The invention relates to a medical instrumentation with a navigation system which comprises an optical detection unit comprising a camera, and a data processing unit coupled to the detection unit, with a stabilization element of a surgical fixation system and with a medical marking device which is held in a defined spatial arrangement on or is comprised by or formed by the stabilization element, the location and orientation of the marking device in space being determinable with the navigation system, it being possible for at least two images of the stabilization element and the marking device to be taken from a different orientation by means of the detection unit and for the shape of the stabilization element to be determined by the data processing unit on the basis of the two or more images. The invention also relates to a method for determining the shape of a surgical stabilization element.
