Abstract:Objective To study the short time effects of cyclic mechanical stretch on human adenocarcinoma cell line A549. Methods By Flexercell-4000TTM Unit, A549 cells were subjected to 20% elongation of biaxial stretch at frequency 30cycles/min within 4h. Results Short time mechanical stimulation can enhance the proliferation rate of A549 cells. The proliferation responding ratio M(%) vary with the loading time: M(%)=18% for 0.5 h, M(%)=22% for 1 h and M(%)=5% for 4 h. Conclusion There seems to be a peak of M(%) when the cycle number is about 1800 cycles. This feature is similar to the human bone derived cells. Further experiment demonstrates that intermittent loading could result in high proliferation of the A549 cells for long time whereas the past studies showed the continuous loading can only depress A549 cells proliferation.

Abstract:Objective To study the change of local biomechanical property after treatment of femoral head necrosis with BMP-2 gene therapy. Methods 11 goats with 22 sides were divided into 4 groups: Ⅰnormal group (n=6 ), Ⅱ untreated group (n=6 ), Ⅲ β-gal group (n=5), Ⅳ BMP-2 group (n=5). TCP (β-tricalcium phosphate) loaded with Adv-βgal or Adv-hBMP-2 gene transfected MSCs was implanted into femoral head at 3rd week after establishment of animal models of femoral head necrosis. All goats were killed at 16th week after treatment. Sub?-chondral bone and cancellous bone were harvested to test its biomechanical property. Results The maximum stiffness and elastic modulus of cancellous bone in BMP-2 group were (38.35±4.16) MPa and (86.85±7.28) MPa, respectively. The maximum stiffness and elastic modulus of sub-chondral bone in BMP-2 group were (80.76±5.32) MPa and (126.65±10.88) MPa, respectively. The parameters in BMP-2 group are higher than that both in β-gal group and untreated group(P<0.05), but close to normal group. Conclusion The BMP-2 Gene transfected autologous bone marrow-derived mesenchymal stem cells can accelerate the repair of femoral head necrosis and prevent the collapse of femoral head.

Abstract:Objective To analyze the interface biomechanical properties between femora and bioactive ceramics coatings prosthesis during the initial implant stage. The objective is to optimize the thickness of bioactive ceramics coatings on the metal surface. Methods Biomechanical models of press fit implanting the femora with non-homogeneous layer-like materials were used to quantify the press fit strength and circumferential stress of the interface when the femora were replaced with the different thickness of bioactive ceramics coatings prosthesis during the initial implant stage. Results The maximum press fit strength appears on the interface between femora and non-coatings layer Ti alloy prosthesis; the press fit strength decreased with the thickness increase of coatings layer. The circumferential stress displayed as the large tensile stress at the femora side of the interface; the compressive stress appeared at the coatings layer and Ti alloy prosthesis side of the interface. Conclusion The shearing strength of joint between the prosthesis and femora would be bigger with the thinner bioactive ceramics coatings.

Abstract:Objective To investigate the effect of OGP(10-14) and its derivatives G38I and G38K on bone biomechanical characteristics of femur and lumbar vertebra in rats with ovariectomy-induced osteoporosis. Methods Fifty-six female Sprague-Dawley rats, three month old, were randomly divided into 7 groups. Rats in group 1 to 6 were bilaterally ovariectomized (OVX) and the others in group 7 were sham-operated. Group 1 to 5 received OGP(10-14), G38I, G38K, residronate and alendronate respectively by subcutaneous injection daily after surgery. Group 6 and 7 received vehicle only. The rats were killed 60 days after operation. The left femora were taken for three-point bending test and the lumbar vertebrae were taken for compression test. The data were derived and analyzed by computer. Results The maximal stress and maximal strain of lumbar vertebra in OVX group were decreased to 80% and 65% respectively compared with the sham group. The changes in spine were more significant than that in femora and implied that cancellous bone was impacted earlier than cortical bone when osteoporosis happened. After the treatment, femoral elasticity bending stress increased significantly in G38I and G38K groups compared with OVX group. Although maximal bending stress and elastic modulus of femora enhanced in treated groups, the differences were not so significant. In OGP(10-14) -treated group, the maximal stress of lumbar vertebra was 1.28-times more than that in OVX group (P<0.01) and was similar to the group with bisphosphonates. The elastic modulus of lumbar vertebra was increased to 1.35-times in OGP(10-14) group compared with OVX group. Conclusion After the treatment with OGP(10-14) and its derivatives, the anti-impact and anti-compression ability of bone were increased in osteoporotic rats while the biomechanics was improved.

Abstract:Objective To set up the multiple regression equation that could immediately calculate the segmental move inertia of the Chinese young male bodies by determining the data of move inertia of the segments and the mathematical model. Methods By using the CT-DIP method in this project , to carry out the determination for 50 Chinese young male living subjects (18～23 year-old) on their posture parameters , the scanning , image analysis , calculation , and progressive regression so that to choose and define the important variable quantities. Results A series of the data on move inertia of the segments were obtained and set up the mathematical model consisted of 15-segments. The multiple regression equation was then established which could immediately calculate the move inertia of the segments of the Chinese young male bodies, in which the body weight , the stature , and the segmental length , the wide, and the contour were usedas independent variable quantity. Conclusion This study provided the dependable means to calculate immediately the move inertia of the segments of the Chinese young male bodies .

Abstract:Objective Research on the viscoelastic properties of L5 lumbars got from fresh corpse of our country. Methods Make the stress relaxation test and the creep test on them with Shimadzu AUTOGRAPH electronic universal testing machine. Results The stress relaxation and reduced creep data and the curves of L5 were obtained. The reduced stress relaxation and reduced creep function and its curves were also gained, together with the regressive coefficient a,b,c and d. Conclusion The L5 spine's stress relaxation quantity is 0.261MPa and the creep quantity is 0.217%.

Abstract:Objectives To evaluate the hip stress status in vivo in order to serve for clinic. Methods Based on gait database of the human hip in vivo collected by Biomechanics Lab of Berlin University and Hertzian elasticity contact theory, a realistic stress level analysis for dynamic cases at hip joint(including: walking slowly, walking normal, walking fast, knee bend, going up stairs, going down stairs, standing up and sitting down activities) is presented. Results The maximum peak stress for the human eight routine activities is 11.25 MPa, 11.38 MPa, 11.89 MPa, 10.32 MPa, 11.66 MPa, 11.63 MPa, 10.37 MPa, 10.29 Mpa respectively; The minimum peak stress for the human eight routine activities is 5.32 MPa, 5.77 MPa, 6.54 MPa, 7.40 MPa, 5.96 MPa, 6.41 MPa, 6.00 MPa, 5.56 MPa respectively. The average peak stress is 8.75 MPa, 8.95 MPa, 9.63 MPa, 8.70 MPa, 8.83 MPa, 9.23 MPa, 8.01 MPa, 7.77 MPa. Conclusions (1) The peak stresses in human routine activities range from 5.32 MPa to 11.89 MPa; (2) The general average peak stress in the human routine activities is 8.72 MPa; (3) The peak stress distributions have a double peak curve for walking cases, and there exist the peak stress for the walking fast case.

Abstract:Objective To elucidate the biomechanical foundation of Swan-like Memory Compressive Connector(SMC ) for treatment of humeral fracture. Methods To analyze the biomechanical stability of the fixed humeral fracture with SMC and eight holes plate by three methods: tension test bending test and torsion test. Results From three tests above,the relation of load-straining load-migration bending moment- deflection?torsion moment-torsion angle were drew, both of results show no statistical significant deviation. Conclusion Internal fixation of humeral fracture with SMC could have good biomechanical stability.

Abstract:Objective To investigate biomechanics of Achilles tendon on an in vivo model. Methods 45 rabbits were averagely assigned into 3 groups at random. Group A (normal left Achilles tendon), Group B (normal right Achilles tendon), Group C (non-innervated left Achilles tendon). Their biomechanical variables were measured by modified buckle transducer. Result The tension-time curve can be mainly classified into four types (I, II, III, IV). Biomechanical variables of Achilles tendon under non-innervated condition were much lower than those under normal condition (P<0.05). Conclusion Modified buckle transducer can be used for measuring tension of Achilles tendon in vivo and be characterized as feasible, stable and sensitive.

Abstract:Objective To compare the biomechanical performance of pedicle screws with different forms in lower thoracic and lumbar vertebra. Methods 54 vertebral specimens were obtained from 6 fresh normal frozen cadavers (T9-L5). The experimental 5.5 mm conical pedicle screw was implanted at one side at random and tested with an MTS machine (858 Bionix Ⅱ). To measure the maximal insertion torque firstand then the maximal pull-out strength. The same experiment was done with the cylindrical screw of 5.5 mm on the other side. Then the revision test with 6.25 mm and 7.0mm pedicle screws was done in the lumbar region. Strength dada were recorded. Results At lower thoracic region the torque of conical screw(1.445±0.66) N.m was distinctly higher than that of the cylindrical screw(1.073±0.42) N.m(P<0.05),but in the lumbar region such difference was not found. Conical and cylindrical screws have similar pull?-out strength. Correlation between insertion torque and pull -out strength was statistically significant with the cylindrical screw(r=0.629), but not with the conical screw (r=0.179). The displacement when reach the maximal pull-out strength was similar for the screws with the different forms. Conclusion The conical screw has the similar pull-out strength with that of the same diameter cylindrical screw. And if the diameter of conical screw is similar with the inner-diameter of pedicle, it has the higher insertion torque. The relationship between the insertion torque and pull-out strength is based on the different screw form.

Abstract:When cells are exposed by force they will have many effects of expressions. In this study we will introduce different experimental methods about cells exposed by force and different effects of expressions are studied. The article is mainly concerned with the mechanosensitive channel currents recorded in microvascular endothelial cells, ICAM-1 expression, the secretion of monocyte chemotactic protein-1,expression of proto-oncogenes c-fos and c-myc.

Abstract:Objective Bone tissue has a optimal structure, which could present a typical example to show how the structure-function of bone controlled by biomechanics The mechanics plays an important role in the growing, reconstructing and shaping of bone. But up to now it has not been able to essentially illustrate this mechanic stimulation The bone tissue is a kind of porous struction and its deformation resulted from mechanic loading can cause fluid flow to make the effect on bone cells, which also has been proved by the vitro experiments. So the flow shear stress is one of the important factors when study bone tissue controlled by mechanic loaded, The present study on the flow shear stress mainly shows the effective function of theflows, the bio-reaction of cells and the mechanic transmission researched by the flow shear stress in cells.Many of these studies indicated that at least in part fluid shear stress is concerned with the mechanotransduction in bone tissue

Abstract:Flow chamber is one of the most effective equipment to study the response about blood corpuscle and endothelioid cells under the condition of hemodynamics in vitro. This is also one of the main methods for study the response about blood corpuscle and endothelioid cells under the condition of hemodynamics.The classification, the simulation, including the data simulation of the flow chamber with a backward step, and the construction of the flow chamber are described .