of the present study were: 1) to develop an explicit finite element (FE) model of the KKS capable of recreating experimental loading protocols for a deep knee bend activity and 2) to verify predicted six degree-of-freedom (DOF) TF and PF kinematics of two cruciate retaining (CR) and two posterior stabilized (PS) implanted specimen-specific models with deformable, wrapping soft tissue constraint.
Development of a Multiple Indicator Dilution Technique Using Fluorescent Dyes to Measure Cardiac Capillary Permeability
Authors: McGoron Anthony J. , Fernandez-Fernandez Alicia
Published: March 2014

Anthracyclines are widely-used drugs for the treatment of cancer. Although these drugs are effective in reducing or containing tumor progress, their long-term use is limited by toxicity effects. A special area of concern is related to the toxic effects that these drugs have on the myocardial tissue, including interstitial edema, fibrosis, degeneration of myocardial cells, and cardiac dilatation, among others. The end result is an overall impairment in cardiac function that limits the use of these agents [1,2]. This damage in heart function can be life-threatening, and it causes special concern in patients with prior cardiac dysfunction, as well as in children [2]. As a result of these disadvantages, there is a trend in current research to develop anthracycline derivatives or modified formulations with reduced cardiotoxic effects, as well as to learn more of the mechanisms that mediate this cardiac toxicity. Our long-term goal is to measure changes in capillary endothelium permeability in the heart after administration of anthracyclines which may contribute to the overall deterioration in function observed after chronic treatment with this medication. The goal of this project was to develop a sensitive, non-radioactive technique to measure capillary permeability in experimental animal models. This technique could then be applied in future studies of anthracycline cardiotoxicity.
Experimental Determination of Osteon Permeability
Authors: Gailani Gaffar , Cardoso Luis , Cowin Stephen
Published: March 2014

Measurement of a permeability of a single osteon is still one of the most demanding tasks in bone mechanics to be solved. The challenges are the size of the osteon and the limitations or absence of the tools that can take a direct measurement. Determining the permeability in an osteon may help to best understand the fluid flow occurring in cortical bone and its role in mechanotransduction. In this communication, both analytical and experimental approaches are proposed to estimate the permeability of a single osteon. The Young modulus and Poisson’s ratio of the bone matrix and the osteon under undrained conditions will be determined using acoustic microscopy and mechanical testing. Based on the unconfined compression test results, the permeability of the osteon can be obtained by curve fitting of the data of the compressive ramp loading to the transverse isotropic osteon analytical model that we developed in Gailani and Cowin [1].
Stereoscopic PIV of Steady Flow Through a Bileaflet Mechanical Heart Valve
Authors: Hutchison C. , Sullivan P. E. , Ethier C. R.
Published: March 2014

Each year over 180,000 mechanical heart valves are implanted worldwide, with the bileaflet mechanical heart valve (BiMHV) accounting for approximately 85% of all valve replacements [1,2]. Although much improved from previous valve designs, aortic BiMHV design is far from ideal, and serious complications such as thromboembolism and hemolysis often result. Hemolysis and platelet activation are thought to be caused by turbulent Reynolds shear stresses in the flow [1]. Numerous previous studies have examined aortic BiMHV flow using LDA and two component Particle Image Velocimetry (PIV), and have shown the flow to be complex and three-dimensional [3,4]. Stereoscopic PIV (SPIV) can obtain all three velocity components on a flow plane, and hence has the potential to provide better understanding of three dimensional flow characteristics. The objective of the current study was to use SPIV to measure steady flow, including turbulence properties, downstream of a BiMHV in a modeled aorta. The resulting dataset will be useful for CFD model validation, and the intent is to make it publicly available.
A Clinical Approach to Multi-Joint EMG-Driven Modelling
Authors: Bassett Daniel N. , Buchanan Thomas S. , Cerulli Giuliano
Published: March 2014

Most muscles span more than one joint. This can lead to problematic questions when making biomechanical models. How many joints need to be included in an accurate model? Do all joints that each muscle crosses need to be taken into account? If so, how many joints away from the joint of interest must be included, since they are all interconnected?
In Vivo MRI-Based Estimation of Time-Dependent Elastic Modulus in Healthy Arteries
Authors: Taviani Valentina , Li Zhi-Yong , Young Victoria , Sutcliffe Michael P. F. , Wong Pauline , Graves Martin J. , Gillard Jonathan H.
Published: March 2014

The elastic properties of the arterial wall have been the subject of physiological, clinical and biomedical research for many years. There is convincing evidence that the elastic properties of the large arteries are seriously impaired in the presence of cardiovascular disease (CVD), due to alterations in the intrinsic structural and functional characteristics of vessels [1]. Early detection of changes in the elastic modulus of arteries would provide a powerful tool for both monitoring patients at high cardiovascular risk and testing the effects of pharmaceuticals aimed at stabilizing existing plaques by stiffening them or lowering the lipids.
Escherichea coli Biofilm Formation and Susceptibility in Response to Increased Shear Stresses
Authors: Kostenko Victoria , Salek M. Mehdi , Boraey Mohammad A. , Surette Michael G. , Martinuzzi Robert J.
Published: March 2014

The development of biofilms, well organized communities of bacterial cells embedded in a self-generated extra-cellular polymeric matrix, on medical devices (vascular or urinary catheters, surgical implants) and surrounding tissue poses a great challenge for modern medicine. The biofilm environment confers onto bacterial cells resistance to antimicrobials and the host immune system that leads to persistent and recurrent device-associated infections, deterioration of patient life quality, and often replacement of the device [1].
A Multi-Axis Programmable Spine Robot: Application Towards Kinematic Assessments of the Lumbar MSU
Authors: Kelly Brian P. , Zufelt Nephi A. , Sander Elizabeth J. , DiAngelo Denis J.
Published: March 2014

Current in vitro testing methodologies remain limited in the ability to explore spinal dynamics. The gold standard of flexibility testing has traditionally focused on evaluating MSU rotational ranges of motion only. While such data may be applied towards evaluation of the Instantaneous Axis of Rotation (IAR), many systems lack the needed sensitivity. The result is that there is currently no consensus on the location of the IAR. Further, very limited data or insight can be gathered as to the precise kinematic or dynamic state of the MSU, or the influence of surgically implanted motion restoration devices. For example, total disc arthroplasty devices are typically rigid mechanical devices that impose an IAR or IAR range. How might this imposed IAR affect MSU mechanics? How might variations in surgical placement of an implant be scientifically quantified? More recently an emerging group of compliant motion restoration devices are being developed that require new methods of evaluation. How well does a compliant device restore the native mechanics of the disc or MSU? To address and understand these increasingly important issues, novel, more advanced biomechanical testing protocols need to be developed.
Development of a Finite Element Model of a Pediatric Pelvis and Material Property Estimation
Authors: Kim Jong-Eun , Li Zuoping , Ito Yasushi , Huber Christina D. , Shih Alan M. , Soni Bharat K. , Yang King H. , Eberhardt Alan W.
Published: March 2014

The pediatric pelvis is vulnerable to injuries in motor vehicle collisions, sport activities, and fall accidents. Pelvic fractures and injury mechanisms in children differ substantially from those found in adults [1]. While the injury mechanisms and tolerances of the adult pelvis have been fairly well characterized through cadaveric experiments and computational models, efforts related to the pediatric pelvis have been limited due to difficulties in acquiring and testing pediatric cadavers. The objective of this study was to develop a finite element (FE) model of a 10-year-old (10YO) human pelvis to provide more comprehensive understanding of injury mechanisms experienced by children.
An Automated Image-Based Method of 3D Subject Specific Body Segment Parameter Estimation
Authors: Sheets Alison L. , Corazza Stefano , Andriacchi Thomas
Published: March 2014

Recent studies have suggested that limb kinetics during swing or float phase movements are important for ACL injury analysis and injury prevention [1]. Kinetic (moment and force) calculations during swing phase can be sensitive to the accuracy of subject-specific body segment parameters (BSP) including mass and inertial properties. While numerous methods for estimating BSP have been implemented including regression equations [2,3], geometric body shape estimations, medical imaging and optimization approaches, they all have application specific limitations. Almost all of these BSP estimation approaches are limited by assumptions that: the mass center (CM) lies on the axis connecting the segment’s proximal and distal joint center, the body principle moments of inertia are aligned with the segment axes [4], and the right and left limbs are symmetric. These assumptions could introduce errors in 3D kinematic analysis. Non-invasive methods of measuring the exact geometry and volume of body segments have the potential to reduce most sources of error.
Effect of Processing Parameters on the Microstructure and Mechanical Behaviour of Nano Bioceramic
Authors: Liu Xueran , El-Ghannam Ahmed R.
Published: March 2014

Silica-calcium phosphate nanocomposite (SCPC) has a superior bone regenerative capacity and resorbability when compared to hydroxyapatie (HA) and bioactive glass [1–2]. Synthesis of SCPC bioceramics with superior mechanical properties has been an important and challenging issue. Ideally, the mechanical strength of the orthopedic implantat should be comparable to that of the host-bone in order to provide structural support and minimize stress shielding. The compressive strength of trabecular bone ranges from 2–12 MPa and that of cortical bone varies in the range of 100–230 MPa [3]. The aim of the present study is to study the effect of processing parameters on the mechanical properties of SCPC cylinders prepared by powder metallurgy technique. The mechanical properties were correlated to the microstructure of SCPC prepared under different processing conditions.
Finite Element Analysis of S1 Fracture Following Anterior Lumbar Interbody Fusion With Concomitant Bilateral Spondylolysis
Authors: Pfeiffer Ferris M. , Abernathie Dennis L. , Miles John D. , Parker Jeffery W.
Published: March 2014

Instability of the lumbar spine is a significant cause of pain and loss of function in the human population. There are a multitude of causes for a reduction or complete loss of stability of the lumbar spine. These causes include but are not limited to degenerative disc disease, spondylolysis, spondylolisthesis, genetic and growth abnormalities, and ligament laxity. Regardless of the cause, instability of the spine often leads to discomfort and loss of function. When conservative options have been exhausted, the surgeon in consultation with the patient may opt for surgical treatment of the unstable segment.