Distal targeting system

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.

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.