Browsing by Author "Gonzalez, Nicolas"

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    Conformational Changes of Poly(Maleic Anhydride-alt-styrene) Modified with Amino Acids in an Aqueous Medium and Their Effect on Cytocompatibility and Hemolytic Response
    (2023) Maine, Arianne; Tamayo, Laura; Leiva, Angel; Gonzalez, Alex; Rios, Hernan E.; Rojas-Romo, Carlos; Jara, Paul; Araya-Duran, Ingrid; Gonzalez-Nilo, Fernando; Yazdani-Pedram, Mehrdad; Santana, Paula; Leal, Matias; Gonzalez, Nicolas; Briones, Ximena; Villalobos, Valeria; Urzua, Marcela
    The conformational changes of poly-(maleic anhydride-alt-styrene) (PSMA) modified with different amino acids (PSMA-Aa) were studied in an aqueous medium as a function of ionic strength and pH. The specific viscosity of PSMA-Aa decreased with increasing salt concentration due to a more compact conformation. There was a decrease in surface tension with increasing concentrations of the modified polyelectrolyte having a greater effect for the PSMA modified with l-phenylalanine at pH 7.0, demonstrating a greater surface-active character. The conformational changes were also confirmed by molecular dynamics studies, indicating that PSMA-Aa exhibits a compact structure at pH 4.0 and a more extended structure at pH 7.0. On the other hand, the conformational changes of PSMA-Aa were related to its biological response, where the higher surface-active character of the PSMA modified with l-phenylalanine correlates very well with the higher hemolytic activity observed in red blood cells, in which the surface-active capacity supports lytic potency in erythrocytes. The cytocompatibility assays indicated that there were no significant cytotoxic effects of the PSMA-Aa. Additionally, in solvent-accessible surface area studies, it was shown that the carboxylate groups of the PSMA modified with l-phenylalanine are more exposed to the solvent at pH 7.0 and high salt concentrations, which correlates with lower fluorescence intensity, reflecting a loss of mitochondrial membrane potential. It is concluded that the study of the conformational changes in PE modified with amino acids is essential for their use as biomaterials and relevant to understanding the possible effects of PE modified with amino acids in biological systems.
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    Skyline view of the patella does not increase fracture detection: A non-inferiority diagnostic study
    (2023) Gonzalez, Nicolas; Besa, Pablo; Correa, Ignacio; Guiloff, Benjamin; Irarrazaval, Sebastian
    Purpose: Patella fractures are frequent injuries in the adult population. Initial study is made by plain radiographs and the standard set includes the skyline view of patella. Recommendation for use of this projection is variable among the experts, without data that support its performance in the diagnosis of patella fractures. The main purpose of this study was to determine the sensitivity of the antero-posterior and lateral view of the knee, without skyline view, in the diagnosis of patella fracture.
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    Traction images heavily influence lateral wall measurement in trochanteric hip fractures. A prospective study
    (2023) Carmona, Maximiliano; Gonzalez, Nicolas; Segovia, Javier; de Amesti, Martin; Zamora, Tomas; Schweitzer, Daniel
    Introduction: hip fracture represents a global health problem, with a high morbidity and mortality rate and an increasing incidence. The treatment of trochanteric fractures is reduction and osteosynthesis, and implant selection depends mainly on the stability of the fracture and lateral wall competence. Lateral wall competence has gained relevance in recent years, which led to the modification of the AO/OTA classification. However, determination of lateral wall integrity is difficult from plain radiographs; the influence of images with traction on its measurement has not been evaluated.
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    Training Program for Orthopedic Residents in Forefoot Osteotomy Skills Transference From a Simulator to a Cadaveric Surgical Scenario
    (2023) Ledermann, Gerardo; Kuroiwa, Aron; Gonzalez, Nicolas; Silva, Isadora; Villa, Andres
    IntroductionAn effective simulation program allows both the acquisition of surgical skills on the simulated model and the transfer of these skills to a surgical scenario. We designed a forefoot osteotomy training program and sought to determine the transferability to a cadaveric surgical scenario.MethodsEleven orthopedic residents and 2 foot and ankle surgeons were included. A foot simulator was used. All residents were instructed on the surgical techniques of Chevron, Akin, and triple Weil osteotomies. Eight junior residents (trainees) were enrolled in a supervised simulation program. Baseline assessment was performed on the simulator with the Objective Structured Assessment of Technical Skills (OSATS) and the Imperial College Surgical Assessment Device (ICSAD). After baseline, trainees completed a training program and had a final evaluation of proficiency on the simulator and on cadaveric specimens. Three senior residents with no simulated training (controls) and experts were assessed for comparison.ResultsAll trainees improved from a baseline OSATS score of 11 points (9-20) to a final score of 35 points (33-35) in the simulator and 34 points (32-34) in the cadaveric specimen (P < 0.01). Compared with baseline, the ICSAD results improved in path length (391 [205-544] to 131 [73-278] meters, P < 0.01) and number of movements (2756 [1258-3338] to 992 [478-1908], P < 0.01). The final OSATS and ICSAD scores did not differ from experts (P = 0.1) and were significantly different from untrained residents (P = 0.02).ConclusionsSimulated training of Chevron, Akin, and triple Weil osteotomies in orthopedic residents improved procedural proficiency, enabling successful skill transfer to a surgical scenario in cadavers.