Study and examination of the implements used for securing pelvis bone

Our goal was to compare the direct plate known as the “gold standard” technology in case of a pelvis fracture with the H-plate technology reinforced with iliolumbar fusion and the pelvis screwing technology reinforced with iliolumbar fusion, especially focusing on the matter of stability.In our work we studied and examined the securing possibilities and stability of the transforaminal pelvis fracture using the finite element analysis. My colleauges and I created the anatomically correct model (including the 4th and 5th lumbars and cartilages under the lumbars). To create the model we used a previous geometric model used for older preceding analyses. During the modeling we perfected the geometry; we separated the different bone regions and paid close attention to create the scale model of the implements. The placements of the implements are appropriate and in accordance with real surgery procedures. We examined three different cases: standing on the healthy leg, standing on both legs and standing on the injured leg. The boundary conditions for the finite element analysis: the femur is fi xed and in case of standing on one leg the opposing side of the hip bone is fixed on both the X and Z axes directions. Furthermore both hip bones are fixed on the Y axis direction, and this applies when standing on both legs as well. We added the load to the 4th lumbar on the model. The value of the load is 500 N and the direction is –Z. We defined surface to surface connection between the femur and acetabulum and also between the side of the symphysis pubica and the fracture ends. We defined bonded connection between all the other components. In our analyses and evaluation we examined the arising stress values and also the displacements in the cortical and spongiosa regions and in the implements. We examined the elongation of the ligaments in the pelvis and measured the maximal distance between the fracture ends under load.Considering the results of the stress states, the iliolumbar fusion technologies provide more stability. Therefore it is recommended to use these technologies, not mentioning the fact that the dorsal exposure puts the patient through considerably less trauma.Considering the results of the fracture ends displacements it can be declared that the reason for the existence of the H-plate technology reinforced with iliolumbar fusion cannot be questioned. Therefore continuing the research can be justifi ed by further analyzing and examining dynamic loads on models extracted from CT images. DOI: 10.17489/biohun/2010/1/2

Effect of preloading on lower jaw implant

The procedure of mandible resection is basically unavoidable in case of cancer in the field of oral surgery. The reinforcement and the reconstruction of the jaw closest to its original condition is very challenging. Considering the load properties the examination of the plates used in the reconstruction is highly important. The cadaver examination procedure however is very difficult to execute, therefore the use of the Finite Element Analysis proves rather supportive. Fast recovery can be achieved by applying the implants correctly. Furthermore brakeage resulting from high loads in the plates can be avoided. The goal is to examine and understand the Non-locking screwing technique used with plate implants in different mandible resections and reconstructions, focusing on the preloaded force. Furthermore the study and comparison of different stress that arise in different cases.A toothless mandible was used for the creation of the Finite Element Analysis model. The data was provided for the model by CBCT. During the creation of the model we separated four different resection areas to which we used the plates with the Non-Locking screwing technique, also used in clinical reconstructions. For the preload of the plates we used different preloaded forces on the screws. We considered and used boundary conditions complying with the anatomical structure. The muscles required for chewing were transferred to the model and used as main loads. The bone structure is heterogenic and the bone density is based on CBCT.The preloaded forces have a major role in the stresses arising in the bone during the use of Non-locking technique. The comparison of the resection techniques can provide valuable information regarding the preloaded condition and the following chewing load condition connected to the main loads in the bone.Those measurements that are important from biomechanical point of view and would prove difficult or impossible with in vivo or in vitro load measurements to be examined can be compared with the Finite Element Analysis method. DOI: 10.17489/biohun/2013/1/0

Compression test of the mandibular cortical bone: A cadaver study assessing formalin treated or macerated bone specimens

AbstractNowadays 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

Assessment of a large volume maxillofacial CBCT system-from biomechanical point of view-as a tool to build patient customized bio-models

AbstractThe 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

Finite element analysis of the lower jaw implant in different resection scenarios

The goal of the research is to examine the different reconstruction solutions, which are used for the often-occurring jaw cancer resection and finding those areas that show higher potential risks of implant fracture. Within the research some finite element analysis based on data provided by Computer tomography have been concluded. The model in practice is built up with the most frequently used reconstruction plates and monocortical screws. Both lock and non-lock system solutions were examined. The results supporting the practice showed that indeed the maximal stress would rise in the implants closer to the resection in case of screws and in case of plates this will occur in the closer areas of resection within the thinner cross-sections