Instrumentation for distal targeting of locking screws in intramedullary nails

• US 5,411,503 A
• Filed: 06/18/1993
• Issued: 05/02/1995
• Est. Priority Date: 06/18/1993
• Status: Expired due to Fees

• Current Assignee: Bradley A. Hollstien, David S. Hollstien, Roy B. Hollstien, Steven B. Hollstien
• Original Assignee: Bradley A. Hollstien, David S. Hollstien, Roy B. Hollstien, Steven B. Hollstien
• Inventors: Hollstien, David S., Hollstien, Roy B., Hollstien, Bradley A., Hollstien, Steven B.
• Primary Examiner(s): Brown, Michael A.
• Application Number:
  US08/080,345
• Time in Patent Office: 683 Days
• Field of Search: 606/86, 606/87, 606/88, 606/96, 606/97, 606/98, 606/130, 378/162, 378/163, 378/205, 33/286, 33/262, 33/263, 33/334
• US Class Current: 606/86.00R
• CPC Class Codes: A61B 17/1707 using electromagnetic effects, e.g. with magnet and external sensors
• CPC Class Codes: A61B 17/1725 for applying transverse screws or pins through intramedullary nails or pins
• CPC Class Codes: A61B 2017/00039 Electric or electromagnetic phenomena other than conductivity, e.g. capacity, inductivity, Hall effect
• CPC Class Codes: A61B 2090/3958 emitting a signal

Abstract

The instrumentation is used by orthopaedic surgeons for accurate and rapid placement of distal locking screws in intramedullary nails. A probe inserted into the intramedullary nail positions two electromagnetic drive coils with their magnetic axes parallel to and at a fixed offset from the axis of a transverse hole to be drilled. The drive coils generate alternating magnetic fields over intermittent and non-overlapping time intervals in a manner that provides independent sources of positional information. A hand-held guide, containing a drill bushing and four receiving coils with the same offset as the drive coils, when moved about in the vicinity of the probe, produces a corresponding movement of graphical images on a display screen. The graphical images provide intuitive information as to how the guide must be moved to accurately align the drill bushing with the axis of the transverse hole. With the aid of continuous visual information on the display screen, the surgeon holds the guide and bushing in proper position while making a stab incision to the bone, while drilling or driving a trocar through the near and far cortices of the bone, and while inserting and fastening the locking screw. The intrumentation enables distal targeting by surgeons without specialized training or experience and eliminates the need for C-arm x-ray machines that increase operating room costs and increase the risk of radiation exposure to the patient and the surgeon.

Claims

1. A device for locating a distal transverse hole disposed at known axial and radial positions in a hollow interlocking nail inserted into the medullary canal of a fractured bone and for drilling therethrough coaxially with the distal transverse hole, comprising:

a probe adapted to be inserted into the interlocking nail;

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 distal transverse hole in the interlocking nail;

radial positioning means for securely placing and retaining said proximal magnetic axis at a predetermined angular relationship with said distal transverse hole;

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 fractured bone coaxially with said distal transverse hole;

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 distal transverse hole;

whereby said probe may be inserted into the interlocking nail 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 distal transverse hole;

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 said fractured bone coaxially with said distal transverse hole.

2. The device recited in claim 1, wherein each of said proximal electromagnetic drive means and said distal electromagnetic drive means consists of an electromagnetic coil and said coils are energized alternately to generate alternate magnetic fields that are independent and noninteracting with one another.

3. The device recited in claim 1, wherein said axial positioning means consists of a stopper in the probe for engagement with the interlocking nail at a point whereby said distal magnetic axis is positioned at said predetermined axial distance from the distal transverse hole in the interlocking nail.

4. The device recited in claim 1, wherein said radial positioning means consists of a tab in the probe for engagement with a corresponding notch in the interlocking nail at a point whereby said proximal magnetic axis is positioned at said predetermined angular relationship with said distal transverse hole.

5. The device recited in claim 1, wherein said first electromagnetic sensor means consists of a first pair of coplanar receiving coils capable of emitting said first output signal responsive to the flux received from said distal electromagnetic drive means, such that the first output signal is zero when said distal magnetic axis is coplanar with said first pair of receiving coils.

6. The device recited in claim 1, wherein said second electromagnetic sensor means consists of a second pair of coplanar receiving coils capable of emitting said second output signal responsive to the flux received from said proximal electromagnetic drive means, such that the second output signal is zero when said proximal magnetic axis is coplanar with said second pair of receiving coils.

7. The device recited in claim 1, wherein said first electromagnetic sensor means consists of a first pair of coplanar receiving coils capable of emitting said first output signal responsive to the flux received from said distal electromagnetic drive means, such that the first output signal is zero when said distal magnetic axis is coplanar with said first pair of receiving coils;

wherein said second electromagnetic sensor means consists of a second pair of coplanar receiving coils capable of emitting said second output signal responsive to the flux received from said proximal electromagnetic drive means, such that the second output signal is zero when said proximal magnetic axis is coplanar with said second pair of receiving coils; and

wherein said first and second pairs of receiving coils are disposed in planes that are perpendicular to one another.

8. The device recited in claim 1, wherein said display means comprises a screen with fixed reference lines relative to a target point;

comprises a first movable pointer displayed on said screen and having a screen position responsive to an axial distance between said first electromagnetic sensing means and said distal magnetic axis, such that said first movable pointer coincides with said target point when said first electromagnetic means is in said first predetermined alignment with said distal magnetic axis; and

comprises a second movable pointer displayed on said screen and having a screen position responsive to a radial distance between said second electromagnetic sensing means and said proximal magnetic axis, such that said second movable pointer coincides with said target point when said second electromagnetic means is in said second predetermined alignment with said proximal magnetic axis.

9. The device recited in claim 1, wherein said drilling means for drilling a hole through said fractured bone coaxially with said distal transverse hole consists of a drilling guide and a drilling bit coaxially aligned thereto.

10. The device recited in claim 7, wherein said drilling means for drilling a hole through said fractured bone coaxially with said distal transverse hole consists of a drilling guide and a drilling bit coaxially aligned thereto, wherein said drilling guide is disposed in parallel to both of said first and second pairs of coplanar receiving coils.

11. 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.

12. 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.

13. 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.