Abstract: An adaptor for receiving a navigated structure, wherein the navigated structure is at least a part of a medical object which carries an object reference, and for being connected to a registration tool in order to register the navigated structure in a medical navigation system, the adaptor comprising at least two adaptor parts which, in an assembled state, form a structure receiving recess in the shape of the navigated structure and an adaptor coupling part for connecting the adaptor to the registration tool in a predetermined relative position.