bluuebunny/crossref_metadata_2025 huggingface dataset:
An Investigation on the Effect of Groove Dimensions and Inclination on Cementless Femoral Component in Hip Arthroplasty
Authors: Rawal B. R. , Bhatnagar Naresh
Published: July 2013

The optimal surface for a cementless femoral stem has been the subject of debate for the past several years. Several researchers have stressed the need for research on how an implant surface shape contributes to long-term stability, after implantation, in the field of orthopaedics. The introduction of optimized grooves on an implant surface may enhance long-term stability of an implant. This study thus analyzes the effect of different groove dimensions and angles with a transverse plane on stress transmission by a load at the proximal femur by using finite element analysis. Results suggest that the tendency of stress transmission differs depending on the size, position and angle of the grooves. So, optimized groove size and inclination plays a vital role for long-term stability of cementless femoral stems.
Microscale Fiber Network Structure Affects the Simulated Macroscale Failure of Collagen Gel Tissue Analogs
Authors: Hadi Mohammad F. , Barocas Victor H.
Published: July 2013

The microstructure of a soft tissue plays a significant role in shaping its failure properties at much larger length scales. However, delineating the specific relationship between microstructure and failure response has proven enigmatic. Important recent work has included the efforts of Quinn et al. to assess experimentally microscale collagen fiber realignment precipitated by mechanical damage in the facet capsular ligament [1] and of Ritter et al. to model the failure of extracellular matrices using a zipper network model [2]. In the present study, we employ a multiscale finite-element damage model to explore the impact of microscale fiber network morphology on the macroscale failure properties of a collagen gel tissue analog. To simulate damage, the model links the failure of discrete collagen fibers in networks at the microscale to the overall macroscale stress-strain response of the tissue analog. The model has the advantages of being able to accommodate a wide range of microstructural network morphologies and to simulate complex macroscale tissue geometries. By furthering our ability to link tissue microstructure to failure, we can improve methods for assessing injury in native soft tissues, enhance treatments for injured tissues, and engineer more resilient replacement tissues.
Modeling Growth in Tissue Expansion
Authors: Zöllner Alexander M. , Buganza Tepole Adrián , Kuhl Ellen
Published: July 2013

Skin expansion enables the correction of birthmarks, burn injuries, and reconstruction of breasts after tumor removal. The astonishing properties of human skin allow us to implant and inflate a balloon expander next to a defect to grow skin with matching color, texture, hairiness, and thickness while minimizing the risk for rejection and scaring3. In order to grow skin in situ, the balloon expander is placed in a subcutaneous pocket of approximately the expander size and shape, see Figure 1. Inflating the balloon gradually between four to eight weeks after surgery triggers growth by overstretching the skin.
Biomechanical Characteristics of Aortic Aneurysms Generated in Fibulin-4 Deficient Mice
Authors: Speelman L. , Moltzer E. , van der Heiden K. , van Heijningen P. , van der Steen A. F. W. , Essers J. , Gijsen F. , Wentzel J.
Published: July 2013

Aortic aneurysms affect approximately 5% of the elderly population and aneurysm rupture is responsible for a significant number of deaths in the western world. Risk factors for aortic aneurysm include high cholesterol, high blood pressure, and smoking. Fibulin-4 is a glycoprotein, which is expressed in medial layers of blood vessels and a critical component for the structural integrity and elasticity of the aortic wall [1]. Mice with reduced levels of Fibulin-4 develop aortic abnormalities similar to Fibulin-4 patients, such as dilation of the ascending aorta. A 4-fold reduction of Fibulin-4 expression (fib-4R/R) causes a severe dilation, while a mice with a 2-fold reduction (fib-4+/R) show an onset of aneurysm formation, comparable with the development of an aneurysm in aging humans [2].
Transient Tensile Facet Capsular Ligament Loading Above the Mechanical Threshold to Induce Pain Also Regulates Spinal Neuronal Hyperexcitability
Authors: Crosby Nathan D. , Dong Ling , Winkelstein Beth A.
Published: July 2013

Traumatic neck injuries are a primary cause of chronic pain, with the cervical facet joint and its capsule being a common source of the pain. During these injuries, the facet capsular ligament undergoes excessive stretching that can initiate pain [1]. Behavioral sensitivity is produced as early as 1 day after facet capsule stretch, which suggests that the excitatory systems in the spinal cord are modulated by certain tissue loading conditions. In particular, the signaling protein PKCε has been implicated in glutamate release in inflammatory pain [2] and is increased in afferents after painful facet injury [3]. Also, neuronal hyperexcitability has been detected after painful, but not nonpainful, facet joint distraction [4]. Despite the involvement of spinal neuronal activation in pain, the time course of its development and its relationship to painful mechanical facet joint injury is unknown.
Characterization of Depth-Dependent Mechanical Properties in Bio-Titanium Hybrid Osteochondral Tissue Engineered Constructs
Authors: Nover Adam B. , Wood Katherine C. , O’Connell Grace D. , Essner Aaron P. , Klein Robert W. , Napolitano Anthony P. , Lima Eric G. , Ateshian Gerard A. , Hung Clark T.
Published: July 2013

With cartilage autografts and allografts in short supply, tissue engineered osteochondral (OC) grafts offer an alternative [1]. These constructs are comprised of a chondrocyte-seeded hydrogel region and a porous, bone-like base. Our laboratory has shown growth of more robust osteochondral constructs on clinically-relevant metal substrates (eg. tantalum) as opposed to devitalized bone, and these constructs have been evaluated in vivo [1,2]. Due to the presence of the base, it is expected that transport of nutrients and chemical factors in OC constructs will differ from transport in chondral-only constructs (Fig. 1, bottom-left). Depth-dependent mechanical properties of chondral-only constructs have been measured, yielding a “U-shaped” strain profile, in which the construct is stiffest on the edges and softest in the center. However, depth-dependent properties have not been measured in tissue engineered OC grafts [3].
Modeling the Anisotropic Properties of Human Skin Tissues
Authors: Koys Theresa M. , Nguyen Thao D.
Published: July 2013

The anisotropic properties of human skin tissues are important for many applications, such as medical device/patient interface modeling. Typically, uniaxial [1] and biaxial [2] tests are used for mechanical testing of skin. The inflation method, less commonly used for skin, presents the advantages of imposing a biaxial deformation state more similar to that found in vivo. For methods that incorporate full-field displacement measurements, the material directions can be determined from the test rather than pre-selected prior to testing [3]. Furthermore, the mechanical response measured by the inflation method has been shown to be insensitive to preconditioning [4].
Strain Analysis in the Scapula After a Reverse Total Shoulder Arthroplasty
Authors: Patel Radhika J. , Zhang Chi , Gao Yingxin
Published: July 2013

A reverse total shoulder arthroplasty (RTSA) is strongly suggested for patients who suffer from rotator cuff (RTC) arthropathy, where RTC deficiency causes abnormal loading leading to articular cartilage damage. Studies show that 47% of RTSA patients have rotator cuff arthropathy and 27% have some form of osteoarthritis (OA) [1].
Investigation of Stress Fiber and Focal Adhesion Evolution Under Applied Mechanical Loading
Authors: Ronan William , Deshpande Vikram S. , McMeeking Robert M. , McGarry J. Patrick
Published: July 2013

Numerous in-vitro studies have established that cells possess the ability to react to their physical environment. However, the mechanisms underlying such phenomena are poorly understood. Recent experimental studies have employed arrays of microposts to measure the active contractile forces generated by cells [1]. A bio-chemo-mechanical model has been used to predict the response of smooth muscle cells on such array [2]. However, this study only considers stress fiber (SF) contractility and does not examine the role of focal adhesion (FA) formation in the contractile response of cells. Recent studies have subjected cells, which are adhered to micropost arrays, to both local and global cell deformation by moving the supporting microposts. Computational investigation of the cellular contractility must be capable of capturing the active response of SFs and FAs to externally applied loading.
Development of an Anatomically Realistic Left Ventricle Physical Model and Multi-Modality Experimental Platform for Validation of Patient-Specific Computational Simulations
Authors: Chaffins Brandon , Le Trung , Santhanakrishnan Arvind , Mirabella Lucia , Sotiropoulos Fotis , Yoganathan Ajit
Published: July 2013

Recent trends in bioengineering, also supported by the FDA [1], highlight the importance of experimental validation of numerical solvers used in medicine in order to use numerical solvers for surgical planning. Efforts to improve the diagnosis of left heart diseases have pointed to the importance of hemodynamic patterns in the left ventricle [2] and the use of CFD simulations could aid in repair and treatment of left heart disease. In this study, we aim to experimentally validate the Curvilinear Immersed Boundary solver (CURVIB) [3] to use patient specific data for simulations. As a first step, an idealized left heart model with a single deforming wall was used for comparison of the diastolic intra-ventricular flow field between experimental and CFD results. The inputs for the numerical solver include the dynamics of LV wall motion as well as the mitral and aortic flows. We have achieved good agreement between the experimental and CFD and our goal is to translate the solver to use clinical data. We present a reconstruction method for the LV deformation from normal volunteer MRI images and an anatomically realistic LV physical model that has been designed for validation.
Effect of Glenoid Implant Orientation and Depth on Potential Cement Failure in Total Shoulder Arthroplasty Using Finite Element Analysis
Authors: Yongpravat Charlie , Levine William N. , Bigliani Louis U. , Gardner Thomas R. , Ahmad Christopher S.
Published: July 2013

One of the most common complications of total shoulder arthroplasty (TSA) is glenoid component loosening due to implant-cement fixation failure. High cement stresses resulting in fracture are believed to result from malpositioning the glenoid implant [1]. Ideal glenoid preparation and placement, however, are not always achievable due to significant anatomical alterations caused by arthritis resulting in posterior glenoid erosion and increased glenoid retroversion. To our knowledge, prior research has not compared the effects of insufficient reaming depth and incomplete version correction on the likelihood of cement mantle failure. The purpose of this study was to investigate how the degree of correction of the glenoid vault affects cement mantle stress and potential cement failure.
3D Reconstruction of Scleral Shell Using Three Dimensional Active Contours
Authors: Ayyalasomayajula Avinash , Vande Geest Jonathan P.
Published: July 2013

There is a general consensus that elevation in intraocular pressure (IOP), due to a reduced outflow of aqueous humor, is a major factor leading to primary open-angle glaucoma (POAG). Studies indicated that the damage of the optic nervehead (ONH), due to the biomechanical environment in and around the lamina cribrosa (LC), could be an important event leading to POAG [Morgan]. Since experimentally testing tissues of such small dimensions is difficult, many researchers resorted to computationally model the biomechincal environment inside the eye [Avatar, Kobayashi, Sigal, Uchio, Xu, Tandon]. It also gives the flexibility to parametrically study and isolate the effects of individual tissues on the IOP and LC. Many of these studies involve stress analysis on a hypothetical geometry (for e.g. spherical or axisymmetric hemisphere) using a variety of constitutive models (for e.g. elastic, biphasic etc) to study the static, and dynamic response of the IOP [Tandon, Sigal].
The Effect of Pubococcygeus Muscle Avulsion on the Anterior Vaginal Wall Support: A Biomechanical 3D Finite Element Modeling Study
Authors: Chen Luyun , Ashton-Miller James A. , DeLancey John O. L.
Published: July 2013

Levator ani muscle defects are common in women after vaginal birth and have been associated with the development of pelvic organ prolapse (Kearney et al 2006, DeLancey et al 2007, and Dietz and Lanzarone 2005). Sometimes there is a loss of muscle substance but the overall shape of the muscle remains intact. In other instances, gross distortion of the muscle origin occurs (Huebner et al. 2008) presumably due to avulsion of muscle from the pubic bone. Theoretical biomechanical modeling work has showed that even with intact pubic origin, weakening of levator ani muscle leads to the development of cystocele (Chen et al, 2009). The biomechanical effects of avulsion of the pubic origin of the pubococcygeal muscle have not been fully explored. The objective of this study if to use a finite element model to perform a biomechanical analysis of how pubococcygeus muscle avulsion affects the descent of the anterior vaginal wall during a Valsalva.
Measuring Strain in Bone Cement With Carbon Nanotubes
Authors: Melander Jennifer R. , Holmes Ryan R. , Yao Xiaomei , Weiler Rachel A. , Eick J. David
Published: July 2013

While great strides have been made in the design of dental composites and orthopaedic implants, improvements are still needed. For instance the life span of dental polymer composites is known to be significantly shorter than traditional amalgam restorations [1]. Similarly, the early failure rate of orthopaedic implants often leads to an intentional delay in the treatment of painful, debilitating joints to ensure patients don’t outlive the functional life of their prosthetics [2]. Stress concentrations within biomaterials may be partially to blame for these premature failures.
Not Just Inductive: A Critical Mechanical Role for the Endoderm During Heart Tube Assembly
Authors: Varner Victor D. , Taber Larry A.
Published: July 2013

The heart is the first functioning organ to form during development. Similar to other organ primordia, the embryonic heart forms as a simple tube — in this case, a straight muscle-wrapped tube situated on the ventral side of the embryo. During gastrulation, the cardiac progenitors reside in the lateral plate mesoderm but maintain close contact with the underlying endoderm. In amniotes, these bilateral heart fields are initially organized as a pair of flat epithelia that move toward the embryonic midline and fuse above the anterior intestinal portal (AIP) to form the heart tube. This medial motion is typically attributed to active mesodermal migration over the underlying endoderm. In this view, the role of the endoderm is two-fold: to serve as a mechanically passive substrate for the crawling mesoderm and to secrete various growth factors necessary for cardiac specification and differentiation.
Treatment Efficacy of Laser Photothermal Therapy Using Gold Nanorods: Tumor Shrinkage Study
Authors: Manuchehrabadi N. , Toughiri R. , Cai H. , Zhu L. , Attaluri A. , Edziah R. , Lalanne E. , Ma R. , Johnson A. M. , Bieberich C.
Published: July 2013

Gold nanorods can be tuned to a specific laser wavelength and serve as strong laser energy absorbers. Due to the powerful optical absorption, the laser energy is concentrated in an area congregating by nanorods, and then the energy absorbed can be transferred to the surrounding tumor tissue by heat conduction.1–4 Previous studies have shown a wide range of heating parameters with or without temperature measurements. Our previous experiment4 has demonstrated that using only 0.1 cc gold nanorod solution can lead to tumor temperature higher than 50°C when the laser irradiance is only 2 W/cm2. Based on the measured temperature elevation and heating duration, thermal damage to the tumor is highly likely. However, some researchers raised the question whether temperature sensors used in those experimental studies are truly reflecting the temperatures in the tumors. The objective of this study is to measure quantitatively tumor shrinkage after laser irradiation to evaluate efficacy of laser photothermal therapy.
Polymerization Stress and the Influence of TOSU Addends on Methacrylate Composites
Authors: Holmes Ryan R. , Melander Jennifer R. , Weiler Rachel A. , Schuman Thomas P. , Kilway Kathleen V. , Eick J. David
Published: July 2013

The aesthetic appeal of composite-resin restoratives promotes their use, however their functional life is significantly shorter when compared to their metal counterparts.1 One possible reason is the effect of polymerization stress on marginal integrity. Shrinkage of the composite, and its associated stress, has been found to cause gap formation and stress interactions between the restorative and the adhesive. These gaps offer an ideal niche for bacteria, and, when compounded by the mechanical strain of chewing, can lead to premature failure of the restorative.2,3 Additionally, it is well known that incomplete conversion of the double bonds occurs during methacrylate polymerizations.4–7 A high degree of conversion is needed to prevent the presence of potentially hazardous monomers.8
In Situ Hierarchical Strain Transfer From the Articular Cartilage Surface to the Chondrocyte Nucleus
Authors: Henderson Jonathan T. , Neu Corey P.
Published: July 2013

Osteoarthritis (OA) is a disabling disease, commonly thought of as the “wear and tear” of articular cartilage, afflicting 27 million Americans [1]. Multiple (e.g. biomechanical and biochemical) factors [2] contribute to maintenance of healthy joints through chondrocyte and extracellular matrix interactions. Interestingly, volumetric contractions of nuclei exhibit a zonal dependence [3], suggesting that nuclear mechanics may play a key role in the maintenance of healthy tissue by mechanically-mediated pathways.
Effect of Housing System on Properties of Pullet Bones
Authors: DeLand Trevor S. , Dudgeon Ross E. , Orth Michael W. , Karcher Darrin M. , Haut Roger C.
Published: July 2013

Recently, attention has been brought to the welfare of laying hens and the benefits provided by progressive housing systems [3]. Conventional battery cage (CC) systems provide each bird with access to feed and water at all times with room to move. One of the new housing types being implemented, referred to as a cage-free aviary system (AV), is much larger than conventional cages and houses more birds. Aviary systems comprise multiple levels providing more opportunity for movement and exercise. Hens can forage and dust bathe in an open communal area, have access to perches, and nest boxes. However, for mature hens to fully utilize an AV, pullets (pre-egg production birds) must be reared in a similar environment.
Quantitative Studies of Fibronectin Adsorption on Submicron Scaffolds
Authors: Regis Shawn , Jassal Manisha , Youssefian Sina , Rahbar Nima , Bhowmick Sankha
Published: July 2013

Fibronectin plays a crucial role in adhesion of several cell types, mainly due to the fact that it is recognized by at least ten different integrin receptors. Since most cell types can bind to fibronectin, it becomes involved in many various biological processes. The interaction of cells with ECM proteins such as fibronectin provides the signals affecting morphology, motility, gene expression, and survival of cells [1]. Fibronectin exists in both soluble and insoluble forms; soluble fibronectin is secreted by cells and exits in cell media or body fluids, whereas insoluble fibronectin exists in tissues or the extracellular matrix of cultured cells [2]. The ability to control adsorption of fibronectin on tissue engineering scaffolds would therefore play a huge role in controlling cell attachment and survival in vivo. This can be achieved through surface functionalization of the scaffolds. The goal of these studies is to use molecular dynamics (MD) simulations to mechanistically understand how fibronectin adsorption is enhanced by surface functionalization of submicron scaffolds.
High-Risk Tissue Distribution in the Human Proximal Femur Under Sideways Fall Loading
Authors: Nawathe Shashank , Romens Alissa , Bouxsein Mary L. , Keaveny Tony M.
Published: July 2013

Despite the central role of femoral strength in the etiology of osteoporotic hip fractures [1], the associated micromechanical basis of femoral strength remains poorly understood. Cadaver studies [2] using biomechanical testing have established that both the cortical and trabecular bone contribute to the structural integrity of the proximal femur but these studies did not address mechanisms. Addressing mechanisms, theoretical and finite element continuum analyses have assessed cortical-trabecular load sharing and have described stress and strain distributions throughout the proximal femur [1,3]. However, the regions of the bone at highest risk of initial failure remain unclear, in part because the continuum nature and low spatial resolution of these previous analyses render them incapbable of capturing load transfer associated with the microstructure of the trabecular bone and the sometimes thin cortex. Overcoming this limitation, micro-CT-based finite element analysis has recently been applied to the entire proximal femur [4], but so far only two femurs have been analyzed and thus reported trends are difficult to generalize. To extend this recent work and provide further insight into the microstructural basis of femoral strength, we applied micro-CT based finite element analysis to investigate femoral micro-mechanics in a cohort of elderly human proximal femurs.
Quantification of the Ranges of Motion of the CMC Joints of the 4th and 5th Digits of the Human Hand In Vivo Using Computed Tomography
Authors: Buffi James , Hoover James , Crisco Joseph J. , Murray Wendy M.
Published: July 2013

Over 80% of activities of daily living involve grasping or seizing objects with the hand [1]. The carpometacarpal (CMC) joints of the hand and wrist, the five joints that articulate the distal row of carpal bones and the proximal bases of the five metacarpal bones, are particularly important for prehensile tasks involving the opposition of the ring and little fingers with the thumb, such as during precision grasping. In addition, impairment of the CMC joints can weaken grip strength [2].
Frictional Coefficient of TMJ Disc and Condylar Cartilage
Authors: Bonnevie Edward D. , Barito Laura , Aldridge Matthew , Wang Liyun , Burris David L. , Lu X. Lucas
Published: July 2013

Temporomandibular joint (TMJ), the only diarthrodial joint in human head, is composed of two articulating bones covered by cartilage with an extra disc between the two cartilage surfaces. The rotation and gliding motions of TMJ allow us to talk, chew, and yawn. Dislocation of the disc or degeneration of the cartilage can severely ruin the congruity and integrality of TMJ and further leads to TMJ disorders (TMD). Histology studies showed that the composition and structure of condylar cartilage do not resemble any other fibrocartilages [1], our recent study also found that the condylar cartilage is much softer than cartilage in other joints [2]. The condyle is fully covered by the disc, which glides on the condyle cartilage during daily activities [3]. Little is known about the frictional coefficients of these cartilaginous tissues in TMJ. In this study, using a novel custom-built tribometer, we propose to investigate: 1) the frictional coefficients of condylar cartilage and disc at five different regions, and 2) the dependency of frictional coefficient on sliding speed and loading magnitude.
Validation of Knee Load Predictions During a Dual Limb Squat and Calfrise
Authors: Guess Trent M. , Stylianou Antonis , Kia Mohammad
Published: July 2013

Knowledge of knee loading would benefit prosthetic design, development of tissue engineered materials, orthopedic repair, and management of degenerative joint diseases such as osteoarthritis. Musculoskeletal modeling provides a method for estimating in vivo joint loading, but validation of model predictions is challenging. Data provided by the “Grand Challenge Competition to Predict In-Vivo Knee Loads” for the 2012 American Society of Mechanical Engineers Summer Bioengineering Conference [1] provides data from an instrumented prosthetic knee that can be used to validate load predictions. The Grand Challenge data set includes implant and bone geometries, motion, ground reaction forces, electromyography (EMG) as well as measured knee loading. Presented here are muscle driven forward dynamics simulations with a prosthetic knee for two of the calibration gait trials (SC_2legsquat and SC_calfrise) provided with the Grand Challenge data set. The calibration trials include the instrumented knee measurements and are provided to help “calibrate” models used in the Grand Challenge competition. Inputs to model simulations were experimental marker motion and outputs included muscle force, ground reaction forces, ligament forces, contact forces, and knee loading. Experimental measurements of knee loading, ground reaction force, and muscle activations were compared to model predictions.
Intervertebral Disc Shape Variation and its Relationship to Degeneration Using Principal Components Analysis of a Population of MR Images
Authors: Peloquin John M. , Yoder Jonathon H. , Jacobs Nathan T. , Moon Sung M. , Wright Alexander C. , Vresilovic Edward J. , Elliott Dawn M.
Published: July 2013

Degeneration of the intervertebral disc (IVD) is implicated in low back pain, which is a costly and prevalent disease. Since the IVD is a mechanically active organ, it is important to consider its mechanical behavior as one factor in the degenerate pathology. Strain can be measured directly by imaging methods, but the stress distribution within the disc must be calculated. The stress distribution for a particular strain state is dependent on the IVD’s material properties and its geometry. While the material properties of the tissues comprising IVD have been extensively studied, its three-dimensional geometry remains incompletely characterized. Prior whole-disc models have been constructed from single IVDs. While this approach ensures that the geometry has a physiological basis, it is uncertain the degree to which results from a single IVD shape can be generalized to the entire population.
Development of a Weighted Functional Finger Space
Authors: Leitkam Sam , Bush Tamara Reid
Published: July 2013

The human hand is a complex biological system that is used every day for a range of applications, from sewing and typing on a cell phone, to brushing teeth, and opening doors. The hand’s ability to adapt to this large range of applications is based upon the human body’s ability to manipulate many degrees of freedom within the hand.
Fracture Patterns From Three-Point Bending of Sheep Femora
Authors: DeLand Trevor S. , Kendell Ashley E. , Fenton Todd W. , Haut Roger C.
Published: July 2013

Fracture patterns of long bones broken under various loading conditions have been well documented [1,8]. Of particular interest in the current study was the wedge or “butterfly” type fracture that occurs as a result of bending forces on a bone. Butterfly fractures generally consist of a characteristic “Y” shape across the long axis [1,7]. While no studies were found that examine the mechanism of such a fracture, it is generally accepted and widely published that the bottom of the Y fracture is found on the tensile side and the top split portion occurs on the compressive side of the neutral axis (Figure 1). This phenomenon is explained using basic solid mechanics principles. Since the tensile strength of bone is 133 MPa compared to a compressive strength of 193 MPa [6], bending initiates a transverse fracture on the tensile side. However, across the neutral axis, compressive forces dominate and tensile failure is thought not to continue. Since the shear strength of bone is 51.6 MPa [10], less than half the compressive strength, the bone appears to fail along the planes of maximum shear stress at 45° to the transverse split [3].
MRI-Based Strains and Relaxation Mapping in Human OA Articular Cartilage
Authors: Griebel Adam , Trippel Stephen , Neu Corey P.
Published: July 2013

Osteoarthritis (OA) is a degenerative disease of articular cartilage in synovial joints. The mechanical function of cartilage declines during OA progression, including the softening of the tissue coupled with increased friction and wear [1,2]. Structurally, cartilage wear is regionally nonuniform over the entire articular surface, and load-bearing regions often show more OA severity compared to non-load-bearing regions in the same joint [2].
3-D Quantitative Microanatomy of Rat Kidney Podocytes as Determined by Serial Block-Face Scanning Electron Microscopy
Authors: Azeloglu Evren U. , Stothers Mark , Deerinck Thomas J. , Falkenberg Cibele , Chen Yibang , He John Cijiang , Hone James C. , Loew Leslie M. , Ellisman Mark H. , Iyengar Ravi
Published: July 2013

The shape of a cell is critical for proper signaling and resultant biological function [1]. Podocytes, kidney visceral epithelial cells, have a distinctive morphology with interdigitating foot processes that wrap around the capillaries of the glomeruli and, together with endothelial cells and the basement membrane, form the glomerular filtration barrier. In addition to forming the filtration barrier, slit diaphragms that connect the alternating foot processes from two podocytes are thought to be signaling hubs that regulate cell morphology and function.
Viscoelastic Properties of Living Human Brain by Local Frequency Estimation Applied to Distortional Wave Fields
Authors: Clayton Erik H. , Genin Guy M. , Bayly Philip V.
Published: July 2013

The use of magnetic resonance imaging (MRI) to characterize the biomechanical material properties of tissue in vivo is an emerging application. Local frequency estimation (LFE) [1] has been used to locally extract the wavenumber κ from displacement wave fields in order to estimate the elastic shear modulus via the well-known phase velocity relation [2,3]. LFE-based inversion is attractive because it allows material parameters to be estimated without explicitly invoking the equations of motion, thus obviating the need to numerically compute the Laplacian. In this study, viscoelastic properties of brain tissue at multiple frequencies were obtained by local frequency estimation (LFE) applied to distortional wave fields. This avoids artifacts from the presence of unmodeled longitudinal waves. By use of the equation describing planar distortional wave propagation in a lossy medium, the viscoelastic shear moduli were approximated.
Sex Differences in the Mechanical Behavior of the Decellularized Rat Left Ventricle
Authors: Witzenburg Colleen , Vanderheiden Sarah , Nagel Tina M. , Kren Stefan M. , Taylor Doris A. , Barocas Victor H.
Published: July 2013

There are fundamental differences in the size and performance of male and female hearts. Even after adjustments for height and body surface area, the left ventricle of a healthy male is larger in both volume and mass [1]. There are differences in contractile performance between papillary muscle from male and female rats with male rats showing slower responses in both isometric and isotonic tests [2]. It is less clear, however, whether the underlying structure or mechanical properties vary between sexes as well. Of particular interest to us is the extracellular matrix (ECM) of the ventricular wall, which provides structural stability to the heart. This matrix can be isolated by perfusion decellularization [3].
Development of a Microfluidic Device Embedding High-Conductivity Flexible Electrodes for Three-Dimensional Cell Culture Stimulations
Authors: Rasponi Marco , Piraino Francesco , Cagol Nicola , Moretti Matteo , Fiore Gianfranco B. , Redaelli Alberto
Published: July 2013

Successful treatment of cardiovascular diseases has so far been limited by the lack of suitable autologous tissue to restore injured tissues. Currently, a novel encouraging frontier for such treatment is represented by tissue engineering [1]. Although traditional bioreactors for cardiac tissue engineering, based on a classical macro-scale approach, are widely used, research for identifying effective stimulation patterns has not lead to robust results yet. In this sense, the phenomena driving cell growth and differentiation become more addressable in reduced-scale systems, and microfluidics represents a valid alternative approach to overcome traditional bioreactors limitations. In order to favor the differentiation paths, recently developed microfluidic bioreactors tend to increase the control within cell culture chambers by coupling mechanical, electrical, thermical or optical effects. In particular, stem cell differentiation into cardiomyocytes seems to draw beneficial effects from electrical and mechanical stimulations [2]. This work introduces a simple method of embedding conductive and flexible material within microfluidic devices as a means to realize microscale bioreactors for cell electro-mechanical stimulation. Thanks to the proposed technology, high conductivity three-dimensional (3D) electrodes can be simply realized.
Injectable and Photocrosslinkable Laminin Functionalized Biomaterials for Intervertebral Disc Regeneration
Authors: Francisco Aubrey T. , Mancino Robert J. , Jeong Claire G. , Karikari Isaac O. , Bowles Robby D. , Craig Stephen L. , Setton Lori A.
Published: July 2013

Biological and anatomical changes of intervertebral disc (IVD) degeneration frequently occur in the nucleus pulposus (NP) [1]. Changes in NP matrix composition coincide with the loss of a distinct notochord derived cell population [2],[3], which may have the potential to generate or maintain a functional NP-like matrix. Immature NP cells reside in an environment rich in laminin and express specific laminin-binding receptors [4],[5]. Additionally, NP cells attach in higher numbers to laminins as compared to cells isolated from other regions of the IVD [6]. Our initial work demonstrated that matrix protein and stiffness modulate NP cell-cell interactions upon surfaces [7], with results that suggest soft, laminin-functionalized hydrogels may be useful for promoting an NP-like cell phenotype.
CFD Challenge: Solutions Using a Second Order Accurate, Stabilized Finite Element Solver
Authors: Arzani Amirhossein , Wilson Nathan , Shadden Shawn C.
Published: July 2013

Dr. Shadden’s group focuses on dynamical systems methods to quantify complex flow, with particular focus on the cardiovascular applications in order to better understand hemodynamic phenomena. For this CFD challenge, simulations were performed by Amirhossein Arzani using a customized version of the finite element solver integrated into SimVascular [1].
Human Tibial Cartilage Reveals Non-Linear and Non-Uniform Regional Topography Under Physiological Loading Rates
Authors: Deneweth Jessica M. , Newman Kelly E. , Sylvia Stephen M. , McLean Scott G. , Arruda Ellen M.
Published: July 2013

Nearly 3% of individuals worldwide experience pain, immobility, and compromised quality of life due to knee osteoarthritis (OA)1. It has been widely accepted that joint mechanics play a critical role in the initiation and progression of knee OA2. A shift away from the normal joint motion, for example due to injury or malalignment, is believed to produce an abnormal pattern of cartilage loading that creates unusual and damaging stresses within the tissue. Accurate knowledge of cartilage’s normal mechanical response to physiological loading—and particularly the regional dependence of this response—is critical to successfully testing this theory. To our knowledge, little is known about the regionally-dependent mechanical response of healthy human tibial cartilage under physiological loading conditions. There is also a compelling need for more accurate cartilage data to be integrated into computational simulations of the knee joint. Hence, the purpose of this study was two-fold:

1) to characterize the typical stress-strain response of tibial cartilage at 21 locations across the tibial plateau when subjected to loading representative of human walking, and

2) to demonstrate that these 21 sites can be reduced to a small number of regions displaying significantly different average moduli.
An Immersed Porous Boundary Method for Computational Fluid Dynamics of Blood Flow in Aneurysms With Flow Diverters
Authors: Mihalef Viorel , Sharma Puneet , Kamen Ali , Redel Thomas
Published: July 2013

Intracranial aneurysms are pathological dilatations of a cerebral artery that may suffer rupture and lead to subarachnoid hemorrhage. Such a condition presents high morbidity and mortality rates for the patients concerned.
Directed Injection of Vertebroplastic Cement at the Site of a Lytic Metastatic Lesion Restores Strength With Minimum Injection Volume
Authors: Kiapour Ata M. , Truumees Eeric , Goel Vijay K. , Demetropoulos Constantine K.
Published: July 2013

Metastatic disease in the thoracolumbar spine represents a large and growing problem. These metastases can lead to pain, pathologic fracture, and neurologic compromise. Over the last two decades, the utilization of polymethylmethacrylate (PMMA) for percutaneous vertebral stabilization has increased. Most of the biomechanical and outcomes data addresses the use of vertebroplasty and kyphoplasty procedures for osteoporotic fractures [1,2]. Use of these procedures for metastatic disease enjoys a long clinical history, but the outcomes and complications are notably higher than in osteoporosis [3,4]. Newer formulations of PMMA used in advanced systems such as the Perimeter System (DePuy, Raynham, MA) may allow carefully controlled, anatomically directed PMMA application with far greater control. However, The relative benefits of these newer, proprietary systems have not been demonstrated. Proposed benefits of direct void reconstruction, as opposed to anterior vertebral body fill include: tumor lysis, decreased risk of later tumor growth with canal compromise, the ability to use less total PMMA, decreased impact on adjacent segment mechanics, and therefore, a decreased adjacent segment fracture risk. This study was conducted to examine and compare the biomechanical effectiveness of the cement augmentation (vertebroplasty) and directed PMMA injection using the Perimeter system.
Finite Element Analysis of Force Transmission in Skeletal Muscle Fiber
Authors: Zhang Chi , Gao Yingxin
Published: July 2013

Skeletal muscle has a complex hierarchical structure which is mainly composed of myofibers and the surrounding extracellular matrix (ECM) including endomysium, perimysium, and epimysium. To produce movement, force generated by individual myofibers has to be transmitted to the tendon. Previous studies have shown that many muscle fibers terminate within the fascicle without reaching either ends of the tendon[1,2], in which case force generated has to be transmitted laterally through the ECM to surrounding fibers and then to the tendon[3]. In this study, a two dimensional finite element (FE) model of a single muscle fiber was developed to determine the effects of ECM stiffness and tapered end angles of myofiber on lateral transmission of force in skeletal muscle.
Accumulation of Extracellular ATP in Porcine Nucleus Pulposus
Authors: Wang Chong , Gonzales Silvia D. , Gu Weiyong , Huang C.-Y. Charles
Published: July 2013

There are many reasons for people to miss work; one of the leading contributors is low back pain (LBP), which is believed to affect 80% of the population at some point during their lifetime. Suffering from back pain is the chief complaint of 5% of people who visit the doctor in the US [1]. The total medical cost related to low back pain in the US exceeds 100 billion dollars every year [2]. The cause of LBP is still unclear. However, recent studies revealed that intervertebral disc (IVD) degeneration is closely related to LBP [3]. IVD transfers loads and allows the spine to move through torsion, bending or compression [4–6]. There are two main anatomic regions in IVD: nucleus pulposus (NP) and annulus fibrosis (AF). The loss of notochordal cells in the NP region has been associated with the initiation of disc degeneration [7]. Our recent studies demonstrated that the adenosine triphosphate (ATP) production of notochordal NP cells was much higher than that of the AF cells while mechanical loading promoted ATP release from IVD cells [8]. Extracellular ATP (eATP) is a powerful signaling molecule that can mediate a wide variety of biological responses, such as cell metabolism, survival, and growth by binding to the purinergic receptors: G protein coupled receptor (P2Y) or ligand-gated ionotropic receptor (P2X) [9]. In addition, eATP is often rapidly hydrolyzed by several families of ectonucleotidases [10–12]. The by-products of eATP hydrolysis include inorganic pyrophosphate (PPi) and phosphate (Pi) which are closely related to mineral crystal formation and tissue calcification [12–15]. PPi and Pi released from eATP hydrolysis may contribute to endplate calcification which has been associated with disc degeneration. However, eATP accumulation in the IVD has not been studied yet. Therefore, the objective of this study was to investigate the accumulative level of eATP in the NP region of porcine IVD using a novel optical ATP sensor.
Effects of Quadriceps and Hamstrings Ratio on ACL Strain During Landing Activities
Authors: Quatman Carmen E. , Kiapour Ata M. , Kiapour Ali , Levine Jason W. , Wordeman Samuel C. , Demetropoulos Constantine K. , Hewett Timothy E. , Goel Vijay K.
Published: July 2013

Over 100,000 anterior cruciate ligament (ACL) injuries occur annually in the United States [1]. Of these, 70% are classified as non-contact, many of which occur subsequent to a landing from a jump [2]. While most agree that quadriceps (Q) and hamstrings (H) have a significant contribution in knee biomechanics, the role of quadriceps and hamstrings muscle loads and their ratio (Q/H) in ACL injury remains controversial. Understanding muscle recruitment in high risk activities may improve our knowledge of ACL injury mechanisms. Such insight may improve current prevention strategies to decrease the risk of ACL injury and damage to secondary anatomical structures, all of which may in turn minimize associated posttraumatic knee osteoarthritis. As in vivo quantification of muscle loads remains challenging, especially under dynamic conditions, validated finite element (FE) models of the knee can be used to characterize the role of muscle loads in ACL injury. FE analysis has provided considerable insight into knee joint biomechanics, including ligament function, ligament reconstruction technique and implant design. This study utilized a validated FE model of the knee joint to study the effects of quadriceps to hamstrings ratio (Q/H) on ACL strain during a simulated landing from a jump. We hypothesized that both the ratio and magnitude of muscle loads are critical determinants of ACL loading. Further, a threshold may be reached as the magnitude of quadriceps load exceeds hamstrings load.
Prediction of the Impact of Craniospinal Compliance on the Relative Timing of Arterial and Cerebrospinal Fluid Pulsations and Perivascular Fluid Flow Into the Spinal Cord
Authors: Martin Bryn A. , Stergiopulos Nikos
Published: July 2013

Craniospinal compliance (CC) has been hypothesized to have importance in craniospinal disorders such as hydrocephalus and syringomyelia in which tissue edema occurs. In this study we assess the impact of CC on 1) the relative timing of spinal cord blood flow (SCBF) and cerebrospinal fluid (CSF) pulsations and 2) perivascular flow (PVS) into the spinal cord (SC). A previously developed coupled model of the cardiovascular and CSF system is utilized to obtain the results. The results predict that CC can significantly alter the relative timing of arterial and CSF pulsations in the spine and total perivascular flow to the SC. CC was found to have the greatest impact on relative timing and PVF in the lumbar spine and to a lesser extent in the cervical and thoracic spine. A reduction in CC resulted in increased PVF to the SC that might help to explain tissue edema present in craniospinal disorders with reduced CC.
Finger Flexor Tendon Excursion During Computer Keyboarding
Authors: Toosi Kevin K. , Boninger Michael L.
Published: July 2013

Previously our laboratory demonstrated that a continuous one-hour keyboarding assignment caused acute changes in the ultrasonographic measures of the median nerve.1 We also attempted to correlate these changes to a variety of contributing factors, such as individual features, as well as certain biomechanical variables. In this study, our objective was to quantify the amount of tendon travel as a function of keyboarding and investigate the effects of tendon travel on the median nerve ultrasonographic measures.
Global Quasi-Static Mechanical Characterization of the Human Knee Under Single- and Multi-Axis Unconstrained Loading Conditions
Authors: Kiapour Ata M. , Quatman Carmen E. , Ditto Richard C. , Levine Jason W. , Wordeman Samuel C. , Hewett Timothy E. , Goel Vijay K. , Demetropoulos Constantine K.
Published: July 2013

A substantial number of knee injuries are reported in the United States annually, and are principally observed among young athletes. ACL (anterior cruciate ligament) injury is one of the most common and devastating knee injuries [1]. Many factors influence such injuries, from anatomical variability to magnitude and direction of loading. A better understanding of knee biomechanics and injury mechanisms may improve current preventative, surgical and rehabilitation strategies, and thus, mediate injury risk. Considerable study of knee joint biomechanics under various modes of loading has been undertaken [2–4]. Additional work is needed to characterize the effects of different loading factors on knee biomechanics, especially ACL loading patterns under more physiologically relevant conditions. The purpose of this study is to develop a new technique to investigate the effects of various single- and multi-axes loading conditions on knee kinematics, ACL and MCL (medial collateral ligament) strains, and TF (tibiofemoral) articular cartilage pressure distribution under quasistatic loading conditions that simulate various weight bearing activities.
Aging Related Changes in the Kinematics of Walking: A Potential Pathway to Changes in Cartilage Morphology
Authors: Boyer K. A. , Andriacchi T. P.
Published: July 2013

Age-related changes in spatio-temporal and sagittal plane walking mechanics are well documented [1, 2]. These changes along with age-related changes in muscle strength, muscle activation patterns and ligament stiffness [3] may also lead to changes in both rotational and translation motions at the knee. It has been suggested that alterations in the normal kinematics of the knee related to aging may be a contributing factor to the increased incidence of knee osteoarthritis (OA) with aging [4].
Spatial Mapping of Moisture Content and Cellular State During Desiccation Preservation in a Sessile Droplet
Authors: Oliveira Matthew , Jimenez-Rios Jorge L. , Fowler Alex , Bhowmick Sankha
Published: July 2013

The use of sessile droplets in desiccation protocols has been brought into question due to potential inhomogeneity within the samples [1]. The moisture content and the corresponding viability that gets recorded, in most viability studies, represents that of the whole sample and does not account for any variation that may be present within the drop. One reason that trehalose is added to desiccation media as a biopreservative is to create a glassy state around the cell at certain moisture contents [2]. This makes it important to know the local residual moisture contents to better analyze viability results and whether or not the cells are actually capable of reaching a glassy state.