 Good afternoon everybody. Thank you for attending to this seminar before everything. I should apologize for any inconvenience because I have got caught cold and I apologize for that. Today I'm going to present some highlights about the application of the finite element analysis or FEA in biomechanics and also I used computed tomography imaging data in this order. Now let's see first see what is finite element analysis. Based on Wikipedia the finite element analysis or FEA is a numerical method for solving problems of engineering and mathematical physics. One of the most important thing engineer and scientist to do is modeling natural phenomena. For example consider here we have hips, sacrum and femur here and we want to see the effect of applying load on the head of the femur. So in this reason we should develop conceptual and mathematical models and we should separate this part of the body and study the boundary conditions and then we should follow up and find the mathematical models to predict and simulate this physical phenomena. In this order we need to extract some formula could be in algebraic differential or integral equation and for example we could have some elasticity equation and as you can see most of them are in the differential equation and sometimes finding the exact solution for this equation is a difficult task. So in such cases finite element analysis help us and this is one of the most commonly numerical methods to provide alternative means to find the solution for the following complex equation and in this order we have some steps. First we should discretize the domain with these simple primitive shapes depending on what type of the analysis we want to follow up we can select some type of these elements or combination of them. Here we discretize the domain the femur domain with these simple elements then we should derive and assemble element equation. After that we should apply material property each element should have its material property which come from the model and then apply the load and boundary condition here boundary condition and at the bottom of the femur is the fixed constree and excuse me then solving the equations and at the final step we can show the distribution of the result. Here shows the result of the finite element analysis and it shows the distribution of the stress all around the body from the head of the femur to the bottom of that and as you can see each color represents its own result or stress in megapascal for example red color indicates the higher amount of the stress while the blue one shows the minimum amount of stress and this analysis shows we have the maximum amount of stress in the neck of the femur. Now let's have a quick see at the what is the computed tomography or CT. This is a non-invasive medical examination that excuse me uses a specialized x-ray equipment to produce cross sectional image of the body based on the FDA definition. You can see we have here an uncovered CT device and here you can see the x-ray tube on the opposite of that you can see the row of detectors and this is called the gantry excuse me by simultaneously rotation of the gantry and movement of the patient table we can have the slice by slice x-ray images of the body organ. Here it shows an example animation of the CT images a slice by slice you here you can see the vertebra and then you can see the hips sacrum and femur from the top to the bottom of the body. Now here's a few application of FEA in biomechanics it showed the femur meddling after using the CT techniques CT imaging techniques we have the slice by slice x-ray images of the head of the femur and then we apply discretization steps in the finite element method and after that here shows the discretized model and after that we can apply and enter the material property from the model to the finite element and we can use this type of application to see the effect of the loads which applied at the head of the femur and see the distribution on the neck of the femur and see where is the critical position in applying the load. Here shows an example of finite element analysis in orthodontics you can see this is the maxillary central incisor and the red portion shows the pulp of the teeth tooth excuse me and the blue color around the root shows a periodontal ligament which is an impact observer impact damper around the root this shows the molar with three roots and pulp and PDL around the roots and this shows all of the teeth in maxilla and actually we did that to design some practice for a veteran which lost the right part of his maxillarities and we used this model to design some practice and we used the left side to give good support for that practice and analyzed that and selected the best position to put the practice around the teeth. Now some of my previous works actually been finite element modeling in vertebra using techniques from medical image processing and finite element analysis. In this order to predict the failure initiation or to evaluate treatment in human vertebra samples extracted from the cadavers and then they were CT scanned this is type of the CT sliced images excuse me and then the CT scanned process to convert into the finite element model first created the 3d model and then we discretized that and applied material property and after applying the force and boundary condition we can see the result of the stress distribution of the stress all around the body of the vertebra. We used that excuse me we use this method to predict any failure initiation or and to follow up the treatment method which performed on the vertebra. In order to compare the effect of the treatment on the vertebra we created three types of the samples first this is the intact sample which extracted from the cadavers. This is the defective sample which as you can see here we created an artificial defect inside that by using CNC machine and here is the augmented sample or after treatment where this sample filled up with some special bone cement excuse me. The process or filter that we followed is as you can see is following first the sample or patient goes to the CT imaging and the CT device or CT imaging gives us the raw images and as you can see we have the gray color around the body we should remove and get rid of these part. For this reason we process the images and remove the unnecessary surrounding and then we assembled the slices and then made the 3d model final element model applying boundary condition material property loads and extract the load displacement diagram. Here you can see the animation of the excuse me raw images you can see here we have gray color around the bone around the vertebra this could be the shadow or images of another organ which is near or next to the vertebra we should get rid of them so by applying image processing techniques we removed all unnecessary surrounding around the bone then we assembled the slices to check the shape and continuity of the model you can see this shows the slices from the superior end plate of the vertebra to the inferior end plate this shows the wireframe model of the vertebra the application of this type of model is we can quickly or at the glance can take a look at the detail of vertebra is inside that this shows the three-dimensional model of the vertebra and by using this type of model surgeon can 3d print that to make the plan before the surgery and make more familiar with the body before any operation this shows the waxel based finite elements and the name is waxel based because each element comes from the waxel or pixel images of the city slices as you can see this shows one slice of the city image and we discretized that exactly equivalent to the pixels from the city image and we put the element on each pixel exactly the same size of the pixel in in this analysis the pixel size was 0.25 by 0.25 millimeter so the size of the element is the same but the slice thickness was one millimeter so in this reason we sweep the element one millimeter and make a cube element equivalent to waxel of the city images then excuse me we repeated this procedure for all the sections and you can see the creation of the elements from the inferior end plate to the superior end plate of the vertebra after that next step is applying the material property and in this order we calculated material for each element and applied that in the model from the bottom to the top you can see each color represents its own property its own material property including modules of elasticity Poisson ratio density and such up as bone material property comes from the density of the bone we first we should create the distribution of the bone mineral density for the bone or for the vertebra and then and you can see this shows the distribution of BMD and then each each amount of the density by applying the related formula can convert to modules of elasticity Poisson ratio and mechanical properties and as you can see this has another can we have another call application we can cross it remove some part of the of that and take a look at inside the body and see the distribution of the density and we can see if there is any osteoporotic defect inside that so depending on the cts slice thickness and resolution of the city imaging because our elements exactly are corresponding from the corresponding or equivalent to the waxel size it dictates the number of elements so for this reason we have a lot of elements and it calls it costs computational cost it increased the time of the computation that needs a special hardware to overcome that we applied mesh courseening excuse me and as you can see we increase the size of the elements instead of point 25 we increase that to one by one and it increase significantly in decrease the number of elements and increases speed of analysis if you take a look at this part and I zoom it in you can see we have different color and as I told you as I said each color represents its own material property and if you look at this one it means that it has different material property with its neighbor so it calls heterogeneity and we actually applied heterogeneous material property in our model the next step is excuse me applying boundary conditions here we wanted to simulate the lifting situation on the vertebra for this reason we fixed the inferior end plate in the axial direction while we applied displacement in axial direction on the superior end plate and after performing the finite element analysis we have the distribution of the stress all around the body and as I mentioned before each color represents its own magnitude of the stress and the red color shows the maximum amount while the blue one shows the minimum amount of the stress excuse me as each finite element analysis should be validate the result should be validated because we don't know if whether the result is correct or not so we validated the finite element result with experimental with experimental test we took the sample to the lab and put similar compression on the vertebra and extract the load displacement diagrams as you can see the black color shows the load displacement diagram for the experimental and the red one shows the finite element curves and here you can see the slope of all curves are the same so this shows that the stiffness of the both analysis are the same and it validated the results after that we go further step excuse me and we perform failure analysis on the vertebra as you can see here and take a look at the amount of the load it's around 500 Newton by applying this this load we can see some micro failed micro failure elements on the body and by increasing the amount of the load for example here to 2000 Newton number of the failed region increased again by applying by increasing the amount of load the number of the failed region increased they grows they join together and make a weak area around the vertebra and it caused the final fracture and after that it shows that we have the final fracture and analysis stopped here shows animation of the progression of the failure pattern failed region all around the body you can see first we have a small number of failed region and then if they increase they join together and make the weak area and it shows the prediction of the collapse region from the finite element analysis by applying the compression load on the top of the vertebra and fixed in the bottom of that you can see the collapse region which it predicts and also this prediction validated by the experimental result you can see we have here we have collapse region which is exactly the same that finite element predicts this shows the progression of the failed region here blue color indicates the failed region and from the posterior lateral view you can see the creation and growing the failed region here it shows the anterior lateral view of the failure pattern again the blue color indicates the failed region here again we validate the predicted result by here by plane radiography as you can see here it predicted failure in the lateral view lateral view of the vertebra so plane radiograph of lateral view of the experimental result experimental sample shows the same behavior of the fracture and also here it shows the anterior posterior view and the x-ray from the anterior posterior direction shows the same behavior of the fracture to to study the effect of the excuse me defects inside the sample as I told you before we separate some intact samples and then we create the artificial defect inside that by using the CNC machine this shows the x-ray of the defective sample and you can see the size and location of the defect inside the vertebra and by following the same procedure we established the finite element model and then analyze that and also this shows the bone mineral density distribution layer by layer from the bottom to the top of the sample and you you here you can see the cross section of the defect in each layer each section after that we applied the load the boundary condition on that and analyze that and save the data to compare for to compare with the intact and treatment sample the model has the ability to predict the osteolytic effect and also osteoporotic defect in the model to study the effect of the treatment we follow up the augment augmentation procedure or vertebra plastic in this procedure we injected some special bond cement inside the vertebra and you can see this is the augmented sample and then we applied the same procedure to model the finite element this shows the city images this shows the finite element and here you can see the tip of the the place that we injected the cement inside the vertebra result of augmentation model shows that although it increased the height and strength of the vertebra but here you can see some end plate fracture on the augmented samples which these fracture pattern validated by the experimental test and in in this sample in this sample it predicts the fracture on the end plate in this direction which is validated by plain x-ray radiograph you can see here the fracture pattern and it shows the bond cement or PMMA inside the sample to study the effect of the position of the bond of the special bond cement inside the vertebra we simulated the vertebra plastic with a special shape here we got the spherical shape of the PMMA or bond cement and put it in different position inside the vertebra for example here we placed it shows a section of the vertebra which you can see the bond cement inside that we placed the PMMA or bond cement closer to the superior end plate here and here we place that closer to the inferior end plate here it plays closer to the lateral wall and here it plays closer to the anterior wall and here it's closer to the posterior wall after analyzing all of these finite element models and putting the related force and bond conditions we extracted the results to compare this shows the strength distribution of the vertebra and the horizontal axis shows the different position for each vertebra here is the position for L1 positions of the bond cement for the L2 position of bond cement for T12 or thoracic vertebra and as you can see the red color shows the intact model before analyzing we perform finite element analysis and we find the strengths of the intact samples then we created the defect artificial defect inside the vertebra and performed analysis and you can see the distribution of the strengths it shows that the defect existence of the defect inside the vertebra decrease significantly the amount of the strengths comparing to the intact strengths for all of the samples then we analyze the effect of the augmentation and the blue one show the strengths of the augmented model and as you can see here in posterior location we have the we have much increased more increase in the strengths for the L1 and here also it shows that if we put the bond cement place it in the posterior position it has more increase in the strengths for the L2 and actually for the thoracic it predicts the same behavior to simulate the distribution of the bond cement inside the vertebra we simulated the PMMA with elliptical shape and by positioning the major axis of the ellipse in different direction we simulated the position of the the distribution of the PMMA for example here the major axis it shows a cross section of the model which bond cement is injected inside that you can see the major axis of ellipse is located in the superior inferior direction and here the major axis of ellipse located in anterior posterior direction and here it's placed in medialateral direction and after analyzing all of these models you can see the comparison between the intact defective and augmented models again this vertical axis shows the strengths in kilonewton and the horizontal shows the distribution of the bond cement for each type of the vertebra the red color indicates intact the green shows the defective and blue shows the augmented model you can see by comparing these results the normal is here for all of the vertebra defects reduce significantly the strengths of the vertebra comparing to the intact for all of the samples and augmentation here in different direction or different distribution for example here in anterior posterior and but here in superior inferior we have more increase in the amount of the strengths here for lombard 2 superior inferior is higher and here again it's higher but is closer to the another amounts so it showed that by choosing different position and different distribution or direction we can gain different amount of the strengths in the vertebra so we should consider that during the vertebra plastic procedure as a summary through this presentation you saw there are many application for the finite element analysis in biomechanics and also saw the ability of finite element to predict failure creation and follow up the effect of the treatment on the defective vertebra we got intact sample created defect inside them followed the augmentation procedure and created the finite element analysis and it showed that the side effect of the augmentation and the amount of the increase which when we placed the different location and distribution of the bones and inside the body that's it thank you and let me know if you have any question it's made of the poly metal acrylic PMMA is a special composition which is compatible to the body and when we can injected that inside the bone the bone can tolerate them and won't reject that no it's used for medical procedure when somebody had fracture in his or her vertebra they can inject this type of cement inside the vertebra and it recovers the height of the vertebra and can goes to regular or normal activity for failure each type of the each actually position or each material inside the vertebra has its own ultimate strength and we define this criteria in analysis if the amount of the stress reach to that level it fracture and it goes out of the analysis yes so you were showing the final element model for that segment spine and then the build-in bone augmented moderate have you guys done any simulation along the entire spine to show how that segment acts with the full load on it or do you simulate the additional load from any point above yes yes it the full analysis of the spine showed that it the rigidity of a spine increase and the load tolerance changed and it's some and we have another fracture on the vicinity or neighbor neighbor vertebra inside the spinal column yes no I didn't do that but yes there is a special area or zone around the bone cement and the bone which actually has nothing inside that how do you extract each foxels material property from a given let me show you we extracted the material property based on the bone mineral density each bone mineral density has it's actually we have some equation which converts the bone mineral density to mechanical property we use this distribution for that reason for the material properties what's have you checked the sensitivity for example to use a homogenous material property throughout versus different material properties for each element see seems to me when we did this work it was not that sensitive to the variation of defining each material with different material properties only becomes important when we talk about the cortical bone versus the spongy bone because the material properties between the two is significant let me show you this actually this analysis shows the sensitivity of the material property of the model to the material property because you know the ultimate strength of the of this type of bone here should be more than five thousand meter but as you can see depending on the heterogeneity of the material here with the lower amount of the force we have some fade region which it showed that it's dependent on the heterogeneous of the material property on this graph the difference between this graph and the e-graph there's a basically a shift of close to two millimeter I would think that's just basically an experiment to do any noise because when you apply the load it takes a while for the specimen to capture that load but you capture it right away because of what I said the two graphs that shift I like that shift but that too many ways yes you are right just make sure that we are absolutely right here it shows that we have more displacement and it's because of this rubber which puts on the top and bottom of the vertebra to simulate the intervertebral disc and so when we start applying the compression load it takes a lot to reach the one structure to sense the load so this is this shift the load displacement to this position all right questions let's thank Dr. Ramchuk