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Objective To investigate dynamic response of the finite element model of Lenke3 type scoliosis. Methods The finite element model was established based on CT scanning images from a patient with Lenke3 type scoliosis, and validation of the model was also conducted. Modal analysis, harmonic response analysis and transient dynamic analysis were carried out on the model. Results The first order natural frequency of this model was only 1-2 Hz.The amplitude of the finite element model was the largest at the first natural frequency. At the same resonance frequency, the amplitude of the thoracic curved vertebra was larger than that of the lumbar curved vertebra.The amplitude from T6 vertebra to L2 vertebra decreased successively. Conclusions The degree of spinal deformity may affect the perception of spine vibration, and the higher the degree of spinal deformity, the higher the sensitivity to vibration. The first natural frequency is most harmful to Lenke3 type scoliosis patients. Under cyclic loading, the thoracic curved vertebra is more prone to deformation than the lumbar curved vertebra. The closer to T1 segment, the greater the amplitude of the vibration is.
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Objective To investigate the influence from natural and constrained modal of the hip joint on internal fixation after implantation of hollow screws and locking plates for treating femoral neck fractures. Methods CT image data of a patient with femoral neck fracture were analyzed, boundary of the hip joint was extracted to generate a three-dimensional (3D) model of the hip joint, and the assembly of common internal fixation models and hip joint models was established. Finite element simulation was then conducted, with focus on vibration characteristics. Results Vibration had a certain effect on internal fixation stability of hollow screws and locking plates. The occurrence of torsion would destroy the fixation environment of hollow screws and locking plates, resulting in a small displacement at the fracture end. In a constrained state, the modal frequency range was lower. Deformation of the vibration shape mostly occurred at proximal end of the femoral head, leading to the loosening phenomenon of internal fixation and prosthesis. A method for judging the stability of internal fixation was proposed from the perspective of vibration characteristics, and it was found that the stability of internal fixation with hollow screws was better than that of proximal locking plates. Conclusions For choosing internal fixation, influences from natural frequency of the screw and plate should be considered, so as to avoid natural frequency of the femur, which may cause resonance. The results can be used as a guidance for the selection of internal fixation materials and the design of structure and configuration.
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Objective To explore the dynamic characteristics of the thoracolumbar osteoporotic vertebral bodies under free state. Methods Based on CT data from the thoracic and lumbar vertebral body of a healthy female volunteer, model materialization and intervertebral disc tissue reconstruction were realized by using the computerized processing software. The finite element models of normal thoracolumbar vertebral body and thoracolumbar osteoporotic vertebral body were established in ABAQUS 6.14 to perform modal analysis. Results Compared with the normal model, the osteoporosis model had a lower natural frequency and a lager amplitude. As the vibration frequency increased, the model vibration type changed from uniaxial and unidirectional motion to multiaxial and multidirectional motion, and the responsible vertebral body for the maximum amplitude moved down gradually. Conclusions Modal analysis can better analyze dynamic characteristics of the thoracolumbar osteoporotic vertebral body. Patients with osteoporosis should try to avoid the specific vibration environment, so as to decrease the risk of intervertebral disc tissue degeneration, strain of thoracolumbar soft tissues and lesion in posterior structures of the vertebral body.
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The purpose of this study is to reveal the protective effect of rib cage on scoliotic spine by comparing the different effect of rib cage on the stability of normal spine and Lenke1 scoliotic spine. Firstly, according to X-ray computed tomography (CT) image data, four spinal finite element models (SFEMs), including normal spine without rib cage (N1), normal spine with normal rib cage (N2), scoliotic spine without rib cage (S1) and scoliotic spine with deformed rib cage (S2), from the first thoracic vertebrae to the sacral vertebrae (T1～S) were established. Secondly, the natural vibration characteristics of the four SFEMs were obtained by modal analysis. Finally, the maximum vibration amplitudes of the four SFEMs under external excitation were obtained by steady-state analysis. As shown in results, compared with N1, the maximum deformation of N2 segment T4～T6 in the -axis (coronal axis), -axis (sagittal axis) and -axis (vertical axis) directions decreases by 38.44%, 53.80% and 33.72%, respectively. Compared with S1, the maximum deformation of S2 segment T4～T6 in the -axis direction, -axis direction and -axis directions decreases by 44.26%, increases by 32.80% and decreases by 49.23%, respectively. As it can be seen, for normal spine, the rib cage can improve the stability of the whole spine in three directions; for the Lenke1 scoliotic spine, the rib cage can reduce the vibration of the scoliotic spine in the -axis and -axis directions and improves the stability of the whole spine in the two directions, while in the -axis direction, for the serious severe anteversion of scoliotic spine, the deformed rib cage exacerbates the vibration of the scoliotic spine in this direction and destroys the stability of the scoliotic spine in the -axis direction. This study reveals the biomechanical characteristics of rib caged influence on the stability of the scoliotic spine and it has guiding significance for the study of daily protection methods and protective tools for scoliotic patients.
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Humanos , Fenômenos Biomecânicos , Análise de Elementos Finitos , Caixa Torácica , Escoliose , Coluna Vertebral , Vértebras Torácicas , Tomografia Computadorizada por Raios X , VibraçãoRESUMO
In this study, we developed an aluminum-load-cell-based wireless Ringer's solution monitoring and alarm (WRMA) system. The Al load cell was designed with a rectangular shape, and the load was concentrated in the lower beam part of the load cell because of the anisotropic thickness. From the static analysis, we identifi ed the appropriate location for a Wheatstone bridge circuit consisting of four strain gauges. In addition, the modal and harmonic analyses showed that the vibrational frequencies of the hospital environment do not seriously interfere with the output voltage of the Al load cell. However, random vibrations generated by the movement of the WRMA system on various surfaces severely increase the standard deviation of the measured solution weight by ± 10 g or more. Such vibrational error is too large because the average weight of Ringer's solution is 30–40 g at the time of replacing Ringer's solution. Thus, this error could be confusing for nurses and result in mistakes in the timely replacement of the Ringer's solution. However, the standard deviation of the measured weight was dramatically reduced to ± 3 g or less by using the vibration correction algorithm developed in the present study.
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VibraçãoRESUMO
Objective To study the effect of vibration environments on patients with posterior lumbar interbody fusion in daily life. Methods Finite element models of an intact lumbar spine and a postoperative model with fixed L4-5 segments were established. Subsequently, a 40-kg mass point was applied to the upper end plate of the L1 segment to perform a modal analysis. Results In comparison with an intact lumbar spine, the resonance frequency for each order of the whole lumbar spine was reduced after posterior lumbar interbody fusion, and the primary movement of the corresponding modes were also changed. The first two inherent frequencies of the modal in the fusion model were 2.94 Hz and 3.81 Hz, which were close to the vibration frequencies in daily life. In the first three order vibrations, the mode amplitudes of the posterior elements for the L2 and L3 segments increased in the fusion model, which could increase the risk of postoperative degeneration at such locations. In addition, the vibration amplitude of the intervertebral disc of the L3-4 segments clearly increased, particularly at the part of the disc near the L3 vertebral body, which could lead to increased stress and strain and further accelerate its degeneration. Conclusion sBased on the modal analysis of a lumbar spine after posterior lumbar interbody fusion, the investigation of the vibration characteristics of the postoperative lumbar spine will provide some theoretical guidance for the recovery and healthy life of the patients after the corresponding surgery.
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Objective To establish the three-dimensional (3D) finite element (FE) model of thoracolumbosacral T1-S spine based on the computed tomography (CT) images of patients with scoliosis and study its dynamic characteristics. Methods The established scoliotic model was validated by axial compression and shear loading, and the predicted responses were in good agreement with the experimental data. The modal and harmonic analyses were performed using the ABAQUS software, and during the harmonic analysis, the dynamic response of the model was collected at frequencies 5 Hz and 10 Hz. Results From the modal analysis, the first fourth-order modal was extracted. The first- and second-order resonant frequencies of the model were 1.097 Hz and 1.384 Hz, respectively, and the vibration mode was longitudinal bending and lateral bending, respectively. The distribution of the second- and third-order modal resonant frequencies were 5.688 Hz and 28.090 Hz, and the vibration mode was vertical vibration and twisting around the long axis, respectively. The peak amplitude in the harmonic analysis appeared near the modal frequencies, and the average amplitude of vertebral body of the lateral convex segment was larger than that of other segments of the scoliotic spine. Under the vibration frequencies of 5 Hz and 10 Hz, the stress inhomogeneously concentrated on the concave and convex sides of the segments of the vertebral deformity as well as on the intervertebral disc. Conclusions The segments of the spinal deformity in patients with scoliosis were the weak links of their spines and more vulnerable to damage in a vibrating environment. Patients with scoliosis should avoid a vibrating environment, particularly in a sensitive frequency range. The research outcomes provide methodological assistance and mechanical analysis references for the protection, rehabilitation treatment, and clinical pathological studies of patients with scoliosis.
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Dental implant is considered to be the best treatment when dealing with the loss of teeth. It gives beautiful results and can last longer than most of other treatments. Since the Osseo-integration period is a critical period for implant stability, so the used material for dental implant is one of the most factors affecting the stability and Functionally Graded Material (FGM) is one of the opportunities to improve it. The aim of this research is to carry out modal analysis and vibration analysis analytically for functionally graded Dental Implant. In this study several models for dental implant was analyzed by ANSYS15.0 APDL. The functionally graded material was considered in three models. The same materials, Ti-HA, where used in all of them but with different ratio in each. The natural frequency and mode shapes were extracted for all models. The frequency responses of functionally graded Dental Implant after performing a static analysis for each modal have been studied. It was noticed using modal analysis that all of the extracted results for FGM are vary between the two basic materials and it is affected by the concentration of each. It is firmly believed that FGM is the future of dental implant due to the ability of designing a specific material property to be more stable. A comparison of the materials that utilized in FGM when the ration of each 100% was performed as well as an evaluation for the classical dental implant. It is firmly believed that FGM is the future of dental implant due to the ability of designing a specific material property to be more stable.
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To perform modal analysis of CT shelter by applying computer simulation technology so as to pro-vide theoretical guidance for CT shelter structure optimization. Based on CAD model, the finite element model of a CT shelter was established with ANSYS simulation platform. Through modal analysis, different-order modal frequency and modal shape of the shelter were computed and the kinetic characteristics were evaluated. Low order modal frequency was kept away from the natural frequency range of chassis system resonance to avoid the overall structure reso-nance; the 3rd and the 4th modal frequency and engine idle speed frequency were very close so that local resonance might occur; road roughness excitation frequency covered the first 6 order modal frequencies and the further vibration-re-ducing measures of CT equipment were suggested. Based on the theories of finite element method and current software platform, modal analysis of shelter structure can be simulated and the results can provide valuable data for the improvement of kinetic characteristics and structure design.
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Objective To study dynamic characteristics of human lumbar spine using three-dimensional finite element method. Methods Finite element model of lumbar spine (L1~5) was developed and validated based on CT images, and the modal analysis was also conducted. Results A total of top 30-order modal parameters were extracted to obtain dynamic characteristics of the lumbar spine under free boundary conditions. Resonance frequencies of the model were concentrately distributed, but the amplitude of each order varied greatly. Amplitude near L5 segment was much larger, indicating L5 was easily to be injured. This lumbar modal analysis could provide a basis for its further dynamic analysis. Parameters such as natural frequency, modal shape and vibration amplitude of the lumbar spine would be helpful for both lumbar dynamic analysis and optimal design of man-machine interface mechanical equipment.
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La búsqueda constante de medidas para garantizar la calidad y seguridad de la sangre y hemocomponentes constituye una necesidad para el logro de la seguridad transfusional. Aunque las buenas prácticas de producción tienen el objetivo de disminuir los riesgos para obtener productos puros, seguros y eficaces, es necesario complementarlas con herramientas que permitan prevenir los posibles fallos y detectar dichos riesgos. Tal es el caso de la aplicación del Análisis Modal de Fallos y Efectos en el Banco de Sangre Provincial de Villa Clara, donde se identificaron y evaluaron las posibles fallas del proceso de donación de sangre total, lo que permitió caracterizar este proceso, identificar sus variables críticas, proporcionar las bases para proponer nuevos puntos críticos de control y establecer las acciones necesarias para la reducción o eliminación de las fallas detectadas. Esto contribuyó al aumento de la satisfacción de los servicios de transfusión hospitalarios y de los pacientes
The constant search of measures to guarantee the quality and the safe of blood and hemocomponents is a need to achieve the transfusion safe. Although the aim of the good practices of production was to decrease the risks to obtain pure, safe and effective products, it is necessary its fulfillment with tools allowing to prevent the potential failures and to detect such risks. That is the case of the application of the Modal Analysis of Failures and Effects in the Provincial Blood Bank of Villa Clara where the potential failures in the process of total blood donation were identified and assessed, allowing to characterize it, to identify its critical variables, to lay the foundations to propose new critical points of control and to establish the actions necessary to reduce or to eliminate the failures detected. All this contributed to the satisfaction of hospital transfusion services and of patients
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Humanos , Doadores de Sangue , Bancos de Sangue/normas , Controle de QualidadeRESUMO
Objective To study the deformation and stress distribution of femur after total hip arthroplasty (THA) and its influence on the vibration mode and natural frequency of femur. Method Two finite element models of natural femur and femur after THA were developed on the basis of computed tomography (CT) scans from a normal young man to investigate the biomechanical behavior of the subjectunder gait condition and make the modal analysis. Results (1) After THA, obvious stress concentration was obtained around the prosthesis neck, and the stress shielding was observed; (2) The peak stress of femur model after THA increased to 4.36 times of the original one; (3) The natural frequency for constrained mode was much higher than that of free mode; (4) With the increase of vibration mode, the differences in natural frequency between two models became larger; (5) Bending and twisting were the main vibration mode of femur, and there were no significant changes in vibration mode before and after THA. Conclusions The prosthesis could change the mechanical and structural properties of the original femur. In order to avoid prosthesis loosening derived from sympathetic vibration, the vibration property of femur must be taken into consideration in the design of prosthesis.