AUTOMATIC FRACTURE REDUCTION WITH A COMPUTER-CONTROLLED EXTERNAL FIXATOR

The reduction of fractures by means of an Ilizarov's fixator is obtain ed by successively shortening or lengthening the rods. This entails th at all reduction operations of the fracture stumps be performed with a series of empirical attempts, requiring great experience and manual d exterity in the surgeon. Moreover this process involves a long exposur e of both physician and patient to potentially harmful radiation due t o the continuous checking of the intermediate positions on the X-ray i mage intensifier. In order to overcome these limits a new device has b een conceived, based on the application of three stepper-motors on thr ee rods. Its basic principle is functionally very similar to Ilizarov' s prototype. The relative motions between the two frames are carried o ut by controlling the three actuators with a computer, which processes the number of required steps on the basis of an algorithm, starting f rom a few inputs supplied by the surgeon. This article illustrates the functional kinematic study necessary for the complete automation of t he reduction process. Also considered is the complex problem of the re duction trajectory definition, intended as a sequence of configuration s of partial correction, obtained by formalizing in geometrical terms the empirical criterial followed by the orthopaedic surgeon in reducin g fractures. Such a sequence is intended to be a suggestion for the su rgeon who can visualize and possibly interact with the system to deter mine a trajectory harmless for the soft tissues surrounding the bone.