title: State-of-the-art in orthopaedic surgical navigation with a focus on medical image modalities
abstract: This paper presents a review of surgical navigation systems in orthopaedics and categorizes these systems according to the image modalities that are used for the visualization of surgical action. Medical images used to be an essential part of surgical education and documentation as well as diagnosis and operation planning over many years. With the recent introduction of navigation techniques in orthopaedic surgery, a new field of application has been opened. Today surgical navigation systems - also known as image-guided surgery systems - are available for various applications in orthopaedic surgery. They visualize the position and orientation of surgical instruments as graphical overlays onto a medical image of the operated anatomy on a computer monitor. Preoperative image data such as computed tomography scans or intra operatively generated images (for example, ultrasonic, endoscopic or fluoroscopic images) are suitable for this purpose. A new category of medical images termed 'surgeon-defined anatomy' has been developed that exclusively relies upon the usage of navigation technology. Points on the anatomy are digitized interactively by the surgeon and are used to build up an abstract geometrical model of the bony structures to be operated on. This technique may be used when no other image data is available or appropriate for a given application
keyphrases: orthopaedic surgical navigation medical image modalities surgical education image-guided surgery systems surgical instruments graphical overlays computer monitor computed tomography scans intra operatively generated images surgeon-defined anatomy abstract geometrical model bony structures surgical action visualization medical image processing image registration