[Original developments of navigation techniques in traumatology]

This article presents an original method for long objects modeling and two navigation applications in trauma surgery. Both concern long bone fracture treatment. Our modeling method requires only two x-ray views. The projection cones of the object are determined and their intersection is computed, providing an approached 30 model, which can be improved by adding a priori knowledge or other information. The first application concerns the control of diaphyseal fracture reduction treated by external fixation. Reference frames are fixed to the bone fragments and tracked by a 3D optical localizer, allowing the computation of their relative position. Approached 3D models of the fragments are displayed in real time according to the manipulation effected by the surgeon. The principal axes of the fragments, very useful for the fracture reduction, are also displayed. The alignment of the bone fragments is quantified by parameters provided in real time during the reduction. The second application concerns the distal locking of intra-medullary nails. A 3D model of the nail and its locking holes is built from two calibrated fluoroscopic views. The nail and the surgical tool are tracked thanks to reference frames fixed to each of them. A 3D view of these two elements is displayed in real time, guiding the surgeon in the difficult task of distal targeting. Experiments and results are presented for both applications. These techniques provide real 3D models to the surgeon during the operation, allowing precise guidance of the surgical gesture and considerable reduction of the irradiation to the patient and the surgical team.