RESUMO
Intramedullary nails are routinely used in the treatment of fractures of the femur. While their effectiveness has been demonstrated clinically, a number of complications, including bone refracture and implant failure, persist. This paper presents novel three-dimensional finite element (FE) models, at four stages of gait, of: (i) a realistic femur analogue known as third generation composite bone, and (ii) a system consisting of an intramedullary nail implanted in the femur of (i). A comparison of experimentally measured strains on the surface of the femur with those predicted by the FE model revealed good agreement. The models were then used to identify implant/bone load sharing patterns, and areas of stress concentration in both the intramedullary nail and the bone, when statically locked by one or two screws at either end. The results of this study can be used to guide future implant design and surgical procedure.
Assuntos
Fraturas do Fêmur/fisiopatologia , Fraturas do Fêmur/cirurgia , Fixação Intramedular de Fraturas/instrumentação , Fixação Intramedular de Fraturas/métodos , Marcha , Modelos Biológicos , Suporte de Carga , Pinos Ortopédicos , Simulação por Computador , Desenho Assistido por Computador , Elasticidade , Análise de Falha de Equipamento/métodos , Análise de Elementos Finitos , Humanos , Desenho de Prótese , Implantação de Prótese/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Estresse Mecânico , TorqueRESUMO
A method is presented for estimating the compression wave velocities of organic fluids, based only on their density and molecular properties. The method is applied to a search for very low-speed ultrasonic couplants, suitable for 250 MHz acoustic microscopy studies of epoxy materials. Experimental measurements confirmed that acoustic velocity could be predicted within 3% for simple fluorine-containing organic compounds, and within 10% for those with a more complex molecular structure. The compound 2-dichloropentafluoropropane (C(3 )HCl(2)F(5)), with a compression wave velocity of C(L)=638 m/s and acceptably low attenuation coefficient, was identified as a good coupling agent for acoustic microscopy studies of low speed materials.
Assuntos
Células Sanguíneas/fisiologia , Modelos Biológicos , Proteínas/fisiologia , Animais , Bactérias , Água Corporal , Adesão Celular , Separação Celular , Eritrócitos/citologia , Congelamento , Granulócitos/citologia , Humanos , Matemática , Proteínas Opsonizantes/imunologia , Fagocitose , Tensão Superficial , Termodinâmica , Fatores de TempoRESUMO
The freezing front technique for solid surface tension measurements was used to obtain the surface tensions of glutaraldehyde-fixed human erythrocytes, and fresh human lymphocytes and granulocytes in aqueous media. The results agree well with the values obtained by other methods and indicate that the freezing front technique is sufficiently sensitive to detect small differences (of the order of 0.1 ergs/cm2) in surface tension. This property, along with a number of applications for which it is uniquely suited, makes the freezing front technique an important new approach to the measurement of the surface tensions of biological cells and of small particles in general.
