Distal targeting system

• US 5,584,838 A
• Filed: 02/28/1994
• Issued: 12/17/1996
• Est. Priority Date: 07/09/1991
• Status: Expired due to Fees

• Current Assignee: Stryker Corporation
• Original Assignee: Stryker Corporation
• Inventors: Evans, James A., Ely, Douglas J., Sertic, Lisa D., Alves, Matthew S., Philipp, Christopher D., Rona, Mehmet
• Primary Examiner(s): Hafer, Robert A.
• Assistant Examiner(s): HANLON, BRIAN EMMETT
• Application Number:
  US08/203,664
• Time in Patent Office: 1,023 Days
• Field of Search: 408/13, 408/16, 408/72 B, 408/115 B, 408/97, 606/172, 324/207.17, 324/207.18, 324/207.19, 324/243, 324/245, 324/246, 324/67, 324/326, 324/226
• US Class Current: 606/96
• 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 2090/3958 emitting a signal
• CPC Class Codes: G01B 7/31 for testing the alignment of axes
• CPC Class Codes: Y10T 408/175 to control relative positioning of Tool and work
• CPC Class Codes: Y10T 408/21 with signal, indicator, illuminator or optical means
• CPC Class Codes: Y10T 408/56245 including tool-guide [or bushing]
• CPC Class Codes: Y10T 408/568 Guide bushing

Abstract

A femoral nail which can be implanted in a bone has a transverse hole, and an arrangement is provided for generating a magnetic field which has a maximum strength along an axis of the transverse hole and which decreases in strength in directions radially away from the axis. A drill guide for axially aligning a drill with the transverse hole has an axial drill opening through it, and first and second sensor arrangements are provided at axially spaced locations on the drill guide and each have a plurality of sensors which are at angularly spaced locations and are spaced radially from the opening through the drill guide. An arrangement responsive to the first and second sensor arrangements detects a deviation of the drill opening in the drill guide from coaxial alignment with the axis of the hole in the member, and provides an operator perceptible indication of a radial direction from the drill opening to the axis.

Claims

1. A medical instrument guide assembly for positioning a medical instrument over a point on a body, said assembly including:

a positioning coil adapted to be inserted in the body so as to be centered along an axis that intersects the point over which the instrument is to be positioned;

a power supply connected to said positioning coil for applying a voltage to said positioning coil so as to cause the generation of a magnetic field centered along an axis intersecting the body point;

an instrument guide for receiving the medical instrument to be positioned, said instrument guide having an elongated center axis;

a first sensor disk attached to said instrument guide so as to be coaxially mounted to said instrument guide at a position proximal to the body, said first sensor disk including a first sensor disk first pair of sensors for monitoring the magnetic field generated around said positioning coil, each said first sensor disk sensor being configured to generate a sensor signal representative of the magnetic field strength in the vicinity of said first sensor disk sensor, said first sensor disk sensors being positioned on said first sensor disk at diametrically opposed locations relative to said instrument guide center axis and being spaced a common distance from said instrument guide center axis;

a second sensor disk attached to said instrument guide so as to be coaxially mounted to said instrument guide at a position distal to the body, said second sensor disk including a second sensor disk first pair of sensors for monitoring the magnetic field generated around said positioning coil, each said second sensor disk sensor being configured to generate a sensor signal representative of the magnetic field strength in the vicinity of said sensor, said second sensor disk sensors being positioned on said second sensor disk at diametrically opposed locations relative to said instrument guide center axis and being spaced a common distance from said instrument guide center axis, wherein said second sensor disk first pair of sensors are spaced further from said instrument guide center axis than the distance at which said first sensor disk first pair of sensors are spaced;

a signal processor connected to said first sensor disk first pair of sensors to receive said sensor signals therefrom and to said second sensor disk first pair of sensors for receiving said sensor signals therefrom, said signal processor being configured to compare said signals produced by said first sensor disk first pair of sensors to each other and to compare said signals produced by said second sensor disk first pair of sensors to each other and, based on said comparisons, to generate sensor disk position signals that indicate if each said sensor disk is centered over the magnetic field axis and, if either said sensor disk is not so positioned, the direction in which said sensor disk should be moved in order to be so positioned; and

a display connected to said signal processor for receiving said sensor disk position signals, said display including a plurality of display elements actuatable in response to said sensor disk position signals to indicate if said elongated instrument guide axis is aligned over the body point and if a portion of said instrument guide axis is not so aligned, the direction in which said instrument guide should be moved in order to be so aligned.

2. The medical instrument guide assembly of claim 1, wherein said display is mounted to said instrument guide.

3. The medical instrument guide assembly of claim 1, wherein:

a second pair of sensors is mounted on said first sensor disk for monitoring the magnetic field produced by said positioning coil, said sensors each said first sensor disk sensor pair being located diametrically across from each other relative to said instrument guide center axis and said first sensor disk sensors are mounted on said first sensor disk on a first radius relative to said instrument guide center axis;

a second pair of sensors is mounted on said second sensor disk for monitoring the magnetic field produced by said positioning coil, said sensors of each said second sensor disk sensor pair being located diametrically across from each other relative to said instrument guide center axis and said second sensor disk sensors are mounted on said second sensor disk on a second radius relative to said instrument guide center axis, said second radius on which said second disk sensors are mounted being greater than said first radius on which said first sensor disk sensors are mounted on said first sensor disk; and

said signal processor is further configured to produce said sensor disk position signals by comparing said signals from said sensors that form each said pair of sensors.

4. The medical instrument guide assembly of claim 3, wherein said display is mounted to said instrument guide.

5. The medical instrument guide assembly of claim 4, wherein said instrument guide is a hollow tubular member having a center space adapted for receiving the medical instrument.

6. The medical instrument of claim 3, wherein said sensors are coils.

7. The medical instrument guide assembly of claim 3, wherein said instrument guide is a hollow tubular member having a center space adapted for receiving the medical instrument.

8. The medical instrument guide assembly of claim 3, further including an audio generator connected to said signal processor to receive said sensor disk position signals, said audio generator being configured to emit a plurality of audible tones including a distinct tone emitted only when said sensor disk position signals indicate both said sensor disks are aligned with the axis of the magnetic field.

9. The medical instrument of claim 1, wherein said sensors are coils.

10. The medical instrument guide assembly of claim 1, wherein said instrument guide is a hollow tubular member having a center space adapted for receiving the medical instrument.

11. The medical instrument guide assembly of claim 1, further including an audio generator connected to said signal processor to receive said sensor disk position signals, said audio generator being configured to emit a plurality of audible tones including a distinct tone emitted only when said sensor disk position signals indicate both said sensor disks are aligned with the axis of the magnetic field.

12. A positioning system for positioning a cutting instrument over a bore hole formed in an intramedullary nail disposed in a cavity within a bone, the bore hole having an axis, said system including:

a positioning coil configured to be disposed in the intramedullary nail, said coil having a center axis for positioning in the intramedullary nail so as to be axially aligned with the bore hole;

a power supply connected to said positioning coil for applying a voltage to said positioning coil so as to cause the generation of a magnetic field centered along the bore hole axis;

an instrument guide for receiving the cutting instrument to be positioned, said instrument guide having an elongated center axis;

a first sensor disk attached to said instrument guide so as to be coaxially mounted to said instrument guide at a position proximal to the bone, said first sensor disk including a first sensor disk first pair of sensors for monitoring the magnetic field generated around said coil, each said first sensor disk sensor being configured to generate a sensor signal representative of the magnetic field strength in the vicinity of said first sensor disk sensor, said first sensor disk sensors being positioned on said first sensor disk at diametrically opposed locations relative to said instrument guide center axis and being spaced a common distance from said instrument guide center axis;

a second sensor disk attached to said instrument guide so as to be coaxially mounted to said instrument guide at a position distal to the bone, said second sensor disk including a second sensor disk first pair of sensors for monitoring the magnetic field generated around said coil, each said Second sensor disk sensor being configured to generate a sensor signal representative of the magnetic field strength in the vicinity of said sensor, said second sensor disk sensors being positioned on said second sensor disk at diametrically opposed locations relative to said instrument guide center axis and being spaced a common distance from said instrument guide center axis, wherein said second sensor disk first pair of sensors are spaced further from said instrument guide center axis than the distance at which said first sensor disk first pair of sensors are spaced;

a signal processor connected to said first sensor disk first pair of sensors to receive said sensor signals therefrom and to said second sensor disk first pair of sensors for receiving said sensor signals therefrom, said signal processor being configured to compare said signals produced by said first sensor disk first pair of sensors to each other and to compare said signals produced by said second sensor disk first pair of sensors to each other and, based on said comparisons, to generate sensor disk position signals that indicate if each said sensor disk is centered over the magnetic field axis based on said sensor signals and, if either said sensor disk is not so positioned, the direction which said sensor disk should be moved in order to be so positioned; and

a display connected to said signal processor for receiving said sensor disk position signals, said display including a plurality of display elements actuatable in response to said sensor disk position signals to indicate if said elongated instrument guide is aligned over the intramedullary nail bore hole and if a portion of said instrument guide is not so aligned, the direction in which said instrument guide should be moved in order to be so aligned.

13. The positioning system of claim 12, wherein said display is mounted to said instrument guide.

14. The positioning system of claim 12, wherein:

a second pair of sensors is mounted on said first sensor disk for monitoring the magnetic field produced by said coil, said sensors of each said first sensor disk sensor pair being located diametrically across from each other relative to said instrument guide center axis and said first sensor disk sensors are mounted on said first sensor disk on a first radius relative to said instrument guide center axis and;

a second pair of sensors is mounted on said second sensor disk for monitoring the magnetic field produced by said coil, said sensors of each said second disk sensor pair being located diametrically across from each other relative to said instrument guide center axis and said second sensor disk sensors are mounted on said second sensor disk on a second radius relative to said instrument guide center axis, the second radius on which said second disk sensors are mounted being greater than the first radius around which said first sensor disk sensors are mounted on said first sensor disk.

15. The positioning system of claim 14, wherein said display is mounted to said instrument guide.

16. The positioning system of claim 15, wherein said coil is spaced away from the nail bore.

17. The positioning system of claim 14, wherein said sensors are coils.

18. The positioning system of claim 14, wherein said coil is configured to be removably secured in the intramedullary nail.

19. The positioning system of claim 14, further including an audio generator connected to said signal processor to receive said sensor disk position signals, said audio generator being configured to emit a plurality of audible tones including a distinct tone emitted only when said sensor disk position signals indicate both said sensor disks are aligned with the axis of the magnetic field generated by said coil.

20. The positioning system of claim 12, wherein said sensors are coils.

21. The positioning system of claim 12, wherein said coil is configured to be removably secured in the intramedullary nail.

22. The positioning system of claim 12, further including an audio generator connected to said signal processor to receive said sensor disk position signals, said audio generator being configured to emit a plurality of audible tones including a distinct tone emitted only when said sensor disk position signals indicate both said sensor disks are aligned with the axis of the magnetic field generated by said coil.

23. The positioning system of claim 12, wherein said coil comprises a flexible sheet of nonconductive material configured to be removably disposed in the intramedullary nail wherein a conductive trace is located on said flexible sheet so as to function as said coil.

24. The positioning system of claim 12, further including a sleeve configured to be removably disposed in the intramedullary nail wherein said coil is secured to said sleeve.

25. A drill guide for positioning a drill with an elongated drill bit over a point on a bone, said drill guide including:

an elongated guide tube having a center opening for receiving the drill bit, said guide tube having a selected inside diameter and a selected outside diameter;

a positioning assembly configured to locate said guide tube over the selected bone point, said positioning assembly including;

a magnetic field generator configured to be positioned in the bone for generating magnetic fields centered on the selected bone point;

a sensor array attached to said guide tube for monitoring the strength of the magnetic fields at a plurality of locations spaced from said guide tube, said sensor array being configured to produce sensor signals representative of the monitored magnetic field strength; and

a monitoring circuit coupled to receive said sensor signals and including a display assembly, said monitoring circuit being configured to produce an indication on said display assembly when said guide tube is positioned over the selected bone point;

a plurality of tubular locking sleeves, each said tubular locking sleeve having an axially extending center bore for receiving the drill bit and being formed so as to have a stem section shaped with an outside diameter so as to allow said stem section to be disposed in said guide tube and a head section having an outside diameter greater than said inside diameter of said guide tube wherein, said head sections of each said sleeve has a different overall length and one said sleeve is disposed in said guide tube so as to extend outwardly toward the bone.

26. The drill guide of claim 25, wherein said locking sleeve head sections are formed with outwardly extending teeth.

27. The drill guide of claim 25, wherein said locking sleeve head sections are formed to have an outside diameter equal to said outside diameter of said guide tube.

28. The drill guide of claim 25, wherein said positioning assembly sensor array includes first and second sensor disks attached to said guide tube, said first sensor disk being attached to said guide tube at a location proximal to the bone and said second sensor disk being attached to said guide tube at a location distal to said bone;

a first sensor disk pair of sensors attached to said first sensor disk for monitoring magnetic field strength; and

a second sensor disk pair of sensors attached to said second disk for monitoring magnetic field strength.

29. The drill guide of claim 28, wherein said first sensor disk sensors are mounted to said first sensor disk on a first radius centered around said guide tube center opening and said second disk sensors are mounted to said second sensor disk on a second radius centered around said guide tube center opening, said second radius being greater than said first radius around which said first sensor disk sensors are mounted to said first sensor disk.