RESUMO
The endurance properties of a femoral stem under fatigue loading must be known and the methodology proposed in this work provides the mathematical tools for designers of femoral stems and orthopedic surgeons to select the adequate material and femoral stem design with a new graph that condensate the information in an easy to use selection process. Initially, the theoretical and computational development of the fatigue analysis provides comparable results with an average error of 8.3%. And the formulated methodology with the aim of selecting the mechanical device with the best fatigue performance with an average error of 8.7%.
Assuntos
Prótese de Quadril , Estresse Mecânico , Desenho de Prótese , Fêmur/cirurgia , Análise de Elementos FinitosRESUMO
The maximum stresses on a femoral stem must be known for selecting the right size and shape of the shaft cross-sectional area for reducing the stress shielding effect generated after the total hip arthroplasty (THA) surgical procedure. The methodology proposed in this study provides the tools to the designers of femoral stems and orthopedic surgeons to select the adequate femoral stem cross section, decreasing the stiffness of the stem, thus reducing the stress shielding effect in the patient bones. The first contribution is the theoretical development of the maximum static stress calculation for 12 different femoral stem models with the beam theory, followed by the comparison with the static finite element analysis (FEA) simulations and finally the experimental corroboration of one femoral stem model measuring the strain with linear strain gages and transform it to stresses, the three different approaches provide comparable results, with a maximum average error of less than 8.5%. The second contribution is the formulation of a new selection methodology based on maximum stresses in the femoral stem and the cross section area for decreasing the stress shielding effect, optimizing the area needed for withstand the loads and decreasing the overall stiffens of the stem.
Assuntos
Artroplastia de Quadril , Prótese de Quadril , Artroplastia de Quadril/métodos , Fêmur/cirurgia , Análise de Elementos Finitos , Humanos , Desenho de Prótese , Estresse MecânicoRESUMO
Genetic breeding for cold tolerance is presented as a strategy to confront the problem of chilling temperature in Rio Grande do Sul during irrigated rice crop season. The occurence of chilling temperatures in other countries is compared to the situation in Southern Brazil. Plant developmental stages most affected by low temperatures, selection strategies available in controlled conditions and difficulties found for breeding this trait are discussed. Finally, promising selection strategies based on Physiology and Biotechnology studies are presented.
O melhoramento genético para tolerância ao frio é apresentado como estratégia para enfrentar o problema de temperatura baixa no Rio Grande do Sul durante o período de cultivo do arroz irrigado. A ocorrência de temperaturas baixas em outros países é comparada com a situação no sul do Brasil. Os estádios de desenvolvimento da planta mais afetados pela temperatura baixa, as estratégias de seleção disponíveis sob condições controladas e os problemas encontrados para o melhoramento dessa característica são discutidos. Finalmente, estratégias de seleção promissoras baseadas em estudos de Fisiologia e Biotecnologia são apresentadas.
RESUMO
Genetic breeding for cold tolerance is presented as a strategy to confront the problem of chilling temperature in Rio Grande do Sul during irrigated rice crop season. The occurence of chilling temperatures in other countries is compared to the situation in Southern Brazil. Plant developmental stages most affected by low temperatures, selection strategies available in controlled conditions and difficulties found for breeding this trait are discussed. Finally, promising selection strategies based on Physiology and Biotechnology studies are presented.
O melhoramento genético para tolerância ao frio é apresentado como estratégia para enfrentar o problema de temperatura baixa no Rio Grande do Sul durante o período de cultivo do arroz irrigado. A ocorrência de temperaturas baixas em outros países é comparada com a situação no sul do Brasil. Os estádios de desenvolvimento da planta mais afetados pela temperatura baixa, as estratégias de seleção disponíveis sob condições controladas e os problemas encontrados para o melhoramento dessa característica são discutidos. Finalmente, estratégias de seleção promissoras baseadas em estudos de Fisiologia e Biotecnologia são apresentadas.