Irregular-Shaped Fe3O4 Nanoparticles-Mediated Magneto-Mecha nical Force for Killing Tumor Cell / 医用生物力学

Objective To investigate tumor cell killing effect of superparamagnetic Fe3O4 nanoparticles with cubic phase through magneto-mechanical force under a low-frequency vibrating magnetic field ( VMF). Methods A kind of strong magnetic and irregular-shaped Fe3O4 nanoparticles with cubic phase was synthesized by coprecipitation method. The Fe3O4 nanoparticles were exposed to a self-developed VMF and cell killing efficiency of the Fe3O4-mediated magneto-mechanical force was investigated. Results VMF alone had no effects on cell viability. After Fe3O4 nanoparticles were added, the cell viability significantly decreased with prolonging the VMF treatment time and increasing the Fe3O4 nanoparticle concentration. Lactate dehydrogenase released by damaged cells also increased with prolonging the VMF exposure time. Conclusions The irregular-shaped Fe3O4 nanoparticles can transfer magneto-mechanical force to tumor cells under VMF, cause structural damage of cells and result in cell death. The VMF generator developed in this study has simple structure and it is safe for use and convenient for operation. The developed magnetic nanoparticles and the corresponding cancer cell killing technique have the potential for clinical transformation.

Force Transmission Mode of Foot Ankle in Children with Down’s Syndrome During Standing / 医用生物力学

Objective To explore the joint contact force, ligament tensile force and force transmission mode of foot internal structure in Down’s syndrome child (DSC) during standing. Methods The finite element models of foot were constructed based on CT image data from one DSC and one typically developing child (TDC). The models were validated by plantar pressure measurement during static standing. To simulate foot force during standing, the ground reaction force and the triceps surae force were applied as the loading condition. Contact pressure of the tibiotalar, talonavicular and calcaneocuboid joints, tensile force of the spring and plantar calcaneocuboid ligaments, and force transmission mode in transverse tarsal joints were calculated and analyzed. Results The finite element models of foot were validated to be reliable. Compared with the TDC, the DSC showed higher contact pressure at the tibiotalar joint and lower contact pressure at the talonavicular joint. The tensile force of spring and plantar calcaneocuboid ligaments of DSC was 10 times and 58 times of TDC, respectively. The forces transmitted through both mediate and lateral columns in DSC were lower than those in TDC. Conclusions Abnormal contact pressure of the tibiotalar joint, larger tensile force of midfoot ligaments and smaller force of the transverse tarsal joint were found in DSC during standing. The abnormal alteration of stress patterns in foot internal structure of DSC should be fully considered in clinical rehabilitation, so as to provide theoretical references for screening and making intervention plans for early rehabilitation, as well as designing individualized orthopedic insoles.

Comparison of Muscle Activation and Co-Contraction Patterns for Trunk Muscles During Four-Point Hand-Knee and Hand-Foot Kneeling Positions / 医用生物力学

Objective To analyze the similarities and differences between four-point hand-knee position and hand-foot kneeling positions in trunk muscle activation and co-contraction, explore the possibility of hand-foot kneeling position as core stabilization exercises, so as to provide suggestions for actual training.Methods Nineteen healthy volunteers randomly performed exercises of four-point hand-knee position (4 motions) and hand-foot kneeling position (3 motions), while surface electromyography (sEMG) signals were collected from bilateral rectus abdominis, external oblique, erector spine, and multifidus muscles. The average sEMG and muscle co-contraction index (CCI) based on the sEMG signals were analyzed and compared.Results Significant differences were found in the sEMG and CCI within and between the two positions. Under four-point hand-knee position with the right hand and left leg lifting, the activation of all muscles was higher than that in the starting position. In four-point hand-knee position with the left leg lifting, the activation of ipsilateral multifidus muscle was significantly higher than that in hand-foot kneeling position. The activation degree of external oblique muscle and rectus abdominis was higher in hand-foot kneeling position with right hand lifting. A total of 28 muscle matching methods were obtained by pair-to-pair matching of 8 muscles. The starting posture in four-point hand-knee position fluctuated the least, indicating that the spine was the most stable, while the index of other exercises fluctuated in a larger range.Conclusions The possibility of hand-foot kneeling position as core stabilization exercises was proved from two aspects, namely, muscle activation and CCI. The hand-foot kneeling position and four-point hand-knee position can be used for strengthening abdominal muscles and back muscles, respectively. The four-point hand-knee position with contralateral upper and lower limbs lift is a more advanced exercise for trunk muscles, but sports injuries should be avoided.

Comparison of the Lower Limb Kinematics and Muscle Activation Between Asian Squat and Western Squat / 医用生物力学

Objective To compare the differences in lower limb joint kinematics and muscle activation between Asian squat (AS) and Western squat (WS). Methods Eleven healthy adults were recruited to complete the biomechanical test of AS and WS. The 3D motion analysis system, force plates and surface electromyography (EMG) were used to collect kinematics, kinetics and muscle activation data of the subjects during two squats, and muscle force of the lower limb was also calculated by OpenSim. Results AS showed pelvis forward flexion, while WS showed pelvis backward extension at the time of peak knee flexion angle. Compared with the AS, a significant smaller hip flexion, larger knee flexion, larger hip abduction and hip rotation angles were found in WS at the time of peak knee flexion angle. Compared with AS, a significant greater peak force of soleus was found in WS during descent and ascent phases of squat. Additionally, a smaller peak force of anterior tibia was found in WS than that in AS during descent and ascent phases of the squat. No significant differences were found in other muscle peak force and the time of peak force between AS and WS. Conclusions The combined tibialis anterior activation and proximal joint flexion might be beneficial to stabilization during AS. The soleus muscle activation was significant in WS with heel lifting. The muscle activation pattern of proximal joint was similar between AS and WS. This study provides theoretical guidance for the design of clinical squat rehabilitation programs or the selection of squat training.

Biomechanics in Active Health / 医用生物力学

In active health, biomechanics plays an irreplaceable role. Exercise creates mechanical stimulation to human tissues and organs. It promotes health, or causes injury and disease. In addition, biomechanics is involved in the design and evaluation of assistive devices, as well as in rehabilitation clinical diagnosis and treatment. The development of active health biomechanics requires the integration of sports and medicine. It includes more dynamics, fatigue and mechanical coupling issues. In the future research, on the one hand, the experience of other directions in biomechanics should be learnt from. On the other hand, it is necessary to combine the frontiers of scientific and technological development to develop new directions in biomechanics.

Biomechanical Comparison of Two-Point and Three-Point Fixation for Treating SandersⅢ Calcaneal Fracture / 医用生物力学

Objective To analyze the biomechanical feasibility of two-point fixation by distal radius plate for the treatment of SandersⅢ calcaneal fractures. Methods The three-dimensional (3D) finite element musculoskeletal foot model was established based on CT and MRI images, which comprised bones, muscles, plantar fascia, ligaments and soft tissues. After validation, the SandersⅢ calcaneal fracture models fixed by distal radial plate (two-point fixation) and calcaneal plate (three-point fixation) were established, so as to compare the biomechanical characteristics of two calcaneal models. Results The maximum stress of the two-point fixation and three-point fixation model was 324.70 and 407.90 MPa, respectively. The maximum displacements of the two models were 2.498 and 2.541 mm, respectively. There was no significant difference in the posterior articular surface displacement between the two models. In both models, the Bohler’s angle and Gissane’s angle were within the normal range. Conclusions The two-point fixation by distal radial plate can satisfy the biomechanical stability of calcaneal fracture treatment. Compared with traditional steel plate, the two-point fixation shows the advantage of smaller surgical trauma, more uniform overall stress distribution, early weight-bearing rehabilitation after surgery, which is a novel treatment recommended for treating calcaneal fractures.

Biomechanical analysis of ankle-foot complex during a typical Tai Chi movement-Brush Knee and Twist Step / 生物医学工程学杂志

The purpose of this study is to analyze the biomechanics of ankle cartilage and ligaments during a typical Tai Chi movement-Brush Knee and Twist Step (BKTS). The kinematic and kinetic data were acquired in one experienced male Tai Chi practitioner while performing BKTS and in normal walking. The measured parameters were used as loading and boundary conditions for further finite element analysis. This study showed that the contact stress of the ankle joint during BKTS was generally less than that during walking. However, the maximum tensile force of the anterior talofibular ligament, the calcaneofibular ligament and the posterior talofibular ligament during BKTS was 130 N, 169 N and 89 N, respectively, while it was only 57 N, 119 N and 48 N during walking. Therefore, patients with arthritis of the ankle can properly practice Tai Chi. Practitioners with sprained lateral ligaments of the ankle joint were suggested to properly reduce the ankle movement range during BKTS.

Effects of Gravity Loading Countermeasure Garment on Degeneration of Lumbar Intervertebral Disc in Microgravity Environment / 医用生物力学

Objective To analyze the biomechanical effects of gravity loading countermeasure garment on human lumbar intervertebral disc in microgravity environment. Methods Based on CT images of a healthy adult volunteer, the finite element model of L4-5 vertebrae was established. Through the empty load and 400 N axial loading for 4 hours on lumbar finite element model, the biomechanical effect of the non-intervention and gravity loading countermeasure garment were simulated respectively in microgravity environment. Results The central pore pressure, radial displacement and water content of the human lumbar intervertebral disc increased with time in microgravity environment. In the case of wearing gravity loading countermeasure garment, the central pore pressure, axial stress, radial displacement and water content of the lumbar intervertebral disc were reduced after 72 hours of cyclic loading compared with the non-intervention group. Conclusions Wearing gravity loading countermeasure garment can help astronauts to prevent the adverse effects of microgravity on the spine to some extent in microgravity environment.

Research Progress on Balance Control and Biomechanics of Tai Chi / 医用生物力学

Tai Chi, developed from a kind of martial arts into a new form of exercise therapy, has received wide attention. Studies on the rehabilitation effects of Tai Chi and its mechanism have been conducted by researches in both China and other countries, and most of these studies are concerned with Tai Chi’s role in balance improvement. According to the purpose of the study and the evaluation index, the rehabilitation function and biomechanical characteristics of Tai Chi exercising were reviewed. The biomechanical mechanism of rehabilitation function was discussed by comparing the differences between the research method and the conclusion. Due to the lack of a unified specification for the standard and duration of Tai Chi exercising, some study result are inconsistent. Enhancing biomechanical researches on Tai Chi and setting different practicing standards for people with various health conditions will be a main direction for Tai Chi study in the future.

Effects of ankle stabilizers on electromyographic activities of lower extremity muscles during simulated half-squat parachute landing / 医用生物力学

Objective To study effects of ankle stabilizer on electromyographic activities of lower extremity muscles during the simulated half squat parachute landing and its gender differences. Method Eight male and eight female healthy adults were required to jump from a platform of 0.72 m high to simulate half squat parachute landing. The experiment was divided into 3 groups: the barefoot one as control group, the group wearing tapes and braces respectively. The electromyogram (EMG) of each subject’s tibial anterior, lateral gastrocnemius, biceps femoralis and rectus femoralis was measured. Two way ANOVA was used to analyze and evaluate the effect of the stabilizers and genders on EMG variables. Results The use of brace significantly increased the pre landing EMG amplitude of the tibialis anterior for male (Control: 266 μV; Tape: 368 μV; Brace: 552 μV). The stabilizers had no significant effects on the other EMG parameters. Conclusions Semi rigid ankle braces are capable of arousing more active EMG of male’s ankle flexor during half squat parachute landing, but female does not share this predominance. Ankle stabilizers have no significant effects on EMG activities for knee joints.

Valid constructing method of three-dimensional finite element human foot model and experimental analysis on its rationality / 生物医学工程学杂志

To provide a digital simulation platform for foot-ankle biomechanics research, a 3-D finite element model was established through helical CT images under the principle of RE (reverse engineering) and meshed in FEM software. In the process of modeling cartilage, ligaments, tendons and plantar soft tissue, many anatomic data and results of cadaver specimen experiment were referenced; LINE elements and SHELL elements were used skillfully to simplify the model and resemble the physiological state. The model was then validated by specimen experimentation, which was done on seven fresh cadaver foot specimens, and digital speckle correlation method (DSCM) was used to measure their displacements. Upon the comparison with experimentation and others models, this study also testified that the model, of which the plantar fascia is linked to the heads of metatarsus, is more reasonable to clinical application.

Longitudinal arch stress distribution of the foot following plantar ligament injury / 中华创伤杂志

Objective To measure stress distribution of the main bone architecture of the normal adult cadaveric foot and discuss the effect of plantar ligament injury on stress distribution. Methods Seven fresh adult cadaveric feet were used and 10 strain gauges attached to the bones of the longitudinal foot arch,including the calcaneus,navicular,medial cuneiform,1-5 metatarsal trunk,the distal part of the tibia and fibular,respectively.After the loading Was added to 700 N by almighty test machine,resistance strainmeter was used to measure surface strain of these bones.The results were processed statistically. Results The strain was varied based on different bone segments attached and increased with loading.Tensile force was always found at the medial part of the navicular,the distal part of the tibia and fibular,while the others showed compression all the time.Peak strain was found at calcaneus.followed by the second and third metatarsal.Strain on the surface of the bone segments changed greatly with different ligament injury(P＜0.05).Conclusion The bone surface stress of the longitudinal foot arch changes significantly when the plantar ligament is injured.