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Human Finite Element Analysis in the Supine Position
Figure 1. Finite Element Model Included Soft Tissues and Spinal Core
This was a commissioned research project period of one year from the company of developing ergonomic mattress. The purpose of this study is to construct the different shape of finite element human model and investigate the effect on spinal alignment and stress distribution while altering hardness of mattress. I totally responsible for this project and my contribution to the research project included model development, simulation, coding and data analysis.
The spine is stabilized by the intervertebral discs themselves and the surrounding soft tissues such as the ligaments and muscles, which are prone to fatigue injuries under prolonged malpositioning. The humans spend about one-third of their lives lying on the bed. Thus, it is essential to maintain a good spinal alignment in the supine position. However, direct measurement of the forces in the body in vivo is possible only in exceptional circumstances. Owing to the varieties of back shapes and body figures across individuals, it is difficult to provide a subject-specific analysis to simulate the spine alignment while lying supine on the mattress.
Finite Element Model and Analysis
The study reconstructed an existing whole-body CT scan data for bone and Magnetic Resonance Imaging(MRI) for muscle, fat, and skin(Fig. 2) into a three-dimensional model. A generic whole body finite element model(Fig. 1) was built and each element was assigned a tissue by point-in-polyhedron tests. Secondly, to generate a subject-specific FE model, the study utilized Kinect to capture(Fig. 3) depth images which were stitched into subject’s whole body point cloud. Surface deformation from CT to subject’s model was determined by non-rigid registration (CPD). Inner tissue deformation was determined with kernel regression following CPD’s assumption. A subject-specific FE model was then created. Together with the mattress model formed in the software, the study has succeeded in analyzing spinal alignment during supine with validation.
Figure 2. Modeling from Magnetic Resonance Imaging
Figure 3. Kinect Capture System
Result and Discussion
All of the indicator including neck angle variation, pelvis angle variation and upper spine displacement is shown that we tremendously influenced by hardness mattress(Fig. 4).
Figure 4. Result of neck angle variation, pelvis angle variation and upper spine displacement
The concentration of the stress found in thigh part and the head part(Fig. 5). Moreover, we realized that the stiff mattress brings us the greater concentration than others.
Figure 5. Result of Stress Distribution
The study provided a three-dimensional customized process to spinal analysis without invasive technique or radiation. It was helpful to gain insight of spinal alignment during supine with different mattress for different people. The study would help to the development of mattress and the diagnosis of the spine.
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