Computer assisted surgery has rapidly developed over the last decade, essentially due to the development of navigation and 3D virtual surgical planning and image fusion technologies. The recent introduction of intra-operative cone-beam CT scan (CBCT), which integrates flat panel technology, allows for high resolution bone imaging, the quality and accuracy of which is similar to the one obtained by conventional spiral CT scan. The combination of these two technologies in a "hybrid" operating unit enables the convergence of the pre-, intra- and post-operative steps in a linear computer-assisted processing chain, which optimises surgery accuracy, predictability and patient outcomes while potentially reducing costs, operating times and need for further surgical revision. TECHNICAL NOTE: The "hybrid" unit includes: 1) the operating room (65 m(2)) equipped with horizontal laminar-flow, a mobile monoplane ceiling suspended C-arm CBCT scan system with a flat panel detector, a wireless navigation system, and an interactive wall-mount touch screen 2) the control room (18 m(2)) separated from the operating room by an X-ray lead protective glass window, including two separate computer workstations for 3D image integration and processing 3) the scrub room (17 m(2)) with two separate stainless steel surgical wash-basins. The intra-operative protocol includes the following steps: 1) elaboration of the patient specific pre-operative computed planning and simulation based on pre-operatively and/or intra-operatively acquired patient images 2) intra-operative navigational guidance setting 3) surgical procedure 4) intra-operative 3D CT imaging 5) suture.