Abstract:As the outermost layer of the eyeball, corneal and scleral tissues play an important role in the maintenance of ocular morphology and refraction function. The cornea and sclera are both typical viscoelastic tissues, and changes in their biomechanical properties can lead to corresponding ocular diseases such as myopia and keratoconous. In clinic, biomechanical behavior can be changed by altering the tissue and morphological structures of cornea and sclera ( such as refractive surgery, orthokeratology wear, corneal collagen crosslinking), so as to treat some ocular diseases related to refraction. In this review, the progress of biomechanical researches in corneal and scleral diseases as well as its clinical translation was summarized, and problems in clinic treatments were clarified and discussed, so as to provide references for improving diagnostic and therapeutic strategies, and developing new potential approaches in clinic treatments.
Abstract:Objective The tendency of elastic modulus on trabecular meshwork (TM) surface was measured and numerical simulation was derived using an anisotropic model, so as to verify rationality of the anisotropic model. Methods Atomic force microscope (AFM) indentation tests were conducted on four TM samples from two rats at different locations, and simulation experiment was conducted to measure elastic modulus at different locations of TM surface based on the proposed anisotropic TM model. Results The tested TM elastic modulus varied at different test locations on TM surface and reached the minimum value in the middle of TM. The anisotropic TM model could reliably simulate this phenomenon. Conclusions The anisotropic TM mechanical model has strong theoretical significance and practical values in describing mechanical characteristics of TM. Meanwhile, the model can explain the huge differences in elastic modulus obtained by uniaxial stretch of TM tissues and by AFM indentation test. Therefore, the anisotropic TM model is a better description for TM mechanical properties
Abstract:Objective To investigate the effect of adhesion behavior of the extraocular muscle ( EOM) on eye motion. Methods The pull-off test was carried out on EOM in vitro exposed to the air in different time periods using steel spherical indenters with three different sizes, and adhesion behavior of the EOM was studied. Then contribution of the adhesion between EOM and sclera to maintain eye balance during eye motion was analyzed by combination with the JKR theory. Results The adhesion force of the epimysium of EOM in vitro decreased with the increase of exposure time. Except for the case of 1-hour exposure time, the adhesion force was not affected by the indenter size at other exposure time. The experimental adhesion force was in good agreement with the theoretical adhesion force calculated by the JKR theory. The adhesion force between EOM and sclera, as well as the active force of lateral rectus muscle increased with the abduction angle increasing. The adhesion moment increased exponentially with the abduction angle, and accounted for an increasing proportion of the sum of resistance moment, passive moment and adhesion moment. Conclusions The duration of exposure to the air had a significant effect on adhesion properties of the epimysium of EOM in vitro. The adhesion interaction between sclera and EOM could be preferably described by the JKR theory. The adhesion interaction between EOM and sclera participated in maintaining balance of the eyeball and made certain contributions in regulating eye motion. The results in this study can provide theoretical foundation for researches of disorders related to eye motion such as strabismus.
Abstract:Objective To propose a scheme to suture the cornea after sucking and raising the cornea to a height suitable for suturing by negative pressure, and conduct the simulation study on suction parameters. Methods According to surgical requirements, the corneal holder based on negative pressure suction was designed. The simulation models of sucking cornea with straight wound ( different types of length, depth and position) were established, and then the procedure of sucking cornea under 6 negative pressure conditions was simulated by fluid-structure interaction to solve the deformation, corneal stress and suction force. The suction force caused by the holder under 6 negative pressure conditions was measured on the PDMS film and compared with the simulation results. The operating safety of the proposed holder was evaluated by in vitro porcine eye experiment. Results The maximum corneal deformation in all simulation models under negative pressure from - 70 kPa to -40 kPa was greater than the maximum raising height of wound required for corneal suturing depth. The maximum corneal deformation increased with the negative pressure decreasing. The maximum corneal stress of all simulation models was less than the corneal stroma damage strength (5 MPa). The suction force of simulation was in good agreement with the experimental results. No corneal rupture occurred when the holder conducted the sucking operation under negative pressure higher than -70 kPa. Conclusions The corneal holder proposed in this study can meet the required depth in corneal suture surgery within the set negative pressure from - 70 kPa to -40 kPa, and can precisely control the suturing depth by changing the negative pressure. The corneal tissues will not be damaged under negative pressure higher than -70 kPa. With the assistance of the corneal holder, doctors can use a straight needle to conduct corneal suture surgery and reduce the difficulty of clinical operations.
Abstract:Objective To study the drug diffusion process in posterior eye under the biodegradation behavior of hydrogels, and to provide the research basis for evaluating local drug concentration and optimizing intraocular drug release performance of the biodegradable hydrogels. Methods Through finite element analysis, the drug delivery model of the biodegradable drug-loaded in-situ hydrogels in posterior eye was established. The effects of degradation of hydrogels, intraocular pressure and convection caused by active absorption of retinal pigment epithelial cells, as well as the effect of intraocular absorption and clearance on drug diffusion were considered to study the development of drug concentration in posterior eye. Results The intraocular drug diffused mainly to the posterior segment during drug release, and release rate of the drug-loaded hydrogels was significantly slower than that of the solution. Conclusions The biodegradable hydrogels prolong the residence time of drug in posterior eye by preventing movement of the drug center and limiting drug diffusion inside the hydrogels. Reasonable adjustment of the in-situ hydrogel injection position and degradation performance parameters can effectively improve its therapeutic effects.
Abstract:Objective To establish a finite element simulation system for the surgery of small incision lenticule extraction (SMILE) and provide foundation for the optimization of SMILE based on simulation results of corneal biomechanical properties, and to study the effect of corneal collagen cross-linking ( CXL) on biomechanical properties of the cornea after SMILE. Methods The mechanical behaviors of the cornea were characterized by hyperelastic constitutive relations with the consideration of gradient distributions of cross-linking strength. The indentation finite element model of SMILE was established. By setting up different surgical parameters such as incision position, incision length, side-cut angle and thickness of corneal cap, the corneal biomechanical behaviors after SMILE were simulated and analyzed. The finite element simulation under different irradiation doses was conducted to analyze the effect of CXL on the cornea after SMILE. Results The maximum von Mises stress increased as the angle of incision position decreased, the incision length increased, the side-cut angle changed from 90° to 135° or 45°, and the thickness of corneal cap decreased. Moreover, the maximum von Mises stress after CXL increased with the radiation dose increasing. Conclusions The finite element model of SMILE constructed in this study can effectively be used to characterize corneal biomechanical responses and provide simulation references for the optimization of SMILE. In addition, the reduced corneal biomechanical strength after SMILE can be effectively improved by CXL.
Abstract:Objective To investigate the hemodynamic changes and therapeutic effects of phacoemulsification and cataract extraction before and after treatment in patients with senile angle-closure glaucoma (ACG). Methods A total of 86 patients with senile ACG were randomly divided into control group ( n = 43) and experiment group (n= 43), and treated with trabeculectomy and phacoemulsification, respectively. For patients in both groups, the intraocular pressure ( IOP) and hemorheology, and their correlation with visual acuity, incidence of complica- tions, anterior chamber depth, and angle adhesion closure were observed and analyzed. Results Before treatment, there were no significant differences in visual acuity and IOP, plasma viscosity, hematocrit and platelet adhesion rate, anterior chamber depth and angle adhesion closure for patients in both groups (P>0. 05). After treatment, compared with the control group, the experiment group showed higher visual acuity (P<0. 05) and lower IOP ( P < 0. 05), lower incidence of complications ( P < 0. 05), as well as lower plasma viscosity,1039 hematocrit and platelet adhesion rate (P<0. 05). The anterior chamber depth and angle adhesion closure of the experiment group were significantly improved (P<0. 05), and the therapeutic effect was significantly higher (P< 0. 05). Conclusions Phacoemulsification and cataract extraction can effectively enhance the therapeutic effect for patients with senile ACG, further reduce the incidence of complications, promote the improvement of IOP and visual acuity, significantly improve anterior chamber depth and hemodynamic stability, effectively control angle adhesion closure, which can be promoted in the treatment for patients with senile ACG.
Abstract:Objective To investigate the influence of hyper-gravity environment on biomechanical properties and morphological structure of bone tissues, so as to provide theoretical support for safe flight training of astronauts and pilots and determination of the maximum tolerance value of hyper-gravity. Methods The hyper-gravity animal model was established by using the self-designed hyper-gravity loading platform. The loading mode was the ventral-dorsal direction which was subjected to centripetal acceleration of 5 g, 10 g, and 20 g, respectively (45 s, once a day, 5 d/ week, for 4 weeks). Instron 5865 material testing machine was used to perform three- point bending test on in vitro tibia, and the influence of hyper-gravity environment on mechanical properties of bone tissues was analyzed by measuring changes in mechanical parameters. Dual-energy X-ray absorptiometry, micro-CT scanning and bone tissue staining were utilized to test changes in bone mineral contents, bone mineral density, and to observe the influence of hyper-gravity environment on bone morphology. Results Hyper-gravity loading could reduce fracture stress and elastic modulus of the tibia in mice. The bone volume/ total volume (BV/ TV), trabecular thickness (Tb. Th) and trabecular number (Tb. N) were significantly decreased, and the trabecular arrangement was disordered under hyper-gravity environment. Conclusions The effect of hyper-gravity on biomechanical properties and morphological structure of bone tissues is related to the intensity of hyper- gravity. Low-strength ( 5 g) overload can reduce Tb. Th, but has little effect on its mechanical properties. Moderate ( 10 g) and high-strength ( 20 g) overload can significantly trigger bone loss and decrease bone mechanical properties. With the increase of hyper-gravity load, physiological regulation of the body can not prevent the decline of bone mass and mechanical properties.
Abstract:Objective To investigates the stress-strain relationship of ligaments under compression at different strain rates and construct a constitutive model, so as to provide references for prediction of ligament injury and development of replacement materials. Methods The compressive mechanical properties and compressive relaxation responses of rabbit patellar ligaments at different strain rates (0. 001, 0. 01, 0. 1, 1 s-1 ) were tested by universal tensile testing machine, and the corresponding constitutive equations were constructed. Results The uniaxial unconfined compression experiment showed that the stress and tangent modulus under 30% strain and 40% strain increased obviously with the increase of strain rate. Compared with the Gent model, the Fung model and Ogden model were more suitable for fitting the ligament compression curves ( R2 > 0. 99). The four-term Prony series were more suitable for fitting relaxation curves of the ligaments ( R2 > 0. 99). Conclusions The compressive mechanical properties of rabbit patellar ligaments demonstrate the significant viscoelastic response. The Fung model and Ogden model can be used to fit compressive response of the ligaments, and the four-term Prony series can be used to fit the compressive relaxation response of rabbit patellar ligaments.
Abstract:Objective To predict and evaluate biomechanical responses and injury mechanism of lower extremity for a small-sized female pedestrian in pedestrian-car collision. Methods The lower extremity geometric model with detailed anatomical structure was reconstructed based on CT images from the 5th percentile Chinese female volunteer. The finite element computational model was developed by optimizing the curved surface and meshing. The finite element model of pedestrian lower extremity was validated by reconstructing several cadaver tests, including dynamic three-point bending corpse experiments, and knee joint lateral bending and shearing cadaver experiments at high speed. Four simulation tests of pedestrian lower extremity-car collision as specified Euro NCAP TB024 were set up to investigate injury mechanisms of lower extremity of 5th percentile female pedestrian. Results The biomechanical computational model was validated to have high biofidelity by comparing the simulation test results with the cadaver test results. The lower extremity suffered the least injury in pedestrian- SUV collision. The femurs quickly fractured in simulations on four types of vehicle, so that no injury was found in knee ligaments. Conclusions This lower extremity finite element model is an important part of basic work for developing the 5th percentile Chinese female whole body computational model, which lays the foundation for model development. This study has important application values for studying injury mechanisms of female lower extremity and developing pedestrian protection devices.
Abstract:Objective To evaluate the biomechanical strength of individualized three-dimensional ( 3D) titanium alloy short femoral stem prosthesis. Methods A total of 12 adult cadaveric femur specimens were treated with artificial femoral head replacement with 4 kinds of short femoral stem prostheses: 3D printing group 1 (prosthesis A), 3D printing group 2 ( prosthesis B), BE 1 ( prosthesis C) and SMF ( prosthesis D). The deformation, maximum compressive load, maximum compressive displacement and compressive stiffness of the four prosthesis models were compared and analyzed through initial stability test and static compression test on the universal material mechanics testing machine. Results The initial stability test results showed that the deformation of 3D printing group 1 was slightly lower than that of 3D printing group 2, and the deformation of 3D printing group 1 was significantly lower than that of SMF group and BE group, but the difference was not statistically significant ( P > 0. 05). The maximum compressive load and compressive stiffness of 3D printing group 1 were higher than those of the other three groups, and the maximum compressive displacement was lower than that of the other three groups, but the difference was not statistically significant (P>0. 05). Conclusions The mechanical properties of individualized 3D printing titanium alloy short femoral stem prosthesis are similar to those of SMF and BE 1 prosthesis that are used frequently in clinic, and its mechanical stability is good.
Abstract:Objective The finite element models of knee joint before and after mobile-bearing unicompartmental knee arthroplasty (MB-UKA) were established, and the influence from posterior inclinations of tibial prosthesis on contact stress of tibio-femoral joints was studied. Methods Based on computed tomography (CT) and magnetic resonance (MR) images from a healthy subject, the finite element model of healthy knee joint was developed, and the validity of knee joint model before and after MB-UKA was verified. MB-UKA with 7° posterior inclination of tibial component was simulated, and the maximum contact stress of tibial plateau cartilage in lateral compartmen and polyethylene insert was calculated based on joint forces obtained by three-dimensional (3D) motion capture system in MB-UKA model. Results The comparison with results from present literatures showed that calculation results of healthy knee joint model and post-MB-UKA knee joint model were reasonable. The maximum contact stress on polyethylene insert after MB-UKA was greater than that on tibial plateau cartilage in lateral compartment. Conclusions The established finite element models before and after MB-UKA were verified. This study provides a referable method for MB-UKA evaluation.
Abstract:Objective To study the patterns of stress distributions on the area around the acetabulum during normal gait cycle, and to further explore the distribution of biology force lines of each column of the acetabulum as well as the thickness morphology of cortical bones. Methods The muscle and hip loads under 8 typical phases of human gait cycle were obtained through human reverse dynamics analysis. The three-dimensional (3D) model of hip joint was built by 3D reconstruction technology, and the finite element analysis and topology optimization of cortical bones were conducted by using the obtained loads as loading boundary conditions. Results In support phase, the hip joint load was larger, the strain energy of the middle column accounted for 55% -69% of the total strain energy, and the stress at top of the acetabulum was larger. In swing phase, the hip joint load decreased and the percentage of strain energy in the middle column decreased. Different motion angles of the hip joint affected muscle forces and further affected stress distributions on hip joints. The obtained biology force lines of each column of the acetabulum based on finite element method were basically consistent with biology force lines and bone trabecular arrangement proposed by the anatomy, and corresponded to thicker areas of cortical bones in topology optimization simulation results. Conclusions Biology force lines of each column of the acetabulum and thickness morphology distributions of cortical bones can be determined by numerical simulation, which provides theoretical references for reasonable placement of the internal fixation for fracture treatment.
Abstract:: Objective To establish a simplified mechanical model of L4-5 movable lumbar segment according to the sagittal curve of human spine, and to verify and analyze validity of the model structure. Methods An in vitro measurement device based on the time-of-flight (ToF) distance measurement principle was used to obtain the sagittal curve of human spine. Based on the curve, the simplified mechanical model of L4-5 lumbar segment was constructed, and validity of the model was verified from the aspects of range of motion (ROM), intervertebral disc pressure (IDP) and facet joint force (FJF). Results The maximum IDP under 0. 2, 0. 4, 0. 6, 0. 8 and 1 kN follower load (FL) was 0. 23, 0. 46, 0. 69, 0. 92 and 1. 15 MPa, respectively. The ROM of models during flexion, extension, lateral flexion and axial torsion under pure moment were 6. 61°, 4. 03°, 3. 30° and 2. 03°, respectively. The IDPs of models during flexion, extension, lateral flexion and axial torsion under the combined load of FL and moment were 1. 80, 1. 00, 1. 36, 0. 80 MPa, respectively. The FJFs of models during extension, lateral bending and axial rotation were 79. 60, 29. 49, 96. 64 N, respectively. Conclusions The simplified mechanical model based on sagittal curve of human spine can be used for spinal mechanical analysis on changes in sagittal curve of the spine.
Abstract:Objective To make biomechanical analysis on soft tissues in the formation of postburn claw hand deformity and during its two traction orthodontic treatments. Methods The hand model containing skin and scar was established, and the scar contracture-tendon and ligament contracture-scar excision with skin grafting- traction orthodontic treatment process for postburn claw hand deformity was simulated. Biomechanical analysis on relevant soft tissues was performed, and the advantages and disadvantages of the two traction modes were compared. Results The associated flexors and extensors were stretched when scar contracture occurred. The dorsolateral ligaments at the metacarpophalangeal ( MCP) joints were relaxed and most of the lateral collateral ligaments were tensed. After surgical treatment, the deformity was largely relieved. Tension or laxity of the tendons was reduced. The tensed lateral collateral ligaments were relaxed and the contracted dorsolateral ligaments were stretched. Traction orthodontic treatment was gainful for scar removal surgery. For postburn claw hand deformity, the treatment protocol of dynamic traction applied directly after scar release set up in this study was safe and effective, and had a better promotion effect on tendon elongation. In terms of traction effect, the elongated traction method showed more advantages than the antagonistic traction. Conclusions The research results may provide references for clinical interventions and prognosis improvement of patients.
Abstract:Objective The three-dimensional ( 3D ) modeling of customized polyetheretherketone ( PEEK ) temporomandibular joint (TMJ) prosthesis was performed, and the stress distribution characteristics of prosthesis with three different condylar head shapes ( prototype, 80% prototype and cylindrical) were analyzed by finite element method, so as to evaluate the effects of three different condylar head morphology on stability, joint movement and articular fossa of PEEK total TMJ prosthesis. Methods The finite element analysis modelsⅠ,Ⅱ and Ⅲ of the cranio-maxillo facial and PEEK full TMJ prosthesis were established. Under four different occlusal conditions, i. e. , intercuspal position ( ICP), incisal clench ( INC), left unilateral molar clench ( LMOL), and right unilateral molar clench (RMOL), the maximum stress of the articular fossa prosthesis, condyle prosthesis and titanium scrows, the stress and strain distribution of the mandible, and the maximum displacement of the three models were analyzed. Results The maximum stresses of PEEK total joint prosthesis and screws in 3 models were 35. 22 MPa and 16. 73 MPa, respectively, which were lower than yield strength of the materials. The maximum stress of the mandible in modelsⅠ,Ⅱand Ⅲ were 41. 47, 42. 84 and 56. 92 MPa, and the strain was 3. 896× 10-3 , 2. 175 × 10-3 , 4. 641 × 10-3 , respectively. The maximum displacement of the three models was 209. 0 μm, which was located at the left mandibular angle of model Ⅲ. Conclusions PEEK TMJ prostheses with three different condylar head shapes all show uniform stress distribution, but the joint prostheses with 80% of the prototype condyle head shape have better mechanical effects. This study provides theoretical basis for the design of PEEK TMJ.
Abstract:Objective To explore the optimal strategy for fiber-reinforced composite (FRC) post-and-resin core restoration on an endodontically-treated maxillary first molar with a disto-occluso-palatal ( DOP ) defect. Methods Eight different finite element models of FRC post-resin core restored maxillary first molar were established. In the multi-post groups, the thinner post was horizontally trimmed 1 mm below the intersection point as the adjunct post, and the thicker one was resignated as the main post. The 800 N vertical force parallel to the long axis of the tooth and 225 N lateral force directed at 45° to the long axis of the tooth were applied. The equivalent stresses on external surfaces of tooth tissues, internal surfaces of root canals and in the posts, as well as the maximum shear stresses on post-cement interfaces and cement-dentin interfaces were calculated with finite element analysis. Results All the models showed similar distribution patterns of equivalent stress on external surfaces of tooth tissues under the same loading. The maximum equivalent stress was found on palatal (P) side of the root trunk under vertical loading, and on mesiobuccal ( MB) side of root trunk under lateral loading. On internal surfaces of root canals, the maximum equivalent stress increased at the middle third of post- placed canal, and decreased at the cervical third of the canal. Under vertical loading, P posts showed the highest equivalent stress, while MB posts showed the highest equivalent stress under lateral loading. Under vertical loading, the main post encountered larger shear stress than the assistant one on post-cement interface in the same canal. Under lateral loading, post-cement interface in MB canal showed the highest shear stress. The highest shear stress appeared on cement-canal interface with a P post under vertical loading, and with an MB post under lateral loading. Conclusions The FRC post restoration can transmit occlusal force towards apical area, so as to improve stress distributions in residual tooth tissues for a maxillary first molar with DOP defect. One post in the P canal may be the best strategy of FRC post and resin core restoration for an endodontically- treated maxillary first molar with a DOP defect.
Abstract:Objective To propose a personalized design, optimization and manufacturing method of three- dimensional (3D) printed implants for repairing large area of maxillary defect. Methods Based on the patient’s cone beam computer tomography (CBCT) and oral scan data information, the implant design was optimized at first. The structure and material selection of the implant were iteratively optimized by finite element analysis method . The force of the implant in oral cavity was simulated, the stress magnitude, conduction direction and distributions of the implant were obtained, and the implant structure was optimized accordingly. Finally, the maximum equivalent stress of the implant and the mandible, as well as the total displacement of titanium screws with the same configuration under three different materials, namely, titanium alloy, tantalum metal and polyetheretherketone (PEEK) were obtained, so as to determine printing material of the implant. Finally, the implant was printed using 3D printing technology, and facial remodeling and occlusal reconstruction were completed in clinic. Results Through iterative optimization of the structure, the best configuration of the implant was obtained, and the titanium alloy material was selected. The 3D printed implants were used in clinic to complete occlusal reconstruction. Conclusions The method described in this study has clinical feasibility and is suitable for different types of maxillary defect cases. The designed implant is accurate in size and has preferable mechanical properties. It can not only restores the patient’s maxillofacial appearance, but also meets the clinical needs of occlusal reconstruction after maxillofacial defect repair.
Abstract:Objective To realize the online estimation of airway resistance ( R) by applying positive airway pressure in ventilation treatment. Methods At the end of expiration when the airflow was zero, with a negative pulse pressure superposed upon the expiratory positive airway pressure (EPAP), a discharged airflow in the airway was produced, and the R and C were calculated with the discharged airflow. Then, taking the simulated normal adult, typical patients with acute respiratory distress syndrome (ARDS) and patient with chronic obstructive pulmonary disease (COPD) as experimental subjects, a simulated platform was established and the simulation experiments were conducted to calculate R and C. Results The errors in R and C were 3. 398% and -3. 288% for the simulated normal adult, 1. 265% and -1. 348% for the simulated patient with COPD, 3. 400% and -3. 286% for the simulated patient with ARDS, respectively. Conclusions The method with a negative pulse pressure superposed upon the EPAP to conduct the R and C is well practicable. This study lays solid foundation for the technology of intelligent and precision ventilation.
Abstract:Objective To developed a data-driven method for fast calculation of coronary microcirculation resistance. Methods The neural network was constructed and optimized to extract cross-sectional area features of coronary arteries. The microcirculation resistance at the end of the coronary branch was quickly calculated by using cross-sectional area features, allometric scaling law and flow distribution ratio, and the blood flow reserve fraction was non-invasively calculated based on microcirculation resistance. Results In order to verify validity of the neural network, the cross-sectional area characteristics of 40 clinically collected coronary artery branch measurements were compared with predicted result of the neural network, and the mean absolute error value was 1. 08 mm2 . In order to verify accuracy of the microcirculation resistance, the clinical fractional flow reserve of 15 patients was compared with the fractional flow reserve calculated by the microcirculation resistance, and the calculation accuracy was 86. 6% . Conclusions The rapid calculation method of coronary microcirculation resistance proposed in this study has potential clinical application value.
Abstract:: Objective To analyze the influence of different loads (abdominal pressure and uterine weight) on stress and deformation of uterine ligaments using the finite element method, and obtain the sensitivity of each accessory ligament to the changes of load on uterus. Methods The three-dimensional (3D) models of retroverted uterus and its accessory ligaments were established, loads and constraints were set in ABAQUS software, and the stress and deformation of uterine ligaments were calculated. Results The changes of abdominal pressure and uterine weight alone or both together would cause tensile deformation of uterine ligaments, and the deformation and stress increased with the load increasing. The deformation and stress were mainly distributed in the middle and lower part of each ligament or at the junction with uterus. The maximum stress and displacement were concentrated at the junction of each ligament with uterus or pelvic wall, and uterus weight had a greater influence on the ligaments than abdominal pressure. When abdominal pressure changed alone or together with uterine weight, the stress and sensitivity to load changes of the ligaments were in the order of uterosacral ligament (USL), broad ligament (BL), cardinal ligament (CL) and round ligament (RL). When uterine weight changed alone, the stress and sensitivity to load changes of the ligaments were in the order of USL>CL >RL >BL. The deformation and sensitivity to load changes of the ligaments remained unchanged and the order was BL>RL>USL>CL. Conclusions The sensitivity of each uterine ligament changing with uterine load was studied through finite element analysis, and the research results were consistent with the clinical data, which could provide guidance for optimization of surgical scheme of uterus prolapsed in clinic and exploration of pathogenesis.
Abstract:Objective Considering the characteristics of gallbladder under healthy and pathological conditions, biomechanical properties of gallbladder wall and hydrodynamic characteristics of bile, as well as the correlation between motor function of gallbladder and genesis of gallstones were studied. Methods The three-dimensional (3D) structure model of gallbladder was constructed by using CT image data. The finite element model was established to simulate the movement of gallbladder and the flow process of bile, so as to analyze the movement mode of gallbladder and its influence on gallstones formation under different fluid-solid coupling conditions. Results Gallbladder motor function was closely related to biomechanical characteristics. Under the same boundary conditions, the flow velocity of calculous bile (1. 1 cm / s) was lower than that of normal bile (2. 3 cm / s). The abnormality of gallbladder motor function would not change the flow pattern of bile, but the change of bile composition would make the flow pattern more tortuous. The maximum stress and maximum deformation of gallbladder with weak motor function were 1. 079 kPa and 0. 931 mm, which were far smaller than the maximum stress (4. 318 kPa) and maximum deformation (3. 725 mm) of healthy gallbladder. In terms of stress, abnormal bile composition did not have much impact on gallbladder. Conclusions When the motor function of gallbladder is damaged and weakened, the contraction will be greatly reduced and gallstones are more likely to occur. The 3D model of gallbladder and analysis of motor function can provide necessary theoretical basis and technical means for surgical treatment of gallstones.
Abstract:Objective To simulate foot-ankle stresses at different push-off ankles in ice skating, so as to obtain a reasonably quantitative relationship between push-off angle and foot-ankle stress through optimization analysis. Methods The finite element coupling model of ice hockey shoes and foot-ankle was established, then the kinematic parameters of ice hockey players were obtained by three-dimensional ( 3D) photography for model validation and boundary. The foot-ankle stresses at different push-off angles were calculated and compared, and the multi-objective optimization function model was constructed. Results At the same push-off angle, the stress of the tibia and fibula was the largest, followed by the subtalar joint stress, then the first metatarsophalangeal joint stress, and finally the plantar fascia stress was the smallest. As the angle of push-off decreased, the foot-ankle stresses increased monotonously. The stress changes of the tibia and fibula and the plantar fascia were large, and the stress changes of the subtalar joint and the first metatarsophalangeal joint were relatively smaller. Conclusions During the start-up push-off phase of ice hockey, the push-off angle and foot-ankle stress show an inversely proportional relationship. The optimal push-off angle depends on the expected value of skating speed. If the preference coefficient between speed and stress tolerance is given, the optimal push-off angle can be calculated by optimization method.
Abstract:Objective To investigate the effects of unstable support surface (USS) training on balance, gait and lower limb motor function in patients with chronic stroke. Methods Twenty stroke patients were divided into two groups. Control group ( n= 10) received 12 weeks of routine rehabilitation training on the basis of conventional treatment, and experimental group ( n= 10 ) received 12 weeks of balance plate training on the basis of conventional treatment. BBS scale, Fugl-Meyer lower limb function scale, 10-meter walking speed test(10 MWT) and 6-minute walking distance test ( 6 MWD) were used to evaluate dynamic balance, walking and lower limb motor function before and after intervention. NeuroCom Balance Manager system, Qualisys 3D motion capture and analysis system and Kistler 3D force platform were used to measure the patient’s static balance, as well as their kinematics and dynamic gait data before and after intervention. Results After intervention, the differences in BBS score, Fugl-Meyer score and 6 MWD score between control group and experimental group as well as between experimental groups had statistical significance(P<0. 05), and the difference in 10 MWT score between experimental groups was statistically significant (P< 0. 05). After intervention, the difference in weigh-bearing/ squat (WB/ S) between control group and experimental group as well as between experimental groups at 90° and 60° had statistical significance (P<0. 05), and the difference in WB/ S between experimental groups at 30° and 0° was statistical significant(P<0. 05). After intervention, the differences in center of pressure (COP) symmetry and hip joint symmetry between control group and experimental group had statistical significance (P<0. 05), while the difference in symmetry of knee joint and ankle joint was not statistically significant(P>0. 05). Conclusions USS training with NeuroCom Balance Manager Balance board can effectively improve balance, gait and lower limb motor function in stroke patients.
Abstract:Objective To reveal the gait pattern differences between higher-mileage runners ( HMR) and low-mileage runners ( LMR) by using the deep neural network ( DNN) classification model, and investigate the interpretability analysis of successfully recognized gait patterns by layer-wise relevance propagation ( LRP) technique. Methods Through DNN, 1 200 groups of gait feature data from HMR and LMR were trained and classified. Then, the LRP was used to calculate the relevance score ( RS) of relevant variables at each time point, and the high relevance variables were extracted to analyze the interpretability of gait pattern differences. Results The DNN model achieved 91. 25% accuracy in gait feature classification between HMR and LMR. The contribution of variables during 1% -47% stance phase was higher than the contribution of variables during the 48% -100% stance phase to the successful classification. The sum contribution rate of the ankle joint related trajectory variable RS reached 43. 10% , and that of the knee joint and hip joint was 37. 07% and 19. 83% , respectively. Conclusions The ankle and knee provide considerable information can help recognize gait features between HMR and LMR. The early stages of the stance are very important in the term of gait pattern recognition because it may contain more effective information about gait patterns. LRP completes a feasible interpretation of the predicted result of the model, thus providing more interesting insights and more effective information for analyzing gait patterns.
Abstract:Objective To explore the effects of wearing running shoes with different heel-to-toe drops on lower limb joint loading at the same running speed, so as to provide references for the design of running shoes and for runners to buy running shoes. Methods A total of 18 male runners completed the running test by wearing shoes with 0 mm and 10 mm heel-to-toe drops at the speed of (4. 0±0. 2) m / s, the kinematic parameters and ground reaction force (GRF) of lower limbs were collected synchronously by using infrared high-speed motion capture system and three-dimensional (3D) force plates. Statistical parameter mapping (SPM) was used to analyze the effects from heel-to-toe drop of running shoes on GRF as well as 3D moments of lower limb joints during stance phase. Results The heel-to-toe drop of running shoes had no effects on vertical GRF, but had significant effects on moment-time series of lower limb joints. Compared with wearing 0 mm heel-to-toe drop running shoes, wearing running shoes with 10 mm heel-to-toe drop increased the hip internal rotation moments in 27% -38% of stance phase and the knee extension moments in 47% -75% of stance phase, meanwhile decreased the plantar flexion moments, valgus moments and external rotation moments of ankle joints in 16% -33% , 25% -30% and 12% - 25% of the stance phase, respectively. Conclusions Compared with wearing 0 mm heel-to-toe drop running shoes, wearing running shoes with 10 mm heel-to-toe drop increases the hip joint loading, decreases the ankle joint loading in early stance phase, and increases the knee joint loading in middle stance phase. It is suggested that runners choose running shoes according to their own characteristics and the effects of heel-to-toe drop of running shoes on lower limb joint loading.
Abstract:Objective To explore the transformation mechanism and changing law of foot arch function in support phase during walking through the analysis of gait parameters and foot arch mechanical structures. Methods Gait parameters, transverse and longitudinal arch angles of 8 subjects at different walking speeds were collected synchronously by motion capture system and plantar pressure test system. One-way repeated measure anova was used to test differences in characteristic values of foot transverse and longitudinal arch angles as well as plantar forces at different speeds. Results In support phase, two eigenvalues appeared in curve of longitudinal arch angle, transverse arch angle and plantar force, and the eigenvalues of three curves were consistent at four types of walking speeds. During walking at 1. 4 and 1. 2 times of the optimum speed, the time of push-off stage was significantly longer than that at 0. 8 times of the optimal speed (P<0. 05). The inflection point and the first peak of the transverse arch appeared earlier than those at 0. 8 times of the optimal speed ( P < 0. 05). The minimum transverse arch angle at 1. 4 times of the optimal speed was significantly larger than that at 0. 8 times of the optimal speed ( P < 0. 05 ), while the time when the minimum angle appeared was significantly earlier (P<0. 05). During walking at 1. 2 times of the optimal speed, the position for the second peak of the longitudinal arch appeared earlier than that at the optimal speed (P< 0. 05). Conclusions In support phase during walking, foot function transformation was realized by both the longitudinal arch and transverse arch. The longitudinal and transverse arch of the foot were lowered to complete buffer function, and the longitudinal arch of the foot was lowered while the transverse arch was raised to increase foot stiffness to complete the push-off function. The faster pace would increase time proportion of the push-off stage in support phase, while the change of the transverse arch and longitudinal arch was advanced. Exploring the change of foot arch and the mechanism of foot function transformation has important guiding significance for understanding the law of foot movement as well as ankle rehabilitation.
Abstract:Glaucoma is an ophthalmic disease with abnormally elevated intraocular pressure as the main risk factor. Trabecular meshwork is the main channel for the outflow of aqueous humor and is very important for regulating intraocular pressure. Studies have shown that the elasticity of trabecular meshwork in patients with glaucoma is significantly higher than that of normal people. The increase in intraocular pressure may be associated with the increase in trabecular meshwork elasticity. Based on the brief description of characteristic of trabecular meshwork cells, this article focused on the relationship between trabecular meshwork elasticity and glaucoma, as well as the effect of extracellular matrix elasticity on trabecular meshwork cells, so as to study glaucoma pathogenesis and provide references for prevention and treatment.
Abstract:Cell migration is a basic physiological activity of cells. Cell migration not only plays an important role in vascular reconstruction, inflammatory response, tissue development, wound healing, etc. , it is also related to the invasion and metastasis of cancer cells. Plectin (499-533 kDa) is a macromolecular skeleton protein widely expressed in various tissues and cells. It has important biological functions and participates in many physiological and pathological processes of cells. Plectin can affect migration by regulating the cytoskeleton and through related signaling pathways. This review focused on the role of plectin in cancer cell migration and its related molecular mechanisms, and provided the theoretical basis to further understand and study the relationship between plectin and cancer cell migration and its targeted intervention.
Abstract:Airway stenosis is a congenital or common clinical disease caused by infection, tumor, trauma, tuberculosis and other diseases, and its common causes in China include tracheobronchial tuberculosis, benign or malignant tumors, etc. Implantation of airway stents has become one of the main ways for interventional treatment of airway stenosis. Airway stent develops from silicone stent to engraved stent and braided stent, and its materials and configurations have been continuously replaced and improved. However, problems such as stent displacement, tracheal granuloma, and restenosis after airway stent implantation still remain unsolved. These issues are related to the mechanical effects on tracheal tissues as a whole after stent implantation. In this paper, mechanical properties of airway stents and typical numerical simulation studies of stents and trachea were summarized. Mechanical properties include stent radial force, kink resistance and yield stress, which will be affected by stent materials, configuration design, manufacturing process, etc. Numerical simulation method can efficiently provide technical support for airway stent development, which provides references for stent material selection, design improvement and manufacturing.
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