bluuebunny/crossref_metadata_2025 huggingface dataset:
A Structural and Microstructural Model for Tendon and Ligament Stress-Stretch Response
Authors: Hurschler Christof , Vanderby Ray
Published: July 2023

Collagen structural and microstructural organization are thought to contribute strongly to mechanical behavior in normal and healing tendon and ligament. Recent studies have attempted to correlate various collagen microstructural and structural features to material stiffness of healing ligaments (Frank et al., 1991, 1992; Padgett and Dahners 1992; Shrive et al., 1995). Other studies have suggested that progressive fiber failure may be a mechanism for damage accumulation and eventual failure of tendons and ligaments (Kennedy et al., 1976; Viidik 1978; Butler et al., 1984). It may also be an explanation for the observed permanent deformation of tendon at relatively low levels of strain (2–4%, Rigby et al., 1959; Abrahams 1967). Structural mathematical models for tendons and ligaments have been developed but few have incorporated more than one structural scale (i.e. fibril as well as fiber organization). The aim of this study is to develop a mathematical model for tendons and ligaments that will help to better understand the relationship between collagen structure, microstructure, and mechanical properties.
Curvature and Congruence Analysis of the Thumb Carpometacarpal Joint
Authors: Xu L. F. , Jenkins M. S. , Bucchieri J. S. , Strauch R. , Wang L. H. , Rosenwasser M. P. , Ateshian G. A. , Pawluk R. J. , Mow V. C.
Published: July 2023

Twenty-nine thumb carpometacarpal (CMC) joints, divided into a control group (normal and minimally degenerated joints) and a degenerated group (moderately and severely degenerated joints), were used to quantify CMC curvature and congruence. The saddle-shaped surface of the degenerated trapezium was found to be more concave and less convex than that of the control trapezium, with the greatest differences occurring in high-load-bearing (HLB) regions of the trapezium. No analogous differences were found in the metacarpal. Moreover, the degenerated group demonstrated greater joint congruence. The results suggest that curvature changes in the trapezial HLB regions may be highly associated with moderate or severe osteoarthritis of CMC joint.
The Knee Joint Mechanism
Authors: Wilson David R. , O’Connor John J.
Published: July 2023

Mathematical models have been developed to predict knee kinematics and mechanics for a number of applications, including the estimation of muscle, ligament and contact forces in activity and the prediction of soft tissue geometry within the joint.
Real Time Calcaneal-Cuboid Joint Pressure Measurements During Lateral Column Lengthening for Adult Acquired Flat Foot Repair
Authors: Nowak Michael D. , Cooper Paul S. , Shaer James
Published: July 2023

Real time contact pressure pads were used to evaluate calcaneal cuboid joint pressures as a result of lateral column lengthening. The Evan’s lateral column lengthening procedure has been used to restore the arch of the human foot after acquired adult flatfoot. There has been some question as to the consequences of this procedure with regards to calcanealcuboid arthrosis. This study evaluated the calcaneal cuboid contact pressure without lengthening, and after 5 and 10 mm lengthening. Each length was also evaluated with a compressive load of 350 N applied to the tibia. Total contact forces and pressures increased statistically as lengthening increased and after load application. Peak pressures also increased. Pressures exceeded 2.3 MPa in the loaded feet at 10 mm lengthening. Patients subjected to lateral column lengthening of 10 mm may be at increased risk for joint arthrosis.
The Collection of Material Properties of Vertebral Bone in Three Dimensions
Authors: Kenyeri Ronald L. , Grimm Michele
Published: July 2023

In order to increase the amount of information available on vertebral bone material properties, a three dimensional, nondestructive data collection system has been developed. To measure the deflections of a bone specimen in three dimensions, LVDTs were positioned in the three primary axes. LVDTs are used because their measurements will not be influenced by the MTS machine, and therefore the deflection read from the MTS machine can be used to check the LVDT output. LVDTs can also be rapidly and accuracy calibrated. Using LVDTs is a relatively inexpensive way to measure deflection along the three axes due to a unixial compression and, therefore, allows the calculation of Possion’s ratio with respect to an axis. This method can therefore calculate all six Possion’s ratios that are found in a 3 × 3 material matrix, quantities that are not well established for bone.
Development of a New Hardness Test for Cancellous Bone
Authors: Doppler Richard A. , Duquette Jeffrey J. , Hoffman Allen H.
Published: July 2023

A modified Rockwell superficial hardness test was developed for application to cancellous bone. Hardness tests conducted on cores from human and bovine specimens revealed that the average indent depth was strongly correlated with bone mineral density (r = −0.77). Although qualitative in nature, this new superficial hardness test is well suited to examine the spatial variation of bone strength in cancellous bone.
Computational Analysis of Fracture for the Human Femur
Authors: Vongpaseuth Thongsay , Marsh M. Virginia , Todd Beth A.
Published: July 2023

The cortical bone of the human femur was considered as a thin-walled non-circular cross section to analytically determine the required torque, T, to cause spiral fracture. Magnetic resonance images of a human subject’s right thigh were used for analysis. The minimum torque required for fracture was 73 N-m located 33.6 cm from the femoral head.
Internal Rotation Gait: A Compensatory Mechanism to Restore Abduction Capacity Decreased by Bone Deformity?
Authors: Arnold Allison S. , Delp Scott L.
Published: July 2023

Children with spastic cerebral palsy often walk with a troublesome in-toed gait. Excessive internal rotation, usually accompanied by excessive femoral anteversion, causes tripping and may lead to lateral patellar subluxation or external tibial torsion. Hence surgeries aimed at decreasing excessive internal rotation are often warranted.
The Effect of Posture, Loading Rate, and Diurnal Fluid Changes on the Propensity to Disc Prolapse
Authors: Lu Y. Michael , Gharpuray Vasanti M. , Hutton William C.
Published: July 2023

Sudden disc prolapse usually occurs due to a traumatic event when a high compressive force is suddenly applied to the spine in an unfavorable condition. Previous experimental studies have shown that disc prolapse is more likely to occur in normal or slightly degenerated discs, and that for prolapse to occur, the applied load must be a combination of forces (e.g., forward bending and axial compression) (Adams et al. 1982, 1985; Gordon et al. 1991). By definition, for a disc to prolapse it must have a fissure or channel for the passage of nuclear material (Brinckmann et al. 1994). Although this seems a statement of the obvious, it is still not clear how or where the fissure initiates and then propagates to create the channel. Therefore, the purpose of the study was to use a three dimensional viscoelastic finite element (FE) model of a lumbar motion segment to simulate the successive steps required to create a radial fissure in the anulus, and to study the effect of posture, fluid changes and loading rates on propagation of the fissure.
The Effect of Disc Degeneration on the Kinematic Characteristics of the Lumbar Motion Segment
Authors: Lim Tae-Hong , An Howard S. , Hong Jung Hwa , Yoshida Hyroyuki
Published: July 2023

Degenerative processes of the lumbar motion segment involve aging and degenerative changes of the intervertebral disc and facet joints. The classification most widely used for grading the disc degeneration was based upon the appearance of the disc in the horizontal section.4 Limitations of this grading scheme includes no assessment of changes in the end-plate and vertebral body, insufficient categories to distinguish wide range of appearances encountered, and the lack of tested validity of the scheme.7 Recently, Thompson et al.7 proposed a five-category grading scheme for assessing the gross morphology of midsagittal sections of the intervertebral disc.
Tissue Engineering: A Review
Authors: Ranieri John P.
Published: July 2023

Tissue engineering is defined as the in vitro or in vivo creation or regeneration of differentiated tissue for the clinical replacement of a compromised body structure. The ultimate goal of tissue engineering is to reconstruct an organ by taking advantage of recent progress in molecular biology (i.e., mechanisms controlling cell differentiation and gene transfer), materials science (development of “smart” and bioresorbable polymers), and surgical techniques. Tissue engineering is not so much a science in the traditional sense, but an amalgam of technologies from disparate fields that are grouped such that clinically relevant tissue replacement therapies may result.
Development, Manufacture and Clinical Testing of an Engineered Tissue: Experience With Human Skin
Authors: Parenteau Nancy L.
Published: July 2023

Development of a cell therapy beyond proof of principle requires overcoming practical as well scientific hurdles. Our experimental and clinical experience has been obtained developing a full-thickness human skin replacement (Graftskin™). Feasible cell sourcing, a scalable culture process, and mode of cell delivery are important to success both in the clinic and the marketplace. The ability to create working cell banks of the needed cell population allows reproducible manufacture of a complex tissue. For example, specialized keratinocyte cultivation techniques enable the production of approximately 200,000, 44 cm2 units of Graftskin using cells cultivated from one 1.5 cm2 infant foreskin.
A Mathematical Model of the Circulation in the Presence of a Bidirectional Cavopulmonary Anastomosis: Hemodynamics and Oxygen Concentration
Authors: Pennati Giancarlo , Migliavacca Francesco , Dubini Gabriele , Fumero Roberto , de Leval Marc R.
Published: July 2023

A mathematical model of the circulation was developed to study the hemodynamics in the presence of the bidirectional cavopulmonary anastomosis (BCPA). Computer simulations were conducted to evaluate the influence of an additional source of blood flow (ABF) from the native pulmonary artery on the hemodynamics and the oxygen concentration in the upper part of the body.
Effects of Upstream Curvature on Stenotic Flows
Authors: Bergman Harris L. , Ku David N.
Published: July 2023

Physiologic flows are unsteady and complicated. Fluid mechanics investigations of these flows typically simplify the geometries by assuming smooth, rigid walls and, in some cases, axisymmetry. Stenotic geometries have been of interest because they cause non-typical flow anomalies such as head loss and turbulence. Most studies with stenotic geometries have used axisymmetric stenoses with straight inlets. Both experimental and numerical results thus show only one jet configuration: with the jet staying along the centerline. Another stable configuration is for the jet to stick to a wall. Note that, in vivo, there are no perfectly straight vessels. In fact, stenoses which present morbidity and mortality typically originate downstream of bifurcations. After bifurcating, the flow in each branch is characterized by skewing of the velocity profile and by secondary flows. It is therefore necessary to ask how different is the post stenotic flow field when upstream curvature is present.
Analysis of Fluid Mechanical Energy Losses in Aortic Valve Stenosis
Authors: Heinrich Russell S. , Fontaine Arnold A. , Grimes Randall Y. , Moore Kristin E. , Levine Robert A. , Yoganathan Ajit P.
Published: July 2023

Aortic valve stenosis occurs when the aortic valve does not open fully during systole, thus creating an obstruction to blood flow leaving the left ventricle. Maximum orifice pressure drop and valve orifice area are the primary clinical indicators of the severity of aortic stenosis. Pressure drop can be measured by catheter insertion or calculated with the modified Bernoulli equation from Doppler ultrasound velocity measurements. Unfortunately there are discrepancies between the two techniques that are often attributed to pressure recovery downstream of stenotic aortic valves [Levine et al, 1989]. The relationship between orifice pressure drop and left ventricular function is ambiguous. This has been emphasized in a recent paper by Vandervoort et al [1996], which states, “Although maximum, transvalvular, and net pressure gradients are all different gradients that physically exist, it is currently not known which of these gradients is most relevant to reflect the work load imposed on the heart”. Since it has been shown that left ventricular function has a significant effect on post-operative recovery [Ross, 1985], it is imperative that the severity of aortic valve stenosis be evaluated in terms of left ventricular work capacity. Therefore, the purpose of this study was to determine the relationship between left ventricular work and pressure drop measurements in aortic stenosis. The hypothesis that motivated this study was that the left ventricle performs work to overcome energy losses caused by aortic valve stenosis, and the pressure drop that most accurately represents this work should be used for clinical assessment of aortic stenosis.
Sensitivity of Endothelial Cell Response to the Onset Rate of Shear Stress
Authors: Blackman Brett R. , LaPlaca Michelle C. , Barbee Kenneth A. , Thibault Lawrence E.
Published: July 2023

Bovine pulmonary aortic endothelial cells (BPAEC) exposed to controlled levels of fluid shear stress in the absence of ATP exhibited transient intracellular free calcium (Ca2+i) responses that were sensitive to the onset rate of shear stress (ORSS). A coaxial parallel-disk device was used to control the application of a high (>900 dyn/cm s−1) or low (< 6 dyn/cm s−1) ORSS. The high rate elicited greater peak responses and final levels of intracellular free calcium concentrations, [Ca2+]i, compared to the low rate. The ORSS appears to be an important parameter characterizing the mechanical environment of endothelial cells and may play a role in their differential responses in disturbed versus undisturbed flow regions.
Model Studies on the Origination of Pseudo-Regurgitation During Heart Valve Closure
Authors: Talukder Niranjan K. , Komerath Narayanan M.
Published: July 2023

The role of back flow or regurgitation in heart valve closure has been a matter of controversy for a long time. According to Bellhouse and Bellhouse (1969) a little back flow is necessary to close a heart valve and vortices play a crucial role in minimizing the back flow through heart valves. Talukder et al. (1977) advanced the hypothesis that under pulsatile flow valve closure may take place without the least regurgitation. Reul et al. (1981) demonstrated that, the flow pulsatility being maintained, valve movements remain practically unchanged in absence of vortices near the valve. They pointed out the important roles of the adverse pressure gradient during flow deceleration. Recent studies by Talukder and Komerath (1995) using flow visualization and Spatial Correlation Velocimetry (SCV) showed that, after the onset of flow deceleration, the valve leaflets are accelerated towards closure while the flow in the valve aperture is still forward. The present paper provides evidence for the fact that forward flow through the valve aperture persists even when the net flow across the valve root is reversed and attempts to explain the origination of this reversed flow.
Effect of Shear Stress on Albumin Uptake Into Cultured Endothelial Cells
Authors: Kudo Susumu , Ikezawa Kenji , Matsumura Shinji , Ikeda Mariko , Oka Kotaro , Tanishita Kazuo
Published: July 2023

The endothelial cell monolayer exposed to shear stress by a blood flow in vivo is a principal barrier for macromolecules transport across the vascular wall. Abnormal uptake of macromolecules into endothelial cell monolayer causes several vascular diseases. Therefore we studied the effect of shear stress on macromolecules uptake into cultured endothelial cells. After 48hr. exposure to shear stress, endothelial cells on coverslips were incubated at 37°C for 60 minutes in PBS containing Tetrametylrhodamine Isothiocyanate conjugated Albumin (TRITC-Albumin). Thereafter the uptake of albumin and the shape of endothelial cells were observed by a laser scanning confocal microscope. The uptake of albumin into endothelial cells exposed to shear stress increased for lower shear stress range and decreased for high shear stress.
Determination of Stresses and Strains in Heterogeneous, Diseased Human Aorta
Authors: Beattie Deborah K. , Vito Raymond P. , Xu Chengpei , Glagov Seymour
Published: July 2023

Atherosclerosis continues to be a leading cause of death and disability in this and other western industrialized nations. Although little is known regarding the relationships between stresses and strains in the arterial wall and disease etiology, one of the most clinically relevant issues is the stability of the established plaque. In this research, an experimental technique was developed to determine the finite strain field in heterogeneous, diseased arterial cross-sections in vitro. The distribution of histologic attributes such as lipid accumulations, regions of calcification, and the plaque fibrous cap is quantified. By coupling experimental and histologic data in a finite element analysis, plaque mechanical properties, stresses, and strain energies can be determined using an optimization approach. Such results form a basis for establishing links between the composition of diseased vessels and plaque failure in vivo.
Hemodynamics of the Total Cavopulmonary Connection: An In-Vitro Study
Authors: Kim Sang Hyun , Park Young Hwan , Cho Bum Ku , Hong Yoo Sun
Published: July 2023

Total cavopulmonary (CP) connection has been developed to treat hearts with essentially a single ventricular chamber[1]. In a typical CP connection, the superiour vena cava (SVC) and inferior vena cava (IVC) are connected directly to the right pulmonary artery (RPA). High incidence of failures occurred due to fibromuscular ingrowth, valvular degeneration and pseudo-intimal peel formation. All of which depend upon the hemodynamics of the connection through the presence of stasis, wall shear stress or energy loss due to the conduits. There is very little in-vitro study on the hemodynamics of the CP connection[2,3]. In terms of the local fluid dynamics, the surgically created circuit should not cause blood flow abnomalities. It is important to obtain quantitative informations to optimise the hemodynamic design of the CP connection. The objective of this study is to compare the flow fields across the models of the CP connection.
Effects of Ventricular Overloading on Multiaxial Mechanics in Passive Myocardium
Authors: Emery Jeff L. , Omens Jeffrey H. , McCulloch Andrew D.
Published: July 2023

Passive overstretch of myocardium occurs in the ischemic and dilated heart, but the subsequent changes in local tissue mechanics and structure remain unclear. Therefore, we estimated changes in myocardial biaxial stiffness using by solving an inverse finite element problem. The differences between the strains measured on the epicardium of the isolated rat left ventricle (LV) during overstretch and those of a prolate-spheroidal finite element model were minimized by optimizing the material parameters of an exponential constitutive law. When passive LV pressure was increased from 10 to 120 mmHg, there were progressive decreases in wall stiffness up to 93% that were equal in fiber and cross-fiber directions. Thus, myocardium softens isotropically with progressive overstretch independently of muscle fiber direction. This local strain softening may, therefore, arise from damage to structures with uniform distribution of orientation rather than components aligned with myofibrils.
An Optical System to Determine Axial Surface Strains in Skeletal Muscle
Authors: Best Thomas M. , McElhaney James E. , Garrett William E. , Myers Barry S.
Published: July 2023

Muscle is compliant, undergoes large deformations and demonstrate anisotropic behavior when loaded. The variable amount of specimen slippage can result in error when strain estimates are determined by measures of grip-to-grip motion (Zernicke et al., 1984). In this paper we describe a noncontact optical system and method of analysis to measure full field surface strains in skeletal muscle. The system is used to examine the effect of stretch rate on the distribution of axial strains in rabbit skeletal muscle.
Effects of Aging on Compressive and Laser Scatter Properties of Articular Cartilage
Authors: Athanasiou Kyriacos , Kovach Ian
Published: July 2023

The effects of maturation and aging on the functional characteristics of articular cartilage have not been fully studied. Known age- or maturation-related changes in this tissue’s biochemical constituents include accumulation of hyaluronic acid, chondrocyte modification, proteoglycan alterations, decreased water content, decreased proteoglycan extractability, greater degree of collagen crosslinking, and shortening of the core protein region. Numerous approaches can be employed to quantify age-related changes on the functional properties of articular cartilage. In this study, we chose to measure some of the tissue’s mechanical and optical properties in an aging baboon model. We obtained intrinsic, compressive, mechanical properties and correlated those to small angle laser light scatter characteristics. To our knowledge, this is the first time that the effects of maturation and aging have been measured on the compressive and light scattering properties of articular cartilage.
Tissue Engineering Striated Muscle Organs by Mechanical Forces
Authors: Vandenburgh Herman H.
Published: July 2023

Mechanical forces play a significant role during the organogenesis of striated muscle. The rapid bone elongation in the limb and the marked increases in blood pressure and volume during development help to organize skeletal myofibers and cardiomyocytes, respectively, into the proper three-dimensional cellular pattern necessary for a functional organ. The mechanotransduction processes regulating organogenesis can be studied in tissue culture by growing isolated embryonic cells on an elastic substratum and repetitively loading the substratum with computer controlled stepper motors. Both avian skeletal muscle and rodent cardiac muscle cells have been mechanically loaded while undergoing differentiation in vitro by patterns of activity that simulate the in vivo environment. In the presence of appropriate exogenous growth factors and extracellular matrix molecules, mechanical stimulation leads to the growth and organization of these cells into 2- and 3-dimensional organ-like structures (“organoids”) (Vandenburgh and Karlisch, 1989; Vandenburgh et al., 1991; Vandenburgh et al., 1995b). These organoids display many morphological characteristics of in vivo organs including skeletal myofibers organized into fascicles with developing tendon-like structures (Fig. 1), and sheets of parallel, interconnected rod-shaped cardiomyocytes. The pattern of unidirectional and repetitive mechanical stimulation is critical for the proper in vivo-like arrangement of the cells. For example, unidirectional stretching without relaxation of both skeletal and cardiac muscle cells aligns them in the direction of stretch, while repetitive stretch-relaxation of the same cells causes them to align perpendicular to the direction of stretch. Percent cell stretch and frequency of stretch are also important parameters in determining the growth response of the cells to mechanical forces.
Comparison of Optimal Seat Suspension Parameters Obtained Using Different Vibration Sensitivity Standards
Authors: Wan Yi , Schimmels Joseph M.
Published: July 2023

This paper investigates the effects that different vibration sensitivity standards have on optimal seat suspension designs. Optimal seat suspensions are obtained using a previously published 4 degree of freedom (DOF) model of a human exposed to vertical vibration [4] and five different previously published model-based human sensitivity standards to assess human sensitivity to imposed vibration [5]. Seat suspension optimal parameters obtained using the different vibration sensitivity standards are compared. The optimal parameter values are also compared with the results of previous optimal suspension design studies.
Fall Direction and the Likelihood of Fracture of the Proximal Femur
Authors: Sabick Michelle B. , Goel Vijay K.
Published: July 2023

Falls are a common cause of hip fractures in the elderly. Epidemiologic research suggests that the fall direction, and therefore the position of the femur at impact, affects the likelihood that a hip fracture will occur. The purpose of this research was to apply several loads which simulated likely fall directions to a finite element model of the proximal femur. Eight loads of 6000 N magnitude but varying in direction were applied. The magnitude of the resulting peak von Mises equivalent strains for each load case were calculated and compared to determine which fall directions were more likely to cause hip fracture. Falls with a 15° angle of femur inclination produced the highest strains regardless of the internal rotation angle of the femur. All simulated fall positions caused strains well above the three percent failure criterion, suggesting fractures would have occurred.
A Numerical Study of Flow Through a Mechanical Heart Valve
Authors: Wang Jong H. , Guo George , Schreck Stefan , Prisco Michael
Published: July 2023

The purpose of this study was to develop a numerical model for simulating the flow through a Mechanical Heart Valve (MHV), for which a good understanding of the detailed flow information is desired. This is because that fluid mechanics may play an important role in the thrombus formation and hemolysis in the mechanical valve prosthesis.
Experimental-Numerical Analysis of Mitral Mechanical Heart Valve Fluid Dynamics and Cavitation Potential
Authors: Siegel John M. , Makhijani Vinod B. , Singhal Ashok K.
Published: July 2023

Fluid dynamics are of primary importance in the function of mechanical heart valves (MHV’s). Excessive shear rates can cause damage to blood components, regions of stasis can result in blood clots, and extremely high or extremely low pressures can result in structural or cavitation damage, respectively. Experimental techniques can measure pressure and velocity in the region of heart valves, but are unable to resolve the fluid dynamics immediately adjacent to the micron sized ‘squeeze-flow’ gap between the valve leaflet and housing. The current study uses computational fluid dynamics (CFD) to provide a detailed description of the flow field surrounding mitral mechanical heart valves. Experimentally measured leaflet closing velocities are used as an input to the computational model which allows for moving boundaries. The resultant flow field is used to assess the time-history of important fluid parameters such as minimum pressure and maximum shear rate through the final degrees of valve closure.
Time Dependent Characteristics of Valvular Regurgitation: A Numerical Investigation
Authors: Myers Jerry G. , Anayiotos Andreas S. , Perry Gilbert J.
Published: July 2023

The steady normalized centerline-velocity distribution proximal to an orifice has been used in quantifying valvular regurgitation with color Doppler (CD). However, the presence of pulsitility and constraining walls in a viscous flowfield may influence the centerline flow characteristics. This study utilized computational fluid dynamic (CFD) models of the flow region proximal to an axisymmetric orifice to investigate the combined effects of adjacent wall influence and time dependence on the proximal flowfield. Steady state conditions and time waveforms for flowrate and pressure-gradient were used as input boundary conditions. Results of this study indicate that normalized centerline velocity distributions depend on adjacent wall orientation. However, for a specific wall orientation, the instantaneous, normalized, centerline-velocity distribution showed little deviation from steady state distributions. These results suggest that the steady state proximal centerline velocity distribution is a good approximation the pulsatile centerline distribution for a specific time.
Flow Effects on the Concentration of Platelet Active Substances in the Vicinity of Mural Platelet Aggregates
Authors: Perktold Karl , Karner Gerhard , Rappitsch Gerhard
Published: July 2023

The influence of convective flow on the transport of prothrombin, thrombin, antithrombin, ADP and thromboxane in the vicinity of a mural microthrombus has been analysed applying computer simulation. The basis of the study is a suitable reaction, emission and transport model. The reaction kinetics and the mass transport are modelled mathematically with a coupled system of convection-diffusion equations. The description of the flow field near the microthrombus uses the three-dimensional Navier-Stokes equations. The numerical approach applies the finite element method.
A Numerical Simulation for Determination of Velocity Encoded MR Parameters
Authors: Fox James F. , Anayiotos Andreas S. , Doyle Mark
Published: July 2023

Several current investigations aim at developing methods of measuring valvular regurgitation using velocity encoded magnetic resonance (MR) imaging. MR flow encoding provides useful three-dimensional spatial and velocity information. While still in the preliminary stages, these investigations must distinguish the optimum scan parameters necessary to minimize acquisition time and maximize quantitative results. Scan parameters of particular interest are slice thickness and slice orientation. This simulation uses velocity information from computational fluid dynamic (CFD) models to create a numerical, flow dependent, MR scan proximal to an orifice. The purpose of this simulation is to analyze the effect of slice thickness and slice orientation on measuring flow proximal to an orifice. Results indicate that centerline distribution for the four millimeter (mm) slices compare best to the numerical and 1 mm slices, considering that larger slice thicknesses reduce scan time. In addition, given the 4 mm slice thickness, perpendicular slices provide more useful velocity information within the region of interest.
The Effects of Anatomical Models and Cost Functions Used by Optimization Models on the Predicted Spinal Load
Authors: Parnianpour M. , Shirazi-Adl A. , Wang J. L. , Wilke H.-J. , Sparto P.
Published: July 2023

The kinetic redundancy present in the biomechanical models of complex joints has presented an obstacle in estimating the joint reaction forces during simulation of complex physical activities. Six anatomical models used for the spinal loading studies and six cost functions suggested by various groups were considered in determining their effects on the predicted joint reaction forces. Only the type of anatomical model that was used significantly affected the predicted spinal loads.
Reconstruction of Embryo 3D Surface Geometry Using Multiple Macroscope Images
Authors: Brodland G. Wayne , Veldhuis Jim H.
Published: July 2023

An algorithm for reconstructing the surface geometry of a developing embryo using macroscope images taken from at least two viewing angles is presented. A feature of the method is that it can correct for translational camera errors. To implement the method, point correspondences must be established between feature points that are visible in two or more views. If the embryo surface has sufficient optical texture, this can be done by computer using image processing techniques (Veldhuis and Brodland, 1996). A system of linear equations that determine the three-dimensional point locations and camera translations that minimize the total squared error are derived. These can be solved directly for each reconstruction case.
Multi-Body Contact Analysis of the Tibiofemoral Joint in Varus-Valgus
Authors: Bendjaballah M. Z. , Shirazi-Adl A. , Zukor D. J.
Published: July 2023

The passive stability of the human knee joint under various loads and motions is provided by the multi-body articulations, menisci, and ligaments. In this study we sought to investigate the articulation response of the joint under varus-valgus moments and determine the influence of sectioning collaterals on the joint biomechanics. For this purpose, a nonlinear 3-D finite element (FE) model of the human knee [1] is used in which, the multi-body articulation between cartilage layers as well as the intervening menisci are treated as a frictionless nonlinear contact problem. The mechanical response of the intact joint at full extension is investigated in varus-valgus moments of up to 15N-m followed by two analyses that simulate MCL and LCL-deficient human knees under valgus and varus moments, respectively. Attention is focused on the mechanism of contact and load transmission across the tibiofemoral articulation and the overall biomechanics of the joint including joint kinematics, ligament forces, and stress/strain states in various components for the intact and collateral-deficient knee models.
A Telemetry System for In-Vivo Temperature Measurement in Orthopaedic Implants
Authors: Shetty Devdas , Kondo Jun , Fast Avital
Published: July 2023

The need for a miniaturized, telemetrized and light weight implantable device to monitor the human and animal bio-parameters has been increasing in recent years as more researchers try to understand the cause and effects of various diseases that lend themselves to human and animal disability. This paper highlights a methodology of monitoring the temperature variations over a period of time in large animals. This research has focussed on the design and development of a miniaturized sensing and transmission mechanism to acquire the temperature data. The system uses a real time visual simulation based data acquisition system which has advantages while monitoring the healing parameters in animals. The visual simulation system can also be used for the modeling of the sensing methodology in addition to the monitoring of the data. Simulated in vitro studies in the laboratory were conducted. The results from a canine knee joint implant indicate the presence of lower temperature under normal activities. The paper, which describes the scientific objectives of the design problems, highlights the test results.
Investigation Into a Miniaturized Sensing Device for Angular Measurement in Hip Implants
Authors: Soni M. K. , Shetty D. , Leone D. J. , Nowak M. D. , Lewis C. G.
Published: July 2023

This paper looks at a methodology of precision measurement of angular micro-motion in a hip prosthesis. This research involved investigating various types of angular sensing devises such as potentiometric sensors, capacitive sensors, inductance transducers, variable reluctance transducers, optical encoders and hall effect sensors. After considering their feasibility, a hall effect sensor was designed for a model of an implant and a femur. A brief description of the design procedure is given. The results of the experiment show that the usage of hall sensors for micro-motion measurement are promising.
Finite Element Mesh Generation Using Skeleton-Based Decomposition of Sliced Biomedical Image Data: Application to Limb Prosthetics
Authors: Zachariah Santosh G. , Sanders Joan E. , Turkiyyah George M.
Published: July 2023

A systematic method to generate hexahedral meshes for finite element (FE) analysis of residual limbs and similar biomedical geometries is presented. It utilizes skeleton-based subdivision of parallel cross-sections into geometrically simple regions onto which structured meshes are easily mapped. Tubular surfaces, defined using B-splines, were chosen to describe component geometries. Application to a below-knee (BK) residual limb is described. Automated hexahedral meshing of sliced data is an advancement in prosthetic stress analysis allowing rapid generation and iterative optimization of the mesh.
Wear of Acetabular Component in Total Hip Arthroplasty: A Parametric Mathematical Model
Authors: Pietrabissa Riccardo , Di Martino Elena , Brugnolotti Gloria , Chichi Marcella , Grappiolo Guido
Published: July 2023

This paper presents a parametric mathematical model to evaluate the dependence of acetabular component wear upon characteristic parameters of the patient and the total hip prosthesis.
On the Biaxial Mechanical Coupling Behavior of Chemically Treated Bovine Pericardium
Authors: Sacks Michael S.
Published: July 2023

Characterization of the non-linear biaxial mechanical properties of chemically treated bovine pericardium (BP) is necessary of proper bioprosthetic heart valve design. New chemical treatment technologies such as photo-oxidation (Moore, et al., 1994), whose aim is to reduce calcification, produce new biomaterials with unknown mechanical behaviors. Further, the state of tension during fixation can profoundly affect the mechanical properties chemically treated BP. In this work we performed biaxial mechanical testing on free-fixed glutaraldehyde treated BP and photo-oxidized tissue that was free-fixed and pre-stretched during fixation. BP biaxial mechanical behavior was modeled using an exponential strain energy function. This strain energy function allowed comparisons of the coupling responses using the globally derived material constants.
Acoustic Emission Detection of Microdamage in Cortical Bone
Authors: Kohn David H. , Rajachar Rupak M. , Thompson Thomas M. , Wcissman Neil A. , Curtis Christopher E.
Published: July 2023

It has been hypothesized that microdamage is a precursor to bone remodeling, regeneration, repair and osseointegration into implants. If damage occurs at a slow enough rate, bone remodeling serves to repair the damage. However, if damage accumulates faster than repair, the microdamage propagates, larger cracks are formed, and catastrophic fracture can occur. Structural damage in bone is associated with stress fractures, pathological fractures, and degenerative diseases. Many of these fractures are not detected until catastrophic fracture occurs, and are thought to be fatigue fractures. By detecting microdamage at an early stage, material failure mechanisms can be related to microstructural and mechanical parameters, yielding insight into potential mechanisms causing microdamage and governing failure.
The Mechanics of the Mechanosensory System in Bone
Authors: Cowin Stephen C.
Published: July 2023

A candidate for the mechanosensory mechanism by which living bone senses its applied mechanical loading and subsequently adapts its tissue structure to accommodate the loading is presented. The emphasis in the presentation will be on ideas and mechanisms — the underlying equations will be described but not presented. The work presented is to be that accomplished jointly with my colleague Shelly Weinbaum and our students, but it is dependent on the work of many others, particularly Sol Pollack and his students, and Clint Rubin, Ken MeLeod and their associates.
Variation of Young’s Modulus and Hardness in Human Lumbar Vertebrae Measured by Nanoindentation
Authors: Roy Marcel , Rho Jae-Young , Tsui Ting Y. , Pharr George M.
Published: July 2023

The nanoindentation technique was used to characterize the variation of the intrinsic mechanical properties of human lumbar vertebral cortical and trabecular bone. Significant differences in mechanical properties between various orientations were revealed. Longitudinal sections of vertically aligned trabeculae have a hardness and elastic modulus higher than other directions of cortical and trabecular bone.
Biomechanics-Based Pre-Operative Planning in THR: Application of Fictitious Domain Method
Authors: Kallivokas Loukas F. , Jaramaz Branislav , Ghattas Omar , Shah Sameer V. , DiGioia Anthony M.
Published: July 2023

Typical pre-operative planner in total hip replacement (THR) surgeries includes only geometric templating capabilities that are used, invariably, to find an appropriate match between the femoral and acetabular implants and their respective receiving bones. Such systems lack the predictive capabilities that could conceivably be offered by pre-operative planners enhanced with biomechanical evaluation modules. For the augmented pre-operative planners to be of clinical use, the underlying analysis tools need be reliable, fast and accurate. However, most analysis tools are designed and tested outside the context of a pre-operative planner and in an ad-hoc way that is difficult to automate, if one were to meet the severe demands of a patient-specific pre-operative planning environment. Furthermore, the typical modeling pipeline that is the backbone of the analysis part of a biomechanical evaluation module, is burdened by the introduction of approximation errors. We report here on a novel approach that greatly simplifies the typical modeling pipeline.
Computer and Robot Assisted Total Knee Arthroplasty
Authors: Fadda Marco , Marcacci Maurilio , La Palombara Francesco , Bertelli Daniele , Visani Andrea , Dario Paolo , Paggetti Cristiano
Published: July 2023

Total Knee Arthroplasty (T.K.A) is a complex intervention aimed at restoring a good level of patient’s activity by substituting damaged knee articular surfaces by a compound prosthesis. As a matter of fact, the intervention is not very repeatable, because of the large amount of variables influencing it and for this reason, long term positive results are achieved only in a limited number of patients which do not need to be reoperated during their life (Hungerford et al. 1993).
Computer Assisted Planning for Knee Surgery: A Patient Specific Approach
Authors: Heegaard Jean H. , Hovey Chad B. , Kaplan Matt L.
Published: July 2023

Current medical imaging technology provides orthopaedic surgeons with powerful tools to diagnose knee joint disorders. However, after having planned a corrective procedure, surgeons are confronted with the problem of transposing a pre-operative protocol based on medical images to the patient. Furthermore, this planning all to often bears an inherent qualitative character resulting from the current impossibility to fully appreciate the complexity of the joint’s biomechanics.
Computational Models for Cardiac Looping
Authors: Taber Larry A. , Perucchio Renato
Published: July 2023

Early in development, the initially straight heart tube bends (loops) into a curved tube. Two theoretical models are proposed for the mechanism of cardiac looping. In one model, a residual stress in the dorsal mesocardium drives looping, while in the other model, microfilament contraction drives the deformation. The results show that the models are consistent with most of the available experimental data, but further studies are necessary.
Measurement of Friction Properties at the Bone-Metal Interface for Various Porous Metal Surfaces
Authors: Dammak M. , Shirazi-Adl A. , Schwartz M. , Gustavson L.
Published: July 2023

In joint arthroplasty, adequate initial and long-term fixation of implant components to host bone represents a great challenge as a stable fixation is a prerequisite to its satisfactory performance. In a cementless implant, bone-prosthesis interface friction plays an important role in the transfer of shear stresses and, hence, in the fixation stability of the system, particularly in the immediate post-operative period when no bony ingrowth has yet occurred. The friction properties at the interface between tibial cancellous bone and a number of metal plates (ie, a beaded porous surface, a fibre mesh porous surface, and a smooth surface) have previously been measured under single and repetitive loadings [1,2]. In this investigation, friction properties of four different metal surfaces on polyurethane and cancellous bone specimens are measured and compared. Three different normal stresses of 0.1, 0.15, and 0.25 MPa are used. Bone cubes are obtained from different proximal regions of resurfaced cadaveric tibiae. Both monotonic and cyclic fatigue loadings of up to 4000 cycles at one Hz are considered.
Efficient Finite Element Method for Contact Analysis of Articular Joints
Authors: Stone James J.-S. , Ju Shen-Haw , Chao Edmund Y. S. , Morrey Bernard F. , An Kai-Nan
Published: July 2023

An efficient 2-D continuum finite element method (FEM), including the rigid body algorithm and our previously developed contact element, was formulated for the contact stress analysis of articular joints. This FEM can calculate the contact pressure distribution on articular surfaces and stress distribution inside of cartilage. This method can model geometric and material nonlinearities for both the static and dynamic situations. The major advantage of this method is that only the soft cartilage requires finite element (FE) mesh, while the bony structure can be modeled as a rigid body due to its relatively rigid nature. Since much less degrees of freedom are now required in FEM, much faster computing speed can be achieved.
Efficient Parametrization of the Configuration Space for Rigid Multi-Body Contact and Impact
Authors: Heegaard Jean H.
Published: July 2023

Contact and impact problems are routinely encountered in joint biomechanics and computer generated gait analyses. Reduction of the system’s configuration space dimensions by inequality constraints is one of the main difficulty when solving such problems. Much effort has been devoted, especially by the finite element community, to the formulation of contact constraints which are easy to compute (Laursen and Simo, 1993; Heegaard, 1995; Wriggers and Imhof, 1993).
An Interactive Model of the Human Thigh for Simulating Surgical Procedures in Virtual Environments
Authors: Basdogan Cagatay , Loan Peter , Rosen Joseph M. , Delp Scott L.
Published: July 2023

We have developed an interactive 3D model of the human thigh along with a set of surgical tools to simulate surgical procedures in virtual environments. The project will have applications in the training of medical personnel to treat traumatic injuries. Our current simulation system uses a graphics workstation, stereo glasses, and a 6-degree-of-freedom positioning device. Future versions of the system will provide a more realistic training environment by employing force-feedback devices.
Influence of Q Angle on Patellofemoral Tracking During a Simulated Walking Cycle
Authors: Pavlovic Jennifer L. , Bourgeault Craig A. , Bechtold Joan E. , Gustilo Ramon B. , Durfee William K. , Kirstukas Steven J.
Published: July 2023

The angle between the line of application of the quadriceps force and the direction of the patellar ligament is commonly called the Q angle. A large Q angle, with an excessive lateral pull by the quadriceps muscles on the patella, may cause pain and lateral patellar dislocation. Three-dimensional (3D) patellofemoral (p-f) tracking, as a function of a 5° increase (+) and decrease (−) in Q angle, was measured in vitro during a dynamic walking cycle on a knee simulation machine to determine the effects of change in Q angle on patellar shift (medial-lateral translation), rotation (in the frontal plane) and tilt (in the transverse plane) during walking. One objective of this study was to assess whether these effects could be emulated with an acceptable degree of realism on our knee simulation machine. Full details about this study can be found in [Pavlovic, 1996].