Computer-assisted bone segment navigation.

Computer-assisted bone segment navigation is defined as the precise 3-D positioning of geometrically mapped and mathematically described skeletal segments. These bone segments are osteotomized, fractured or prefabricated according to a surgical plan. The high-precision positioning should have an accuracy of 1 mm or better. Segment navigation should be prepared with plain computed tomography (CT) without the implantation of registration markers before CT in order to reduce the number of CTs and operations. The Surgical Segment Navigator (SSN) was developed at the University of Regensburg with the support of Carl Zeiss. This is the first system to meet these criteria. The SSN is based on an infrared positioning device which is connected to a Hewlett Packard LD Pro Workstation. Infrared transmitters are connected to individual templates which are fixed to the bone segment by osteosynthesis screws. Intraoperative correlation between surgical planning and surgical site is achieved by use of a surface-pattern of the bone segment which fits equally well to the laboratory model and the conditions encountered in the patient. The concept of the SSN was submitted by Carl Zeiss as German Patent DE 19747427 A1 in 1997. The SSN system presented here has already been applied clinically and its precision has been evaluated by bone segment navigation in human cadavers.