Instrumentation for distal targeting of locking screws in intramedullary nails

Apparatus for concurrently displaying relative positions of first and second signal-sensing means with respect to first and second signal-emitting means, respectively, in order to effect alignment therewith, comprising:

• a screen with fixed reference lines relative to a target point;
• a first movable pointer displayed on said screen and having a screen position responsive to a distance between said first signal-sensing means and said first signal-emitting means, such that said first movable pointer coincides with said target point when said first signal-sensing means is in alignment with said first signal-emitting means;
• and
• a second movable pointer displayed on said screen and having a screen position responsive to a distance between said second signal-sensing means and said second signal-emitting means, such that said second movable pointer coincides with said target point when said second signal-sensing means is in alignment with said second signal-emitting means;
• wherein said first signal-emitting means and said second signal-emitting means are alternately activated with a predetermined frequency, such that said screen positions of said first and second movable pointers are independently produced.

A method for concurrently displaying relative positions of first and second signal-sensing means with respect to first and second signal-emitting means, respectively, in order to effect alignment therewith, comprising the following steps:

• providing a screen with fixed reference lines relative to a target point;
• producing a first movable pointer displayed on said screen and having a screen position responsive to a distance between said first signal-sensing means and said first signal-emitting means, such that said first movable pointer coincides with said target point when said first signal-sensing means is in alignment with said first signal-emitting means;
• and
• producing a second movable pointer displayed on said screen and having a screen position responsive to a distance between said second signal-sensing means and said second signal-emitting means, such that said second movable pointer coincides with said target point when said second signal-sensing means is in alignment with said second signal-emitting means;
• wherein said first signal-emitting means and said second signal-emitting means are alternately activated at a predetermined frequency, such that said screen positions of said first and second movable pointers are independently produced.

A device for locating a target point disposed at known axial and radial positions in a supporting structure and for drilling therethrough, comprising:

• a probe adapted to be mounted on said supporting structure;
• a proximal electromagnetic drive means disposed at a predetermined fixed location within said probe and capable of producing a proximal magnetic flux having a proximal magnetic axis;
• a distal electromagnetic drive means disposed at a predetermined fixed location within said probe and capable of producing a distal magnetic flux having a distal magnetic axis, said proximal and distal electromagnetic drive means being alternately operative;
• axial positioning means for securely placing and retaining said distal magnetic axis at a predetermined axial distance from the target point in said supporting structure;
• radial positioning means for securely placing and retaining said proximal magnetic axis at a predetermined angular relationship with said target point;
• first electromagnetic sensor means for sensing the distal magnetic flux produced by said distal electromagnetic drive means and for emitting a first output signal corresponding thereto, such that the first output signal is zero when said first electromagnetic sensor means is in first predetermined alignment with said distal magnetic axis;
• second electromagnetic sensor means for sensing the proximal magnetic flux produced by said proximal electromagnetic drive means and for emitting a second output signal corresponding thereto, such that the second output signal is zero when said second electromagnetic sensor means is in second predetermined alignment with said proximal magnetic axis;
• display means connected to said first and second electromagnetic sensor means for converting said first and second outputs into visual signals enabling a user to change the position of said first and second electromagnetic sensor means so as to cause said first and second outputs to be zero;
• and
• drilling means for drilling a hole through said target point;
• said drilling means having a main axis disposed in parallel to said first predetermined alignment at an axial distance from said first electromagnetic sensor means equal to said predetermined axial distance, and said main axis also being disposed in parallel to said second predetermined alignment at an angle with said second electromagnetic sensor means equal to said predetermined angular relationship with said target point;
• whereby said probe may be mounted onto said supporting structure and securely retained with said distal magnetic axis at said predetermined axial distance from, and with said proximal magnetic axis at said predetermined angular relationship with, the target point;
• said first and second electromagnetic sensor means may be aligned with said distal and proximal magnetic axes, respectively, by moving said electromagnetic sensor means until said first and second outputs are zero;
• and said drilling means may then be used for drilling through said target point.