Distal targeting of locking screws in intramedullary nails

Abstract

In a distal targeting system a hand-held location pad is integral with a guide section for a drill or similar surgical instrument, and has a plurality of magnetic field generators. A sensor, such as a wireless sensor, having a plurality of field transponders, is disposed in an orthopedic appliance, such as an intramedullary nail. The sensor is capable of detecting and discriminating the strength and direction of the different fields generated by the field generators. Control circuitry, preferably located in the location pad is responsive to a signal of the sensor, and determines the displacement and relative directions of an axis of the guide section, and a bore in the orthopedic appliance. A screen display and optional speaker in the location pad provide an operator-perceptible indication that enables the operator to adjust the position of the guide section so as to align its position and direction with the bore.

1 . A distal targeting system for determining the location and orientation of an instrument relative to a target, comprising: 
 a movable guide assembly for guiding an instrument toward a target;    a plurality of magnetic field generators that generate known distinguishable magnetic fields in response to drive signals, said magnetic field generators being operably associated with said guide assembly.    one or more magnetic field detectors disposed at known locations with respect to said target that generate magnetic field detector signals in response to said magnetic fields, said magnetic field detectors having known alignments with an axis of said target;    a signal processor responsive to said drive signals and said magnetic field detectors signals for producing three location coordinates of a point on said guide assembly and two orientation coordinates of an axis of said guide assembly; and    a display responsive to said signal processor that provides an indication of a location of said point with respect to said target and of an alignment between said axis of said guide assembly and said axis of said target.    
   
   
       2 . The distal targeting system according to  claim 1 , wherein said display is integral with said guide assembly.  
   
   
       3 . The distal targeting system according to  claim 1 , wherein said display comprises a ball-and-crosshairs indication.  
   
   
       4 . The distal targeting system according to  claim 1 , wherein said magnetic field detectors are wireless magnetic field detectors.  
   
   
       5 . The distal targeting system according to  claim 1 , further comprising: 
 a control unit; and    a plurality of external magnetic field generators responsive to control signals of said control unit, wherein external fields generated by said external magnetic field generators provide power to said magnetic field detectors.    
   
   
       6 . The distal targeting system according to  claim 5 , wherein said external fields further provide said drive signals to said magnetic field generators.  
   
   
       7 . The distal targeting system according to  claim 1 , wherein said indication comprises at least one of three location coordinates of a point on the guide assembly, and two orientation coordinates of an axis of the guide assembly.  
   
   
       8 . The distal targeting system according to  claim 1 , wherein said target comprises a hollow appliance, and said magnetic field detectors are insertable therein.  
   
   
       9 . The distal targeting system according to  claim 8 , wherein said hollow appliance comprises an intramedullary nail.  
   
   
       10 . The distal targeting system according to  claim 1 , wherein said magnetic field detectors are integral with said target.  
   
   
       11 . The distal targeting system according to  claim 10 , wherein said target comprises an intramedullary nail.  
   
   
       12 . The distal targeting system according to  claim 1 , further comprising a plurality of locating elements having location field detectors therein, said locating elements being disposed at known locations with respect to a fixed frame of reference, wherein said signal processor is responsive to said locating elements to determine a corrected indication of said location of said point.  
   
   
       13 . The distal targeting system according to  claim 1  further comprising a probe for cooperation with the target; and 
 whereas said plurality of magnetic field generators are connected to said probe.    
   
   
       14 . A distal targeting system for determining the location and orientation of an instrument relative to a target, comprising: 
 a movable guide assembly for guiding the instrument toward the target;    a plurality of permanent magnets;    one or more magnetic field detectors disposed at known locations with respect to said target that generate field detector signals in response to said fields, said magnetic field detectors having known alignments with an axis of said target;    a signal processor responsive to said drive signals and said field detector signals for producing three location coordinates of a point on said guide assembly and two orientation coordinates of an axis of said guide assembly; and    a location pad attached to said guide assembly and moveable therewith, responsive to said signal processor that provides a quantitative indication of a distance and a location of said point with respect to said target and of an alignment between said axis of said guide assembly and said axis of said target.    
   
   
       15 . The distal targeting system according to  claim 14 , wherein said magnetic field detectors are wireless magnetic field detectors.  
   
   
       16 . The distal targeting system according to  claim 14 , further comprising: 
 a control unit; and    a plurality of external field generators responsive to control signals of said control unit, wherein external fields generated by said external field generators provide power to said magnetic field detectors.    
   
   
       17 . The distal targeting system according to  claim 14 , wherein said quantitative indication comprises at least one of three location coordinates of a point on the guide assembly, and two orientation coordinates of an axis of the guide assembly.  
   
   
       18 . The distal targeting system according to  claim 14 , wherein said target comprises a hollow appliance, and said permanent magnets are insertable therein.  
   
   
       19 . The distal targeting system according to  claim 18 , wherein said appliance comprises an intramedullary nail.  
   
   
       20 . The distal targeting system according to  claim 14 , wherein said permanent magnets are integral with said target.  
   
   
       21 . The distal targeting system according to  claim 20 , wherein said target comprises an intramedullary nail.  
   
   
       22 . The distal targeting system according to  claim 14 , further comprising a plurality of locating elements having location field detectors therein, said locating elements being disposed at known locations with respect to a fixed frame of reference, wherein said signal processor is responsive to said locating elements to determine a corrected indication of said location of said point.  
   
   
       23 . The distal targeting system according to  claim 14:   further comprising a probe for cooperation with the target; and wherein said plurality of magnets are connected to said probe.    
   
   
       24 . A distal targeting system for determining the location and orientation of an instrument relative to a target, comprising: 
 a hand-held movable guide assembly for guiding the instrument toward the target;    a plurality of magnets;    a plurality of magnetic field detectors disposed at known locations with respect to said target that generate sensor signals in response to said fields, said sensors having known alignments with an axis of said target;    a signal processor disposed in said guide assembly responsive to said drive signals and said field detector signals for producing three location coordinates of a point on said guide assembly and two orientation coordinates of an axis of said guide assembly; and    a location pad disposed in said guide assembly, responsive to said signal processor that provides a quantitative indication of a distance and a location of said point with respect to said target and of an alignment between said axis of said guide assembly and said axis of said target, said location pad having a visual display for providing said quantitative indication.    
   
   
       25 . The distal targeting system according to  claim 24 , wherein said display is integral with said guide assembly.  
   
   
       26 . The distal targeting system according to  claim 24 , wherein said display comprises a ball-and-crosshairs indication.  
   
   
       27 . The distal targeting system according to  claim 24 , wherein said magnetic field detectors are wireless magnetic field detectors.  
   
   
       28 . The distal targeting system according to  claim 24 , wherein said visual display further provides a qualitative indication of a misalignment between said axis of said guide assembly and said axis of said target.  
   
   
       29 . The distal targeting system according to  claim 24 , further comprising: 
 a control unit; and    a plurality of external field generators responsive to control signals of said control unit, wherein external fields generated by said external field generators provide power to said magnetic field detectors.    
   
   
       30 . The distal targeting system according to  claim 29 , wherein said external fields further provide said drive signals to said magnets.  
   
   
       31 . The distal targeting system according to  claim 24 , wherein said quantitative indication comprises at least one of three location coordinates of a point on the guide assembly, and two orientation coordinates of an axis of the guide assembly.  
   
   
       32 . The distal targeting system according to  claim 24 , wherein said target comprises a hollow appliance, and said magnetic filed detectors are insertable therein.  
   
   
       33 . The distal targeting system according to  claim 32 , wherein said appliance comprises an intramedullary nail.  
   
   
       34 . The distal targeting system according to  claim 24 , wherein said magnets are integral with said target.  
   
   
       35 . The distal targeting system according to  claim 24 , wherein said target comprises an intramedullary nail.  
   
   
       36 . The distal targeting system according to  claim 24 , further comprising a plurality of locating elements having location field detectors therein, said locating elements being disposed at known locations with respect to a fixed frame of reference, wherein said signal processor is responsive to said locating elements to determine a corrected indication of said location of said point.  
   
   
       37 . The distal targeting system according to  claim 24:   further comprising a probe for cooperation with the target; and    wherein said plurality of magnets are connected to said probe.    
   
   
       38 . A system for treating fractures of a bone, comprising: 
 An implant for cooperation with the bone;    An instrument for cooperation with the bone and the implant.    a movable guide assembly for guiding the instrument toward the target; a plurality of permanent magnets;    one or more magnetic field detectors disposed at known locations with respect to said target that generate field detector signals in response to said fields, said magnetic field detectors having known alignments with an axis of said implant;    a signal processor disposed in said guide assembly responsive to said drive signals and said field detector signals having a first output responsive to a difference between a location of said implant and a location of said guide assembly and second output responsive to a difference between a direction of an axis of said guide assembly and a direction of said axis of said target; and    a display disposed in said guide assembly responsive to said signal processor that provides a qualitative indication of said first output and said second output.    
   
   
       39 . The system according to  claim 38 , wherein said display is integral with said guide assembly.  
   
   
       40 . The system according to  claim 38 , wherein said display comprises a ball-and-crosshairs indication.  
   
   
       41 . The system according to  claim 38 , wherein said magnetic field detectors are wireless magnetic field detectors.  
   
   
       42 . The system according to  claim 38 , further comprising: 
 a control unit; and    a plurality of external field generators responsive to control signals of said control unit, wherein external fields generated by said external field generators provide power to said magnetic field detectors.    
   
   
       43 . The system according to  claim 38 , wherein said implant comprises a hollow appliance, and said permanent magnets are insertable therein.  
   
   
       44 . The system according to  claim 43 , wherein said implant comprises an intramedullary nail.  
   
   
       45 . The system according to  claim 38 , wherein said permanent magnets are integral with said implant.  
   
   
       46 . The system according to  claim 45 , wherein said implant comprises an intramedullary nail.  
   
   
       47 . The system according to  claim 38 , further comprising a plurality of locating elements having location field detectors therein, said locating elements being disposed at known locations with respect to a fixed frame of reference, wherein said signal processor is responsive to said locating elements to determine a corrected indication of said location of said implant.  
   
   
       48 . The system according to  claim 38:   further comprising a probe for cooperation with said implant; and    wherein said plurality of permanent magnets are connected to said probe    
   
   
       49 . The system according to  claim 38  wherein said magnets comprise NB45 magnets.  
   
   
       50 . The system according to  claim 38 , wherein said implant comprises one of a drill and a screw.  
   
   
       51 . A system for treating fractures of a long bone, comprising: an intermedullary nail for cooperation with the bone; 
 an instrument for cooperation with the long bone and the nail.    a movable guide assembly for guiding the instrument toward the target;    a permanent magnet disposed at a known location with respect to said nail and having a known alignment with an axis of said nail;    a plurality of field detectors in said guide assembly producing field detector signals responsive to a field of said magnet;    a signal processor disposed in said guide assembly responsive to said field detector signals having outputs representative of a difference between a location of said nail and a location of said guide assembly and a difference between a direction of an axis of said guide assembly and a direction of said axis of said nail; and    a display disposed in said guide assembly responsive to said signal processor that provides a first indication of said difference between said location of said nailand a second indication of said difference between said direction of said axis of said guide assembly.    
   
   
       52 . The system according to  claim 51 , wherein said display is integral with said guide assembly.  
   
   
       53 . The system according to  claim 51 , wherein said first indication and said second indication comprise a ball-and-crosshairs display.  
   
   
       54 . The system according to  claim 51 , wherein said nail comprises a hollow appliance, and said magnet is insertable therein.  
   
   
       55 . The system according to  claim 51 , wherein said magnet is integral with said nail.  
   
   
       56 . The system according to  claim 51 , further comprising a plurality of locating elements having location field detectors therein, said locating elements being disposed at known locations with respect to a fixed frame of reference, wherein said signal processor is responsive to said locating elements to determine a corrected indication of said location of said nail.  
   
   
       57 . The system according to  claim 51:   further comprising a probe for cooperation with said nail; and    wherein said plurality of magnets are connected to said probe.    
   
   
       58 . The system according to  claim 51 , wherein said magnets comprise NB45 magnets.  
   
   
       59 . The system according to  claim 51 , wherein said instrument comprises one a drill and a screw.