Future minimally invasive neck surgery requires a navigation system adapted to the actual intra-operative bedding of the patient. The detection of the bedding-caused tissue shift is essential for a safe orientation for the surgeon new endoscopic operation procedures in neck surgery. It is essential to visualize the relation between important anatomic landmarks and operation instruments at any time. Within the scientific project SACAS we focus on developing an ultrasound supported navigation system based on preoperative imaging which considers the intra-operative tissue shift. A rotatable, flexible neck-model provides the basis for our analysis to evaluate the tissue shift and to invent the new navigation system for endoscopic neck surgery. The total registration error of the system was 2 mm.