Method and apparatus for finding the position of a mechanical axis of a limb
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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.
111 Citations
34 Claims
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1-20. -20. (canceled)
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21. A method for implanting a prosthesis on a limb, comprising:
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calculating the position of a mechanical axis extending longitudinally through a limb without piercing a skin on the limb beyond a first exposed end of the limb, the limb being freely movable and rotatably supported in a body via a movable center of rotation at a second end of the limb;
aligning a cutting jig on the limb with respect to the calculated mechanical axis;
attaching the cutting jig to the first end of the limb, the cutting jig guiding a cutting device thereon to resect the first exposed end of the limb; and
implanting a prosthesis on the limb at the resected first end. - View Dependent Claims (22, 23, 24, 25, 26)
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27. A method for implanting a knee prosthesis, comprising:
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calculating the position of a mechanical axis extending longitudinally through a femur without piercing a skin on the femur above a first exposed end of the femur, the femur being freely movable and rotatably supported in a hip via a movable center of rotation at a second end of the femur;
aligning a cutting jig on the first end of the femur with respect to the calculated mechanical axis, the cutting jig guiding a cutting device thereon;
operating the cutting device to resect the first exposed end of the femur; and
implanting a prosthesis on the resected first end of the femur. - View Dependent Claims (28, 29, 30)
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31. A system for finding the position of a mechanical axis of a limb that is rotatably supported via a movable center of rotation comprising:
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a camera arrangement comprising at least two cameras spaced apart from one another by a fixed distance, each of the at least two cameras configured to receive a signal from at least one transmitter;
at least two multi-point indicators, each of which comprises a measurement-point field with several measurement points, the multi-point indicators configured to detect at least one measurement-point coordinate set, each measurement-point coordinate set including several measurement-point coordinates, one of the at least two multi-point indicators attached proximal a second end of the limb and configured to provide 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;
an evaluation unit configured to evaluate the at least one measurement-point coordinate set provided by the at least two multi-point indicators and detected by the camera arrangement using an iterative procedure to identify the mechanical axis of the limb extending through the first end of the limb without piercing a skin on the limb beyond a second end of the limb; and
a process control device configured to control sequential recording and storage of the measurement-point-coordinate sets obtained for each rotational position of the limb. - View Dependent Claims (32, 33, 34)
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Specification