Orthopaedic cutting instrument and method

Abstract

An orthopaedic cutting instrument and associated methods are presented.

1 . An orthopaedic cutting instrument comprising: 
 a drive mechanism;    a cutter coupled to the drive mechanism;    means for driving the drive mechanism to produce oscillating rotary motion of the cutter; and    means for adjusting the angular amplitude of the oscillating rotary motion.    
   
   
       2 . The instrument of  claim 1  further comprising: 
 means for driving the drive mechanism to produce continuous rotary motion; and    means for changing from oscillating rotary motion to continuous rotary motion.    
   
   
       3 . The instrument of  claim 1  further comprising: 
 means for combining oscillating rotary motion and continuous rotary motion to oscillate the cutter while simultaneously rotating the cutter.    
   
   
       4 . The instrument of  claim 1  wherein the drive mechanism comprises a motor and further wherein the means for driving the drive mechanism to produce oscillating rotary motion comprises a sending a drive signal to the motor that oscillates from positive to negative signal values.  
   
   
       5 . The instrument of  claim 4  wherein the means for adjusting the angular amplitude comprises adjusting the amplitude of the oscillating drive signal.  
   
   
       6 . An orthopaedic cutting instrument comprising: 
 a handpiece including a motor;    an elongated shaft extending from the handpiece and defining a shaft centerline, the shaft being coupled to the motor to transmit rotary motion from the motor;    a cutter coupled to the shaft; and    a control unit for driving the motor to produce oscillating rotary motion of the cutter about the shaft centerline.    
   
   
       7 . The instrument of  claim 6  wherein the shaft comprises a flexible shaft.  
   
   
       8 . The instrument of  claim 6  wherein the shaft includes a rigid portion.  
   
   
       9 . The instrument of  claim 8  wherein the shaft includes a curved portion.  
   
   
       10 . The instrument of  claim 8  wherein the shaft includes a steerable portion movable relative to the shaft centerline to change the angle of the cutter relative to the shaft centerline.  
   
   
       11 . The instrument of  claim 6  wherein the shaft comprises fluid delivery and aspiration channels to transmit fluid to and away from the cutter.  
   
   
       12 . An orthopaedic cutting instrument comprising: 
 a drive mechanism;    a cutter coupled to the drive mechanism; and    means for driving the drive mechanism to preferentially cut relatively hard tissue and spare relatively soft tissue.    
   
   
       13 . The instrument of  claim 12  wherein the drive mechanism comprises a handpiece containing a motor and an elongated shaft defining a longitudinal centerline coupled to the motor and extending from the handpiece, and further wherein the means for driving comprises a control unit that sends an oscillating drive signal to the motor to cause the cutter to oscillate rotationally in a plane about the shaft centerline.  
   
   
       14 . The instrument of  claim 13  wherein the cutter includes a plurality of teeth having an angular spacing measured in the cutter rotation plane, the cutter oscillating with an angular amplitude that is greater than the angular spacing of the teeth.  
   
   
       15 . The instrument of  claim 13  wherein the cutter includes a plurality of teeth having an angular spacing measured in the cutter rotation plane, the cutter oscillating with an angular amplitude that is less than the angular spacing of the teeth.  
   
   
       16 . The instrument of  claim 15  wherein the control unit further sends a constant drive signal combined with the oscillating drive signal to the motor to cause the cutter to oscillate while simultaneously rotating.  
   
   
       17 . The instrument of  claim 13  wherein the shaft includes a portion that is steerable to change the angle of the cutter relative to the shaft.  
   
   
       18 . The instrument of  claim 12  wherein the cutter comprises a circular blade having teeth formed around its perimeter.  
   
   
       19 . The instrument of  claim 18  wherein the cutter comprises a plurality of circular blades mounted on a common shaft, the blades having graduated diameters.  
   
   
       20 . The instrument of  claim 12  wherein the cutter comprises a hollow shell having an interior and an outer surface, the shell having teeth formed on its outer surface, the shell including openings from the outer surface to the inner surface adjacent the teeth.  
   
   
       21 . The instrument of  claim 12  wherein the cutter comprises a hemispherical body defining a pole and an equator, the body defining longitudinally oriented and circumferentially spaced teeth extending from the pole to the equator.  
   
   
       22 . The instrument of  claim 12  wherein the cutter comprises an expandable cutter head formed from a flexible material with cutting teeth attached to its outer surface.  
   
   
       23 . An orthopaedic cutting instrument for cutting tissue at a surgical site, the surgical site being defined within a surgical navigation coordinate system, the instrument comprising: 
 a drive mechanism;    a cutter coupled to the drive mechanism;    means for tracking the cutter within the surgical navigation coordinate system;    means for defining a cut zone within the surgical navigation coordinate system corresponding to a portion of the surgical site;    means for driving the drive mechanism to cause the cutter to cut tissue when the cutter is within the cut zone; and    means for stopping the drive mechanism to cause the cutter to cease cutting tissue when the cutter is outside of the cut zone.    
   
   
       24 . The instrument of  claim 23  wherein the means for driving causes the cutter to oscillate rotationally.  
   
   
       25 . The instrument of  claim 23  wherein the means for driving causes the cutter to oscillate rotationally while simultaneously rotating.  
   
   
       26 . The instrument of  claim 23  wherein the drive mechanism comprises a handpiece including a motor and a control unit coupled to the handpiece to send a drive signal to the motor, the means for tracking being coupled to the control unit to modify the drive signal to cause the motor to stop when the cutter is outside of the cut zone.  
   
   
       27 . The instrument of  claim 23  further comprising means for steering the cutter to cause the cutter to change position within the cut zone.  
   
   
       28 . The instrument of  claim 27  wherein the means for steering comprises actuators coupled to the means for tracking, the means for tracking transmitting a signal to the actuators to cause the cutter to change position within the cut zone.  
   
   
       29 . The instrument of  claim 23  wherein the means for tracking is able to produce an output indicating areas with the cut zone through which the cutter has not yet passed.  
   
   
       30 . A method of cutting tissue at a surgical site comprising: 
 introducing a cutter into a surgical site;    driving the cutter to preferentially cut relatively hard tissues as opposed to relatively soft tissues; and    manipulating the cutter within the surgical site to morselize relatively hard tissues.    
   
   
       31 . The method of  claim 30  wherein the cutter is mounted on a curved shaft and further wherein manipulating the cutter comprises moving the shaft from side to side and rotating the shaft to cause the cutter to sweep an area larger than the cutter diameter.  
   
   
       32 . The method of  claim 30  wherein the cutter is mounted on an elongated shaft and the shaft includes a steerable portion, manipulating the shaft comprising steering the steerable portion to cause the cutter to change position relative to the shaft.  
   
   
       33 . The method of  claim 30  wherein driving the cutter comprises moving the cutter in an oscillating rotary motion.  
   
   
       34 . The method of  claim 33  further comprising: 
 adjusting the oscillation amplitude to adjust the cutting characteristics of the cutter.    
   
   
       35 . The method of  claim 33  further comprising: 
 adjusting the oscillation frequency to adjust the cutting characteristics of the cutter.    
   
   
       36 . The method of  claim 30  wherein driving the cutter comprises moving the cutter in a continuous rotary motion.  
   
   
       37 . The method of  claim 30  wherein driving the cutter comprises moving the cutter in an oscillating rotary motion while simultaneously rotating the cutter in a continuous rotary motion.  
   
   
       38 . The method of  claim 30  wherein introducing a cutter into a surgical site comprises moving the cutter in a continuous rotary motion to form an access portal and driving the cutter comprises moving the cutter in an oscillating rotary motion.  
   
   
       39 . The method of  claim 30  wherein introducing a cutter into a surgical site comprises forming a portal through a femur from the lateral side of the femur to the hip joint.  
   
   
       40 . The method of  claim 39  wherein driving the cutter selectively removes the femoral head.  
   
   
       41 . A method of cutting tissue at a surgical site comprising: 
 introducing a cutter into a surgical site;    tracking the position of the cutter with a surgical navigation system; and    driving the cutter with cutter position dependent drive inputs.    
   
   
       42 . The method of  claim 41  further comprising: 
 defining a cut zone within the surgical navigation system, driving the cutter comprising driving the cutter to cut tissue when the cutter is within the cut zone.    
   
   
       43 . The method of  claim 41  wherein introducing a cutter into a surgical site comprises forming a portal through a femur from the lateral side of the femur to the hip joint.  
   
   
       44 . The method of  claim 43  wherein driving the cutter selectively removes the femoral head.