Apparatus and Methods for Using an Electromagnetic Transponder in Orthopedic Procedures

Abstract

Electromagnetic transponders as markers are used to localize and guide orthopedic procedures including: knee replacement, hip replacement, shoulder replacement, damaged bone reconstruction, and spine surgery, and more particularly, to guide orthopedic surgical navigation and alignment techniques and instruments. For example, the marker could further be used in any number of guides or templates that attach to the bony anatomy, such as a surgical guide, cutting guide, cutting jig, resection block and/or resurfacing guide. Further, the marker could be incorporated into an existing intramedullary guide rod for a femur and an extramedullary guide rod for a tibia in a knee replacement surgery; or into an external surgical guide system, or the marker could eliminate the need for an external template altogether. According to yet another anticipated use of the tracking system, the marker could be used in conjunction with or replace an optical alignment system.

1 . An electromagnetic marker for use in orthopedic procedures, comprising:
 a template of known mechanical dimensions temporarily used during surgery; and   a marker fixed to the template in a substantially fixed relationship.   
     
     
         2 . An electromagnetic marker for use in orthopedic procedures, comprising:
 a prosthetic device configured for implantation in a patient; and   a marker fixed to the prosthetic device in a substantially fixed relationship.   
     
     
         3 . An electromagnetic marker for use in orthopedic procedures, comprising:
 a bone screw or similar device; and   a marker fixed to the bone screw or similar device in a substantially fixed relationship.   
     
     
         4 . The apparatus of  claim 1  wherein the marker comprises a wireless transponder configured to wirelessly transmit a location signal in response to a wirelessly transmitted excitation energy. 
     
     
         5 . The apparatus of  claim 1  wherein the marker comprises a casing affixed in or on the template and a magnetic transponder in the casing, and wherein the magnetic transponder comprises a coil and a capacitor coupled to the coil. 
     
     
         6 . The apparatus of  claim 1  wherein the template comprises a cutting guide, and wherein the apparatus further comprises a plurality of markers attached to the cutting guide. 
     
     
         7 . The apparatus of  claim 6  wherein the markers comprise wireless transponders configured to wirelessly transmit location signals in response to wirelessly transmitted excitation energy. 
     
     
         8 . The apparatus of  claim 6  wherein the markers comprise a first magnetic transponder having a first resonant frequency and a second magnetic transponder having a second resonant frequency different than the first resonant frequency. 
     
     
         9 . The apparatus of  claim 7  wherein the markers comprise radiopaque elements. 
     
     
         10 . The apparatus of  claim 7  wherein the markers comprise magnetic transponders and/or radiographic fiducials. 
     
     
         11 . The apparatus of  claim 10  wherein the transponders and the fiducials are in a fixed relationship and/or orientation to one another. 
     
     
         12 . The apparatus of  claim 4  wherein the transponder comprises an alternating magnetic circuit having a ferrite core and a coil with a plurality of windings around the ferrite core. 
     
     
         13 . The apparatus of  claim 4  wherein the transponder comprises a ferrite core and a coil around the ferrite core, and wherein the marker further comprises a capsule encasing the transponder, the capsule having a longitudinal axis and a cross-sectional dimension normal to the longitudinal axis of not greater than 2 mm. 
     
     
         14 . The apparatus of  claim 2  wherein the prosthetic device further comprises a first marker in a first portion of the member and a second marker in a second portion of the member spaced apart from the first marker, wherein the first and the second markers are orthogonally oriented with respect to each other. 
     
     
         15 . The apparatus of  claim 2  wherein the marker comprises an alternating magnetic circuit and wherein the marker has a radiographic centroid and the alternating magnetic circuit has a magnetic centroid at least approximately coincident with the radiographic centroid. 
     
     
         16 . A system for localizing and/or tracking a device contained in a bony anatomy of a patient, comprising:
 a transponder affixed to the bone of a patient, wherein the transponder has a circuit configured to be energized by a wirelessly transmitted pulsed magnetic field and to wirelessly transmit a pulsed magnetic location signal in response to the pulsed magnetic field;   an alignment device for aligning the bone of a patient during localizing and/or tracking of the transponder; and   an excitation source comprising an energy storage device, a source coil, and a switching network coupled to the energy storage device and the source coil, the source coil being configured to wirelessly transmit the pulsed magnetic field to energize the transponder, and the switching network being configured to alternately transfer (a) stored energy from the energy storage device to the source coil and (b) energy in the source coil back to the energy storage device.   
     
     
         17 . The system of  claim 16  wherein the switching network comprises an H-bridge switch. 
     
     
         18 . The system of  claim 16  wherein the switching network is configured to have a first on position in which the stored energy is transferred from the energy storage device to the source coil and a second on position in which energy in the source coil is transferred back to the energy storage device. 
     
     
         19 . The system of  claim 18  wherein the first on position has a first polarity and the second on position has a second polarity opposite the first polarity. 
     
     
         20 . The system of  claim 16  wherein the source coil comprises an array having a plurality of coplanar source coils. 
     
     
         21 . The system of  claim 20  wherein the switching network is configured to selectively energize the coplanar source coils to change a spatial configuration of the pulsed magnetic field. 
     
     
         22 . The system of  claim 16  wherein the transponder comprises an alternating magnetic circuit having a ferrite core and a coil with a plurality of windings around the ferrite core. 
     
     
         23 . The system of  claim 16  wherein the transponder is not electrically coupled to external leads outside the body. 
     
     
         24 . A system for tracking a body contained in an implanted prosthesis of a human, comprising:
 a prosthesis configured to be received in a cavity of a human and a magnetic transponder contained in or on the body, wherein the transponder has a circuit configured to be energized by a wirelessly transmitted pulsed magnetic field and to wirelessly transmit a pulsed magnetic location signal in response to the pulsed magnetic field; and   a sensor assembly comprising a support member and a plurality of field sensors carried by the support member configured to sense the pulsed magnetic location signal from the transponder.   
     
     
         25 . The system of  claim 24  wherein the field sensors are responsive only to field components of the pulsed magnetic location signal normal to individual field sensors. 
     
     
         26 . The system of  claim 24  wherein the field sensors are arranged in an array occupying an area having a maximum dimension of approximately 100% to 300% of a predetermined sensing distance between the marker and the sensing array. 
     
     
         27 . The system of  claim 24  wherein the transponder comprises an alternating magnetic circuit having a ferrite core and a coil with a plurality of windings around the ferrite core. 
     
     
         28 . A method for using implanted an electromagnetic transponder to localize bone components, comprising:
 implanting one or more electromagnetic transponder pre-operatively;   localizing bone components using one or more electromagnetic transponders pre-operatively; and   localizing bone components using one or more electromagnetic transponders during surgery electromagnetically.   
     
     
         29 . The method of  claim 28  further comprising:
 localizating bone components using one or more electromagnetic transponders following surgery electromagnetically.   
     
     
         30 . A method for using implanted an electromagnetic transponder to localize a prosthesis relative to bony anatomy during surgery, comprising:
 localizing bone components using one or more electromagnetic transponders pre-operatively; and   localizing bone components using one or more electromagnetic transponders during surgery.   
     
     
         31 . A method for using an electromagnetic transponder to localize a cutting guide during surgery, comprising:
 localizing the cutting guide using one or more electromagnetic transponders pre-operatively; and   localizing the cutting guide using one or more electromagnetic transponders during surgery electromagnetically.   
     
     
         32 . The method of  claim 28  wherein localizing the marker comprises (a) wirelessly delivering a pulsed magnetic field to energize the marker, (b) wirelessly transmitting a pulsed location signal from the marker to a location outside the patient, (c) sensing the pulsed location signal at a sensor located outside the patient, and (d) periodically calculating a three-dimensional location of the marker in a reference frame. 
     
     
         33 . The method of  claim 32  further comprising providing an output of the location of the marker in the reference frame at least every t f  second and within t l  second from sensing the pulsed location signal, wherein t f  and t l  are not greater than 1 second. 
     
     
         34 . The method of  claim 33  wherein t f  and t l  are from approximately 10 ms to approximately 500 ms. 
     
     
         35 . The method of  claim 32  wherein providing an output of the location of the marker further comprises referencing the three-dimensional location of the marker with an image of the marker relative to a target. 
     
     
         36 . The method of  claim 32  wherein localizing the marker comprises determining whether the marker has moved from a desired location. 
     
     
         37 . The method of  claim 32  wherein localizing the marker occurs during surgery.