A device for driving a wire or a drill precisely in given direction through a point under closed sky conditions

摘要

The paper presents a new device which allows the precise positioning of a guide through a point and in a given direction, or which can permit to reach a given bone section. Other devices exist mainly addressed to the insertion of a screw in the correct position on endo-medullary nails, but these are usually based on the knowledge of the geometry of the nail, and are therefore made by the maker of the nail. In other instances, often the doctors use trial drilling under fluoroscopy to place a kirshner wire in the required position. The actual device is instead based only on an aiming methodology resting on geometrical considerations. Previous knowledge of the position of such a point and direction, which can be given by a hole belonging to a plate or to an endo-medullary nail or can be part of the patient's bone structure, is not necessary. This is due to the use of fluoroscopy coupled to the localisation of two aiming planes on whose interception is placed the line of interest. A first instrument developed on this principle found limited clinical success due to the complexity of the first kinematic chain used in the aiming process and to human error. A new version has been designed and is at present under construction, which solves the kinematic problem through a careful choice of a series of constraints enabling the aiming process to be divided in sub processes, thus gradually controlling the final result.