Hungarian Society of Biomechanics: E-Journals / Magyar Biomechanikai Társaság
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Tracking movement of body-mounted markers through opaque orthotics
Get PDFIt is very important in marker-based motion capture systems that cameras can follow markers attached to anatomical points without any obstruction. Based on marker positions the computer program can reconstruct movement of the body’s biomechanical model by calculating typical distances, angles and trajectories.Analysis becomes complicated when the person wears a rigid and opaque orthotic device (e.g. a plastic corset), through which cameras can not see markers attached to the body surface. We had to find a marker attachment method, so that infrared motion capture cameras can follow movement of markers attached to certain anatomical points on scoliosis patients wearing their corsets, when analyzing the effects of corsets on posture and movement.Infrared cameras in the Gait Analysis Laboratory of Semmelweis University’s Department of Orthopedics can not „see through” polyethylene corsets. Markers have to be attached directly to the body surface, because a corset is a rigid body, therefore it moves differently, than the human body under it. Multiple considerations have to be made, when choosing markers. There is limited room between body and corset, markers can not affect wearer’s movement and can not cause discomfort. The chosen method uses magnets attached to the skin with medical tape. Size and properties of magnets were verified by simulation. Infrared cameras can follow the painted magnet counterparts on the outer surface of the corset.Magnets attached to the corset’s outer surface follow the movement of magnets taped to the body, so cameras can follow movement of anatomical points under the opaque corset, without the need of providing direct visibility by destructing corset material. Holes larger than the size of markers would be required, to avoid the shading effects of the corset resulting from body-corset and body-camera distance and angle.According to measurement results of patients with and without corsets, magnetic markers sufficiently follow the body’s movement under the corset. In the meantime with markers attached immovably to the corset’s outer surface, movement of the corset as a rigid body can be tracked, as well.The presented method allows further detailed investigation, concerning the movement altering effects of not just corsets, but other orthotics, too. DOI: 10.17489/biohun/2013/1/1
Angel Heel rendszer: új mérési technika a részleges alsóvégtag-tehermentesítés tanításában és ellenőrzésében
Get PDFIn 2012 a three-round clinical trial started to test a new system developed by Metalelektro Méréstechnika Ltd. called Angel Heel by three different medical institutes. The tests of the system that was developed for controlling and training partial weight bearing based on acoustic feedback were performed with 150 people (in most cases after a hip or knee Total EndoProsthesis [TEP] surgery) in one year.The summarized results showed that the rate of patients’ lower limb overload decreased by 54% when the acoustic feedback of the system was activated. Also, the absolute amount of the overload was signifi cantly decreased (by 27%) related to the case when the acoustic feedback was deactivated. The clinical trial clearly proved the effi ciency of the Angel Heel system because it signifi - cantly decreased the amount and the rate of the injurious lower limb overloads during the rehabilitation.2012-ben indult az a három részből álló klinikai vizsgálatsorozat, amely során a DE OEC OrtopédiaiKlinika, a Kenézy Gyula Kórház és Rendelőintézet Rehabilitációs Osztálya és a DE OECOrvosi Rehabilitáció és Fizikális Medicina Tanszéke tesztelte a Metalelektro Méréstechnika Kft.által kifejlesztett Angel Heel nevezetű rendszert. A hangvisszajelzésen alapuló, az alsóvégtagrészleges tehermentesítésének kontrollálását és betanítását szolgáló rendszer tesztjei 150, főlegtérd- és csípőízületi total endoprosthesis (TEP) műtéten átesett résztvevő bevonásával, egy évalatt zajlottak le. Az összesített eredmények azt mutatták, hogy a rendszer hangvisszajelzésénekalkalmazásával az előre meghatározott maximális terhelést a betegek mintegy 54%-kal kisebbarányban lépik túl, valamint a túlterhelés mértéke is jelentősen, 27%-kal csökkent a hangjelzésalkalmazása nélküli esethez képest. A klinikai vizsgálatok egyértelműen bizonyították az AngelHeel rendszer hatékonyságát, hiszen lényegesen lecsökkenti a rehabilitáció során a káros következményekkeljáró alsóvégtag-túlterhelések arányát és mértékét is. DOI: 10.17489/biohun/2013/2/0
A Slooff-technika nanokompozit csontpótló anyaggaltörténő alkalmazhatóságának meghatározása biomechanikai vizsgálatokkal
Get PDFA nano-composite based material has been developed by two work teams at the University of Debrecen for the treatment of particularly large bone defects; the project was supported by an OTKA grant. In case if this material is used for fi xing a cementless revision hip prosthesis, the possibility of using the so-called impaction Slooff-technique has raised. We accomplished three biomechanical experiments to decide whether our bone substitution material is suitable for using in Slooff-technique. Summarizing our results, we have found that the method can be applied safely when the thickness of the cortical bone is higher than 1 mm.A Debreceni Egyetemen két munkacsoport egy OTKA pályázat keretén belül egy nanokompozitalapú csontpótló anyagot fejlesztett ki, amely különösen alkalmas nagy csontdefektusokkal járóműtétek esetén a csontszövet pótlására. Ha ezt az anyagot revíziós csípőprotézisszárak cementnélküli rögzítésére használjuk, akkor az impaktációs ún. Slooff-technika alkalmazásának lehetőségeis felmerül. Annak eldöntésére, hogy a csontpótló anyagunk alkalmas-e a Slooff-technikamegvalósítására, három biomechanikai kísérletsorozatot végeztünk. Eredményeinket összesítveazt állapítottuk meg, hogy 1 mm-nél vastagabb corticalis esetén a módszer biztonságosan alkalmazható. DOI: 10.17489/biohun/2013/2/0
Development and test results of a system for the recovery of the lower limbs
Get PDFAccording to medical research,1 exertion of a certain level of loading to injured lower limbs is considered as important from the point of view of their recovery. Total unloading would decelerate coalescing of bones just like their permanent overloading. In order to avoid it, patients must be trained to walk with optimal load on lower limbs. A data logger with built-in load cell is designated both to sustain this process and to store data on load values exercised to limbs during recovery as well. The report below tells how this device was developed. DOI: 10.17489/biohun/2013/1/2
Anodisation of medical grade titanium
Get PDFIn recent years the number of titanium dental implants in use has significantly increased. At the same time bacterial infection of implants has become more common. The goal of our study was to develop a titanium-dioxide layer on the surface of titanium implant materials by anodisation with a view to impeding the attachment of contagious bacteria. In our experiments Grade 2 titanium and nanograin Grade 2 titanium discs were subjected to anodisation. We investigated the effect of voltage on the surface pattern of emerging titanium-dioxide. We examined the surfaces by reflected-light microscopy. We found that the value of the applied voltage and variation in grain size affected the thickness of the formed titanium-dioxide layer. These layers may promote or support desired forms of biological activity, such as cell attachment to integrate with bone. DOI: 10.17489/biohun/2013/1/2
Mechanical behaviour of healthy and damaged human arteries and validation of parameters derived from experiments
Get PDFOur research group aimed to develop a numerical model for the analysis of healthy and damaged human blood vessels (e.g. an aneurysm, an adverse vasodilatation) and to investigate the hyperelastic mechanical response of human brain arterial tissue. One of our tasks was to perform laboratory analysis on the specimens taken from the wall of the vessel, to calculate material model parameters for numerical models based on our measurements. Biaxial biomechanical characterization of living tissues – like the artery walls – provides important information about their in vivo behaviour. The aim of our research is to estimate stresses of the aneurysm wall and its parent artery, and to estimate the likelihood of a later aneurysm rupture, too. Laboratory measurements have been undertaken, we have taken the specimens of the vessel wall from human cerebral aneurysms and from control healthy artery carotis interna (both from surgery and cadavers), and then we investigated the biomechanical properties of samples in uniaxial and biaxial tensile tests. We attained for this by means of processing the values of the deformations and (Cauchy-)stresses arising from the wall. We verified the necessity of the parameters calculated from the laboratory measurements with finite element simulations performed on a real geometry aneurysm sack. From our study it may be concluded that there is a need for a constitutive model which describes the hyperelastic behavior of the human arterial wall. We demonstrated with numerical simulations that consideration for inhomogenity in investigations of diseased segments of blood vessels has crucial importance. We proved that damage taking place in aneurysm-sacks is many times more presumable than in healthy material parent arterial segments. DOI: 10.17489/biohun/2013/1/1
Biomechanical evaluation of two different vertebral interbody devices by using QCT-based case-specific nonlinear finite element models
Get PDFInterbody devices are widely used to replace the degenerated discs of the spine. For this purpose, a novel methodology uses cement instead of conventional spacers, which is hypothesized to provide smoother transition of forces, lower risk of bone tissue damage, thus smaller subsidence, reduced risk of further pathological deformations and other complications. This new treatment approach has been compared with the conventional method experimentally by mechanical loading of human vertebral motion segments treated with either of these. The present study aimed at complementing the that work with finite element analysis and, by performing in silico mechanical testing of QCT-based case specific models incorporating the elasto-plastic behavior of bone, providing better understanding of experimental results, in particular, the differences between the two sample groups equipped with the different spacer types. This report presents the applied numerical methodology as well as the first results, which are in line with the experimental ones. Besides providing deeper insight into the experimental outcomes, these models are expected to provide a basis for virtual parameter analysis studies, which may help to optimize the surgical procedure. DOI: 10.17489/biohun/2013/1/2
Experimental and numerical analysis of the influence of embedding thickness in compressive mechanical testing of vertebral augmentation and spinal interbody fusion
Get PDFFor in vitro mechanical testing of biomechanical objects the specimens must generally be embedded into a special material to obtain a stable position in the testing machine. However, the experimental boundary conditions may influence the results of the measurements. In this study the effect of embedding thickness on the mechanical properties of vertebrae treated by vertebroplasty and kyphoplasty and lumbar motion segments treated by interbody fusion with PEEK and PMMA cement spacers is analyzed by using compressive mechanical tests and QCT based specimen-specific finite element simulation. DOI: 10.17489/biohun/2013/1/3
Determination of reference function to knee prosthesis rating
Get PDFThe knee joint is one of the most complicated joints in the human body. Fundamental knowledge about kinematics is essentially important in order to design knee prostheses which are functionally similar to the knee joint. In addition, the prosthesis should carry out similar kinematics, since only the geometrical resemblance is insufficient. As an initial step, an experimental apparatus, a test protocol and an evaluation method were developed which allows the investigation of the human knee joint kinematics. Based on the results of multiple experiments, a reference function was determined, which provides guidance on how the flexion-rotation function in the human knee joint can be described. The function also provides reference about the kinematics which should be defined in the design of prostheses, and to what extent does an arbitrary knee prosthesis follows the required kinematics. The definition of knee rotation is reported in this article. DOI: 10.17489/biohun/2013/1/3
