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Doctoral Thesis
Full name
Gustavo Silva Abrahão
Knowledge Area
Date of Defense
Ribeirão Preto, 2011
Shimano, Antonio Carlos (President)
Engel, Edgard Eduard
Garcia, Flávio Luís
Reis, Andréa Candido dos
Roesler, Carlos Rodrigo de Mello
Title in Portuguese
Influência do preparo do orifício piloto na ancoragem dos parafusos com diâmetro interno cônico
Keywords in Portuguese
Coluna vertebral
Dispositivos de fixação ortopédica
Parafusos ósseos
Vértebras lombares
Abstract in Portuguese
Objetivo: Avaliar a influência do diâmetro e do modo de preparação do orifício piloto na resistência ao arrancamento e no torque de inserção dos parafusos pediculares do sistema de fixação vertebral com diâmetro interno cônico. Métodos: foram realizados ensaios mecânicos com parafusos pediculares com alma cônica e diâmetro de 4,2mm e 5,2mm inseridos nos pedículos vertebrais lombares de suínos. Foi considerada a maior medida de torque obtida com torquímetro. O orifício piloto foi confeccionado com de broca e sondas (pontiaguda e cortante) com diferentes diâmetros. Resultados: Os resultados demonstraram que utilizando o parafuso de 4,2mm, a perfuração com orifício igual ou inferior ao menor diâmetro interno do parafuso, aumentou o torque e a resistência ao arrancamento. Perfurações com diferentes instrumentos apresentaram comportamento semelhante. Perfurações com sondas permitiram que os orifícios confeccionados com dimensões superiores ao menor diâmetro interno do parafuso apresentassem resistência semelhante a das perfurações com dimensões iguais ao menor diâmetro interno do implante, realizadas com sondas e brocas. Conclusões: Nos parafusos de 4,2mm, o diâmetro e o modo de preparação do orifício influenciam o torque e a resistência, nos de 5,2mm apenas o torque de inserção. Não há correlação entre força de arrancamento e torque de inserção.
Title in English
Effect of pilot hole preparation of anchorage of pedicle screws with conical internal diameter
Keywords in English
Bone screws
Devices for orthopedic fixation
Lumbar vertebra
Vertebral spine
Abstract in English
Objective: We evaluated the influence of the diameter and the preparation of the pilot hole in the resistance to the pulling out and to the strength when inserting the pedicle screws of the vertebral fixation system with conical internal diameter. Methods: mechanical experiments were done with pedicle conical screws of 4.2mm and 5.2mm diameter. They were inserted in the vertebral pedicles of swine. We considered the largest torque measure obtained with a torque wrench. The pilot hole was manufactured with a drill and a probe (pointed and sharp) which had different diameters. Results: While testing the 4.2mm screw, the perforation of holes, with measure equal or inferior to the lesser internal diameter of the screw, increased the torque and the resistance to the pulling out. Perforations with different instruments have presented similar results. Perforations with probes allowed that orifices manufactured with superior dimensions, comparing to the lesser measure of internai diameter of the screw, showed similar resistance to the perforations in holes with the dimensions of equal or lesser internal diameter implant, made with probes and drills. Conclusions: For 4.2mm screws, the diameter and the preparation of the hole influence the strength and resistance. For the 5.2mm screws, there is only the influence of the insertion torque. There is no correlation between pulling out strength and insertion torque.
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