RESUMEN
Objective To investigate the characteristics of knee kinematics and ground reaction force (GRF), as well as the stress state of cartilage and meniscus in the process of lateral incisions at different cutting angles under expected conditions. Methods Kinematics and GRF data of 14 subjects at 45°, 90° and 135° cutting angle respectively under expected conditions were collected. The knee joint reaction force was obtained through the inverse dynamics calculation of Visual 3D. Based on three-dimensional (3D) finite element model of the knee joint, the contact process at 3 lateral cutting angles was simulated. ResultsUnder expected conditions, there were significant differences in knee joint kinematics characteristics at 3 cutting angles during contact process(P＜0.001), and the knee flexion increased with the cutting angle increasing; the vertical GRF decreased significantly with the cutting angle increasing (P＜0.001), while the horizontal GRF showed the opposite trend; for 3 cutting angles, the peak contact stress of patellar cartilage and femoral cartilage was larger at 90° cutting angle, the peak principal stress at anterior cruciate ligament (ACL) contact point was also larger at 90° cutting angle, and the following was at 135° and 45° cutting angle, respectively; the peak contact stress of lateral femoral cartilage was larger than that of medial femoral cartilage at 3 cutting angles. Conclusions The risk of knee joint injury is higher at 90° cutting angle, and the stress state of knee joint at 135° cutting angles is better than that at 90° cutting angle, and the risk of knee joint injury does not increase with the increase of cutting angle under expected conditions.
RESUMEN
Objetivos: describir las características y empleo de la trepanación corneal cónica. Métodos: se realizó un estudio experimental en el Instituto Cubano de Oftalmología Ramón Pando Ferrer de enero a diciembre de 2010. Se realizó la trepanación en diez globos oculares no útiles para trasplante, con un trépano corneal de vacío que tiene como característica fundamental la creación de un corte oblicuo. Se analizaron los parámetros: longitud del corte, grosor corneal, diámetro externo del botón, diámetro interno del botón y ángulo del corte. Se utilizó la estadística descriptiva para expresar los resultados. Resultados: la longitud media del corte fue de 1 776,7 ± 273,7 mm y el grosor corneal medio a nivel del corte fue de 850,0 ± 119,2 mm, con una diferencia entre estos de 926 mm. El diámetro externo medio del botón corneal fue de 7,6 ± 0,2 mm y el interno de 8,5 ± 0,4 mm, con una diferencia de 0,9 mm. El ángulo de corte medio fue de 28,4 ± 2,1°. Se estableció una fórmula para calcular la longitud o profundidad del corte en base a la paquimetría media del círculo en el que se realizó la trepanación para un ángulo de corte determinado. Conclusiones: se obtuvo un corte regular, simétrico y de mayor longitud que el grosor corneal y con el aspecto cónico planificado. Dicho patrón de corte provee una mayor área de contacto y una tendencia autosellante
Objectives: to describe the characteristics and use of the conic corneal trephination.Methods: an experimental study was performed in Ramón Pando Ferrer Cuban Institute of Ophthalmology from January to December 2010. Ten eyeballs not useful for transplantation underwent trephination, with a corneal vacuum trephine particularly designed to create an oblique corneal cut. The cutting length, the corneal thickness, the external diameter of the disc, the internal diameter of the disc and the cutting angle were the analyzed parameters. Descriptive statistics were applied to show the results. Results: the mean cutting length was 1776.7 ± 273.7 mm and the mean corneal thickness at the cutting point was 850.0 ± 119.2 mm , being the difference between them equals to 926 mm. The mean external diameter was 7.6 ± 0.2 mm and the internal diameter was 8.5 ± 0.4 mm, with a difference of 0.9 mm. The mean cutting angle amounted to 28.4 ± 2.1°. A formula was developed to calculate the cutting length or depth based on the mean pachymetry of the circle where the trephination is performed for a determined cutting angle. Conclusions: aregular symmetric cut was obtained, longer than the corneal thickness with the planned conic profile. Such cutting pattern provides a larger contact surface and self-sealing tendency