Process and device for the preoperative determination of the positioning data of endoprosthetic parts

A process for the preoperative determination of positioning data of endoprosthetic parts of a central joint relative to a first set of two bones forming the central joint, comprising the steps of:

• moving, relative to one another, a second set of two bones coming together at a first outer joint and having a first bone from the first set of bones, located at an end of the first bone facing away from the central joint, to determine a first articular point for said first bone;
• determining a second articular point in the area of the central joint for said first bone;
• determining a first characteristic direction for said first bone by way of a straight-line connection of the first and second articular points;
• and
• determining an orientation of the endoprosthetic parts relative to the first characteristic direction.

A device for the preoperative determination of positioning data of endoprosthetic parts of a central joint relative to a first set of two bones forming the central joint, comprising:

• at least one marking element securable to each bone from a second set of two bones forming a first outer joint, said second set of two bones having a first bone from the first set of two bones;
• a measuring device for determining the position of the marking elements in space;
• a data processing system adapted to receive signals corresponding to positioning data of the marking elements from the measuring device;
• and
• said data processing system is responsive to the signals during movement of the second set of bones about the first outer joint to determine the point of greatest invariance at the first outer joint as a first articular point;
• wherein:
• a second articular point is determined in the area of the central joint for said first bone;
• and
• a first characteristic direction is determined for the first bone from the position of the first articular point and the second articular point.