Abstract:A model of effect of dynamical variation of tissue pressure on exchange between capillary and tissue has been presented in this paper. Filtration rate FR filtration factor FF and apparent viscosity μ of blood in capillary were got by using numerical calculation and compared with those in static condition. The results showed these important parameters varied dynamically with dynamical variation of tissue pressure. In general static condition blood apparent viscosity will increase along capillary tube then keeps in a higher level but in dynamic condition blood apparent viscosity will keep in a lower level not rise during some phase just if amplitude of dynamical variation of tissue pressure is in a suitable range. This is a reasonable explanation for Hemodynamics Mechanism of Chinese massage "huoxuehuayu".

Abstract:Objective to investigate the mechanical properties of the bioabsorbable solid-state compression reinforced high strength poly-L-lactide (SC-PLLA) material in vivo Methods SC-PLLA rods (3.2mm×30mm) were made by a special heating compression - the solid-state compression process. The morphological properties and the mechanical strengths (bending and shear strength) of the rods were investigated succesivly after the rods were implanted in rabbits subcutanously and in bone. Results Tuenty-four weeks after implantation the bending and shear strength of SC PLLA rods remained above 180 Mpa and 75Mpa respectively. They were higher than the strength of human cortical bone. The shear strength decreased faster than the bending strength. Under the scanning electron microscope numerous ordered fibers could be seen longitudinal to the axis of the rod inside the SC-PLLA material. After implantation the fibers could be degraded with time and the material become porotic. Conclusion Solid-compression process could obtain high initial and retention strength PLLA which could fit for the general bone internal fixation. SC-PLLA is a promising bioabsorbable osteosynthetic material.

Abstract:Simplifying the complicated structure of the cancellous bone so as to get a regular cube-frame of geometry and utilizing the equivalent element channel a physical model which takes accounts of effects coming from the surface friction drag between fluid(such as marrow etc.) and solid medium was proposed. A relation between pressure gradient and velocity for the liquid flow through porous media was formulated. Thereby the expression predicting the permeability k of cancellous bone was derived by the cube-frame. Measurement of k has been made in a special apparatus. The results show that the theoretical predictions based on the model presented in this paper agree with the experiment values and provide corresponding data of the penetrability for the application of the mechanics behavior study about cancellous bone.

Abstract:The analytical results on the quasi-linear viscoelastic constitutive equation under the periodic loading showed that the equation could not describe the experimental results of soft tissues. And based on the discussion on the single-integral constitutive relations a new constitutive form of soft tissues was provided which could describe more mechanical behaviors of soft tissues.

Abstract:In this paper the quantification method on the fracture treatment progress by inventing and applying the deformation transducer of the bone threading pins (ZL00201477.7) was introduced. The aim of this biomechanical research is to detect the motion of fractured site during healing thus make the fracture treatment method with reduction fixator applied more effectively.

Abstract:Objectives To study the mechanical behavior of the posterior longitudinal ligament (PLL) to retropulsed fragment in spinal canal in different conditions of thoracolumber burst fracture. Methods 5 fresh human thoracolumber spine were tested in following conditions intact specimen injury specimen with lordosis injury specimen with lordosis and axial distraction injury specimen with kyphosis injury specimen with kyphosis and axial distraction. A probe containing a strain gauge tip was mimicked as a retropulsed fragment by passing through L1 body tunnel which was created previously to press PLL in different deepness. Results The indirect reduction strength of PLL without axial distraction was less than with axial distraction (p<0.05). There was not a significant difference statistically between lordosis and kyphosis after axial distraction.There was a good correlation between the degree of canal encroachment and indirect reduction strength of PLL. conclusions Regardless of the sagital plane angulation of the injuried spine the indirect reduction strength of retropulsed fragment in spinal canal by tension of PLL is mainly affected by axial distraction force It is importment to use the distraction device in management thoracolumber burst fracture in order to achieve indirect reduction of retropulsed fragment in spinal canal.

Abstract:Purpose To analyze the stress distribution of prosthesis with different materials after replacement. Method Three-dimensional finite-element analysis was used to analyze the stress distributon when the prosthesis were loaded in the static and walking state after the replacement of composite material prosthesis and CoCrMo alloy prosthesis respectively. Result When loaded CRF/PSF Group received 85%～98% of the stress while CoCrMo Group only received 50% the surface stress of the prosthesis was only 10% for the CRF/PSF Group and 50% for the latter. Conclusion Low elastic CRF/PSF composite prosthesis can significantly reduce stress shielding and concentration have high anti-fatigue strength and reach better mechanical compatibility.

Abstract:Objective To test the mechanical property of Small Intestinal Submucosa. Methods The mechanical property of SIS were tested by SHIMADZU AG20KNA material test machine. Results Group A Stress of yield point is 7.72±0.70MPA strain is 42.66±14.69% Group B Stress of yield point is 7.57±1.94MPA strain is 42.34±8.29% Group C Stress of yield point is 3.91±0.91MPA strain is 71.59±3.64%. Conclusion The shape of load-extension diagram of SIS is just like that of collagen. The yield point stress of SIS is one seventh to fourteenth to that of the ligament and tendon. SIS exhibited an anisotropic mechanical property. Both yield point and max stress of SIS in longitudinal direction are nearly twice bigger than those in circumferential direction. The yield point and max strain in circumferential direction are more than 70%.

Abstract:Objective To compare the biomechanical properties of two different fixation. Methods Fourteen cadaver femure were used in the study. complete fractures of femoral necks were induced with Pauwel＇s angle more than 70 degrees and divided into two groups rendomly which were fixed by cannulated screw fixation with two different geometric contiguration of positive or negative triangle respectively. The biomechanical properties of two different fixation were evaluated. Results Main mechanical properties in negative triangle group such as tensile strain compressive strain displacement of femoral head (except horizontal displacement) axial and lateral rigidity ultimate load and yielding limit were significantly better than in positive triangle group (p<0.05). Conclusion Through biomechamal test we concluded that negative triangular internal fixation were better conformed to biomechanical demanded of fixation of femoral neck fracture than positive triangle group.

Abstract:Three dimensions finite element model of lumbar inter-body fusion was established to analyse internal biomechanical responses of lumbar inter-body. Single inter vertebrae fusion was performed and fixed with pedicle screw then we observed stresses distribution of lumbar and analysed degeneration mechanism of the neighboring inter-vertebrae joints. The study provided some information on the design and application of spinal internal fixation devices. At the same time we indroduced a model on studies of the lumbar fusion and fixation.

Abstract:Objective Quantitative biomechanical compairson of different internal fixation methods for distal femoral fractures provides theoretical basis for clinic curing. Method Performing theoretical and experimental stress analysis for fixing Y type femora fracture by using three different internal fixation methods. Results Under the same load condition Intramedullary supracondylar nail method is the best while for comprssed plate method the femoral condyle strength and origidity is worse (P<0.05). Conclusion Intramedullary Supracondylar nail Method is the best method among different internal fixation methods. It deserves to be put into application and populatization.

Abstract:To evaluate the biomechanical differences of Hydroxyapatite-Polyethylene composite coating and uncoated Ti-alloy implants. Methods The canine transcortical implant model was utilized At the end of the implantation periods push-out tests were carried out to acquire bone-coating interface shear strength of hydroxyapatite-polyethylene coating with uncoated Ti-alloy implants as control. Results The hydroxyapatite-polyethylene coating in every group showed greater shear strengths than uncoated implants being 3-5 times as much. The difference was significant statistically. (P<0.01) The strength increased with time reached the peak value at 12 weeks. Conclusions The interface shear strength of hydroxyapatite-polyethylene composite coating was much greater than that of the uncoated implants the results have revealed its good biomechanical characteristics which provided an effective method of biological fixation.