Abstract:Cardiovascular disease is one of the most serious diseases endangering human life and health. In China, 2 out of every 5 people die of cardiovascular diseases. Myocardial ischemia is one of the important cardiovascular diseases. Fractional flow reserve (FFR) is used to quantify myocardial ischemia in epicardial stenoses. Index of microvascular resistance (IMR) is an invasive index for quantitative evaluation of coronary microcirculation. Traditional FFR and IMR measurements rely on guide wires to perform interventional measurements under the maximum hyperemia state,so as to assist the diagnosis of myocardial ischemia clinically. Coronary angiography-derived FFR and IMR without using invasive pressure-wire measurement, hyperemic stimulus and contraindications can assist the diagnosis and treatment of percutaneous coronary intervention by fast simultaneous calculation of FFR and IMR. In this review, the research progress of coronary angiography-derived FFR and IMR as well as other coronary physiological evaluation in recent years were summarized. It is of great clinical value to further study the combination of coronary angiography-derived FFR and IMR in functional research of coronary circulation from macro to micro.
Abstract:Objective To investigate the effect of cyclic stretch on Src and Runt-related transcription factor 2 (RUNX2), and their pivotal roles in migration of vascular smooth muscle cells (VSMCs). Methods The 5% cyclic stretch (to simulate normotensive physiological condition) or 15% cyclic stretch (to simulate hypertensive pathological condition) was applied to VSMCs by FX-5000T system. Western blotting was used to detect the expression of RUNX2 and phosphorylation of Src in VSMCs. The Ingenuity Pathway Analysis (IPA) bioinformatic software was used to analyze the potential regulatory effect of Src on RUNX2. Small interfering RNA (siRNA) was transfected to decrease the expression of RUNX2. Src inhibitor-1 was used to repress Src kinase activity; Wound-healing assay was applied to detect VSMC migration. Results Compared with 5% cyclic stretch, 15% cyclic stretch significantly increased RUNX2 expression in VSMCs. Under both static and 15% cyclic stretch conditions, VSMC migration was significantly inhibited after reducing RUNX2 expression with siRNA transfection. IPA indicated that Src kinase might be the upstream modulator of RUNX2, and Western blotting validated that RUNX2 expression was significantly decreased after inhibiting Src. Furthermore, under 15% cyclic stretch, Src inhibitor-1 markedly repressed RUNX2 expression and VSMC migration.Conclusions High cyclic stretch increased phosphorylation of Src kinase and expression of RUNX2, which subsequently induced VSMC abnormal migration. Exploring the mechanobiological mechanism of VSMC migration regulated by cyclic stretch may contribute to further revealing the mechanism of vascular physiological homeostasis and vascular pathological remodeling, as well as providing new perspective for the translational research of vascular remodeling upon hypertension.
Abstract:Objective To study the difference in thrombus formation at distal end of the graft with two different treatments.Methods For coronary artery bypass grafting with distal-end side-to-side anastomosis (DESSA), two models with or without distal end trimming of the graft were established. Using the blood substance transport and diffusion model considering biochemical reactions, combined with hemodynamics parameters of shear rate, fluid residence time, and platelet distribution, the possibility of thrombus formation was evaluated. Numerical simulation method was used to investigate thrombus growth in coronary artery bypass grafting with DESSA.ResultsFor the model without distal end trimming of the graft, the thrombus was first formed on inner wall at distal end of the graft, and then grew inward until the thrombus occupied most of the graft region at distal end, which indicated that thrombus formation was in a stable state, and the volume of the thrombus didn’t change, the final volume of the thrombus was 15.05 mm3. For the model with distal end trimming of the graft, the final volume of the thrombus was 7.35 mm3, which was 51.2% smaller than that of the model without distal end trimming of the graft. Thrombus was formed on inner wall of the graft above the anastomosis for the model with distal end trimming of the graft, and the wall thickness was about 0.16 mm, which was 10.65% of the graft radius (1.50 mm). In the above two procedures, multiple vortices (blood flow velocity less than 10 mm/s) were formed in distal region of the graft, which further promoted thrombus formation at distal end of the graft. The area of thrombus formation obtained from numerical simulation was consistent with clinical investigation.Conclusions For clinical coronary artery bypass grafting with DESSA, the volume of the generated thrombus can be reduced for the model with distal end trimming of the graft. However, the effect of thrombus formation on inner wall of the graft above the anastomosis on coronary artery bypass grafting needs further study.
Abstract:Objective To explore the application of three parameter identification methods (impedance modulus curve method, impedance component method, and genetic algorithm) in solving parameter identification problem of the 11-element lumped parameter model in the circle of Willis. Methods Using the flow and pressure waveforms of the internal carotid arteries and vertebral arteries on both sides as inlet conditions, parameter values of the model under normal and bilateral vertebral artery stenosis conditions were calculated. The recognition algorithm was verified by using Simulink models, and finally the stability of the recognition algorithm was verified by adding a certain noise to the flow. Results Under normal circumstances, the proximal resistances obtained by the impedance modulus curve method were larger, and the resistances of the anterior communicating artery obtained by the impedance component method were larger. The genetic algorithm could obtain relatively reasonable model parameter values. In the case of vertebral artery stenosis on both sides, the impedance modulus curve method could obviously get the results of the increasement in proximal resistances of the posterior circulation, but the results obtained by the impedance component method and the genetic algorithm mainly lied in that the distal resistance had a larger increase. Conclusions There are still differences between the pressure data calculated by the parameters identified by the above three methods and the actual data, which are considered as modeling errors, source data errors and calculation errors. The impedance modulus curve method has a certain effect in distinguishing changes of the proximal and distal resistances, but there exist large errors in identification of some parameters. The impedance component method can identify the parameters, but this method is unstable with large calculation errors. Genetic algorithm can obtain a better approximate solution, but it has certain problems in distinguishing vertebral artery stenosis. The combination of impedance modulus curve method and genetic algorithm may play a better role in future application of this model for disease diagnosis.
Abstract:Objective To analyze mechanical properties of stent retrievers with different structures, and provide theoretical support for the design and clinical selection of stent retrievers. Methods Three kinds of stent retrievers with different structures (B3, K4, X) were evaluated by finite element analysis and in vitro simulation experiment. The analytic parameters were radial support force, withdrawal force and thrombosis state during the thrombotomy test. Results The radial support forces of B3, K4, X stent retrievers obtained from the experiment were 0.48 N, 0.43 N, 0.51 N, respectively. The larger the crimping distance, the greater the radial support force of stent retrievers. The radial support force of the stent increased significantly when the crimping distance was larger than 3 mm. The simulated thrombus removal experiment results showed that the peak withdrawal forces of B3, K4, X stent retrievers were 0.410 N, 0.451N, 0.501 N, respectively. The experimental results were consistent with the finite element analysis results. Conclusion sBoth the experimental results and the finite element results showed that the X stent has better mechanical properties. This method can be used as an analytic method to evaluate performance of the stent retrievers, and provide references for performance improvement and development of the stent retrievers.
Abstract:Objective To investigate platelet aggregation on glass surface under physiological flow condition. Methods The polydimethylsiloxane (PDMS)-glass microchannel chips were fabricated by soft lithography. Anti-coagulant human peripheral whole blood was flowed through the microchannel chip at flow shear rate of 300 s-1 and 1 500 s-1, respectively. The fluorescence images of platelet aggregates formed on glass surface at the bottom of the microchannel were captured after 150 s using an inverted fluorescence microscope. The number of platelet aggregates, average size, surface coverage and average fluorescence intensity were quantified by image analysis. The glass surface was treated with oxygen plasma, BSA blocking or collagen modification to establish different surfaces for platelet aggregation. The hematocrit (Hct) of blood sample was adjusted, and the whole blood was treated with different anti-platelet agents. The platelet aggregation on glass surface was observed under the above experimental conditions. The platelet aggregations in healthy people and diabetic patients were also analyzed. Results Under the flow condition, platelet aggregation on glass surface was three-dimensional. Platelet aggregation was dependent on wall shear rate, the hydrophilicity of glass surface and Hct, and was mainly regulated by GPIIb/IIIa-fibrinogen and ADP-P2Y12 receptor pathways. The aggregation of platelets on the glass surface could also reflect the high activity of platelets in diabetic patients. Conclusions At the flow conditions of 300 s-1 and 1 500 s-1, platelet aggregation on glass surface is related to flow rate, protein adsorption, platelet related receptors and platelet activation state. In this study, a new model for microfluidic platelet function analysis without additional adhesion protein modification was established, and it could be used for clinical evaluation of platelet function.
Abstract:Objective From the perspective of biophysics and immunology, the effects of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on biophysical characteristics, cytoskeleton and migration ability of mouse derived dendritic cells (DCs) were analyzed, so as to explore the effect of ω-3 polyunsaturated fatty acids (ω-3 PUFAs) on immune function of DCs and its potential mechanism. Methods The bone marrow-derived monocytes from C57BL/6J mice were isolated and induced to differentiate into immature dendritic cells (imDCs) by 20 ng/mL recombinant murine granulocyte-macrophage colony-stimulating factor (rmGM-CSF) and 10 ng/mL recombinant mouse interleukin-4 (rmIL-4), After 6 days, 100 ng/mL lipopolysaccharide was added to induce mature dendritic cells (mDCs). Further the morphological observation and positive rate of CD11c in imDCs and mDCs were analyzed, Then at different concentrations of EPA and DHA (0-60 μmol/L), the cell viability and apoptosis of DCs were detected by cell counting kit-8 (CCK-8) kit and flow cytometry. After the optimal concentration of EPA and DHA were determined, the changes of the membrane fluidity, electrophoretic mobility (EPM) and osmotic fragility of DCs were separately detected by the fluorescence polarization, cell electrophoresis and concentration gradient. The expression of filamentous actin (F-actin) was detected by the immunofluorescence. Finally, the migration ability of DCs was detected by the Transwell system. Results The positive rate of CD11c in DCs was about 80%. The viability of DCs decreased in a dose-dependent manner under the action of EPA and DHA of different concentrations, which didn’t induce the apoptosis of DCs. Under the action of 50 μmol/L EPA and DHA, the osmotic fragility and EPM of DCs significantly decreased, and the membrane fluidity significantly increased. The expression of F-actin in DCs obviously increased, and the migration rate of cells obviously decreased. Conclusions ω-3 PUFAs may affect the cytoskeleton structure and biophysical characteristics of DCs, inhibit the migration, and then affect its immune function.
Abstract:Objective For the system of two single-walled carbon nanotubes (CNTs) placed in parallel onto a cell membrane, effects of the interaction between carbon nanotubes on wrapping manner of carbon tubes by the membrane were investigated, and the energy-optimized configurations were obtained. Methods A physical model for membrane-wrapped CNTs considering the interaction between two CNTs, and parameters describing the morphology of cell membrane and positions of CNTs were introduced. The Helfrich model based on continuum mechanics was used to calculate the membrane’s bending energy and the Lennard-Jones potential was introduced to describe the interaction between CNTs. Free energy of the system at different distances of NTs was calculated by the look-up table method, and the typical configurations of the membrane-wrapped CNTs was obtained. Results Compared with the case wherein the interaction between CNTs was not considered, the free energy profile of the system significantly changed. Deep well appeared on energy curve, when the distance between CNTs of carbon was 0.3 times of the tube diameter; as the distance between CNTs increased, the energy returned to the case wherein the interaction between CNTs was not considered. Conclusions With introduction of the interaction between CNTs, the wrapping manner of CNTs by the cell membrane changed, and the two CNTs tended to contact during their endocytosis. These results provide theoretical references for understanding and developing novel nanotube-based system for drug delivery.
Abstract:Objective To propose a method for determing cell Poisson’s ratio based on micropipette aspiration technique. Methods Based on the assumption of deformation symmetry, the analytical expression between Poisson’s ratio and the amount of deformation was derived by extracting the extrusion deformation characteristics of the cells under micropipette aspiration according to the generalized Hooke’s law. The accurate determination of Poisson’s ratio of cells was realized according to position changes of markers on the surface of cell membrane. ResultsThe Poisson’s ratio of LNCaP cells in prostate cancer cells was measured. The result showed that the Poisson’s ratio of LNCaP cells was between 0.44 and 0.46, with an average value of 0.45. The influence of the location of the same cell feature points on calculation results of Poisson’s ratio was within the error range of 1.6%. Conclusions This method is simple and feasible, can improve the measurement accuracy of Poisson’s ratio of cells, and is helpful for cell detection and screening by using cell mechanical properties in clinic.
Abstract:Objective In view of the situation that tracheal atrophy causes the overall airway size to become smaller in the elderly, effects of the airway wall surface on reconstruction of a narrow airway and the airflow field under different respiratory conditions were investigated. Methods A three-dimensional (3D) model of human airway was established by using Mimics, and flow field in the airway was simulated by computational fluid dynamics (CFD) method. The inner wall pressure and the distribution of airflow were analyzed and compared under different breathing states. Results Under different respiratory states, the pressure of endotracheal wall was relatively uniform in the endotracheal wall, but decreased significantly in air inlet of the bronchial stenosis segment, and reached negative pressure near the narrowest area. The airflow velocity decreased from the center of the pipe to the boundary layer, and the velocity reached the maximum at the narrow area. Vortex was generated when airflow passed through the narrow area, and the larger the inlet flow velocity was, the larger the positive pressure and negative pressure were, the more obvious the pressure drop at the narrow area was, and the more obvious the vortex phenomenon was. Conclusions The constriction of the airway stenosis area caused by negative pressure will lead to the patient’s dyspnea, and the eddy current will cause the airway wall to be affected by the aerodynamic shear stress and may damage the airway wall mucosa. Therefore, understanding of the pressure distribution and velocity distribution in the narrow airway can provide references for clinical diagnosis and treatment of such diseased airways.
Abstract:Objective To propose an airbag-type helmet cushioning lining structure and analyze its protective effect on head injury of two-wheeled bicycle riders. Methods The airbag lining was applied to two typical two-wheeled bicycle helmets for bicycles (half helmets) and motorcycles (full helmets). Then kinematic and biomechanical responses of the human head model were predicted from impact simulations under test conditions of the standard GB 24429-2009 and the regulations ECE R22.05, and conventional expanded polystyrene (EPS) helmets were compared from the perspective of skull fracture and brain injury risk, so as to make comprehensive evaluation on protective performance of the airbag helmet. Results When the airbag pressure was 0.06 MPa, the relevant amount of human skull fracture under protection of airbag helmet (half/full helmet) was smaller than 120 g and 150 g, respectively; the risk of skull fracture was basically lower than 40%; the maximum principal strains of the brain were both smaller than 0.3, which indicated that the risk of mild brain injury was lower than 25%. Generally, the risk of human skull fracture and head injury under protection of airbag helmets was lower than that under protection of EPS helmets. Conclusions The airbag helmet designed in this study has a good protective effect, which can give attention to the protection of both skull fracture and head injury, providing a basic example for the design of novel helmet. Injury risk analysis can also provide the preliminary reference for emergency diagnosis on head injury of cyclists.
Abstract:：Objective To establish a mechanical model with times of laser treatment as the independent variable in treatment process of rabbit ear hypertrophic scar (HPS) by combining experimental research and numerical simulation, so as to evaluate the curative effect of HPS. Methods Firstly, the HPS model of rabbit ear was established by CO2 laser instrument, and then the HPS was treated for continuous three times by pulsed dye laser (PDL) combined with CO2 lattice laser. After each treatment, the uniaxial compressive mechanical properties of HPS were tested to fit Ogden hyperelastic model to obtain mechanical parameters of HPS during the treatment. The functional relationship between mechanical parameters of HPS and times of laser treatment was established by LM optimization algorithm. Results Mechanical parameters of HPS increased with the increase of laser treatment times, and gradually became a constant, namely, mechanical parameters of normal skin. With the increase of laser treatment times, the growth ratio of HPS mechanical parameters gradually decreased. The initial growth ratio was 60% and decreased to 4.09% after three times of treatment. Conclusions The initial curative effect of laser therapy is the most obvious, and with the relief of symptoms, the effect of single laser therapy is no longer significant.
Abstract:Objective To analyze interface stress of cemented tibial prosthesis platform and determine the interface stress damage area, so as to provide references for stress failure of tibial platform in clinical single condylar replacement. Methods The full cycle gait was simulated by human dynamics software to obtain the load-bearing condition of knee joint. A complete model of the knee joint was established by medical imaging and three-dimensional (3D) reconstruction software, and unicompartmental replacement was performed. The distribution of interfacial stress of tibial prosthesis platform after single condylar replacement was analyzed by finite element method. ResultsIn gait, force and angle of the knee joint changed periodically with time, a cycle lasted 1.3 s, and the peak of knee joint resultant force was 760 N. The maximum shear stress of the interface was 11.82 MPa and the maximum tensile stress was 6.849 MPa, both occurred at inner front end of the corner of prosthesis cement interface. The maximum interface stress of titanium alloy prosthesis was lower than that of stainless steel prosthesis. Conclusions The decrease in elastic modulus of prosthesis can reduce the maximum principal stress at the interface. Considering the interface stress, titanium alloy prosthesis is better than stainless steel prosthesis. The area of tibial prosthetic platform interface damage is mainly at the medial anterior and posterior corners and lateral middle ends,so improving the ability of prosthesis cement bonding in this area can prevent the loosening of tibial prosthesis of unicompartmental knee joint.The findings have practical implications for the prevention of tibial prosthetic platform loosening after unicompartmental knee arthroplasty in clinic.
Abstract:Objective To compare and analyze biomechanical stability of Ethibond thread suture and threaded anchor for fixing inferior pole fracture of the patella using the finite element method. Methods CT images of the knee joint from a healthy adult volunteer were selected and the inferior patella fracture model was established, then the three-dimensional (3D) models of fracture fixation with Ethibond thread suture and threaded anchor were established. Stress and displacement distributions of each fixiation model at different knee flextion angles were analyzed. Results In the range of 0°-90°, as knee flexion angle increased, the maximum stress and maximum displacement also increased. At the same knee flexion angle, threaded anchor fixation had the highest stress level, and Ethibond thread suture had the lowest stress level and the most uniform stress distributions. The displacement deformation of Ethibond thread suture was the largest, and the displacement deformation of threaded anchor fixation was the smallest. Conclusions The maximum displacement of the seam suture around patellar tendon with Ethibond suture is relatively moderate, and its maximum stress is relatively small, which is a reliable method for fixing inferior pole fracture of the patella in clinic.
Abstract:Objective To study mechanical properties of traditional trajectory (TT) and modified cortical bone trajectory (MCBT) on osteoporotic vertebrae through finite element analysis. Methods The three-dimensional model of L4 segment was established, and pedicle screw (PS) (diameter 6.0 mm, length 45 mm) and MCBT screw (diameter 4.5 mm, length 40 mm) were placed on both sides of the lumbar spine. The pull-out strength and the load-displacement ratio of screws in two different screw trajectories under up, down, left, right working conditions were analyzed, and the stability between the screw and vertebral body under osteoporotic conditions was evaluated. Results Compared with TT, the pull-out strength of MCBT screw was increased by 13.1%. Compared with PS, the load-displacement ratio of MCBT screw under up, down and left working conditions was increased by 57.2%, 32.4%, and 31.6%. Under right working condition, although the load-displacement ratio of MCBT screw was higher than that of PS, no statistical difference was found. The load-displacement ratio of vertebral body in MCBT group under lateral bending and axial rotation was significantly higher than that in TT group. The load-displacement ratio of vertebral body in MCBT group under flexion was lower than that in TT group. Although the load-displacement ratio of vertebral body in MCBT group under extension was higher that that in TT group, no statistical difference was found. Conclusions MCBT is superior to TT in pull-out strength, screw stability and vertebral body stability under lateral bending and axial rotation, but its vertebral body stability under flexion and extension was weaker than that of TT. The research findings demonstrate the superiority of MCBT under osteoporotic conditions and lay the foundation for clinical application of MCBT.
Abstract:Objective To evaluate the efficacy of additive manufacturing scoliosis orthosis, by simulation on interaction of the bone, trunk and orthosis using finite element method. Methods Combined with CT data of the patients, three-dimensional (3D) scanning model of the trunk and full length X-ray of the spine, the bone-trunk-orthosis finite element model was established and proved to be effective. The change and development trend of Cobb angle of the main thoracic scoliosis was calculated under different boundary and load conditions. Results The treatment effect of the additive manufacturing scoliosis orthosis was good. With the increase of orthotic preload, the improvement of Cobb angle and pelvic tilt was more obvious. The Cobb angle was expected to decrease by 6.18° after application of 70 N preload to the orthosis for 6 months. In the case of increasing system stiffness, Cobb angle improvement was not obvious and became even worse. Conclusions Additive manufacturing scoliosis orthosis is effective for treating adolescents with immature bones, while for patients with mature or degenerative bones, its treatment effect is poor.
Abstract:Objective The traditional circular external fixation structure was redesigned to make it more suitable for intraarticular Pilon fracture fixation. The stability of the horseshoe annular external fixator was verified by analyzing fracture displacement of the Pilon bone after fixation with the external fixator under loading.MethodsAO-C2 Pilon fracture model was prepared by pendulum saw according to predetermined osteotomy line, and then fixed by horseshoe ring external fixator. The fixed ankle model was subjected to axial loading on mechanical test machine. The axial force loading mode was from 0 N to 150 N, 300 N and 450 N successively. The displacement changes of fracture blocks in X (left-right), Y (up-down) and Z (anterior-posterior) axis during axial loading were recorded by dynamic capture instrument.ResultsThe overall left-right, up-down and anterior-posterior displacement of the fibula ranged from 0.32 mm to 0.70 mm, -0.27 mm to -0.23 mm and 0.23mm to 0.32 mm, and the maximum difference was 0.09 mm. The overall left-right, up-down and anterior-posterior displacement of medial malleolus fracture in the tibia range from 0.02 mm to 0.14 mm, -0.80 mm to -0.19 mm and -0.78 mm to -0.13mm.The overall left-right, up-down and anterior-posterior displacement of lateral malleolus fracture in the tibia ranged from -0.07 mm to 0.05 mm, -0.36 mm to -0.03 mm, 0.27 mm to 0.47 mm.ConclusionsThe horseshoe ring external fixator can not only stabilize the fracture end, but also produce micromotion which is beneficial to fracture healing, which accords with biomechanical characteristics of fracture healing. The external fixator structure is simple, suitable for the treatment of Pilon fracture, and worthy of popularization and application.
Abstract:Objective To design a novel biodegradable intestinal anastomosis stent and explore the relationship between pressure distance and biomechanical properties of the anastomosis, so as to provide new ideas and methods for compression anastomosis of intestinal tissues. Methods A compression anastomosis stent was designed for reconstruction of intestinal tissues, and the finite element model of compression anastomosis of intestinal tissues was established to investigate the relationship between pressurized distance (2, 1.6, 1.2, 0.8 mm) and tissue stress of the stent. The anastomosis effect of intestinal tissue under different pressurized distances was analyzed by the test of tear-off force and burst pressure. Results Biomechanical properties of the intestinal anastomosis were the best when the pressurized distance was 1.2 mm, and its maximum tensile strength reached 0.77 MPa. The tear-off force and burst pressure of tissues were (25.80±1.82) N and (12.30±0.26) kPa, respectively. The optimal intestinal anastomosis was achieved when tissues were compressed to 60% of the original thickness. Conclusions The biodegradable intestinal stent designed in this study can successfully achieve compression anastomosis of intestinal tissues, which provides theoretical references for the development and application of novel biodegradable compression anastomosis devices.
Abstract:Objective To explore the differences between the result of static optimization (SO) and computational muscle control (CMC) algorithms for estimating muscle forces, so as to provide references for researchers to choose the appropriate algorithm and make horizontal comparison of the results from different studies. Methods Targeting at a single gait cycle running at four different speeds, SO and CMC algorithms were used to calculate forces and activations of the major muscles in lower limbs, and the results were compared and analyzed. Results Among the 10 major muscles participating in running, except for anterior tibial and rectus femoris, muscle forces and muscle activations solved by the two algorithms had similar curves with correlation coefficients more than 0.91, and the peak value of muscle forces solved by SO was higher and the positions of peak muscle activation had a 10 ms delay. Conclusions In movement analysis, if the research focuses on the timing of muscle forces and the contribution ratios among different muscles, there is not too big difference and SO algorithm is recommended for its simplicity and efficiency. For horizontal comparison of muscle forces and muscle activations estimated by SO and CMC algorithms in different studies, the differences between the two algorithms should be considered.
Abstract:Objective According to clinical demand of quantification evaluation on flat foot and high arch, an intelligent and rapid method to diagnose arch shape based on principal component analysis (PCA) of plantar pressure is proposed, and its clinic validity is tested. Methods Volunteers diagnozed as abnormal arch and healthy arch were included in this study, and a portable intelligent arch test system was designed and developed. By adopting thin-firm piezoresistive sensor array with 44 rows, 52 columns of sensing units, the system could collect plantar pressure distribution data from the subjects under static standing. Foot axis could be fitted automatically by using the self-programmed PCA, so that foot diagnosis was completed with diagnostic report. The plantar pressure results from the system were compared with those from the existing plantar pressure acquisition device, so as to verify precision of collected data. The accuracy of the diagnosis algorithm for flat foot, high arch and healthy foot was verified through comparison with clinical diagnosis. Results The result of the system had a good correlation with that of the existing plantar pressure acquisition device, the deviation of contact area acquired by the system was smaller than 3.2%, and the angle deviation of the fitted foot axis with clinically defined angel was less than 1°. The system was capable of making diagnosis on arch shape that was 92.6% consistent with the clinical diagnosis. Conclusions PCA is introduced to automatically fit foot axis to achieve the purpose of fast and accurate extraction of foot arch information. The method can be used to assist clinical diagnosis of flat foot and high arch foot, and contribute to quantative analysis on foot arch deformity and its pathogenesis study.
Abstract:Objective Through the evaluation of subjective comfort and plantar pressure during walking, with the integration of subjective perception and biomechanical indexes, to explore the effect of personalized insole on foot perception and ankle function of normal foot. Methods Sixteen male subjects with normal foot types were recruited, and the visual analog scale (VAS) was used to evaluate the differences of subjective comfort index under the intervention of minimalist shoes and personalized insoles, and changes of time and plantar pressures at each stage of barefoot walking and walking with minimalist shoes and personalized insoles were analyzed by single factor repeated measurement variance. Multiple linear regression was used to screen the main indexes which affected the overall comfort of shoes during walking with minimalist shoes and personalized insoles. Results For measurement of plantar pressures, the gait support buffer stage of walking with shoes was higher than that of barefoot walking or walking with minimalist shoes（P<0.05）, and the dynamic arch index (AI) of walking with personalized insole was higher than that of walking with minimalist shoes and barefoot walking（P<0.05）. The dynamic AI during walking with minimalist shoes was higher than that of barefoot walking（P<0.05）, and the proportion of foot impulse during walking with personalized insoles was higher than that during barefoot walking（P<0.05）. When wearing shoes, the average slope for center of pressure (COP) trajectory was lower than that of barefoot walking, and the slope of COP trajectory of walking with personalized insoles was lower than that of walking with minimalist shoes（P<0.05）. For evaluation of subjective comfort, the overall comfort, heel cushioning, front foot cushioning, arch support, forefoot wrapping and foot control of walking with personalized insoles were higher than those of walking with minimalist shoes（P<0.05）. The results of linear regression showed that arch support and the proportion of middle foot impulse had significant influences on the overall comfort of walking with shoes（P<0.05）. Conclusions Personalized insoles can improve the overall comfort of normal foot mainly through the influence of foot arch. After personalized insole is added, the cushioning ability and foot control ability of walking are improved, and force deviation of the foot on coronal axis is reduced. Feet-insoles-shoes jointly affect the perception of human feet, and insoles should be selected in many aspects, such as foot types, shoe conditions and insole materials.
Abstract:Objective To compare the effects of hip abductor fatigue on postural stability and neuromuscular control in different gender groups during single-leg side-jump landing. Methods Twenty male and twenty female adults were required to execute single-leg side-jump landing before and after hip abductor fatigue protocol. The center of pressure (COP), ground reaction force (GRF), lower extremity kinematics, joint moment, muscle activity were compared. Results For both males and females after fatigue, the maximum displacements and average velocities of COP decreased, and the peak angles of hip abduction and ankle eversion increased, and the peak torques of ankle inversion increased. At 200 ms pre-landing, the activiation of rectus femoris, biceps femoris, tibialis anterior, peroneus longus were lower in male than that in female. At 200 ms post-landing, the activiation of biceps femoris in male was lower than that in female after fatigue. Conclusions The postural stability in frontal plane decreased after hip abductor fatigue. The frontal plane control of hip joint and ankle joint was weakened, which might increase the risk of joint injury. There are differences in postural strategies for different genders, indicating that gender difference in the mechanism of lower limb joint injury is worth of further investigation.
Abstract:Objective To analyze muscle pre-activation and surface electromyography (sEMG) characteristics of knee and ankle joints of long-term Tai Chi practitioners during brush-knee twist-step and normal walking, and explore the neuromuscular control strategies of Tai Chi to prevent falls. Methods Vicon motion capture system, Kistler force plate, and Noraxon sEMG system were synchronously used to collect the EMG signals of the rectus femoris, biceps femoris, tibialis anterior muscle, lateral head of gastrocnemius and body posture information during brush-knee twist-step and normal walking. The pre-activation and co-contraction of knee and ankle joints were calculated by integrated EMG of the rectus femoris/biceps femoris, tibial anterior/lateral gastrocnemius muscles. Results Compared with normal walking, the average time of brush-knee twist-step in four phases was significantly increased. There was a significant difference in the percentage of time in four phases. The knee joint co-contraction level and pre-activation level decreased, and the ankle joint co-contraction level and pre-activation level increased. Conclusions Long-term Tai Chi exercises may increase the activation level of the muscles around knee joints and enhance the synergy in muscle groups to help stabilize the joint. The results provide references for rehabilitation assessment and training of neuromuscular control disorders.
Abstract:Objective To explore the effects from different contact areas of the instrument causing trauma on biomechanical response parameters of rabbit skull fractures under quasi-static compression conditions. Methods The rabbits were divided into the scalp preservation group and scalp removal group. Each group was subdivided into 3 mm group, 6 mm group, 9 mm group according to contact diameter of the instrument causing trauma. There were 9 rabbits in each group, 54 rabbits in total. All rabbits were put to death by over anesthesia and made into a skull compression model. An electronic universal material testing machine was used to perform quasi-static compression of rabbit skulls to fractures, and biomechanical response parameters such as ultimate load, deformation under ultimate load and compressive strength of rabbit skulls in each group were detected. Results The differences in ultimate load, deformation under ultimate load, and compressive strength of rabbit skulls in scalp preservation group and scalp removal group under different contact areas were statistically significant. The ultimate load was positively correlated with the contact area, and the compressive strength was negatively correlated with the contact area. No correlation was found between deformation under ultimate load and contact area. For scalp preservation group and scalp removal group, the difference in deformation under ultimate load was statistically significant in the 3 mm contact surface diameter group, and there was no statistical significance in the other groups. Conclusions The contact area is positively correlated with the ultimate load of rabbit skull fracture and negatively correlated with compressive strength, while it has no correlation with deformation under ultimate load and is unrelated to whether the scalp is removed.
Abstract:Objective To investigate the clinical effect of acupuncture combined with five-step reduction method for treating intervertebral disc herniation (IDH). Methods A total of 80 patients meeting the requirement of IDH were selected and randomly divided into control group, acupuncture group, five-step reduction massage group and acupuncture combined five-step reduction method group. Each group included 20 subjects, who received two courses of treatment for 1 month. After the treatment, the therapeutic effects of acupuncture, five-step reduction massage, acupuncture combined with five-step reduction massage were evaluated. The observation indicators included back pain JOA scale, McGill pain scale, quality of life QOL scale, gravitational moment and muscle moment. Results After the intervention treatment, compared with control group, the JOA, McGill, QOL, gravitational moment and muscle moment of patients in acupuncture group, five-step reduction massage group, acupuncture combined five-step reduction method group were significantly improved (P＜0.05), and the improvement effect in combined treatment group was more significant (P＜0.01). Conclusions Acupuncture combined with five-step reduction method significantly improved the symptoms of lumbar disc herniation in swimmers.
Abstract:Patellofemoral pain syndrome (PFPS) has been attracting more and more attention in the field of rehabilitation treatment due to its high incidence rate and low cure rate. Researches show that the abnormal anatomy, muscle activity changes due to pain and insufficient muscle strength in patients with PFPS can cause wrong movement patterns of lower limb joints, which will lead to aggravation of the disease and is not conducive to the rehabilitation of patients. Movement patterns of the hip, knee, ankle joints can be improved by exercise therapy, taping, neuromuscular training and joint orthosis, thus to reduce the pain. In this paper, the movement pattern characteristics of patients with PFPS and the corresponding rehabilitation treatment method were summarized, so as to provide references for the rehabilitation of PFPS.
Abstract:Periodontium is mechanoresponsive to multiple types of mechanical stimuli like occlusal and orthodontic force and reacts quickly. It is widely used as the loading subject in researches regarding dental mechanical force models both in vivo and in vitro. This review summarized various animal models and cell culture loading methods (including static gravity approach, centrifugation approach, vibration approach, cyclical tension approach, fluid flow approach)，as well as parameters for periodontium in recent years, so as to provide references for the study of periodontal mechanoresponsive mechanism and the development of new clinical therapies.
Abstract:Blood is an important component of living organism which is responsible for material transportation. The microenvironment of blood flow plays an important role in physiological and pathological processes of angiogenesis and cardiac development, erythrocytes aggregation and blood viscosity, tumor metastasis and atherosclerosis. Besides, micro-fluid environment significantly affects drug delivery, cell screening, and artificial organ design. Thus, the measurement and quantitative analysis of micro-fluid contribute to the biomedical engineering filed. Micro-particle imaging velocimetry (Micro-PIV) combines conventional PIV with microscopy technique. Correlation analysis is conducted in two groups of images captured by high speed camera at different time intervals, and the velocity profiles in micro-fluid environment are successfully measured. Compared with other velocity measurement methods, Micro-PIV has high temporal resolution and spatial resolution. The main setup of Micro-PIV and its principle analysis method were introduced in this review. Recent studies of Micro-PIV applications in biomedical engineering field were then summarized. Moreover, the drawbacks of Micro-PIV technique and prospect of its applications were discussed.
Abstract:With the multi-directional differentiation potential such as osteogenic differentiation, chondrogenic differentiation and adipogenic differentiation, mesenchymal stem cells (MSCs) have been widely used in basic research and clinical applications. The differentiation potential of MSCs is altered during senescence. Osteogenic differentiation potential decreases, while the lipogenic differentiation potential increases in aging MSCs. Changes in differentiation potential of MSCs during senescence are accompanied with cell physical heterogeneity variation (cell size, cell stiffness and nucleoplasmic ratio). Studies have shown that changes in physical heterogeneity of stem cells may be a key factor leading to the differences in differentiation potential of MSCs. Therefore, studies on physical heterogeneity variation of MSCs during senescence will provide a new research direction in fate prediction of stem cell. In this review, the effects of physical heterogeneity variation on differentiation potential of MSCs were summarized, and the corresponding mechanism was also discussed.