Hungarian Society of Biomechanics: E-Journals / Magyar Biomechanikai Társaság
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Assessment of a large volume maxillofacial CBCT system-from biomechanical point of view-as a tool to build patient customized bio-models
Get PDFAbstractThe number of patients diagnosed with cancer is reaching a scarily high number worldwide. This is no different in the area of mandible cancer. Unfortunately Hungary is quite high up in the ladder. The registered known number of patients with mandible cancer and the associated number of death occurrences are also showing signifi cant data in the country. However it is easy to diagnose, alcohol consumption and smoking or just bad oral hygiene really pushes the statistics. Inside the oral cavity, in case of mandible cancer and late diagnosis the only viable solution is the bone resection. To determine the extent of the cancer and to carefully plan the surgery procedure or in case of models which were created for biomechanical examinations, the medical science more and more often uses the image based processes and tools. Next to the realistically built models a more punctual mechanical parameter simulation becomes possible. It is highly important that the necessary information is extracted from the patients with the least stress. With the shortest time and smallest radiation the image must be made in a way that the scan can be well evaluated and it is usable. Within the current examination in the medical fi eld of imaging methods a gold standard MSCT and a specifi cally in the head-neck region used CBCT methods will be compared specifi cally from biomechanical modelling point of view. During the comparison the gray value was examined by the use of a cadaver head. The results show that the gray values provided by CBCT differs slightly from the MSCT values that is considered as reference. The more extent absolute error occurs with less frequency. Based on these facts the CBCT can be used for the density based material comparison for biomechanical models with less radiation dose.DOI: 10.17489/biohun/2014/2/0
Micro-FEM based mechanical anisotropy measurement of the trabecular bone, in view of the structural anisotropy
Get PDFJelen vizsgálat célja a foggyökér környezetében, a terhelések hatására kialakuló anizotrópia mérése volt. A vizsgálatokhoz 10 különböző korú férfi és nő állcsontjából származó 10 darab mintát vetettünk alá mikro-CT vizsgálatnak. A szerkezeti anizotrópia mérését beillesztett ellipszoidok – a csontállomány belső pontjai környezetében a legnagyobb olyan ellipszoid, ami úgy írható a pont köré, hogy belsejében csak csontanyagot tartalmaz, és felülete érinti a velőüreget – segítségével végeztük. Feltételezve, hogy a szerkezeti és mechanikai anizotrópia főirányai megközelítőleg egybeesnek, a kapott domináns irányokban kivágott csontkockákra mikroszerkezeti végeselemes modellt generálva lehetővé vált a szivacsos állcsont mechanikai anizotrópiájának közelebbi megismerése. A mikroszerkezet végeselemes szimulációja segítségével mérhető volt a foggyökér környezetéből származó csontminták esetén a mechanikai anizotrópia foka és becsülhető a három domináns iránybeli rugalmassági modulus.DOI: 10.17489/biohun/2015/1/01The present study aimed to determine the anisotropy around the tooth root,resulting from the loads of the jaw. 10 specimens from 10 patients were submitted to micro-CT scanning. The measurement of the structural anisotropy was conducted by means of inserted ellipsoids – the largest ellipsoids around certain points in the material, which contain bone and their surfaces touch the medullary cavity. Assuming that the principal directions of the structural and mechanical anisotropy approximately coincide with each other, conclusions could be drawn about the mechanical anisotropy of the trabecular bone, by generating a microstructural finite element model of bone cubes cut in the dominant directions. By means of the finite element simulations of the microstructure, the degree of the anisotropy could be measured and an estimation of the Young moduli in the three dominant directions could be given.DOI: 10.17489/biohun/2015/1/0
Scanning electron and optical microscopic studies of the system of porcine zonular fibres
Get PDFAbstractThe mechanical behaviour of the zonular apparatus greatly affects the accommodation process because it moves out from the ciliary muscle and runs into the lens capsule. The zonular fi bres convey the force between the ciliary body and the crystalline lens. For the measurement of the mechanical properties of zonular fi bres is necessary to know its geometry. In this paper we analyzed the network of porcine zonular fi bres with scanning electron and optical microscope. We manifested that the porcine zonular fi bre system differs from human and monkey eyes. The thickness of the apparatus of intertwined zonular fi bres is approximately 45 μm and the length from the origin to the insertion is about 1.5 mm. Based on these informations the input parameters of numerical modelling can be more precise to clarify the accommodation process.DOI: 10.17489/biohun/2014/2/0
Numerical investigation of the hemostasis process in transient blood flow
Get PDFAbstractThrombus formation is a thoroughly researched area, posing several unanswered questions. Quite many of the underlying processes are still not well understood. This uncertainty arises from the fact that the blood clotting mechanism in our bodies involves a rather complex reaction cascade with plenty of components. These underlying dynamic processes stretch over the domains of several disciplines (as there are biomechanical and biochemical reactions as well as fluid dynamical components). In this study the factors thought to be the most infl uential were selected and coupled with the transient fl ow fi eld that reacts not only to the cardiac pressure waves but also to the changing geometry of the vessel due to the clot formation. Although the number of degrees of freedom is reduced heavily, this model is already capable of qualitatively reproducing the results of in-vivo measured hemostasis.DOI: 10.17489/biohun/2014/2/0
Effects of TKR implantation methods on the kinematics of the knee joint
Get PDFA jelen tanulmány azt a kérdéskört vizsgálja, hogy a teljes felszínpótló térdprotézisek beültetése során alkalmazott beültetési protokoll jellemzői miként vannak hatással a létrejövő új ízületi kinematikára. A protézis beültetések száma egyre nő, azonban az operáló orvos csak a gyártót és a méretet választhatja meg a gyártó által ajánlott protokollal. A jó protézis elvárt tulajdonsága, hogy jól beépíthető és tartós legyen, illetve javítsa a páciens életminőségét az által, hogy megfelelő rotációt biztosít a térd behajlítása során. Ennek eredményeként a protézis által létrehozott mozgás mindinkább megfeleljen a térd természetes kinematikájának. Az operáló orvos számára a protézis beültetési protokoll az egyes beültetési szögbeállításokra (a továbbiakban faktorokra) tartományokat, adott esetben javasolt értékeket ajánl. E beültetési tényezők rotációra gyakorolt együttes hatását mérjük fel és keressük az optimális beültetési értékeket annak érdekében, hogy a rotáció-flexió mozgás mindinkább közelítse az ízület valós mozgásátDOI: 10.17489/biohun/2015/1/02The following study examines the issues that how the implanting protocol’s features of TKR knee prosthesis affect the new knee kinematics. The number of implanted prostheses are increasing, but surgeons can only chose the manufacturer and the size of the prostheses with the recommended implanting protocol. From a good prosthesis it is required to be well implantable and durable, on the other side it should improve the patient’s quality of life by ensuring the required knee rotation during the flexion movement. The movement, which is allowed by the knee prosthesis, should meet even more the human knee movement. For the surgeon the prosthesis implanting protocol offers angle ranges (further factors) or optionally recommended values to each implanting factors. Our aim is evaluate the common effect of the implanting factors to the rotation, and we are trying to determine the optimal implanting factors to the rotation-flexion movement that should approach the original movement of the knee joint.DOI: 10.17489/biohun/2015/1/0
Dynamic time warping analysis in post-stroke rehabilitation
Get PDFAbstractThis paper presents the application of the Dynamic Time Warping (DTW) algorithm in the analysis of human functional movements in activities of daily living (ADLs). Dynamic Time Warping was originally developed for automatic speech recognition, though the method has been adopted by several fi elds of biomechanics. As a part of the post-stroke rehabilitation project COSMOSYS, the aim is to quantify the ADL performances of hemiparetic subjects, hence to be able to track their progress during physiotherapy.DOI: 10.17489/biohun/2014/2/0
Compression test of the mandibular cortical bone: A cadaver study assessing formalin treated or macerated bone specimens
Get PDFAbstractNowadays the examination of implants from engineering point of view is becoming more and more supported in the medical fi eld. Instead of the more problematic cadaver examination, the computer based simulations are growing more popular. The examinations must be validated to be able to stay with the realistic situation. Using these engineering methods it became possible to do measurements on the reconstructions of a human resectioned mandible. The creation of the bone models is one of the most varying fields in the biomechanical simulation. In the literature a wide range of Young modulus for the bone cortical layers can be found and these values are actively used even in different further fi nite element simulation researches. However the proper modeling of the cortical layer thickness and correctly calibrated mechanical parameter settings bare key importance regarding the stability and connection of the implants and the fi xing screws. The values of the Young modulus are depending on many factors, for example gender or even the age, not even mentioning further different infl uencing factors. In this study destructive biomechanical examinations were carried out on bones received from dead people. The samplings of the bone were conducted from the area of the screwing used in the mandible reconstruction. Considering the results it can be concluded that the values in the literature are often not as accurate. Regarding orthotropic values of the mandible, so far has only been a small segment of information was covered. The measured values are lower than the ones in the literature. In case of the highest value it is still 3.5 GPa Young modulus in the axial direction. The results can be used in order to create a more reliable model combined with a more realistic Young modulus for the fi nite element simulation of the bone models. On these models the different scenarios of the resection cases can be estimated more precisely with examinations.DOI: 10.17489/biohun/2014/2/0
Estimation of moments acting on the pelvis in standing and in two different sitting postures
Get PDFAbstractAccording to popular consideration prolonged sitting posture in work can cause pain at different regions of the back. Many researches aiming to defi ne the relationship between these two, and as a result of noticing the problem many design solutions can be found, some of which are considered as alternative. Healthy sitting posture should be mean that with anterior rotation of the pelvisthe curve of the lumbar spine would be neutral or more preferably lordotic. In sitting the muscle balance changes thus there is more muscle activity needed for erection of the trunk and anterior rotation of the pelvis. In this study muscle activity in standing and in two different sitting postures is estimated as a difference of the two moments acting on the pelvis, which are the upper bodyweight moment and the passive elastic moment. Further investigation of the effects of hip-fl exing thigh muscles or other passive tissues on pelvic range of motion is warranted.DOI: 10.17489/biohun/2014/2/0
