Desenvolvimento de um dispositivo para radiografias de estresse do tornozelo fabricado por manufatura aditiva

Abstract

For the correct diagnosis of some ankle injuries it is necessary to take stress radiographs. However, this diagnostic technique is dependent on several factors, and the experience of the health professional is a determining factor for the quality of the examination. In this case, the health professional is usually exposed to radiation during the ankle fixation operation in a position suitable for the visualization of the trauma. Therefore, the development of new methods of patient positioning is extremely important so that there is no interference of the human factor in the diagnosis and, consequently, reduce the exposure to radiation, because at high rates it is harmful to the human being. In view of this, this work aims to develop an ankle support device, modular and with simplified adjustments, manufactured completely by additive manufacturing. The equipment must allow the realization of stress maneuvers and subsequent fixation without the direct action of the health professional during the procedure, besides not interfering significantly in the radiographic image. The project was conceived with the use of simple mechanical elements, such as spherical joint, screw fixation systems, and regulation systems by means of guides. The choice of material took into consideration the density, mechanical resistance and the manufacturing process used. Three polymeric materials (ABS, PLA and Tritan™) were tested with two types of filling (rectilinear and full honeycomb) in order to investigate the most suitable for application in radiographic examinations. The fabrication was done by an additive manufacturing technique called FFF. The prototype was built and then functionality tests were performed on the device with the simulation of stress maneuvers application. By analyzing the radiographic images of the materials studied, the ABS material with rectilinear filling showed better final contrast with the medium. The device is capable of simulating the movements of dorsiflexion, plantar flexion, inversion, eversion, external rotation, anterior drawer and horizontal translation, with sufficient variation ranges for each movement. Additionally, a structural analysis was performed using the finite element method in order to evaluate the resistance of the device under loading conditions. Analyzing the displacement levels and equivalent tension of Von Mises, considering a single positioning and the simplifications imposed on the models, it was verified that the device was not damaged for a total load of up to 100 kg, being, therefore, dimensioned for this situation.