Establishment of Three-Dimensional Finite Element Model of Medulla Oblongata-Upper Cervical Spinal Cord Based on Pathological Section and Biomechanical Analysis of Related Injury / 医用生物力学

Objective The three-dimensional (3D) solid model of medulla oblongata-upper cervical spinal cord based on specimen pathological section data was established, and the stress and strain levels of medulla oblongata-upper cervical spinal cord under dentate process compression were obtained by finite element analysis, so as to provide references for clinical research. Methods Mimics was used to process the slice data, so as to establish the point cloud model. SolidWorks was used to locate, edit and optimize the point cloud model, so as to establish the 3D solid model. HyperMesh was used to establish the finite element model and ANSYS was used for finite element analysis. Results The medulla oblongata-upper cervical spinal cord model with clear boundary between gray matter and white matter and white matter fiber bundle was established. The stress and strain levels and stress-strain curves of white matter and gray matter under different compression degrees were obtained. Conclusions Combined with pathological sections of specimens and reverse engineering, the 3D medulla oblongata-upper cervical spinal cord model with clear morphology and structure of gray/white matter can be established. When the medulla oblongata-upper cervical spinal cord is compressed, the stress level of gray matter is lower than that of white matter, and about 20% of compression is the critical state of white matter. When the disease develops beyond the critical state, the biomechanical properties of white matter may fail, resulting in gray matter damage.

The biomechanical analysis of craniovertebral junction finite element model in atlas assimilation / 中华外科杂志

<p><b>OBJECTIVE</b>To study the biomechanical change of the craniovertebral junction in conditions of atlas assimilation.</p><p><b>METHODS</b>Mimics software was used to process CT data of the craniovertebral junction in a health adult to obtain the three-dimensional reconstruction and the cloudy points of C1, C2 and part of the occipital bone. Then the cloudy points were imported into the Abaqus 6. 8 software to establish the occipito-atlantoaxial finite element model in normal structure. According to the established model in normal structure, the model in conditions of atlas assimilation was set by changing the model parameters. Both models of normal structure and atlas assimilation were loaded with 1. 5 N . m static moment to simulate four motions of flexion, extension, lateral bending and axial rotation respectively. The movement characteristics,joint stress force and ligament deformation was analyzed.</p><p><b>RESULTS</b>Under 1. 5 N . m moment, in model of atlas assimilation the C1-C2 range of movement decreased from 13. 55° to 11.88° in flexion,increased from 13. 22° to 15. 24° in extension and from 4. 05° to 4. 23° in lateral bending and remained unchanged in axial rotation when compared with the normal model. In flexion movement, the contact force of the atlanto-dental joint increased from 1. 59 MPa to 3. 28 MPa and the deflection of apical ligament, tectorial membrane and alar ligament increased 129. 1%, 157. 6% and 75. 1% respectively when compared with the normal model.</p><p><b>CONCLUSIONS</b>The normal C1-C2 motion mode is destructed in conditions of atlas assimilation, leading to the changes of the range of movement,joint stress force and the ligament deformation at C1 C2 junction. The atlantoaxial instability will likely occur in flexion motion.</p>

Research on biomechanics properties of occipito-atlantoaxial complex by finite element method / 生物医学工程学杂志

Based on the research history of the biomechanics of occipito-atlantoaxial complex, we have systematically summarized the use of finite element method for studying biomechanics of occipito-atlantoaxial complex. Then, combined with four basic principles of establishing an effective finite element model for mechanics, our comments are focused on the establishment of geometrical model, finite element model, finite element mechanics model, and on the method and implementation for validating the model. In addition, the developing trends, existing problems and future researching directions in this area are discussed.

Differentiation of human embryonic stem cells into cardiomyocytes in vitro / 中国组织工程研究

BACKGROUND: Differentiation of embryonic stem (ES) cells into cardiomyocytes in vitro has been studied in great detail in the world. However, much of what is currently known about cardiomyocyte differentiation from ES cells has been learned from studies on mouse in China, few studies are on human ES cells.OB JECTIVE: To investigate the differentiation effcacy of human ES cells into functional cardiomycytes with the human H14 ES cell line.DESIGN: Suspending method was used to form pseudo-embryo proper of human ES cells so as to observe ratio of pseudo-embryo proper with rhythmic contraction and expression of specific gene of myocardium in various differentiated phases.SETTING: Molecular Biology Laboratory of Stanley Ho Center for Emerging Infectious Diseases, School of Public Health, the Chinese University of Hong Kong.MATERIALS: Human ES cell line H14 was obtained from WiCell Research Institute (Wisconsin, USA) with a license agreement.METHODS: The experiments were carried out in the Molecular Biology Laboratory of Stanley Ho Center for Emerging Infectious Diseases, School of Public Health, the Chinese University of Hong Kong from August to December of 2006.The H14 ES cell colony was used to form embryoid bodies (EBs) by using suspending method. Four days later,pseudo-embryo proper was cultured in gelatin-coating 6-well culture plate (5-10 embryo proper/well) and spontaneously differentiated into moving pseudo-embryo proper. Rhythmic contraction was observed under microscope and RT-PCR was used to detect expression of special genes of myocardium.MAIN OUTCOME MEASURES: Ratio of pseudo-embryo proper with rhythmic contraction and expression of specific gene of myocardium in various differentiated phasesRESULTS: Spontaneously contracting cells appeared as cluster and were identified in approximately 2% of EBs at differentiation day 8 and increased to as many as 10% of the EBs by day 16. The beating rate of contracting cells arranged at 70-100 beats per minute. RT-PCR analyses demonstrated that cells isolated from spontaneous beating areas within the EB expressed the cardiac transcription factors GATA-4 and Nkx2.5, cardiac progenitor gene Isl-1 and cardiomyocyte marker gene α-MHC.CONCLUSION: This is the first time to report human ES cells can effectively differentiate into functional cardiomyocytes in China.