The Surgical Segment Navigator (SSN) is a computer-based system for use in surgical navigation. It is integrated into a common platform

Platform (computing)

A computing platform includes some sort of hardware architecture and a software framework , where the combination allows software, particularly application software, to run...

, together with the Surgical Tool Navigator (STN), the Surgical Microscope Navigator (SMN) and the 6DOF

Degrees of freedom (engineering)

In mechanics, degrees of freedom are the set of independent displacements and/or rotations that specify completely the displaced or deformed position and orientation of the body or system...

 Manipulator (MKM), developed by Carl Zeiss.

SSN

The SSN has been developed as a computer system for bone segment navigation

Bone segment navigation

Bone segment navigation is a surgical method used in the field to find the anatomical position of displaced bone fragments in fractures, allowing a good fixation by osteosynthesis. It has been developed for the first time in oral and maxillofacial surgery....

 in oral and maxillofacial surgery

Oral and maxillofacial surgery

Oral and maxillofacial surgery is surgery to correct a wide spectrum of diseases, injuries and defects in the head, neck, face, jaws and the hard and soft tissues of the oral and maxillofacial region. It is an internationally recognized surgical specialty...

. It allows a very precise repositioning of bone fragments, with the advent of preoperative simulation and surgical planning

Surgical planning

The surgical planning is the preoperative method of pre-visualising a surgical intervention, in order to predefine the surgical steps and furthermore the bone segment navigation in the context of computer assisted surgery....

.The system has been developed since 1997 at the University of Regensburg, Germany

University of Regensburg

The University of Regensburg is a public research university located in the medieval city of Regensburg, Bavaria, a city that is listed as a UNESCO World Heritage Site. The university was founded on July 18, 1962 by the Landtag of Bavaria as the fourth full-fledged university in Bavaria...

, with the support of the Carl Zeiss Company. Its principle is based on an infrared localisation system, composed of an infrared

Infrared

Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

 camera and at least three infrared transmitters attached to each bony fragment. The SSN is mainly used in orthognatic surgery (surgical correction of dysgnathia), but also for the surgical reconstruction of the orbit

Orbit

In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...

, or other surgical interventions to the midface.

SSN++

Since 2001, at the University of Heidelberg, Germany, the SSN++ has been developed, a markerless-registration

Patient registration

Patient registration is the concept and set of methods needed to correlate the reference position of a virtual 3D dataset gathered by computer medical imaging with the reference position of the patient...

 navigation system, based on a native (=markerless) CT

Computed tomography

X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...

 or MRI. In this case, the patient registration

Patient registration

Patient registration is the concept and set of methods needed to correlate the reference position of a virtual 3D dataset gathered by computer medical imaging with the reference position of the patient...

 is obtained on the operating table, using a surface scanner. The SSN++ corelates the surface scan data (gathered on the operating table) with the skin surface reconstruction from the dataset obtained preoperatively by CT

Computed tomography

X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...

 or MRI. This principle complies with the terrain contour matching

TERCOM

Terrain Contour Matching, or TERCOM, is a navigation system used primarily by cruise missiles. It uses a pre-recorded contour map of the terrain that is compared to measurements made during flight by an on-board radar altimeter. A TERCOM system considerably increases the accuracy of a missile...

 principle described for flying objects. The advantage of the new method is that the registration of the patient's position

Patient registration

Patient registration is the concept and set of methods needed to correlate the reference position of a virtual 3D dataset gathered by computer medical imaging with the reference position of the patient...

becomes a simple automated procedure; on the other hand, the radiation load for the patient is reduced, compared to the method using markers.