Technology and Health Care - Volume 14, issue 4-5

Article Type: Editorial

DOI: 10.3233/THC-2006-144-501

Citation: Technology and Health Care, vol. 14, no. 4-5, pp. 199-200, 2006

Authors: Ohrndorf, A. | Krupp, U. | Christ, H.-J.

Article Type: Research Article

Abstract: The aim of this paper is to report on the characterization of the influences of foam homogeneity and the cell strut material on the mechanical behaviour and the fracture mode of metallic foams that are promising candidates for new perfectly tailored medical implants. For two open-cell foams with identical cell geometries produced in the same precision-casting process but using different cell strut materials, the stress-strain behaviour and the evolution of damage until fracture is compared. To account for effects arising from a change in the geometry of the cell structure and the resulting homogeneity of the foam, the main characteristics …of fracture for the group of closed-cell foams were included in this study. Monotonic tests carried out in compression revealed that foam homogeneity is the major factor with respect to the formation of deformation bands prior to cell collapse in metallic foams. The influence of the cell strut ductility is particularly pronounced in monotonic tension where the fracture mode changes from extremely brittle fracture to strongly plastically deformed cells, with substantial fracture elongation. In tension-tension fatigue as well as under symmetric push-pull loading conditions, damage is governed by a combination of cyclic creep and fatigue crack propagation through the specimen. From a mechanistic point of view no fundamental differences between the three foams tested were detected for these loading conditions. However, in compression-compression fatigue the same dependencies in terms of homogeneity and ductility influence the mechanisms of strain evolution that are active in monotonic compression. Show more

DOI: 10.3233/THC-2006-144-502

Citation: Technology and Health Care, vol. 14, no. 4-5, pp. 201-208, 2006

Authors: Liepsch, Dieter

Article Type: Research Article

Abstract: Biofluid mechanics is a complex field that focuses on blood flow and the circulation. Clinical applications include bypass and anastomosis surgery, and the development of artificial heart valves and vessels, stents, vein and dialysis shunts. Biofluid mechanics is also involved in diagnostic and therapeutic measures, including CT and MRI, and ultrasound. The study of biofluid mechanics involves measuring blood flow, pressure, pulse wave, velocity distribution, the elasticity of the vessel wall, the flow behavior of blood to minimize complications in vessel,- neuro-, and heart surgery. Biofluid mechanics influence the lungs and circulatory system, the blood flow and micro-circulation; lymph flow, …and artificial organs. Flow studies in arterial models can be done without invasive techniques on patients or animals. The results of fluid mechanic studies have shown that in the addition to basic biology, an understanding of the forces and movement on the cells is essential. Because biofluid mechanics allows for the detection of the smallest flow changes, it has an enormous potential for future cell research. Some of these will be discussed. Show more

DOI: 10.3233/THC-2006-144-503

Citation: Technology and Health Care, vol. 14, no. 4-5, pp. 209-214, 2006

Authors: Vejpustková, J. | Vilímek, M. | Sochor, M.

Article Type: Research Article

Abstract: Today artificial neural networks can be trained to solve problems that are difficult for conventional computers or human beings. The big advantage of an artificial neural network is results obtained without knowledge of the algorithm procedure or without full and exact information. Therefore an artificial neural network was used to predict the muscle forces. The aim of the study was to simplify prediction of muscle forces which are difficult to determine, because many muscles act cooperatively. However, orthopeadists, biomechanical engineers and physical therapists need to take muscle forces into consideration because joint contact forces, as well as muscle forces, need …to be estimated in order to understand the joint and bone loading. In terms of sensitivity of the muscle parameters to the results from the proposed neural network object, the muscle force prediction was simplified. Show more

DOI: 10.3233/THC-2006-144-504

Citation: Technology and Health Care, vol. 14, no. 4-5, pp. 215-218, 2006

Authors: Goldmann, Tomáš | Seiner, Hanuš | Landa, Michal

Article Type: Research Article

Abstract: Elastic properties of single parts of a human skeleton are necessary to know for modelling bone tisue-implants interactions as well as for diagnostic purposes. This paper contributes to the methodology of the evaluation of elastic properties of bones by the ultrasonic wave inversion. The method was developed on composite structures such as plates and cylindrical shells. Final results are then demonstrated on the bovine cortical bone specimen. Properties are supposed to exhibit an orthotropic or a transversally isotropic symmetry. Quasi-longitudinal and quasi-transversal waves are generated from the wave diffraction on the liquid/specimen interface. Wave velocity fields obtained by …the ultrasonic scanning technique are used as an input to the inversion procedure for all elastic constants determination. Experimental results are confronted with the numerical modelling of the wave propagation and the stability of resulting data is evaluated by the statistical method based on the Monte-Carlo simulation. The suggested approach has a potential for the qualify of such measurements performed on fresh bones and also for improvement in-situ ultrasonic techniques. Show more

DOI: 10.3233/THC-2006-144-505

Citation: Technology and Health Care, vol. 14, no. 4-5, pp. 219-232, 2006

Authors: De Beule, M. | Van Impe, R. | Verhegghe, B. | Segers, P. | Verdonck, P.

Article Type: Research Article

Abstract: In Western countries, cardiovascular disease is the most common cause of death, often related to atherosclerosis. This paper offers a brief introduction into some aspects of this disease and its treatment, where the use of stents is gaining increasing importance. Stents are supporting – mostly metal – tubular mesh structures which are opened in an obstructed artery in order to reopen it, and to offer radial strength to prevent elastic recoil of the dilated vessel. In addition to a variety of experimental tests to study the behavior of (new) stent designs, advanced numerical models (e.g. Finite Element Models) may offer …interesting insights in the mechanical behavior of stents and will undoubtedly influence the design of future generation stents. A brief literature review on numerical studies dealing with the mechanical behavior of stents is presented. Subsequently, the finite element method is exploited to investigate and compare different designs of a “first generation” Palmaz Schatz stent in order to reduce the dogboning (i.e. ends of stent open first during expansion) to a minimum. Our computational models (Abaqus [1]) are described in terms of geometry, constitutive material models, numerical aspects and output quantities. Altering the original symmetric stent design to asymmetric designs decreased the dogboning from 27.24% to less than 10% for the vast majority of the studied asymmetric designs. For one particular configuration, the dogboning effect vanished completely. For this reason, taking asymmetry into account in the design of stents seems very promising, at least from the perspective of dogboning. However, as the dogboning only takes into account the radii (R) at the central and distal part of the stent, nothing can be concluded concerning the uniformity of the complete stent expansion. The mean value (Rm ) and the root mean square (RRMS ) of radii (differences) of the stent at the end of the loading phase (P=0.7 N/mm2 ) are much better parameters to give a clear indication of the uniformity of the expanded stent's shape. Although the model is suitable to study basic aspects of stent deployment, further research is necessary, especially accounting for newer generation stent geometries and more realistic balloon-stent interaction. Show more

DOI: 10.3233/THC-2006-144-506

Citation: Technology and Health Care, vol. 14, no. 4-5, pp. 233-241, 2006

Authors: Zsidai, Attila | Kocsis, László

Article Type: Research Article

Abstract: A modern motion analysis laboratory was installed by way of several scientific research instrumentation grants awarded to the Department of Applied Mechanics, BUTE. Motion and spine analysis is performed by a CMS-HS ultrasound-based system. System operation is based on ultrasound spread characteristics. In the area of spine analysis, it is possible to investigate the shape of the spine, its movement characteristics, mobility, and the movement characteristics of the cervical spine separately. The results of traditional spine tests are adequately supplemented by the results of the tests performed by this motion analysis system, considered to be a specialty throughout Europe. With …the EMG (ElectroMyoGraph) sensors specify whether the muscles operate insufficiently or become active during the wrong motion, limiting the patient in motion. Show more

DOI: 10.3233/THC-2006-144-507

Citation: Technology and Health Care, vol. 14, no. 4-5, pp. 243-250, 2006

Authors: Paróczai, Róbert | Kocsis, László

Article Type: Research Article

Abstract: Recently, there has been great improvement in the field of movement analysis, which is a worldwide tendency. There is a continuous improvement of new methods, combined with traditional ones. In the last few years, we have managed to set up a modern, absolutely up-to-date motion analysis laboratory at the Budapest University of Technology and Economics (BUTE). The primary purpose of this study was to determine usual walking and running parameters as a function of speed and compare our results with the data of other studies. We tested the gait and running characteristics of people at different speeds, measuring …the usual parameters of walking and running. On the basis of these measurements, we observed the interrelation of the three main parameters of gait and running (speed, cadence, stride length) and determined the dependence of cadence and stride length on speed as well. The determined energetically optimal walking speed (EOWS) and the usual walking speed (UWS) correlate well with the values in literature. Our measurements were performed on a running corridor, and at the facilities provided by the Biomechanical Laboratory, including an instrumented treadmill connected to the measurement system. Show more

Keywords: Gait analysis, running analysis, kinematic and kinetic parameters, speed

DOI: 10.3233/THC-2006-144-508

Citation: Technology and Health Care, vol. 14, no. 4-5, pp. 251-260, 2006

Authors: Füchtmeier, B. | May, R. | Fierlbeck, J. | Hammer, J. | Nerlich, M.

Article Type: Research Article

Abstract: A new humerus nail (Sirus™) has become available for the treatment of fractures of the proximal humerus. The aim of the study was the biomechanical comparison of this implant with established systems. 12 matched pairs of human humeri were employed for testing. Three randomized groups were formed (n=4 pairs). A bending moment of 7.5 Nm and a torsional moment of 8.3 Nm were applied in a test of five loading cycles to all intact bones. Loading was consistently initiated at the distal epiphysis. The consequent deformation at the distal epiphysis was continuously recorded. Then an osteotomy with a …defect of 5 mm was created to simulate an unstable subcapital humerus fracture. For paired comparison, one of each pair was stabilized with the Sirus proximal humerus nail. The other side was fixed with a reference implant. The following groups were created.: Group I: Sirus versus Proximal humerus nail (PHN) with spiral blade. Group II: Sirus versus PHILOS plate. Group III: Sirus versus 4.5 mm AO T-plate. The proximal humerus nail (Sirus) demonstrated significantly higher stiffness values than the reference implants for both bending and torsional load. The following values were recorded at a bending moment of 7.5 Nm: Sirus 14.2 mm, PHN 20.7 mm, PHILOS plate 28.1 mm, 4.5 AO T-plate 29.3 mm p<0.0012). The values at 8.3 Nm torsional moment were: Sirus 8.5°, PHN 12.3°, PHILOS plate 16.4°, 4.5 AO T-Platte 15.6° (p<0.002). The intramedullary load carriers were biomechanically superior when compared to the plating systems in the fracture model presented here. Supplementary, the Sirus Nail showed higher stiffness values than the PHN. However, the latter are gaining in importance due to the possibility of minimal invasive implantation. Whether this will be associated with functional advantages requires further clinical investigation. Show more

Keywords: Proximal humerus fractures, biomechanical analysis, Sirus nail

DOI: 10.3233/THC-2006-144-509

Citation: Technology and Health Care, vol. 14, no. 4-5, pp. 261-270, 2006

Authors: Vaverka, Michal | Návrat, Tomáš | Vrbka, Martin | Florian, Zdeněk | Fuis, Vladimír

Article Type: Research Article

Abstract: Many disorders of the hip can be treated with a suitable osteotomy based on the improvement of mechanical conditions in the hip joint. These operations, such as osteotomies are very complex. The surface replacement has also been developed as an alternative to a total hip replacement for young and more active people. It is up-to-date to concern with biomechanics of pathological hips and it is necessary to supplement the existing clinical findings with the results of mechanical analyses. Several finite element (FE) models are presented in this paper. The first one offers solutions to the strain-stress analysis of the physiological …hip. The second one represents dysplastic hip joint. Another two computational models of both hips of a young patient were created (FE model of physiological hip and pathological hip affected by Perthes disease with a deformed shape of the femoral head). Also a computational model is presented, which enables us to investigate strain and stress parameters in the hip joint with applied surface replacement. The strain and stress analysis was performed by means of finite element method (FEM) in ANSYS system. Show more

DOI: 10.3233/THC-2006-144-510

Citation: Technology and Health Care, vol. 14, no. 4-5, pp. 271-279, 2006