Abstract:Objective To explore the biological influence of shear stress on intact artery. Methods The common carotid arteries of pigs were cultured with a new artery organ-culture system under shear stress in vitro. 100mmHg of pressure and stable flow were selected. After 1, 4 and 7 day, immunohistochemistry was performed on the sections of artery with antibody to antigen BrdU. Apoptosis were identified by morphology, TUNEL and Hoechst 33258 staining. Results The results showed that the proliferation rate of vascular smooth muscle cells (VSMC) increased continuely while the apoptosis rate increased at first and then decreased under low shear stress, maximum on day 1. Conclusion These results suggest that proliferation and apoptosis of VSMC have important effects on vascular remodeling under low shear stress; Unbalance of proliferation and apoptosis may be one of foundations of cardiovascular diseases.

Abstract:Objective Cardiac Qi-Deficiency(CQD) is one of the main syndrome of TCM (Traditional Chinese Medicine). Based on Qi-Blood Transportation theory and blood-tissue fluid circulation analysis, a hemodynamics model describing CQD was set up to explore its dynamics mechanism.Methods Through analyzing the calculating results, the regulary influence of the vascular hemodynamics parameter′s changes on the interstitial edema's (main symptom of Qi-Deficiency) formation has been obtained, and quantitative relationship between the vascular hemodynamics parameters and the edema degree was given.Results To compare the theoretical results with the CQD research of clinical and animal experiments, it showed that our model could explain the physiological and pathological mechanism of CQD quantitatively. When the vascular parameters (for example, the total blood volume, the remote vascular resistance, and the cardiac contract force ) change, the interstitial volume will increase, which could lead to the decrease of the concentration of the protein and other nutritious contents.Conclusion the Qi content of CQD is closely relative to the nutrition concentration in the tissue fluid, when more water moves from blood to the inter-tissue, the content concentration in tissue-fluid will decrease, which will affect cell's physiological function and lead to symptoms of Qi-Deficient.

Abstract:Objective There are many disadvantages in prolonged immobilization aften the repair operation of Achilles tendon while with early functional exersice conspicuous result could be got in Achilles tendon repair. To probe into the mechanical characteristics of different suture materials and slip-knots in knotted condition and to provide reliable scientific evidences in support of the new technique uesd for suture combination without prolonged cast immobilization at postoperation in Achilles tendon rupture. Methods Measuring the mechanical properties of different suture materials by cutting 16 piescs of Coated Vicryl-910,Mersilk,Nylon,Polydioxanone filaments in the middle of the line respectively and tying 4 knots in each. Results The tests show that the maximum load?Young,s modulus?strength? Raroenergy are: PDS>Coated Vicryl>Nylon>Mersilk(P<0.05). Conclusion Despite PDS have the tendency of slip-knot, 1/0-PDS?1/0- Vicryl and 1/0 Nylon filament all have the admired strength for end to end simple repair. 5/0 PDS?5/0 Coated Vicryl filaments also have the significant strength and it would be better by tying more than 4 knots. Although Mersilk have less slip-knot instincts trend, it is not suitable for Achilles tendon repair. Nevertheless,The choosing of suture material is equal vital as choosing of the most advisable suture combination.

Abstract:Objective To investigate the biomechanical influence of vertebroplasty on the adjacent vertebral body and intervertebral disc. Methods Six fresh cadaver specimens were applied to make 6 T 12-L 2 function spine unit (FSU) as group A,and 6 L 3-L 5 FSU as group B, respectively. All the FSU were underwent flexion-axial loading to result in middle vertebral body fracture. Following reduction,the middle fractured vertebral body were strengthened by the method of vertetroplasty, with group A using Calcium Phosphate Cement (CPC), group B using Polymethylmethacrylate(PMMA) respectively. Before fracture and after vertebroplasty, all the FSU were conducted biomechanical test. Results In the CPC group(group A), the stiffness of middle vertebral body were enhanced by 19%, without any affection on the stiffness and strength of the whole FSU, the stiffness of upper vertebral body decreased by 6.7%, the height of upper disc is decreased evidently. In group B, even when the stiffness of middle vertebral body were 5 to 6 times augmented, the stiffness and strength of the whole FSU were still not affected ,the stiffness of upper vertebral body decreased by 24.4%, the height of upper disc were decreased very evidently. Conclusion Following vertebroplasty, the enhanced vertebral body don't result in great stress concentration in the adjacent vertebral body, especially with CPC, it means that vertebroplasty technique is safe in the respect of biomechanics. While some extend of stress concentration are present in the adjacent dise, which will possibly accelerate disc degeneration process.

Abstract:Objective To explore the biomechanical properties of pig thoracic aorta. Methods 54 pig thoracic aortas aged from 1 to 9 months old were observed by cutting the middle regional vessels into short segments. Thoracic aortas from 7-month-old pigs were divided into three regions: superior, middle and inferior regions and each region was redivided into 5 shorter segments. The equivalent inner diameter and the mean wall thickness were measured after every segment has been cut radially for 20 minutes. Results With age the opening angle of pig thoracic aorta aged from 1 to 7 months old increased from (42.17±4.06)° to (76.22±4.40)°, after 7 th months became stable ,while in the same age pigs the opening angle of thoracic aorta decreased from (99.73±6.79)° in the superior region to (42. 09±7.40)° in the inferior region. The ratio of the wall thickness and the equivalent inner diameter decreased with age and stayed at about 0.18 after 7th months. Conclusion The opening angle, wall thickness and equivalent inner diameter of the studied pig thoracic aortas increase with age, but tend to decrease with the longitudinal distance X/L increasing. The inner and outer diameters increase after 7th months simultaneously. The results are useful for providing essential data for pig→human vascular xenotransplantation and analyzing the pathological recovery and remodeling process.

Abstract:Objective To investigate an ideal method of treating bovine pericardial. Methods The changes of biomechanical and ultrastructural properties of the bovine pericardial affer different treatments were studied by the shrinkage temperature analysis and uniaxial load test. Results After the treatment, the thickness and stiffness of pericardium were increased, whereas the plasticity and flexibility were decreased, which became similar to the biomechanical properties of bioprosthesis. The modulus of elasticity of 2,3-butanediol post-treatment group is higher than that of glutaraldehyde-fixed group (8.75±1.71 versus 6.59±1.37, P<0.05), which was similar to that of nature valve tissue. The ultimate tensile stress of glutaraldehyde-fixed group was higher than that of 2,3-butanediol post-treatment group (P<0.005). Histological examination revealed some changes in structural organization of the collagen, which explained the alterations in the biomechanical properties. Conclusion The 2,3-butanediol post-treatment is a better method of treating bovine pericardial, which improved the biomechanical properties of bovine pericardial.

Abstract:Objective To probe into the effects of the varying size of intravertebraldefect on the strength of the vertebral body under compression-flexion loading. Methods 18 vertebraes from 6 fresh cadavers were diarticulared, with their discs excised and the posterior element removed.The upper and lower adjacent vertebrae were used as controls to generate an estimate of intact middle vertebyal body strength,and the strength of the middle vertebral body with intravertebral defect were measured, which was made by a small scraper through venous aperture in the posterior edge of vertebrae. Results The result demonstrated a positive correction between vertebral body strength and the volume of the vertebral body defect. Compared with intact vertebral body,the strength of damaged vertebral body decreased 10.67%?18.00%?26.83%, with its defect rate 10%?20%?30%respectively. Conclusion The result show a positive correction between vertebral body strength and the volume of the intravertebral body defect. When the volume of cancellous interior of intravertebral body defect exceeds 30% of vertebral body volume,the patient is at risk of pathological fracture,so internal fixtion is indicated.

Abstract:Objective To design a new kind of bi-plate for fixation of long bone comminuted fracture, and detect its mechanical properties. Methods We designed limited contact chute bolt compression bi-plate, and detected its mechanical properties by electrical methods, comparing with single plate and simple bolt bi-plate made by the same material and technology. Results The axial strength of limited contact chute bolt compression bi-plate was different from those of simple single plate and traditional bi-plate (P<0.01). There was no obvious difference with traditional bi-plate in anti-bending property, but obvious difference with single plate (P<0.01). It has low stress protection effect. Conclusion Limited contact chute bolt compression bi-plate has high strength and low stress protection effect. It becomes possible for early functional exercise and accelerated bone union procedure. It provides a new method for rigid internal fixation with low stress protection effect.

Abstract:Objective Two-rigid-body system of human upper extremity was founded with some proper simplification on the analysis of the physiological structure and motion characteristics of the upper extremity structure. The motions of such upper extremity were analyzed. Methods Using ADAMS simulation software, the upper arm and the forearm were simplified as two rigid-bodies, the conjunction between the upper arm and the trunk as a spherical joint, the conjunction between the upper arm and the forearm as a revolute joint, and muscular actions as forces acted on the mass centers of the upper arm and the forearm. Thus, motion models for human upper extremity were founded and simulation were carried out on the three simple motions for abduction/adduction, inner rotation/outer rotation and flexion/extension. Results The model simulation is coincided with the practical motion of human upper extremity. Conclusion Motion model of human upper extremity may be well founded by using ADAMS to analyze the motion of human upper extremity.

Abstract:Objective Study the difference of tensile strength, compressive strength, bending strength and twisting strength between the femoral bone and tibial bone of Qinghai bosgrunniens and lake bostaurus.Methods Crura bones taken out from 6 adult Qinghai bosgrunniens and 6 adult lake buffalos were made into standards objects as test requirement. For each test 3 samples were taken out from different oxen.With traditional mechanics method and equipment, 4 experiments on tensile strength, compressive strength,bending strength and twisting strength of the femoral bone and tibial bone have been made between bosgrunniens and bostaurus. Results For the femoral bone of Qinghai bosgrunniens tested, the tensile strength is (106.35±3.45)MPa, compressive strength is (127.60±2.65)MPa, bending strength is (225.9±4.1)MPa, and twisting strength is (53.45±1.55)MPa. For the tibial bone tested, tensile strength is (114.96±1.46)MPa, compressive strength is (184.75±3.25)MPa, bending strength (211.35±2.45)MPa, and twisting strength is (51.9±0.5)MPa. While the tibial bone of lake bostaurus the tensile strength is (128.1±11)MPa, compressive strength is (195.8±9.4)MPa, bending strength is (167.4±12.7)MPa, and twisting strength is (54.25±0.75)MPa. Conclusion Primay data of the stress of Qinghai bosgrunniens and lake bostaurus have been obtained.