bluuebunny/crossref_metadata_2025 huggingface dataset:
Indentation Simulation of Ovariectomized Sheep Bone Using a Viscoelastic/Plastic Damage Model
Authors: Zhao Yang , Ovaert Timothy C.
Published: July 2013

Indentation techniques have become a standard method to assess the mechanical properties of numerous materials. In recent years, nanoindentation of bone has been used to extract the mechanical behavior at the level of osteons and lamellae. Under a transmitted light microscope, small microcracks can be observed in cortical bone, and breakage of trabeculea can be observed in trabecular bone. These cracks are implicated in physiological phenomena including stress fractures, bone remodeling, and adaptation. Together, these material discontinuities can be considered as damage. Damage accumulation of bone is generated through daily mechanical loading, and then recovered during remodeling. For bone indentation modeling, even though pre-existing damage may be neglected in most cases, new damage can also be produced during the process of testing. Thus, damage accumulation needs to be considered when establishing a nanomechanical bone model.
A 2D Finite Element Model of Lateral Transmission of Force in Skeletal Muscle
Authors: Zhang Chi , Gao Yingxin
Published: July 2013

Skeletal muscle has a complex hierarchical structure which is mainly composed of myofibers and the surrounding extracellular matrix (ECM) including endomysium, perimysium, and epimysium. Myofibers are long, cylindrical, multinucleated cells composed of repeating sarcomeres, which are basic functional units for skeletal muscle contraction. In order to produce body movement, the force generated by myofiber has to be transmitted from individual fiber to the tendon. The commonly accepted site for force transmission is the myotendinous junction (MTJ) where the myofibers connect to the tendon. However, the myofibers mainly end within the muscle fascicles without reaching the MTJ in many muscles, in which case the force has to be transmitted laterally to adjacent fiber through shear and to the tendon eventually.
Penetration Mechanics of Endovascular Stent Graft Barbs in Aortic Tissue
Authors: Lin Kathleen , Berkowitz Benjamin , Raghavan Madhavan L.
Published: July 2013

Endovascular stent grafts with barbs — tiny needle-like pins that provide active fixation — are increasingly used for treating aortic aneurysms and dissections. Characterization of barb penetration mechanics may help improve stent-graft designs. Barb angle varies among manufacturers (10–50°). But little is known regarding aortic wall penetration characteristics in relationship to barb angle. There is a body of work on needle insertion properties such as insertion forces into soft tissues. However, there have not been specific studies involving the aorta and the relationship between entry angle and entry force. Kratzberg et al. [1,2] demonstrated that barb angle was closely related to penetration angle and that lower angles between the barb and the body of the aortic stent-graft resulted in better penetration probability and fixation strength in the aortic wall. In order to assess why lower barb angles (i.e., barb axis closer to the graft axis) resulted in better penetration, this study investigates the relationship between barb penetration angle and aortic tissue entry force and compared it to a homogeneous control membrane made of silicone.
Experimental and Numerical Flow Visualization in Patient Specific Pre Operative Human Airway Geometry
Authors: Vermeulen Mathias , Van Holsbeke Cedric , Claessens Tom , De Backer Jan , Van Ransbeeck Peter , Verdonck Pascal
Published: July 2013

An experimental and numerical platform was developed to investigate the fluidodynamics in human airways. A pre operative patient specific geometry was used to create an identical experimental and numerical model. The experimental results obtained from Particle Image Velocimetry (PIV) measurements were compared to Computational Fluid Dynamics (CFD) simulations under stationary and pulsatile flow regimes. Together these results constitute the first step in predicting the clinical outcome of patients after lung surgeries such as Lung Volume Reduction.
Compaction and Anisotropy Induced by Remodeling of the Collagen Network’s State of Tension-Compression Transition
Authors: Nagel Thomas , Kelly Daniel J.
Published: July 2013

Extracellular matrix remodeling is ubiquitous in connective, musculoskeletal and cardiovascular tissues. The collagen network can thereby not only remodel its orientation [1] but also its stress-free configuration. This stress-free configuration can be described by the so-called transition stretch — the stretch above which a fiber begins to bear load. Remodeling of collagen crimp has been shown to be involved in long bone growth [2], contracture, scar pathologies, collagen gel compaction and can be cell mediated or occur via cell-independent mechanisms [3, 4, 5].
Bodyweight Apparatus Used to Apply Compression Garments for Lymphedema Patients
Authors: DeRoche David , Sharp Zachary
Published: July 2013

Lymphedema is a medical condition caused by an excess of fluid collecting in the interstitial tissue. When the lymphatic system is functioning normally, the interstitial fluid passes into the lymphatic capillaries, thought the lymphatic ducts, and returns to the circulatory system [1]. If this system is disrupted due to congenital reasons, surgery, or radiation therapy associated with cancer treatment, the fluid is unable to properly drain [2]. This collection of fluid leads to swelling of the affected area, usually the legs or arms (Figure 1).
Layer-Specific Distributed Collagen Fiber Orientations in Human Arteries, From Thoracic Aorta to Common Iliac
Authors: Schriefl Andreas J. , Regitnig Peter , Pierce David M. , Holzapfel Gerhard A.
Published: July 2013

We use the well established method of polarized microscopy on picrosirius red stained tissue samples and a dispersion model to quantify over 37000 measured layer-specific 3D fiber orientations of 11 human thoracic and abdominal aortas and common iliac arteries. Our results yield mean fiber directions, quantitative dispersion data and the existence of two distinct and prominent fiber families for all layers of the aortic wall.
Numerical Reduction of Position Error in a Mechanical Tracking Linkage for Arthroscopic Hip Surgery
Authors: Geist Emily , Shimada Kenji
Published: July 2013

The selection of a tracking system for locating patient anatomy and/or surgical tools is of critical importance for many computer aided techniques in minimally invasive surgery. A mechanical tracking system has many advantages in a medical situation since it avoids the occlusion and distortion issues of optical and electromagnetic systems. However, few mechanical tracking systems exist due to the challenges of minimizing error accumulation along a serial linkage. To minimize error, the existing mechanical tracking linkages are large and bulky, making them impractical for a surgical setting.
An Electromechanical Bioreactor for Scaffold-Free Skeletal Muscle Tissue Engineering
Authors: Koppes Ryan A. , Schiele Nathan R. , Corr David T.
Published: July 2013

The loss of functional muscle from genetic disease, traumatic injury, or surgical excisions results in a physiologic deficiency that continues to remain without an effective clinical treatment [1]. Engineering functional muscle tissue in vitro for replacement in vivo may offer a potential remedy for this clinical demand. However, in vitro muscle constructs in two- and three-dimensions have yet to fully exhibit the dynamic mechanical responses of physiological muscle [2]. Furthermore, the application of mechanical and electrical stimulation in vitro has shown promise for growing contractile tissue [3], but these have been limited to 2-D and/or rely on inhibitory scaffold techniques. For these reasons, we sought a new approach to utilize both extrinsic growth and maturation cues, in addition to the myoblasts’ innate propensity to differentiate and produce functional myotubes in vitro, for the development of clinically-relevant skeletal muscle replacements.
A Simulation Tool for Virtual Stent Graft Deployment in Patient-Specific Abdominal Aortic Aneurysms
Authors: De Bock S. , De Beule M. , De Santis G. , Vermassen F. , Segers P. , Verhegghe B.
Published: July 2013

An Abdominal Aortic Aneurysm (AAA) is a pathological dilatation of the aorta, commonly involving the region between the renal arteries and the aortic bifurcation, with a high degree of mortality. Endovascular repair of AAA has proven to be a valid alternative for the conventional open repair, with clear benefits in terms of length of hospital stay, reduced operational mortality and less trauma [1]. However, stent grafts are still associated with various problems and failings, which may lead to AAA rupture or rise the need for an additional open surgery.
Evaluation of Syncardia Total Artificial Heart Using Device Thrombogenicity Emulator
Authors: Alemu Yared , Girdhar Gaurav , Xenos Michalis , Claiborne Thomas , Jesty Jolyon , Einav Shmuel , Slepian Marvin , Bluestein Danny
Published: July 2013

The thrombogenicity of the left ventricle of the temporary Total Artificial Heart (TAH-t) (SynCardia Systems, Inc. Tucson, AZ) was evaluated using our device thrombogenicity emulator (DTE) methodology [1] that integrates advanced numerical modeling of the whole device combined with experimental measurements of platelet activity. The ejection phase of the cardiac cycle, including diaphragm motion, was modeled with fully-coupled fluid structure interaction (FSI) simulation. Stress loading histories of several thousand platelet trajectories were extracted from these simulations and collapsed into quantitative probability density function (PDF) distributions that represent the TAH-t thrombogenic footprint. Representative stress-loading waveforms with substantially higher stress accumulation (high propensity to cause platelet activation) were replicated in computer controlled hemodynamic shearing device (HSD), where the effect on platelet activation was measured with a modified prothrombinase assay. By determining the platelet stress accumulation distribution, the thrombogenic signature unique to specific TAH design from the results, this methodology facilitates virtual evaluation and optimization of various designs.
Analysis of Aortic Wave Travel and Reflection Using Advanced Modeling Methods in Simplified Geometries
Authors: Taelman Liesbeth , Degroote Joris , Swillens Abigail , Vierendeels Jan , Patrick Segers
Published: July 2013

The analysis of wave travel and reflection has gained increased interest in the clinical community. The speed of the pressure pulse, PWV, (assessed from the time delay of the foot of the wave measured at two distant locations), is considered the gold standard method to assess the stiffness of arterial segments and has been shown to be of prognostic value for cardiovascular disease. Also, analysis of wave reflections has been suggested as diagnostic tool, a.o. to estimate the effect of the treatment of aortic coarctation (a congenital disease characterized by an obstructive narrowing of the upper descending aorta) on the load on the heart. The presence of a residual narrowing and/or local stiffening after treatment of aortic coarctation leads to an impedance mismatch and generates wave reflections that reach the heart very fast, given the short distance to the heart. The exact interplay between arterial stiffness, wave travel and reflection is, however, still relatively poorly understood due to the complexity of the arterial tree leading to scattered wave reflection, rather than discrete reflection.
Mechanical Characterization of Vascular Smooth Muscle
Authors: van den Broek Chantal , Nieuwenhuizen Jeroen , Rutten Marcel , van de Vosse Frans
Published: July 2013

Remodeling of the arterial wall, in response to e.g. induced hypertension, vasoconstriction, and reduced cyclic stretch, has been studied in detail to get insight into vascular pathologies [1]. Constitutive models are helpful to the understanding of the relation between different processes that occur in the arterial wall during remodeling. Including the smooth muscle cell (SMC) behavior in constitutive models is relevant, as those cells may change tone when subjected to an altered mechanical loading and can initiate arterial remodeling.
Magnetic Resonance Elastography for the Measurement of Annulus Fibrosus Material Properties
Authors: Cortes Daniel H. , Smith Lachlan J. , Moon Sung M. , Magland Jeremy F. , Wright Alexander C. , Elliott Dawn M.
Published: July 2013

Intervertebral disc degeneration is characterized by a progressive cascade of structural, biochemical and biomechanical changes affecting the annulus fibrosus (AF), nucleus pulposus (NP) and end plates (EP). These changes are considered to contribute to the onset of back pain. It has been shown that mechanical properties of the AF and NP change significantly with degeneration [1,2]. Therefore, mechanical properties have the potential to serve as a biomarker for diagnosis of disc degeneration. Currently, disc degeneration is diagnosed based on the detection of structural and compositional changes using MRI, X-ray, discography and other imaging techniques. These methods, however, do not measure directly the mechanical properties of the extracellular matrix of the disc. Magnetic Resonance Elastography (MRE) is a technique that has been used to measure in vivo mechanical properties of soft tissue by applying a mechanical vibration and measuring displacements with a motion-sensitized MRI pulse sequence [3]. The mechanical properties (e.g., the shear modulus) are calculated from the displacement field using an inverse method. Since the applied displacements are in the order of few microns, fibers may not be stretched enough to remove crimping. Therefore, it is unknown if the anisotropy of the AF due to the contribution of the fibers is detectable using MRE. The objective of this study is twofold: to measure shear properties of AF in different orientations to determine the degree of AF anisotropy observable by MRE, and to identify the contribution of different AF constituents to the measured shear modulus by applying different biochemical treatments.
An Investigation on the Use of Silicone to Model Arterial Tissue Behaviour in the Idealised Tuning-Fork Model of the Carotid Bifurcation
Authors: Mulvihill J. J. , O’Donnell M. R. , O’Connell B. M. , Walsh M. T.
Published: July 2013

The development of atherosclerosis in the carotid bifurcation of the cardiovascular system has been the subject of much investigation. The carotid bifurcation is a prevalent area for atherosclerotic plaque build-up (Sakata et al., 1988). The performance of minimally invasive treatment of this plaque build-up has been below expectations. There is an increased need to analyse the poor performance of this treatment by numerically and experimentally replicating the diseased carotid bifurcation geometry with realistic material behaviour. This paper presents the investigation of an analogue material to represent arterial tissue behaviour. The aim of this study is to computationally set up an idealised carotid bifurcation model and compare the mechanical behaviour of arterial tissue and a silicone material model.
Mechanically Induced Calcium Release From Bone Matrix Triggers Intracellular Ca2+ Signalling in Osteoblasts: A Novel Mechanotransduction Mechanism
Authors: Sun Xuanhao , Kishore Vipuil , Fites Kateri , Akkus Ozan
Published: July 2013

Bone cells are responsible for sensing and converting the mechanical signals into cellular signals to drive bone adaptation and damage repair [1]. Cell-mediated repair of bone is reported to be in preferential association with regions filled with microdamage [2]. Although different theories have been proposed for mechanisms involved in those processes (such as substrate deformation, fluid flow shear, and hydrostatic pressure in mechanotransduction [3], or microcrack and osteocyte apoptosis in damage detection [4]), knowledge on the exact form of physical stimuli which trigger bone cells, especially in critically loaded regions of bone, is still elusive.
In Vitro Three Dimensional Imaging of Human Carotid Atherosclerotic Plaques Using Ultrasonography
Authors: Boekhoven Renate W. , Rutten Marcel C. M. , van Sambeek Marc R. H. M. , van de Vosse Frans N.
Published: July 2013

Ruptured atherosclerotic plaques in the carotid artery are the main cause of stroke (70–80%). To prevent it, carotid endarterectomy is the procedure of choice in patients with a recent symptomatic 70–99% stenosis. Today, the selection of candidates is based on stenosis size only. However, endarterectomy is beneficial for only 1 out of 6 patients [1], the patients with unstable plaques (Fig. 1). Knowledge of mechanical properties of different components in the atherosclerotic arteries is important, because it will allow the identification of plaque stability at an early stage.
Experimental Investigation of the Local Blood Flow Pattern in Stented Coronary Bifurcations
Authors: Morlacchi Stefano , Schmieg Jaime , Cooper Dan , Burzotta Francesco , Migliavacca Francesco , Vlachos Pavlos P.
Published: July 2013

Stenting procedures give the opportunity to treat cardiovascular diseases with a time saving, cost effective and minimally invasive procedure when compared to coronary artery by-pass, while ensuring improved clinical results than balloon angioplasty. However, despite their success, stenting procedures are still associated with some clinical problems like sub-acute thrombosis (ST) and in-stent restenosis (ISR). Several clinical studies associate these issues to the local blood flow alterations caused by stent implantation. In particular, hemodynamic forces like wall shear stresses induce endothelial cells to experience an enhanced proliferative attitude.
Database of Rabbit Aortic Geometries for Use in Computational Flow Studies
Authors: Peiffer V. , Rowland M. , Weinberg P. D. , Sherwin S. J.
Published: July 2013

Although risk factors for atherosclerosis such as genetic predisposition and diet are systemic, the disease develops non-uniformly throughout the arterial system. Lesions preferentially occur in curved arteries and branching regions and their distribution has been observed to change with age in both humans and rabbits [1]. If local blood flow patterns play a role in the initiation of atherosclerosis, the age-related differences may be a consequence of changes in the flow characteristics.
A Coupled Simulation of Spinal Cord Blood Flow and Cerebrospinal Fluid Motion in the Spinal Subarachnoid Space Based on In Vivo Measurements
Authors: Martin Bryn , Reymond Philippe , Balédent Olivier , Novy Jan , Stergiopulos Nikos
Published: July 2013

A preliminary coupled 1-D model of the systemic arterial tree and cerebrospinal fluid (CSF) system was constructed. The systemic tree model includes arteries greater than 2 mm in diameter and a simplified spinal cord vasculature. Coupling of the arterial tree and CSF system is accomplished by a transfer function based on in vivo cerebral blood flow (CBF) and CSF pulsation measurements in 17 young healthy adults. A 1-D tube model of the CSF in the spinal subarachnoid space (SSS) is formed based on in vivo measurements and used to determine flow and pressure along the SSS. The pressure and flow results in the CSF and systemic arterial tree are qualitatively and quantitatively similar to in vivo measurements in healthy subjects. The relative arrival time of blood pulsations in the spinal cord and CSF in the SSS is impacted by CSF system compliance and geometry. With low CSF system compliance the CSF pulsations arrive around the spinal cord before arterial pulsations and vice versa. Overall, the preliminary results support that geometric and mechanical properties of the CSF and cardiovascular system have an important impact on the flow and pressure environment and accent the importance to obtain in vivo measurements to improve modeling capabilities.
Visualization of Heat Shock Proteins for Quantifying Laser-Induced Thermal Ablation of Biological Tissues
Authors: Sajjadi Amir Y. , Mitra Kunal , Grace Michael S.
Published: July 2013

In laser-based therapeutics, it is important to ablate target tissue with minimal damage to surrounding healthy tissue. Unique properties of lasers allow precise and controlled ablation of tissue. Tightly focusing a short-pulse laser at the desired tissue region and controlling the exposure time by scanning the beam at the target can minimize corresponding collateral damage [1]. Even so, design of effective laser-based ablation procedures requires an understanding of the extent of laser-induced damage for given laser parameters (power, intensity, duration, etc.). Therefore, the instantaneous and effects over time of laser irradiation in live tissue should be studied. Instantaneous effects can be quantified by measuring thermal effects of laser irradiation on tissue. Depending on the application, threshold temperature is necessary to make permanent or temporary changes in tissue structure [1]. The temperature profile around the laser-irradiated region gives insight into radial energy spread and the extent of damage in tissue surrounding the ablation zone. In order to investigate the effects over time of laser irradiation of tissue, we studied the temporal expression patterns heat shock proteins (HSP), members of a class of proteins whose expression patterns change when cells are exposed to elevated temperature or other stressors [2]. We conducted experiments on live anesthetized mice to determine the spatiotemporal expression patterns of heat shock proteins in skin tissue after laser stimulation, both to understand the roles of heat shock proteins in laser-induced tissue damage and repair, and to develop heat shock proteins as tools to illustrate the extent of laser-induced damage and wound healing following irradiation.
Quantification of Dexterity Through a Novel Electronic Device
Authors: Cate Avery L. , Eng Dillon P. , Jackson Rachel W. , Scully Allison C. , Scully Jessica A.
Published: July 2013

Cerebral palsy affects movement, muscle tone, and coordination as a result of an injury to, or lesion of, the immature brain. One of the most common manifestations of cerebral palsy is spastic hemiplegia, which limits arm and hand use on the involved side of the body [1]. Many treatment options are available but a major clinical problem is how to evaluate the success of these treatment plans. Currently, video analysis is the standard used for evaluating dexterity of cerebral palsy patients. This requires trained clinicians to spend hours watching video of patients performing specified tasks in order to evaluate baseline dexterity and improvements throughout treatment. VICON is the current state of the art device for motion capture. It captures motion using multiple video cameras around the room and outputs the position data of many points through time. VICON machines must be carefully calibrated and are too bulky to be used throughout a clinic. VICON can also not show the upper extremity dexterity necessary for tracking many cerebral palsy patients’ progress. As can be seen, no portable, efficient, and quantitative dexterity test for cerebral palsy patients currently exists.
Designing a Patient-Specific Paediatric Mock Circulatory System to Study the Norwood Circulation
Authors: Biglino Giovanni , Schievano Silvia , Baker Catriona , Giardini Alessandro , Figliola Richard , Taylor Andrew M. , Hsia Tain-Yen
Published: July 2013

The Stage I of Fontan palliation for neonates with hypoplastic left heart syndrome, namely the Norwood procedure, aims to improve the flow of oxygenated blood in the systemic circulation while at the same time providing blood flow to the pulmonary circulation1. This surgical operation usually involves enlargement of the hypoplastic aorta by means of a patch, reconstruction of aortic coarctation and increase pulmonary flow. The latter point, at present, is achieved in three different ways: i) a Blalock-Taussig (BT) shunt from the innominate artery to the pulmonary artery, ii) an atrio-pulmonary shunt, referred to as Sano modification2 and iii) stenting the ductus arteriosus and banding the pulmonary arteries, referred to as “hybrid” Norwood3. In general, it is clear that the circulation following the Norwood procedure presents a very specific and complex arrangement.
Anterior Versus Posterior Fixation for an Isolated Posterior Facet Complex Injury in the Sub-Axial Cervical Spine
Authors: McLachlin Stewart D. , Rasoulinejad Parham , Bailey Stewart I. , Gurr Kevin R. , Bailey Chris S. , Dunning Cynthia E.
Published: July 2013

Traumatic injuries to the sub-axial cervical spine are relatively common, but can present with a wide-ranging spectrum of osteoligamentous damage. Guidelines for the appropriate treatment of these injuries are unclear with both operative (posterior and/or anterior approaches) and non-operative management advocated [1].
Local Shear Deformation in Whole Cartilage Explants Determined by Texture Correlation
Authors: Henderson Jonathan T. , Shannon Garrett , Yuen Kai , Neu Corey P.
Published: July 2013

Osteoarthritis (OA) is a prevalent disease, afflicting 27 million people in the United States alone [1]. OA is commonly thought of as “wear and tear” of the joints caused by repeated compression and shear strains. The mechanical contribution to the onset and progression of OA is unknown; however, it is likely a result of an imbalance of cartilage homeostasis, represented by a shift in biochemical and mechanical factors that typically maintain healthy joints [2]. Cartilage homeostasis results in part from cellular mechanotransduction events, i.e. the conversion of mechanical stimuli into a biochemical response.
A Partial Weight Bearing Reminder Device for Rehabilitation After Lower Extremity Surgery
Authors: Adams Elsbeth , Kiser Travis , LaPorte Rochelle , Roux Tracy , Stanistreet Eric , Storey Caitlin
Published: July 2013

Annually, in the United States there are roughly 352,000 incidents of hip fractures [1], 300,000 total hip replacements, and 270,000 total knee replacements, most of which are in adults over age 50 [2]. During rehabilitation, patients who have undergone total knee or hip replacement, cartilage cell transplant, cruciate ligament replacement, meniscus debridement, or complex fracture repairs may be instructed to restrict weight bearing. Partial weight bearing (PWB) includes everything from toe-touch to strict PWB (10–50% of the patients’ body weight), to full weight bearing as tolerated [3]. The restrictions following a hip replacement with a cement-less implant typically require a 6-week PWB regimen [4].
Towards a New Virtual Bench Testing Environment for Stents Assessment
Authors: Iannaccone F. , De Beule M. , Mortier P. , Segers P. , Verhegghe B.
Published: July 2013

Stenting has become a common procedure in clinical practice to treat arterial stenosis in coronary and peripheral vascular districts such as carotid or superficial femoral arteries.
Multi-Scale Modeling of Cancer Cell Migration and Adhesion During Epithelial-to-Mesenchymal Transition
Authors: Zielinski Rachel , Mihai Cosmin , Ghadiali Samir
Published: July 2013

Cancer is a leading cause of death in the US, and tumor cell metastasis and secondary tumor formation are key factors in the malignancy and prognosis of the disease. The regulation of cell motility plays an important role in the migration and invasion of cancer cells into surrounding tissues. The primary modes of increased motility in cancerous tissues may include collective migration of a group of epithelial cells during tumor growth and single cell migration of mesenchymal cells after detachment from the primary tumor site [1]. In epithelial cancers, metastasizing cells lose their cell-cell adhesions, detach from the tumor mass, begin expressing mesenchymal markers, and become highly motile and invasive, a process known as epithelial-to-mesenchymal transition (EMT) (Fig. 1) [2]. Although the cellular and biochemical signaling mechanisms underlying EMT have been studied extensively, there is limited information about the biomechanical mechanisms of EMT. In particular, it is not known how changes in cell mechanics (cell stiffness, cell-cell adhesion strength, traction forces) influence the detachment, migration and invasion processes that occur during metastasis.
Functional Diagnosis of Coronary Artery Stenoses Using Pressure Drop Coefficient: A Pilot Study in Humans
Authors: Kolli Kranthi K. , Effat Mohamed , Arif Imran , Helmy Tarek , Leesar Massoud , Back Lloyd H. , Banerjee Rupak K.
Published: July 2013

Optimization of cut-off values for diagnostic parameters in determining stenosis severity depends on coupling functional (hemodynamic) and anatomical data. In this study, we sought to investigate the functional diagnostic parameter (CDP; the ratio of trans-stenotic pressure drop to distal dynamic pressure) by correlating with FFR (ratio of distal to proximal pressure of a stenotic section) and CFR (ratio of hyperemic blood flow velocity to that of resting condition). A 0.014-inch dual sensor (pressure and Doppler velocity) guidewire was used in 9 patients to obtain pressure drop and velocity at hyperemia. Functional index CDP was assessed from measured hyperemic pressure drop and velocity. CDP correlated linearly and significantly with FFR and CFR. Indicating that, measurements of CDP can provide a better assessment of stenosis severity.
Innovative Design of a Venous Valve Intended for PIV Measurements
Authors: Van Der Smissen Benjamin , Van Canneyt Koen , Vermeulen Mathias , Bayley Martin , Narracott Andrew V. , Kaminsky Rado , Van Ransbeeck Peter , Verdonck Pascal R. , Segers Patrick
Published: July 2013

Today, hemodialysis is a common therapy to treat people with severe chronic kidney disease. This therapy strongly relies upon the vascular access that connects the patient’s circulation to the artificial kidney and which is obtained by surgically creating an arteriovenous fistula in the arm. However, due to the high flows involved at the venous side and elevated venous pressures, the functioning of venous valves in the arm is significantly disturbed, which too often bring about serious dysfunctions or complications in the patient [1–2]. To this end, research is done to improve the outcome of vascular access in patients on hemodialysis therapy by means of computational modeling [3]. One crucial challenge, however, is experimental validation of these computer models, preferably by using Particle Image Velocimetry (PIV) for simulations of flow fields. Yet, the task of modeling the venous valve is daunting because this valve functions at very low physiological pressure differences. Moreover, PIV requires an experimental model to be fully transparent. In this study, we propose an innovative design of a PIV-compatible venous valve model which has the ability to function at minimal pressure differences and which is able to generate valuable PIV data.
Failure Properties of the Simian Inferior Glenohumeral Ligament
Authors: Cassilly Ryan T. , Bunting Haley A. , Jin Brian , Ahmad Christopher S. , Bigliani Louis U. , Levine William N. , Gardner Thomas R.
Published: July 2013

Several animal models of the shoulder are currently in use, including the rat, sheep and goat, as a means to model shoulder pathology[1]. Cynomolgus monkeys have served as nonhuman primate models in several studies including monkey models of menopause [2], reproductive support structures [3] and the knee joint[4]. Anatomical comparisons of simian and human shoulders have demonstrated that the simian shoulder is similar to that of the human in both musculature and bony structures[5]. A preliminary study concluded that there exists a high degree of similarity between the simian and human glenohumeral joint (GHJ)[6]. Biomechanical studies have been performed on the human IGHL to determine its tensile properties [7] yet there are few comparative studies of the biomechanical properties of the simian and human GHJ. The objective of this study was to determine the geometric and tensile properties of the simian IGHL as compared to those of the human IGHL.
Estimation of In-Vivo Quadriceps Forces of the Knee: A Combined In-Vivo Patellofemoral Joint Kinematics Measurement and Finite Element Prediction
Authors: Kobayashi Koichi , Li Guoan
Published: July 2013

The load transfer mechanics across the patellofemoral (PF) joint during weight-bearing conditions is important for treatment of the knee pathology, such as knee OA, ACL deficiency as well as TKA. Many studies have characterized the PF joint reaction forces using equilibriums of the quadriceps and ground reaction forces at the knee joint [1,2,3]. However, this simplification does not consider other muscle function as well as 3D knee joint contact location when calculate moment arms of the involved forces.
Effect of Hormone Therapy on Tensile Strain of the Macaque Inferior Glenohumeral Ligament
Authors: Bunting Haley A. , Cassilly Ryan T. , Jin Brian , Ahmad Christopher S. , Bigliani Louis U. , Levine William N. , Gardner Thomas R.
Published: July 2013

The effect of hormone treatment on the material properties of ligaments has been extensively studied for the anterior cruciate ligament (ACL). However, there have been few studies on the effects of hormones on the material properties of the shoulder. Shoulder ligaments contribute to overall shoulder stability, and a change in ligament properties could contribute to a change in overall shoulder laxity. Cynomolgus monkeys have served as nonhuman primate models in studies examining the effects of hormone replacement therapy on the cardiovascular system, as well as serving as a model for menopause, reproductive support structures, the knee joint and shoulder joint. The cynomolgus macaques are commonly used for studies involving hormone replacement therapy because they have 28-day menstrual cycles with very similar hormonal patterns to that of women. This study uses female cynomologus macaque (Macaca fascicularis) monkeys as an animal model of the human shoulder to determine if estrogen has an effect on the strain distribution of the inferior glenohumeral ligament (IGHL).
Functional Tissue Engineering for Repair of Load-Bearing Musculoskeletal Tissues: History and Perspective
Authors: Butler David L.
Published: July 2013

Although who first defined tissue engineering and when this event first occurred in the 1980’s were only recently clarified [1], the enthusiasm for this treatment approach cannot be disputed. Traditional treatments have often been inadequate, leading clinicians and basic scientists to seek novel tissue engineering strategies using various cell, scaffold and bioreactor strategies (Figure 1). Tissue engineers routinely mix specialized as well as undifferentiated cells from various sources [2] with biologic, synthetic, and even hybrid scaffold biomaterials [3]. Cells can accelerate repair while scaffolds provide the tissue engineered construct (TEC) with mechanical and structural integrity and guide cell proliferation and differentiation and protein synthesis. Tissue engineers also design and adapt bioreactors to deliver mechanical and chemical stimuli to ensure viability and controlled cell preconditioning [4]. Once implanted, the fate of the repair rests on our ability to achieve desirable mechanical, structural, biological and clinical outcome measures. Unfortunately, many of these “design” or “success” criteria have not been agreed upon nor have the values been determined [5].
Tactile Surface Detector for a Prosthetic Hand
Authors: Lim Kai Yuen , Cook Emily , Kirkpatrick S. Philip , Palettas Neophytos
Published: July 2013

Currently, the number of amputees in the United States is estimated at 1.7 million people [1], and of those 1.7 million people, only approximately 300,000 are upper limb amputees [2]. However, the number of amputees is growing at a rate of more than 18,000 people per year [3]. Although the body powered and myoelectric prosthetics have been invented to provide a cosmetic solution and functionally allow the user to employ leverage or grasp an object, there are no marketed products which provide tactile feedback. Often amputees will not use their current prosthetics due to their unnatural feel. In terms of functional use of the prosthetics, reports show as low as 29% of amputees with prosthetics make use of the grasp feature [4]. Due to the general lack of user satisfaction, it is necessary to improve the prosthetic market by incorporating sensory feedback into upper limb prosthetics so that the user feels like they are using their own arm. With the incorporation of sensory-motor coordination, amputees’ reliance on visual information to be aware of the artificial hand and arm will be decreased, thereby, decreasing their cognitive load [5]. Additionally, due to the increased feedback from the arm regarding the environment, the amputee will be able to use their artificial limb more effectively and with more of native feel.
Experimentally Modeling Patient-Specific Fontan Circulations Including Respiration Effects Using a Mock Circulatory System
Authors: Chiulli John A. , Conover Timothy A. , Joshi Sharmad S. , Figliola Richard S. , Hsia Tain-Yen
Published: July 2013

The Fontan circulation is the result of a series of operations performed on children born with univentricular circulations (1). These congenital heart defects are uniformly fatal if left alone. After birth, an operation is performed to assure that the child receives enough blood flow to the lungs, but not too much in order to avoid pulmonary vascular disease. Once the child reaches 2–4 years of age, the child’s blood vessels are sufficiently large for the Fontan operation. The Fontan operation connects the great systemic veins directly to the pulmonary arteries, bypassing the right ventricle entirely. One method of the Fontan procedure, which is known as the total cavopulmonary connection (TCPC), achieves venous return to the pulmonary circulation without a ventricular power source. The load on the heart is reduced, and these patients can lead a normal life into adulthood; although late complications continue to prevent normal lifespan. One unique feature of the Fontan circulation is reliance of the inferior vena cava (IVC) flow on respiration, and flow reversal in the IVC and hepatic vein during expiratory phase of breathing (2). Hsia et al. (3) suggest that reducing flow reversal in the hepatic vein will improve the outcome of the Fontan operation. The goal of this study is to model experimentally the Fontan circulation for a variety of different patients using an adjustable mock circulatory system, which for the first time includes the influence of respiration.
Effect of Non-Uniform Tissue Configuration on Conductance Catheter Measurement for Arterial Lumen Sizing
Authors: Choi Hyo Won , Kassab Ghassan S.
Published: July 2013

A novel approach of two bolus injections of saline solutions has been proposed for conductance catheter measurement of cross-sectional area (CSA) and parallel conductance for medium size arteries [1–2]. The parallel conductance or current leakage through surrounding tissue is dependent on how differently the combined configuration of lumen, surrounding tissue, and conductance catheter forms an electric field. Arteries have a variety of surrounding tissue geometries and electrical conductivities depending on their anatomic situations. Specifically, coronary/peripheral arteries are often characterized by their superficial anatomic positions so that surrounding tissue has asymmetric configurations. Such notions highlight the need for addressing the impact of anatomically relevant tissue properties on the performance of conductance catheter measurement. In the present study, we computationally probe how asymmetric surrounding tissue thickness and/or inhomogeneous/anisotropic electric conductivity of tissue can modulate the electric field and hence accuracy of CSA measurement for a medium size artery.
Emulating the Interfacial Kinematics of CNS White Matter With Finite Element Techniques
Authors: Pan Yi , Pelegri Assimina A. , Shreiber David I.
Published: July 2013

Axonal injury represents a critical target for TBI and SCI prevention and treatment. Mechanical strain has been identified as the proximal cause of axonal injury, while secondary ischaemic and excitotoxic insults associated with the primary trauma potentially exacerbate the structural and functional damage. Many studies have been attempted to identify the states of stress and strain in white matter using animal and finite element models. These material models employed in finite element simulations of the central nervous system (CNS) of soft tissues heavily depend on phenomenological representations. The accuracy of these simulations depends not only on correct determination of the material properties but also on precise depiction of the tissues’ microstructure.
Continuity and Affine Fiber Kinematics in Biaxial Tension of the Supraspinatus Tendon
Authors: Szczesny Spencer E. , Peloquin John , Ilkhani-Pour Sarah , Cortes Daniel H. , Kadlowec Jennifer A. , Soslowsky Louis J. , Elliott Dawn M.
Published: July 2013

The human supraspinatus tendon (SST) exhibits strong heterogeneity in fiber alignment and material properties [1,2]. The relationship between fiber angle distribution and material properties has been previously described by a structurally based continuum model [3], which provided new quantitative structure-function relationships to explain the observed SST heterogeneity; however, in some locations and testing directions, the model predictions were not consistent with a continuum assumption [3]. More recent analysis of the change in fiber angle during loading showed that samples with less aligned fibers have less affine kinematics in uniaxial tensile loading [4]. That is, in uniaxial tensile testing, where the transverse edges freely contract, the fiber strain did not match the tissue strain. Because the SST is somewhat transversely constrained by surrounding rotator cuff structures in vivo and has distributed fibers to support multidirectional loading, the freely contracting edges of uniaxial tension may not appropriately constrain the tendon. Therefore, the objective of this study was to evaluate SST stress-strain behavior and affine deformation under biaxial tension. Specifically, if behaving as a continuum, we expected that applying a fixed boundary condition in the transverse direction would produce a higher apparent modulus, a smaller toe-region, and more affine fiber realignment than a free boundary condition.
Muscle Injury Attenuates BMP-2 Mediated Tissue Regeneration in a Novel Rat Model of Composite Bone and Muscle Injury
Authors: Willett Nick J. , Li M. Alice , Uhrig Brent A. , Warren Gordon L. , Guldberg Robert E.
Published: July 2013

Musculoskeletal diseases and injuries are a major burden on society, representing the most common cause of pain and impaired function worldwide. Composite injuries involving bone and the surrounding soft tissue comprise one of the most challenging musculoskeletal conditions to return to normal function. During repair of these injuries there is a loss of the synergistic interactions between adjacent tissues resulting in impaired bone regeneration. Additionally, local soft tissue ischemia may also be a contributing factor to increased infection rates observed in severe composite tissue injuries. Muscle has been implicated as a source for re-vascularization, osteoprogenitor cells and osteogenic factors, as well as a contributor to the biomechanical stimuli; however, associated studies have mostly been qualitative in nature, offering little insight into the mechanistic nature of the relationship of soft tissue to bone regeneration. Small animal models of critically sized bone defects are an efficient means to test engraftment strategies of novel constructs and therapeutics particularly in terms of functional restoration of a limb. Our lab previously developed a critically-sized rat segmental defect model with which we have quantitatively assessed bone regeneration using numerous constructs and therapeutic treatments [1]. Our objective was to develop a composite injury model by combining this segmental defect model with a muscle injury adjacent to the bone defect. We hypothesized that animals with a composite injury would have attenuated BMP-2 mediated tissue regeneration as compared to animals with a single tissue injury.
A Novel Mechanical Bioreactor System Allowing Simultaneous Strain and Fluid Shear Stress on Cell Monolayers
Authors: Van Dyke W. Scott , Nauman Eric , Akkus Ozan
Published: July 2013

The causes, mechanisms, and biology of bone adaptation have been under intense investigation ever since Julius Wolff proposed that bone architecture is determined by mathematical laws as a result of mechanical loading. How bone responds to mechanical loads by converting the mechanical signals into chemical signals is known as mechanotransduction. The in vivo environment of bone is complex, and most studies of cell-level phenomena have relied on the use of in vitro experiments using mechanical bioreactors. The main types of bioreactors are fluid flow shear stress, tensile and/or compressive strain, and hydrostatic pressure [1–2]. Of these bioreactors, the most intuitive mechanical stimulus for bone would be the tensile and compressive strain bioreactors. However, many researchers now claim that shear stress via interstitial fluid flow in the lacunar-canalicular porosity is the primary mechanosensory stimulus [3]. A handful of studies have attempted to compare the effects of both of these mechanical stimuli on osteoblasts, but these studies are lacking in two respects [4–6]. First, if both fluid flow and strain are performed in the same bioreactor, the magnitude of one loading mode is explicitly determined through constitutive equations, while the other is only estimated. Second, if the magnitudes of the loading modes are able to be explicitly determined they are performed in different bioreactors, providing the cells different extracellular environments. Therefore, a highly controllable dual-loading mode mechanical bioreactor, as described and characterized in this study, is a necessary tool to further understand the mechanotransduction of bone.
Disc Torsion Mechanics: Comparison of Animal Models to Human
Authors: Showalter Brent L. , Beckstein Jesse C. , Martin John T. , Beattie Elizabeth E. , Espinoza Orías Alejandro A. , Schaer Thomas P. , Vresilovic Edward J. , Elliott Dawn M.
Published: July 2013

The intervertebral disc plays a critical role in providing structural support to the spine while permitting extensive flexibility in a number of orientations. Axial rotation is a key parameter in spine function and torsional instability is related to spinal degeneration [1]. Animal models are integral components in many in vivo disc studies, however each animal varies in availability, size, cost, and scientific criteria such as cell phenotype and biomechanics. Selection of an appropriate animal model requires knowledge of the similarities and differences in biomechanical and biochemical factors between the model and human discs. Previous studies have often compared the characteristics of a single animal model with the human disc [2, 3]. However, variations in animal models and testing protocols between groups hinder comparisons and interpretations between different studies. This is especially relevant in torsion mechanics, where the magnitude of an applied compressive load and other testing parameters significantly affect the apparent torsional stiffness of the disc [4]. The objective of this study was to measure and compare the torsion mechanical properties of the human disc and 11 disc types from 8 mammalian species.