RESUMEN
El dolor facetario lumbar es una de las principales causas de dolor lumbar; representa alrededor del 15-56%. La articulación facetaria estabiliza la columna vertebral, tiene un rol fundamental en el soporte, distribución del peso y regulación de los movimientos rotacionales de la columna. Por ello, el conocimiento de la anatomía y de la biomecánica de esta articulación ayuda a tener una mejor comprensión de su participación en la fisiopatología del dolor lumbar y, por ende, mejora su abordaje diagnóstico y terapéutico. Nosotros revisamos aquí los conceptos actuales de embriología, anatomía, biomecánica y la correlación clínica/imagenológica de los cambios asociados a la enfermedad degenerativa facetaria de la columna lumbar.
Low back pain is a very common reason for emergency room consultation, it is found in approximately 60% of adults, and, within it, facet lumbar pain is one of the main causes, accounting for about 15-56% of low back pain cases. The facet joint stabilizes the spine, helps to distribute loads and has a fundamental role in support, weight distribution, and rotational movements regulation of the spine. Consequently, knowledge of the anatomy and biomechanics of this joint is helpful to have a better understanding of their contribution to the low back pain pathophysiology and, therefore, improving diagnostic and therapeutic approaches. This paper aims to review the current concepts of embryology, anatomy, biomechanics, and clinical/imaging correlation of the changes associated with lumbar degenerative facet disease
Asunto(s)
Humanos , Dolor de la Región Lumbar , Osteoartritis , Columna Vertebral , Anatomía , ArticulacionesRESUMEN
Objective To analyze the stress distributions under static loading and impact simulation in the process of tibial plateau fracture using finite element analysis,providing evidence for individualized diagnosis and treatment of tibial plateau fracture.Methods A healthy male volunteer was recruited.A 3D finite element model of a whole knee joint with ligaments,menisci and articular surfaces was generated using CT,MRI and 3D finite element software.The knee joint model was given the nature and parameters after reconstruction.According to the features of tibial plateau fracture,different operating conditions were designed.The stress distributions under static loading and impact simulation in the process of tibial plateau fracture were characterized by finite element analysis.Results Under static loads on the lateral condyle of the tibia,the stress was mainly concentrated on the front edge of the tibial plateau,especially the lateral stress.The stress on the medial condyle of the tibia was significantly increased,and the medial stress extended downwards to the tibial shaft.When the vertical stress moved towards outside,it extended from both sides of the internal and external condyles downwards to the tibia,and the value of lateral platform stress was slightly larger than that on the inside.In collisions,the stresses distributed on the neutral position were the same with the static loads.The stress on the medial condyle of the tibia was significantly increased,extending downwards the tibial shaft when it fell to the inside slope.When it fell to the outside slope,the stress on the tibial plateau was mainly distributed on most of the front edges of lateral and medial platforms,and the stress distributed on the fibula increased obviously.Conclusions The medial tibial plateau plays a major role in bearing stress loads.The stress is more concentrated on the lateral platform but distributed on a larger area of the medial platform,extending downwards the metaphysis.Therefore,small split fractures are likely to occur on the outer edge of the platform while fractures of a large fragment are likely to occur on the medial platform,even involving the metaphysis.
RESUMEN
ABSTRACT. Introduction: some studies on the effect of zirconia aging mention a degree of reduction of zirconia′s fracture strength varying from 20 to 40%, while other authors argue that aging does not affect the material′s strength. The aim of this study was to evaluate the response of a zirconia abutment subjected to static loads and artificial aging using the finite element method (FEM). Methods: modeling of the Tapered Screw- Vent implant and the zirconia Zimmer® abutment (Zimmer Dental1 900 Aston Avenue Carlsbad, CA 92008-7308 USA). Four models were designed: one with an implant of 3.7 mm in diameter and a 3.5 mm diameter abutment, another with an implant of 4.7 mm in diameter and a 4.5 mm diameter abutment, and other two with the same dimensions but changing the final fracture limit to 40%, analyzing the response of different components to specific loads. Results: models subjected to decreases in zirconia abutment fracture strength did not show zirconia differences in terms of von Mises values. A factor of safety allowed observing the working threshold of the zirconia abutment; failure occurred at values lower than 1. Conclusions: by modifying zirconia′s properties in order to simulate aging, the factor of safety decreases at values lower than 1. However, the applied forces under which the safety factor decreases are higher than normal masticatory forces.
RESUMEN. Introducción: estudios sobre el efecto del envejecimiento de la circona refieren una disminución de la resistencia a la fractura de la circona que varía del 20 al 40%, mientras que otros argumentan que no influye en la resistencia del material. El propósito de este estudio fue evaluar la respuesta de un pilar de circona sometido a carga estática y envejecimiento artificial usando el método de elementos finitos (MEF). Métodos: se modelaron el implante Tapered Screw-Vent y el pilar de circona Zimmer® (Zimmer Dental1 900 Aston Avenue Carlsbad, CA 92008- 7308 USA). Se diseñaron cuatro modelos: uno con implante de 3,7 de diámetro y pilar de 3,5 mm de diámetro, otro con un implante de 4,7 de diámetro y un pilar de 4,5 mm de diámetro, y otros dos con las mismas dimensiones pero modificando el limite último de fractura en un 40%. Se observó el comportamiento de los diferentes componentes ante la carga. Resultados: en los modelos donde se aplicó la disminución de la resistencia a la fractura del pilar de circona, no se observaron diferencias en la circona en cuanto a los valores de von Mises. Se generó un coeficiente de seguridad que permitió observar el umbral de trabajo del pilar de circona, a valores inferiores a 1 se presentó la falla. Conclusiones: al modificar las propiedades de la circona, para simular el envejecimiento, el factor de seguridad disminuye a valores inferiores a 1. Sin embargo, las fuerzas aplicadas bajo las cuales disminuye el factor de seguridad son superiores a las fuerzas de la masticación normal.