Abstract:Objeclive To understand the effects of the arterial size on the hemodynamics of S-shaped arteries. Method Numerical simulation method was applied to analyze the temporal and spatial distributions of hemodynamic variables in bothlarge and small S-shaped arterial models with different arterial diameters under identical boundary conditions, respectively. Result The secondary flow in the large S-shaped artery is more complex than that in the small one; stronger eddy flow occurred in the inner bends of curved arteries; pressure and wall shear stresses changed violently in the curved arteries, especially in the larger model. Conclusion The hemodynamics of S-shaped arteries may affect the function of arterial endothelium, and result in the thickening of the intima. It may be favorable to avoid using the S-shaped artery in operations to correct or bypass arterial stenosis when utilizing prosthetic or autologous vessels.

Abstract:Objective To investigate tumor-induced angiogenesis under the influence posed by the mechanical environments in and out of tumor, and simulate the capillary network numerically. Methods The tissue in and out of tumor is assumed to be linear visco-elastic. The diffusive coefficient of endothelia-cell (EC) keeps constant in normal tissue out of tumor. In tumor, the reduced activity of tumor cells becomes a big obstacle for EC's movement, the coefficient is supposed to be a power function along the distance from the tumor center. An equation for EC movement is established in this model to illustrate the mechanical effect. The capillary network is simulated numerically. Results A relatively realistic capillary network in and out of tumor is gained. The mechanical factor results a layered structure: at the edge of tumor, numerous capillaries are generated, while closer to the tumor center, less the capillary. A Necrotic Region without any vessel exists in the center. However, the model can not generate a layered network without considering the mechanical effect. Conclusion Different mechanical environments in and out of tumor play an important role in the process of tumor-induced angiogenesis.

Abstract:Objective To study hemodynamics in 3D microvascular networks and interstitium of solid tumor by numerical method. Methods Generate 3D vascular networks of solid tumor numerically; calculate intravascular pressure、interstitial pressure and velocity by Poiseuille's law and Darcy's law, respectively. Results To vessels outside tumor, blood pressure drops rapidly, but to vessels inside tumor, it changes a little which could be assumed constant; interstitial pressure of tumor is high and plain in the center region and drops rapidly in the edge, which is reverse for interstitial fluid velocity. Conclusion An effective 3D vascular networks inside and outside of tumor was obtained; the results of hemodynamics consist with basic physiological features, and provide a credible model and method for research about drug delivery in tumor.

Abstract:Objective To study the effect of anisotropic hydraulic conductivity coefficient on interstitial fluid flow in solid tumor. Methods 2-D Microvascular networks model with neoplastic microvascular morphometric and topological characteristic is built based on image manipulation. The interstitial fluid flow in connected multi-domains to account for the effect of variations hydraulic conductivity coefficient was calculated by using boundary element method. Results The difference of hydraulic conductivity coefficient between horizontal and vertical has a striking effect on the distributions of interstitial fluid pressure (IFP) in the whole tumor. Different function forms of hydraulic conductivity coefficient influence the distributions of IFP in the local region of the tumor. Conclusion Effect of anisotropic hydraulic conductivity coefficient on IFP relates to both of the various range of hydraulic conductivity coefficient and the morphology of microvascular networks.

Abstract:Objective To investigate the effect of physiology parameter and drug injection-methods on drug delivery in solid tumor. Methods The distributing of the tumor vascular is sphere-symmetry, and the surface areas per unite volume for blood vessels is a function of radius. The tumor interstitium is considered as porous medium and drug could pass through the microvascular into it. The drug in tumor interstitium is transported by diffusion. The interstitium of normal tissue contain vessels and lymphatic, and the drug can be absorbed by lymphatic. In the normal tissue an advanced pharmacokinetic model is considered. The area under the curve (AUC) of drug concentration which is higher than minimum effective concentration (MEC) in tumor during 24 hours is used to evaluate the treatment of drug. Results Increasing vascular permeability coefficient P and the drug diffusion coefficient D, AUC will increase. In the six injection-methods, injecting by continuing-dropping in separated time periods or bolus injection in several times with the same interval could obtain the highest AUC. Conclusion Increasing vascular permeability coefficient, raising the drug diffusion coefficient, and injecting by continuing-dropping in separated time periods or bolus injection in several times with the same interval are more useful for treatment of tumor.

Abstract:Objective To explore the impact of stress and inhibitor on avascular tumor growth. Methods A two-phase model, including the tumor cell and the extra-cellular interstitium is presented to describe avascular tumor growth. The diffusion of nutrients gives rise to the cellular growth while metabolism and inhibitor released by tumor cell itself accelerate the death rate. The continuum equation for tumor cell and the diffusion equation for nutrients and inhibitor are established. Given the interaction between the two phases, equations of momentum conservation are gained. With the constitutive relationship of each phase, the final coupled equations are linked together and numerical results are obtained. Results The tension of nutrients declines as time goes by, with lower value in the central area compared with its surrounding. Much more inhibitors are absorbed by the central area than its edge. Given the inhibitor and stress of each phase, the out-ring area of tumor shows more potential to grow and the central area tends to be dormant. The whole tumor tends to grow actively if inhibitors are neglected. Conclusion The existence of inhibitor is essential for the formation of necrosis. The stress of tumor cell phase drives the tumor to grow outside so that the high stress could be relieved.

Abstract:Objective To study the tumor-immune model under the heterogeneous blood perfusion caused by the nonhomogeneity of vessel distribution. Methods Assume the distribution of blood perfusion to be quadratic along radius axis and adapt parameters accordingly. Solve the model given by Costa et al and compare with their result. Results The tumor-immune competition various obviously among different locations. The growth stagnates in the nuclear region, but acquires monotonous or periodical uncontrolled patterns in the outer layer of the core. Restriction of the tumor growth appears in the peripheral layer of the solid tumor. Conclusion The tumor-immune competition shows palpable discrepancy when taking into account the heterogeneity of blood perfusion.

Abstract:Objective This paper analyze the locomotion property of statocyst of marine mollusk Clione limacine. Method We used here are WLC model to study electric spike of neural system and to simulate Liapunov index of the spike neuron. Result The results show the Liapunov index of the neural electric spike appears negative in general situation and appears positive in special external stimulus. Conclusion The locomotion of statocyst of marine mollusk Clione limacine have different steady states and the two steady states can be change from chaos. This is the boundary of chaos property of motor systems of Clione.

Abstract:Objective A nonlinear finite element model was used for comparing stentless? pericardial mitral valve and stented? pericardial three-leaflet valve to identify their static stress distribution at valve open and closed position during cardiac cycle. Methods A finite element code was developed? by using the 8-node super-parameter nonlinear shells and the Newton-Raphson method. The load was the mean transvalvular? pressure gradient of the tested valves at open and closed position, and the stress was determined. Results At an internal pressure of l20mmHg in mitral valve closed position, stentless? pericardial mitral valve showed more reasonable stress distribution than that of stented? pericardial three-leaflet valve. The maximum first principle normal stress, of which the area corresponded with the perforation point, was 2.352MPa in stented pericardial three-leaflet valve. The average first principle normal stress of stented pericardial three-leaflet valve (0.223~0.724MPa) was higher than that of stentless pericardial mitral valve (0.040~0.l49Mpa). Conclusion A finite element analysis of the quadrileaflet? stentless mitral valve, whose geometry and action was nonlinear, was effective and feasible. It shows that for the stentless pericardial mitral valve, the absence of the stent resulted in reduced stress on the leaflets. It could bepostulated that this will lead to a decrease of tears, perforation and calcification, which may result in an improved long-term behavior.

Abstract:Objece Acetabular component failure has been proved to be the key factor affecting the long-term result of survival rate of TKR. Preparation of the acetabular for the component is the most important procedure for predicating the destiny of acetabular component. This study aimed to evaluate the side-effect of extensive concentric reaming for acetabular preparation in respect of bone loss of acetabulum rim and change of acetabular anteversion. Methods CT images of 40 normal adult bony acetabula were obtained and processed with the algorithm of histogram-threshold segmenting and Kirsh boundary detection to get a binary contour image. The contour of scanned acetabulum was then used for three-dimensional reconstruction with CAD software. With best-fit sphere of acetabulum bone joint surface technique, quantitative analyses have been done in computer imitating the concentric reaming for acetabulum. Two kinds of extensive concentric reaming for acetabular preparation were defined as reaming to the depth of reaching bottom of Harris forum or reaming until reaching the inner pelvic wall at medial side of acetabulum. Results (1) when it was done to the depth of reaching bottom of Harris forum, bone losses at anterior rim and posterior rim of acetabulum were estimated to average 6.75 mm and 6.11 mm respectively, and the acetabular anteversion was increased at upper half of acetabulum with maximum increase of 4.83°. (2) when it was done to the depth of reaching reaching the inner pelvic wall , bone losses at the anterior rim and posterior rim could reach to 9.54 mm and 9.56 mm thickness and acetabular anteversion at upper half of acetabulum further increased with maximum increase of 8.55°. Conclusion Although concentric reaming for acetabular would precisely maintain the normal hip kinematic center, extensive concentric reaming to the extent reaching or passing over the bottom of Harris forum could result in obvious bone losses at both anterior and posterior rims of acetabular bearing surface and alter the nature acetabular anteversion, which might compromise both the integration of acetabular component with bone surface and proper orientation of the component.

Abstract:Objective To Study the availability of manual reduction and the method of internal fixation in the treatment of anterior shoulder joint dislocation and proximal humeral fracture by percutaneous internal fixation. Methods To measure the force that pull tail-pressed angle-adjusted hollow screw out of the head of humerus (P(subscript min)) and the force that needed in the traction reduction of acute anterior dislocation of shoulder joint under local anesthesia (P(subscript max)). Stastical analysis has been made. Results When the screw put into the head of humerus 20 mm, P(subscript minA)=284 N, P(subscript minB)=l98 N; P(subscript maxA)=206 N, P(subscript maxB)=195 N. The act of comparing P (subscript min) with P(subscript max), P(subscript min) is more than P(subscript max) Traction force that needed by traction reduction of anterior dislocation of shoulder joint is less than the minimum force that pull tail-pressed angle-adjusted hollow screw out of humeral head. Conclusion Using tail-pressed angle-adjusted hollow screw can meet the need of percutaneous internal fixation in the treatment of proximal humeral fracture and anterior dislocation of shoulder joint.

Abstract:Objective: To investigate the biomechanical performance of a newly designed cervico-trochanteric stemless prosthesis by comparing the stres distribution with that of the traditional stem-type porous-coated anatomic prosthesis. Methods Using CT scanning photographs of real femur, three-dimensional finite element models were created for the intact, cervico-trochanteric (with two or three fixation screws), and porous-coated anatomic implanted femora with the geometry of a standardized real femur. Analysis was performed for a loading condition simulating the single-legged stance. The von Mises stress distributions of each model were analyzed and compared. Results The results can be summarized as follows: (1) Von Mises stress in the proximal, medial femur for the cervico-trochanteric implanted model was higher than that of the intact model and the porous-coated anatomic implanted model; (2) stress-shielding effect of the cervico-trochanteric models (with two or three fixation screws) were eliminated as compared with the porous-coated anatomic model; (3) no obvious difference in von Mises stress distribution for the cervico-trochanteric implanted model with two or three fixation screws. Conclusion The cervico-trochanteric femoral prosthesis may reduce the stress-shielding effect of the proximal femur and achievea more physiological stress distribution on the proximal femur than that of the porous-coated anatomic prosthesis.

Abstract:Objective To compare the stiffness, pull-out strength and energy absorption of two different sacroiliac screw fixation techniques under different loading conditions to determine the new fixation method more congruous with human biomechanics requirements. Methods Eight bone specimens of human pelvis of 23 to 45 year-old were used. No deformity, osteoporosis, tumor or trauma was found in all the specimens after gross anatomy, X-ray and BMD (bone material density) inspection. The eight pelvis were cut into halves and divided into two groups. Sixteen sacroiliac screws by using LX method were inserted into the left sides (Group one), the negative stress sacroiliac screw was inserted into the tension band of sacroiliac complex, the positive stress sacroiliac screw was inserted into the compression band. Eight ordinary sacroiliac screws were inserted into the right sides (Group two). The insertion torque, pull-out strength, relative migration, energy absorption ofeach screw were measured. Results The pull-out strength of the sacroiliac screws using LX method were higher than that of the ordinary sacroiliac screw (P<0.05). There exist obviously positive correlations between the insertion torque and the pull-out strength, the BMD and the pull-out strength, the BMD and the insertion torque (P<0.05). The energy absorption of the ordinary sacroiliac screws was higher than that of the pressure screws and the tension screws (P<0.05), but the total energy absorption was higher in the sacroiliac screws using LX method when compared with that of the ordinary sacroiliac screws (P<0.05). Conclusion The stiffness, pull-out strength and absorption energy of sacroiliac screws using LX method were biomechanically superior to that of ordinary sacroiliac screw. Therefore, the new sacroiliac screws fixation technique which is more congruous with human biomechanics requirements would be recommended for better stability of the reconstructed pelvis.

Abstract:Speckle metrology, which was created in 60's, is one of photomechanics in experimental mechanics. This method has hitherto been developed and applied widely in many engineering fields, including biomedical engineering. The author summarily explained the principle and characteristic of speckle metrology as well as the application of main speckle metrologies used in biomedical field, such as speckle photography、speckle interferometry、electronic speckle pattern interferometry、digital speckle correlation methodand bio-speckle method.i it's development in the future has also been introduced.

Abstract:Arthritic dislocation is the common postoperative complication of total hip arthroplasty and larger ball head could be one of the efficient means to deal with this problem. This article discussed the relationship between the diameter of ball head and wear of polyethylene, the experimental results of reducing the dislocation rate with larger ball head and the preliminary clinical consequence of hip arthroplasty using larger head.