Augmented Reality in Orthopedic Surgery

The medical images that we use for our interventions are mostly two-dimensional (2D) images that serve us intraoperatively to identify anatomical structures. The major disadvantage of this approach is the lack of a spatial relationship between the patient and its own medical images. To ensure this relationship, it is therefore necessary to repeatedly perform an intraoperative mental registration. Augmented reality is a display technique that provides assistance and guidance during navigation steps by allowing inlay and combining additional information into the surrounding real world. This technique was introduced in France in the late 1980s (neuro-navigation) and extended to other specialties, including orthopedics in the 1990s, thanks to some pioneering navigation teams. Typically, the additional information comes from images provided by a computer from a variety of sources (MRI, CT, Radioisotope scanning, Ultrasound, C-arm X rays) or a video camera. In its second step of development, augmented reality provides the surgeon with a direct and real time spatial relationship between medical images and the operated anatomical region of the patient by using sophisticated registration process. The image is thus projected onto the patient and appears in the same orientation and in the same position as the corresponding anatomical structure. Some clinical applications in spine surgery or traumatology (pedicle screwing, peripheral osteosyntheses and distal locking of intra- medullary nails) can already be noted. However, there are many questions to be solved for using augmented reality in orthopedic surgery: in which situations do we need information (preoperative planning, intraoperative navigation or postoperative evaluation)? What information is really useful? What accuracy level do we need? How to properly display this information? Universal application of augmented reality in orthopedic surgery does not exist at present and future developments require a close collaboration between surgeons and scientists.