The scanning electron microscope (SEM) results of bone interface of titanium-coated 317L plate screw are reported in this article. 317L plate screw had a rough surface composed of sprayed pure titanium which formed a ...The scanning electron microscope (SEM) results of bone interface of titanium-coated 317L plate screw are reported in this article. 317L plate screw had a rough surface composed of sprayed pure titanium which formed a bone/metal interface in biointegration after implanted into the mandible of dog. Though a bone/metal interface in osseointegration was also formed on the surface of uncoated 317L plate screw after implantation, a smal1 space was seen between the bone and surface of the screw, indicating that the tissue compatibility of titanium-coated 317L plate screw may be better than that of the non-coated screw.展开更多
The problem of a screw dislocation interacting with a circular nano-inhomogeneity near a bimaterial interface is investigated. The stress boundary condition at the interface between the inhomogeneity and the matrix is...The problem of a screw dislocation interacting with a circular nano-inhomogeneity near a bimaterial interface is investigated. The stress boundary condition at the interface between the inhomogeneity and the matrix is modified by incorporating surface/interface stress. The analytical solutions to the problem in explicit series are obtained by an efficient complex variable method associated with the conformal mapping function. The image force exerted on the screw dislocation is also derived using the generalized Peach–Koehler formula. The results indicate that the elastic interference of the screw dislocation and the nano-inhomogeneity is strongly affected by a combination of material elastic dissimilarity, the radius of the inclusion, the distance from the center of inclusion to the bimaterial interface, and the surface/interface stress between the inclusion and the matrix. Additionally, it is found that when the inclusion and Material 3 are both harder than the matrix（ μ1 〉 μ2 and μ3 〉 μ2）, a new stable equilibrium position for the screw dislocation in the matrix appears near the bimaterial interface; when the inclusion and Material 3 are both softer than the matrix（ μ1 〈 μ2 and μ3 〈 μ2）, a new unstable equilibrium position exists close to the bimaterial interface.展开更多
Background： We aimed to use the animal model of dynamic fixation to examine the interaction of the pedicle screw surface with sun＇ounding bone, and determine whether pedicle screws achieve good mechanical stability ...Background： We aimed to use the animal model of dynamic fixation to examine the interaction of the pedicle screw surface with sun＇ounding bone, and determine whether pedicle screws achieve good mechanical stability in the vertebrae. Methods： Twenty-four goats aged 2-3 years had Cosmic pedicle screws implanted into both sides of the L2-L5 pedicles. Twelve goats in the bilateral dynamic fixation group had fixation rods implanted in L2-L3 and L4-L5. Twelve goats in the unilateral dynamic fixation group had fixation rods randomly fixed on one side of the lumbar spine. The side that was not implanted with fixation rods was used as a static control group. Results： In the static control group, new bone was formed around the pedicle screw and on the screw surthce. In the unilateral and bilateral dynamic fixation groups, large amounts of connective tissue formed between and around the screw threads, with no new bone formation on the screw surlhce; the pedicle screws were loose after the fixed rods were removed. The bone mineral density and morphological parameters of the region of interest （ROI） in the unilateral and bilateral dynamic fixation group were not significantly different （P 〉 0.05）, but were lower in the fixed groups than the static control group （P 〈 0.05）. This showed the description bone of the ROI in the static control group was greater than in the fixation groups. Under loading conditions, the pedicle screw maximum pull force was not significantly different between the bilateral and unilateral dynamic fixation groups （P 〉 0.05）： however the maximum pull force of the fixation groups was significantly less than the static control group （P 〈 0.01 ）. Conclusions： Fibrous connective tissue formed at the bone-screw interface tinder unilateral and bilateral pedicle dynamic fixation, and the pedicle screws lost mechanical stability in the vertebrae.展开更多
文摘The scanning electron microscope (SEM) results of bone interface of titanium-coated 317L plate screw are reported in this article. 317L plate screw had a rough surface composed of sprayed pure titanium which formed a bone/metal interface in biointegration after implanted into the mandible of dog. Though a bone/metal interface in osseointegration was also formed on the surface of uncoated 317L plate screw after implantation, a smal1 space was seen between the bone and surface of the screw, indicating that the tissue compatibility of titanium-coated 317L plate screw may be better than that of the non-coated screw.
文摘The problem of a screw dislocation interacting with a circular nano-inhomogeneity near a bimaterial interface is investigated. The stress boundary condition at the interface between the inhomogeneity and the matrix is modified by incorporating surface/interface stress. The analytical solutions to the problem in explicit series are obtained by an efficient complex variable method associated with the conformal mapping function. The image force exerted on the screw dislocation is also derived using the generalized Peach–Koehler formula. The results indicate that the elastic interference of the screw dislocation and the nano-inhomogeneity is strongly affected by a combination of material elastic dissimilarity, the radius of the inclusion, the distance from the center of inclusion to the bimaterial interface, and the surface/interface stress between the inclusion and the matrix. Additionally, it is found that when the inclusion and Material 3 are both harder than the matrix（ μ1 〉 μ2 and μ3 〉 μ2）, a new stable equilibrium position for the screw dislocation in the matrix appears near the bimaterial interface; when the inclusion and Material 3 are both softer than the matrix（ μ1 〈 μ2 and μ3 〈 μ2）, a new unstable equilibrium position exists close to the bimaterial interface.
文摘Background： We aimed to use the animal model of dynamic fixation to examine the interaction of the pedicle screw surface with sun＇ounding bone, and determine whether pedicle screws achieve good mechanical stability in the vertebrae. Methods： Twenty-four goats aged 2-3 years had Cosmic pedicle screws implanted into both sides of the L2-L5 pedicles. Twelve goats in the bilateral dynamic fixation group had fixation rods implanted in L2-L3 and L4-L5. Twelve goats in the unilateral dynamic fixation group had fixation rods randomly fixed on one side of the lumbar spine. The side that was not implanted with fixation rods was used as a static control group. Results： In the static control group, new bone was formed around the pedicle screw and on the screw surthce. In the unilateral and bilateral dynamic fixation groups, large amounts of connective tissue formed between and around the screw threads, with no new bone formation on the screw surlhce; the pedicle screws were loose after the fixed rods were removed. The bone mineral density and morphological parameters of the region of interest （ROI） in the unilateral and bilateral dynamic fixation group were not significantly different （P 〉 0.05）, but were lower in the fixed groups than the static control group （P 〈 0.05）. This showed the description bone of the ROI in the static control group was greater than in the fixation groups. Under loading conditions, the pedicle screw maximum pull force was not significantly different between the bilateral and unilateral dynamic fixation groups （P 〉 0.05）： however the maximum pull force of the fixation groups was significantly less than the static control group （P 〈 0.01 ）. Conclusions： Fibrous connective tissue formed at the bone-screw interface tinder unilateral and bilateral pedicle dynamic fixation, and the pedicle screws lost mechanical stability in the vertebrae.
