Abstract:Objective To develop the experimental model for explosive blast under water and analysis its distribution characteristics. Methods Depending on the theoretic principle of explosive blast,the experimental model for explosive blast under water was established. The cultured endothelial cells were placed into special asepsis plastic bag to simulate the cell injury through electric exploder of 80mg. Results The reducing velocity of explosive blast in water is slower than in air.The height of the exploder in water had obvious influence on the pressure peak of explosive blast .From the same explosive source, the deeper the water,the smaller the pressure.Different covers with filter membrane have relation to the pressure by line reducing. There is obviously crimple and exfoliate of endothelial cells injury when covered by 8 membranes. Conclusion Transmission speed of explosive blast has relation to different medium, the pressure of explosive blast under water is not only related to the distance from explosive source, but also to the height of the water.

Abstract:Objective To Investigate the stress adaptability of freeze-dried bone allograft. Methods Cortical and cancellous allograft were transplanted to each side of the midshaft diaphyseal ulnar respectively in each group of 28 animals. The left transplanted allograft was free from fixaton and bear normal physiological load, while the right transplanted allograft was protected from loading by a simple external fixator and bear less load. Animals were killed in batch at 2nd, 4th, 8th, 16th week after transplantation and specimens were taken out for bone histomorphometry study and analysis of collagen gene expression by in situ cDNA-mRNA hybridization.Results Labeled surface(LS) and bone mineral apposition rate(MAR) of the normally loaded graft-host bone interface were significantly higher than that of the less loaded side at the 4th,8th,16th week after transplantation. The parameters reflecting the internal repair process of allograft such as LS in cortical and cancellous boen or MAR in cortical bone of the normally loaded side were significantly higher than that of the less loaded side at 16th week after transplantation. The result of in situ hybridization indicated that more osteoblast-like cells with expression of typeⅠcollagen gene occuring in the interface or interior of normally loaded graft. Conclusion The stimulus of physiologic load can accelerate the early union of allograft-host bone interface and later new bone creeping substitution to the necrotic allograft.

Abstract:Objective By evaluating quantitative biomechanical comparison of four internal fixation methods for distal femoral fractures, to choose suitable clinical internal fixation method according to the experimental data. Methods The models of fracture of femoral condyle were made on 16 fresh cadaver femurs (C1 of AO classification) and fixed by supracondylar intramedullary interlocking nail, dynamic condyle screw plate, L shaped condyle plate and Ender's nail fixation respectively. To compare the four different methods by experimental stress analysis and theoretical analysis of finite element method. Results Under the same load condition, the supracondylar intramedullary interlocking nail absorbed more energy during axial loading compared with the other constructs(P<0.01). The dynamic condyle screw plate had the greatest torsional stiffness (P<0.01). There were no significant differences in torsional stiffness between GSHN and DCS. Conclusion Using supracondylar intramdullary inter locking nail and the dynamic condyle screw plate are better than the other internal fixation methods and deserve to be put into clinical application and populatization.

Abstract:Objective The thoracolumbar vertebra fracture is usually treated by transpedicle screw fixation. Since its effects are correlated to such factors as the length and the implanted direction of screw ,BMD etc. This study was made to provide some biomechanical evidence for better clinical operation.Methods To take six cadaveric lumbar spines to undertake tests with experimental stress analysis.Results The strain of long screw compared with short ones,is respectively 16%, 41%, 56%, 41% lesser in compression,anterior flection,posterior extension and luteral flection;the strength is improved by 16%, 41%, 55% and 41%; the displecement of spine is lower by 18%, 25%, 32% and 30%;the axial rigidity is improved by 18%, 25%, 32% and 30%(P<0.05).The drawing strength of screw implanted in parallel direction is larger by 20% than screw implanted in 7° direction,while the drawing displacement increased by 7%,the energy increased by 18%(P<0.05). With regard to the bone density effect on drawing strength, the normal group is larger than osteoprotic group by 67%. There is average 16% difference in the relative displacement ,strain and energy.Conclusion The relative factors of the fixation that mentioned above should be caused attention in operation so that it can improve the operative quality and reduce complications.

Abstract:Objective To reveal the rule of the biomechanical remodeling of the aorta by studying zero?stress state of abdominal aorta in strepozotocin-induced diabetic and spontaneously hypertensive rats. Methods The animal model of diabetes with and without hypertension were made on SHR (SHRDM group) and SD (SDDM group) rats respectively by injection of streptozotocin. The opening angle (OA) of their abdominal aorta (AA) was studied by microscope and compare image analysis system.Results (1) OA of AA in SD group became bigger from 1st week to 4th week, and then turned smaller, after 8th weeks became stable. (2) OA in SDDM group increased rapidly from 1st week to 4th week, decreased greatly within 4th to 8th weeks, and increased rapidly again after 16th weeks. OA in SDDM group was smaller at 8th or 16th week (P<0.05) and bigger at 4th or 24th week (P<0.01) than that in SD group. (3) The tendency of OA in SHR group turned out contrary to that in SDDM group , which was bigger than that in SD group at 1st, 8th, 16th week (P<0.01) and smaller at 4th weeks (P<0.01). (4) The change of OA in SHRDM group was similar to that in SDDM group, but smaller at 4th week ( P<0.01 ) and bigger at 8th or 16th week (P<0.05) than SDDM group. Conclusions The zero-stress state of abdominal aorta was abnormal in diabetic and hypertensive rats. The contrary tendency of OA between diabetic and hypertensive groups at early stage suggests that there exsits un-uniform growth obviously in big artery wall of diabetes and hypertension, but the patterns are different.

Abstract:Objective To evaluate the efficacy of BSYJF on raising the quality of cortical bone of femur in osteoporotic rat model induced by ovariectomy and its mechanism on improving biomechanical properties of cortical bone. Method Forty female Wistar rats were divided randomizedly into four groups: Sham control group(GA), Ovx control group(GB), BSYJF group(Ovx+BSYJF,GC) and BML Group(Ovx+BML, GD). The time point of administering drug(BSYJF or BML) to the rats was 90 days after ovariectomy. The time point of sacrificing was 180 days later. After sacrificing, macroscopic geometry structure, bone mineral density and bionechanical properties of three-point bending (structural mechanical property and material mechanical property) of femur were determined. Results In GB, the dirmeter of medullary canal was enlarged significantly (P<0.05) and the thickness of cortical bone decreased significantly ( P <0.05), respectively vs GA; in GC and GD, there was no significant change of the diameter but the thickness of cortical bone all was enlarged olveously (P<0.05), respectively vs GB. The bone mineral density in GB were not decreased significantly as compared with GA also in GC compared with GB. In GB the parameters of structural mechanical property(maximum load. stiffness and energy) and the parameters of material mechanical property(maximum stress and elastic modulus) were decreased significantly (P<0.05), respectively compared with GA. Stiffness and elastic modulus in GC were increased significantly (P<0.05) but not in GD (P<0.05) and other parameters of mechanical properties in the two groups (GC and GD) were all increased sinificantly (P<0.05), respectively compared with GB. Conclusion BSYJF can raise the quality of cortical bone of femur in the rat model induced by ovariectomy. In improving biomechanical properties of cortical bone, BSYJF has the same partial mechanism, which can modify the macroscopic geometry structure of cortical bone as BML. But BSYJF has another different mechanism, which can up-regulate stiffness and elastic modulus of cortical bone without increasing bone mineral density.

Abstract:Objective To investigate the loading ability of improved U shaped plate. Methods To understand the bending and distorting ability of U shaped plate by experimental test of mechanics and to verify its theoretical calculation as well as comparison with general plate, AO plate and dynamic compression plate. Results The bending ability and the distorting ability of general plate adding a simple U shaped arm can be raised respectively by 22～37 percent and 50～105 percent. Compared with the same usage of AO plate and dynamic compression plate at sagittal face, the bending ability can also be raised respectively by 107.6 percent and 21.5 percent, and the distorting ability raised respectively by 406 percent and 58 percent of raised by 31.9 percent of distorting ability compare with CP DCP Conclusion U shaped bone plate is an eligible plate with enough strength, simple structure and less materials.

Abstract:Objective To determine the mechanical properties of the interlocking expanding compressive screw(HZS) to treat the femoral neck fracture and present the scientific data for its further clinical uses. Methods The models of femoral neck fracture were made in 8 cases of the fresh cadaveric human femurs. The fractures were reduced anatomically and fixed with the interlocking expanding compressive screw, dynamic compressive screw, twin compressive screw and three cannulated screws individually. Then the specimen were tested on the material machine. Results The models of HZS were strongest of all for against the compression, flexion, shearing and torsional force. The HZS has the good impact effect between the two fracture segments which could accelerate the bone healing. Conclusion The interlocking expanding compressive screw is a new kind of optimal fixator for the femoral neck fracture due to its superior mechanical properties to any other ones.

Abstract:The purpose of this paper is to investigate the effects of Chinese traditional medical management on the function and biomechanical properties of rabbit muscle after step loading continuous eccentric exercise. The animals exercised eccentrically for 6 and 12 days, while administering oral Chinese medicine ,external use of Chinese medicine as well as both oral and exteral use used. Through observing the work and the isometric torgue of eccentrie exercise, we found chinese medicine is useful in restoring the muscle function and the decreased viscoelastic properties of muscle caused by eccentric exercise.

Abstract:Objective To observe the histomorphlogical changes of the collagen fiber structure after the articular cartilage was subjected to loading. Methods The articular cartilage specimenns from 12 human femoral heads were studied under scanning electronic microscope to observe the structure changes under different sets of loadings. Results The collagen fibers tended to become bended when they were subjected with loadings.The bending of the fiber became more marked and finally disrupted as the loads increased. Conclusion When the articular cartilage is loaded with abnormally high stress,it may result in damage or even cause the disruption of the collagen fibers.

Abstract:Objective To establish the fatigue test device and observe the stiffness of two spinal posterior fixation devices in the fatigue test. Methods The testing apparatus consisted of two round plate which fixed specimens. The pivot of upper plate, which was fixed balance rods, was made of a 3 cm anterior offset to the specimens. To simulate the effect of erector spinae muscle force on the spinal segment, a sping was mounted between the two rods posterior the specimens. In ten specimens using lumbosacral cadaveric spine(L1-S2), with an L3 burst fracture, two dorsally applied spinal fixation implants(Reduction Fixtion,RF and Modified Edwards System,MES)were used acording to clinical operation. In SANS testing machine, the specimens were loaded cyclically at 0.5Hz in(440±165)N for up to 10,000 cycles. Displacement transducers monitored motion at the site of instability and at the segment below the implants. Flexibility at these segments were measured at initial and 1500 and 10000 cycles. Results In the fracture models, a one-way analysis of variance showed that there were more significant differences in flexibility of the two fixation constructs(P<0.05). The stiffness of RF and MES was increased at initial cycles. RF allowed significantly more rigid across the site of instability than MES at 1500 and 10000 cycles. There were no significantly more stiffness between the fixation constructs and intact spine at the segment below the implants. Conclusion This fatigue test device is fit for biomechanical study of spinal interal instrumentation.

Abstract:Based on the result of processing CT image, various interpatation algorithm,including Lagrange interpretation? Newton interpretation? Hermite interpretation and Spline interpretation etc, are applied to set up the outline's curve. Each algorithm's merit and demerit are compared from itself to its' applicability for medicine. A series of problem, which will be faced during the course of 3D design, are discussed roundly in this thesis.