CESAR AUGUSTO MARTINS PEREIRA

(Fonte: Lattes)
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Departamento de Ortopediae Traumatologia, Faculdade de Medicina
LIM/41 - Laboratório de Investigação Médica do Sistema Músculoesquelético, Hospital das Clínicas, Faculdade de Medicina

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  • article
    Estudo biomecânico do comportamento de diferentes espessuras de capa de cimento ósseo em novo modelo de prótese modular diafisária femoral em cão submetidas a ensaio de torção
    (2013) NINA, Marcos Ishimoto Della; FERRIGNO, Cassio Ricardo Auada; PEREIRA, Cesar Augusto Martins; ALVES, Flavio Rocha; HERNANDEZ, Arnaldo Jose
    Background: The feasibility of modular cemented prosthesis in the femoral diaphysis was demonstrated in dogs, but several authors report loosening of bone-cement-implant interface as a major complication and have yet to reach a consensus on the ideal cement layer thickness for reducing postoperative morbidity. The objective of this study was to evaluate the stabilization of the prosthesis using different thicknesses of cement layer, subjected to torsion forces. Materials, Methods & Results: For this study 48 femurs from 24 dogs weighing over 15 kg were used. The animals used did not have any prior diagnosis of bone or nutritional diseases, which was an exclusion criteria for this study. All biological materials were obtained immediately after death or euthanasia of the animal, and then subjected to conventional storage in a freezer at a temperature of - 24 degrees C. The prosthesis was composed of a cylindrical part with rods for attachment to the intramedullary canal, made of alloy steel 316L. After thawing the femurs and subsequent stabilization at room temperature we performed osteotomies of the femoral diaphysis with an oscillating saw and the installation of the prosthesis. As preparatory measures for prosthesis fixation with cement, the intramedullary canals were cleaned, washed with saline and aspirated. They were separated in four groups, the first group with eight femurs used a cement mantle of 1.0 to 1.5 mm, the second group, with eight femurs, used a cement mantle of 2.0 to 2.5 mm and the third group, with eight femurs, used a cement layer of 3.0 to 3.5 mm. The femurs were submitted to destructive torsion tests using a universal testing machine with a load cell of 981 N (100 kg) and an essay speed of 22 mm / min. They were evaluated due to the values of torsional rigidity and maximum torque shown by the implant, bone and bone cement interface. The fourth group consisted of the remaining intact femurs, they were evaluated using the same torsion test used on the other groups. The results were analyzed using the Statistical Analysis System (SAS, 2001) and the normality of residuals was previously verified by the Shapiro-Wilk test. It was established to conduct the testing using an external rotation protocol in order to standardize, assuming a situation where the dog was in movement during a uniform curvilinear motion, trying to mimic a situation where the rotational forces were acting more significantly on the femur. Discussion: In our study the importance of cleaning up the intramedullary canal for proper bone cement penetration, a good reaming of the intramedullary canal and drying the area before the cement implantation was made clear. Statistical analysis showed that the thicknesses of the cement layer ranging from 1 mm to 2.5 mm, although bringing a gradual increase in maximum torque and torsional rigidity, are not sufficient to be statistically significant and may be considered equal in their biomechanical behavior assessed by this study. A similar result was found when we compared the 2 mm to 3.5 mm layers. The comparison that was statistically significant and can be considered in relation to the different biomechanical behavior of the cement layer was seen between the group I of 1 mm to 1.5 mm, and group III of 3 mm to 3.5 mm. Although some results were not statistically significant we must remember that, in absolute values, the torsional rigidity and maximum torque increased linearly with the increasing of the cement layer. From these results we can infer about the real advantage of using a thicker cement layer over an increment in the diameter of the intramedullary component, giving greater resistance to the prosthesis.
  • article 0 Citação(ões) na Scopus
    Avaliação mecânica e de composição de liga metálica de dois tamanhos de anéis para fixador externo circular de três diferentes fabricantes para cães
    (2014) SANTOS, Jaqueline Franca dos; FERRIGNO, Cassio Ricardo Auada; PEREIRA, Cesar Augusto Martins; ABURAYA, Jim Heiji; DRIGO, Evandro; SOUZA, Alexandre Navarro Alves de; CAQUIAS, Daniela Fabiana Izquierdo
    Background: Circular external skeletal fixator Ilizarov is a fixation method widely used to stabilize fractures. The method is performed using several components but the ring stands out as the fundamental component of this device, and compression loads in the same plane of the ring are mainly due to the wires connected from one side to another of the implant. The axial load is reached on the rings with a proper tension distractor device connected to the wires and fixed with bolts, washers and nuts during surgical procedure. Additional loads to axial tension are employed during patient's physical activities after surgery. The study aimed to compare the resistance to axial compression load and analyze the alloy composition of the Ilizarov rings with different diameter sizes and alloys. Materials, Methods & Results: We tested two diameters of rings acquired from three manufacturers for mechanical axial compression. Manufacture sample (N = 30 rings of each trademark) was divided into two groups (60 and 80 diameter mm). The tests to evaluate strength and deformation parameters were performed in a universal testing machine Kratos (R) 3.000 MP KE model, equipped with a load cell of 3000 N with test speed of 10 mm per minute. We also evaluated the elemental alloy composition by the method of the TTPIXE (Thick Target Proton Induced X-Ray Emission) in external PIXE. The Kolmogorov-Smirnov test was used to confirm normal distribution of the data. The comparison between results from manufacturers A, B and C for the two diameters was performed with one-way ANOVA with a post hoc Tukey's test for normal distribution and Kruskal-Wallis with a post hoc Dunn's test was used for means comparison without Gaussian distribution. The level of significance was set at 5 % (P < 0.05). The results presented that metal alloy of circular external skeletal fixator rings are mainly composed of aluminum and there are differences in aluminum percentage of alloy composition between different trademarks. Differences between tree manufactures were also founded in the resistance to axial mechanical compression tests. The rings of both diameters (60 and 80 mm) provided from manufacturer A were more rigid than other trademarks. A greater resilience was also founded in the 80 mm ring of trademark A than B and C. Discussion: Several trademarks of veterinary orthopedic implants are available but the mechanical properties of these implants are unknown. The selection of material for the implant should starts with the identification of the properties required for the application in question and thus meets the expected behavior. Due to the features displayed for each element and examining the alloy components manufacturer for the two diameters tested, it was found that it was an alloy with a lower concentration of aluminum with the addition of copper or copper and zinc, which increases the strength and stiffness of the material. Despite trademarks differences in axial resistance and alloy composition, we believe that the rings provided from all three manufacturers have a good quality based in the minimum values which demonstrated higher resistance to axial loads. Apparently, the mechanical properties of these rings suggest that other factors could be responsible for implant failure. Future studies are encouraged to detect if the other circular external skeletal fixator Ilizarov components could be responsible for implant loss.
  • article 0 Citação(ões) na Scopus
    Estudo mecânico in vitro da resistência a forças axiais dos parafusos canulado e convencional de 3,5 mm de diâmetro em fraturas de cabeça e colo femoral
    (2014) FERRIGNO, Cassio Ricardo Auada; BACCARIN, Daniel Castelo Branco; PEREIRA, Cesar Augusto Martins; FERREIRA, Marcio Poletto
    Background: Proximal femoral fractures account for 25% of all femoral fractures in dogs and are more common in young animals. Osteosynthesis of femoral head and neck fractures is a complex procedure that can be performed using conventional screws or wires. However, proper fracture reduction and fixation are difficult to achieve and, despite many advancements, such fractures remain challenging to solve. Cannulated screws have good compressive capacity and can be employed to simplify the surgical procedure while optimizing outcomes. This study was designed to compare the resistance of conventional and cannulated screws to axial loading following experimental femoral neck fracture in dogs. Materials, Methods & Results: Fourteen cadaveric canine femurs were used in this study. Femurs were collected from dogs over 20 pounds in body weight with no gross or radiographic signs of orthopedic disease. Cadaveric femurs were submitted to experimental femoral neck fracture using a Gigli saw and allocated to osteosynthesis using either conventional or cannulated screws (seven bones each). All screws were inserted below the greater trochanter of the femur from the lateral aspect of the bone and screw topography confirmed radiographically. Test specimens were then potted in polymethylmethacrylate, coupled to a hinged device and submitted to axial loading. Data on maximum load, maximum displacement, load within the proportional limit, offset within the proportional limit and load required to produce a 3 mm displacement were collected. Mean values were calculated and compared using the Student's t test (P < 0.05). Mean values varied greatly within groups. Maximum load and displacement correspond to the critical point from which biomechanical testing becomes destructive. Data were missing from one test specimen (conventional screw group) due to abrupt diaphyseal fracture at the start of the axial loading trial. Discussion: The canine femur was selected as an experimental model in this project due to the high incidence of femoral neck fractures in dogs. Also, studies on proximal femoral fracture osteosynthesis using cannulated screws are scarce. The effectiveness of the compression osteosynthesis technique employed in this trial has been confirmed in several canine proximal femoral fracture studies, with reported success rates between 2 and 21%. Success rate variability could be due to substantial individual differences, as suggested by the large intragroup variation in this trial. The biomechanical behaviour of conventional sliding hip screws (SHC) and cannulated screws following experimental femoral neck fracture osteosynthesis was compared. Increased stiffness was achieved with SHCs, possibly due to more efficient transmission of compressive forces to cortical bone under the plate. Compression screws act by transmitting compressive forces to cancellous bone under the fracture line. Replication of this scenario in this trial supports the recommendation that the lowest screw be inserted as close as possible to the medial cortex of the femur, which is stiffer than the cancellous bone in the femoral head. Under the conditions studied, mean maximum load values were higher when bone screws were inserted closer to the medial cortex of the femoral shaft and the proximal aspect of the femoral head, regardless of screw type. The opposite scenario was also observed (i.e. the farther from the medial cortex of the femoral shaft, the lower the mean maximum load). In this trial, conventional and cannulated screws were equally resistant to axial loading. However, femoral neck fracture osteosynthesis using cannulated screws was easier to perform.