The reduction offiactures by means of an Ilr&rov 'sfiator is obtained by successively shortening or lengthening the rods. This entails that all reduction operations of the fracture stumps be ptiormed with a series of empirical attempts, requiring great experience and manual dexterity in the surgeon. Moreover thzs process involves a long exposure of both physician andpatient to potentially harmful radiation due to the continuous checking of the intermediate positions on the X-ray image intenstfier. In order to overcome these limits a new device has been conceived, based on the application of three stepper-motors on three rods. Its basic ptinciple is finctionally very similar to Ilt&rov's prototype. The relative motions between the two frames are carried out by controlling the three actuators with a computer, which processes the number of required steps on the basis of an algorithm, startingfiom a few inputs supplied by the surgeon. This article illustrates t& finctional kinematic study necessary for the complete automation of the reduction process. Also consio!ered is the complex problem of the reduction trajectory de+ition, intended as a sequence of con&rations of partial correction, obtained by fownaliring in geometrical terms the empirical criteria followed by the orthopacdic surgeon in reducingfiactures. Such a sequence is intended to be a suggestion for the surgeon who can vbual& and possibly interact with the system to determine a trajectory harmless for the sojt tissues surrounding the bone.