Method and apparatus for finding the position of a mechanical axis of a limb

An arrangement for finding the position of a mechanical axis of a limb that is rotatably supported by its first end via a movable center of rotation comprising:

• a camera arrangement with at least two cameras spaced apart from one another by a fixed distance for the spatially determined reception of transmitter signals
• at least two multi-point indicators, each of which comprises a measurement-point field with several measurement points, to detect several measurement-point coordinates (P11-Pn−1), such that a first multi-point indicator is constructed as a movable feeler for the tactile sampling of bony reference points in order to measure their coordinates, and
• an evaluation unit for evaluating the measurement-point coordinate sets provided by the multi-point indicator and detected by the camera arrangement, in order to identify the mechanical axis of the limb extending through the first end of the limb without piercing a skin on the limb above a second end of the limb, and such that a second multi-point indicator is rigidly attached in the vicinity of said second end of the limb, in such a way that it provides measurement-point-coordinate sets for several rotational positions of the limb, all of which lie on spherical surfaces positioned around the associated site of the center of the rotation, and
• a process control means to control sequential recording and storage of the measurement-point-coordinate sets obtained in the individual rotational positions of the limb, and subsequent processing thereof, according to a prespecified processing thereof, according to a prespecified processing sequence, and wherein the evaluation device comprises means for performing an iteration procedure, to specify a site of the center of rotation, for calculating the position of a mechanical axis on the basis of the site of the center of rotation, and for calculating a second point at the second end of the limb, specified on the basis of bony reference points on the limb.