Abstract:Rehabilitation engineering can not only improve life quality of the elder and people with disability, but also reduce burdens of the society and family for care at the same time. With the development of economy and improvement of life quality, rehabilitation engineering will be raised to a new level. Biomechanics provides fundamental basis for the design and assembly of rehabilitation products. As the main reason for rehabilitation is to maximally restore the lost function of body support and exercise, it is important to understand the force transmission and interaction between the body and supporting device. Through biomechanical research, optimized assistive technology for rehabilitation and training program can be designed. This paper will review the major focus on biomechanics research in rehabilitation engineering, including body support interfacial biomechanics, musculoskeletal kinematics and kinetics, finding appropriate control signals, and developing advanced materials, so as to provide theoretical basis for the development of rehabilitation products.

Abstract:Objective To study the effects of wedged insoles at different location on loads and motion of the knee joint. Methods Ten healthy female subjects participated in this experiment. Their gait patterns were assessed as six different wedged insoles and one controlled flat insole. The gait was monitored to study the kinetic changes in joint by using Motion Analysis System and force platforms. One way repeated measurement ANOVA was used to analyze the influences. Results Compared with the control group, the first peak of knee adduction moment was significant reduced by using medial forefoot wedged insole (P<0.05). The second peak of knee adduction moment was significantly reduced by both lateral forefoot wedged insole (P<0.05) and full-length lateral wedged insole (P<0.05). Conclusions The wedged insoles can effectively decrease the knee adduction moment in stance phase during walking, which will help to design an appropriate insole to reduce the knee pain due to osteoarthritis.

Abstract:Objective To monitor the exercise load in daily life activities, a reliable method to estimate the real-time plantar pressure based only on a few sensors was presented. Methods Pedar-X pressure insoles were applied to collect plantar pressures from 10 healthy young adults performing 5 typical motions (vertical jump-landing, level walking, level running, stair ascending and stair descending). Stepwise linear regression was performed to reconstruct a mathematic model of calculating the foot force for each style of the motion based on 99 individual pressure data. Then these models were validated by comparing the plantar pressures measured by Pedar-X system and the estimated values by these models when other 4 subjects conducted the same 5 motions and the continuous motion composed of the 5 motions. Results Regardless of the single motion or continuous motion, the foot force calculated by each model for each motion, as well as that calculated by level walking model for each motion were almost the same as the data measured by Pedar-X system. In addition, there was no significant difference between the estimated values by each motion model and level walking model. Conclusions The foot force in daily life activities can be monitored effectively by level walking model with only 5 pressure sensors placed under T1, M2, M3, HM and HL region of the foot.

Abstract:Objective To test the mechanical properties such as stiffness and strength of a new proximal femoral nail antirotation (PFNA) with three-dimensional finite element method and analyze its stress and strain distributions before and after the femur intertrochanteric fracture healing. Methods The three-dimensional model of PFNA was established by UG NX and the CT images were preprocessed by MIMICS. The finite element model of intertrochanteric fracture and fracture healing were developed for numerical simulation. Results Before the fracture healing, the maximal Von Mises stress was up to 663 Mpa at the location of fracture and that near the locking bolt was only 113 MPa after PFNA implanted. After the fracture healing, the maximal Von Mises stress occurred at the blade-nail interface. Obvious stress concentrations appeared near the locking bolt on the femur shaft. Conclusions The PFNA should be taken out because the femur shaft fracture often occurred at the location of the locking bolt after healing.

Abstract:Objective To investigate the acute effect of local vibration stimulus with low frequency on hand control ability, flexibility, grip strength, and muscle EMG activity. Methods 10 subjects in this study held a vibrator for 20 seconds with isometric contraction at the vibration frequency of 12.5 Hz (vibration group, VIB) or with only isometric contraction (control group, CON). The same procedure measurement, including control ability, flexibility, grip strength, and muscle activity, were recorded both at pre-stimulus (pre-test) and 60-second after stimulus (post-test), respectively. Paired-t test was used to compare the values between pre-test and post-test and the changing rate between groups. Results The control ability and flexibility in pre-post test showed significant improvement after VIB intervention in VIB (P＜0.05). The changing rate of grip strength and EMG in VIB was significantly higher than those in CON (P＜0.05). Conclusions Acute local vibration stimulus with low frequency can be used to improve the hand control ability and flexibility for those who need better hand functional ability in the future.

Abstract:Objective To explore biomechanical assessment for the effects on vibration against bone loss by investigating the relationship between material distribution and mechanical properties of rat femur cortical bone based on Micro CT. Methods 35 rats were randomly divided into intermittent vibration groups with the interval of 1, 3, 5, 7 days, and continuous vibration group, respectively. Tail suspended model of disuse osteoporosis was set up. All rats were loaded with mechanical vibration of 35 Hz and 0.3 g, and killed after 8 weeks. Micro CT scanning of the left femur of each rat was performed. Three-dimensional finite element model of the cortical bone was established to calculate the apparent and tissue-level mechanical parameters. Principal components (PCs) were extracted from material distribution, intermittent days and volume fraction by principal components analysis (PCA). Results The PCA revealed the three independent components that could fully explaine the variability of cortical bone characteristics under vibration. The linear regression equations were also created between the material property and the apparent and tissue-level mechanical properties, respectively. Mechanical properties of the cortical bone were influenced by material distribution mostly, and the volume fraction and intermittent days were next in importance. Conclusions The cortical bone material distribution can reflect changes in its mechanical properties, and the bone strength could be assessed by establishing the linear relationship, which could provide a theoretical basis for osteoporosis prevention and treatment as well as the assessment on its rehabilitation process.

Abstract:Objective To investigate the interface pressure on above knee residual limb at mid stance during walking，so as to provide basis for the establishment of measurement and evaluation system for the above-knee socket. Methods Based on CT images of the femur, soft tissue and above knee socket of the patient with residual limb, the three-dimensional model was first built, and then to assemble them according to changes of the hip joint in a gait cycle. The finite element model was then established to simulate the loading conditions at mid stance during a gait cycle, and the effect of pre-stress was investigated by nonlinear large deformation analysis. Results If considering the effects such as joint changes and pre-stress, the maximum value by calculation for normal interface pressure distributed on the terminal of stump was 257.66 kPa, which could better match the maximum stress actually measured by the Mflex Sensor Distributing System as 258.9 kPa. Conclusions The three-dimensional finite element model with considering the factors such as hip joint change, pre-stress and friction could effectively simulate the stress condition of patient with residual limb during walking.

Abstract:Objective To design a mouse device based on surface EMG signals of the temporalis for people who suffered with paraplegia, upper limb disability or impaired hand function to be able to operate the mouse. Methods A control method for mouse operation based on surface EMG was presented. Through analysis and test, facial surface EMG signals of the temporalis were selected as the control signal and with the bite as a trigger action. EMG signals with different characteristics could be generated from the temporalis muscle according to different bite actions, and thus a mouse device controlled by the facial surface EMG signals from the temporalis was designed. Results The test proved that by using the device, subjects could control the mouse by a simple bite action. Conclusions The control method for mouse operation based on surface EMG is feasible，and the mouse device designed according to this method is valuable in practical application.

Abstract:Objective To investigate the effects of Tai Chi Chuan combined with vibration training on the excitability of α-motorneuron pool and γ-reflex arc. Methods 55 healthy college students were divided into Tai Chi Chuan + vibration training (TAV) group, Tai Chi Chuan training (TAI) group, vibration training (VB) group, and control group (CON) for 8 weeks with 3 times training per week. Each time at pre-and post-training, H-reflex and M-wave were recorded by electrical stimulus induced on soleus muscle. T-reflex was also collected by knocking on the Achill tendon. Results After 8-week training, the ratios of Hmax/Mmax and T-reflex/Mmax in VB group were significantly decreased (P<0.05), while the ratio of T-reflex/Mmax in TAV group was significantly increased (P<0.05), and the change percentage of T-reflex/Mmax was significantly higher than that in VB group (P<0.05). Conclusions Although the vibration training could decrease the resting excitability of α-motorneuron pool, the Tai Chi Chuan combined with vibration training could give the muscle spindle stronger excitement so as to further induce the high excitability of γ-reflex arc. It indicated that the Tai Chi Chuan combined with vibration training is feasible since the neural adaptation around peripheral neuron system could be induced after such kind of training.

Abstract:Objective To develop a microfluidic device with the adjustable concentration and pressure gradient for 3D cell culture in hydrogel and set up an in vitro model with the capability to closely simulate in vivo microenvironment for cell growth. Methods The microfluidic chip, with a middle channel for 3D cell culture and two side channels for delivering cell culture medium, was designed and fabricated using standard soft lithography and replica molding techniques. Its capability to generate concentration gradient, interstitial flow and image cell in situ was demonstrated. Results A simple microfluidic chip for 3D cell culture in hydrogel with the capability to generate the concentration and pressure gradient was obtained. At a flow rate of 2 μL?min-1 in each side channel, the concentration gradients remained constant after 3 h. The interstitial flow across the gel scaffold was generated by a 100 Pa pressure difference between two-side channels with the pressure gradient of 0.11 Pa/μm. Human adult dermal microvascular endothelial cells (HMVEC) were maintained in 3D culture with collagen type I and observed with confocal microscopy. Conclusions The microfluidic chip is simple and easy to operate and it can simulate the complicated microenvironment in vivo. The chip also allows the multiparameter control of microenvironment, facilitating the better understanding of interaction between cells and microenvironment.

Abstract:Objective To cross-link the porous biological ceramics and PVA hydrogel to form a double layer construction between the artificial cartilage and hard joint, and to analyze its morphologies and mechanical properties. Methods With hydroxyl apatite (HA) as the substrate, the porous hydroxyl apatite biological ceramics with different porosities were prepared by using NH4HCO3 crystal grains as the pore-formed material. The poly vinyl alcohol (PVA) and epoxypropane were used as the primary material and cross-linking agent, respectively. The PVA hydrogel with double layer construction was cross-linked and prepared on the porous biological ceramics surface. The fracture appearances of the test specimen section were characterized. The performances of anti tensile strength and anti-shear strength for PVA hydrogel were analyzed. Results The cross-linked PVA hydrogel could permeate in the biological ceramics substrate, and the union between ceramic substrate and PVA hydrogel performed well. With the porosity of the porous biological ceramics increasing, the tension load and shear load of the PVA hydrogel samples both increased, and with the average porosity of 70%, the samples’ biggest tension load and shear load were 153.61 N and 64.46 N, respectively. But the corresponding tensile strength and shear strength both decreased and with the average porsity of 70%, the samples’ biggest tensile strength and shear strength were 2.12 MPa and 1.13 MPa, respectively. The failure mode of both tension and shear tests for PVA hydrogel samples was due to the crack propagation, and the fracture morphologies showed that obvious cracks and internal defects appeared on the fracture surface, while the source of the crack and the direction of the crack propagation could be observed. Conclusions Considering the compression strength of porous biological ceramics, the permeation effect on the porous biological ceramic substrate with the average porosity of 50% is moderate to be used, which ensures the appropriate shear and tensile strength of PVA hydrogel samples and the compression strength of porous biological ceramic.

Abstract:Objective To prepare the porous NiTi alloy with good biocompatibility for jaw bone implantation and compare the amount of the nickel ion release from NiTi alloy with TiO2 or HA coatings, respectively. Methods The porous NiTi samples were fabricated by powder metallurgy and the morphological characteristics were observed by metallographic microscope and X ray dispersive spectroscopy (XRD). The elastic modulus and fracture strength of the porous NiTi samples were recorded after the compression test. By sol-gel method, TiO2 or HA coatings were obtained on the porous NiTi samples, and the amount of nickel ion release from the samples was measured at 1，3，7，15 d, respectively. Results The pores were interconnected with the pore size of 50~200 μm and ~50 μm. The porosities of porous NiTi samples ranged from (23.5±5.24)% to (38.8±1.82)%, the elastic modulus from (9.55±0.19) GPa to (4.28±0.32) GPa, the fracture strength from (133±6.75) MPa to (80.5±5.58) MPa (P<0.05). The amount of nickel ion release from porous NiTi samples with HA or TiO2 coatings were obviously lower than that of porous NiTi samples uncoated. There were no statistic differences between HA-coating group and TiO2-coating group(P>0.05). Conclusions The mechanical properties of porous NiTi alloy declined with the increase of pore-forming agent and porosity. Coating treatment could effectively inhibit the release of nickel ion from the porous NiTi alloy.

Abstract:Objective To improve the method used for traditional compression test to reflect the compressive elastic modulus of trabecular bone in proximal femur more accurately and investigate its biomechanical properties to provide experimental evidences for clinical treatment. Methods The properties of trabecular bone from normal cadaveric proximal femur(45~60 years old) were measured by the micro material mechanics testing system. Results The elastic modulus in the direction of principle compression and principle tension on trabecular bone were (335.26±183.85) MPa and (59.27±23.88) MPa, respectively. The biomechanical properties of trabecular bone in the direction of principle compression were significantly higher than those in its vertical direction.The displacement and strain distribution profiles under the loading were recorded, which showed to be asymmetric. Conclusions It is feasible to test the biomechanical properties of trabecular bone more accurately by the micro material mechanics testing system. The compressive properties of trabecular bone in proximal femur are obviously anisotropic and heterogeneous.

Abstract:Objective To establish patient-specific hexahedral finite element mesh model for the maxillofacial surgery. Methods A standard and common hexahedral finite element mesh model for the face soft tissue was first built by semi-automatic procedure, and the an individual facial hexahedral mesh was then generated by an example learning method based on volumetric mapping. Results It was convenient to generate a high quality patient-specific hexahedral mesh with geometric shape feature and mesh element quality preserved as much as possible with this method. Conclusions The new hexahedral mesh modeling method can provide high quality hexahedral mesh input for biomechanics analysis with good application prospect in many fields such as oral and maxillofacial surgery.

Abstract:Objective Try to set up a nonlinear lumped parameter model of intra-aorta pump by studying the relationship between the pressure difference and the blood flow rate at the head of the pump, so as to predict the hemodynamic parameters of the pump. Methods Only the parameters of the pump, without hemodynamic parameters of the circulating system, were used to esfablish the model. It was composed of a speed-controlled current source representing the flow rate driven by impeller, an internal resistant representing the resistance of the radial clearance, an inductance denoting the inertance of the blood. Results The model could simulate the physiological status of the heart under all the situations from pulmonary congestion to ventricular collapse. The characteristic equation of the pump was derived with parameters determined by experimental data in vitro. Conclusions To verify the accuracy of the model, the prediction value calculated from the model was compared with the one recorded from experiment in vitro. The results showed that the error in between was less than 5%, which indicated that this model could predict the pressure difference of the pump accurately.

Abstract:Objective To discuss the characteristics of flexor and extensor torque of the knee joint by carrying out isokinetic testing on women handball players in Guangdong Province, and to provide some isokinetic test data for the strength and physical training research on handball players. Methods Flexor and extensor of knee joint in fourteen players from Guangdong provincial handball team were measured by CON-TREX isokinetic testing system. Relative peak torque, hamstring/quadriceps ratio, total work, average power and fatigue index were selected to study the isokinetic characteristics of the women handball players’ knee joint. Independent t tests were employed to compare the results between flexor and extensor. Results For women handball players, at the velocity of 60°/s (low speed test)and 240°/s(high speed test), the relative extensor peak torque value was significantly greater than that of the flexor（P＜0.01）; at the velocity of 240°/s, the hamstring/quadriceps ratio was about 76%; at the velocity of 60°/s,　the total work and average power of the extensor was greater than that of the flexor（P＜0.01）; at the velocity of 240°/s, the total work and average power of the extensor in left knee joint were greater than that of the flexor（P＜0.05）; the range of fatigue index was from 0 to 0.49. Conclusions The maximum strength and speediness strength of extensor was greater than that of the flexor; at the velocity of 240°/s, the hamstring/quadriceps ratio of the knee joint was relatively lower, which showed that the speediness strength of flexor in knee joint was relatively low; the speediness strength and the working capability of the extensor in knee joint was greater than that of the flexor; the fatigue index of extensor and flexor of knee joint was relatively low, which may indicate that the level of strength stamina of extensor and flexor in knee joint was relatively low.

Abstract:Objective To investigate effects of orthoses and relative techniques applied in burn patients.Methods 20 customized orthoses used for 17 burn cases since the year 2008 were studied, and the effects and main technical points of the treatment were summarized based on the principle of such orthoses. The burn areas in these patients were at the neck, hand, ankle, foot and body trunk. The intervention time of using orthoses was at early stage of burn, recovery stage and late stage of rehabilitation, respectively. Results The review study showed that fitting the orthoses after burn could prevent the contracture of the joint, restrain scar casting, assist training to improve the range of motion of the joint. Conclusions According to the state of the burn patients, the use of well fitted orthoses could have obvious good clinic effect, which promotes the functionality recovery.

Abstract:Calcium is not only the important signaling molecule within and between bone cells, but also the primary component of extracellular matrix in bone. It has been demonstrated during the past over 100 years that mechanical stimulations can regulate the molecular signal transduction and intercellular communication in bone cells as well as the bone mineralization and resorption at tissue level, but further more researches are still needed to give insight into the mechanism of mechanical stimulation-induced bone remodeling. This paper will summarize the related works on the following aspects: (1) the primary experimental approaches for studying mechanical stimulation induced calcium response and transfer in osteoblasts, (2) the calcium sources and mechanism of calcium response in osteoblasts, (3) the intercellular calcium transfer pathways and (4) characteristic parameters of calcium response and transfer in osteoblasts. Finally, several potential research directions in this field are presented in the paper.