Abstract: A method and apparatus for cross checking points palpated with a localization device. Points corresponding to the palpated points are obtained from a preoperative image of an object such as an X-Ray of a tibia bone. During a surgical procedure, the accuracy of palpated points are determined based on the palpated points and corresponding points obtained from the preoperative image. If a palpated point is inaccurate, an indicator is generated to indicate the inaccuracy of the palpated point.

Abstract: A calibration method and also a calibration device are proposed to enable a spatial position and/or orientation of a surgical referencing unit of a surgical navigation system fitted with at least one inertial sensor to be specified in relation to a spatial coordinate system.

Abstract: A calibration method and also a calibration device are proposed to enable a spatial position and/or orientation of a surgical referencing unit of a surgical navigation system fitted with at least one inertial sensor to be specified in relation to a spatial coordinate system.

Abstract: In order to improve the precision of determining the articulation point with a method for determining an articulation point of two bones, which are connected by a joint and are connected to pivot relative to one another around at least two non-parallel rotational axes, wherein the two bones are moved relative to one another, measured values describing the movement of a point of a bone in a reference system of the other bone are recorded, a rotational axis describing the movement as rotation is determined from these measured values for a plurality of parts of the path or respectively for one of a plurality of consecutively recorded paths, it is proposed that the deviation in orientation is calculated for the differently oriented rotational axes determined in this way and from the differently oriented rotational axes an articulation point is calculated only when the deviation in orientation of the rotational axes exceeds a specific value.

Abstract: To enable the contour of a recess in a piece of material, which is worked into the material by means of a tool, in particular in a piece of bone, to also be determined without a direct view of the machining region with a method for determining this contour, it is proposed that the position of the piece of material in space is established by a navigation system, that the position of the tool in space is established by a navigation system, that the respective position of the tool in relation to the piece of material is determined from the position data obtained in this manner, that during the machining of the piece of material with the tool, the relative positions of the tool in relation to the piece of material are stored and that the prepared contour on the piece of material is determined from extreme values of these relative positions with respect to a fixed reference position of the piece of material. A device for performing this method is also specified.