ABSTRACT
Objective To establish a 3D finite element model of cervicothoracic spinal segments C5-T2 based on CT images and test its validity and effectiveness. Methods By using the Mimics, Geomagic and Hypermesh software, the 3D model of cervicothoracic spinal segments C5-T2 was reconstructed, repaired and pre-processed. Moment of ±0.5, 1, 1.5, 2 N•m were applied on top of the model to simulate loads produced during the flexion and extension movement of human body. The range of motion (ROM) of the segments C5-T2 during flexion and extension was calculated by ANSYS, and the reliability of the model was verified by comparing the experimental results in the previous literature with the finite element analysis results obtained in this study. Results Under the moment of 1 N•m, the ROMs of C5-6, C6-7, C7-T1 and T1-2 during flexion were 4.30°,3.21°,1.66° and 1.41°, and those during extension were 3.47°, 2.86°, 0.96° and 0.92°, respectively. The maximum stress during flexion appeared on the front of the vertebral body, while that during extension appeared on the back of the vertebral body. The trends of ROM and stress distributions were consistent with results reported in the previous literature. Conclusions The 3D model established in this study is accurate and realistic, and conforms to biomechanical properties of the cervicothoracic spine. The simulation results can be further used to explore clinical pathology of the spine and provide theoretical references for evaluation on cervicothoracic spine surgery.
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Traditional Chinese medicine (TCM) has been formed and developed in medical practices over thousands of years, while biomechanics as a new research direction in TCM has been developing rapidly in recent years. Biomechanics in TCM encompasses abundant contents, such as hemodynamics in meridians, substance transport of Yin-Yang and the Five Elements, hemodynamics of pulse manifestation, heat conduction in tongue diagnosis, biomechanics of orthopaedics and traumatology, mechanics of acupuncture, massage and manipulation, TCM medical device, biomechnopharmacology and etc. Journal of Medical Biomechanics has published some papers about TCM biomechanics in the past years, and in this issue, a special column of TCM biomechanics in three research directions is organized, including massage and manipulation, fracture fixator by TCM treatment, and Tai Chi Quan, so as to arouse readers’ interest in TCM biomechanics.
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Objective To make a quantitative research on the vertical force homogeneity of Yizhichan manipulation and look for the quantitative index and reference value which can describe the force homogeneity of Yizhichan manipulation effectively. Methods After the force homogeneity was described mathematically, the vertical force signals from Yizhichan manipulation operated by 5 experts, 5 skilled doctors and 5 beginners were measured and analyzed, respectively. Results The period homogeneities and the waveform homogeneities were obtained. No significant differences were found in the period homogeneities among the three groups, but significant differences appeared in waveform homogeneities between the beginner and expert group or the beginner and skilled doctor group. Conclusions The waveform homogeneities are more suitable for evaluating the vertical force homogeneity of Yizhichan manipulation by different operators, and 0.927 can be used as a reference value to evaluate the vertical force homogeneity of the operator.
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Objective To raise a quantitative indicator for the waveform similarity between different signals of the same kind and apply it to the analysis on the vertical force signals from the rolling manipulation. Method After two signals of the same kind were normalized and their waveform errors were analyzed, the waveform similarity, which was to be utilized to describe the extent to which two signals were similar to each other, was defined. Then, the vertical force signals of the rolling manipulation operated by several experts, graduates who have learned the manipulation for some time and beginners were measured, respectively. Subsequently, the values of the waveform similarity between the three different groups of signals were calculated. Results The similarity between the experts’ signals was relatively high, so it was reasonable to be used as a template for other operators’ signals to be compared with. Further calculation revealed that the waveform similarity between the experts’ signals and the graduates’ was generally lower than that between the experts’, and the similarity between the experts’ and the beginners’ was the lowest. There was significant difference between the three groups. Conclusions The waveform similarity raised in this paper could serve as a quantitative indicator for the similarity between different vertical force signals from the rolling manipulation, and this method was also applicable to the similarity evaluation between other approximate periodic signals.
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Objective To numerically simulate the blood flow in myocardial bridging parietal coronary artery and investigate the hemodynamics mechanism of the fact that atherosclerosis is more likely to occur in proximal segment of the parietal coronary artery. Methods The model, a straight tube with local stenosis which moved along with heart beating being used in order to simulate the morphology of myocardial bridging parietal coronary artery, was established. The wall of the tube was assumed as a thin wall linear elastomer, and the blood flow was assumed as a series of one dimensional flow equations following incompressible Newtonian fluid. The Lax-Wendroff method was also adopted to solve the governing equations numerically. Results There were significant differences in blood flow, wall shear stress and wall shear stress gradient between parietal coronary artery and normal coronary artery. For parietal coronary artery, the changes of wall shear stress and wall shear stress gradient were more dramatic in proximal segment than those in distal segment. As for two myocardial bridgings in one coronary artery, the trend of the wall shear stress and wall shear stress gradient was essentially the same, but the wall shear stress and wall shear stress gradient in myocardial bridging far from the ventricle were larger than those in myocardial bridging near the ventricle, with a more dramatic change along the time during one cardiac cycle. Conclusions Simulation results indicate that hemodynamics of parietal coronary artery is different from that of normal coronary artery. Changes of wall shear stress and wall shear stress gradient are more dramatic in proximal segment than those in distal segment, thus having an important impact on the local endothelial cells. It might be the hemodynamic mechanism of the fact that atherosclerosis is more likely to be developed in proximal segment of parietal coronary artery.
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Objective To analyze the energy of rolling manipulation in different frequency bands and find the features of rolling manipulation dynamics. MethodThe force signals of rolling manipulation of six experts and six beginners were measured and divided into different frequency bands by wavelet transform to calculate the energy. Through statistical analysis, 18 characteristic quantities of horizontal force or vertical force were created and the overall evaluation coefficient R was proposed. ResultsAbout 70% of experts’ rolling manipulation energy was found in 0~0.406 25 Hz and about 20% energy in 1.625~3.25 Hz. The overall evaluation coefficient R of 6 experts was over 0.70, while R of beginners was below 0.70, which showed the difference was significant. ConclusionsThe energy distribution of rolling manipulation reflects the characteristics of softness and periodicity. If the rolling manipulation is in accordance with the manipulative requirement and the overall evaluation coefficients R is over 0.70, it could be said that the operator masters the rolling manipulation well.
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Objective In order to provide a more realistic microvasculature model for the study on tumor hemodynamics and drug delivery, a simulated tumor microvascular network was developed by the technique of numerical simulation and post processing. Method We constructed a tumor microvascular model with host arteriole venule system, in which the variation in vascular branching and dimensions was taken into account. A sensitivity analysis was made for the parameters of the model to evaluate the adjustability of simulated results. The connectivity of the vascular network was tested to ensure the integrity of the network. The vascular network was smoothed afterwards to reduce flow resistance resulting from numerical networks. Results The simulated results are consistent with the characteristics of real tumor microvasculature, which show intact circulation, local adjustability, high network connectivity and smooth degree. Conclusions This study provid a numerical microvasculature model for the research on tumor hemodynamics, drug delivery and vascular targeted therapy.
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Objective To study the characteristics of micro environmental flow and the process of macromolecular drug delivery in solid tumor. Method3D models simulating tumor hemodynamics and drug delivery were developed. Microcirculation and concentration distribution of two macromolecular drugs in tumor were simulated. ResultsThe model successfully reflected abnormal tumor hemodynamics, which results in impeded drug delivery and uneven concentration distribution of the drug. The results also shows that the drug with lower molecular weight is more easy to spread in tumor and excrete with interstitial fluid flow. In contrast, the drug with higher molecular weight tends to accumulate and maintain an effective concentration in tumor for a longer period. ConclusionsThe results derive from this model can reflect physiological conditions, providing a reliable numerical model for the investigation of tumor micro environment, drug delivery and strategy of therapy.