TOMAZ PUGA LEIVAS

Índice h a partir de 2011
5
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Unidades Organizacionais
Instituto do Coração, Hospital das Clínicas, Faculdade de Medicina
Instituto de Ortopedia e Traumatologia, Hospital das Clínicas, Faculdade de Medicina
LIM/41 - Laboratório de Investigação Médica do Sistema Músculoesquelético, Hospital das Clínicas, Faculdade de Medicina

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  • article 6 Citação(ões) na Scopus
    Evaluation of Laser Marked ASTM F 139 Stainless Steel in Phosphate Buffer Solution with Albumin
    (2014) PIERETTI, Eurico F.; PALATNIC, Ricardo P.; LEIVAS, Tomaz P.; COSTA, Isolda; NEVES, Mauricio D. M. das
    Albumin is the most abundant protein found in human serum and sinovial fluids. Investigations on its effects on the corrosion resistance of metallic biomaterials have led to controversial conclusions. The BSA (bovine serum albumin) concentration used in most of the studies is below the usual concentration found in the human physiological fluids. This is possibly the reason for the lack of agreement on the conclusions reported in literature. The aim of this study is to evaluate the effect of albumin in concentration on the susceptibility to corrosion of the ASTM F139 austenitic stainless steel (SS) used in fabrication of orthopedic implants, specifically on the areas marked by a Nd: YAG laser. The electrolyte used was a phosphate buffer solution (PBS) and the effect of albumin was investigated by adding 10 g/L into the electrolyte and comparing the corrosion resistance in the two environments, with and without albumin, by electrochemical methods. The Mott-Schottky approach was used to evaluate the electronic properties of ASTM F139 SS oxide layer marked by laser beam. The results showed a strong effect of the albumin on the electronic properties of the passive film and on the resistance to localized corrosion. The albumin changes the flat band potential position, increasing the oxide layer doping densities. The laser marked surface showed lower corrosion resistance in the electrolyte with albumin, when compared to the tests performed with pure PBS.
  • article 7 Citação(ões) na Scopus
    Measurement of the concentration and size of aerosol particles and identification of the sources in orthopedic surgeries
    (2012) PEREIRA, Marcelo Luiz; VILAIN, Rogerio; LEIVAS, Tomaz Puga; TRIBESS, Arlindo
    In this study, the measurement of the concentration and size of particles and the identification of their sources were carried out at five orthopedic surgeries. The aerosol concentration and particle size distribution, ranging from 0.3 mu m 10 mu m, were measured and related to the type of indoor activity. The handling of surgical linen and gowns, handling of the patient, use of electrosurgical apparatus, use of a bone saw, handling of equipment, and cleaning of the room were identified as the most important sources of particles, with each of these activities posing different risks to the health of the patients and workers. The results showed that most of the particles were above 0.5 mu m and that there was a strong correlation among all particles of sizes above 1 mu m. Particles with diameters in the range of 0.3 mu m-0.5 mu m had a good correlation only with particles in the ranges of 0.5 mu m-1.0 mu m and 1.0 mu m-3.0 mu m in three of the surgeries analyzed. Findings led to the conclusion that most of the events responsible for generating aerosol particles in an orthopedic surgery room are brief, intermittent, and highly variable, thus requiring the use of specific instrumentation for their continuous identification and characterization.
  • article 8 Citação(ões) na Scopus
    Electrochemical Study of a Laser Marked Biomaterial in Albumin Solution
    (2014) PIERETTI, Eurico F.; COSTA, Isolda; MARQUES, Rogerio A.; LEIVAS, Tomaz P.; NEVES, Mauricio D. M. das
    Proteins are widely used in solutions in order to simulate the physiological fluids and study corrosion mechanisms. The present work appraised the ASTM F 139 austenitic stainless steel (SS), employed in prostheses manufacture, and engraved by a nanosecond laser beam, using a phosphate buffered solution with 10 g/L of bovine serum albumin (PBS + BSA). Due to the complexity of the interaction between protein and the biomaterial, it was necessary to use higher BSA concentrations, however, similar to those found in human serum. The electrochemical tests consisted in monitoring the open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and cyclic polarisation measurements. The results showed that the laser marked areas are more susceptible to corrosion; suggesting that the laser marking technique has a more preponderant effect on the passive film protective character than the albumin addition to the electrolyte.
  • article 13 Citação(ões) na Scopus
    Axial compressive strength of human vertebrae trabecular bones classified as normal, osteopenic and osteoporotic by quantitative ultrasonometry of calcaneus
    (2017) CESAR, R.; LEIVAS, T. P.; PEREIRA, C. A. M.; BOFFA, R. S.; GUARNIERO, R.; REIFF, R. B. D. M.; NETTO, A. M.; FORTULAN, C. A.; ROLLO, J. M. D. A.
    Introduction: Biomechanical assessment of trabecular bone microarchitecture contributes to the evaluation of fractures risk associated with osteoporosis and plays a crucial role in planning preventive strategies. One of the most widely clinical technics used for osteoporosis diagnosis by health professionals is bone dual-energy X-ray absorptiometry (DEXA). However, doubts about its accuracy motivate the introduction of congruent technical analysis such as calcaneal ultrasonometry (Quantitative Ultrasonometry - QUS). Methods: Correlations between Bone Quality Index (BQI), determined by calcaneal ultrasonometry of thirty (30) individuals classified as normal, osteopenic and osteoporotic, and elastic modulus (E) and ultimate compressive strength (UCS) from axial compression tests of ninety (90) proof bodies from human vertebrae trabecular bone, which were extracted from cadavers in the twelfth thoracic region (T12), first and fourth lumbar (L1 and L4). Results: Analysis of variance (ANOVA) showed significant differences for E (p = 0.001), for UCS (p = 0.0001) and BQI. Spearman’s rank correlation coefficient (rho) between BQI and E (r = 0.499) and BQI and UCS (r = 0.508) were moderate. Discussion: Calcaneal ultrasonometry technique allowed a moderate estimate of bone mechanical strength and fracture risk associated with osteoporosis in human vertebrae. © 2017, Brazilian Society of Biomedical Engineering. All rights reserved.
  • article 20 Citação(ões) na Scopus
    Comparison between the effects of platelet-rich plasma and bone marrow concentrate on defect consolidation in the rabbit tibia
    (2011) BATISTA, Marco Antonio; LEIVAS, Tomaz Puga; RODRIGUES, Consuelo Junqueira; ARENAS, Gessica Cantadori Funes; BELITARDO, Donizeti Rodrigues; GUARNIERO, Roberto
    OBJECTIVE: To perform a comparative analysis of the effects of platelet-rich plasma and centrifuged bone marrow aspirate on the induction of bone healing in rabbits. METHOD: Twenty adult, male New Zealand rabbits were randomly separated into two equal groups, and surgery was performed to create a bone defect (a cortical orifice 3.3 mm in diameter) in the proximal metaphysis of each rabbit's right tibia. In the first group, platelet-rich plasma was implanted in combination with beta-tricalcium phosphate (platelet-rich plasma group), and in the second group, centrifuged bone marrow in combination with beta-tricalcium phosphate (centrifuged bone marrow group) was implanted. After a period of four weeks, the animals were euthanized, and the tibias were evaluated using digital radiography, computed tomography, and histomorphometry. RESULTS: Seven samples from each group were evaluated. The radiographic evaluation confirmed the absence of fractures in the postoperative limb and identified whether bone consolidation had occurred. The tomographic evaluation revealed a greater amount of consolidation and the formation of a greater cortical bone thickness in the platelet-rich plasma group. The histomorphometry revealed a greater bone density in the platelet-rich plasma group compared with the centrifuged bone marrow group. CONCLUSION: After four weeks, the platelet-rich plasma promoted a greater amount of bone consolidation than the bone marrow aspirate concentrate.