Method and apparatus for finding the position of a mechanical axis of a limb
First Claim
1. A method of finding the position of a mechanical axis running in the longitudinal direction through a limb, the limb rotatably supported by a first end via a movable and inaccessible center of rotation for the mechanical determination of coordinates, comprising:
- providing an optical coordinate-measurement device with at least one multi-point indicator to signal measurement-point coordinates in a rotational position of the limb;
rigidly attaching said multi point indicator near a second end of the limb;
detecting several measurement-point coordinates (P11, P21, P31, Pn1) per rotational position of the limb;
recording said measurement-point coordinates;
selecting from measurement-point-coordinate sets (P11-Pn1, P12-Pn2, P1m-Pnm) at least one group;
assigning said at least one group to a same site of the center of rotation; and
calculating the position of the first end of the limb and a mechanical axis running through the first and second ends using the measurement-point-coordinate sets (P11-Pn1, P12-Pn2, P1m-Pnm) assigned to said site of the center of rotation without piercing a skin of the limb above said second end.
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Accused Products
Abstract
A method of finding the position of a mechanical axis running in the longitudinal direction through a limb that is rotatably supported by its first end in a center of rotation that is not fixed and is not accessible for the mechanical determination of coordinates, by means of an optical coordinate-measurement device with an indicator to detect measurement-point coordinates in one rotational position of the limb, such that, for each rotational position, a multi-point indicator rigidly attached near the second end of the limb signals several measurement-point coordinates, and, from the sets of measurement-point coordinates detected in a plurality of rotational positions, at least one group is selected that can be assigned to the same site of the center of rotation, and the measurement-point-coordinate sets assigned to this site of the center of rotation are used to calculate the mechanical axis.
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Citations
20 Claims
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1. A method of finding the position of a mechanical axis running in the longitudinal direction through a limb, the limb rotatably supported by a first end via a movable and inaccessible center of rotation for the mechanical determination of coordinates, comprising:
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providing an optical coordinate-measurement device with at least one multi-point indicator to signal measurement-point coordinates in a rotational position of the limb;
rigidly attaching said multi point indicator near a second end of the limb;
detecting several measurement-point coordinates (P11, P21, P31, Pn1) per rotational position of the limb;
recording said measurement-point coordinates;
selecting from measurement-point-coordinate sets (P11-Pn1, P12-Pn2, P1m-Pnm) at least one group;
assigning said at least one group to a same site of the center of rotation; and
calculating the position of the first end of the limb and a mechanical axis running through the first and second ends using the measurement-point-coordinate sets (P11-Pn1, P12-Pn2, P1m-Pnm) assigned to said site of the center of rotation without piercing a skin of the limb above said second end. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 19)
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11. 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:
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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, andan 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. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 20)
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Specification