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Abstract:Generally, extracellular matrix (ECM) has the characteristics of viscoelasticity. In osteoarthritis (OA), catabolic processes alter the viscoelastic properties of functional pericellular matrix (PCM) of chondrocytes. Chondrocytes sense and respond to their mechanical microenvironment via an array of mechanosensitive receptors and channels that activate a complex network of downstream signaling pathways to regulate several cell processes central to OA pathology. Advances in understanding the specific mechanosignalling mechanisms in articular cartilage will promote the development of cell microenvironment construction in cartilage tissue engineering and the targeted precision therapeutics for OA. In this review, the work on the mechanism of matrix viscoelasticity regulating chondrocytes mechanotransduction by Agarwal et al. was briefly commented, and the recent advances related with their work was also discussed.

Abstract:Lumbar surgical operation is the crucial treatment against lumbar degenerative diseases (LDDs), whose development depends on persistent comprehension and innovation of vertebral biomechanics. The thorough understanding of biomechanical changes during lumbar senescence and degeneration is the important bedrock to grasp LDDs pathogenesis, renovate LDDs surgical strategy, and embrace more precise and minimally invasive treatment against LDDs. Herein, in this review, the intimate crosstalk between LDDs with degenerative biomechanics of vertebrae, intervertebral disc and paravertebral muscles was elucidated, followed by the classification of lumbar surgery history into non-vertebral implant era (before the year 1980), vertebral implant era (during the year 1980-1990), vertebral fusion era (during the year 1990-2010), precise and minimally invasive decompression era (after the year 2010) based on lumbar surgical characteristics in each era. The significance of representative biomechanical studies in each era for lumbar surgery was also concluded. From biomechanical perspectives, the history of spinal surgery is the development history of surgical strategies that has progressed as the continuously in-depth understanding of spinal biomechanics. With the deepening of spinal biomechanical researches, spinal surgeons are expected to develop treatment strategies that are more adapted to physiological and biomechanical characteristics of the spine, thereby guiding the future direction of spinal surgery advancement.

Abstract:Biomechanical model of musculoskeletal system has accurate human anatomy and good biological fidelity. It can accurately and effectively reveal the biomechanical state and predict the internal mechanical response of musculoskeletal system. Therefore, it has been widely used in biomechanical study of musculoskeletal system, diagnosis and treatment of bone diseases, implant optimization design and preoperative planning. In 2021, the latest advances in biomechanical modeling method of musculoskeletal system mainly included three aspects, i.e., individualized finite element modeling, statistical model modeling and musculoskeletal system modeling. On this basis, the latest relevant literatures were summarized in this review to illustrate the progress and main applications of the above modeling method, and the future development direction of musculoskeletal modeling was discussed.

Abstract:Objective To explore the spatial distribution of microstructural parameters and mechanical properties for trabecular bone in the femoral head with osteonecrosis. Methods Microstructural parameters and mechanical properties of trabecular bone in different regions were analyzed by combined use of imaging measurements and numerical simulation method, and the spatial distribution of biomechanical properties for trabecular bone along coronal, sagittal and vertical directions was investigated. Results Microstructural characteristics and mechanical properties of trabecular bone were Y-shaped distributed along coronal and sagittal directions, and mechanical properties of trabecular bone in Y-shaped region were higher than those in the other regions. Such distribution characteristics was consistent with the location of principle compressive group in the femoral head. Conclusions Necrotic lesions in Y-shaped region had a greater influence on stress distribution of the femoral head and might cause the deterioration of osteonecrosis. The spacial correlation between necrotic lesions and Y-shaped region should be fully considered during clinical diagnosis.

Abstract:Objective To analyze the influence of total hip arthroplasty (THA) on the process of proximal femoral bone remodeling by using the Wolff bone remodeling theory. Methods According to control equation of bone remodeling, the program of bone remodeling was written in Python language. Preoperative femur model and postoperative femur and prosthesis finite element models were established respectively in ABAQUS software. The process of bone reconstruction before and after THA operation was compared to analyze the effect of prosthesis implantation on mechanical properties of the femur in the middle and long term after THA operation. Results The stress in proximal femur continued to decrease after prosthesis implantation, and the stress site was transferred from the femoral head to the prosthesis, resulting in an obvious stress shielding phenomenon. Bone loss in the stress shielding area was serious. The femoral shaft cortical bone became thinner and the stress shielding was relieved. The medial side at the bottom of the prosthesis was compressed, and the stress was significantly higher than that of the lateral side, where the bone was unevenly distributed. Conclusions After THA operation, obvious stress shielding occured at proximal medial side of the femur, leading to bone loss and prosthesis loosening. The difference in stress levels on both sides at the bottom of the prosthesis resulted in an uneven bone distribution, causing the discordance between the prosthesis and the femur, as well as postoperative pain in the middle part of the thigh.

Abstract:Objective To study topological structure of a new type of three-dimensional (3D) printed height increasing insoles for leg length discrepancy (LLD) and its effect on biomechanics of lower limbs. Methods Topological structure for middle and rear part of the insole was optimized by solid isotropic microstructures with penalization (SIMP), the force was loaded and the boundary conditions were set according to force area of the insole, and the height increasing insole with thermoplastic polyurethanes (TPU) materials was printed by selected laser sintering (SLS). The insoles were used in 9 patients with LLD, visual analogue scale (VAS) and Maryland foot function scores were used to compare pain and foot function changes of patients before and after using the insole, and the 3D gait analysis system was used to compare spatiotemporal parameters and vertical ground reaction force (vGRF) of both lower limbs. Result sAfter the patient wore 3D printed insole, VAS scores decreased, Maryland foot function scores increased, vGRF of both lower limbs decreased, and the difference of cadence, stance phase and swing phase in both lower limbs decreased. Conclusions The 3D printed height increasing insole after topology optimization can improve coordination of lower limb movement, reduce ground impact, relieve pain and improve foot function, thus providing an effective personalized orthopedic plan for LLD treatment in clinic.

Abstract:Objective To investigate changes in gait level of patients after hip replacement, the variation trend of bone mineral density (BMD) around the prothesis was studied, so as to reveal the influence pattern of gait level at postoperative initial and long-term stages on bone reomodeling. Methods Based on adaptive bone remodeling theory, the finite element model of femer-prosthesis was developed. The BMD distribution was calculated using the initial and long-term gait level after hip replacement as the remodeling parameters. Gruen method was applied to quantify the BMD changes. Results At the postoperative initial stage, obvious variations existed in constant gait group and changing gait group. The maximum difference occurred in low gait group, resulting in the decrease of BMD by 41% in greater trochanter region. The improvement of gait level would promote the enhancement of BMD in proximal and middle region of the prosthesis, resulting in the increase of BMD by 47%. Long-term gait recovery would promote BMD recovery in middle and end region of prosthesis, with BMD increase by 2%-9%. Conclusions The research findings provide guidance for rehabilitation process of patients after hip replacement.

Abstract: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.

Abstract:Objective For patients with foot drop gait, to design a kind of anterior ankle foot orthosis (AFO) with adjustable stiffness, so as to restore natural gait of the ankle by limiting the patients’ unusual plantar flexion to the optimum extent. Methods The minimum orthodontic moment of 10 foot drop male patients was measured by self-made experimental equipment, which could be used to select optimum material modulus of the AFO. The relationship between elastic modulus and different filling structures and filling ratio parameters was studied by tensile test. A typical patient with foot drop was selected, and the anterior AFO fitting the shape of patient’s foot was quickly made by three-dimensional (3D) printing with foot geometric data and specific filling material, filling structure and filling rate. The kinematics and surface electromyography (sEMG) of plantar flexors were tested under barefoot and wearing two kinds of AFOs, so as to verify the effect of the AFO on plantar flexion. The effectiveness of the limitation and the degree of preservation of ankle valgus and plantar flexion were discussed. Results The minimum corrective torque required for 10 male patients with foot drop was 2.16 N·m. Compared with the rigid AFO, the range of motion (ROM) of plantar flexion and valgus increased by 67.8% and 88.6% respectively with the flexible AFO. The activation of the muscles responsible for plantar flexion (soleus, medial head of gastrocnemius and lateral head of gastrocnemius) also decreased by 38.3%, 46.6% and 55.8%. Conclusions This AFO with adjustable stiffness can be used for orthosis customization of patients with foot drop, providing more effective and long-term orthosis function and potential.

Abstract:Objective To estimate knee adduction moment (KAM) and knee flexion moment (KFM) under different gait test conditions via an inertial sensor network (ISN). Methods Twelve healthy young male subjects wore eight inertial sensors (located in the trunk, pelvis, both thighs, both shanks, both feet) and walked under different test conditions (changing foot progression angle, trunk sway angle, step width and walking speed). An ISN was used to extract biomechanical features as the input of recurrent neural network (RNN), so as to estimate the KAM and KFM. Results The overall KAM estimation accuracy: relative root mean square error (rRMSE) was 8.54% and r=0.84. The overall KFM estimation accuracy was rRMSE=6.40% and r=0.94. Conclusions The model can be used as the basis for load estimation of knee joints out of the lab and its potential application includes gait training and rehabilitation assessment after knee surgery.

Abstract:Objective To analyze the gait characteristics of hip disarticulation amputees, and analyze the reasons for their differences from normal gait, so as to assist clinical diagnosis and evaluation. Methods Through the portable human motion capture device and plantar pressure analysis system, the kinematics and plantar pressure information of 5 hip amputees were collected and compared with 15 healthy volunteers in control group. Gait differences between the amputees and normal subjects and between the affected leg side and the healthy leg side of the amputees were compared. Results The proportion of double-support period for hip amuptees was higher than that of normal gait. Step length, step time, loading response period, mid support period, pre-swing period, proportion of the swing period for the affected leg side and healthy leg side of hip amputees showed significant differences with those of control group. The relative symmetry index of the gait for hip amputees was 0.60±0.05. Compared with the affected leg side, the support period of the healthy leg side was extended, the step length was shortened, the ground reaction force was greater than that of the affected leg side, and the center of pressure trajectory shifted to the affected leg side. Conclusions The gait of hip amputees is significantly different from that of normal people. Hip amputees have weak walking ability, poor gait symmetry, and they lack of continuity in the body’s center of gravity. The results provide experimental basis and theoretical analysis for the design of mechanical structure and control system of novel hip prosthesis.

Abstract:Objective To establish the instability model of goat cervical vertebrae, and test biomechanical stability of the novel arc cervical titanium mesh with endplate ring. Methods The anatomical data from cervical vertebrae of adult goats were measured, so as to select a new type of arch cervical titanium mesh with endplate ring which was suitable for goat cervical vertebrae. A total of 24 goats with preserved articular capsule, ligaments and intervertebral disc were randomly divided into 4 groups. Group A (n=6, normal group) didn’t receive any special treatment, while Group B (n=6, model group) received partial resection of C4 vertebrae as well as upper and lower intervertebral disc. On the basis of models in Group B, Group C (n=6, experimental group) was installed with the novel arch cervical titanium mesh and fixed by plate and screw, and Group D (n=6,control group) was installed with traditional straight titanium mesh and fixed by plate and screw. The ranges of motion (ROMs) for 4 groups of specimens during flexion, extension, left/right lateral bending, left/right rotation under 2.0 N·m load were measured, and their three-dimensional (3D) motion stability was tested. The displacement of Group C and Group D under 200 N compression force was measured, the stiffness was calculated, and the anti settlement ability of the whole specimen was tested. Results The ROMs of Group A in all directions were smaller than those of Group B,the ROMs of Group A were larger than those of Group C, and the ROMs of Group C during flexion were smaller than those of Group D (P<0.05). The stiffness of Group C was higher than that of Group D (P<0.05).The compression displacement of Group C was smaller than that of Group D(P<0.05). Conclusions Compared with the straight titanium mesh, the novel arc titanium mesh is more consistent with the physiological curvature of cervical verebrae, and has better stability than the traditional titanium mesh during the most frequent flexion activities of cervical verebrae. Moreover, compression displacement of the novel arc titanium mesh under short-term stress is smaller than that of the straight titanium mesh, and its postoperative anti-settlement is better than that of the straight titanium mesh, which is worthy of further experiment and clinical promotion.

Abstract:Objective To predict and assess biomechanical responses and injury mechanisms of the thorax and abdomen for small-sized females in vehicle collisions. Methods The accurate geometric model of the thorax and abdomen was constructed based on CT images of Chinese 5th percentile female volunteers. A thoracic-abdominal finite element model of Chinese 5th percentile female with detailed anatomical structure was developed by using the corresponding software. The model was validated by reconstructing three groups of cadaver experiments (namely, test of blunt anteroposterior impact on the thorax, test of bar anteroposterior impact on the abdomen, test of blunt lateral impact on the chest and abdomen). Results The force-deformation curves and injury biomechanical responses of the organs from the simulations were consistent with the cadaver experiment results, which validated effectiveness of the model. Conclusions The model can be used for studying injury mechanisms of the thorax and abdomen for small-sized female, as well as developing small-sized occupant restraint systems and analyzing the forensic cases, which lays foundation for developing the whole body finite element model of Chinese 5th percentile female.

Abstract:ObjectiveT o explore the influence of patch shape for intraventricular tunnel (IVT) construction on biomechanical performance of the double outlet right ventricle after correction. Methods Based on the idealized IVT model, a two-dimensional IVT patch was designed. Six groups of patch models with the rhombic long-to-short axis ratio of 1∶0.625, 1∶0.3, 1∶0.2, 1∶0.15, 1∶0.125, 1∶0.1 were established according to the difference between the long and short axis of the rhombus patch in the turning part, and finite element analysis method was used to numerically simulate the process of stitching, holding and propping up the patch into a three-dimensional (3D) IVT model. Results The maximum stresses on suture line of 6 patch models were mainly concentrated at acute-angle corners of the rhombus. As rhombic long-to-short axis ratio of the patch increased, the maximum stress of the IVT suture line first decreased and then increased, and the volume showed an increasing trend. The pressure difference between two ends of the tunnel first decreased and then increased. The patch with the long-to-short axis ratio of 1∶0.15 had a uniform surface stress distribution, and the maximum stress on the suture line was the smallest. Meanwhile the right ventricular volume was less encroached on, and the pressure difference at both ends of the tunnel was small. Conclusions The IVT shape can influence stresses of suture line, the right ventricle volume and the pressure difference of IVT with non-monotonic variations. The suture effect of the patch with the long-to-short axis ratio of 1∶0.15 is relatively better among the constructed models.

Abstract:Objective To explore the relationship between the establishment of collateral circulation caused by iliac vein compression syndrom(IVCS) and the deep venous thrombosis (DVT). Methods Different types of ideal collateral circulation models and IVCS patient-specific models were numerically simulated using computational fluid dynamics (CFD) in combination with the blood stasis model. The relationship between blood retention and collateral types and cross-sectional area was studied, and the relationship with thrombosis was explored. Results Wall shear stress (WSS) at the distal end part of each ideal model was 0.3 Pa. After four cardiac cycles, the residual blood stayed at the stenosis and the distal end part for the lumbar ascending and pelvic type models, the old blood volume fraction (OBVF) varied with collateral cross-sectional areas, ranging from 5%-90% and 70%-80%, respectively. The OBVF of the coexistence model was above 80%. The WSS at the distal end part of the patient-specific model was 0.9 Pa, and the OBVF at the distal end part was 51.5%. Conclusions The stenosis and the distal end part are most prone to blood stasis, and closely related with DVT. The larger the collateral cross-sectional area, the more serious the blood stagnation. Blood stagnation of the coexistence model is higher compared with the model with lumbar ascending type and pelvic type.

Abstract:Objective To study CH-VAD blood pump developed by CH Biomedical Inc., a method for estimating the real-time flow of blood pump was established by using the voltage, current, speed, duty cycle, and fluid viscosity as the input data. Methods The blood pump system was disassembled into two modules, the motor and the centrifugal pump. Firstly, the output torque of the motor was calculated according to the voltage, current, speed and duty cycle of the motor, then the relationship between flow and torque at different speeds and viscosities was tested through experiments, and a fitting model was established based on the experimental data. Results The fit goodness of Pump 1 and Pump 2 reached 0.982 6 and 0.982 9,respectively. The fitting parameters were used for verification. When the viscosity changed, the root mean square error for the estimated flow of Pump 1 and Pump 2 was 0.260 and 0.274 L/min, respectively. The fitting parameters and estimated results of the two blood pumps were in good agreement. The flow estimation method could follow the actual flow waveform in real time, and the accuracy of the estimated average flow was not affected by the pulsation. Conclusions The flow estimation method proposed in this paper is suitable for CH-VAD blood pumps. It can accurately estimate the flow of blood pumps in the range of speed 1 600-3 600 r/min, flow 0.4-8 L/min, viscosity 1.2-5 mPa·s, and can follow the flow waveform well under pulsating conditions.

Abstract:Objective To explore the hemodynamic characteristics in functional side-to-end (STE) anastomosis arteriovenous fistula (AVF) by computational fluid dynamics (CFD), so as to provide theoretical basis for clinical application of the AVF. Methods AVF models of functional STE anastomosis (STE group) and conventional STE anastomosis (cSTE group) were established. The hemodynamic parameters of models in two groups under retrograde and antegrade flow states were analyzed, including blood flow velocity, pressure drop, low wall shear stress area (LWSSA). Results Under retrograde flow, the total LWSSA in STE group was 5.70% lower than that in cSTE group, and the LWSSA on venous wall in STE group was 49.71% lower than that in cSTE group. Under antegrade flow, the total LWSSA in STE group was 6.97% greater than that in cSTE group, and the LWSSA on venous wall in STE group was 10.62% lower than that in cSTE group. Conclusions Under retrograde flow state, functional STE anastomosis can significantly decrease the LWSSA of AVF, while under antegrade flwo state, functional STE anastomosis has no significant impact on improving the LWSSA of AVF.

Abstract:Objective To study the effect of morphological characteristics of modular inner branched stent graft (MIBSG) on hemodynamic performance of postoperative aortic arch based on parameterized MIBSG model. Methods The fluid-structure interaction model of blood-MIBSG coupling performance was solved, and the effects of stent branch angles, stent diameters on hemodynamic characteristics were analyzed. Results With the increase of angles between branch stent and aortic arch stent, blood flow within the branch decreased, but the stress and displacement increased. With the decrease of stent diameters, blood flow perfusion decreased significantly, but the stress and displacement increased first, and then decreased. Conclusions The morphological changes of MIBSG not only have an impact on blood perfusion rate of branch stent, but also affect the stress exerted on stent and the corresponding displacement. Before application in clinic treatment of aortic arch diseases, the movement and torsion of MIBSG should been taken into full account in operation plan according to the actual situation.

Abstract:Objective To investigate the influence of internal and external sphincter loss synergy on stress distributions and urine flow rates of lower urinary tract organs and tissues. Methods Based on collodion slice, the geometric model of the lower urinary tract was reconstructed, and finite element model of the lower urinary tract with muscle active force was established. Through fluid structure coupling simulation, the changes of tissue stress and urine flow rate were simulated under four conditions: normal contraction of internal and external sphincter, total loss of muscle active force and single loss of muscle active force for internal and external sphincters at the end of urination. Results The urethral stress changes in normal contraction of internal and external sphincter muscles were the same as the clinically measured urethral pressure changes. Compared with normal contraction, when the internal sphincter lost its muscle active force alone, stress of the internal sphincter and the urethra of the prostate was reduced by 33.6% and 13.8%, and flow rate of urine in this position was also reduced. When the external sphincter lost its muscle active force alone, the urethral stress of the external sphincter and external urethra was reduced by 59.5% and 24.03%, respectively. When the internal and external sphincter lost muscle active force, stress of the internal sphincter, the prostate, the external sphincter and the external urethra were reduced by 38.77%, 18.6%, 63.58%, 29.74%, respectively, and flow velocity in the corresponding position was also reduced. Conclusions Internal and external sphincter loss synergy resulted in the difference of tissue stress and urine flow rate. The results can provide the theoretical basis for surgical treatment of urinary incontinence caused by sphincter.

Abstract:Objective To obtain a more suitable puncture method for venipuncture robot through experiments.Methods By using different puncture speeds and angles for biomimetic materials, the force-time curves by various puncture methods were obtained. Results During puncture process, with the increase of the puncture angle, a smaller puncture force was required. The faster puncture speed would lead to a larger puncture force. Conclusions The 40°-45° puncture angleand the 120-300 mm/min puncture speed should be used for designing the puncture method of venipuncture robot. The results provide references for selecting the puncture angle and speed of the venipuncture robot.

Abstract:Objective To quantify operation characteristics of the ankle rotating-traction-poking manipulation (RTPM) for treating acute lateral ankle sprain by using motion capture technology, so as to provide objective references for standardized operation of RTPM and its education inheritance. Methods A professional physiotherapist performed the RTPM on 60 volunteers with acute lateral ankle sprain. Motion capture system was used to acquire effective kinematic data during the RTPM, so as to make analysis and summarize rules. Results The average time of ankle rotating for six circles was 11.36 s and the average time of ankle traction and poking was 3.42 s. The average displacement of ankle traction was 36.94 mm and the average displacement of ankle poking was 22.44 mm. The average angle of ankle traction was 23.27°, and the average angle of ankle poking was 22.76°. During the RTPM for treating acute lateral ankle sprain, the average linear velocity of ankle rotating was 58.28 mm/s, and the average linear velocity of ankle traction and poking was 23.81 mm/s. The linear acceleration of ankle rotating was 0.43 mm/s2, and the linear acceleration of ankle traction and poking was 0.54 mm/s2. Conclusions The RTPM can be applied in clinical practice. During the RTMP, the principle of gentleness, rhythmicity and continuity should be followed. Under the premise of following physiological characteristics of ankle joint, treatment of the sprained ankle should be carried out with slow and uniform speed continuously.

Abstract:Objective To evaluate the influence of stress distributions on bone-anchored maxillary protraction at different protraction sites, so as to guide patients to choose an optimal protraction site in clinic. Methods A three-dimensional (3D) finite element model of child head with implant anchorages was establised. Four protraction sites were set according to the position of implant installation. Working condition 1: the alveolar bone at the intersection of distal 2 mm of primary lateral incisor crown distal surface and gingival cervical margin to 5 mm. Working condition 2: the alveolar bone at the intersection of mesial 2 mm of maxillary first primary molar crown mesial surface and gingival cervical margin to 5 mm. Working condition 3: the alveolar bone at the intersection of mesial 2 mm of maxillary first molar crown mesial surface and gingival cervical margin to 5 mm. Working condition 4: the alveolar bone at the intersection of distal 2 mm of maxillary first molar crown distal surface and gingival cervical margin to 5 mm. The finite element models were loaded with 500 g protraction force at each side with 30° forward direction to the occlusal plane. Stress distributions on each suture were analysed. Results The maximum stress of frontomaxillary suture was in working condition 2 (1 477-28 190 Pa). The maximum stress of nasomaxillary suture was in working condition 1 (5.296-924 Pa). The maximum stress of zygomaticomaxillary suture was in working condition 4(394.7-13 130 Pa). The maximum stress of zygomaticofrontalis suture was in working condition 4 (495.2-31 690 Pa). The maximum stress of zygomaticotemporal suture was in working condition 3 (1 148-15 870 Pa). The maximum stress of medianpalatine suture was in working condition I (6.479-730 Pa). Conclusions When the protraction sites are set in distal maxillary primary lateral incisor and mesial maxillary first primary molar, it is of positive significance to improve the concave profile, especially in nose root. When the protraction sites are set in mesial or distal maxillary first molar, it is of positive significance to improve the concave profile, especially in maxillary basal bone of the midface.

Abstract:Objective To establish the theoretical model for morphology of lipid droplets adhering to inner vascular wall, so as to provide the theoretical model for the study and analysis of the overall morphology of lipid droplets on inner vascular wall of patients with fat embolism. MethodsThe model of the droplet with variable radius on inner wall of the cylindrical tube was established to describe morphology of lipid droplets on inner vascular wall, and accuracy of the theoretical model was verified by Surface Evolver (SE) software simulation results. According to the theoretical model, the influencing patterns of lipid droplet volume and contact angle on dimensionless adhesion area Sb0 and blockage ratio κ of lipid droplets in blood vessels were analyzed. Results The theoretical model could predict contour parameters of adhesion morphology for lipid droplets on inner vascular wall, including the height and arc radius of lipid droplet at azimuth angle of 0 and π/2. The relative errors between contour parameters obtained from the theoretical model and corresponding parameters obtained from the SE simulation were smaller than 10%. For lipid droplets with the same dimensionless volume V0, Sb0 of inner vascular wall decreased with contact angle increasing, and blockage ratio κ increased with contact angle increasing. At the same contact angle, the smaller V0 , the smaller Sb0 and κ would be. Conclusions The established theoretical model with variable radius can well describe morphological characteristics of lipid droplets on inner vascular wall. The influening pattern of volume, contact angle and other parameters on height, adhesion area and cross-sectional area of lipid droplets can be accurately and quickly obtained through the theoretical model, indicating that the larger the contact angle of lipid droplets or the smaller the dimensionless volume, the lower the probability of embolism. The research findings provide theoretical support for the analysis on related diseases.

Abstract:Objective To investigate the effects of cyclic stretch on migration of MC3T3-E1 cells and its related mechanism. Methods The strain loading system was used to stretch MC3T3-E1 cells cultured in vitro with 15% amplitude, to simulate the mechanical condition in vivo. The wound healing assay was used to detect the migration of MC3T3-E1 cells. Western blotting was used to test Runx2 expression. RNA interfering was used to decrease Runx2 expression. Results Cyclic mechanical stretch with 15% amplitude, 1.25 Hz frequency and lasting for 24 hours could promote the migration of MC3T3-E1 cells and increase the expression level of Runx2. Runx2 interference inhibited the migration of MC3T3-E1 cells in static culture condition. Interference with Runx2 expression in MC3T3-E1 cells could partially reduce the positive effect of cyclic mechanical stretch on cell migration. Conclusions Cyclic stretch can promote the migration of MC3T3-E1 cells, and Runx2 may play an important role in this process. This study provides experimental basis for finding innovative clinical treatment method to promote fracture healing.

Abstract:bjective To observe the changes of upper extremity sensory function in patients with radicular cervical spondylosis and evaluate the treatment effect, by using the method of suspension exercise therapy (SET) and soft tissue manipulation. Methods A total of 72 patients with cervical spondylosis were divided into observation group (treated by SET combined with manipulation)and control group (treated by purely cervical traction) by simple random method. Both groups received 4-week continuous treatment for 6 times per week. The somatosensory evoked potential(SEP), current perception threshold (CPT) before and after the treatment in two groups were separatedly tested, and changes in visual analogue scale (VAS) pain scores of the affected limbs were examined, so as to determine the effective rate of treatment. Results After treatment, the latency of SEP was shortened mainly in brachial plexus potential N9 and cervical spinal potential N13 in two groups (P<0.05). The CPT levels and the VAS pain scores of the affected limbs were reduced in two groups (P<0.01), and the treatment effect in observation group was better that in control group (P<0.01)．Conclusion SET combined with soft tissue manipulation can effectively promote the repair of nerve sense function of cervical spondylotic radiculopathy.

Abstract:Objective To explore the effect of proprioceptive neuromuscular facilitation (PNF) rehabilitation training on functional recovery of athletic rotator cuff injury. Methods Twenty-two college students with athletic rotator cuff injuries were stratified according to their gender and randomly divided into resistance band + passive joint range of motion (ROM) training group (control group) and PNF training group (experimental group). The visual analog scale (VAS) was used to evaluate subjective pain intensity of the shoulder joint. Pain positive rate for each manipulation test of rotator cuff injury was observed, and active ROM and muscle strength of the shoulder joint were measured. Improved UCLA shoulder joint score was used to evaluate comprehensive function of the shoulder joint. Results After training, VAS scores and pain positive rate in two groups were lower than those before training, and VAS scores and pain positive rate in experimental group were lower than those in control group. Muscle strength, active ROM in all directions and improved UCLA score of the shoulder joint in two groups were also higher than those before training, and the internal rotation muscle strength, the internal rotation and external rotation active ROM, improved UCLA score of the shoulder joint in experimental group were higher than those in control group. Conclusions PNF rehabilitation training can reduce the pain of athletic rotator cuff injury, improve the active ROM, muscle strength and UCLA shoulder joint score. The function recovery effect of PNF training is better than that of resistance band + passive ROM training.

Abstract:Neovascularization plays an important role in many physiological and pathological processes, but its mechanism is still unclear. Since vascular cells are subjected to a variety of biochemical and biomechanical stimulations in vivo and live in a complex microenvironment, it is necessary to construct the vascular model in vitro and simulate the in vivo microenvironment to explore the mechanism of neovascularization. Recently, owing to the advance of micromachining and microfluidic technology, various in vitro microvascular models have emerged. Variables such as shear stress, interstitial flow and biochemical gradient of angiogenic factors have been controlled in these models, which greatly promotes the research of neovascularization. The construction, development and biomechanical design of various microvascular models are reviewed in this paper.

Abstract:In recent years, with the increase of traffic accidents and the further development of aging, the incidence of pelvic fracture is gradually increasing. Based on the in-depth study about biomechanics of pelvic fracture fixation, the surgical treatment has been widely carried out. The purpose of surgical treatment is to effectively reduce and fix the fracture, correct deformity, restore integrity and stability of the pelvis, and minimize the complications caused by internal and external fixation. How to improve stability of the pelvis while ensuring therapeutic effect is a problem that every doctor will face in clinic. This paper summarizes the biomechanical research progress of pelvic fracture in recent years from the aspects of anatomy, normal biomechanics, classification and biomechanics of pelvic fracture fixation, so as to provide some references for reasonable treatment of pelvic fracture.

Abstract:Thrombosis is the process of platelet adhesion and aggregation or blood coagulation after the body is subjected to certain physical and chemical stimuli. At present, the use of basic experimental research and computational simulation to understand thrombosis has become a research hotspot. The complex process of thrombosis makes computational modeling very difficult, but the development of calculation models has still made great progress. At present, a variety of calculation models for thrombosis have been developed, including coagulation models based on ordinary differential equations, mathematical models based on finite element analysis, Lattice-Boltzmann method models, smooth particle dynamics method models, etc. Each model has its advantages and disadvantages.In this review, the physiological mechanism of thrombosis was explained, the models for simulating thrombosis were also systematically sorted out and evaluated, and the limitations of computational simulation and future application prospects were summarized as well.