Abstract:The method of biomechanical modeling and computer simulation for human movement has been widely used in such research fields as elucidating physiological mechanisms of different kinds of movements, investigating the causes of sports injuries, helping to promote sports performances and to prevent injuries for athletes. Such method involves mathematical modeling on a series of physiological, anatomical and mechanical characteristics of human bones, joints, muscles and nerves. Muscle forces exerted during movements can be estimated using algorithms based on such models. Meanwhile, simulation experiments can be performed and make the results visualized by using computer software. This paper will review the biomechanical modeling and computer simulation of human movement and its application in details.

Abstract:Multi-component synthetical nanofiber is a result from blending nanotechnology, material science and biological science. The nanofiber represents a kind of classic nanostructures that can fully simulate the microenvironment of fibrous structure in vivo, while providing topographical structures, biomechanics and biochemistry agents to promote tissue regeneration and wound healing. These fibers are prepared with mixtures of naturally and synthetically derived polymers. They have synergistic effect on mechanical properties, biological response and structural properties and play an important role in tissue engineering and drug delivery.

Abstract:Objective To study the mechanisms of vascular remodeling induced by hypertension and/or low shear stress, which will be helpful in the prevention, diagnosis and treatment of cardiovascular diseases. Method The models of low shear stress in carotid artery or of hypertension were established by the ligation of partial distal branches of the left common carotid artery (LCA) or by the coarctation of aorta in SD rats, respectively. For some rats, the low shear stress in LCA was accompanied by the hypertension. The wall thickness and the ratio of wall thickness to inner diameter were determined by morphometrical approach. The MMP-2 activity was detected by gel zymography, and the expression of proteins, including p-Akt, Rho GDIα, was verified by Western blotting in LCA. Results When LCA was subjected to hypertension or low shear stress, MMP-2 activity, the wall thickness, and the ratio of wall thickness to inner diameter were all increased significantly. They were further enhanced when the hypertension and low shear stress were both existed, which would speed the vascular remodeling. Low shear stress induced the expression of p Akt, and the lower shear stress, the higher p-Akt expression would be. However, the highest expression of p-Akt was observed in LCA of hypertension accompanied by low shear stress. The expression of Rho GDIα was upregulated in LCA by either low shear stress or hypertension. The highest expression of Rho GDIα was observed in LCA of hypertension accompanied by low shear stress. Conclusions Vascular remodeling could be mostly influenced in LCA subjected to low shear stress accompanied by hypertension, which was also regulated through the changing expression of p-Akt and Rho GDIα.

Abstract:Objective To investigate the effect from mechanical stimulation and osteogenic chemical inductor on osteoblastic differentiation markers and formation of calcified nodules in rat bone mesenchymal stem cells (rBMSCs). Method The rBMSC were cultured in medium contained with or without osteogenic chemical inductor. The cyclic biaxial mechanical strain (2%), at a frequency of 1 Hz, was applied to the rBMSCs for periods of 2 hours each time, at intervals of 2 hours, 3 times every day, lasting 3 days and 6 days, respectively. The mRNA expression of alkaline phosphatase (ALP), collagen type I (COL I) and osteocalcin (OCN) were analyzed with real time fluorescent quantitation reverse transcription polymerase chain reaction(qRT-PCR) and formation of calcified nodules were detected with alizarin red staining method. Results The mRNA expression of ALP, COL I and OCN were significantly increased in induced group compared with that in the corresponding uninduced group and calcified nodule was observed in the osteogenic chemical inductor group after 6 days with mechanical stimulation. Conclusions Osteogenic chemical inductor and mechanical stimulation can promote the osteoblastic differentiation of rBMSCs.

Abstract:Objective To explore the role of mechanical stimulation in synovium under different pathological conditions through studying the effects of cyclic mechanical stretch on the expression of bone morphogenetic protein 2 (BMP-2) in rheumatoid arthritis (RA) and osteoarthritis (OA) fibroblast-like synoviocytes (FLS). Method 6% and 0.5 Hz stretch generated by Flex cell 4000 tension systems was applied on normal, RA and OA FLS of human knee joint source under normal and inflammatory conditions for 2 h or 6 h, respectively. Results Cyclic mechanical stretch of 6%, 0.5 Hz had no significant effects on the expression of BMP-2 in normal, RA and OA FLS at 2 h, while in RA FLS it increased significantly at 6 h. Inflammatory cytokines (IL-1β) didn’t influence normal FLS at 2 h, but made BMP-2 mRNA significantly increased at 6 h. IL-1β increased BMP-2 mRNA of RA FLS significantly both at 2 h and 6 h. IL-1β increased BMP-2 mRNA of OA FLS significantly only at 2 h, but had no significant effect at 6 h. The co-effect of IL-1β and cyclic mechanical stretch induced the ascension of BMP-2 expression significantly in normal and RA FLS at 2 h, and in normal, RA and OA FLS at 6 h. Conclusions Response of BMP-2 mRNA to mechanic stimulation and IL-1β in normal, RA and OA FLS were different. Inflammation may play a more important role than mechanical stimulation in the pathogenesis of RA and OA. Synergetic effect in inflammation and mechanical stimulation were found in OA FLS at 6 h, which reveals that they may co-act in the occurrence and development of OA.

Abstract:Objective To investigate the effect of focal adhesion kinases (FAK) inhibitor with different concentration on the adhesion and migration of endothelial cells (ECs) and the expression of downstream Rac1 protein, and to explore the role of FAK in adhesion and migration of ECs by using FAK inhibitor to inhibit the phosphorylation of Y397 site of FAK. Method Scratch wound migration assay was performed to examine the effect of FAK inhibitor with different concentration (from 0 nmol/mL to 250 nmol/mL) on ECs migration at 2, 4, 8 and 24 h, respectively. Western blot combined with immunofluorescence analysis were performed to determine the effect of FAK inhibitor with different concentration on distribution and expression of Rac1 protein. Results With the concentration of FAK inhibitor increased, ECs migration distance and the Rac1 protein expression decreased. Conclusions The inhibition of FAK phosphorylation could inhibit cell adhesion and migration with the decrease in downstream Rac1 protein, and ECs adhesion/migration was related to FAK Rho GTPases signaling pathways.

Abstract:Objective To raise a quantitative indicator for the waveform similarity between different signals of the same kind and apply it to the analysis on the vertical force signals from the rolling manipulation. Method After two signals of the same kind were normalized and their waveform errors were analyzed, the waveform similarity, which was to be utilized to describe the extent to which two signals were similar to each other, was defined. Then, the vertical force signals of the rolling manipulation operated by several experts, graduates who have learned the manipulation for some time and beginners were measured, respectively. Subsequently, the values of the waveform similarity between the three different groups of signals were calculated. Results The similarity between the experts’ signals was relatively high, so it was reasonable to be used as a template for other operators’ signals to be compared with. Further calculation revealed that the waveform similarity between the experts’ signals and the graduates’ was generally lower than that between the experts’, and the similarity between the experts’ and the beginners’ was the lowest. There was significant difference between the three groups. Conclusions The waveform similarity raised in this paper could serve as a quantitative indicator for the similarity between different vertical force signals from the rolling manipulation, and this method was also applicable to the similarity evaluation between other approximate periodic signals.

Abstract:Objective To obtain pressure-volume relatioship for the rabbit eye in vivo. Method Physiological salt solution was injected with the rate of 20 μL/min through the limbus to the anterior chamber of the rabbit eye for 100 min and the intraocular pressure (IOP) was recorded. Results The relationship between IOP and injection time could be fitted to a segmented function with a characteristic point called IOPg. The ocular rigidity coefficients before and after this IOPg were (4.02±0.86) mmH2O/μL and (2.43±0.94) mmH2O/μL, respectively (1 mmH2O=9.8 Pa), showing significant difference. Conclusions IOPg existed in all curves of IOP and injection time and the ocular rigidity coefficients were dependent on the injection rate and position of IOPg. Parameters of the fit function between IOP and injection time have definite physiological significance.

Abstract:Objective An effective but simple method for quantifying the fracture healing progress was provided to obtain more information on fracture healing mechanics from plain X-ray film. Method Twelve rabbits were used for experimentally osteotomy at the middle tibiae, each of which was fixed by the sliding fixator with four pins of 1.5 mm diameter, with mini transducer of displacement measuring the sliding micro movement between the fractured bone fragments, denoted as ΔL. The bending rigidity, denoted as K=P/ ΔL, of the rabbits’ tibia (with sliding fixator together) were recorded by computer data assembling system once a week, where P was the load on the fracture site from anterior of the tibia by manual operation of a loading transducer. The anterior posterior and lateral radiographs were also taken every week by digitally upgraded X-ray radioscope. The effective weakest transverse curved interfaces were found, and the equivalent bending moments of inertia were calculated from the radiographs automatically, by gray scan along the longitudinal axis of the tibia upon the image programs edited in Delphi programming environment. And they were used for quantitative description of the rigidity of the healing bone. Results The sliding fixators were removed in 29~41 days after the osteotomy. Ratios of the minimum to the maximum of equivalent bending moments of inertia for each fracture bone were calculated. And they were found to increase via the healing time. The means of the ratios of all twelve rabbits calculated from lateral radiographs were (0.31±0.17) for the first week, (0.34±0.13) for the second week，(0.43±0.20) for the third week, and (0.56±0.23) for the fourth week after the osteotomy, respectively. From anterior posterior radiographs, the means of the ratios were (0.40±0.19), (0.47±0.16)， (0.56±0.20), and (0.66±0.11), respectively. These ratios were significantly correlated with the bending rigidity K of the fracture tibia of the rabbits. The means of K value was （3.976±4.986）N?μm-1 before the operation，and （0.679±1.026）N?μm-1 for the first week，（2.115±3.233）N?μm-1 for the second week，（3.459±4.723）N?μm-1 for the third week and （4.788±4.831）N?μm-1 for the fourth week after the operation, respectively. Conclusions The growth of external callus has its own rules. It can be distinguished from plain radiographs easily, and it grows from either side of the fracture site and meets together gradually, filling up the gap at the fracture site at last. The methods described in this paper could reflect the feeling when reading the radiographs.

Abstract:Objective To determine the effects of the two kinds of pedicle screws with cement augmentation used for in vitro sheep osteoporotic vertebra model. Method Forty osteoporosis specimens of lumbar vertebrae demineralized by decalcification solution were complete randomly devided into four groups including Group A (only screw),Group B (whole trajectory filled with PMMA),Group C1(partial trajectory filled with PMMA) and Group C2 (partial trajectory filled with PMMA). Osteoporosis specimens from four groups were tested by bone mineral density (BMD) and observed by spiral CT and MicroCT. The maximum force and energy absorption of pedicle screw were tested. Results BMD in each group were averagely declined about 25%～30% (P>0.05), so osteoporotic vertebrae model was successfully established.Spiral CT and MicroCT showed that screw of Group B was fully surrounded by PMMA, which constituted screw PMMA-bone interface,while screw of Group C2 was partially surrounded by PMMA, which constituted partial screw-bone and partial screw PMMA-bone interface. The axial pull-out test showed that the maximum force (Fmax) and its energy absorption in Group B, C1,2 were significantly higher than those in Group A（P<0.05）, those in Group B, C2 were higher than those in Group C1（P<0.05）, and those in Group B and Group C2 had no significant difference(P>0.05). Conclusions Both the whole and partial pedicle screw augmentation can significantly improve the strength of pedicle screw in the context of osteoporosis. The latter not only formed a special whole interface consisting of partial “screw-bone” and partial screw-CSC-bone interface,but produced the strengthening effect equivalent to the former by increasing injection doses of PMMA.

Abstract:Objective To illustrate the influences of walking speed and road slope on lower limb motions by quantitative analysis on the changes of joint angles and muscle activation. Method Five walking speeds and three road slopes were selected from slow to fast according to the related measurement. The gaits of 15 young women were measured using the motion capture system and the EMG signals of 8 major muscles in lower limbs were collected simultaneously. The mean joint angles of hip, knee and ankle in sagittal plane at different speeds and different slopes were calculated. The subject whose data was closest to the mean value could be easily found. Results The joint angles of the subject’s hip, knee and ankle in sagittal plane at different speeds and different slopes in a gait cycle were presented and the activation curves of the 8 major muscles during lower limb movements were obtained. Conclusions In each gait cycle, the curves of joint angles and muscle activations varied little with 5 different speeds, while curves for 3 different road slopes only showed similar tendencies but with different peaks.

Abstract:Objective To study the effect of continuous low frequency resonance on blood pressure, heart rate, breath rate and body temperature of the rat so as to provide basic data for the study of organs’ resonance injury and its reaction. Method Thirty two SD rats were divided into four groups randomly: false vibration group, 3 Hz vibration group, 6 Hz vibration group and 21 Hz vibration group. Femoral artery intubatton was given after anaesthesia with 1.5% sodium pentobarbital. All the rats were fastened on their back on the vibration platform staying calmly for 30 min. Then the vibration groups were given sine wave vibration with 5 mm amplitude(p-p), while the blood pressure, heart rate, breath rate and body temperature of the rats were measured at 0, 1, 3, 5, 10, 30, 60, 120, 180, 240, 300 and 360 min. The above physiological data were also observed in false vibration group at corresponding time. Results Continuous low frequency resonance could cause the blood pressure, heart rate, breath rate of the rat to rise rapidly after 1 min of vibration, and to reach the maximum value after 1 min to 3 min of vibration, and then to descend gradually and to be lower than the normal value after 30 min of vibration. The body temperature of the rat did not change at the beginning of vibration, but descended gradually after 10 min of vibration. At the beginning of vibration, the effect of 6 Hz resonance on blood pressure, heart rate, breath rate was dominating, while at the later stage, 3 Hz resonance was dominating. But the effect of the two frequencies on body temperature was accordant. Conclusions Continuous low frequency resonance can cause the blood pressure, heart rate, breath rate of the rat to rise rapidly at the beginning of vibration and then to descend gradually, and it can also depress the ability of body temperature regulation in rats.

Abstract:Objective To evaluate the difference in articular cartilage simulation due to the application of either homogeneous or depth-dependent mechanical parameters. Method The nonlinear， biphasic， porous model of articular cartilage was built using poroelasticity module in COMSOL. Under the static load, the model was computed using homogeneous and depth dependent parameter, respectively. The difference between the results was analyzed. Results For the total stress of cartilage， there was no remarkable difference between two parameter configurations. However, for the analysis such as solid phase stress, fluid pressure and flow velocity， the difference between two parameter configurations must be considered. Conclusions Different parameter configuration has negligible effect on the total stress of cartilage, but it is influential to the flow velocity. Therefore， homogeneous mechanical parameters should be used in order to simplify the total stress computation problem. The other more detailed analysis should be based on the depth dependent parameters. These conclusions could be referred to for future cartilage modeling and numerical computation and thus laying a foundation for the design and computation of artificial joint.

Abstract:Objective To investigate the design approaches and manufacturing techniques for the calibration system of side impact dummy neck. Method The ES-2 side impact dummy neck was selected as the research subject and a set of calibration system of ES 2 side impact dummy neck was developed in this experiment according to the pendulum impact theory, and the new design approaches and new manufacturing techniques suitable for the present industrial conditions in China were created to establish its two key components: the pendulum device and the head-neck flexion angle measurement device. The optimal designs for the quality distribution and inertia moment distribution of the whole pendulum were also carried out to assure the pendulum initial velocity and the pendulum impact velocity time curve during the pendulum absorber impact, while optimal designs for three angle sensors and the complex stereoscopically dependent relationship among those three sensors were carried out to assure the reliability of the head neck flexion angle measurement device. Correspondingly, a total of six calibration tests were carried out to validate this calibration system in terms of the technical requirements of ECE R95. Results The pendulum initial velocity of 3.36～3.48 m/s and the pendulum impact velocity time curve during the pendulum absorber impact, which were generated by the pendulum device in this calibration system of ES 2 side impact dummy neck, were in accordance with the ECE R95. Meanwhile, the head neck flexion angle measurement device of this calibration system was sufficient to detect the following three target angle values more accurately: the maximum values of fore pendulum base angles, the maximum values of aft pendulum base angles, and the maximum values of head neck complex flexion angles. Conclusions The calibration system of ES-2 side impact dummy neck is basically capable of meeting the demands of the existing international rule, the ECE R95. Besides, this neck calibration system is convenient and practical, and its design approaches and manufacturing techniques are likely to find the wider application in the impact biomechanics field.

Abstract:Objective It is demostrated that the porous protein mineral mechanics model could provide more accurate prediction for biomaterial properties of dentine compared with the other established models. This paper would use the model to reevaluate the mechanical properties and its interacting mechanism of human dentine. Method By using a porous protein mineral mechanics model, the effect from the interactions between tubules, peritubular and intertubular matrix on dentine microstructure was discussed. Results The dentinal micromechanical properties were dependent on the tubular direction, and the absolute values of the stresses derived from the hydraulic and gas tubular pressures increased parabolically with the increasing diameter of the tubules. It was also found that the effective elastic constants of the dentine microstructure would vary with the aging and the distribution of mineral and collagen within peritubular and intertubular matrix of detine. Conclusions The theoretical analyses provided in this paper demonstrated that the microstructural characteristics of tubules, peritubular and intertubular dentinal matrix could have different influences on the micromechanical properties of human dentine, which showed the validity of porous protein mineral mechanics model, and the limitation of some models that neglected the interacting mechanism.

Abstract:Objective To study the biological macrofeatures and criterion thereof for fracture immobilization in Chinese Mongolian traditional osteopathy. Method The principles and methods of modern physiological psychology and biomechanics were used in this study to explore the biological macrofeatures and criterion thereof for fracture immobilization, based on the view of the harmony of human and nature (including a unity of body and function) in Chinese Mongolian traditional osteopathy. Results Chinese Mongolian traditional osteopathy implies the biological macrofeatures and criterion thereof for “dynamic immobilization” in fracture treatment, including the stability of structure and force catched, state of static and dynamic, forming and destroying of bone, physical and psychological stability. Therefore, it is a kind of non invasive and non shelter fixing method. Conclusions The biological macrofeature and criterion thereof for the fracture dynamic immobilization in fracture treatment, in Chinese Mongolian traditional osteopathy is not only the fundamental support for its inheritance up to now, but also could be a new attempt in modern fracture immobilization.