The microgravity environment of a long-term space flight may induce acute changes in an astronaut＇s musculo-skeletal systems. This study explores the effects of simulated microgravity on the mechanical characteristic...The microgravity environment of a long-term space flight may induce acute changes in an astronaut＇s musculo-skeletal systems. This study explores the effects of simulated microgravity on the mechanical characteristics of articular cartilage. Six rats underwent tail suspension for 14 days and six additional rats were kept under normal earth gravity as controls. Swelling strains were measured using high-frequency ultrasound in all cartilage samples subject to osmotic loading. Site-specific swelling strain data were used in a triphasic theoretical model of cartilage swelling to determine the uniaxial modulus of the cartilage solid matrix. No severe surface irregularities were found in the cartilage samples obtained from the control or tail-suspended groups. For the tail-suspended group, the thickness of the cartilage at a specified site, as determined by ultrasound echo, showed a minor decrease. The uniaxial modulus of articular cartilage at the specified site decreased significantly, from （6.31 ± 3.37） MPa to （5.05 ± 2.98）MPa （p 〈 0.05）. The histology- stained image of a cartilage sample also showed a reduced number of chondrocytes and decreased degree of matrix staining. These results demonstrated that the 14 d simulated microgravity induced significant effects on the mechanical characteristics of articular cartilage. This study is the first attempt to explore the effects of simulated microgravity on the mechanical characteristics of articular cartilage using an osmotic loading method and a triphasic model. The conclusions may provide reference information for manned space flights and a better understanding of the effects of microgravity on the skeletal system.展开更多
Two clinical ablation protocols, 2C3L and stepwise, have been routinely used in our group to treat atrial fibrillation （AF）, but with a less than 60% long-term arrhythmia-free outcome achieved in patients. The goal ...Two clinical ablation protocols, 2C3L and stepwise, have been routinely used in our group to treat atrial fibrillation （AF）, but with a less than 60% long-term arrhythmia-free outcome achieved in patients. The goal of this study was to examine the underlying mechanism of low success in clinical outcome. MRI images from one patient were used to reconstruct a human atrial anatomical model, and fibrotic tissue was manually added to represent the arrhythmia substrate. AF was induced with standard protocols used in clinical practice. 2C3L and stepwise were then used to test the efficacy of arrhythmia termination in our model. The results showed that re-entries induced in our model could not be terminated by using either 2C3L or the stepwise protocol. Although some of the induced re-entries were terminated, others emerged in new areas. Ablation using only the 2C3L or stepwise method was not sufficient to terminate all re-entries in our model, which may partially explain the poor long-term arrhythmiafree outcomes in clinical practice. Our findings also suggest that computational heart modelling is an important tool to assist in the establishment of optimal ablation strategies.展开更多
Postoperative tunnel enlargement has been frequently reported after anterior cruciate ligament（ACL）reconstruction.Interference screw,as a surgical implant in ACL reconstruction,may influence natural loading transmis...Postoperative tunnel enlargement has been frequently reported after anterior cruciate ligament（ACL）reconstruction.Interference screw,as a surgical implant in ACL reconstruction,may influence natural loading transmission and contribute to tunnel enlargement.The aims of this study are（1）to quantify the alteration of strain energy density（SED）distribution after the anatomic single-bundle ACL reconstruction;and（2）to characterize the influence of screw length and diameter on the degree of the SED alteration.A validated finite element model of human knee joint was used.The screw length ranging from 20 to 30 mm with screw diameter ranging from 7 to 9 mm were investigated.In the post-operative knee,the SED increased steeply at the extra-articular tunnel aperture under compressive and complex loadings,whereas the SED decreased beneath the screw shaft and nearby the intra-articular tunnel aperture.Increasing the screw length could lower the SED deprivation in the proximal part of the bone tunnel;whereas increasing either screw length or diameter could aggravate the SED deprivation in the distal part of the bone tunnel.Decreasing the elastic modulus of the screw could lower the bone SED deprivation around the screw.In consideration of both graft stability and SED alteration,a biodegradable interference screw with a long length is recommended,which could provide a beneficial mechanical environment at the distal part of the tunnel,and meanwhile decrease the bone-graft motion and synovial fluid propagation at the proximal part of the tunnel.These findings together with the clinical and histological factors could help to improve surgical outcome,and serve as a preliminary knowledge for the following study of biodegradable interference screw.展开更多
Carotid artery stenting presents challenges of in-stent restenosis and late thrombosis, which are caused primarily by alterations in the mechanical environment of the artery after stent implantation. The present study...Carotid artery stenting presents challenges of in-stent restenosis and late thrombosis, which are caused primarily by alterations in the mechanical environment of the artery after stent implantation. The present study constructed patient-specific carotid arterial bifurcation models with lipid pools and calcified components based on magnetic resonance imaging. We numerically analyzed the effects of multicomponent plaques on the distributions of von Mises stresses (VMSs) in the patient-specific models after stenting. The results showed that when a stent was deployed, the large soft lipid pool in atherosclerotic plaques cushioned the host artery and reduced the stress within the arterial wall; however, this resulted in a sharp increase of VMS in the fibrous cap. When compared with the lipid pool, the presence of the calcified components led to slightly increased stresses on the luminal surface. However, when a calcification was located close to the luminal surface of the host artery and the stenosis, the local VMS was elevated. Overall, compared with calcified components, large lipid pools severely damaged the host artery after stenting. Furthermore, damage due to the calcified component may depend on location.展开更多
The primary cilium,as a mechanical receptor of osteocytes,participates in the regulation of osteocyte mechanosensitivity.However,how the length of osteocyte primary cilia changes with fluid shear stress(FSS)are unclea...The primary cilium,as a mechanical receptor of osteocytes,participates in the regulation of osteocyte mechanosensitivity.However,how the length of osteocyte primary cilia changes with fluid shear stress(FSS)are unclear,and how the mechanical transmission within osteocytes altered by primary cilia is not well understood yet.Therefore,the ciliary length changes of osteocyte under 15dyn/cm2 of FSS were experimentally detected,and then 3D finite element models of osteocyte primary cilia containing the basal body and axoneme were built.The results showed that(1)The ciliary length of the CON group,FSS 1h,and FSS 6h were 3.71±1.34μm,3.79±1.04μm,and 1.24±0.73μm respectively,indicating the different durations of FSS might lead to the adaptive changes of cilium length.The calculations showed(2)when the ciliary length became shorter with the ciliary angle stayed the same,the deformation and stress of the cell membrane and membrane skeleton was increased.However,the deformation and stress of the cilia membrane,basal body,the rotation angles of basal body were decreased,and those of cytoplasm,cytoskeleton,actin cortex and nucleus were also decreased;(3)With the decrease of the ciliary angle,the deformation and stress of the cilia membrane,basal body,as well as the rotation angles of basal body were increased.Those of the cytoplasm,cytoskeleton,actin cortex,and nucleus were also increased except the cell membrane and membrane skeleton.The calculation results suggested the length and angle of the primary cilia,the deformation and stress of intracellular structures in osteocyte were altered with ciliary basal body,indicated the connection between the basal body and cytoskeleton may be a key factor that affected the mechanical transport in osteocytes across the cell membrane.This finally promoted the adaptive change of ciliary length under FSS.展开更多
Temperature-sensitive random copolymerized nanohydrogels were prepared via a one-pot polymerization method using N-isopropylacrylamide(NIPAM)and 2-acrylamido-2-methylpropanesulfonic acid(AMPS)as raw materials.Transmis...Temperature-sensitive random copolymerized nanohydrogels were prepared via a one-pot polymerization method using N-isopropylacrylamide(NIPAM)and 2-acrylamido-2-methylpropanesulfonic acid(AMPS)as raw materials.Transmission electron microscopy(TEM)and differential scanning calorimetry(DSC)analyses revealed the partially crystallized porous nanostructure of the gels,which is consistent with the characteristics of porous nanohydrogel materials.The low-molecular-weight polymers exhibited enhancement and sharpening of the end group peaks in Fourier-transform infrared(FTIR),X-ray photoelectron spectroscopy(XPS),and nuclear magnetic resonance hydrogen(^(1)H-NMR)spectra due to the high proportion of small molecules or low-molecular-weight chain segments.In turn,the high-molecular-weight polymers showed pronounced peaks in the main chain segments because of the long-chain effect.Hygroscopicity increased with the molecular weight of the selected polymers,but was inhibited by temperatures below the lower critical solution temperature(LCST).Meanwhile,moisture desorption was faster in low-molecular-weight samples,and the overall moisture desorption rate rose above the LCST value.According to the kinetic analysis,the moisture absorption process conformed to the quasi-primary or quasi-secondary kinetic model,whereas the moisture desorption followed the quasi-secondary model.Moisture cycling experiments showed that the material maintained stable moisture absorption and desorption performance after several cycles,which is essential for long-term cycling.展开更多
Background： Sacroiliac （SI） screw fixation is a demanding technique, with a high rate of screw malposition due to the complex pelvic anatomy. TiRobot- is an orthopedic surgery robot which can be used for SI screw f...Background： Sacroiliac （SI） screw fixation is a demanding technique, with a high rate of screw malposition due to the complex pelvic anatomy. TiRobot- is an orthopedic surgery robot which can be used for SI screw fixation. This study aimed to evaluate the accuracy of robot-assisted placement of SI screws compared with a freehand technique. Methods：Thirty patients requiring posterior pelvic ring stabilization were randomized to receive freehand or robot-assisted SI screw fixation, between January 2016 and June 2016 at Beijing Jishuitan Hospital. Forty-five screws were placed at levels S1 and S2. In both methods, the primary end point screw position was assessed and classified using postoperative computed tomography. Fisher＇s exact probability test was used to analyze the screws＇positions. Secondary end points, such as duration of trajectory planning, surgical time after reduction of the pelvis, insertion time for guide wire, number of guide wire attempts, and radiation exposure without pelvic reduction, were also assessed. Results： Twenty-three screws were placed in the robot-assisted group and 22 screws in the freehand group; no postoperative complications or revisions were reported. The excellent and good rate of screw placement was 100% in the robot-assisted group and 95% in the freehand group. The P value （0.009） showed the same superiority in screw distribution. The fluoroscopy time after pelvic reduction in the robot-assisted group was significantly shorter than that in the freehand group （median [Q1, Q3]： 6.0 [6.0, 9.0] s vs. median [Q1, Q3]： 36.0 [21.5, 48.0] s; χ2 = 13.590, respectively, P 〈 0.001）; no difference in operation time after reduction of the pelvis was noted （χ2 = 1.990, P = 0.158）. Time for guide wire insertion was significantly shorter for the robot-assisted group than that for the freehand group （median [Q1, Q3]： 2.0 [2.0, 2.7] min vs. median [Q1, Q3]： 19.0 [15.5, 45.0] min; χ2 = 20.952, respectively, P 〈 0.001）. The number of guide wire attempts in the robot-assisted group was significantly less than that in the freehand group （median [Q1, Q3]： 1.0 [1.0,1.0] time vs. median [Q1, Q3]： 7.0 [1.0, 9.0] times; χ2 = 15.771, respectively, P 〈 0.001）. The instrumented SI levels did not differ between both groups （from S1 to S2, χ2 = 4.760, P = 0.093）. Conclusions： Accuracy of the robot-assisted technique was superior to that of the freehand technique. Robot-assisted navigation is safe for unstable posterior pelvic ring stabilization, especially in S1, but also in S2. SI screw insertion with robot-assisted navigation is clinically feasible.展开更多
Lower-limb assisted exoskeletons are widely researched for movement assistance or rehabilitation training.Due to advantages of compliance with human body and lightweight,some cable-driven prototypes have been develope...Lower-limb assisted exoskeletons are widely researched for movement assistance or rehabilitation training.Due to advantages of compliance with human body and lightweight,some cable-driven prototypes have been developed,but most of these can assist only unidirectional movement.In this paper we present an untethered cable-driven ankle exoskeleton that can achieve plantarflexion-dorsiflexion bidirectional motion bilaterally using a pair of single motors.The main weights of the exoskeleton,i.e.,the motors,power supplement units,and control units,were placed close to the proximity of the human body,i.e.,the waist,to reduce the redundant rotation inertia which would apply on the wearer’s leg.A cable force transmission system based on gear-pulley assemblies was designed to transfer the power from the motor to the end-effector effectively.A cable self-tension device on the power output unit was designed to tension the cable during walking.The gait detection system based on a foot pressure sensor and an inertial measurement unit(IMU)could identify the gait cycle and gait states efficiently.To validate the power output performance of the exoskeleton,a torque tracking experiment was conducted.When the subject was wearing the exoskeleton with power on,the muscle activity of the soleus was reduced by 5.2%compared to the state without wearing the exoskeleton.This preliminarily verifies the positive assistance effect of our exoskeleton.The study in this paper demonstrates the promising application of a lightweight cable-driven exoskeleton on human motion augmentation or rehabilitation.展开更多
Background：Previous studies have shown that hypertension is an important factor contributing to the occurrence and progression of diabetic kidney damage.However,the relationship between the patterns of blood pressure...Background：Previous studies have shown that hypertension is an important factor contributing to the occurrence and progression of diabetic kidney damage.However,the relationship between the patterns of blood pressure （BP） trajectory and kidney damage in the diabetic population remains unclear.This prospective study investigated the effect of long-term systolic BP （SBP） trajectory on kidney damage in the diabetic population based on an 8-year follow-up community-based cohort.Methods：This study included 4556 diabetic participants among 101,510 participants.BP,estimated glomerular filtration rate （eGFR）,and urinary protein were measured every 2 years from 2006 to 2014.SBP trajectory was identified by the censored normal modeling.Five discrete SBP trajectories were identified according to SBP range and the changing pattern over time.Kidney damage was evaluated through eGFR and urinary protein value.A multivariate logistic regression model was used to analyze the influence of different SBP trajectory groups on kidney damage.Results：We identified five discrete SBP trajectories：low-stable group （n =864）,moderate-stable group （n =1980）,moderate increasing group （n =609）,elevated decreasing group,（n =679）,and elevated stable group （n =424）.The detection rate of kidney damage in the low-stable group （SBP：118-124 mmHg） was the lowest among the five groups.The detection rate of each kidney damage index was higher in the elevated stable group （SBP：159-172 mmHg） compared with the low-stable group.For details,the gap was 4.14 （11.6% vs.2.8%） in eGFR 〈60 ml.min-1.1.73 m 2 and 3.66 （17.2% vs.4.7%）,3.38 （25.0% vs.7.4%）,and 1.8 （10.6% vs.5.9%） times in positive urinary protein,eGFR 〈60 ml.min-1.1.73 m 2 and/or positive urinary protein,and eGFR decline ≥30%,respectively （P 〈 0.01）.Conclusion：An elevated stable SBP trajectory is an independent risk factor for kidney damage in the diabetic population.展开更多
Cortical bone is the main mechanical bearing structure of bone,and the mechanical properties of materials are not only related to bone mineral density,but also largely depend on its pores microstructure which affected...Cortical bone is the main mechanical bearing structure of bone,and the mechanical properties of materials are not only related to bone mineral density,but also largely depend on its pores microstructure which affected by blood vessels.However,the change of pores structure in cortical bone under microgravity was still unclear.In this study,in order to clear the changes of pore structure with cortical vascular pores and its effect on bone mechanical properties,rat tail-suspension was used to simulate microgravity and the changes of the microstructure in rat tibia cortices were investigated by high-resolution micro-CT(3μm)while the bone mechanical properties were measured via three point bending test.The results showed the bone mineral density of cortical bone didn't change in tail-suspended rats.However,the pore structure of cortical bone in tail-suspended rats changed significantly,the proportion of pores greater than 15μm(cortical vascular pores)increased while that less than 15μm decreased.The mechanical properties of bone(such as maximum load and maximum stress)in tail-suspended rats deteriorated.And the volume ratio of pore vessels(vessel volume/tissue volume)was negatively correlated with the mechanical properties.In conclusion,the increase of cortical vascular pores in rats caused by the simulated microgravity contributes to the decrease of mechanical properties.展开更多
基金supported by the National Natural Science Foundation of China (31170896)State Key Laboratory of Software Development Environment (SKLSDE-2011ZX-11)
文摘The microgravity environment of a long-term space flight may induce acute changes in an astronaut＇s musculo-skeletal systems. This study explores the effects of simulated microgravity on the mechanical characteristics of articular cartilage. Six rats underwent tail suspension for 14 days and six additional rats were kept under normal earth gravity as controls. Swelling strains were measured using high-frequency ultrasound in all cartilage samples subject to osmotic loading. Site-specific swelling strain data were used in a triphasic theoretical model of cartilage swelling to determine the uniaxial modulus of the cartilage solid matrix. No severe surface irregularities were found in the cartilage samples obtained from the control or tail-suspended groups. For the tail-suspended group, the thickness of the cartilage at a specified site, as determined by ultrasound echo, showed a minor decrease. The uniaxial modulus of articular cartilage at the specified site decreased significantly, from （6.31 ± 3.37） MPa to （5.05 ± 2.98）MPa （p 〈 0.05）. The histology- stained image of a cartilage sample also showed a reduced number of chondrocytes and decreased degree of matrix staining. These results demonstrated that the 14 d simulated microgravity induced significant effects on the mechanical characteristics of articular cartilage. This study is the first attempt to explore the effects of simulated microgravity on the mechanical characteristics of articular cartilage using an osmotic loading method and a triphasic model. The conclusions may provide reference information for manned space flights and a better understanding of the effects of microgravity on the skeletal system.
基金The work was supported by the CAMS Fund of the Nonprofit Central Research Institutes （No. 2016ZX330015）, National Natural Science Foundation of China （No. 11421202） and the 111 Project （No. B13003）.
文摘Two clinical ablation protocols, 2C3L and stepwise, have been routinely used in our group to treat atrial fibrillation （AF）, but with a less than 60% long-term arrhythmia-free outcome achieved in patients. The goal of this study was to examine the underlying mechanism of low success in clinical outcome. MRI images from one patient were used to reconstruct a human atrial anatomical model, and fibrotic tissue was manually added to represent the arrhythmia substrate. AF was induced with standard protocols used in clinical practice. 2C3L and stepwise were then used to test the efficacy of arrhythmia termination in our model. The results showed that re-entries induced in our model could not be terminated by using either 2C3L or the stepwise protocol. Although some of the induced re-entries were terminated, others emerged in new areas. Ablation using only the 2C3L or stepwise method was not sufficient to terminate all re-entries in our model, which may partially explain the poor long-term arrhythmiafree outcomes in clinical practice. Our findings also suggest that computational heart modelling is an important tool to assist in the establishment of optimal ablation strategies.
基金supported by the National Science & Technology Pillar Program of China(2012BAI18B07 and 2012BAI22B02)the National Natural Science Foundation of China(10925208 and 11120101001)the National Key Lab of Virtual Reality Technology
文摘Postoperative tunnel enlargement has been frequently reported after anterior cruciate ligament（ACL）reconstruction.Interference screw,as a surgical implant in ACL reconstruction,may influence natural loading transmission and contribute to tunnel enlargement.The aims of this study are（1）to quantify the alteration of strain energy density（SED）distribution after the anatomic single-bundle ACL reconstruction;and（2）to characterize the influence of screw length and diameter on the degree of the SED alteration.A validated finite element model of human knee joint was used.The screw length ranging from 20 to 30 mm with screw diameter ranging from 7 to 9 mm were investigated.In the post-operative knee,the SED increased steeply at the extra-articular tunnel aperture under compressive and complex loadings,whereas the SED decreased beneath the screw shaft and nearby the intra-articular tunnel aperture.Increasing the screw length could lower the SED deprivation in the proximal part of the bone tunnel;whereas increasing either screw length or diameter could aggravate the SED deprivation in the distal part of the bone tunnel.Decreasing the elastic modulus of the screw could lower the bone SED deprivation around the screw.In consideration of both graft stability and SED alteration,a biodegradable interference screw with a long length is recommended,which could provide a beneficial mechanical environment at the distal part of the tunnel,and meanwhile decrease the bone-graft motion and synovial fluid propagation at the proximal part of the tunnel.These findings together with the clinical and histological factors could help to improve surgical outcome,and serve as a preliminary knowledge for the following study of biodegradable interference screw.
基金supported by the National Natural Science Foundation of China (Grants 11332003, 11421202, 61190123, 31200703, 11472031)Special Fund for Excellent Doctoral Degree Dissertation of Beijing (Grant 20131000601)+1 种基金the 111 Project (Grant B13003)the Innovation Foundation of BUAA for Ph.D. graduates
文摘Carotid artery stenting presents challenges of in-stent restenosis and late thrombosis, which are caused primarily by alterations in the mechanical environment of the artery after stent implantation. The present study constructed patient-specific carotid arterial bifurcation models with lipid pools and calcified components based on magnetic resonance imaging. We numerically analyzed the effects of multicomponent plaques on the distributions of von Mises stresses (VMSs) in the patient-specific models after stenting. The results showed that when a stent was deployed, the large soft lipid pool in atherosclerotic plaques cushioned the host artery and reduced the stress within the arterial wall; however, this resulted in a sharp increase of VMS in the fibrous cap. When compared with the lipid pool, the presence of the calcified components led to slightly increased stresses on the luminal surface. However, when a calcification was located close to the luminal surface of the host artery and the stenosis, the local VMS was elevated. Overall, compared with calcified components, large lipid pools severely damaged the host artery after stenting. Furthermore, damage due to the calcified component may depend on location.
基金National Natural Science Foundation of China(11972068,12002026).
文摘The primary cilium,as a mechanical receptor of osteocytes,participates in the regulation of osteocyte mechanosensitivity.However,how the length of osteocyte primary cilia changes with fluid shear stress(FSS)are unclear,and how the mechanical transmission within osteocytes altered by primary cilia is not well understood yet.Therefore,the ciliary length changes of osteocyte under 15dyn/cm2 of FSS were experimentally detected,and then 3D finite element models of osteocyte primary cilia containing the basal body and axoneme were built.The results showed that(1)The ciliary length of the CON group,FSS 1h,and FSS 6h were 3.71±1.34μm,3.79±1.04μm,and 1.24±0.73μm respectively,indicating the different durations of FSS might lead to the adaptive changes of cilium length.The calculations showed(2)when the ciliary length became shorter with the ciliary angle stayed the same,the deformation and stress of the cell membrane and membrane skeleton was increased.However,the deformation and stress of the cilia membrane,basal body,the rotation angles of basal body were decreased,and those of cytoplasm,cytoskeleton,actin cortex and nucleus were also decreased;(3)With the decrease of the ciliary angle,the deformation and stress of the cilia membrane,basal body,as well as the rotation angles of basal body were increased.Those of the cytoplasm,cytoskeleton,actin cortex,and nucleus were also increased except the cell membrane and membrane skeleton.The calculation results suggested the length and angle of the primary cilia,the deformation and stress of intracellular structures in osteocyte were altered with ciliary basal body,indicated the connection between the basal body and cytoskeleton may be a key factor that affected the mechanical transport in osteocytes across the cell membrane.This finally promoted the adaptive change of ciliary length under FSS.
文摘Temperature-sensitive random copolymerized nanohydrogels were prepared via a one-pot polymerization method using N-isopropylacrylamide(NIPAM)and 2-acrylamido-2-methylpropanesulfonic acid(AMPS)as raw materials.Transmission electron microscopy(TEM)and differential scanning calorimetry(DSC)analyses revealed the partially crystallized porous nanostructure of the gels,which is consistent with the characteristics of porous nanohydrogel materials.The low-molecular-weight polymers exhibited enhancement and sharpening of the end group peaks in Fourier-transform infrared(FTIR),X-ray photoelectron spectroscopy(XPS),and nuclear magnetic resonance hydrogen(^(1)H-NMR)spectra due to the high proportion of small molecules or low-molecular-weight chain segments.In turn,the high-molecular-weight polymers showed pronounced peaks in the main chain segments because of the long-chain effect.Hygroscopicity increased with the molecular weight of the selected polymers,but was inhibited by temperatures below the lower critical solution temperature(LCST).Meanwhile,moisture desorption was faster in low-molecular-weight samples,and the overall moisture desorption rate rose above the LCST value.According to the kinetic analysis,the moisture absorption process conformed to the quasi-primary or quasi-secondary kinetic model,whereas the moisture desorption followed the quasi-secondary model.Moisture cycling experiments showed that the material maintained stable moisture absorption and desorption performance after several cycles,which is essential for long-term cycling.
文摘Background： Sacroiliac （SI） screw fixation is a demanding technique, with a high rate of screw malposition due to the complex pelvic anatomy. TiRobot- is an orthopedic surgery robot which can be used for SI screw fixation. This study aimed to evaluate the accuracy of robot-assisted placement of SI screws compared with a freehand technique. Methods：Thirty patients requiring posterior pelvic ring stabilization were randomized to receive freehand or robot-assisted SI screw fixation, between January 2016 and June 2016 at Beijing Jishuitan Hospital. Forty-five screws were placed at levels S1 and S2. In both methods, the primary end point screw position was assessed and classified using postoperative computed tomography. Fisher＇s exact probability test was used to analyze the screws＇positions. Secondary end points, such as duration of trajectory planning, surgical time after reduction of the pelvis, insertion time for guide wire, number of guide wire attempts, and radiation exposure without pelvic reduction, were also assessed. Results： Twenty-three screws were placed in the robot-assisted group and 22 screws in the freehand group; no postoperative complications or revisions were reported. The excellent and good rate of screw placement was 100% in the robot-assisted group and 95% in the freehand group. The P value （0.009） showed the same superiority in screw distribution. The fluoroscopy time after pelvic reduction in the robot-assisted group was significantly shorter than that in the freehand group （median [Q1, Q3]： 6.0 [6.0, 9.0] s vs. median [Q1, Q3]： 36.0 [21.5, 48.0] s; χ2 = 13.590, respectively, P 〈 0.001）; no difference in operation time after reduction of the pelvis was noted （χ2 = 1.990, P = 0.158）. Time for guide wire insertion was significantly shorter for the robot-assisted group than that for the freehand group （median [Q1, Q3]： 2.0 [2.0, 2.7] min vs. median [Q1, Q3]： 19.0 [15.5, 45.0] min; χ2 = 20.952, respectively, P 〈 0.001）. The number of guide wire attempts in the robot-assisted group was significantly less than that in the freehand group （median [Q1, Q3]： 1.0 [1.0,1.0] time vs. median [Q1, Q3]： 7.0 [1.0, 9.0] times; χ2 = 15.771, respectively, P 〈 0.001）. The instrumented SI levels did not differ between both groups （from S1 to S2, χ2 = 4.760, P = 0.093）. Conclusions： Accuracy of the robot-assisted technique was superior to that of the freehand technique. Robot-assisted navigation is safe for unstable posterior pelvic ring stabilization, especially in S1, but also in S2. SI screw insertion with robot-assisted navigation is clinically feasible.
基金Project supported by the National Natural Science Foundation of China(No.61703023)Beijing Municipal Natural Science Foundation,China(No.3184054)+1 种基金China Scholarship Council(No.201706025021)National Undergraduate Training Programs for Innovation and Entrepreneurship(No.201910006118)。
文摘Lower-limb assisted exoskeletons are widely researched for movement assistance or rehabilitation training.Due to advantages of compliance with human body and lightweight,some cable-driven prototypes have been developed,but most of these can assist only unidirectional movement.In this paper we present an untethered cable-driven ankle exoskeleton that can achieve plantarflexion-dorsiflexion bidirectional motion bilaterally using a pair of single motors.The main weights of the exoskeleton,i.e.,the motors,power supplement units,and control units,were placed close to the proximity of the human body,i.e.,the waist,to reduce the redundant rotation inertia which would apply on the wearer’s leg.A cable force transmission system based on gear-pulley assemblies was designed to transfer the power from the motor to the end-effector effectively.A cable self-tension device on the power output unit was designed to tension the cable during walking.The gait detection system based on a foot pressure sensor and an inertial measurement unit(IMU)could identify the gait cycle and gait states efficiently.To validate the power output performance of the exoskeleton,a torque tracking experiment was conducted.When the subject was wearing the exoskeleton with power on,the muscle activity of the soleus was reduced by 5.2%compared to the state without wearing the exoskeleton.This preliminarily verifies the positive assistance effect of our exoskeleton.The study in this paper demonstrates the promising application of a lightweight cable-driven exoskeleton on human motion augmentation or rehabilitation.
文摘Background：Previous studies have shown that hypertension is an important factor contributing to the occurrence and progression of diabetic kidney damage.However,the relationship between the patterns of blood pressure （BP） trajectory and kidney damage in the diabetic population remains unclear.This prospective study investigated the effect of long-term systolic BP （SBP） trajectory on kidney damage in the diabetic population based on an 8-year follow-up community-based cohort.Methods：This study included 4556 diabetic participants among 101,510 participants.BP,estimated glomerular filtration rate （eGFR）,and urinary protein were measured every 2 years from 2006 to 2014.SBP trajectory was identified by the censored normal modeling.Five discrete SBP trajectories were identified according to SBP range and the changing pattern over time.Kidney damage was evaluated through eGFR and urinary protein value.A multivariate logistic regression model was used to analyze the influence of different SBP trajectory groups on kidney damage.Results：We identified five discrete SBP trajectories：low-stable group （n =864）,moderate-stable group （n =1980）,moderate increasing group （n =609）,elevated decreasing group,（n =679）,and elevated stable group （n =424）.The detection rate of kidney damage in the low-stable group （SBP：118-124 mmHg） was the lowest among the five groups.The detection rate of each kidney damage index was higher in the elevated stable group （SBP：159-172 mmHg） compared with the low-stable group.For details,the gap was 4.14 （11.6% vs.2.8%） in eGFR 〈60 ml.min-1.1.73 m 2 and 3.66 （17.2% vs.4.7%）,3.38 （25.0% vs.7.4%）,and 1.8 （10.6% vs.5.9%） times in positive urinary protein,eGFR 〈60 ml.min-1.1.73 m 2 and/or positive urinary protein,and eGFR decline ≥30%,respectively （P 〈 0.01）.Conclusion：An elevated stable SBP trajectory is an independent risk factor for kidney damage in the diabetic population.
基金the National Natural Science Foundation of China(No.11827803)China Space Station Engineering Experiment Project(No.HYZHXM01016)111 Project(B13003).
文摘Cortical bone is the main mechanical bearing structure of bone,and the mechanical properties of materials are not only related to bone mineral density,but also largely depend on its pores microstructure which affected by blood vessels.However,the change of pores structure in cortical bone under microgravity was still unclear.In this study,in order to clear the changes of pore structure with cortical vascular pores and its effect on bone mechanical properties,rat tail-suspension was used to simulate microgravity and the changes of the microstructure in rat tibia cortices were investigated by high-resolution micro-CT(3μm)while the bone mechanical properties were measured via three point bending test.The results showed the bone mineral density of cortical bone didn't change in tail-suspended rats.However,the pore structure of cortical bone in tail-suspended rats changed significantly,the proportion of pores greater than 15μm(cortical vascular pores)increased while that less than 15μm decreased.The mechanical properties of bone(such as maximum load and maximum stress)in tail-suspended rats deteriorated.And the volume ratio of pore vessels(vessel volume/tissue volume)was negatively correlated with the mechanical properties.In conclusion,the increase of cortical vascular pores in rats caused by the simulated microgravity contributes to the decrease of mechanical properties.
