bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Excessive Subtalar Inversion/Eversion on the Dynamic Function of the Soleus and Gastrocnemius During the Stance Phase
Authors: Wang Ruoli , Gutierrez-Farewik Elena M.
Published: July 2013

Gastrocnemius and soleus are often considered as ankle plantarflexors. Their dynamic functions in normal and pathological gait have been well-studied. However, in a neutral position, the tendon passes medial to the subtalar joint axis and therefore produces an inversion moment in addition to the plantar-flexor moment [1]. It was believed that gastrocnemius and soleus are the major dynamic stabilizers preventing excess foot pronation. During normal gait, the subtalar joint experiences rapid eversion following heel strike and subsequent inversion during terminal stance [2]. Varus and valgus foot positions caused by excessive subtalar inversion/eversion can be found in spastic and flaccid paralysis [3]. Although it is widely understood that muscle forces can have important local and remote effects on joints and segments [4], the interrelations between dynamic gastrocnemius and soleus functions and excessive subtalar inversion/eversion remain unclear.
Identifying Candidate Mechanoregulators of Skeletal Development
Authors: Nowlan Niamh C. , Prendergast Patrick J. , Tajbakhsh Shahragim , Murphy Paula
Published: July 2013

Studying the relationship between mechanical forces and skeletal development can provide vital clues to the mechanoregulation of skeletogenesis, providing important information to tissue engineers hoping to create functional cartilage or bone in vitro. Many studies of the mechanoregulation of skeletal development have focused on the chick embryo e.g., [1, 2]. However, as no endochondral ossification takes place in the embryonic chick long bones [1], mammalian systems must be used to examine the effect of mechanical forces on endochondral bone formation. Mouse mutant strains exist in which muscle development is affected, providing models with which to examine skeletogenesis in the absence of skeletal muscle contractions. One such strain is Pax3sp/sp [3], also known as splotch. The splotch mutant lacks the transcription factor Pax3, which prevents the migration of muscle pre-cursor cells into the limb buds, resulting in a complete absence of skeletal muscle.
Contribution of Superior Mesenteric Vein Flow to the Right and Left Lobes of the Liver Using CFD
Authors: George Stephanie M. , Martin Diego R. , Giddens Don P.
Published: July 2013

The incidence of cirrhosis, the end stage for many liver diseases, is rising and with it the need for better understanding of the progression of the disease and diagnostic techniques. The authors have noted that liver disease occurs preferentially in the right side of the liver which is the largest lobe. One hypothesis is that this is due to the composition of the blood that supplies the right lobe. The liver is fed by both the hepatic artery and the portal vein with the portal vein contributing about 80% of the blood supply. The portal vein (PV) is supplied by the superior mesenteric vein (SMV), which drains blood from the digestive track, and the splenic vein (SV), which drains blood from the spleen. Since the blood in the SMV is coming from the digestive track, it carries toxins and items absorbed during digestion. Toxins such as alcohol are known to damage the liver. Thus, our hypothesis is that the majority of the SMV flow feeds into the right portal vein and ultimately the right lobe of the liver. This study seeks to assess the validity of our hypothesis in four subjects by creating subject specific models in two normal subjects and two patients and using computational fluid dynamics (CFD) to calculate the SMV contribution to the right portal vein.
A Simplified Strain Energy Function to Represent the Mechanical Behavior of the Annulus Fibrosus
Authors: García Jose J. , Puttlitz Christian
Published: July 2013

Models to represent the mechanical behavior of the annulus fibrosus are important tools to understand the biomechanics of the spine. Many hyperelastic constitutive equations have been proposed to simulate the mechanical behavior of the annulus that incorporate the anisotropic nature of the tissue. Recent approaches [1,2] have included terms into the energy function which take into account fiber-fiber and fiber-matrix interactions, leading to complex functions that cannot be readily implemented into commercial finite element codes for an efficient simulation of nonlinear realistic models of the spine (which are generally composed of 100,000+ degrees of freedom). An effort is undertaken here to test the capability of a relatively simple strain energy function [3] for the description of the annulus fibrosus. This function has already been shown to successfully represent the mechanical behavior of the arterial tissue and can be readily implemented into existing finite element codes.
Changes in Pulse Pressure Alter Arterial Wall Permeability
Authors: Hayman Danika M. , Yao Qingping , Gireud Monica B. , Dai Qiuxia , Lindsey Merry L. , Han Hai-Chao
Published: July 2013

Pulse pressure, the difference between the systolic and diastolic pressure, is an important characteristic of arterial blood pressure. Changes in pulse pressure occur when cardiac function or arterial compliance changes, which can be caused by ageing [1] and interventions such as cardiopulmonary bypass and left ventricular assist devices [2]. Therefore it is important to understand how both an increase and decrease in pulse amplitude affects arteries.
Low Mineralization Tends to Facilitate the Formation of Diffuse Damage in Bone
Authors: Dong X. Neil , Leng Huijie , Wang Xiaodu
Published: July 2013

Microdamage formation in bone is dependent on its ultra-structural and material properties. Previous studies of probabilistic failure analysis of mineral-collagen composites have indicated that mineral modulus affects the formation of microdamage in bone [1]. Therefore, the hypothesis of this study is that mineralization influences the morphology of microdamage in bone. To test this hypothesis, bone femurs from two types of mice (C57BL/6J and C3H/HeJ) with various bone mineral density [2] were fatigued to produce microdamage and the differences of microdamage morphology were then examined. In addition, nanoindentation techniques were employed to assess the difference of mineralization between these two mice strains.
Subject-Specific Experimental Validation of a C27 Cervical Spine Finite Element Model
Authors: Kallemeyn Nicole A. , Shivanna Kiran H. , Gandhi Anup A. , Kode Swathi , Grosland Nicole M.
Published: July 2013

Computational simulations of the spine have the ability to quantify both the external (i.e. angular rotation) and internal (i.e. stresses and strains) responses to external loading. This is an advantage over cadaveric bench top studies, which are limited to studying mostly external responses. Finite element (FE) analysis has been used extensively to investigate the behavior of the normal cervical spine in addition to its diseased and degenerated states [1,2].
Biomechanics Injury Analysis of Brain White Matter Using Cohesive Zone Method
Authors: Abolfathi N. , Syed A. R. , Karami G. , Ziejewski M.
Published: July 2013

Diffuse Axonal Injury (DAI) can happen due to sudden motion of the head and loading and is a major cause of fatality and severe disabilities. This injury can be biomechanically translated in terms of change in axon geometry and its separation and distortion from the surrounding cells and the extra cellular matrix (ECM). To study DAI, a microscale biomechanical modeling of tissue is forwarded. This modeling benefits from the studies on fibrous composite modeling procedure to examine the tissue and the fibrous axonal injury. Employing a developed micromechanics failure analysis for fibrous composites, the white mater of the brain is assumed as the composite with axon as the fiber and ECM as the matrix. The focus here is on the interface and adhesion of the axon and ECM on the material characteristics of the tissue. The cohesive zone modeling (CZM) is employed to model the interface. The impact due to interface is studied in detail on the characteristics of the white matter tissue. This modeling method enhances the previously proposed micromechanics modeling of brain tissue and enable one to predict the impact due to sliding, and separation of the axons and ECM on the load transfer, stress and strain distribution of axon, ECM and tissue for a microstructural examination of DAI and tissue failure. This can improve the understanding of injury from mechanical perspective and help in detail predicting of any injuries in cellular level in brain tissue.
Real Time Measurement of Head Acceleration During Youth Soccer Play
Authors: Hanlon Erin M. , Bir Cynthia A.
Published: July 2013

The collection of on-field, head impact data in soccer has been a challenge for researchers. Given the lack of headgear, the ability to instrument players, similar to what has been done in other sports [1, 2], is not possible. [3–5]. Laboratory recreations using reflective targets, EMG electrodes, and an instrumented bite plate have provided some insight into heading impact events [3, 5]. However, all of this instrumentation changes the ability of the player to move freely and, therefore, alters the dynamic of the impact. By developing a wireless acceleration measurement system which does not inhibit movement and provides no head protection, the linear and angular head accelerations can be measured during actual soccer play.
Strain Rate Effects on Structure-Property Relationship in the Rabbit Patellar Tendon
Authors: Davis Deborah , Clemmer John , Liao Jun , Horsetemeyer Mark F. , Williams Lakiesha N.
Published: July 2013

Mechanical properties, functional capabilities, and internal structure have all been investigated in tendons. The patellar tendon, specifically, is commonly used for replacing damaged or torn anterior cruciate ligaments (ACL). Many areas of engineering and research seek to determine aspects of biological tissues that can be modeled and mimicked in making artificial constructs. A proper and adequate understanding of the macro and micro-composition and structure-property relationship is essential to computational modeling of the tissue. The behavior of the tendon as a whole is dependent on the mechanics of the individual sublevels of hierarchy in combination.
Effect of Shear Stress on Extracellular Matrix Production of Synovium-Derived Cells
Authors: Sudama Hiroki , Ogawa Atsushi , Saito Kei , Ando Wataru , Nakamura Norimasa , Fujie Hiromichi
Published: July 2013

It is well known that various fibrous tissue such as tendons and ligaments functionally adapt to dynamic and static loads. Although a variety of biomechanical studies have been done to deterimine the mechanism of remodeling in fibrous tissues, it was difficult to obtain detailed information because of complicated condstitution of the tissues. We have developed a stem cell-based self-assembled tissue (scSAT) [1] for tissue engineering. Since the scSAT is consisted of synovium-derived mesenchyaml stem cells and their native extracellular matrix, it is a good experimental model to determine the process of remodeling of fibrous tisues. However, the response of shear stress to the scSAT specimen has not been determined so far, although such data are important for understanding of soft tissue remodeling and for improvement of regenerative medicine. Therefore, the present study was performed to determine the effect of shear stress on the extracellular matrix production of synovium-derived cells including mesenchymal stem cells.
Validation of Di-5-HT-Gd-DTPA, an Enzyme-Specific MR Contrast Agent for Myeloperoxidase, in the Rabbit Elastase Model of Cerebrovascular Aneurysm
Authors: DeLeo Michael J. , Gounis Matthew J. , Wakhloo Ajay K. , Bogdanov Alexei A.
Published: July 2013

Characterization of molecular imaging probes in multiple animal models of disease is essential to increase their diagnostic potential. For example, we recently demonstrated visualization of active inflammation in a rabbit model saccular aneurysm using clinical field strength MRI and the paramagnetic MR contrast agent di-5-HT-GdDTPA, which has been shown in vitro to be sensitive and specific for the enzyme myeloperoxidase (MPO). While the use of transgenic mice (MPO−/−) has demonstrated specificity of di-5-HT-GdDTPA for MPO in a model of myocardial infarction [1], MPO-deficient rabbits are not available. Therefore, in this study, we sought to validate di-5-HT-GdDTPA MPO specificity in the New Zealand white rabbit by comparing serial enhancement ratios of di-5-HT-GdDTPA to a structurally similar MR contrast agent, di-Tyr-GdDTPA, which is activated by peroxidases but not by MPO. Structural diagrams of the synthesis of the two agents are demonstrated in Figure 1 [2].
Method Development for Determination of Initial Stability of Cementless Femoral Stems
Authors: Scholl Laura Yanoso , Schmidig Gregg , Thakore Mayur , Hayes Daniel
Published: July 2013

For press-fit (cementless) total hip arthroplasty, area of non-contact (gaps) between the bone and the implant may reduce the mechanical stability of the implant. Stability is essential for osteointegration and ultimately the long-term success of the implant. Therefore, it is necessary to assess the micromotion that occurs at the bone/implant interface and identify whether this micromotion is within an appropriate range to allow for successful osteointegration between the implant and host bone [1].
An Experimental Study of Metallic Transfer on Ceramic Femoral Heads
Authors: Doud Douglas M. , Beck Preston R. , Petersen Donald R. , Lemons Jack E. , Eberhardt Alan W.
Published: July 2013

Postoperative dislocation of total hip replacements has been documented to occur at a rate of approximately 2.4–3.9% [1–3]. Such events may result in the transfer of titanium from the acetabular cup to the femoral head, both during the dislocation and surgical reduction of the dislocated joint [3,4]. If the head is reduced with this transfer present, the joint life expectancy, which depends on articulating surfaces remaining smooth, is reduced [4]. Although the presence of metal transfer on retrieved femoral heads after dislocation is documented, no previous studies have attempted to quantify the forces or contact stresses at which metal transfer occurs.
Dynamic Shear Stress Induced Platelet Activation in Blood Recirculation Devices: Implications for Thrombogenicity Minimization
Authors: Girdhar Gaurav , Sheriff Jawaad , Xenos Michalis , Alemu Yared , Claiborne Thomas , Slepian Marvin , Jesty Jolyon , Einav Shmuel , Bluestein Danny
Published: July 2013

Implantable blood recirculation devices such as ventricular assist devices (VADs) and more recently the temporary total artificial heart (TAH-t) are promising bridge-to-transplant (BTT) solutions for patients with end-stage cardiovascular disease. However, blood flow in and around certain non-physiological geometries, mostly associated with pathological flow around mechanical heart valves (MHVs) of these devices, enhances shear stress-induced platelet activation, thereby significantly promoting flow induced thrombogenicity and subsequent complications such as stroke, despite a regimen of post-implant antithrombotic agents. Careful characterization of such localized high shear stress trajectories in these devices by numerical techniques and corresponding experimental measurements of their accentuated effects on platelet activation and sensitization, is therefore critical for effective design optimization of these devices (reducing the occurrence of pathological flow patterns formation) for minimizing thrombogenicity [1].
Short Term Cardiac Memory Results in Altered Regional Mechanical Function
Authors: Skorinko Jeremy K. , Guyette Jacques P. , Plotnikov Alexei N. , Shlapakova Iryna N. , Danilo Peter , Ozgen Nazira , Rosen Michael R. , Gaudette Glenn R.
Published: July 2013

Normal electrical activation begins in the sinoatrial node and propagates through the atrium to the atrioventricular node and into the ventricle. Some patients with abnormal electrical activation require a pacemaker with leads implanted into the ventricle. This pacing changes the activation sequence to initially activate the ventricle in the region closest to the pacing electrode. Pacing also decreases mechanical function around the electrode and creates a gradient of regional stroke work (RSW) with the least work done near the pacing site and increasing with distance from the pacing location[1].
Spatiotemporal Deformation of Engineered Tissue During Freezing
Authors: Teo Ka Yaw , Dutton J. Craig , Han Bumsoo
Published: July 2013

A reliable long-term preservation technology is highly desired to provide “off-the-shelf” availability of various engineered tissues (ETs). Among the existing preservation techniques, cryopreservation, which is preserving biomaterials in the frozen state, remains the primary candidate for long-term storage of ETs. One of the most significant challenges in cryopreservation is the lack of consistency in maintaining the functionality of ETs [1]. Since the functionality is closely related to the microstructural integrity of extracellular matrix (ECM) and cellular viability, the ECM microstructure should be maintained as well as the viability of cells [2, 3].
Mechanical Properties of the Iris Dilator and Stroma Using Nanoindentation
Authors: Whitcomb Julie E. , Amini Rouzbeh , Simha Narendra , Barocas Victor H.
Published: July 2013

In certain disorders of the eye such as angle-closure glaucoma [1], pigment dispersion syndrome [2], and intra-operative floppy iris syndrome [3] the contour of the iris plays an important role. The active iris contour is determined by a combination of external stresses arising from the flow of the aqueous humor and internal stresses due to the passive and active components of the constituent tissues. For example, in angle closure, the iris bows anteriorly, and the abnormal shape and position of the iris are directly related to the blockage of aqueous humor outflow, increasing the intraocular pressure. While the interaction between the aqueous humor and iris has been studied [4], little is known about the effect of the components of the iris on the contour. The iris is composed of stroma, pigment epithelial cells, and two constituent muscles, the sphincter iridis and dilator pupillae (Fig1).
Biomechanical Evaluation of the Lasso-Loop Arthroscopic Stitch
Authors: Raghava Parthasarathy , Ponce Brent A. , Hosemann Chad D. , Eberhardt Alan W.
Published: July 2013

The use of arthroscopic repair of rotator cuff tears continues to increase with improved surgical experience and instrumentation. However, it is widely accepted that the weakest aspect of the repair construct remains the tissue-suture interface [1, 2]. Critical to the repair is having high initial fixation strength to allow minimal gap formation and mechanical stability until healing occurs [3, 4]. This emphasizes the need to identify new suture techniques to improve the strength of repairs, open or arthroscopic, in an attempt to improve the rates of healing.
A Rigid Body and Spring Model of the Lumbar Spine Which Considers the Mechanical Loads at the Bone-Screw Interface
Authors: Kiriyama Yoshimori , Matsumoto Morio , Toyama Yoshiaki , Andriacchi Thomas P. , Nagura Takeo
Published: July 2013

A spinal instrument with pedicle screws is one of the most effective surgical techniques for correction of spinal deformity. However, when excessive mechanical loads are applied on the implant upon the fixation, there is a concern for back out of the screw in the cases with poor bone condition such as osteoporosis. For that reason, the mechanical loads at the bone-screw interface should be analyzed for safe and successful correction.
Finite Element Investigation of Out-of-Position Failure Modes for the Knee-Thigh-Hip of a 50th Percentile Male During a Frontal Car Crash
Authors: Silvestri Chiara , Ray Malcolm H.
Published: July 2013

The introduction of air bags has reduced injuries to the upper region of the body for occupants of vehicles in frontal crashes, such as head and thorax. Airbags have not, however, improved the safety of occupants with respect to injuries to the lower extremities. Though lower extremity injuries are usually not life threatening, they can have long lasting physical and psychosocial consequences. A validated Knee-Thigh-Hip (KTH) finite element model of a 50th percentile male was used to investigate injury mechanisms during frontal car crashes with the occupant in different positions. Simulations of frontal impacts were performed with the Knee-Thigh-Hip joints at different angles of thigh flexion, adduction and abduction. Results show that the failure mechanism can significantly depend on the occupant position prior to impact. Failure mechanisms in the simulations were compared to results found in literature to ensure the model provides a useful tool for predicting fractures in the lower limb resulting from out-of-position frontal vehicle crashes.
Evaluating Different Criteria to Diagnose ACL Rupture Using a Knee Arthrometer
Authors: Soudbakhsh Damoon , Tahmasebi Mohammad-Naghi , Parnianpour Mohamad
Published: July 2013

Every year many people suffer from knee injuries. Previous studies on patients with knee injuries has shown that about 40% percent of knee injuries are ligament injuries, and about 50% of the ligament injuries are the Anterior Cruciate Ligament (ACL) injuries [1–2]. Knee arthrometers are widely used to diagnose ACL injuries, along with other methods [3–4]. In the current research, a knee arthrometer which was developed to provide an accurate measurement of AP displacement of the knee [5] was used to measure anterior laxity of the knees of 20 subjects, and the results were analyzed to find better criteria to diagnose ACL rupture using knee arthrometers.
The Effect of Trabecular Microstructure and Mechanical Properties on the Pullout Strength of Suture Anchors
Authors: Yakacki Christopher M. , Poukalova Mariya , Guldberg Robert E. , Lin Angela , Gall Ken
Published: July 2013

Suture anchors are a type of bone anchor designed to attach soft tissues, such as tendons and ligaments, to bone. Suture anchors are commonly used for soft tissue repairs including rotator cuff repairs, bicep tenodesis, flexor tendon repairs, and patellar tendon ruptures among others. In 2007, over 1 million suture anchors were used in 460,000 shoulder repairs in the US alone[1].
A Study of Surgical Optimization for Congenital Heart Diseases Based on Computational Hemodynamic Analysis
Authors: Qian Y. , Liu J. L. , Umezu M. , Itatani K. , Miyaji K.
Published: July 2013

Hypoplastic left heart syndrome (HLHS) is one kind of serious congenital heart diseases (CHD). With a small, underdeveloped left ventricle, a heart suffering from HLHS cannot effectively supply enough blood flow to provide for the needs of the body. In order to improve blood circulation, surgery for HLHS has to be carried out at a very early stage. In general, three-stage palliative surgical management for newborns is now widely accepted [1, 2]; Norwood, Glenn, and Fontan.
How an Eukaryotic Cell Senses the Substrate Stiffness? An Exploration Using a Finite Element Model With Cytoskeleton Modelled as Tensegrity Structure
Authors: De Santis Gianluca , Boschetti Federica , Lennon Alex B. , Prendergast Patrick J. , Verdonck Pascal , Verhegghe Benedict
Published: July 2013

Mammalian cells in vivo are connected to the ECM (or other substrate, SS) or other cells having elastic moduli ranging from 10 to 10000 Pa. Several experimental evidences relate cell processes (e.g. changes of spreading area, cytoskeletal filament assembling, focal adhesion complex (FAC)) to SS stiffness, but how a passive substrate affects these cell processes is still unknown [1,2].
Patient Specific Finite Element Modelling of the Carotid Bifurcation
Authors: Creane Arthur , Maher Eoghan , Sultan Sherif , Hynes Niamh , Kelly Daniel J. , Lally Caitríona
Published: July 2013

Atherosclerosis frequently occurs at the carotid bifurcation and plaque rupture at this site is one of the leading causes of stroke. Over 50% of these strokes occur in asymptomatic patients and thus better indicators of the disease need to be developed. Finite element studies of arterial wall segments have provided key information on the biomechanics of arteries, from prediction of atherosclerotic plaque rupture [1] to the effectiveness of stents [2]. Most studies however have focused on simple straight arterial segments and few on complex geometries such as bifurcations or aneurysms. Studies which have addressed the carotid bifurcation have been based on either idealised geometries [3] or on a single patient specific geometry often generated from cadaveric material [4].
Computational Fluid Dynamic Analysis of an Instrumented Endotracheal Tube for Total Liquid Ventilation to Optimize Pressure Transducer Positioning
Authors: Zaffora Adriano , Bagnoli Paola , Fumero Roberto , Costantino Maria Laura
Published: July 2013

Despite advances in respiratory care, the treatment of critical neonatal patients with conventional mechanical ventilation (CMV) techniques has still many drawbacks. To address this issue, Total Liquid Ventilation (TLV) with liquid perfluorocarbons (PFC) has been investigated as an alternative respiratory modality [1,2]. A dedicated TLV ventilator supplies PFC tidal volumes (TV) through an endotracheal tube (ETT) inserted into the trachea. In experimental studies, TLV proved to be able to support pulmonary gas exchange while preserving lung structure and function. Moreover, PFC properties make these liquids an optimal medium to treat neonatal respiratory failure [1–3]. However, different aspects of TLV have to be further investigated for a safe transition from the laboratory experience to the clinical application. One of these aspects is the possible airway and lung injury that may be caused by the peculiar fluid dynamics developed when using an incompressible and viscous liquid instead of air as a respiratory medium. To overcome this issue, continuous reliable real-time monitoring of airway pressure during TLV is crucial. Thus, the instrumentation of the ETT with a pressure transducer (PT) is mandatory to perform a safe TLV treatment [4–6]. At present, no commercial instrumented ETTs designed for TLV are available; thus during TLV experimental animal trials [4–6] ETT prototypes instrumented with homemade PT-equipped catheters are currently used. However, the positioning of this catheter has to be optimized in order to reduce fluid dynamic disturbances that can alter pressure measurements. Aim of this study is to investigate on the PFC fluid-dynamic patterns in the presence of the catheter by computational fluid dynamic (CFD) analysis, in the view of the development of a TLV dedicated instrumented ETT. In particular, the effect of two different positioning of the PT catheter on the PFC fluid dynamics and airway pressure measurement was evaluated for a neonatal ETT.
Individual Motions of Red Blood Cells in High-Hematocrit Blood Flowing in a Microchannel With Complex Geometries
Authors: Ishikawa T. , Fujiwara H. , Matsuki N. , Lima R. , Imai Y. , Ueno H. , Yamaguchi T.
Published: July 2013

Blood flow in a microchannel with complex geometries has been investigated to develop biomedical microdevices (e.g. Faivre et al., 2006) or to understand pathology in small vessels, such as lacunar infarcts. In a small channel, say 100 μm in diameter, the blood is no longer assumed to be a homogeneous fluid because the size of the red blood cells (RBCs) cannot be neglected compared to the generated flow field (the diameter of a RBC is about 8 μm). In such a case, we must treat the blood as a multiphase fluid, and investigate the motion of individual cells in discussing the flow field. In this study, we investigated the motion of RBCs in a microchannel with stenosis or bifurcation using a confocal micro-PTV system. We measured individual trajectories of RBCs under high Hct conditions (up to 20%), when the interactions between RBCs become significant. We discuss the effect of Hct on the flow field and cell-free layers, as well as the effect of deformability of RBCs on the cell-free layer thickness by hardening RBCs using a glutaraldehyde treatment.
CFD Analysis of Turbulent Particle Deposition in the Lungs
Authors: Radhakrishnan Hari , Kassinos Stavros
Published: July 2013

We are constantly inhaling and exhaling solid and liquid particles that are present all around us in the atmosphere. Medicines used to treat pulmonary diseases are also often nebulized, and administered as inhaled particles. Research has shown that only 10 to 20 per cent of the inhaled drugs reaches the lungs. Another study has shown that there is a high correlation between regions with high concentration of deposited particles and bronchial carcinoma origin sites. Studying how particles are transported and deposited in the airways can help in improving drug delivery and targeted therapy of pulmonary diseases. Therefore, numerous researchers have studied particle deposition in the lungs using experiments and computer-aided numerical simulations.
FAK, SMAD and MAPK Pathways Diverge During Osteogenic and Chondrogenic Differentiation of Adipose-Derived Mesenchymal Cells
Authors: Kemmis Carly M. , Wagner Diane R.
Published: July 2013

Adipose-derived mesenchymal cells (AMCs) are a promising cell source for orthopaedic tissue engineering applications due to their accessibility and multi-lineage potential [1]. However, future use in bone and cartilage regeneration requires a comprehensive understanding of the pathways driving AMCs to osteogenic and chondrogenic lineages. We have previously demonstrated the dual function of a single medium containing bone morphogenetic protein-6 (BMP-6) on differentiation of AMCs; in the presence of BMP-6, monolayer culture induces osteogenic differentiation while pellet culture stimulates chondrogenesis [2]. Additionally, BMP-6 has been demonstrated to be both osteogenic and chondrogenic on marrow-derived stem cells [3,4], but the mechanisms driving the effect of BMP-6 in these conditions remains poorly understood. Recent studies have implicated focal adhesion kinase (FAK) and cell/matrix attachment in directing osteogenesis, while an absence of these signals support chondrogenesis [5,6]. We hypothesized that the focal adhesions present in monolayer prompt different pathway activation than in pellet culture, resulting in either osteogenic or chondrogenic differentiation of AMCs in response to BMP-6. Our goal was to elucidate the cellular mechanisms employed by BMP-6 during differentiation. Therefore, we examined the activation of the FAK, MAP kinase (MAPK) pathways, and the canonical BMP-6 pathway via SMAD signaling in both monolayer and pellet culture.
Measurements of Wave Speed and Distensibility in Elastic Tubes Using the Diameter-Velocity Loop
Authors: Li Ye , Khir Ashraf W.
Published: July 2013

The mechanical properties of arterial walls play an important role in the regulation of cardiovascular hemodynamics. In the past decades, arterial wall dynamics attracted much attention and several methods have been proposed to assess the mechanical properties of the human arteries [1].
Mucopolysaccharidosis VII and the Developing Lumbar Spine: Consequences for Annulus Fibrosus and Vertebral End Plate Mechanical Properties
Authors: Smith Lachlan J. , Martin John T. , Szczesny Spencer E. , Ponder Katherine P. , Haskins Mark E. , Elliott Dawn M.
Published: July 2013

Mucopolysaccharidosis VII (MPS VII) is a rare pediatric, hereditary disorder characterized by deficient activity of beta-glucuronidase, an enzyme that degrades chondroitin, dermatan and heparan sulfate glycosaminoglycans (GAGs) [1,2]. This deficiency leads to systemic lysosomal accumulation of GAGs, resulting in severely impaired physical and intellectual development, with patients frequently not surviving until adulthood. In the spine, the disease is characterized by poorly formed and aligned vertebral bodies, leading to high incidences of kyphosis and scoliosis [1–3].
Subject-Specific EMG Pattern Classification for Effective Rehabilitation of Stroke Survivors
Authors: Lee Sang Wook , Wilson Kristin , Lock Blair A. , Kuiken Todd A. , Kamper Derek G.
Published: July 2013

Many stroke survivors experience chronic upper extremity impairment that leads to significant functional limitations. Especially for those with more severe impairment, therapeutic treatment may have limited effect. Thus, the introduction of assistive techniques, such as powered orthoses, may prove more beneficial in improving function. A challenge, however, lies in providing volitional control of the device to the user. Electromyography (EMG) of muscle has been used with stroke survivors to trigger myoelectric prostheses [1], but the number of the targeted motions and their complexity was limited.
Modeling of the Cardiovascular System During Stand Tests and Centrifuge Training
Authors: Coats Brandon W. , Sharp M. Keith
Published: July 2013

Postflight orthostatic intolerance (POI) is a condition describing the dizziness and fainting that astronauts experience when they are subjected to gravity after becoming acclimatized to microgravity. POI afflicts a significant fraction of male and nearly all female astronauts upon return to Earth from orbital Space Shuttle missions. No instances of POI on the moon were reported from the limited number of male astronauts who participated in lunar landings (1/6 G), but possible symptoms of POI on the moon and Mars (3/8 G) are potentially catastrophic due to the more hazardous conditions and lack of medical facilities. In addition, the long duration flights necessary to reach Mars may elicit adaptations that increase the risk of POI. A number of countermeasures have been proposed and some have been tested during return to Earth, but testing on the moon and Mars is obviously problematic. Of these countermeasures, artificial gravity (centrifuge training) has been identified as a treatment with high likelihood of success. Therefore, computer modeling was undertaken to compare the orthostatic response of male and female astronauts during stand tests in constant gravity, for which the gravitational body force is constant, and in centrifuge conditions, for which the centrifugal body force increases with distance from the centrifuge axis.
Emulating the Anatomy of Acupuncture Points With In Vitro Models
Authors: Julias Margaret , Edgar Lowell T. , Buettner Helen M. , Shreiber David I.
Published: July 2013

In traditional acupuncture, fine needles are inserted and rotated at specific locations on the body that correspond to specific therapeutic effects, which can occur locally or at a distance from the needling point. The majority of acupuncture points co-align with fascial planes under the skin, which present more subcutaneous connective tissue [1] (Fig 1). Needle insertion and rotation induces this connective tissue to couple to and wind around the needle, forming a whorl of alignment and generating measurable force on the needle that is significantly higher at fascial planes in comparison to insertion above a muscle [2, 3]. However, the effects of the varying tissue anatomy at fascial planes on fiber winding are not known. At these planes, the tissue is bounded on two sides by skeletal muscle and generally becomes narrower with increasing depth, presenting distinct boundary conditions compared to locations above a muscle, which resembles an infinite plane.
The Coupled Influences of Substrate Stiffness and Cell Spreading Area on Traction Force
Authors: Han Sangyoon , Sniadecki Nathan J.
Published: July 2013

Traction forces that cells generate play an important role in their interactions with the local environment. Cells use actin polymerization and myosin contraction to indirectly transmit cytoskeletal tension to their adhesions in order to provide stability for active spreading, pull themselves forward during migration, and probe the matrix rigidity. Interestingly, there is developing evidence to show that cells regulate their traction forces in response to feedback they obtain from mechanical factors in their environment like stiffness, geometry, and adhesivity [1,2]. What is unclear is to what extent are mechanical factors and biological interactions interdependent. Consequently, the aim of this paper is to examine the coupled influence of two main regulators of traction forces: substrate stiffness and cell spreading area.
Effect of Caval Waveform on Energy Dissipation of Failing Fontan Patients
Authors: Dur Onur , Kocyildirim Ergin , Degroff Curt G. , Wearden Peter , Morell Victor , Pekkan Kerem
Published: July 2013

Last stage of the palliative surgical reconstruction (i.e. Fontan procedure) for the infants with functional single-ventricle is total cavopulmonary connection (TCPC), where the superior vena cavae (SVC) and inferior vena cavae (IVC) are routed directly into the pulmonary arteries. Limited pumping energy available due to the absence of right-ventricle and altered venous characteristics require optimized hemodynamics inside the TCPC pathway, which can be achieved by minimizing the power losses.
Computational Simulation of Traveling Arrhythmic Waves in Myocardial Tissue
Authors: Wong Jonathan , Göktepe Serdar , Kuhl Ellen
Published: July 2013

Cardiac arrhythmias are common cardiac disorders characterized by irregular electrical activity of the heart. Each year in the United States alone, about half a million deaths and 835,000 hospital discharges result from arrhythmias. In fact, atrial fibrillation is responsible for 15–20% of all ischemic strokes [1]. Due to the complexity of the electrical conduction pathways in myocardium, computational models are useful platforms for gaining insight into the origin of arrhythmias, as well as the development of corrective options. For these purposes, a quantitative finite element model based on the phenomenological Aliev and Panfilov model [2] was implemented to characterize the electrical behavior of cardiac tissue. Several examples of simulated re-entrant spiral waves demonstrate that our implementation can indeed capture the electrical aspects of cardiac tissue.
Modeling Adhesion of Micro/Nanoparticles Under Shear Flow for Nanomedicine Application
Authors: Liu Yaling , Shah Samar
Published: July 2013

Adhering to diseased cells via specific binding is critical in determining the functionality of nanoparticle targeted delivery. This is evident specifically since delivery happens in complex human cardiovascular system. This paper focuses on developing computational methods for micro and nanoparticle adhesion.
Distribution of Oxygen, Glucose and Lactate in Degenerated Intervertebral Disc
Authors: Huang Chun-Yuh , Gu Wei Yong
Published: July 2013

Poor nutritional supply has been a major concern for the health of intervertebral disc (IVD) since the IVD is the largest avascular tissue in the human body. The transport of vital nutrients to cells relies on diffusion and convection through the extracellular matrix (ECM) in the IVD. Transport and metabolism of nutrients (e.g., oxygen and glucose) within the IVD depend on many factors, including the material properties of ECM (e.g., permeability, elastic modulus, and solute diffusivity), cellular metabolic rates, nutritional supply at the edge of the IVD, and mechanical loading [1–6]. Tissue degeneration alters the material properties of the IVD, such as an increase in elastic modulus and a decrease in water content, fixed charge density, permeability and solute diffusivity [6]. However, the effect of tissue degeneration on transport and metabolism of nutrients in the IVD under mechanical loading has not been elucidated. The objective of this study was to numerically investigate the distribution of glucose, oxygen and lactate in the degenerated IVD under static unconfined compression using the mechano-electrochemical mixture theory [7].
Surgeon Experience Level Affects Mechanics of the Pivot Shift Test for Posterolateral Rotatory Instability of the Elbow
Authors: Chu Thomas , Ty Jen M. , Orazov Bayram , Strauss Nicole , O’Reilly Oliver M. , Buckley Jenni M. , Lattanza Lisa L.
Published: July 2013

Posterolateral rotatory instability (PLRI) of the elbow occurs secondary to an injury to the lateral ulnar collateral ligament and lateral stabilizing structures [2]. The lateral pivot-shift test (PST) is a clinical examination for diagnosing PLRI [1]. The test involves moving the elbow from full extension to flexion while applying simultaneous supination torque, valgus moment, and axial compression [2]; a positive result is characterized by ulnohumeral subluxation that is seen clinically as posterolateral movement of the radial head and an incongruent radiocapitellar joint [2]. The PST is difficult to reliably reproduce in an office setting [3]. This can be due to patient-guarding or inexperience of the examiner. It is likely that the experienced examiner may perform the test differently from the inexperienced examiner. The PST has not previously been characterized biomechanically in the laboratory. Thus, the objective of this study is to fully characterize the biomechanics of the PST for PLRI. We will evaluate the repeatability of the PST across multiple surgeons and determine how the clinician’s level of training affects their method of testing. These results will be useful in developing training guidelines to standardize PST application as well as to improve accuracy.
Verification of a Finite Element Method for Solving One-Dimensional Equations of Blood Flow Incorporating a Viscoelastic Wall Model
Authors: Raghu Rashmi , Taylor Charles A.
Published: July 2013

The one-dimensional (1-D) equations of blood flow consist of the conservation of mass equation, balance of momentum equation and a wall constitutive equation with arterial flow rate, cross-sectional area and pressure as the variables. 1-D models of blood flow enable the solution of large networks of blood vessels including wall deformability. Their level of detail is appropriate for applications such as modeling flow and pressure waves in surgical planning and their computational cost is low compared to three-dimensional simulations.
Mechanical Anisotropy of Individual Osteons in Bone Tissue at High Spatial Resolutions
Authors: Carnelli Davide , Yao Haimin , Dao Ming , Vena Pasquale , Contro Roberto , Ortiz Christine
Published: July 2013

Secondary osteons, the fundamental units of cortical bone, consist of cylindrical lamellar composites composed of mineralized collagen fibrils. Due to its lamellar structure, a multiscale knowledge of the mechanical properties of cortical bone is required to understand the biomechanical function of the tissue. In this light, nanoindentation tests were performed along the axial and transverse directions following a radial path from the Haversian canal to the osteonal edges. Different length scales are explored by means of indentations at different maximum penetration depths. Indentation moduli and hardness data were then interpreted in the context of the known microstructure. Results suggest that secondary osteons hierarchical structure is responsible for an observed length scale effect, homogenization phenomena and anisotropy of mechanical properties.
Finite Element Design of Nitinol Embolic Protection Filters Based on Parametric Modelling With PyFormex: A Feasibility Study
Authors: De Beule M. , Conti M. , Mortier P. , Van Loo D. , Verdonck P. , Vermassen F. , Segers P. , Auricchio F. , Verhegghe B.
Published: July 2013

The widespread acceptance of Carotid Artery Stenting (CAS) to treat a stenosed carotid vasculature and its effectiveness compared with its surgical counterpart, carotid endarterectomy (CEA) is still a matter of debate [1]. A major concern related to CAS is embolization distal to the site of treatment potentially leading to stroke or other severe neurological complications. Embolization associated with CAS is mainly due to the plaque debris and thrombi generated during the dilatation of the stenosis and stent positioning. Consequently, embolic protection filters have been developed to capture this released debris and they appear to have a significant favorable impact on the success of CAS [2,3]. Currently, several embolic filter designs are available on a rapidly growing dedicated market. However, some drawbacks such as filtering failure, inability to cross tortuous high-grade stenoses, malpositioning and vessel injury still remain and require further design improvement.
Reproduction of Blood Flow Field by Numerical Simulation Integrated With Ultrasonic Measurement With Noise
Authors: Funamoto Kenichi , Hayase Toshiyuki , Saijo Yoshifumi , Yambe Tomoyuki
Published: July 2013

We have developed ultrasonic-measurement-integrated (UMI) simulation, in which feedback signals based on the optimal estimation of errors in the velocity vector determined by measured and computed Doppler velocities at feedback points are added to the governing equations (see Fig. 1) [1,2]. Our previous numerical studies showed the efficiency of UMI simulation for reproduction of blood flow field, as well as the transient and steady characteristics. However, in real ultrasonic measurement, noise is often included and may deteriorate the computational accuracy of UMI simulation. In this study, the effect of the ultrasonic measurement error due to Gaussian noise on UMI simulation was evaluated by a numerical experiment.
Strength of Atherosclerotic Plaque in Carotid Artery
Authors: Lawlor Michael , Kavanagh Eamon , Grace Pierce , McGloughlin Tim , Walsh Michael
Published: July 2013

Atherosclerotic disease in the carotid artery is a high risk factor for stroke. Stroke is the third-leading cause of death, constituting approximately 700,000 cases each year in the United States [1]. The susceptibility of atherosclerotic plaque to rupture during the carotid angioplasty and stenting (CAS) procedure [2] makes it necessary to determine the force the plaque can withstand without the risk of embolisation.
Effects of Tunnel Location for Suture Augmentation Following Anterior Cruciate Ligament Injury
Authors: Fisher Matthew B. , Jung Ho-Joong , McMahon Patrick J. , Woo Savio L.-Y.
Published: July 2013

The anterior cruciate ligament (ACL) of the knee is frequently injured, but it has limited healing potential. Surgical reconstruction using soft tissue autografts is often required for active patients. However, about 20–25% of patients have less than satisfactory results and some even developed of osteoarthritis in the long-term. Thus, there is a need for alternative approaches. With advances in functional tissue engineering, healing of the ACL using growth factors and/or bioscaffolds has generated new clinical interests [1].
The Development of Physiological Compliant Abdominal Aortic Aneurysm Models for In Vitro Flow Studies
Authors: Corbett Timothy J. , Doyle Barry J. , Callanan Anthony , McGloughlin Tim M.
Published: July 2013

A vast amount of experimental research has been undertaken in the past decade to investigate different aspects of preoperative and postoperative abdominal aortic aneurysms (AAAs). Much of this research has been based on the use of mock arteries in an in vitro flow loop to mimic the behaviour of the abdominal aorta in vivo [1]. These models should be reproducible, have consistent material properties, consistent thickness and be physiological in behaviour.