bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Cyclic Tensioning Duration on the Mechanical Property of a Stem Cell-Based Self-Assembled Tissue (scSAT) Derived From Synovium
Authors: Saito Kei , Ogawa Atsushi , Ando Wataru , Nakamura Norimasa , Fujie Hiromichi
Published: July 2013

Various fibrous tissues such as tendons and ligaments functionally adapt to dynamic and static loads. Although a variety of biomechanical studies have been performed so far to determine the mechanism of remodelling in fibrous tissues, it was difficult to obtain detailed information because of complicated constitution of the tissues. Meanwhile we have been developing a stem cell-based self-assembled tissue (scSAT) for tissue engineering, composed of synovial-derived mesenchymal stem cells (MSCs) and their native extracellular matrix. The scSAT used for cartilage repair is called tissue engineered construct (TEC) [1, 2]. Since the scSAT specimen is consisted of stem cells and their native extracellular matrix, it can be a good experimental model of fibrous tissues to determine the process of remodelling. Therefore, the effects of cyclic tensioning and its duration on the mechanical property of the scSAT specimen were investigated in the present study. It was also the purpose of the present study to determine the bio-synthesis condition adequate for improving the mechanical property of the scSAT specimen.
Role of Elastin Degradation in Identification of Vascular Strain Energy Functions
Authors: Rezakhaniha Rana , Fonck Edouard , Stergiopulos Nikos
Published: July 2013

The vessel wall exhibits relatively strong nonlinear properties and undergoes wide range of deformations. These characteristics make the identification of a strain energy function (SEF), the preferred method to describe the complex nonlinear elastic properties of the vascular tissue. None of the currently proposed structural models succeeded in describing accurately and simultaneously both the pressure-radius (Pro) and pressure-longitudinal force (P-Fz) curves. We hypothesized that the shortcomings of current models are partly due to unaccounted anisotropic properties of elastin.
Pre-Clinical Evaluation of Total Knee Designs for Normal Function
Authors: Walker Peter S. , Heller Yonah , Yildirim Gokce , Cleary David
Published: July 2013

Although Total Knee Replacement (TKR) is successful both in function and durability, there is evidence that the kinematics are abnormal, suggesting that function can be further improved, especially in patients with the capability of returning to an active lifestyle. The goal of this study was to formulate a testing method which would predict the performance of a TKR by using the mechanical characteristics of the anatomic knee as a benchmark. It is proposed that a ‘holistic testing method’ should consist of a determination of the neutral path of motion during a full flexion range, together with the AP and rotational laxity about the neutral path. This test regimen would represent the forces and torques experienced in a range of everyday activities. The proposed testing method is evaluated using a special test rig to compare the kinematics of different TKR designs, with anatomic knee specimens.
Mechanistic Determination of In Situ Toughness of Bone Using a Nanoscratch Methodology
Authors: Wang Xiaodu
Published: July 2013

Hierarchical structures at multiple length scales are characteristic in a class of natural (e.g., bone) and synthetic (e.g., nano-composites) materials that are quasi-brittle in nature but allow for appreciable plastic deformation (1, 2). Since the bulk mechanical properties of the materials are heavily dependent on their nano/microscopic structures, micro/nano mechanics approaches are often required to study their behaviors. However, lack of an effective means to exemplify the post-yield and failure behavior directly at micro/nanometer scales has significantly precluded understanding the constitutive relationship of these materials. A compelling example is that such paucity has significantly hindered establishment of physically sound constitutive relationships for bone tissues. Recent progresses in nanotechnology have allowed for estimation of the stiffness and hardness of bone tissues at submicron and nano length scales (3–5). However, no methods are currently available to assess the post-yield and failure behavior of bone tissues at nano/microscopic levels. Our pilot study (6) has shown that nanoscratch tests could be used in assessing the in situ energy dissipation during the post-yield deformation of bone tissues. To this end, the objective of the present study is to establish a mechanistic model for the nanoscratch methodology based on a assumption that the in situ toughness of bone tissues or the capacity to dissipate energy until failure can be estimated based on the removal energy of the tissue consumed during a nanoscratch test.
Computational Analysis of a Wearable Artificial Pump Lung Device in Terms of Rotor/Stator Interactions
Authors: Taskin M. Ertan , Zhang Tao , Griffith Bartley P. , Wu Zhongjun J.
Published: July 2013

Lung disease is America’s third largest killer, and responsible for one in seven deaths [1]. Most lung disease is chronic, and respiratory support is essential. Current therapies for the respiratory failure include mechanical ventilation and bed-side extracorporeal membrane oxygenation (ECMO) devices which closely simulate the physiological gas exchange of the natural lung.
An Optimized Semi-Shotgun Method to Analyze the Secretome of Breast Cancer Cell Line
Authors: Tang Xiaorong , Yao Ling , Chen Keying , Hu Xiaofang , Xu Lisa X.
Published: July 2013

The secretome of cancer cell lines provides promising pool for the identification of candidates for cancer biomarkers. Simple and effective proteomics method to identify secreted proteins is highly desired [1, 2].
Patient-Specific Finite Element Analysis of Femoral Giant Cell Tumor Reconstructed Using Locking Plate System
Authors: Li Jihui , Wodajo Felasfa
Published: July 2013

Giant cell tumor (GCT) is a benign bone tumor that usually involves the end of long bone in young adults. GCT is locally aggressive, weakens the bone and can lead to pathologic fracture [1, 2]. Clinically, GCT is removed and the defect is reconstructed with bone cement, sometimes enhanced with intramedullary pins. However, there was no significant biomechanical advantage to using a cement plus pin construct over cement alone; clinical outcomes of both reconstruction methods were controversial [3–5]. While locking plates were recently adopted for GCT reconstruction, no biomechanics analysis has been performed to indicate its advantage over the cement alone or cement plus pin reconstruction. In this study we developed patient specific finite element (FE) models to compare the mechanical strengths of GCT reconstructed using cement alone and cement plus locking plate.
Effect of Flow Pulsatility on 2nd Stage Fontan Hemodynamics: An In Vitro Investigation
Authors: Haggerty Christopher M. , Dasi Lakshmi P. , Kanter Jessica , Yoganathan Ajit P.
Published: July 2013

The Fontan procedure [1] is the staged, palliative surgical approach used to treat patients suffering from single ventricle congenital heart defects. The second stage of this procedure involves the connection of the superior vena cava (SVC) to the pulmonary arteries (PAs) in either an end-to-side (known as the Bi-Directional Glenn (BDG)) or side-to-side (or Hemi-Fontan (HF)) fashion. Because of obvious disparities at the connection site, there are understandable differences in the fluid dynamics between the two geometries.
Protein State Affects Wear of UHMWPE
Authors: Dwivedi Yasha , Laurent Michel P. , Schmid Tom , Wimmer Markus A.
Published: July 2013

It is well established that the lubricant properties play a key role in the wear of UHMWPE in prosthetic knees [1] and hips [2, 3]. The total protein concentration, the albumin – globulin ratio, the lubricant volume turnover rate, and the protein precipitation rate, all have ben found to affect the polyethylene wear rate [3]. A factor that has not yet been studied, but may be of clinical relevance, is the effect of the state of protein on the wear and friction of prosthetic joints. Protein cleavage is expected in the presence of an inflammatory response [4] and through wear processes at the articular interface. Such cleavage may have a significant effect on the lubrication regime and the wear mechanism of the prosthetic joint. An understanding of this effect is therefore required to further elucidate UHMWPE wear mechanisms, to increase the reliability and validity of wear tests for the preclinical evaluation of prosthetic joints, and to clinically assess patient effects.
Model Complexity and Prestressing in Abdominal Aortic Aneurysm Simulation
Authors: Gee Michael W. , Wall Wolfgang A.
Published: July 2013

Rupture of abdominal aortic aneurysm (AAA) is the 13th leading cause of death in western society and is fatal in 70–90%. In consequence, precise prediction of AAA rupture risk is essential. With the current, well established CT-morphological parameters such as maximum aortic diameter, aneurysm shape and AAA expansion, only at best the relative, but not the individual rupture risk can be determined. Hence, AAA rupture may occur unexpectedly in small aneurysms below the critical diameter limits whereas many large aneurysms may remain stable throughout patient’s lifetime, without prophylactic surgery.
A Laparoscopic Camera-Enabled Cannula Port
Authors: Rentschler Mark E. , Terry Ben S. , Ruppert Austin D.
Published: July 2013

This project is exploring a potential new approach in providing visual feedback during minimally invasive surgery (MIS) that involves integrating a CMOS camera imager and lens into a traditional cannula entry port. Initial research has focused on developing this device for abdominal surgery (laparoscopy). Such a device can provide vision assistance without positioning and orientation constraints associated with current laparoscopes. Patients who undergo laparoscopic surgery experience less pain, shorter hospital stays, and a more rapid return to normal activities compared to patients who undergo conventional surgery. The benefits of laparoscopic surgery, however, are generally restricted to patients undergoing less complex procedures. The primary reason for limited application of laparoscopy to more complex procedures is two-fold. The first drawback is the limitation of the laparoscope to view all aspects of the abdominal cavity including looking back towards the entry site. Secondly, to view the video image from the scope the surgeon must turn focus away from the patient and towards a recorded video image on a monitor placed away from the patient. These constraints impose severe perception and orientation limitations that degrade surgical task performance. The long-term goal of this project is to develop a camera and sensor module that can be placed within traditional trocar ports for insertion, and that deploy outward from the cannula port after insertion. This approach will allow these ports to still be utilized by all traditional laparoscopic surgical tools, while potentially removing the need for the laparoscope. In addition, a small LCD display is placed at the port’s proximal end restore natural perception and orientation for the surgical team.
Evaluation of Effectiveness of Er,Cr:YSGG Laser for Root Canal Disinfection: Theoretical Simulation of Temperature Elevations in Root Dentin
Authors: Zhu Liang , Tolba Mostafa , Arola Dwayne , Salloum Maher , Meza Fernando
Published: July 2013

Lasers have been used in dentistry for removing hard tooth tissue for more than twenty years. Erbium, chromium: yttrium, scandium, gallium, garnet (Er, Cr: YSGG) lasers are currently being investigated for disinfecting the root canal system, since bacteria can spread from the root canal surface to the deep dentin via the dentin tubules [1]. It is expected that temperature elevation in the deep dentin is sufficient to eradicate bacteria there. Prior to using laser therapy, it is important to understand the temperature distribution and to assess thermal damage to the surrounding tissue. In this study, we develop a heat transfer model to estimate the temperature elevations in both the tooth root and surrounding tissue during Er,Cr:YSGG laser disinfection of the root canal surface. The laser power level, pulse setting, as well as laser duration are incorporated into the Pennes bioheat equation for the theoretical study. We propose a treatment protocol that achieves better heat penetration with shorter treatment time than the existing protocols used in dentistry [2].
A Translating Stage System for Micro-PIV Measurements Surrounding a Migrating Semi-Infinite Bubble
Authors: Smith Bradford J. , Yamaguchi Eiichiro , Gaver Donald P.
Published: July 2013

We have designed, created, and evaluated a translating stage system (TSS) used for Micro Particle Image Velocimetry (μ-PIV) measurements surrounding the tip of a migrating semi-infinite bubble in a glass capillary tube. This study is relevant to acute respiratory distress syndrome (ARDS), which is characterized by pulmonary airway collapse and fluid occlusion. Subsequent airway reopening, driven by mechanical ventilation, may generate damaging mechanical stresses on the airway walls that can result in ventilator-induced lung injury (VILI). Our goal in this study is to characterize and demonstrate a system for mechanically canceling the mean forward velocity of a migrating bubble, allowing continuous measurement near the tip region of interest. This system will be used to validate our previous boundary element computations in a surfactant-free system [1] and further explore airway reopening phenomenon related to surfactant physiochemical interaction.
Double-Modular Hip Device Design Susceptible to Stress Corrosion Failure
Authors: Atwood Sara A. , Patten Eli W. , Bozic Kevin J. , Pruitt Lisa A. , Ries Michael D.
Published: July 2013

Total hip replacements restore pain-free mobility to approximately 200,000 patients in the U.S. each year [1]. A typical hip system comprises a metal alloy stem, a femoral head (ceramic or metal alloy), and a polyethylene acetabular cup fit into a metal alloy backing. A modular press-fit Morse taper is commonly used to attach the femoral head to the stem. There are also more recent designs that incorporate a second interface at the neck-stem junction (Figure 1). Increased modularity in total hip replacement design allows the surgeon to intraoperatively preserve patient anatomy such as leg length and femoral anteversion and better balance the surrounding soft tissue for optimal biomechanics. However, modularity also increases the number of mechanical junctions and interfaces in the device which may lead to complications such as corrosion, wear, and fracture.
Effect of Geometric and Dynamic Parameters on Fluid Flow and Particle Dispersion in Human Lung Acini
Authors: Chhabra Sudhaker , Prasad Ajay K.
Published: July 2013

Breathing, defined as the exchange of gases between the respiratory system and the environment, is an essential process for life. The human respiratory system can be divided into three parts: (i) nose, mouth, and nasopharynx, (ii) trachea, and (iii) lungs. The human lung can be further subdivided into conducting airways which are non-alveolated and comprise the upper part of lung, and the acini which consist of flexible, alveolated airways and are responsible for gas exchange [1]. The alveoli collectively provide a large surface area (∼70 m2) for efficient gas exchange [1]; oxygen diffuses into the blood through the alveolar epithelium, whereas carbon dioxide diffuses in the opposite direction from the blood to the lung.
The Onset of Structural Yield During Tensile Loading Increases With Age in the Pediatric PMHS Cervical Spine
Authors: Quinn Kyle P. , Luck Jason F. , Nightingale Roger W. , Winkelstein Beth A.
Published: July 2013

Motor vehicle crashes are the leading cause of injury to the pediatric spine, and the mortality rate of pediatric spinal trauma victims has been approximated at 25–32% [1]. In addition, non-fatal painful traumatic injuries resulting from motor vehicle crashes or sports-related activities contribute to an estimated prevalence of neck pain of 21–41% in children and adolescents [2]. It has been hypothesized that the anatomy of the pediatric neck, combined with a relatively large head mass, presents an increased risk for traumatic inertial loading in that population, particularly during early development. However, the relationship between mechanical metrics related to pain and age remains undefined, limiting the development of meaningful estimates of tolerance to painful injury in this population.
Prediction of Disturbed Flow by Factor Analysis of Carotid Bifurcation Geometry
Authors: Zhang Qi , Steinman David A. , Friedman Morton H.
Published: July 2013

Hemodynamics plays an important role in the development and progression of carotid artery atherosclerotic lesions. Certain aspects of vascular geometry, which mediates local hemodynamics, might be risk factors that increase a vessel’s atherosusceptibility [1]. To further evaluate this “geometric risk factor” hypothesis, the relationship between geometric features and hemodynamic quantities thought to typify “disturbed flow” was recently investigated [2]. Fourteen intercorrelated geometric features were initially extracted from MR images of 50 carotid bifurcations, and multivariate regression based on an a priori selection of a subset of four of these geometric features was used to identify two that were predictors of disturbed hemodynamics. Here, this work is extended to simultaneously analyze the combined role of all geometric variables using factor analysis.
Quantitative Modeling of Vacuum-Enhanced Human Heat Transfer
Authors: Hensley Daniel W. , Diller Kenneth R.
Published: July 2013

The ability to easily manipulate body temperature would impact a number of fields. While perfusion with externally cooled or warmed blood is effective due to the thermoregulatory power of the circulatory system and its diffuse microcirculation, this process is particularly invasive. Noninvasive techniques to date mostly utilize body surface applications that rely on relatively inferior conduction heat transfer.
Can a Polycarbonate-Urethane Meniscal Implant Protect Articular Cartilage? Histopathological Results in a Sheep Model
Authors: Linder-Ganz Eran , Zur Gal , Shani Jonathan , Elsner Jonathan J. , Brenner Ori , Arnoczky Steven P. , Agar Gabriel , Hershman Elliott B. , Shterling Avi
Published: July 2013

The menisci play an important role in the knee joint biomechanics [1]. Clinical studies have shown that the loss of the meniscus leads to degenerative arthritis attributed to the changes in load distribution and the loss of proprioception [2]. Clearly, there is a substantial need to protect the articular cartilage by either repairing or replacing the menisci. There are many difficulties dealing with both fresh frozen or cryopreserved allograft menisci, and the complexities of meniscal repairs may contribute to uneven distribution of load, instability and recurrence of degenerative damage. Hence there is a need for the development of an artificial meniscus that is available at the time of surgery in several sizes that can accommodate most patients.
Meniscal Implant Biomechanical Performance: A Novel Quantitative Approach
Authors: Elsner Jonathan J. , Linder-Ganz Eran , Danino Amir , Guilak Farshid , Shterling Avi
Published: July 2013

One of the functions of the meniscus is to distribute contact forces over the articular surfaces by increasing joint contact areas [1]. It is widely accepted that total/partial loss of the meniscus increases the risk of joint degeneration. A short-term method for evaluating whether degenerative arthritis can be prevented would be to determine if peak pressure and contact area coverage of the tibialis plateau (TP) articular surface in the knee are restored at the time of implantation. Although several published studies already utilized TP contact pressure measurements as an indicator for biomechanical performance of allograft menisci [2,3], there is a paucity of a quantitative method for evaluation of these parameters in situ with a single effective parameter. In the present study, we developed such a method and employed it on sheep and human cadaveric knees.
Circumferential Cyclic Strain in Patients With Descending Thoracic Aortic Aneurysms: Implications for Endovascular Device Design
Authors: Morrison Tina M. , Taylor Charles A.
Published: July 2013

Endovascular graft (EVG) therapy has emerged as a promising alternative to open surgical repair of thoracic aortic aneurysms. However, the long-term durability of thoracic endovascular repair (TEVAR) remains uncertain due to complications such as incomplete aneurysm exclusion (endoleaks), migration, and stent fracture and collapse. These complications could likely be reduced if the biomechanical environment of the thoracic aorta was better understood. Currently, there are three FDA approved EVGs for treatment of descending thoracic aortic aneurysms (DTAA), but the range of bench-top testing mechanisms for these devices are limited.
A Computational Technique for Uncertainty Quantification and Robust Design in Cardiovascular Systems
Authors: Sankaran Sethuraman , Feinstein Jeffrey A. , Marsden Alison L.
Published: July 2013

Numerical simulations of blood flow in the human cardiovascular system are usually performed using custom Finite element methods and specialized boundary conditions. These simulations are performed to (a) understand the physics of blood flow in the human cardiovascular system and (b) a priori testing of proposed treatments/interventions whether surgical or endovascular. To perform these simulations, we require prior knowledge of parameters such as cardiovascular geometry, boundary conditions (inflow/outflow/pressure), etc. In the past, researchers have assumed exact values for these parameters. However, in reality, each of these parameters is uncertain. For example, inflow conditions into the model are dictated by the heart rate and cardiac output of the patient. Even during rest, there are variations in cardiac output and hence the corresponding blood inflow velocities need to be modeled as a random variable. Additionally, the cardiovascular geometry is built based on MRI-images. These are subject to uncertainties due to noise in the data and variability between users during model construction. We develop a computational toolbox that can account for uncertainties in such parameters in hemodynamic simulations. The uncertainties examined in this work include i) variation and accuracy of image-based model geometry ii) variability in inflow condition of the patient and iii) variability in the implementation of the final surgical design. The last source of uncertainty stems from the fact that optimally designed surgical parameters may not be exactly implemented in the operating room. We show numerical examples of (a) blood flow in stenotic vessels (b) effect of uncertainty in carotid sinus size on blood flow and (iii) develop a stochastic optimization technique to compute optimal parameters of an idealized Y-graft model for the Fontan surgery accounting for sources of uncertainties listed above.
Validation of Santos Biomechanics
Authors: Rahmatalla Salam , Xiang Yujiang , Smith Rosalind , Meusch John , Li Jinzheng , Bhatt Rajankumar , Abdel-Malek Karim
Published: July 2013

A validation methodology for an optimization-based predictive dynamics framework for digital human motion simulation is presented in this work. The proposed validation methodology has been implemented in time and frequency domains on a predicted walking task. The methodology uses selected critical key frames in the comparison process in the time domain, as against the full profile of all joint angles. In the frequency domain, the methodology considers using fast Fourier transform and power spectrum density. In addition to human kinematics, the methodology compares inertia and ground reaction forces, a key kinetic parameter for motion validation. The results have shown considerable correlation and insight information between the predicted and the measured data.
Constrained Mixture Models of Arterial Homeostasis and Adaptation
Authors: Humphrey J. D.
Published: July 2013

Phenomenological models of the mechanical behavior of the arterial wall continue to play important roles in vascular mechanics. Indeed, such models revealed the importance of residual stresses in homogenizing the transmural distribution of stress in normalcy [1], which in turn led to one of the most important hypotheses in vascular mechanobiology — the existence of a mechanical homeostasis [2]. Nevertheless, classical models are not able to exploit the growing information on the different mechanical properties and rates and extents of turnover of different structurally significant constituents within the arterial wall. To address this need, we have proposed a structurally-motivated, materially nonuniform model of the arterial wall based on a theory of constrained mixtures [cf. 3]. Key features of this model include the ability to prescribe individual stored energy functions for different structurally significant constituents that are constrained to move together within the overall wall while being allowed to possess individual evolving natural (stress-free) configurations, and the ability to prescribe separate stress-mediated constitutive relations for constituent production and removal.

We have shown that this constrained mixture approach can capture many salient features of arterial adaptations (e.g., evolving changes in geometry, overall material behavior, and collagen to elastin ratios) to both altered mechanical loading (e.g., altered blood flow and pressure as well as axial stretch) and disease progression (e.g., enlargement of intracranial aneurysms and the development and resolution of cerebral vasospasm). We submit that, in contrast to models built on the assumption of kinematic growth, this constrained mixture approach can incorporate increasingly detailed biological information on cell and matrix turnover and can thereby begin to generate and test novel hypotheses on mechanisms of arterial homeostasis and adaptation. We will show, for example, that the constrained mixture model suggests a possible mechanism for the origin of residual stresses and axial prestretches, the importance of cellular deposition of new extracellular matrix proteins within stressed states, the complementary roles of vasoactivity and matrix remodeling, and stress mediation of matrix turnover [4,5]. We note, in particular, the importance of residual stress and axial prestress in establishing arterial homeostasis and thus targets for subsequent adaptations [5,6].
Nonlinear Constituent Based Viscoelastic Modeling of GAG Depletion Experiments Suggests Strong GAG-Collagen Interactions in Immature Articular Cartilage Tissue
Authors: Klisch Stephen M. , Thomas Gregory C. , Asanbaeva Anna , Vena Pasquale , Sah Robert L.
Published: July 2013

The porous solid matrix (SM) of articular cartilage (AC) contains glycosaminoglycans (GAGs) and collagens (COLs). GAGs provide a fixed negative charge that produces swelling and compressive resistance and the COL network produces tensile and shear resistance. The long-term goal of this study is to improve structure-function relations for characterizing AC growth and remodeling. A recent study using GAG depletion experiments suggested that GAG-COL interactions regulate tissue mechanical properties in a manner dependent on maturational stage [1]. The objective of this study was to characterize GAG-COL interactions on viscoelastic (VE) properties for immature AC tissue. The first aim was to modify a constituent based nonlinear VE model [2] to study AC tissue biomechanics. The second aim was to quantify the VE response for control and GAG depleted immature AC tested in uniaxial tension (UT).
A Novel Multilayered Annular Model to Predict Delamination in a Lumbar Intervertebral Disc
Authors: Natarajan Raghu N. , Lundberg Hannah J. , Oegema Ted , Andersson Gunnar B.
Published: July 2013

Disc degeneration normally is accompanied by structural changes in the intervertebral discs and the end plates. Reduced level of water in the disc, osteophytes formation and geometrical changes in the end plates also accompany the disc degeneration process. Structural changes in the disc due to degeneration can be classified into radial, peripheral and circumferential tears. Radial tears normally extend from inner annulus region to the outer annulus in the radial direction. These may be due to the failure of annular fibers. Peripheral tears in the annulus normally occur near the junction between the annulus and end plates. These may be due to shear loads at the end plate-annulus junction. Circumferential tears can be observed in both anterior and posterior annulus. These circumferential tears may be due to separation of annular layers due to excess shear between layers and/or due to tensile strain between layers. Although the intrinsic mechanical behavior of the annulus fibrosus as a single layer has been studied, the response of the annulus in vivo does depend on its composite multilayer structure. Biomechanical analysis of the multilayered annulus will help to understand the initiation of delamination failure in the annulus. A finite element model of a lumbar disc with annulus consisting of several layers distributed along the radial direction of the disc with interface was developed to understand the delamination process of the disc under physiological loading modes. It is hypothesized that delamination starts at the inner annular layers near the end plates.
Regional Variations in Cartilage Mechanics and Composition Suggest a Sensitivity to Changes in Chronic Joint Loading Patterns
Authors: Bevill Scott L. , Andriacchi Thomas P.
Published: July 2013

It has been suggested that variations in cartilage mechanical properties and biochemistry within a joint may be critical in understanding the implications of altered joint kinematics as a pathway to the initiation of knee osteoarthritis (OA) [1]. For example, the kinematic changes resulting from anterior cruciate ligament (ACL) injury have been suggested as a mechanism for the initiation of OA by altering chronic joint loading patterns in a tissue with low adaptation potential [1]. This mechanism would suggest that regions of cartilage subjected to different habitual post-natal mechanical loading might exhibit, among other things, differences in biochemical content and mechanical properties. The tibial plateau offers a good test bed to evaluate this mechanism since peripheral region articular cartilage (covered by the menisci) appears to experience lower contact pressures in vivo during weight-bearing activity than regions of cartilage exposed to cartilage-cartilage contact [2, 3]. Thus, the purpose of this study was to test the hypothesis that there are significant regional differences in cartilage mechanical properties (including dynamic shear modulus, phase shift angle, and equilibrium Young’s Modulus) and biochemistry (including collagen content, sulfated glycosaminoglycan (s-GAG) content, and water content) between the central and peripheral regions of the porcine tibial plateau.
Weight-Bearing MRI: Comparison of Knee Angle Set-Up Methods and the Effect of Real-Time Visual Feedback
Authors: Dubowsky Sarah R. , Allen Jerome , Gade Venkata , Barrance Peter J.
Published: July 2013

Osteoarthritis (OA) is the most common form of arthritis worldwide, and is reported to be the leading cause of disability in the United States [1, 2]. With the invention of an upright MRI (Fonar Corp., Melville, NY), it is now possible to image the knee of an upright, weight-bearing patient in truly functional positions to provide improved techniques for early evaluation of knee OA. However, scan set-up in a weight-bearing MRI is challenging because of limited space. To get a subject to a targeted knee flexion angle (KFA) and to have them maintain this angle for the duration of a scan is difficult.
Finite Element Analysis of the Anatomy of Acupuncture Points
Authors: Shreiber David I. , Singanamalli Asha , Julias Margaret , Buettner Helen M.
Published: July 2013

Acupuncture is a centuries-old traditional therapy that is used to treat a litany of diseases and conditions. Acupuncture is performed by inserting fine needles into specific locations defined in ancient times — acupressure is similarly applied at these points by tissue palpation without needle insertion. Manipulating these acupuncture points is believed to regulate the flow of energy or ‘qi’ through acupuncture meridians to produce specific, far-reaching results. Though no scientific correlate to ‘qi’ has been identified, acupuncture has indeed been demonstrated to be clinically effective for nausea [1] and osteoarthritic pain [2], and suggested for addiction, stroke rehabilitation, headache, menstrual cramps, tennis elbow, fibromyalgia, myofascial pain, low back pain, carpal tunnel syndrome, and asthma [1]. Despite this evidence, no scientific basis for the location of acupuncture points has been found.
Near-Infrared Imaging Reveals Site- and Age-Specific Localization of Bisphosphonate Delivery and Retention in Model of Osteogenesis Imperfecta
Authors: Kozloff Kenneth M. , Volakis Leo I. , Marini Joan C. , Caird Michelle S.
Published: July 2013

Bisphosphonate use has expanded beyond traditional applications, such as the prevention of osteoporosis, into non-traditional pediatric low bone mass diseases including osteogenesis imperfecta (OI) [1]. Despite enthusiasm, some questions remain on the overall effectiveness and implications of long-term treatment. In the Brtl/+ mouse model for OI, bisphosphonate treatment improves bone size, but bending strength fails to increase to proportionate levels and bones remain brittle [2]. Complications associated with long-term bisphosphonate treatment have been noted in other systems [3,4] leading to a need for critical information describing local drug-cell interactions responsible for these observations. The purpose of this study was to validate a fluorescent bisphosphonate analog, far-red fluorescent pamidronate (FRFP) [5] as a biomarker of bisphosphonate deposition and retention in vivo to monitor local drug concentration in a site-specific manner.
Estrogen Depletion Increases Osteocyte Canalicular Diameter in Cortical and Cancellous Bone of the Rat Proximal Tibia
Authors: Ciani Cesare , Ramirez Marin Paula A. , Doty Stephen B. , Fritton Susannah P.
Published: July 2013

Estrogen depletion has been shown to cause bone loss in the proximal metaphysis of the rat tibia [1,2]. A decrease in bone volume fraction is frequently reported, yet there is little analysis in the literature related to changes in microporosities during osteoporosis. Our recent work quantifying microporosity changes due to estrogen depletion has shown an increase in the lacunar-canalicular porosity surrounding osteocytes in the proximal metaphysis of the rat tibia [3].
Why Are Rates of Restenosis Higher in Peripheral Arteries Than Coronary Arteries? A Computational Study
Authors: Early Michael , Kelly Daniel J.
Published: July 2013

The deployment of stents in some arteries outside the heart has long been recognized as problematic. The use of more flexible shape memory alloy (SMA) stents has improved success rates, making stenting a more successful option than balloon angioplasty alone in peripheral arteries. However, restenosis rates are still considerably higher in peripheral arteries, such as the, femoral and popliteal, than in coronary arteries. As well as differences in dimensions, composition and material properties, peripheral arteries can be subjected to adverse mechanical environments. In addition to the pulsatile environment experienced by all arteries, some peripheral arteries experience combinations of compression, twisting and bending [1, 2]. The objective of this study is to investigate the differences between stenting in coronary and peripheral arteries with a view to determining which factors could be responsible for elevating restenosis rates. Specifically, it will be determined which, if any, of differences in (i) geometry and material properties of the arteries, (ii) the type of stent used, and (iii) the pulsatile and flexion driven mechanical environments could be responsible for either fracture of stents or higher arterial stress levels which could explain the higher rates of restenosis seen in peripheral arteries.
A Composite Microsphere/Nanofiber Controlled Release System for Fibrous Tissue Engineering
Authors: Ionescu Lara C. , Baker Brendon M. , Burdick Jason A. , Mauck Robert L.
Published: July 2013

Fibrous tissues are characterized by a dense, ordered collagenous structure that defines their unique and anisotropic mechanical properties. These properties are critical for tissue function, and are compromised in instances of injury and tissue degeneration. To improve repair, engineering methods based on electrospinning have produced aligned and anisotropic scaffolds composed of biodegradable nanofibers that can serve as templates for new tissue formation [1]. For example, the slow degrading polyester, poly(ε-caprolactone) (PCL) can be formed into aligned arrays that direct cell alignment and ordered ECM deposition, with construct mechanical properties that increase with time [2]. We have further modified these structural templates via the fabrication of multi-polymer composites, with different mechanical properties and degradation profiles provided by different component materials [3]. For example, inclusion of a sacrificial poly-ethylene oxide (PEO) fiber element, followed by its removal (via hydration) increases the porosity of the remaining PCL network and expedites cell infiltration [4].
Deformation and Failure of Collagenous Tissues: A Multi-Scale Study
Authors: Buehler Markus J. , Uzel Sebastien
Published: July 2013

Fibrous proteins constitute critical building blocks of life, forming biological materials such as hair, bone, skin, spider silk or cells, which play an important role in providing key mechanical functions in biological systems. However, the fundamental atomistic and molecular deformation and fracture mechanisms of biological protein materials remain largely unknown, partly due to a lack of understanding of how individual protein building blocks respond to mechanical load.
Towards Patient-Specific Modeling of an Enlarging Abdominal Aortic Aneurysm
Authors: Zeinali-Davarani S. , Sheidaei A. , Baek S.
Published: July 2013

There has been a clear need for better understanding of the progression of abdominal aortic aneurysm (AAA) and obtaining reliable prediction of the AAA rupture. Finite element analysis (FEA) using non-axisymmetric models of AAAs provides better estimation of stress distribution in the aneurysmal wall with complex shapes [1]. However, FEA alone does not provide a mathematical description for the evolution of an AAA through growth and remodeling (G&R). A computational framework for modeling stress-mediated growth and structural remodeling of the arterial wall under physiological and pathological conditions has been suggested using a constrained mixture assumption [2]. Stress-mediated enlargement of intracranial aneurysms has been investigated using idealized axisymmetric geometries [3,4]. The kinetics of stress-mediated turnover of collagen fiber families and degradation of elastin were found to have particular importance in the G&R of aneurysmal wall.
Robustness-Strength Performance of Hierarchical Alpha-Helical Protein Filaments
Authors: Buehler Markus J. , Qin Zhao , Cranford Steven , Ackbarow Theodor
Published: July 2013

The origin of how naturally occurring biological protein materials (e.g. cellular protein filaments, spider silk, bone, tendon, skin) are capable of unifying disparate mechanical properties such as strength (ability to sustain large stresses without fracture) and robustness (ability to undergo deformation without fracture, despite the presence of defects, equivalent to toughness) is of significant interest (Figure 1). However, the molecular basis of these properties remains largely unknown [1–3].
Continuum Modeling of Biological Tissue Growth by Cell Division
Authors: Ateshian Gerard A. , Costa Kevin D. , Azeloglu Evren U. , Morrison Barclay , Hung Clark T.
Published: July 2013

A framework is formulated for continuum modeling of biological tissue growth that explicitly addresses cell division, using a homogenized representation of cells and the extracellular matrix (ECM). The essential elements of this model rely on the description of the cell as containing a solution of water and osmolytes, and having osmotically inactive solid constituents that may be generically described as a porous solid matrix. The division of a cell into two nearly identical daughter cells normally starts with the duplication of cell contents during the synthesis phase, followed by cell division during the mitosis phase. Thus, ultimately, cell division is equivalent to doubling of the cell solid matrix and osmolyte content, and a resulting increase in water uptake via osmotic effects. In a homogenized representation of the tissue, the geometry of individual cells is not modeled explicitly, but their solid matrix and intracellular osmolyte content can be suitably incorporated into the analysis of the tissue response, thereby accounting for their osmotic effects. Thus, cell division can be described by the growth of these cell constituents, including the accumulation of osmotically active content, and the resultant uptake of water.
Tissue-Light Interaction During Monitoring of Thermal Lesion Using Quantum Dot Mediated Fluorescence Thermometry
Authors: Hanson Willard , Abdollahzadeh Najma , Liu Yaling , Han Bumsoo
Published: July 2013

As cancer diagnostics advance, tumors are increasingly detected at very early stages so that the tumors can be destroyed in situ by localized heating. This can be achieved minimally invasively or completely non-invasively using various energy sources including laser, RF wave, microwave and ultrasound. Despite many advantages of these thermal therapies, the major huddle to the widespread dissemination of thermal therapy is the lack of a reliable intraoperative monitoring technique of the thermal lesion. Currently available monitoring techniques cannot provide reliable real-time information of thermal lesion due to their limited accuracy or accessibility.
The Effect of Composition and Inter- and Intrafibrillar Interactions on the Structure of Collagen IV Networks in the Computer-Simulated Glomerular Basement Membrane
Authors: Swickrath Michael J. , Dorfman Kevin , Segal Yoav , Barocas Victor H.
Published: July 2013

The glomerular basement membrane of the kidney, responsible for performing ultrafiltration blood plasma, is largely comprised of type-IV collagen and laminin. Type-IV collagen self-assembles into a heterotrimer composed of three distinct domains (fig. 1A): (1) the globular non-collagenous NCl domain of ∼10 nm in diameter, (2) the non-collagenous 7S domain ∼30 nm in length and ∼3nm in diameter, and (3) the collagenous triple helix of ∼370 nm in length and ∼3 nm in diameter composed of a repeating Gly-X-Y subunit [1]. The heterotrimers associate with remarkable specificity from six genetically distinct α-chains, α1(IV) to α6(IV) forming α1α1α2, α3α4α5, and α5α5α6 heterotrimers [2]. In the healthy glomerulus, α1α1α2 ([α1]2α2) is the predominate collagen while significant α3α4α5 is present; α5α5α6 exists only in negligible quantities [2].
Computational Fluid Dynamics-Based Estimation of Blood Flow Rate in Doppler Analysis: In Vivo Validation by Means of Phase Contrast Magnetic Resonance Imaging
Authors: Ponzini Raffaele , Vergara Christian , Rizzo Giovanna , Veneziani Alessandro , Redaelli Alberto , Vanzulli Angelo , Parodi Oberdan
Published: July 2013

In this work we carry out an in vivo validation of a method for estimating blood flow rate from the peak velocity, as it is usually done in single-wire Doppler catheter measurements. This method, originally proposed in [1] stems from the application of numerical analysis of the blood flow with Computational Fluid Dynamics (CFD) techniques. It proposes a new formula linking the maximum velocity and the flow rate, which, however, has the same practical cost of classical approaches based on a priori assumptions on the velocity profile. After the first clinical observations indicating the improved accuracy in flow rate estimates introduced by the new method discussed in [2, 3], in this paper we present an ad hoc in vivo validation, as firstly suggested in [4], still confirming the reliability of the new approach.
Simultaneous Prediction of Muscle and Contact Forces in the Knee During Gait
Authors: Fregly Benjamin J. , Lin Yi-Chung , Walter Jonathan P. , Fernandez Justin W. , Banks Scott A. , Pandy Marcus G.
Published: July 2013

Walking is important for human health, and independent ambulation predicts quality of life [1]. The study and treatment of neurological and joint disorders that inhibit walking would be more effective if muscle and joint forces could be determined reliably for individual patients. Knowledge of muscle forces is needed to characterize muscle coordination, which is a factor in neurological disorders such as cerebral palsy and stroke, while knowledge of joint contact forces is needed to characterize articular loading, which is a factor in bone and joint disorders such as osteoporosis and osteoarthritis. Reliable determination of these internal forces for individual patients would facilitate the design of customized surgical and rehabilitation treatments that maximize functional outcome.
MRI Analysis of Anteroposterior Stability in the Normal Human Knee
Authors: Arno Sally , Forman Rachel , Glassner Philip , Regatte Ravinder , Walker Peter S.
Published: July 2013

During activities the knee experiences compressive forces caused by the weight of the body and muscle forces. However, there is also an anterior shear force pushing the femur forwards on the tibia. It is likely to be important to the feeling of stability that the shear force is resisted so as to limit the anterior femoral displacement. The dished bearing surface of the medial tibial compartment in combination with the medial meniscus may well perform this function. In contrast, the lateral tibial surface is convex in the sagittal plane and the meniscus is too mobile to offer any anteroposterior (AP) restraint. Therefore, we hypothesize that if an anterior or posterior force is applied to the femur relative to the tibia, AP stability is provided by the medial side, while the lateral side allows for femoral rollback to facilitate a high range of flexion. At any flexion angle, rotational laxity will occur about a point on the medial side.
Changes in Glenohumeral Joint Mechanics, Shoulder Strength, and Clinical Outcomes Over Two Years After Rotator Cuff Repair
Authors: Bey Michael J. , Kline Stephanie K. , Deneweth Jessica M. , Haladik Jeffrey R. , Kolowich Patricia A. , Lock Terrence R.
Published: July 2013

Rotator cuff tears are a common injury that have a major impact on function, comfort, and medical care costs. Treatment procedures rely implicitly on the belief that restoring normal glenohumeral joint (GHJ) mechanics is necessary to obtain a satisfactory clinical result. However, it is unknown if rotator cuff repair restores and maintains normal GHJ mechanics. Thus, the objective of this study was to compare in-vivo GHJ contact patterns between the repaired and contralateral shoulders of patients who underwent rotator cuff repair. We hypothesized that GHJ contact patterns would be significantly different between repaired and contralateral shoulders.