Showing papers in "Journal of Biomechanical Engineering-transactions of The Asme in 1983"

A Joint Coordinate System for the Clinical Description of Three-Dimensional Motions: Application to the Knee

Abstract: The experimental study of joint kinematics in three dimensions requires the description and measurement of six motion components. An important aspect of any method of description is the ease with which it is communicated to those who use the data. This paper presents a joint coordinate system that provides a simple geometric description of the three-dimensional rotational and translational motion between two rigid bodies. The coordinate system is applied to the knee and related to the commonly used clinical terms for knee joint motion. A convenient characteristic of the coordinate system shared by spatial linkages is that large joint displacements are independent of the order in which the component translations and rotations occur.

In-Vitro of Measurement of Static Pressure Distribution in Synovial Joints—Part I: Tibial Surface of the Knee

Abstract: In this first part of a two-part paper, the results of measurement of static pressure distribution on the tibial surface of the knee are presented. Results with intact menisci have been obtained from 18 specimens. Eight of these specimens were the subject of further measurements following medial meniscectomy. The study has been carried out at various flexion angles of the knee with the joint subjected to a compressive force, with or without an initial passive relative displacement between the joint members. The results indicate that a significant fraction of the joint compressive load is transmitted through the menisci and that total meniscectomy causes a drastic alteration in the pressure distribution on the tibial surface. Clinical implications of these results, in terms of post-meniscectomy degenerative changes and mechanism of meniscal lesions, have been discussed.

Three-dimensional stress distribution in arteries.

Abstract: A three-dimensional stress-strain relationship derived from a strain energy function of the exponential form is proposed for the arterial wall. The material constants are identified from experimental data on rabbit arteries subjected to inflation and longitudinal stretch in the physiological range. The objectives are: 1) to show that such a procedure is feasible and practical, and 2) to call attention to the very large variations in stresses and strains across the vessel wall under the assumptions that the tissue is incompressible and stress-free when all external load is removed.

In-vitro measurement of static pressure distribution in synovial joints--Part II: Retropatellar surface.

Abstract: This second part of a two-part paper is concerned with the measurement of static pressure distribution on the retropatellar surface. The study has been performed in a loading apparatus designed to simulate individually the lines of action and the magnitudes of the tensions in the components of the quadriceps femoris muscle group. Results have been obtained using 24 specimens in the knee flexion range 0 to 130 deg and employing a net quadriceps tension of 734 N. Particular emphasis has been placed on the evaluation of the sensitivity of the results to variations in the characteristics of the simulated quadriceps tension. The pressure distribution results have been interpreted in terms of variation of the normal force and the average contact stress on the retropatellar surface as a function of flexion angle. It has been shown that the "pulley" model of the patella consistently overestimates the actual patellofemoral joint reaction force throughout the range of flexion. Clinical implications of the results, in terms of etiology of degeneration of patellar cartilage, have been discussed.

Cycle-dependent and time-dependent bone fracture with repeated loading

Abstract: Fatigue tests of human cortical bone (up to 1.74 X 10(6) cycles) were conducted under tension-compression (T-C) and zero-tension (O-T) modes with a 2Hz, stress controlled, sinusoidal loading history. Tensile creep-fracture tests at constant stress levels were also performed. The relationship between the initial cyclic strain range and cycles to failure with the T-C specimens were consistent with that derived previously in low-cycle fatigue under strain control. Using a time-dependent failure model, the creep-fracture data was found to be consistent with previous studies of the influence of strain rate on the monotonic tensile strength of bone. The model also predicted quite well the time to failure for the O-T fatigue specimens, suggesting that creep damage plays an important role in O-T fatigue specimens.

Age-dependent influence of strain rate on the tensile failure of rat-tail tendon.

Abstract: Sensitivity of tensile strength, failure strain, and failure energy density to strain rate was studied for rat-tail tendon (RTT), a collagen-rich connective tissue. Tendons from animals aged 1-27 months were stretched at a high (720 percent/s) and low (3.6 percent/s) strain rate. Each failure parameter increased with strain rate. However, the sensitivity of tendon failure to rate of strain decreased rapidly during growth and sexual maturation of the animal. The study provides basic data on the rate-sensitive strength of collagen fibers using RTT.

Leg Motion Analysis During Gait by Multiaxial Accelerometry: Theoretical Foundations and Preliminary Validations

Abstract: A theoretical formulation for studying limb motions and joint kinetics by multiaxial accelerometry is developed. The technique is designed to study the swing phase of human gait, modeling the lower leg as a rigid body. Major advantages of the approach are that acceleration information needed for the calculation of forces and moments is generated directly, and that the method automatically generates its own initial conditions. Results of validation experiments using both artificial and experimental data demonstrate that the method is theoretically valid, but that it taxes available instrumentation and requires further development before it can be applied in a clinical setting.

A Finite Element Model of Burn Injury in Blood-Perfused Skin

Abstract: The burn process resulting from the application of a hot, cylindrical source to the skin surface was modeled using the finite element technique. A rotationally symmetric 125-element mesh was defined within the tissue beneath and outlying to an applied heating disk. The disk temperature and duration of contact were varied, respectively, between 50 and 100 degrees C for up to 30 s. Natural convection with ambient air was assumed for areas of skin surface not in direct contact with the disk. The simulated thermal history was used in a damage integral model to calculate the extent and severity of injury in the radial and axial dimensions.

A Three-Dimensional Model of the Human Cervical Spine for Impact Simulation

Abstract: A three-dimensional analytical model of the cervical spine is described. The cervical vertebrae and the head are modeled as rigid bodies which are interconnected by deformable elements representing the intervertebral disks, facet joints, ligaments and muscles. A special pentahedral continuum element for representing the articular facets is described which effectively maintains stability of the cervical spine in both lateral and frontal plane accelerations, which is very difficult with multi-spring models of the facets. A simplified representation is used for the spine and body below the level of T1. The neck musculature is modeled by over 100 muscle elements representing 22 major muscle groups in the neck. The model has been validated for frontal and sideways impact accelerations by simulating published experimental data. Results are also presented to show the effects of the stretch reflex response on the dynamics of the head and neck under moderate acceleration.

Error analysis of a system for measuring three-dimensional joint motion.

Abstract: In the past ten years there has been increased use of six-degree-of -freedom in­ strumented spatial linkages for the measurement of biological joint motions. In spite of the increased popularity, little information has been reported on the ac­ curacy of these devices. In this paper, we present a two-part investigation of the accuracy of the instrumented spatial linkage when used to measure knee joint kinematics. In the first part, we present the results of a theoretical analysis and an experimental determination of the errors associated with spatial linkage systems. In the second part, we describe the errors associated with a bi-planar X-ray system used to obtain the coordinate transformation between the linkage ends and coor­ dinate systems located in the bones comprising the joint. We found that the theoretical error analysis consistently overestimated the actual measurement error, thus providing an unreliable estimate of errors. The experimental study of both the linkage system and the bi-planar X-ray system demonstrated that the accuracy of displacement measurement is insensitive to large systematic errors in position measurement.

A Concise Sensitivity Analysis of the Quasi-Linear Viscoelastic Model Proposed by Fung

Abstract: • A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers.

Identification of in-vivo vibration modes of human tibiae by modal analysis.

Abstract: When attempting to evaluate the mechanical properties of human bones in vivo by mechanical vibration analysis, some essential requirements must be met. A quantitative relation between measured vibration parameters (e.g., natural frequency) and mechanical bone properties must be available, in-vivo vibration modes should correctly be identified and the associated natural frequencies reproducibly and accurately measured, the influence of joints and soft tissues must be known. These problems were addressed by modal analysis (i.e., experimental determination of natural frequencies, mode shapes and damping ratios) of human tibiae in the following situations: 1) dry excised tibiae, 2) fresh excised tibiae, 3) in-vivo tibiae, 4) tibiae in an amputated leg, in different steps of dissection. In the in-vivo measuring conditions used by the authors, the tibia vibration is practically free-free. Two single bending modes (at +/- 270 Hz and +/- 340 Hz, respectively), each of them corresponding with one principal direction for bending, were identified. The difference between the natural frequencies observed in vivo and those of fresh excised tibiae is almost completely caused by the effect of muscles (added mass and damping), whereas joints and skin play only a minor role. Frequency differences between fresh and dry excised tibiae are largely accounted for by the absence of bone marrow in the latter.

Monitoring fracture site properties with external fixation.

Abstract: An in-vitro system has been devised to monitor the properties of an idealized fracture site immobilized with a Hoffman-Vidal external fixator. A dial gage was used to measure the relative pin displacements under controlled axial loading. The displacement measurements were then used in conjunction with a finite element model to predict the modulus of an idealized fracture site. Five fracture sites made of neoprene disks of different mechanical properties were monitored in order to simulate the increasing modulus of a healing fracture. Good agreement was observed between directly measured mechanical properties of the neoprene and those inferred from the combined finite element and pin displacement tests.

Measurement of turbulence intensity in the center of the canine ascending aorta with a hot-film anemometer

Abstract: The blood flow velocity near the central axis of the canine ascending aorta was measured with a hot-film anemometer. The cardiac output and the heart rate were controlled at will by means of an extracorporeal circulation and by atrial pacing. The turbulent component of the blood flow velocity was calculated using an ensemble average technique. Ensemble average turbulent intensity was also calculated to show the time course of turbulence in the aorta. The ratio of the mean turbulence intensity to the time mean sectional average velocity in the aorta was constant in most animals regardless of the changes in fluid mechanical parameters. The correlation between the frequency parameter and the relative mean turbulence intensity was weakly positive. The power spectrum of the turbulence was also calculated.

Joint models, degrees of freedom, and anatomical motion measurement.

Abstract: When the motion associated with an anatomical joint is to be measured, a kinematic model for the joint must first be established. The joint model will have from one to six degrees of freedom, and both the measurement technique and the means used to describe the motion will be influenced by the model and its degrees of freedom. This paper discusses the modeling and measurement of anatomical joint motion from a kinematics viewpoint. A review of the literature pertaining to measurement techniques, kinematic assumptions, and motion descriptions for anatomical joint motion is presented. One, two, three and six degree-of-freedom models for various anatomical joints have appeared in the literature, and the applicability of these models is compared and discussed.

Pre-collapse stress redistributions in femoral head osteonecrosis--a three-dimensional finite element analysis.

Abstract: Three-dimensional finite element analysis is used to explore the influence of several lesion characteristics upon mechanical stress distributions in segmentally necrotic human femoral heads. Variables studied parametrically included apparent modulus deficits within the lesion proper, as well as the depth, width, and location of the infarcted head regions. The detailed patterns of stress redistribution were complex and were found to be a strong function of the specific lesion characteristics. The salient phenomenon, however, was one of preferential load uptake by the stiffer bone surrounding the lesion. Since computed stress reductions within the infarctions were usually much smaller than experimentally observed strength reductions, the data suggest a strong tendency for an elevated incidence of trabecular fatigue fractures in the affected regions.

A Pressure Distribution Transducer for In-Vitro Static Measurements in Synovial Joints

Abstract: The basic features and the performance characteristics of a transducer to measure in-vitro static pressure distribution at the articular interfaces of intact synovial joints are described Pressure distribution is interpreted from the micro-indentation pattern left on a thin plastic material, the indenter and the plastic material having been subjected to load between the articular surfaces The effects of the finite thickness and compliance of the transducer and the effects of the time-dependent response properties of the articular cartilage on the accuracy of measurement have been estimated by means of specific experiments and analyses

Constitutive Equations for the Lung Tissue

Abstract: The mechanical behavior of the lung tissue (expressed by its constitutive equations) has considerable influence on the normal and pathological function of the lung It determines the stress field in the tissue, thus affecting the impedence and energy consumption during breathing as well as the localization of certain lung diseases The lung tissue has a complex mechanical response It arises from the tissue's structure--a cluster of a very large number of closely packed airsacks (alveoli) and air ducts Each of the alveoli has a shape of irregular polyhedron It is bounded by the alveolar wall membrane In the present study, a stochastic approach to the tissue's structure will be employed The density distribution function of the membrane's orientation in space is considered as the predominant structural parameter Based on this model the present theory relates the behavior of both the alveolar membrane and that of its liquid interface to the tissue's general constitutive properties The resulting equations allow for anisotropic and visco-elastic effects A protocol for material characterization along the present model is proposed as well The methodology of the present theory is quite general and can be similarly used with other structural models of the lung tissue (eg, models in which the effect of the alveolar ducts is included)

Static analysis of the left ventricle.

Abstract: Static analysis of the left ventricle is developed to estimate the local stresses and deformations that occur during the heart cycle. The left ventricle is represented as a thick hollow tube composed of solid fibers embedded in an inviscid fluid matrix. A finite deformation analysis is developed to estimate the variation of the pressure, fiber tension and fiber extension across the thickness of the left ventricle. Pressure-volume relations are obtained for the diastolic and the systolic peak isovolumetric phases. The fiber stress distribution and pressure variation are estimated as a function of the initial fiber orientation distribution, relative thickness of the ventricle, inner volume of the ventricle and the various tension-extension relations proposed for the fibers of the heart muscle. It is concluded that the diastolic pressure-volume relation is not very sensitive to either the fiber orientation distribution or the thickness of the ventricle. However, the pumping efficiency of the modeled ventricle is shown to increase with increasing thickness of the modeled left ventricle and with increasing contractility of the heart muscle fibers.

Tensile fatigue failure of acrylic bone cement.

Abstract: Tensile fatigue tests of acrylic bone cement were conducted under strain control in a wet environment at 37 degrees C. A constant strain rate of 0.02s-1 was used, resulting in physiologic loading frequencies. Comparison of the tensile fatigue data with the results of previous tension-compression fatigue tests indicates that fatigue failure is governed primarily by the maximum cyclic tensile strain. The compressive portion of the loading cycle has little effect on the number of cycles to failure. A new empirically derived equation is introduced to describe the influence of mean strain and strain amplitude on fatigue endurance. The results emphasize the critical role tensile strains may play in cement failure and loosening of total joint replacements.

Analysis of the Water Permeability of Human Granulocytes at Subzero Temperatures in the Presence of Extracellular Ice

Abstract: The plasma membrane water permeability of human granulocytes in the presence of extracellular ice was determined experimentally on a cryomicroscope Transient volumes of individual cells were measured at constant subzero temperatures subsequent to ice nucleation Permeability values were deduced by adjustment of multiple parameters in a model to obtain an optimal fit to the data The permeability was determined to be a function of both temperature and intracellular solute osmolality, with a reference value at 0 degrees C of 0407 micrometers/atmmin and temperature and solute coefficients of 218kJ/mol and 109 Osm/kg

An analytical technique for modeling knee joint stiffness--Part II: Ligamentous geometric nonlinearities.

Abstract: An analytical technique previously developed to evaluate the contribution of the ligaments to the nonlinear, coupled stiffness characteristics of the human knee joint [1] is extended here to include geometric nonlinearities. In [1], we assumed that the ligaments act as tensile bands running in a straight line between tibial and femoral insertion sites. Here, two forms of geometric nonlinearities are introduced and analyzed: ligaments wrapping around bone surfaces, such as occurs with the medial collateral ligament, the posterior capsule, and the anterior cruciate in hyperextension, and wrapping of ligaments around each other, such as occurs with the cruciate ligaments as the knee is flexed and internally rotated.

Mechanical behavior of fetal dura mater under large axisymmetric inflation.

Abstract: The nonlinear mechanical behavior of fetal dura mater was tested experimentally and compared to two published nonlinear material strain energy functions, the Mooney-Rivlin and the Skalak, Tozeren, Zarda, and Chien (STZC). The STZC constitutive relations best fit the behavior of the dura mater and were used to describe quantitatively its stiffness. Runge-Kutta numerical procedures were used to fit the theoretical data to the experimental results. The material's stiffness was positively correlated with fetal weight (r = 0.67, p less than 0.05). These results are discussed and directions for future research indicated.

In-Vitro Fluid Dynamic Characteristics of the Abiomed Trileaflet Heart Valve Prosthesis

Abstract: The need for better and longer lasting trileaflet valves has led to the design and development of the Abiomed polymeric trileaflet valve prosthesis. In-vitro fluid dynamic studies on sizes 25 and 21 mm valves in the aortic position indicate an overall improvement in performance compared to the Carpentier-Edwards and Ionescu-Shiley tissue valves in current clinical use. The pressure drop studies yielded effective orifice areas of 1.99 and 1.54 cm2, and performance indices of 0.41 and 0.45 for the Nos. 25 and 21 valves, respectively. Leaflet photography studies indicated that the two valve sizes had maximum opening areas of 225 and 145 mm2, respectively, at a normal resting cardiac output. Steady and pulsatile flow velocity measurements with a laser-Doppler anemometer (LDA) system indicate that the flow field downstream of the Abiomed valve is jetlike and turbulent. Maximum mean square axial velocity fluctuations of 55 and 83 cm/s, and turbulent shear stresses of 220 and 450 N/m2 were measured in the immediate vicinity of the nos. 25 and 21 valves, respectively. The Abiomed valves studied had been originally configured for use in valved conduits, and it is therefore our opinion that further improvements can be made to the valve and stent design, which would enhance its fluid dynamic performance.

Model Simulation of Heat and Water Transport Dynamics in an Airway

Abstract: Heat and water transport processes in the respiratory tract depend on environmental conditions, breathing patterns, and the physiological state of the respiratory system. To study these processes, we have developed a mathematical model of the dynamics of temperature and water vapor in the radial and axial directions of an idealized trachea. The model is expressed as two implicit finite-difference equations and solved using an alternating-direction algorithm. Using these equations, we simulated the effects of inspired gas temperature and humidity, velocity profile, and flow rate on heat and water transport between the gas and airway wall. Under inspired gas conditions of low temperature or high relative humidity, supersaturation occurs. Increasing either the velocity gradient at the wall or the flow rate increases the heat and water transport rates. However, these rates change by only 10 percent when the velocity gradient is doubled, and by about 35 percent when flow rate undergoes a two-fold change. The model can be used with in-vivo data from the trachea to test hypotheses concerning normal and abnormal heat and water transport.

Soft Tissue Strain and Facet Face Interaction in the Lumbar Intervertebral Joint—Part II: Calculated Results and Comparison With Experimental Data

Abstract: A numerical simulation of soft-tissue strain and facet face interaction in the lumbar intervertebral joint under load was performed. The results, compared with a previous experimental sectioning study, showed that disk fiber strain was the main mechanism in shear resistance, except posterior shear, where the facets were main load bearing members. In axial compression, compression of the annulus was found, with a significant decrease in compressive strain resulting from annulus bulging, but no contact was found in the facet joints. The posterior ligaments, except for the facet capsules and ligamentum flavum, were found to be active only in flexion and lateral bending, while the facets and the disk both played major roles in resisting axial torsion moments.

Mechanical Characterization of Membranelike Biological Tissue

Abstract: Experimental and analytical methods are presented which enable one to examine the local rheological properties of biological tissues which can be captured as flat sheets between matching pressure manifolds and deformed under experimentally prescribed hydrostatic loading conditions In spite of the fact that most biological tissues, including arteries, are nonlinearly elastic when considered over wide ranges of strain, it was found that the deformation of swine and canine arterial wall specimens in the physiological range of wall strain can be approximated by an isotropic, linearily elastic membrane model In view of this, the elastic behavior was characterized approximately by an incremental modulus over the range of 045 to 065 strain The incremental modulus in both species was shown to increase by a factor of three along the descending thoracic aorta from the ductus scar to the celiac orifice

Soft Tissue Strain and Facet Face Interaction in the Lumbar Intervertebral Joint—Part I: Input Data and Computational Technique

Abstract: A numerical simulation was devised to determine ligament strains, facet face interaction, and disk fiber strain in the lumbar intervertebral joint under load. This technique uses experimentally derived load deflection and morphologic data from lumbar cadaver specimens from which initial and displaced soft tissue attachment points can be calculated. This allows the strain data to be derived. The effect of disk bulge is also considered. The calculated strains of most ligaments except the facet capsular ligaments were found to be insensitive to anatomical measurement variability of +/- 1 mm.