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Objective:To design a multimodality wheelchair in order to meet many use requirements of the lower limbs dyskinesia patients. Methods:For some shortcomings of the existing multimodality wheelchair such as heavy structure and drive redundancy, the design of multimodality wheelchair based on double parallelogram mechanism is studied, and a simple and reliable multimodality wheelchair mechanism is presented. Rotary actuation drives the double parallelogram mechanism and makes parts of the wheelchair move, and three posture transformations are realized. The coupling movement of the back and leg rest realizes the transformation of sitting and supine posture, and the coupling movement of seat and back realizes the change of sitting and standing posture. The mechanical analysis of wheelchairs based on uniform load was carried out, and the rotation moment is calculated. Results:When the driving torque changed from sitting position to supine position, it increased with the increase of rotation angle and reached a peak value. When the driving torque changed from sitting position to standing position, it gradually decreased with the increase of rotation angle. Then the dynamics simulation is carried out in Adams software, the calculated results were basically consistent with the simulation results. Conclusion:The proposed mechanism is helpful to realize the lightweight design of multimodality wheelchair, and meets the design needs of intelligent multimodality wheelchair.
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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.
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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.
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PURPOSE: The study aimed to identify the accuracy and reproducibility of preparations made by gypsum materials of various colors using quantitative and semi-quantitative three-dimensional (3D) approach. MATERIALS AND METHODS: A titanium maxillary first molar preparation was created as reference dataset (REF). Silicone impressions were duplicated from REF and randomized into 6 groups (n=8). Gypsum preparations were formed and grouped according to the color of gypsum materials, and light-scanned to obtain prepared datasets (PRE). Then, in terms of accuracy, PRE were superimposed on REF using the best-fit-algorithm and PRE underwent intragroup pairwise best-fit alignment for assessing reproducibility. Root mean square deviation (RMSD) and degrees of similarity (DS) were computed and analyzed with SPSS 20.0 statistical software (α=.05). RESULTS: In terms of accuracy, PREs in 3D directions were increased in the 6 color groups (from 19.38 to 20.88 µm), of which the marginal and internal variations ranged 51.36 – 58.26 µm and 18.33 – 20.04 µm, respectively. On the other hand, RMSD value and DS-scores did not show significant differences among groups. Regarding reproducibility, both RMSD and DS-scores showed statistically significant differences among groups, while RMSD values of the 6 color groups were less than 5 µm, of which blue color group was the smallest (3.27 ± 0.24 µm) and white color group was the largest (4.24 ± 0.36 µm). These results were consistent with the DS data. CONCLUSION: The 3D volume of the PREs was predisposed towards an increase during digitalization, which was unaffected by gypsum color. Furthermore, the reproducibility of digitalizing scanning differed negligibly among different gypsum colors, especially in comparison to clinically observed discrepancies.
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Calcium Sulfate , Dataset , Hand , Molar , Silicon , Silicones , Titanium , Tooth Preparation , ToothABSTRACT
Objective To study the cytotoxicity of cervical collar in rehabilitation technical aids and to investigate the cytotoxicity of domestic marketed products. Methods According to the experimental principle of GB/T 16886.5-2003 and GB/T 16175-2008,microscopic observa-tion and Thiazole Blue Colorimetric methods were used to observe the toxicity of extract from four different cer-vical collars on the cells(L929). Results When the concentration of the extract was 0.1 g/ml,the cytotoxicity was grade three and grade two in the cervi-cal collars D and A,respectively;and it was grade one both in cervical collars B and C.When the concentration of the extract was 0.2 g/ml,the cytotoxicity was grade four in cervical collars A and D,and was grade two in cer-vical collars B and C. Conclusion The cervical collars varied in the cytotoxicity,especially in cervical collars A and D.
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BACKGROUND: Currently, regulation of stem cell differentiation by mechanical stresses or microenvironment has become a popular issue in the tissue engineering and regenerative medicine. OBJECTIVE: To review the progress in the effects of mechanical stress on neural differentiation of mesenchymal stem cells in the last decade, providing theoretical basis for stem cell replacement therapy in the treatment of degenerative diseases. METHODS: A search of Web of Science and PubMed database was done to retrieve articles addressing the effects of mechanical stresses on the neural differentiation of mesenchymal stem cells. After systematical analysis and summarization, 104 articles were finally selected and analyzed. RESULTS AND CONCLUSION: Mechanical stimulation and extracellular physical environment factors have important influence on the neural differentiation of mesenchymal stem cells from the bone marrow, adipose tissues, dental pulp and endometrium. PI3K-AKT-mTOR, Wnt/beta-catenin, Rho, MAPK signaling pathways may be involved in the mechanical stresses regulated neural differentiation. However, the clear molecular mechanism needs further studies.
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<p><b>Background</b>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.</p><p><b>Methods</b>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.</p><p><b>Results</b>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·1.73 m 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·1.73 m and/or positive urinary protein, and eGFR decline ≥30%, respectively (P < 0.01).</p><p><b>Conclusion</b>An elevated stable SBP trajectory is an independent risk factor for kidney damage in the diabetic population.</p>
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Female , Humans , Male , Asian People , Blood Pressure , Physiology , Glomerular Filtration Rate , Physiology , Hypertension , Logistic Models , Prospective Studies , Risk FactorsABSTRACT
<p><b>BACKGROUND</b>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.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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).</p><p><b>CONCLUSIONS</b>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.</p>
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Objective To investigate the biomechanical effects of interbody cage height on cervical spine during anterior cervical discectomy and fusion (ACDF) surgery,so as to provide references for selection of interbody cage.Metheds The finite element model of normal cervical spine (C2-7) was built and validated,and the cages with different height (5,6,7,8 mm) were implanted into C5-6 disc (cage 5,6,7,8 model).All the models were loaded with pure moment of 1.5 N · m to produce flexion,extension,lateral bending and axial rotation motions on cervical spine,and the effects of cage height on range of motion (ROM),facet joint stress,intervertebral pressure in cervical spine were investigated.Results The intervertebral angle at the fusion segment increased by 0.68° with per 1 mm-increase in height.The ROM in C5-6 after cage implantation was smaller than 0.44°.The influence of cage height on ROM in C4-5 was greater than that in C6-7,and the changes of ROM in non-fusion segments were smaller than 7.3％.The cage height variation had a smaller impact on the facet joint stress and intervertebral pressure.The stresses in the capsular ligament,cage and screw-plate system increased gradually with the increase of cage height,and the stresses in cage 6,7,8 models were much higher than those in cage 5 model.Conclusions For patients who need implanting fusion cage,the cage height should be 0-1 mm greater than the original intervertebral space height.
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Objective To investigate the biomechanical effects of interbody cage height on cervical spine during anterior cervical discectomy and fusion (ACDF) surgery,so as to provide references for selection of interbody cage.Metheds The finite element model of normal cervical spine (C2-7) was built and validated,and the cages with different height (5,6,7,8 mm) were implanted into C5-6 disc (cage 5,6,7,8 model).All the models were loaded with pure moment of 1.5 N · m to produce flexion,extension,lateral bending and axial rotation motions on cervical spine,and the effects of cage height on range of motion (ROM),facet joint stress,intervertebral pressure in cervical spine were investigated.Results The intervertebral angle at the fusion segment increased by 0.68° with per 1 mm-increase in height.The ROM in C5-6 after cage implantation was smaller than 0.44°.The influence of cage height on ROM in C4-5 was greater than that in C6-7,and the changes of ROM in non-fusion segments were smaller than 7.3％.The cage height variation had a smaller impact on the facet joint stress and intervertebral pressure.The stresses in the capsular ligament,cage and screw-plate system increased gradually with the increase of cage height,and the stresses in cage 6,7,8 models were much higher than those in cage 5 model.Conclusions For patients who need implanting fusion cage,the cage height should be 0-1 mm greater than the original intervertebral space height.
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High flexion squat is extremely common in the daily activities of Asian countries and certain occupations.In this paper,different types of deep squats and their motion characteristics were summarized,and recent research progress of squat biomechanics was reviewed.Different research methods on squats such as in vitro experiment,in vivo test and computer simulation were also classified and represented.Biomechanical studies on deep squat of the knee can benefit establishment of reasonable rehabilitation training,prevention of sports risks as well as provide some references for optimization of knee prosthesis design.
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Objective To investigate the effect of different calcification patterns on the outcome of transcatheter aortic valve implantation (TAVI) by the finite element method.Methods Three calcified human aortic root models (coaptation line calcification model,attachment line calcification model and circular calcification model) were developed according to the location of calcified plaques on the aortic valve leaflets.The processes of self-expanding transcatheter aortic valve implanted into the 3 calcified models were simulated by ABAQUS software.The effects of different calcification patterns on the aortic root stresses,valve frame distortions and paravalvular gaps were analyzed.Results Circular calcification model had the largest maximum principal stress on calcified plaques (18.42 MPa),which might result in a higher risk of stroke after implantation;the circular calcification model also had the greatest distortion of the valve frame,which might lead to worse prosthetic durability;the paravalvular gaps area of the attachment line calcification model was 37.2 mm2,which was more than twice that of the other 2 models,causing more serious paravalvular regurgitation.Cenclusiens Different aortic valve calcification patterns are related to aortic root stresses,valve frame distortions and paravalvular gaps after TAVI,which will have an impact on postoperative complications and prothesis durability.The research findings provide references for the prediction of clinical outcome after TAVI.
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Objective To study the effect of stair ascent on insert wear of total knee replacement (TKA) by finite element model, which is of great theoretical and practical significance for improvement of wear evaluation method and guidance of design of artificial knee joint prosthesis. Method A finite element analysis model of TKR wear based on Archard’s law was established and validated. The model was applied with loads under normal level walking (ISO14243) and stair ascent, respectively, to compare and analyze the influence of stair ascent on TKR wear. Results The predicted wear during level walking was consistent with experimental results reported in the literature. The volumetric wear rate during stair ascent was 37.10 mm3 per million cycles (MC), which was significantly higher than that during level walking (16.94 mm3/MC). The linear wear during stair ascent was significantly higher than that during level walking as well. Wear during stair ascent was mainly distributed in the backward area of medial platform, which was obviously different from that during level walking. Conclusions As a common daily activity with high loads and high flexion angles, stair ascent contributes an important part in TKR wear, and more attention should be paid to the testing and evaluation of TKR wear.
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High flexion squat is extremely common in the daily activities of Asian countries and certain occupations. In this paper, different types of deep squats and their motion characteristics were summarized, and recent research progress of squat biomechanics was reviewed. Different research methods on squats such as in vitro experiment, in vivo test and computer simulation were also classified and represented. Biomechanical studies on deep squat of the knee can benefit establishment of reasonable rehabilitation training, prevention of sports risks as well as provide some references for optimization of knee prosthesis design.
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Objective To investigate the effect of different calcification patterns on the outcome of transcatheter aortic valve implantation (TAVI) by the finite element method. Methods Three calcified human aortic root models (coaptation line calcification model, attachment line calcification model and circular calcification model) were developed according to the location of calcified plaques on the aortic valve leaflets. The processes of self-expanding transcatheter aortic valve implanted into the 3 calcified models were simulated by ABAQUS software. The effects of different calcification patterns on the aortic root stresses, valve frame distortions and paravalvular gaps were analyzed. Results Circular calcification model had the largest maximum principal stress on calcified plaques (18.42 MPa), which might result in a higher risk of stroke after implantation; the circular calcification model also had the greatest distortion of the valve frame, which might lead to worse prosthetic durability; the paravalvular gaps area of the attachment line calcification model was 37.2 mm2, which was more than twice that of the other 2 models, causing more serious paravalvular regurgitation. Conclusions Different aortic valve calcification patterns are related to aortic root stresses, valve frame distortions and paravalvular gaps after TAVI, which will have an impact on postoperative complications and prothesis durability. The research findings provide references for the prediction of clinical outcome after TAVI.
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Objective To investigate the biomechanical effects of interbody cage height on cervical spine during anterior cervical discectomy and fusion (ACDF) surgery, so as to provide references for selection of interbody cage. Methods The finite element model of normal cervical spine (C2-7) was built and validated, and the cages with different height (5, 6, 7, 8 mm) were implanted into C5-6 disc (cage5, 6, 7, 8 model). All the models were loaded with pure moment of 1.5 N•m to produce flexion, extension, blending and axial torsion motions on the cervical spine, and the effects of cage height on range of motion (ROM), facet joint stress, intervertebral pressure in cervical spine were investigated. Results The intervertebral angle at the fusion segment increased by 0.68°with per 1 mm-increase of height. The ROM at C5-6 after cage implantation was less than 0.44°. The influence of cage height on ROM in C4-5 was greater than that in C6-7, and the changes of ROM in non-fusion segments were less than 7.3%. The cage height variation had a smaller impact on the facet joint stress and intervertebral pressure. The stresses in the capsular ligament, cage and screw-plate system increased gradually with the increase of cage height, and these stresses in the cage6, 7, 8 models were much higher than those in the cage5 model. Conclusions For patients who need implanting fusion cage, the cage height should be 0-1 mm greater than the original intervertebral space height.
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Objective To investigate the effects of inflation pressures on mechanical environment of pathological carotid after stent implantation. Methods The carotid artery models with lipid and calcified plaques were constructed based on high-resolution MRI images. The artery-stent interaction model was developed in the finite element software. Based on the models, the von Mises stress distributions on the vascular wall and plague under 3 different inflation pressures (909, 1212 and 1515 kPa) were simulated. Results High inflation pressure would induce large Von Mises stress on the artery-stent interface. Moreover, the stress on the lipid plaque increased significantly with the increase of inflation pressure. However, the differences in stress distributions on the calcified plaque were very small under different inflation pressure. Conclusions Higher inflation pressure may severely damage the lipid plaque and artery-stent interface after stenting, which will contribute to the failure of stent. This research finding may provide clinical guidance for the selection of inflation pressure for arterial stent deployment and the assessment of plague stability after stent implantation．
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Objective To simulate leg length discrepancy by unilateral increase in lower limb of normal person, analyze gait features in the case of leg length discrepancy and its effect on walking gait, so as to provide theoretical proofs for chronical musculoskeletal diseases in lower limb amputees due to leg length discrepency. Methods Leg length discrepancy was simulated by subjects wearing shoes to increase the unilateral height of one leg. The time-space parameters, ground reaction forces and joint angles of the subjects during normal walking gait and leg length discrepancy gait were obtained via the 3D motion capture system and the reaction force platform to make comparative analysis. Results Significant differences were found between leg length discrepancy gait and normal gait in terms of step length, stride time and single supporting period. In the case of leg length discrepancy gait, the ground reaction force of both feet significantly increased at heel-strike phase compared with normal gait, and obvious changes were observed in angles of hip, knee and ankle joints. Conclusions Leg length discrepancy is an important cause leading to gait abnormalities, and maybe a cause of leg joint diseases for trans-tibial amputees wearing prosthesis.
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Objective To study the effect from different structures and material hardness of orthopedic insoles on flatfoot correction. Methods The contours of flatfoot under weight-bearing and non-weight-bearing conditions were scanned by Infoot system. The 3 kinds of medial longitudinal arch height (typeⅠ, Ⅱ, Ⅲ) and 3 kinds of material hardness (30°, 35°, 42°) from orthopedic insoles were used to compare their effects on flatfoot by the embedded insole test system. Results TypeⅠorthopedic insoles could significantly restore the anatomical position by improving the height of navicular bone, and redistribute the concentrated plantar pressure and increase the loading area of medial longitudinal arch with material hardness of 35°. Conclusions The appropriate insole shows a favorable orthopedic effect to ameliorate the foot deformity of flatfoot patients. The research findings lay a theoretical basis on design of the personalized orthopedic insoles.
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Objective To study the method of lower limb movement pattern recognition using the electromyographic (EMG) signals of the residual thigh muscles, and explore the possibility of lower limb prosthesis control based on the EMG signals. Methods Fifteen transfemoral amputees were selected as subjects, and the subjects were required to complete 5 kinds of motion, including level walking, stair ascent, stair descent, standing up and sitting down. The surface EMG signals from 6 muscles of the thigh stump were collected from each subject, including rectus femoris, vastus lateralis, tensor fascia lata, biceps femoris, semitendinosus and gluteus maximus. Six kinds of time-domain and frequency domain features of the EMG signals were extracted, and 5 kinds of motion patterns were recognized by the support vector machine. Results Five kinds of motion patterns could be recognized online by EMG signals of the residual thigh muscles. By single experimental data from one subject, the recognition rate was 94%; for the same subject, by the data mixed from two experiments, the recognition rate was 85%; for different subjects, the recognition rate was 74%. By feature optimization, using only two EMG features of 3 muscles, the recognition rate could reach 92% by single experimental data from one subject. For 3 kinds of motion patterns (level walking, stair ascent, stair descent), the recognition rate respectively was 100% using single experimental data from one subject, 98.33% using the data mixed from two experiments for the same subject, and 93.33% using the data from different subjects. Conclusions Simply using the thigh stump EMG signals to recognize movement intention is proved to be feasible. For each patient, by several times of training before using the EMG signals, the recognition rate is expected to reach an ideal state. The present work will lay a foundation for lower limb prosthesis control based on the EMG signals.