bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature Elevations in Implanted Prostatic Tumors in Mice During Magnetic Nanoparticle Hyperthermia: In Vivo Experimental Study
Authors: Attaluri Anilchandra , Ma Ronghui , Zhu Liang
Published: July 2013

In this study, we perform in vivo animal experiments on implanted prostatic tumors in mice to measure temperature elevation distribution in the tumor during magnetic nanoparticle hyperthermia. Temperature rises are induced by a commercially available ferrofluid injected to the center of the tumor, which is subject to an alternating magnetic field. Temperature mapping in the implanted prostatic tumors during the heating has illustrated the feasibility of elevating the tumor temperature higher than 50°C using only 0.1 cc ferrofluid injected in the tumor and under a relatively low magnetic field (3 kA/m). Ferrofluid infusion rates during intratumoral injection may affect nanoparticle spreading in tumors. Using a very slow infusion rate of 5 μ1/min results in an average temperature elevation in tumors 27°C above the baseline temperatures of 37°C. However, the temperature elevations are barely 14°C when the infusion rate is 20 μl/min. Our results suggest a more confined nanoparticle distribution to the injection site using smaller infusion rates.
Noninvasive Prediction of the In Vivo Forces on the Lumbar Intervertebral Discs: A Validation Study
Authors: Wang Shaobai , Park Won Man , Li Guoan
Published: July 2013

Evaluation of the forces on the lumbar intervertebral discs (IVDs) is critically important since it closely relates to biomechanics, pathology, prosthesis design and tissue engineering. It remains a big challenge to noninvasively predict the in vivo forces on the IVD. Using our previously established dual fluoroscopic imaging system (DFIS) [1], motion of the vertebrae can be accurately obtained. We proposed to use the kinematics from DFIS as inputs into FE model to calculate the forces on the IVD. In this study, we validated the technique by testing an IVD on a 6DOF robotic system under applied loads and under DFIS. A subject specific FE model of IVD was built. Forces and moments were predicted and compared to the applied loads.
Risk of Rupture in Coronary Vulnerable Plaques: Fluid-Structure Interaction Studies Using Patient Based Micro-CT and IVUS Measurements
Authors: Liang Xuan , Rambhia Suraj , Xenos Michalis , Alemu Yared , Maldonado Natalia , Kelly Adreanne , Lavi Ifat , Einav Shmuel , Weinbaum Sheldon , Cardoso Luis , Bluestein Danny
Published: July 2013

Fluid-structure interaction (FSI) simulations were conducted in patient-specific coronary vulnerable plaque (VP) geometries reconstructed from Micro-CT and intravascular ultrasound (IVUS), in order to study the effects of microcalcification (micro-Ca), anisotropic vessel properties, and hypertension on plaque vulnerability.

The models reconstructed from IVUS included vessel wall, fibrous cap, lipid core and large calcifications. A model reconstructed post mortem from a coronary specimen of a patient with confirmed VP was scanned using high resolution micro-CT. This enabled capture of micro calcifications embedded in the VP fibrous cap in addition to the plaque components mentioned above. Regions susceptible to tissue failure were studied. The thin fibrous cap regions of the plaque were characterized by high stress concentrations. The presence of single or multiple micro-calcified spots embedded within the fibrous cap was studied as well. Micro-Ca significantly enhanced stresses within the fibrous cap, significantly contributing to the risk of rupture.
Temperature Elevations in Implanted Prostatic Tumors During Laser Photothermal Therapy Using Nanorods
Authors: Zhu L. , Attaluri A. , Manuchehrabadi N. , Cai H. , Edziah R. , Lalanne E. , Bieberich C. , Ma R. , Johnson A.
Published: July 2013

Gold nanoshells or nanorods are newly developed nanotechnology in laser photothermal therapy for cancer treatments in recent years [1–10]. Gold nanoshells consists of a solid dielectric nanoparticle core (∼100 nm) coated by a thin gold shell (∼10 nm). Gold nanorods have a diameter of 10 nm and an aspect ratio of approximately four. Nanorods may be taken up by tumors more readily than nanoshells due to nanorods’ smaller size. By varying the geometric ratio, both nanoshells and nanorods can be tuned to have strong absorption and scattering to a specific laser wavelength. Among a wide range of laser wavelengths, the near infrared (NIR) laser at ∼800 nm is most attractive to clinicians due to its deep optical penetration in tissue. Therefore, the tissue would appear almost “transparent” to the 800 nm laser light before the laser reaches the nanoshells or nanorods in tumors, with minimal laser energy wasted by the tissue without the nanostructures. The laser energy absorbed in an area congregating by the nanostructures is transferred to the surrounding tissue by heat conduction. This approach not only achieves targeted delivery of laser energy to the tumor, but also maximally concentrates a majority of the laser energy to the tumor region.
The Effect of Oxidation on the Mechanical Response of Elastin Isolated From Porcine Aorta
Authors: Stephen Beth , Good Theresa A. , Washington Joseph B. , Topoleski L. D. Timmie
Published: July 2013

Arteries play a critical role in human health, and consequently are extensively studied as a biological component. However, the primary function of arteries is mechanical; they conduct blood through the body. Therefore, arteries, and their structure-function relationships, must also be studied as biomaterials.
Education Activities of Bioengineering for Undergraduate Students at UMBC
Authors: Zhu Liang , Arola Dwayne , Eggleton Charles , Spence Anne
Published: July 2013

Recent developments in micro- and nano-technology have become the primary thrust of many new research opportunities in bioengineering to provide better imaging, diagnosis, therapeutic therapy, and monitoring progression of various diseases. Biology and Chemistry are becoming highly quantitative disciplines, dealing with deeply complex interacting factors. Engineered systems are increasingly integrating biological operability and capabilities into traditional methodology. Light matter interactions traditionally employed in Optical Physics has generated new fields in Biophysics and Bioengineering. These are unique challenges often requiring interdisciplinary collaborations among researchers with diversified expertise. Therefore, it is important to educate the next generation of undergraduate students to possess the technical knowledge within their core discipline, to cultivate opportunities for interdisciplinary problem solving and to prepare them for an industrial or graduate environment involving interdisciplinary research.
Localized Cooling Device for Myocardial Tissue Salvage
Authors: Akers Jennifer E. , Merrill Denise R. , Nilsen Todd J. , Koomalsingh Kevin J. , Minakawa Masahito , Shuto Takashi , Gorman Joseph H. , Gorman Robert C. , Gillespie Matthew J. , Merrill Thomas L.
Published: July 2013

The primary goal in treating heart attack is to restore blood flow to blocked areas of the heart. However, even after blood flow is restored, injury can occur as a result of a complex cascade of mechanisms following the reintroduction of flow, aptly referred to as reperfusion injury. Studies show that reperfusion injury is accountable for up to 50% of cell death following an ischemic period [1]. Adjunctive therapies are needed to reduce reperfusion injury.
Mechanical Flow Restoration in Acute Ischemic Stroke: A Model System of Cerebrovascular Occlusion
Authors: Chueh J. Y. , Wakhloo A. K. , Gounis M. J.
Published: July 2013

Stroke is the leading cause of disability and the third cause of death in the United States. About 20% of acute ischemic strokes (AIS) are caused by a large artery occlusion, and restoration of blood flow in a reasonable time is the principle goal of treatment. FDA-approved recombinant tissue plasminogen activator (tPA) administration for treatment of stroke is efficacious, but it has short treatment time window and risk of symptomatic hemorrhage that result in only 3–5% patients of who receive this treatment. Alternatively, endovascular treatment using thrombectomy devices, MERCI and Penumbra systems, has been cleared by the FDA. Without adjunctive therapies, the recanalization rate and clinical outcome associated with these devices could be improved.
A Comparison of the Mechanical Properties of the Goat Temporomandibular Joint Disc to the Mandibular Condylar Cartilage in Unconfined Compression
Authors: Hagandora Catherine K. , Almarza Alejandro J.
Published: July 2013

The temporomandibular joint (TMJ) is a synovial, bilateral joint formed by the articulation of the condyle of the mandible and the articular eminence and glenoid fossa of the temporal bone. The articulating tissues of the joint include the TMJ disc and the mandibular condylar cartilage (MCC). It is estimated that 10 million Americans are affected by TMJ disorders (TMDs), a term encompassing a variety of conditions which result in positional or structural abnormalities in the joint. [1] Characterization of the properties of the articulating tissues of the joint is a necessary prequel to understanding the process of pathogenesis as well as tissue engineering suitable constructs for replacement of damaged joint fibrocartilage. Furthermore, the current literature lacks a one-to-one comparison of the regional compressive behavior of the goat MCC to the TMJ disc.
Device to Lift a Person From the Ground to Wheelchair Height
Authors: Thomas Jason , Doughty Andrew , Perkins David , Wells Eric , Pourazady Mehdi , Hefzy Mohamed Samir
Published: July 2013

The goal of this project was to develop a device to assist a paraplegic or quadriplegic in moving from the floor to a wheelchair with the assistance of only one person. A collapsible and portable device resembling a chair into which the individual can be strapped was developed for this purpose. The device separates into four pieces: the high back, the right leg with an attached foot rest, the left leg with an attached seat, and the top handle. The right and left legs were curved. Two ratcheting rear legs are placed on the back side of the unit for additional support. The device and its components are shown in Figures 1 and 2, respectively. The unit is collapsible into 40″ by 18″ as shown in Figure 3. During use, the client would lay on their side on the floor with their legs bent as if sitting in an imaginary chair. The unfolded and assembled chair would then be placed next to them and safety straps would be placed around the client’s chest, waist, and shins. The client and chair would then be rolled so that the client would be lying on their back. Once in this position, the assistant could lift the tall back of the chair to bring the client to an upright sitting position at wheelchair height.
Anisotropic Inverse Mechanics Identifies Regional Changes in Mechanical Anisotropy During Remodelling of Fibroblast-Populated Collagen Cruciforms
Authors: Raghupathy Ramesh , Lake Spencer P. , Sander Edward A. , Witzenburg Colleen , Barocas Victor H.
Published: July 2013

Most elastographic methods applied to soft tissues assume either isotropy or homogeneity in the sample. While this assumption is valid in specific cases, general methods that can identify regional changes in mechanical anisotropy have many advantages. Chiefly, such methods could quantify regional anisotropic material behavior on intact tissue samples especially when the tissue is heterogeneous and too small for standard tests. In this study we use an inverse mechanics method which handles both anisotropy and heterogeneity to track changes in mechanical anisotropy associated with remodeling in cell-compacted collagen tissue equivalents (TE), which are then compared with measurements from polarimetry to estimate the method’s accuracy.
Biotransport: Fluid Mechanics, Heat and Mass Transfer
Authors: Ayyaswamy P. S.
Published: July 2013

There is an important need for comprehensive courses related to Biotransport to be offered at the undergraduate and graduate levels in US Universities. These courses must emphasize both theory and applications. At present, although there are many different descriptions of courses related to biotransport that are available in catalogues of various departments, it is clear that a systematic approach is needed to develop a formally comprehensive set of guidelines and course material descriptions in this that will be useful for the student body at large. As a part of this discussion, a comprehensive model course description is displayed in the following.
Modeling of Isoelectric Focusing of Type-I Collagen Molecules Under Uniform Electric Field
Authors: Uquillas Jorge Alfredo , Akkus Ozan
Published: July 2013

Our laboratory developed an electrochemical method which transforms collagen solutions to solid state material by densification and unidirectional alignment of molecules [1] based on the principles of isoelectric focusing (IEF). Randomly oriented molecules at the onset migrate to the isoelectic plane when current is applied to the solution. However, the driving forces behind the focusing phenomena are not fully understood.
Polyvinyl Alcohol Hydrogels Functionalized With Organic Boundary Lubricant for Use as a Low Friction Cartilage Substitute
Authors: Blum Michelle M. , Ovaert Timothy C.
Published: July 2013

To solve the materials selection and tribological problems of compatibility, tissue damage, and wear resulting from sports injuries in younger and active populations where total joint replacement is highly undesirable, alternate biomaterials are being developed to repair or replace focal defects in articular cartilage so that the natural life of an articulating joint can be extended. The tribological concerns are most pressing. Articulating joints are not continuously separated by a fluid film. During motionless periods and impact loading conditions, and even in select individuals during the normal gait cycle, the contacting surfaces are not separated by a fluid film and are in the boundary lubrication (BL) regime. Research has shown that BL must occur at some point in time, if not during the majority of the motion cycle [1]. In this regime, the load is supported mainly by a molecular-scale boundary film and the surface asperities. Thus, failure of a synthetic replacement, or the cartilage itself on which it potentially articulates, would occur under BL conditions.
Developing a Framework for Computerized Training of Cryosurgery Based on Finite Elements Analysis
Authors: Keelan Robert , Shimada Kenji , Rabin Yoed
Published: July 2013

As a part of an ongoing effort to develop computerized training tools for cryosurgery—the destruction of undesired tissues by freezing—the current study focuses on developing an efficient framework of applying a commercially available finite-element (FE) code to meet simulation runtime applicable to clinical training. Computerized training is focused on a minimally invasive procedure with prostate cryosurgery as a development model.
Neck Muscle Strength Measured During Vigorous Head Shaking
Authors: Funk James R. , Watson Richard A. , Cormier Joseph M. , Bain Charles E. , Guzman Herb , Bonugli Enrique
Published: July 2013

Neck muscle activation is believed to generally protect against whiplash and head injury in automotive impacts and sports activities. When the torso is struck, active tensing of the neck muscles may prevent the neck from rotating excessively due to the inertia of the head. In this scenario, neck muscle tension may also reduce the severity of a secondary head impact occurring after the primary impact with the body. In a direct impact to the head, it has been hypothesized that active neck muscle tension may reduce the acceleration experienced by the head by increasing its effective mass.
Influence of Microcalcifications on Stress Development Within a Vulnerable Plaque’s Cap
Authors: Aronis Ze’ev , Kanka Erez , Massarwa Eyass , Haj-Ali Rami , Einav Shmuel
Published: July 2013

Vulnerable plaques are inflamed, active, and growing lesions which are prone to complications such as rupture, luminal and mural thrombosis, intraplaque hemorrhage, and rapid progression to stenosis. Despite major advances in the prevention and treatment of this disease, it remains the leading cause of morbidity and mortality worldwide, accounting for 30% of all deaths globally [1]. The importance of stress/strain distribution is now well recognized in vascular pathophysiology, specifically in the mechanisms of plaque rupture. Finite element modeling (FEM) and advanced fluid structure interaction (FSI) studies can better characterize coronary stenosis coupling constitutive equations. Mechanical factors such as stress concentrations within a plaque (material fatigue), lesion characteristic (location, size, and composition), and flow patterns are involved in rupture of plaques. Assessment of local mechanical characteristics caused by plaque structure is important for identifying vulnerable plaques and may improve final estimation of the risk for coronary syndrome.
Comparison of Interface Stresses and Strains for Onlay and Inlay Unicompartmental Tibial Components
Authors: Walker Peter S. , Parakh Dhiraj S. , Chaudhary Miriam E. , Wei Chih-Shing
Published: July 2013

There are two main designs used for unicompartmental tibial components. The first design, an all plastic component called an inlay, preserves bone on the outer edge of the tibia which is feasible using a robotically-controlled burring tool. Also, the depth of resection is small, preserving the strongest cancellous bone which is near the surface. The second design, called an onlay, resects the entire condyle and includes a metal backed plate which rests on the resected tibia. This component requires more bone removal but metal-backing has previously been shown to distribute the load more uniformly. The purpose of this study was to investigate the hypothesis that while inlay components require less bone removal, the peak stresses and strains at the surface of the bone will be greater when compared to onlay components.
The Effect of Synthetic Ice Blockers on Thermal Expansion of the Cryoprotective Cocktail DP6
Authors: Eisenberg David P. , Rabin Yoed
Published: July 2013

Cryopreservation is the only alternative for long-term preservation of high-quality biomaterials, where the availability of reliable techniques for preservation of multicellular structures and organs represents an unmet medical need. Developing cryopreservation techniques revolves around controlling the formation of ice crystals, which is known to be lethal to living cells. Cryopreservation is typically achieved in the presence of cryoprotective agents (CPAs), which exhibit a dramatic increase in viscosity with decreasing temperature. Subject to high cooling rates, the rapidly elevating viscosity of the CPA suppresses ice crystallization and promotes vitrification (vitreous means glassy in Latin). Unfortunately, available CPAs are known to be toxic at the relevant concentrations which permit vitrification. One potential method of reducing CPA concentration, and thereby achieving conditions more favorable to the tissue, is with the introduction of the so-called synthetic ice blockers (SIBs)—the subject matter of the current study.
Mechanical Properties of Injured Human Cervical Spine Ligaments and Corresponding Effect on Spinal Kinematics
Authors: Leahy P. Devin , Puttlitz Christian M.
Published: July 2013

The assessment of cervical spine instability following traumatic injury is controversial [1, 4, 5, 8]. Typical definitions of cervical instability are based on the presence of several key detectable injuries using simple radiographs, computed tomography (CT), and magnetic resonance (MR) imaging. Although these imaging modalities have been shown to be relatively reliable for detection of fractures and very large soft tissue injuries, they are largely deficient for determining the presence of smaller soft tissue injuries, such as hyperstrained ligaments [1, 3]. Soft tissue injuries of this nature may be revealed with dynamic range of motion (ROM) assessment, such as a flexion and extension test with radiography. However, these tests are currently inadequate for determining the existence of specific injuries. Cervical soft tissue injuries demand further analysis, given the risk of severe and permanent neurological impairment that may accompany these injuries [2, 5].
High Flow Rate Circulating Tumor Cell Capture Device
Authors: Park Taehyun , Park Daniel Sangwon , Murphy Michael C.
Published: July 2013

Circulating tumor cells (CTCs) may become a new foundation for early stage cancer diagnosis requiring minimal patient effort [1]. This approach can overcome the limitations of current diagnostic technologies, including computer-aided tomography (CT), magnetic resonance imaging (MRI), X-ray mammography, and ultrasound (UR) which can detect only highly calcified tumors at relatively high cost. Several studies have demonstrated CTC capture using microfluidic devices to identify the presence of human breast cancer, and the CellSearch™ immunomagnetic system (Johnson & Johnson, New Brunswick, NJ) is approved by the Food and Drug Administration (FDA) for monitoring post-treatment therapy, but all of the systems reported have either a long diagnosis time or unacceptable capture rates [2, 3]. CTCs in human peripheral blood are very rare events, typically 1 ∼ 2 CTCs in 1 mL of circulating blood. This low concentration of CTCs requires a large sample volume (∼7.5 mL) to ensure detection. However, current affinity-based microfluidic devices for cell capture usually operate at very low flow rates to increase the capture rate. Therefore, developing high flow rate microfluidic devices for CTC capture is essential and challenging. A new concept of high flow rate device is introduced, simulated, and tested at high flow rates.
Effects of Knee Flexion on Stented Peripheral Arteries: A Computational and In Vitro Study
Authors: Ghriallais Ríona Ní , Bruzzi Mark
Published: July 2013

The femoropopliteal (FP) artery is a branch of the femoral artery, the main artery in the upper leg, providing blood to all muscles and superficial tissues in the thigh. It is the largest of the femoral artery branches, composed of the superficial femoral artery (SFA) in the proximal region and popliteal artery (PA) in the distal region which runs below the knee. It is characterised by its tortuous geometry, associating a high atherosclerotic plaque burden with it. However, due to the dynamic forces of the SFA and PA, peripheral stents are reported to have the highest failure rates, predominantly due to bending [1]. Worst case bending can be seen in regions of the SFA/PA behind and just above the knee [2] and this is detrimental to stent patency.
Quantitative Analysis of Collagen Distribution in the Aorta Using Birefringence Imaging
Authors: Sugita Shukei , Matsumoto Takeo
Published: July 2013

Since collagen is one of the major components of the aortic wall and is the toughest in the wall, it may play a vital role in the strength of the aorta. For the quantification of the amount of collagen, its area fraction has been used in histological analysis. Although this method is convenient to know the distribution of collagen, it cannot be used for precise quantification of the collagen volume, because it is hard to determine the local thickness of collagen in the sample from its color due to unsteadiness of the staining density.
Optimal Boundary Conditions for the Multi-Scale Finite Element Analysis of Fibrous Scaffolds for Heart Valve Tissue Engineering
Authors: Argento Giulia , Oomens Cees W. J. , Baaijens Frank P. T.
Published: July 2013

Although existing valve prostheses generally have resulted in enhanced survival and quality of life, they have serious drawbacks that limit their long-term efficacy. These include thrombo-embolic complications requiring lifelong anticoagulation in case of mechanical valves, limited durability due to calcification and structural failure in case of bioprostheses and structural deterioration and shortage of donor material when using a homograft. In addition, the inability to grow restricts the application of currently available prostheses in pediatric patients. Heart valve tissue engineering (TE) is a promising alternative to create living valves that may have the capacity to grow and remodel. The traditional TE approach requires the growth of tissue on a scaffold in a bioreactor before implantation (1).
The Relationship Between In-Vivo Glenohumeral Joint Motion and Joint Morphology in Rotator Cuff Repair Patients and Healthy Control Subjects
Authors: Peltz Cathryn D. , Ciarelli Kristin , Haladik Jeffrey A. , McDonald Michael J. , Ramo Nicole , Moutzouros Vasilios , Bey Michael J.
Published: July 2013

Rotator cuff tears are a common condition that adversely affect function and quality of life. Altered glenohumeral joint (GHJ) motion is believed to contribute to the development of rotator cuff tears. Previous research has demonstrated relationships between in-vivo joint motion and bony morphology (particularly in the knee [e.g., 1]), and similar relationships have been reported in cadaveric shoulder studies [2, 3]. However, the extent to which these relationships exist under in-vivo conditions or if these relationships are altered in shoulders with pathologic conditions is not known. Thus, the objective of this study was to assess the relationship between glenoid/humerus morphology and in-vivo GHJ motion in healthy control shoulders and rotator cuff repair patients. We hypothesized that a relationship exists between glenoid/humerus morphology and GHJ motion in healthy control shoulders, but that this relationship is altered in rotator cuff patients.
In Silico Design and In-Vivo Analysis of the Pediaflow™ Pediatric Ventricular Assist Device
Authors: Maul Timothy M. , Antaki James F. , Wu Jingchun , Kim Jeongho , Kameneva Marina V. , Olia Salim E. , Wearden Peter D. , Kocylidirim Ergin , Borovetz Harvey S.
Published: July 2013

Mechanical circulatory support for the smallest newborn pediatric patients has historically been limited to extracorporeal membrane oxygenation, which can only provide several days to weeks of full cardiac support; far short of the median waiting time for pediatric heart transplantation of nearly three months [1]. Recently, new technologies have been developed, including the PediaFlow pediatric ventricular assist device, to address this need. The PediaFlow device is a magnetically levitated (mag lev), mixed flow turbodynamic blood pump which has been developed in large part in silico using CFD-based inverse design optimization and closed form rotor dynamics models [2, 3]. Each prototype undergoes a series of in vitro and in vivo tests to verify the accuracy of the simulations in predicting performance and biocompatibility. The overall goal is continued refinement and progress towards an implantable pump that produces 0.3 −1.5 L/min for up to 6 months in pediatric heart failure patients from 5 to 15 kg. We describe here the design principles and test procedures for the first three prototypes as well as the predicted performance for a fourth prototype currently being prepared for testing (Figure 1).
Rightward and Leftward Head Rotation Influence the Geometric Features of the Healthy Carotid Bifurcation
Authors: Aristokleous Nicolas , Seimenis Ioannis , Papaharilaou Yannis , Georgiou Georgios , Brott Brigitta C. , Anayiotos Andreas S.
Published: July 2013

Posture changes may influence the geometry and hemodynamics of the carotid bifurcation [1]. As a result, head rotation may cause geometric changes that alter the hemodynamic variables previously cited to correlate with the development of atherosclerosis. Such variables include oscillating wall shear stress (WSS) and particle residence times. Glor et al. [1] had reported changes in the right carotid bifurcation geometry with leftward rotation of the head. We have previously reported that geometric differences in the right and left carotid bifurcation occur with a rightward rotation of the head [2]. To investigate the geometric changes in the carotid geometry that occur in the prone sleeping position with rightward and leftward head rotation, we have performed studies in two healthy young volunteers. We defined specific geometric parameters of the carotid bifurcation, such as bifurcation angle, internal carotid artery (ICA) angle, ICA planarity angle, in-plane asymmetry angle, tortuosity, curvature, area and diameter ratios, and compared their corresponding values in three head postures: 1) the supine neutral position, 2) the prone sleeping position with head rotation to the right (∼80 degrees), and 3) the prone sleeping position with head rotation to the left (∼80 degrees).
Automated Virtual Placement and Evaluation of Tibial Components for Knee Arthroplasty
Authors: Dai Yifei , Wentorf Mary S. S. , Bischoff Jeffrey E.
Published: July 2013

The ability of tibial tray component shapes to appropriately fit boney geometry is an important aspect of implant design in total knee arthroplasty. Overhang of components in the knee has been associated with soft tissue damage and joint pain [1,2]. Good coverage establishes stability through adequate cortical bone support of the tray component, and reduces the likelihood of loosening and subsidence [3–5], and therefore serves as a key factor in component fixation, especially in those that rely on biological growth into porous component backings such as Trabecular Metal™ Material. More importantly, rotational malalignment of the tibial tray can disrupt the natural kinematics and implant longevity [6]. Previous studies investigated coverage of multiple tibial trays on digitized bone resection contours [1,7]. However the methodology for rotational alignment during implantation was not identified. Although rotational alignment has been investigated in numerous studies, most of the studies were carried out by either investigating the impact of malalignment [6], or assessing different definitions of the tibia rotational axis [8]. No correlation between the size of the rotational alignment window and the amount of coverage has been shown.
Neuronal Precursor Cell Proliferation on Elastic Substrates
Authors: Previtera Michelle L. , Hui Mason , Desai Malav , Verma Devendra , Schloss Rene , Langrana Noshir A.
Published: July 2013

Numerous stem cells therapies have been studied for the replacement of damaged neurons due to spinal cord injury. Our laboratory’s goal is to design an implantable platform for spinal cord neuron (SCN) proliferation and differentiation in order to replace damaged neurons in the injured spinal cord. Based on previous literature, we suspect we can promote neuronal precursor cell (NPC) proliferation and differentiation utilizing elastic matrices.
The Computational Evaluation of a Locking Plate Fixation: Locking Versus Far Cortical Screws
Authors: Moazen Mehran , Jones Alison C. , Mak Jonathan , Jin Zhongmin , Wilcox Ruth K. , Tsiridis Eleftherios
Published: July 2013

Locking plates have gained increased popularity for the treatment of various types of fractures. However, these constructs can provide high stiffness fixations that can potentially fail. Therefore, several methods have been proposed to reduce the stiffness of these fixations in order to promote secondary bone healing via callus formation. One of the most recent concepts that has been proposed to reduce the stiffness of locking plates is the application of “far cortical screws”. This approach has been experimentally tested in vitro models of the femur and its application in animal models has shown promising results.
The Role of Cells in Collagen Modeling in Tissue Engineered Constructs: A Theoretical Framework
Authors: Soares Ana L. F. , van Vlimmeren Marijke A. A. , Oomens Cees W. J. , Baaijens Frank P. T.
Published: July 2013

Mechanical loading protocols in tissue engineering (TE) aim to improve the deposition of a properly organized collagen fiber network. These conditioning protocols can result in tissue compaction [1], which may lead to loss of functionality of the tissue construct. A balance between the collagen deposition and compaction is desirable, yet difficult to achieve, due to the nonlinear coupling between mechanical loading, collagen modeling and compaction.
Evaluation of Lower Limb Injury Mitigation Techniques for High Velocity Impacts With the Mil-LX
Authors: Serres Jennifer L. , Jones Dan V. , Tannous Rabih E. , Dau Nathan , Bir Cynthia A.
Published: July 2013

Improvised Explosive Devices (IED) and landmines present a significant threat to mounted troops currently serving in Iraq and Afghanistan. As a result of these threats, a substantial number of lower limb injuries are sustained by service members. Due to this reality, a critical factor in military vehicle design is the mitigation of lower limb trauma. Past studies have shown that the standard Hybrid III and THOR-LX are not biofidelic in military axial loading conditions (up to 12 m/s). Both of these surrogates over predict axial forces compared to Post Mortem Human Specimens (PMHS) [1]. As a result, a new surrogate was developed, Mil-LX (Military Lower Extremity), that matches the PMHS response for axial loading of the lower leg up to 12 m/s [2,3]. While injury mitigation techniques, such as energy absorbing mats, foot rests, and isolation floors, have been effective in reducing lower extremity injuries in live fire test events, there are several variants of each of these methods. Additionally, it has also been suggested that the positioning of the lower limbs may affect the load sustained by these extremities [4].
Effects of ACL Reconstruction Techniques on the Kinematics of the Knee in a Computational Knee Model
Authors: Bloemker Katherine H. , Guess Trent M.
Published: July 2013

This study examines the effects of different Anterior Cruciate Ligament (ACL) reconstruction techniques on computational multibody knee models. The knee models were derived from two cadaver knees that underwent simulated walk cycles while the kinematics of the knee geometries were collected in a dynamic knee simulator. Once the computational models performed well compared to experimental data, multiple simulated ACL reconstruction surgeries were done on each model. For each simulated reconstruction technique, overall knee kinematics was compared to the experimental cadaver results and anterior-posterior movement of the tibia relative to the femur was compared to the original, intact computational model. The factors examined were ACL reconstruction method, adding preload to the reconstruction element, and reconstruction element type.
The Effect of Muscle Loading on Internal Mechanical Parameters of the Lumbar Spine: A Finite Element Study
Authors: Gadomski Benjamin C. , Rasmussen John , Puttlitz Christian M.
Published: July 2013

The human spine experiences complex loading in vivo; however, simplifications to these loading conditions are commonly made in computational and experimental protocols. Pure moments are often used in cadaveric preparations to replicate in vivo loading conditions, and previous studies have shown this method adequately predicts range of motion behavior (1, 2). It is unclear what effect pure moment loading has on the tissue-level internal mechanical parameters such as stresses in the annulus fibrosus and facet contact parameters. Recent advances in musculoskeletal modeling have elucidated previously unknown quantities of the musculature recruitment patterns such as times, forces, and directions. The advancements are especially relevant in cases of surgical intervention because the spinal musculature has been reported to play a critical role in providing additional stability to the spine when defects such as discectomy and nucleotomy are involved (2). Thus, the aim of the study was to determine the importance of computational loading conditions on the resultant global ranges of motion, as well as the tissue-level predictions of annulus fibrosus stresses, and facet contact pressures, forces, and areas.
Stochastic Modeling to Identify the Normal Response of an Optic Nerve Head to Small Increases in Intraocular Pressure
Authors: Sigal Ian A. , Grimm Jonathan L.
Published: July 2013

Glaucoma is one of the leading causes of blindness worldwide. Although elevated intraocular pressure (IOP) is the main risk factor for the development of the disease, its role remains unclear. Several studies have explored the hypothesis that an IOP-induced altered biomechanical environment within the optic nerve head (ONH), and the lamina cribrosa in particular, may contribute to disruption of the retinal ganglion cell axons, and the subsequent loss of vision associated with glaucoma [1–3]. Identifying the normal ONH biomechanical environment, however, has proven challenging. This has been in part because of the difficulty in accessing the ONH directly for experimentation, but also because of the difficulty in reconstructing models of the relevant structures with which to estimate its biomechanics. Few models represent only a small subset of the possible variations in ONH characteristics in a population, with the consequent lack of statistical power in the predictions.
Shoulder Rotation Laxity is Related to Pitching Mechanics
Authors: Wang Hongsheng , Eaton Koco , Zheng Nigel
Published: July 2013

According to the 2002 Major League Baseball Disability Analysis, almost 70% of players on the disabled list are pitchers and throwing arm related injuries account for 53% of all disabled list placements. To reach a high ball speed, pitchers cock, or excessively externally rotate their pitching arm to or near an extreme ROM of 180° [1]. The shoulder is then immediately internally rotated to an astonishing 7000°/s after the leading foot contact. The excessive external rotation ROM and astonishing internal rotation velocity are thought to contribute to injury [2]. Repeated exposure to the excessive ROM and large shoulder loads may cause excessive laxity to the anterior shoulder and/or damage the soft tissue [2]. This can lead to shoulder instability and excessive humeral head translation that may cause impingement [3]. Therefore, the mobility and stability of the thrower’s shoulder are extremely relevant to performance and injury prevention.
Magnetoelastic Materials as Novel Bioactive Coatings to Improve Integration of Percutaneous Implants
Authors: Holmes Hal , Vlaisavljevich Eli , Tan Ee Lim , Ong Keat G. , Rajachar Rupak M.
Published: July 2013

Fibroblastic activity is an innate function of the host response. In the presence of many percutaneous biomedical implants, this activity becomes uncontrollable, resulting in significant fibrous overgrowth at the soft tissue-implant interface [1]. The aberrant cell growth associated with pathological fibrosis can lead to extensive remodeling and excessive synthesis of extracellular matrix (ECM) components, preventing proper integration [2]. Furthermore, these areas of irregular fibrotic activity can also serve as sites for opportunistic infection [3]. In brief, interfacial fibrosis is often responsible for the ultimate failure and increased risk of infection of percutaneous biomedical implants.
Characterizing the Ex-Vivo Mechanical Properties and Corresponding In-Vivo Impact of Synthetic Urogynecological Meshes
Authors: Feola Andrew J. , Moalli Pamela , Stein Suzan , Jallah Zegbeh , Shepherd Jon , Abramowitch Steven D.
Published: July 2013

Pelvic organ prolapse and urinary incontinence are common conditions in women that significantly diminish quality of life. With roughly 225,000–280,000 women requiring surgery each year in the United States alone, societal costs are over a billion dollars annually (1). While repair with synthetic mesh products have become the surgical treatment of choice, these meshes require very little premarket testing because they are based on previously approved abdominal wall hernia products (510K devices). Thus, there is little scientific data on the efficacy of meshes for gynecological surgery. Moreover, with the recent FDA warning citing large numbers of unreported complications in patients, there is growing concern about the use of gynaecological mesh, especially for transvaginal placement (2). Thus, there is a need to examine the ex-vivo properties of these meshes and relate them to their in-vivo function and outcomes for gynecological applications.
Effect of ST2, a Fragment of ADAMTS13, on Cleavage of Von Willebrand Factor
Authors: Shao Jin-Yu , Ling Yingchen , Sadler J. Evan , Majerus Elaine M.
Published: July 2013

Von Willebrand Factor (VWF) is a multimeric plasma glycoprotein that mediates platelet adhesion and aggregation, a process critical for both hemostasis and thrombosis. Under normal conditions, VWF binds to platelets at sites of vascular injury or damage, leading to blood clot formation and wound healing. VWF contains four types of repeating domains in the following sequence: D1-D2-D’-D3-A1-A2-A3-D4-B1-B2-B3-C1-C2-CK (CK: cystine knot). It is synthesized and secreted into plasma by endothelial cells and megakaryocytes. Many newly-secreted VWF multimers are huge in size, thus they are termed ultra-large VWF (ULVWF). ULVWF is thrombogenic, so it is reduced to smaller VWF multimers by ADAMTS13, a metalloprotease that cleaves the Tyr1605-Met1606 bond in the A2 domain of VWF. Proper ULVWF cleavage and subsequent VWF cleavage result in appropriate size distribution of VWF in plasma, which is required for its hemostatic function. On the one hand, insufficient cleavage of ULVWF leads to thrombotic thrombocytopenic purpura (TTP), a disease characterized by microvascular thrombosis; on the other hand, excessive cleavage of VWF leads to Von Willebrand disease (VWD), a potentially-fatal bleeding disorder manifested by lack of large VWF multimers in plasma [1]. Therefore, understanding VWF cleavage by ADAMTS13 is crucial for understanding VWF function and its related diseases.
Temperature Field Reconstruction for the Application of Wireless Implantable Temperature Sensors in Cryosurgery
Authors: Thaokar Chandrajit , Rabin Yoed
Published: July 2013

This study is a part of an ongoing effort to develop means to improve monitoring and control of cryosurgery—the destruction of undesired biological tissues by freezing. Cryosurgery is being developed as a minimally invasive procedure since the mid 1980’s, following technological developments in medical imaging. Prostate cryosurgery was the first to become a routine minimally invasive cryosurgical procedure [1].
Creep Simulation of a Micro-CT Based Finite Element Model of Porcine Cancellous Bone
Authors: Ertas Ahmet H. , Sindelar Betty J. , Cotton John R.
Published: July 2013

Creep and fatigue behavior of cancellous bone are thought to be important in senile fractures [1, 2], bone remodeling [3], and implant subsidence [4]. Mechanical tests of cancellous bone samples have explored permanent deformation over time in both creep and fatigue loading. For example, Bowman, et al. [1] investigated creep behavior of bovine trabecular bone showing strong relationships between the applied stress and both time-to-failure and steady-state creep rate.
A Biphasic Model Illuminating Freezing-Induced Fluid-Matrix Interactions in a Tissue Equivalent
Authors: Wright Jamie , Han Bumsoo , Chuong Cheng-Jen
Published: July 2013

Cryopreservation of engineered tissue equivalents (TE) has achieved limited success. Successful preservation of a functional TE or tissue could provide prolonged transplantation time windows or off-the-shelf availability of engineered tissues. A quantitative understanding of the freezing-induced cell-fluid-matrix mechanical interaction is critical towards successful preservation of functional tissue. Using quantum dot-mediated cell image deformetry, Teo et al have experimentally mapped the instantaneous deformation of a TE during freezing process and showed its resulting volume change after thawing due to fluid loss [1]. To further our understanding of the freezing-induced fluid-matrix interaction, we have developed a biphasic model that simulates the transient of thermal load, its resulting TE elastic deformation, the corresponding pressure redistribution within, and the fluid movement in the TE.
Wall Shear Stress Measurements in an Arterial Flow Bioreactor
Authors: Voigt Elizabeth , Buchanan Cara , Schmieg Jaime , Rylander M. Nichole , Vlachos Pavlos
Published: July 2013

Physiological flow parameters such as pressure and stress inside the vascular system strongly influence the physiology and function of vascular endothelial cells [1]. Variations in the shear stress experienced by endothelial cells affect morphology, alignment with the flow, mechanical strength, rate of proliferation, and gene expression [2]. Although it is known that these factors are dependent on the hemodynamics of the flow, the relationship has not been accurately quantified. In vitro bioreactor flow loops have been developed to simulate vascular flow for tissue conditioning and measurement of the endothelial cell response to varying shear [3–5]; however, wall shear stresses (WSS) have been estimated from the bulk flow rate by assuming Poiseuille flow [2, 6]. Due to the pulsatility of the flow, biochemical interactions, and the typically short vessel length, this assumption is fundamentally incorrect; however, the level of inaccuracy has not been quantified.
Controlling Swimming Magnetotactic Bacteria Through Microfabrication Toward a Non-Destructive Biological Sensor
Authors: González Lina M. , Ruder Warren C. , Zenkov Eli , LeDuc Philip R. , Messner William C.
Published: July 2013

The development of non-destructive sensors is an important direction to pursue to advance approaches, which are less intrusive in their monitoring. One area where significant advances can be made in this field is through using biological inspiration. In this work, we demonstrate the ability of swimming magnetic bacteria, Magnetospirillum magneticum strain AMB-1, to respond to microfabricated magnetic field concentrators. These magnetic bacteria are envisioned as a potential non-destructive sensor approach for detecting defects in submerged metal structures such as ship hulls and bridges. To accomplish this, a pair of Helmholtz coils was built to magnetize microfabricated permalloy (NiFe) structures of different shapes that mimic defects in metals. The NiFe structures were fabricated through photolithography and depositing a thin film of NiFe on a master mold. The substrate was a thin piece of glass (<170μm) that permitted us to observe the interaction of the magnetic bacteria with the NiFe structures that were positioned at the center of the Helmholtz coils. The response of the bacteria around the structures was quantified through analyzing the images of the bacteria in terms of orientation. The bacteria change orientation as they approach the fabricated structures with concentrated fields due to their geometries. In addition, we used magnetic particles to examine the fields and estimated the local magnetic fields exerted on the particles through calculations involving the forces on the beads. We believe that this work is important in a variety of areas from bacterial mechanics to synthetic biology to aqueous non-destructive sensors.
Strain Distribution of Cytoskeletons in a Cell Embedded in Deformed Tissue
Authors: Wada Shigeo , Soga Masatsugu , Ujihara Yoshihiro , Nakamura Masanori , Koshiyama Kenichiro , Miyazaki Hiroshi
Published: July 2013

The responses of a tissue to an applied mechanical load are the results of overall responses of cells. Deformation of cells embedded in the tissue is immediately transmitted to internal cytoskeletons that interact extensively and intimately with cellular membranes. Cytoskeletons have been shown to dynamically respond to changes in external mechanical environments such as stretch, which results in various outcomes such as change in cell stiffness, alteration of cell adhesivity to substrates or generation of processes. Taking into account a fact that cytoskeletons are concerned deeply with such cellular remodeling, it is necessary to investigate cytoskeletal deformations when cells are subjected to deformation for gaining mechanical insight into the mechanism of cellular remodeling.