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1.
Med Biol Eng Comput ; 59(7-8): 1447-1459, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34156602

RESUMO

Surface electromyography (sEMG) has been widely used in evaluating muscle fatigue among athletes where electrodes are attached on the skin during the activity. Recently, infrared thermography technique (IRT) has gain popularity and shown to be another preferred method in monitoring and predicting muscle fatigue non-obstructively. This paper investigates the correlation between surface temperature and muscle activation parameters obtained using both IRT and sEMG methods simultaneously. Twenty healthy subjects were required to perform a repetitive calf raise exercise with various loads attached around their ankle for 3 min to induce fatigue on the targeted gastrocnemius muscles. Average temperature and temperature difference information were extracted from thermal images, while root mean square (RMS) and median frequency (MF) were extracted from sEMG signals. Spearman statistical analysis performed shows that there is a significant correlation between average temperature with RMS and between temperature difference with MF values at p<0.05. While ANOVA test conducted shows that there is significant impact of loads on RMS and MF where F=12.61 and 3.59, respectively, at p< 0.05. This study suggested that skin surface temperature can be utilized in monitoring and predicting muscle fatigue in low intensity dynamic exercise and can be extended to other dynamic exercises.


Assuntos
Fadiga Muscular , Termografia , Eletromiografia , Exercício Físico , Humanos , Músculo Esquelético
2.
Int J Biol Macromol ; 181: 82-98, 2021 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-33771547

RESUMO

Vitamin D deficiency is now a global health problem; despite several drug delivery systems for carrying vitamin D due to low bioavailability and loss bioactivity. Developing a new drug delivery system to deliver vitamin D3 is a strong incentive in the current study. Hence, an implantable drug delivery system (IDDS) was developed from the electrospun cellulose acetate (CA) and ε-polycaprolactone (PCL) nanofibrous membrane, in which the core of implants consists of vitamin D3-loaded CA nanofiber (CAVD) and enclosed in a thin layer of the PCL membrane (CAVD/PCL). CA nanofibrous mat loaded with vitamin D3 at the concentrations of 6, 12, and 20% (w/w) of vitamin D3 were produced using electrospinning. The smooth and bead-free fibers with diameters ranged from 324 to 428 nm were obtained. The fiber diameters increased with an increase in vitamin D3 content. The controlled drug release profile was observed over 30-days, which fit with the zero-order model (R2 > 0.96) in the first stage. The mechanical properties of IDDS were improved. Young's modulus and tensile strength of CAVD/PCL (dry) were161 ± 14 and 13.07 ± 2.5 MPa, respectively. CA and PCL nanofibers are non-cytotoxic based on the results of the in-vitro cytotoxicity studies. This study can further broaden in-vivo study and provide a reference for developing a new IDDS to carry vitamin D3 in the future.


Assuntos
Celulose/análogos & derivados , Colecalciferol/farmacologia , Liberação Controlada de Fármacos , Nanofibras/química , Poliésteres/química , Varredura Diferencial de Calorimetria , Morte Celular/efeitos dos fármacos , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Celulose/química , Condutividade Elétrica , Humanos , Nanofibras/ultraestrutura , Temperatura , Viscosidade , Água/química
3.
Int J Biol Macromol ; 151: 584-594, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32081758

RESUMO

Arabinoxylan (AX) is a natural biological macromolecule with several potential biomedical applications. In this research, AX, nano-hydroxyapatite (n-HAp) and titanium dioxide (TiO2) based polymeric nanocomposite scaffolds were fabricated by the freeze-drying method. The physicochemical characterizations of these polymeric nanocomposite scaffolds were performed for surface morphology, porosity, swelling, biodegradability, mechanical, and biological properties. The scaffolds exhibited good porosity and rough surface morphology, which were efficiently controlled by TiO2 concentrations. MC3T3-E1 cells were employed to conduct the biocompatibility of these scaffolds. Scaffolds showed unique biocompatibility in vitro and was favorable for cell attachment and growth. PNS3 proved more biocompatible, showed interconnected porosity and substantial mechanical strength compared to PNS1, PNS2 and PNS4. Furthermore, it has also showed more affinity to cells and cell growth. The results illustrated that the bioactive nanocomposite scaffold has the potential to find applications in the tissue engineering field.


Assuntos
Materiais Biocompatíveis/química , Osso e Ossos , Durapatita/química , Nanocompostos/química , Engenharia Tecidual , Alicerces Teciduais/química , Titânio/química , Xilanos/química , Animais , Biopolímeros/química , Linhagem Celular , Sobrevivência Celular , Camundongos , Estrutura Molecular , Nanocompostos/ultraestrutura , Porosidade , Análise Espectral , Estresse Mecânico
4.
Comput Methods Biomech Biomed Engin ; 23(5): 182-190, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31910663

RESUMO

Glenoid perforation is not the intended consequence of the surgery and must be avoided. The analysis on biomechanical aspect of glenoid vault perforation remains unknown. The purpose of this study is to determine the impact of glenoid perforation towards stress distribution and micromotion at the interfaces. Eight glenoid implant models had been constructed with various size, number and type of fixation. A load of 750 N was applied to centre, superior-anterior and superior-posterior area. Implant perforation had minimal impact on stress distribution and micromotion at the interfaces. However, cement survival rate for implant without perforation was the highest with a difference of up to 37% compared to other perforated models. Besides that, implant fixation and high stresses at the implant had more of an impact on implant instability than implant perforation. As a conclusion, glenoid perforation did not influence the stress distribution and micromotion, but, it reduced cement survival rate and increase the stress critical volume.


Assuntos
Artroplastia do Ombro , Simulação por Computador , Prótese Articular , Movimento (Física) , Articulação do Ombro/cirurgia , Perfuração Espontânea/cirurgia , Estresse Mecânico , Fenômenos Biomecânicos , Análise de Elementos Finitos , Humanos , Probabilidade , Desenho de Prótese
5.
J Mech Behav Biomed Mater ; 91: 406-415, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30684888

RESUMO

Intact glenoid labrum is one of passive stabilizer for glenohumeral joint, which have various stiffness at different region. The aim of this study is to develop new artificial glenoid labrum from Polyvinyl Alcohol (PVA) hydrogel, which known as good biomaterial due to its biocompatibility and ability to tailor its modulus. PVA hydrogel was formed using freeze-thaw (FT) method and the stiffness of PVA was controlled by manipulating the concentration of PVA and number of FT cycles. Then, the gradual stiffness was formed using simple diffusion method by introducing the pre-freeze-and-thaw steps. The results showed 20% PVA with three FT cycles suit to highest stiffness of glenoid labrum while 10% PVA with three FT cycles suit to lowest stiffness of glenoid labrum. The functionally graded PVA hydrogel was then developed using the same method by diffusing two mixture (20% PVA and 10% PVA). Mechanical compression test showed, the highest modulus (0.41 MPa) found at the 20% PVA region and lowest modulus (0.1 MPa) found at 10% PVA region. While, at intermediate region, the compressive modulus was in between 20% and 10%, 0.2 MPa. The existence of gradual stiffness was further prove by checking crystallinity of material at each region using Differential Scanning Calorimetry (DSC) and Wide Angle X-ray Diffraction (WAXD). Microstructure of material was obtained from Scanning Electron Microscopy (SEM). This functionally graded PVA hydrogel also able to reduce about 51% of stress at glenoid implant and up to 17% for micromotion at the interfaces. Existence of artificial glenoid labrum could minimize the occurrence of glenoid component loosening.


Assuntos
Materiais Biomiméticos , Congelamento , Álcool de Polivinil , Articulação do Ombro , Força Compressiva , Teste de Materiais
6.
Med Biol Eng Comput ; 56(10): 1925-1938, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29679256

RESUMO

Pilon fractures can be caused by high-energy vertical forces which may result in long-term patient immobilization. Many experts in orthopedic surgery recommend the use of a Delta external fixator for type III Pilon fracture treatment. This device can promote immediate healing of fractured bone, minimizing the rate of complications as well as allowing early mobilization. The characteristics of different types of the Delta frame have not been demonstrated yet. By using the finite element method, this study was conducted to determine the biomechanical characteristics of six different configurations (Model 1 until Model 6). CT images from the lower limb of a healthy human were used to reconstruct three-dimensional models of foot and ankle bones. All bones were assigned with isotropic material properties and the cartilages were assigned to exhibit hyperelasticity. A linear link was used to simulate 37 ligaments at the ankle joint. Axial loads of 70 and 350 N were applied at the proximal tibia to simulate the stance and swing phase. The metatarsals and calcaneus were fixed distally in order to prevent rigid body motion. A synthetic ankle bone was used to validate the finite element model. The simulated results showed that Delta3 produced the highest relative micromovement (0.09 mm, 7 µm) during the stance and swing phase, respectively. The highest equivalent von Mises stress was found at the calcaneus pin of the Delta4 (423.2 MPa) as compared to others. In conclusion, Delta1 external fixator was the most favorable option for type III Pilon fracture treatment. Graphical abstract ᅟ.


Assuntos
Fixadores Externos , Análise de Elementos Finitos , Fraturas da Tíbia/fisiopatologia , Fraturas da Tíbia/cirurgia , Fenômenos Biomecânicos , Calcâneo/fisiopatologia , Humanos , Ligamentos/fisiopatologia , Movimento , Reprodutibilidade dos Testes , Estresse Mecânico , Tíbia/fisiopatologia , Tíbia/cirurgia
7.
J Healthc Eng ; 2017: 9618940, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29065672

RESUMO

The present study was conducted to examine the effects of body weight on intradiscal pressure (IDP) and annulus stress of intervertebral discs at lumbar spine. Three-dimensional finite element model of osseoligamentous lumbar spine was developed subjected to follower load of 500 N, 800 N, and 1200 N which represent the loads for individuals who are normal and overweight with the pure moments at 7.5 Nm in flexion and extension motions. It was observed that the maximum IDP was 1.26 MPa at L1-L2 vertebral segment. However, the highest increment of IDP was found at L4-L5 segment where the IDP was increased to 30% in flexion and it was more severe at extension motion reaching to 80%. Furthermore, the maximum annulus stress also occurred at the L1-L2 segment with 3.9 MPa in extension motion. However, the highest increment was also found at L4-L5 where the annulus stress increased to 17% in extension motion. Based on these results, the increase of physiological loading could be an important factor to the increment of intradiscal pressure and annulus fibrosis stress at all intervertebral discs at the lumbar spine which may lead to early intervertebral disc damage.


Assuntos
Análise de Elementos Finitos , Disco Intervertebral/fisiologia , Vértebras Lombares/fisiologia , Suporte de Carga/fisiologia , Fenômenos Biomecânicos/fisiologia , Humanos , Disco Intervertebral/diagnóstico por imagem , Vértebras Lombares/diagnóstico por imagem , Masculino , Fusão Vertebral , Tomografia Computadorizada por Raios X , Adulto Jovem
8.
Med Biol Eng Comput ; 55(3): 439-447, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-27255451

RESUMO

The present study was conducted to compare the stability of four commercially available implants by investigating the focal stress distributions and relative micromotion using finite element analysis. Variations in the numbers of pegs between the implant designs were tested. A load of 750 N was applied at three different glenoid positions (SA: superior-anterior; SP: superior-posterior; C: central) to mimic off-center and central loadings during activities of daily living. Focal stress distributions and relative micromotion were measured using Marc Mentat software. The results demonstrated that by increasing the number of pegs from two to five, the total focal stress volumes exceeding 5 MPa, reflecting the stress critical volume (SCV) as the threshold for occurrence of cement microfractures, decreased from 8.41 to 5.21 % in the SA position and from 9.59 to 6.69 % in the SP position. However, in the C position, this change in peg number increased the SCV from 1.37 to 5.86 %. Meanwhile, micromotion appeared to remain within 19-25 µm irrespective of the number of pegs used. In conclusion, four-peg glenoid implants provide the best configuration because they had lower SCV values compared with lesser-peg implants, preserved more bone stock, and reduced PMMA cement usage compared with five-peg implants.


Assuntos
Análise de Elementos Finitos , Cavidade Glenoide/fisiologia , Prótese Articular , Desenho de Prótese , Amplitude de Movimento Articular/fisiologia , Estresse Mecânico , Cimentos Ósseos/farmacologia , Cavidade Glenoide/efeitos dos fármacos , Amplitude de Movimento Articular/efeitos dos fármacos , Suporte de Carga
9.
Bioprocess Biosyst Eng ; 40(2): 191-200, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27757535

RESUMO

In this study, laccase was immobilized on nylon 6,6/Fe3+ composite (NFC) nanofibrous membrane and used for the detoxification of 3,3'-dimethoxybenzidine (DMOB). The average size and tensile strength of the NFC membrane were found to be 60-80 nm (diameter) and 2.70 MPa, respectively. The FTIR results confirm that the amine (N-H) group of laccase was attached with Fe3+ particles and the carbonyl (C=O) group of NFC membrane via hydrogen bonding. The half-life of the laccase-NFC membrane storage stability was increased from 6 to 11 weeks and the reusability was significantly extended up to 43 cycles against ABTS oxidation. Enhanced electro-oxidation of DMOB by laccase was observed at 0.33 V and the catalytic current was found to be 30 µA. The DMOB-treated mouse fibroblast 3T3-L1 preadipocytes showed maximum (97 %) cell inhibition at 75 µM L-1 within 24 h. The cytotoxicity of DMOB was significantly decreased to 78 % after laccase treatment. This study suggests that laccase-NFC membrane might be a good candidate for emerging pollutant detoxification.


Assuntos
Caprolactama/análogos & derivados , Dianisidina , Compostos Férricos/química , Proteínas Fúngicas/química , Lacase/química , Membranas Artificiais , Nanofibras/química , Polímeros/química , Trametes/enzimologia , Células 3T3-L1 , Animais , Caprolactama/química , Dianisidina/química , Dianisidina/toxicidade , Enzimas Imobilizadas/química , Camundongos
10.
J Mech Behav Biomed Mater ; 54: 21-32, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26410762

RESUMO

The present study reports the effects of combined torsional and compressive cyclic loading on trabecular bone in order to mimic true physiological conditions and thereby provides improved data that represents clinical and real life conditions. However, only compressive behaviour is evaluated in most previous studies of bone mechanics. From the monotonic evaluation, it is observed that lower stress is needed for the onset of microcrack in the sample under torsional loading, compared to the stress needed in compression. Trabecular bone samples were subjected to a combination of torsion and compression fatigue at different stress levels during which they were compared to compressive axial fatigue. The stress levels were determined by considering the monotonic strength at 25-50% for both compressive and shear stresses. Significant decrease in fatigue lifetime is observed in between samples of pure compression fatigue and those with superpositioned torsional loading (p<0.05). The reduction in fatigue lifetime became more evident at a high torsional stress level. In this case, the failure of the sample is said to be 'torsional dominant'. Fatigue behaviour of bovine trabecular bone begins with plastic deformation, followed by strain accumulation and modulus reduction. As the strain rate increases, more energy dissipates and the sample finally failed. Further, the analysis of fractograph revealed something on the trabeculae by bending in sample with superpositioned torsional loading. In conclusion, torsional loading decreases the quality of the trabecular properties in terms of stiffness, life and structural integrity. It is hoped that results from this study will improve the understanding of the behaviour of trabecular bone under combined fatigue and help to develop future assessments of trabecular failure.


Assuntos
Força Compressiva , Fêmur/fisiologia , Estresse Mecânico , Animais , Fenômenos Biomecânicos , Bovinos , Humanos , Teste de Materiais , Suporte de Carga
11.
Sci Rep ; 5: 11194, 2015 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-26057073

RESUMO

Iron and its alloy have been proposed as biodegradable metals for temporary medical implants. However, the formation of iron oxide and iron phosphate on their surface slows down their degradation kinetics in both in vitro and in vivo scenarios. This work presents new approach to tailor degradation behavior of iron by incorporating biodegradable polymers into the metal. Porous pure iron (PPI) was vacuum infiltrated by poly(lactic-co-glycolic acid) (PLGA) to form fully dense PLGA-infiltrated porous iron (PIPI) and dip coated into the PLGA to form partially dense PLGA-coated porous iron (PCPI). Results showed that compressive strength and toughness of the PIPI and PCPI were higher compared to PPI. A strong interfacial interaction was developed between the PLGA layer and the iron surface. Degradation rate of PIPI and PCPI was higher than that of PPI due to the effect of PLGA hydrolysis. The fast degradation of PIPI did not affect the viability of human fibroblast cells. Finally, this work discusses a degradation mechanism for PIPI and the effect of PLGA incorporation in accelerating the degradation of iron.


Assuntos
Ferro/química , Ácido Láctico/química , Ácido Poliglicólico/química , Próteses e Implantes , Cinética , Microscopia Eletrônica de Varredura , Copolímero de Ácido Poliláctico e Ácido Poliglicólico , Porosidade , Espectrofotometria Infravermelho
12.
Med Eng Phys ; 36(10): 1358-66, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25092623

RESUMO

Subtalar dislocation is a rare injury caused by high-energy trauma. Current treatment strategies include leg casts, internal fixation and external fixation. Among these, external fixators are the most commonly used as this method is believed to provide better stabilization. However, the biomechanical stability provided by these fixators has not been demonstrated. This biomechanical study compares two commonly used external fixators, i.e. Mitkovic and Delta. CT imaging data were used to reconstruct three-dimensional models of the tibia, fibula, talus, calcaneus, navicular, cuboid, three cuneiforms and five metatarsal bones. The 3D models of the bones and cartilages were then converted into four-noded linear tetrahedral elements, whilst the ligaments were modelled with linear spring elements. Bones and cartilage were idealized as homogeneous, isotropic and linear. To simulate loading during walking, axial loading (70 N during the swing and 350 N during the stance phase) was applied at the end of diaphyseal tibia. The results demonstrate that the Mitkovic fixator produced greater displacement (peak 3.0mm and 15.6mm) compared to the Delta fixator (peak 0.8mm and 3.9 mm), in both the swing and stance phase, respectively. This study demonstrates that the Delta external fixator provides superior stability over the Mitkovic fixator. The Delta fixator may be more effective in treating subtalar dislocation.


Assuntos
Fixadores Externos , Análise de Elementos Finitos , Articulações do Pé/lesões , Luxações Articulares/cirurgia , Fenômenos Mecânicos , Fenômenos Biomecânicos , Articulações do Pé/diagnóstico por imagem , Articulações do Pé/fisiopatologia , Articulações do Pé/cirurgia , Humanos , Luxações Articulares/diagnóstico por imagem , Luxações Articulares/fisiopatologia , Estresse Mecânico , Tomografia Computadorizada por Raios X , Suporte de Carga
13.
Med Eng Phys ; 36(10): 1322-30, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25127377

RESUMO

Pilon fractures are commonly caused by high energy trauma and can result in long-term immobilization of patients. The use of an external fixator i.e. the (1) Delta, (2) Mitkovic or (3) Unilateral frame for treating type III pilon fractures is generally recommended by many experts owing to the stability provided by these constructs. This allows this type of fracture to heal quickly whilst permitting early mobilization. However, the stability of one fixator over the other has not been previously demonstrated. This study was conducted to determine the biomechanical stability of these external fixators in type III pilon fractures using finite element modelling. Three-dimensional models of the tibia, fibula, talus, calcaneus, navicular, cuboid, three cuneiforms and five metatarsal bones were reconstructed from previously obtained CT datasets. Bones were assigned with isotropic material properties, while the cartilage was assigned as hyperelastic springs with Mooney-Rivlin properties. Axial loads of 350 N and 70 N were applied at the tibia to simulate the stance and the swing phase of a gait cycle. To prevent rigid body motion, the calcaneus and metatarsals were fixed distally in all degrees of freedom. The results indicate that the model with the Delta frame produced the lowest relative micromovement (0.03 mm) compared to the Mitkovic (0.05 mm) and Unilateral (0.42 mm) fixators during the stance phase. The highest stress concentrations were found at the pin of the Unilateral external fixator (509.2 MPa) compared to the Mitkovic (286.0 MPa) and the Delta (266.7 MPa) frames. In conclusion, the Delta external fixator was found to be the most stable external fixator for treating type III pilon fractures.


Assuntos
Fixadores Externos , Análise de Elementos Finitos , Fenômenos Mecânicos , Fraturas da Tíbia/cirurgia , Fenômenos Biomecânicos , Humanos , Funções Verossimilhança , Movimento , Estresse Mecânico , Tíbia/diagnóstico por imagem , Tíbia/fisiologia , Tíbia/cirurgia , Fraturas da Tíbia/diagnóstico por imagem , Fraturas da Tíbia/fisiopatologia , Tomografia Computadorizada por Raios X
14.
Bioorg Med Chem Lett ; 23(24): 6616-9, 2013 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-24215893

RESUMO

In this study aliphatic polyacids were synthesized using palm acid oil (PAO) and sunflower oil (SFO) via addition reaction technique. The synthesized materials were characterized using Fourier-transform infra-red (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS) and thermo-gravimetric analysis (TGA). Mixing formic acid and hydrogen peroxide with PAO or SFO at the ratio 3:10:1 produced the lowest iodine value of 10.57 and 9.24 respectively, indicating the increase in epoxidization of both oils. Adding adipic acid to the epoxidized oils at a ratio of 1:10 increases the acid values of SFO and PAO to 11.22 and 6.73 respectively. The existence of multi-acid groups present in synthesized polyacid was confirmed by MALD-ToF-MS. This feature indicates a possible value to the biomaterials development.


Assuntos
Ácidos/química , Ácidos/síntese química , Óleos de Plantas/química , Compostos de Epóxi/química , Ácidos Graxos Insaturados/química , Formiatos/química , Peróxido de Hidrogênio/química , Óleo de Palmeira , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Espectroscopia de Infravermelho com Transformada de Fourier , Óleo de Girassol
15.
Int J Oral Maxillofac Implants ; 28(3): e151-60, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23748334

RESUMO

PURPOSE: To compare the extramaxillary approach with the widely used intrasinus approach via finite element method. MATERIALS AND METHODS: A unilateral three-dimensional model of the craniofacial area surrounding the region of interest was developed using computed tomography image datasets. The zygomatic implants were modeled using three-dimensional computer-aided design software and virtually placed according to the described techniques together with one conventional implant and a prosthesis. The bone was assumed to be linear isotropic with a stiffness of 13.4 GPa, while the implants were of titanium alloy with a stiffness of 110 GPa. Masseter forces were applied at the zygomatic arch, and occlusal loads were applied to the surface of the prosthesis. The stresses and displacements generated on the surrounding bone and within the implant due to the simulated loading configuration were analyzed. RESULTS: The bone-implant interface and zygomatic implant body for the intrasinus approach produced 1.41- and 4.27-fold higher stress, respectively, compared with the extramaxillary approach under vertical loading. However, under lateral loading, the extramaxillary approach generated 2.48-fold higher stress than the intrasinus at the bone-implant interface. The zygomatic implant in the extramaxillary approach had twofold higher micromotion than those with intrasinus approach under lateral loading. CONCLUSIONS: No one technique was found to be superior; however, if lateral loading is used, the intrasinus approach is the most favorable for the rehabilitation of severely atrophic maxillae.


Assuntos
Planejamento de Prótese Dentária/métodos , Prótese Dentária Fixada por Implante/métodos , Análise do Estresse Dentário/métodos , Análise de Elementos Finitos , Maxila/patologia , Modelos Dentários , Zigoma , Atrofia , Força de Mordida , Desenho Assistido por Computador , Ligas Dentárias , Implantes Dentários , Humanos , Músculo Masseter , Seio Maxilar , Titânio
16.
J Orthop Res ; 31(9): 1447-54, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23640802

RESUMO

Posterior instrumentation is a common fixation method used to treat thoracolumbar burst fractures. However, the role of different cross-link configurations in improving fixation stability in these fractures has not been established. A 3D finite element model of T11-L3 was used to investigate the biomechanical behavior of short (2 level) and long (4 level) segmental spine pedicle screw fixation with various cross-links to treat a hypothetical L1 vertebra burst fracture. Three types of cross-link configurations with an applied moment of 7.5 Nm and 200 N axial force were evaluated. The long construct was stiffer than the short construct irrespective of whether the cross-links were used (p < 0.05). The short constructs showed no significant differences between the cross-link configurations. The XL cross-link provided the highest stiffness and was 14.9% stiffer than the one without a cross-link. The long construct resulted in reduced stress to the adjacent vertebral bodies and screw necks, with 66.7% reduction in bending stress on L2 when the XL cross-link was used. Thus, the stability for L1 burst fracture fixation was best achieved by using long segmental posterior instrumentation constructs and an XL cross-link configuration. Cross-links did not improved stability when a short structure was used.


Assuntos
Parafusos Ósseos , Fixação Interna de Fraturas/instrumentação , Fraturas por Compressão/cirurgia , Vértebras Lombares/lesões , Desenho de Prótese , Fraturas da Coluna Vertebral/cirurgia , Vértebras Torácicas/lesões , Adulto , Simulação por Computador , Módulo de Elasticidade , Análise de Falha de Equipamento , Análise de Elementos Finitos , Fixação Interna de Fraturas/métodos , Humanos , Instabilidade Articular/prevenção & controle , Vértebras Lombares/cirurgia , Modelos Biológicos , Amplitude de Movimento Articular , Vértebras Torácicas/cirurgia
17.
Int J Mol Sci ; 13(10): 12880-9, 2012 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-23202927

RESUMO

The visible luminescence from Ge nanoparticles and nanocrystallites has generated interest due to the feasibility of tuning band gap by controlling the sizes. Germanium (Ge) quantum dots (QDs) with average diameter ~16 to 8 nm are synthesized by radio frequency magnetron sputtering under different growth conditions. These QDs with narrow size distribution and high density, characterized using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) are obtained under the optimal growth conditions of 400 °C substrate temperature, 100 W radio frequency powers and 10 Sccm Argon flow. The possibility of surface passivation and configuration of these dots are confirmed by elemental energy dispersive X-ray (EDX) analysis. The room temperature strong visible photoluminescence (PL) from such QDs suggests their potential application in optoelectronics. The sample grown at 400 °C in particular, shows three PL peaks at around ~2.95 eV, 3.34 eV and 4.36 eV attributed to the interaction between Ge, GeO(x) manifesting the possibility of the formation of core-shell structures. A red shift of ~0.11 eV in the PL peak is observed with decreasing substrate temperature. We assert that our easy and economic method is suitable for the large-scale production of Ge QDs useful in optoelectronic devices.


Assuntos
Germânio/química , Pontos Quânticos/química , Microscopia de Força Atômica , Tamanho da Partícula , Propriedades de Superfície , Temperatura , Difração de Raios X
18.
Proc Inst Mech Eng H ; 226(7): 510-20, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22913098

RESUMO

The wrist is the most complex joint for virtual three-dimensional simulations, and the complexity is even more pronounced when dealing with skeletal disorders of the joint such, as rheumatoid arthritis (RA). In order to analyse the biomechanical difference between healthy and diseased joints, three-dimensional models of these two wrist conditions were developed from computed tomography images. These images consist of eight carpal bones, five metacarpal bones, the distal radius and ulna. The cartilages were developed based on the shape of the available articulations and ligaments were simulated via mechanical links. The RA model was developed accurately by simulating all ten common criteria of the disease related to the wrist. Results from the finite element (FE) analyses showed that the RA model produced three times higher contact pressure at the articulations compared to the healthy model. Normal physiological load transfer also changed from predominantly through the radial side to an increased load transfer approximately 5% towards the ulnar. Based on an extensive literature search, this is the first ever reported work that simulates the pathological conditions of the rheumatoid arthritis of the wrist joint.


Assuntos
Artrite Reumatoide/fisiopatologia , Cartilagem Articular/fisiopatologia , Força da Mão , Modelos Biológicos , Articulação do Punho/fisiopatologia , Força Compressiva , Simulação por Computador , Humanos , Estresse Mecânico
19.
Med Eng Phys ; 34(9): 1294-302, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22277308

RESUMO

Understanding the pathomechanics involved in rheumatoid arthritis (RA) of the wrist provides valuable information, which will invariably allow various therapeutic possibilities to be explored. The computational modelling of this disease permits the appropriate simulation to be conducted seamlessly. A study that underpins the fundamental concept that produces the biomechanical changes in a rheumatoid wrist was thus conducted through the use of finite element method. The RA model was constructed from computed tomography datasets, taking into account three major characteristics: synovial proliferation, cartilage destruction and ligamentous laxity. As control, a healthy wrist joint model was developed in parallel and compared. Cartilage was modelled based on the shape of the articulation while the ligaments were modelled with linear spring elements. A load-controlled analysis was performed simulating physiological hand grip loading conditions. The results demonstrated that the diseased model produced abnormal wrist extension and stress distribution as compared to the healthy wrist model. Due to the weakening of the ligaments, destruction of the cartilage and lower bone density, the altered biomechanical stresses were particularly evident at the radioscaphoid and capitolunate articulations which correlate to clinical findings. These results demonstrate the robust finding of the developed RA wrist model, which accurately predicted the pathological process.


Assuntos
Artrite Reumatoide/fisiopatologia , Análise de Elementos Finitos , Fenômenos Mecânicos , Punho/fisiopatologia , Fenômenos Biomecânicos , Osso e Ossos/fisiopatologia , Humanos , Amplitude de Movimento Articular , Software , Estresse Mecânico
20.
Int. j. morphol ; 29(4): 1321-1325, dic. 2011. ilus
Artigo em Inglês | LILACS | ID: lil-627009

RESUMO

Clinical practice in our country showed a lack of suitable implants that perfectly match the anthropometry of the local population. However, there have been no reports or comprehensive studies conducted to substantiate this argument. We therefore prospectively studied 120 hips from sixty subjects with an average age of 25+/-5.18 years old. The average weight and height were 61.48+/-13.84 kg and 1.65+/-9.63 m respectively. The exclusion criteria were pregnant woman, those who had injury to the hip joint, and those with implant or prosthesis. Four parameters were measured ­ the femoral head diameter (FHD), femoral neck length (FNL), femoral neck width (FNW) and collo-diaphyseal angle (CDA). Statistical analysis showed no significant differences between left and right femora but significant differences were found between male and female subjects. The results for the male and female femurs are as follows ­ FHD: 43.6+/-3.1 mm and 38.9+/-2.2 mm; FNL: 91.1+/-5.7 mm and 81.8+/-4.3 mm; FNW: 28.9+/-3.4 mm and 26.0+/-4.3 mm; CDA: 132.3°+/-3.4° and 129.9°+/-4.0°. This data could be used as a guideline to design a more suitable implant for the Malay population which covers most of the South East Asian countries.


Problemas con respecto al tamaño de los implantes en relación a cada población se han convertido en una cuestión esencial para la sociedad ortopédica. Varios factores han sido identificados en la literatura, los que pueden afectar la estabilidad del implante, especialmente en el fémur proximal. Se estudió prospectivamente 120 caderas mediante imágenes de tomografía computarizada. Sesenta sujetos fueron reclutados, edad media 25+/-5,18 años, peso de 61,48+/-13,84 kg y altura de 1,65+/-9,63m. Los criterios de exclusión para este estudio incluyeron a mujeres embarazadas, quienes hubiesen experimentado lesiones cadera, uso de implantes o prótesis. Nuestros datos se compararon usando las pruebas de Anderson-Darling y t-test. Los parámetros medidos fueron diámetro de la cabeza femoral (FHD), longitud del cuello femoral (FNL), ancho del cuello femoral (FNW) y el ángulo cuello-diafisial (CDA). Los resultados de los fémures masculinos y femeninos fueron los siguientes: FHD 43,6 +/- 3,1 mm y 38,9 +/- 2,2 mm, FNL 91,1 +/- 5,7 mm y 81,8 +/- 4,3 mm, FNW 28,9 +/- 3,4 mm y 26,0 +/- 4,3 mm; CDA 132.3 +/- 3.4 y 129.9 +/- 4,. Este estudio prospectivo y transversal centrado en la población malaya, proporcionó información esencial sobre el valor normal de la porción proximal del fémur, datos que mejorarán el conocimiento de los aspectos anatómicos y, finalmente, ayuden al diseño del vástago femoral en la artroplastía total de cadera (ATC). Los resultados proporcionarán una nueva comprensión por parte del cirujano ortopédico.


Assuntos
Humanos , Masculino , Feminino , Adulto , Fêmur/anatomia & histologia , Fêmur , Tomografia Computadorizada por Raios X , Malásia , Estudos Prospectivos
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