Computer-assisted bone segment navigation

Computer-assisted bone segment navigation is defined as the precise 3-D pos itioning of geometrically mapped and mathematically described skeletal segm ents. These bone segments are osteotomized, fractured or prefabricated acco rding to a surgical plan. The high-precision positioning should have an acc uracy of 1 mm or better. Segment navigation should be prepared with plain computed tomography (CT) w ithout the implantation of registration markers before CT in order to reduc e the number of CTs and operations. The Surgical Segment Navigator (SSN) was developed :It the University of Re gensburg with the support of Carl Zeiss. This is the first system to meet t hese criteria. The SSN is based on an infrared positioning device which is connected to a Hewlett Packard LD Pro Workstation. Infrared transmitters ar e 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 1:he bone seg ment which fits equally well to the laboratory model and the conditions enc ountered in the patient. The concept of the SSN was submitted by Carl Zeiss as German Patent DE 19747427 Al in 1997. The SSN system presented here has already been applied clinically and its p recision has been evaluated by bone segment navigation in human cadavers.