• Volume 19,Issue 2,2004 Table of Contents
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    • Three-dimensional Numerical Simulation of Steady Flow at the Entrance of Curved Pipe

      2004, 19(2):65-68. DOI: 10.3871/j.1004-7220.2004.2.68.

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      Abstract:Objective To study steady flow characteristics at the entrance of curved pipe. Methods Three-dimensional numerical simulation was performed by finite volume method. Results The streamline,axial constant velocity lines in the cross-section,velocity profile along the diameter of the cross-section in symmetric plane,and the distribution of wall shear stress were calculated respectively.The calculated values of the velocity profile along the diameter of the cross-section were found to coincide fairly well with experimental results. Conclusion The outside wall of curved pipe was the region with high shear stress while the inside wall was the one with low shear stress, which might explained that the preferential region of atherosclerosis.

    • Effects of Mechanical Pressure on the Ultrastructure and the Aggrecan Synthesis in Mandibular Condylar Chondrocytes

      2004, 19(2):69-73. DOI: 10.3871/j.1004-7220.2004.2.73.

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      Abstract:Objective To investigate the change of the ultrastructure and the variation of synthesis in aggrecan,the main proteoglycan component of the cartilage matrix of mandibular condylar chondrocytes(MCC), under the mechanical pressure. Methods In vitro cultured MCC from two-week-old New Zealand rabbits were incubated under continuous pressure of 90 kPa for 60min,360min by hydraulic pressure controlled cellular strain unit.The ultrastructure of MCC was observed under transmission electron microscope(TEM).In situ hybridization method was used to test aggrecan mRNA expression in MCC. Results The appearance of MCC on TEM showed that the cells of the control developed in the normal way.After been pressed under 90kPa for 60min,the cells showed elongated and voluminous cellular processes with increasing aggrecan mRNA.When the pressure lasted to 360 min,some of the cells showed distinct sign of apotosis and the aggrecan mRNA decreased but still higher than that of the control. Conclusion Continuouspressure could cause changes on the ultrastructure and function of MCC.Pressure may be used to up-regulate the synthesis of aggrecan.

    • Numerical Simulation of Pulsating Blood Flow in the Aortic Arch with Tapered Angle

      2004, 19(2):74-78. DOI: 10.3871/j.1004-7220.2004.2.78.

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      Abstract:Objective To study the distributions of velocity and pressure of blood within the aortic arch under normal physiological pulsatile flow conditions in order to provide fundamental theories for the genesis of an arteriosclerosis and its prevention. Method By virtue of the CFD and the fundamental of hemodynamics,the paper gives numerical simulations and flow visualizations of pulsating blood flow in the aortic arch with a tapered angle. Results The distributions of velocity,pressure and path line for the blood flow of the aortic arch with a tapered angle are obtained as a function of time in the cardiac circle. Conclusion There are a lot of causes which result in the complications of pulsating blood flow in the aortic arch.The most important two causes among them are the tapered angle and the curvature of the aortic arch.

    • A Method to Study Young's Modulus of Zona Pellucida of Animal Oocytes

      2004, 19(2):79-83. DOI: 10.3871/j.1004-7220.2004.2.83.

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      Abstract:Objective To develop an reliable method to measure Young's modulus of zona pellucida of animal oocytes in a quasi-static statue. Method Elastic sphere model embracing incompresive liquid was adopted to study in vitro mechanical properties of zona pellucida of baffalo oocytes by using micropipette aspiration technique. Based on mechanical analysis, a formula was derived to calculate the Young's modulus of Zona Pellucida in a quasi-static statue. Results A total of 20 mature non-polus oocytes were evaluated within a rather large strain span at temperature of 24~26℃. Their mean Young's modulus E was 2.2×104 Pa, suggesting a good linear elastic property. Conclusion This study provided an effective method to measure elastic property of zona pellucida of animal oocytes.

    • An Experimental Study on Biomechanical Properties of Iris Tissue

      2004, 19(2):84-87. DOI: 10.3871/j.1004-7220.2004.2.87.

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      Abstract:Objective The biomechanical properties of iris tissues of both the rabbit and the human being have been measured with the method of the whole pressurrization developed by us, and with the method of stimulating the difference of pressure between anterior chamber and posterior chamber in eyes. Methods The pupils are sewn for being water-proof without altering its geometrical shape to make the iris into a part of the glomeration. Then, we impose pressure on the whole iris. Results The iris materials is visco-elastic. These properties are available for the first time. Furthermore, the results show that similarity in biomechanical properties existed between the rabbit iris and the human iris. Linear relation on the whole existed between the area modulus and the difference of pressure between anterior chamber and the posterior chamber in the eye. Under the same pressure difference the area modulus and the curvature radius of the human iris are a little less than those of the rabbit iris. Conclusion The results will be useful in explaining glaucoma and in estimating the Pupillary Blocking Force. Through proper adjustment the rabbit iris can be used as a substitute in studying the biomechanical properties of the human iris with great cost reduction.

    • FEA of Different Internal Fixations for Femoral Neck Fractures

      2004, 19(2):88-92. DOI: 10.3871/j.1004-7220.2004.2.92.

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      Abstract:Objective To investigate the effects of stress changes by using different internal fixation methods in femoral neck fracture in order to find out the most optimal one with sound biomechanical principles before clinical application. Methods Pro/ENGINEER software was used to create a solid model, which was subsequently input into ANSYS 5.7 to establish Finite Element Analysis (FEA) model. A femoral neck fracture with Pauwel's angle of 50° and fixed with a single screw was used to find out the best fixation angle with sound biomechanical principle. Different internal fixations with 2 or 3 screws were then used to find the one with best fixation quality at this best fixation angle. Results When fixation was made for single screw at 50°, all evaluated parameters reached their lowest value, which suggested the optimal screw fixation angle. When 2 or 3 screws were used for fixation, the fixation with two level ones revealed overall the most inferior mechanical stability; two vertically placed screws for fixation showed the lowest anti-torsional property; the fixation with two obliquely inserted screws or combination of three screws provided better mechanical stability. After balancing many factors and from the clinically practical point of view, Single screw fixation was found to be technically simple and also provided reasonable good fixation effects. Conclusion Results of FEA analysis suggested that the difference in screw fixation angles and in way of combined use of screws might have important influence on biomechanical stability of femoral neck fracture fixation.

    • Biomechanical Evaluation of S_1 Screw and Rod-Plate Internal Fixation Developed for Fixation of Pelvic Fracture

      2004, 19(2):93-97. DOI: 10.3871/j.1004-7220.2004.2.97.

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      Abstract:Objective To evaluate biomechanical properties of a S 1 pedicle screw and rod-plate internal fixation developed by author for fixation of vertically unstable pelvic fracture and therefore to provide scientific foundations before clinical application. Methods Twenty fresh frozen cadavaric pelvis were used to create C 1-3 pelvic fracture (Tile classification). The fracture was fixed by using S 1 pedicle screws and rod-plate internal fixation, S 1 pedicle screw and Galveston technique, transiliac rod fixation, iliosacral screw fixation, and reconstruction plate, respectively. The mechanical stability of these five different internal fixation approaches was compared by using stress analysis method. Results Under the same load condition, the strength, rigidity and stability of S 1 pedicle screw and rod-plate internal fixation showed significantly better results than other methods and there was no statistical difference when compared with the result of intact control ( P <0.05). Conclusion S1 pedicle screw and rod-plate internal fixation was a better internal fixation approach as compared with other tested ones, which implied a new fixation method for potential clinical application.

    • Biomechanical Evaluation of an Expansive Pedicle Screw in Calf Vertebrae

      2004, 19(2):98-102. DOI: 10.3871/j.1004-7220.2004.2.102.

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      Abstract:Objective To measure and compare the pullout strength of newly-designed expansive pedicle screws with that of USS,Tenor,and CDH pedicle screws in calf lumber spine, and to evaluate the screw purchase of EPS screws. Methods Sixty fresh calf lumber vertebrae harvested from 12 calf lumber spine were randomly divided into 3 groups, i.e. 40 pedicles from 20 vertebrae for each group. EPS screws were randomly inserted into one side of pedicles of all vertebrae, while USS, Tenor and CDH screws were inserted into the opposite pedicles for pullout test, respectively. The maximum axial pullout strength was used for comparison. Results The maximum axial pullout strength of the EPS, USS, Tenor and CDH screws were 2658.4N±816.7N,1929.9N±484.9N,1849.8N±575.9N and 1980.9N±836.4N, respectively. The maximum axial pullout strength of EPS screws was statistically significantly greater than that of USS, Tenor and CDH screws ( P <0.01). Conclusions Results suggested that as compared with USS, Tenor and CDH screws, the expansive pedicle screws might have better fixation effects.

    • BiomechanicsAnalysisofCatagmaticHumerusFixedwithMemory-Compressive-Connector

      2004, 19(2):103-107. DOI: 10.3871/j.1004-7220.2004.2.107.

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      Abstract:Objective This study is designed to analysis circumstance that connector provdes for humerus,to analysis stress interfere when the connector is applied to humerus cure,and fo analysis stress enviroment according to bone-remodeling. Methods Three dimensional finite element methods is applied to calculats three-dimensional-finite-element model of humerus and connector. Resuls The section of catagmatic humerus always gets three dimensional stress.Shear stress cannot lead destruction of humerus.The bone produces very little distortion.Connector has four sections in which the strain reachs higher value. Conclusion Because of providing continuing stress,connector cannot bring interfere for loads.This improves stress activation for humerus.

    • A Biomechanical in vitro Study of Parachute-Like and Through-Calcaneus Suture Combination for the Repair of Rabbit Achilles Tendon Rupture

      2004, 19(2):108-111. DOI: 10.3871/j.1004-7220.2004.2.111.

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      Abstract:Objective To evaluate the mechanical property of a new parachute-like and through-calcaneus suture combination technique for the repair of Achilles tendon rupture. Methods Eight Achilles tendons each respectively from eight New Zealand white rabbits were repaired by a new suture technique which combined the end-to-end suture method with 0/0 Poliglactin-910 and the cross-stitch epitenon suture method with 5/0 Poliglactin-910. After the suture, the rabbits were given 3-day immobilization cast and then 25 days of functional practice. The in vitro experimental study was conducted next. Results The experimental group achieved 90% of the biomechanical property of the intact group. Conclusion The tendon repair of the new combinatory technique allows early-mobilization which in turn improves the mechanical property of the repaired Achilles tendons.

    • A Study of Interface Biomechanical Properties Between Femora and Prosthesis

      2004, 19(2):112-116. DOI: 10.3871/j.1004-7220.2004.2.116.

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      Abstract:Objective: To analyze the interface biomechanical properties between femora and prosthesis. Methods Theory models of bending and torsion for non-homogeneous layer-like materials were used to quantify the stress distribution when the femora were loaded in single foot stance and stance from seating, both before and after the replacement of different prosthesis. Results As the material properties of interface were different between bone and prosthesis, the bigger the difference, the greater the stress was in the result in the interface of losing, stripping and damage. Difference in young's modulus of the different prosthesis resulted in different levels of stress shielding. Conclusion The prosthesis with composite materials significantly reduced stress shielding. The hydroxyapatite-coated prosthesis helped to reduce stress difference at bone and prosthesis interface.

    • A Preliminary Study on the Diagnostic Value of the Flow Velocity Gradients of Resistance for Airway Obstruction by Impluse Oscillometry

      2004, 19(2):117-119. DOI: 10.3871/j.1004-7220.2004.2.119.

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      Abstract:Objective To assess the diagnostic value of the flow velocity gradients of resistance(dR/dV') in treating airway obstruction using impluse oscillometry. Methods The dR/dV' value, FEV 1, V 50, and V 25 were measured and compared using 72 cases including control, smoking and COPD groups. The dR/dV' values were regressed with FEV 1, V 50 and V 25, respectively. Results Significantly different dR/dV' values were found between control and smoking groups and between control and COPD groups, but not between smoking and COPD groups. Significantly negative correlation was found between dR/dV' and FEV 1, and similarly, between dR/dV' and V 50 and between dR/dV' and V 25. If the dR/dV' value exceeded x ±1.65s it was considered abnormal, and the misdiagnosis rate was 4.17% in the normal group, while the positive rate reached 41.67% in 48 cases (smoking and COPD groups). Conclusion The dR/dV' is considered an index for detecting airway obstruction, but is not accurate in reflecting the severity of the disease.

    • Advanced in Biomechanics of Patella

      2004, 19(2):120-125. DOI: 10.3871/j.1004-7220.2004.2.125.

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      Abstract:髌骨的生物力学是近年来研究的热点之一 ,髌股关节之间的运动十分复杂 ,对合不良被认为和膝前痛密切相关。作者从髌骨在伸膝机制中的作用、髌骨软骨的特性与髌股关节活动的匹配性、髌股关节面在伸屈膝过程中的接触区域变化、髌股关节作用力和压应力、髌骨的运动轨迹五个方面阐述近年来的一些研究进展 ,并分析了一些问题、挑战和前景。

    • Biomechanics of Spinal Cord and Spinal Cord Injuries

      2004, 19(2):126-128. DOI: 10.3871/j.1004-7220.2004.2.128.

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      Abstract:脊髓及脊髓损伤的生物力学研究有助于我们认识损伤机制 ,理解损伤的临床病理结果 ,进一步指导预防、治疗。作者重点对脊髓 (包括灰白质、脑脊液、齿状韧带、软膜、硬脊膜 )的力学特性及脊髓损伤力学研究中的动物模型 (包括撞击损伤模型、压迫损伤模型 )和有限元模型进行了综述 ,并对近年脊髓损伤在细胞水平的生物力学研究作了简要介绍。

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