ILUMARK Navigation Markers are sterile, single-use retro-reflective markers for image-guided surgery systems using passive tracking technology. They are available in both TWIST and SNAP on. Such systems are used to support surgical procedures in Neurosurgery, ENT Sinus Surgery, Cranio-Maxillofacial Surgery, Spine Surgery, Trauma Surgery and in Orthopedic Surgery for Total Hip and Knee Replacements. In surgery, the marker spheres are attached to the surgical instruments. Infrared cameras are tracking the reflective marker spheres and the coordinates in space are localized. The diagnostic patient images are then referenced to the real patient. Now, the surgeon can navigate his surgical instruments on a computer screen. This makes surgical procedures less invasive and more precise. The reflective marker spheres play an essential and integral role in this system.