Position sensing system for orthopedic applications

A surgical tracking system for use by a surgeon, comprising:

• a wireless position sensor, which is adapted to be implanted in a bone of a subject, and generates and transmits sensor signals responsive to externally-applied magnetic fields within a working volume of the tracking system, the sensor signals indicative of coordinates of the position sensor within the bone;
• a plurality of field generator coils, which are adapted to generate the magnetic fields so as to define the working volume, the location and orientation of the plurality of field generator coils being known relative to a given reference frame;
• a reference structure, to which the field generator coils are fixed in predetermined locations, and which is movable relative to the subject by the surgeon during surgery, the reference structure and the field generator coils being raised, lowered, tilted or shifted by the surgeon during surgery in order to shift the working volume so as to intercept the bone;
• and
• a system controller, which is coupled to receive and process the sensor signals so as to determine the coordinates of the position sensor within the bone and within the given reference frame.