Abstract:
A medical catheter extrusion forms a sheath around a wire. The extrusion is coupled to a steering and motivating handle. The handle is part of a housing that houses a motivation component fixed to the housing, a crankshaft, or similar eccentric component, couples to the motivation component, which is coupled to a proximal end of the wire. At the wire&#39;s distal end, a cutting tip with canted teeth couples to the wire. The cutting tip is capable of cutting bone when moving axially toward the catheter extrusion but glides across the bone without cutting it when moving axially away from the catheter extrusion. The motivation component can be a motor or buttons or a trigger, that couple to the wire and converts manual movement into reciprocating motion of the flexible shaft. The shaft&#39;s reciprocating motion moves the flexible and steerable shaft back and forth to move the cutting tip.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. 119(e) to U.S. provisional patent application No. 61/166,693 entitled “Method and system for shaving bone using a catheter,” which was filed Apr. 3, 2009, and is incorporated herein by reference in its entirety. This application also incorporates by reference U.S. patent application Ser. No. 12/132,102 in its entirety. 
    
    
     BACKGROUND 
     Catheters used in the medical industry, such as catheter products produced by Myelotec, Inc. for example, steer a distal end by manipulating stainless steel wires anchored into the distal tip of a plastic extrusion.  FIG. 1  illustrates a catheter assembly  2  comprising extrusion  3  and distal end  4 . Distal end  4  may include a lens and light carrying means, such as optical fiber, that facilitates a user viewing tissue and organs of a human, or animal, body. Applying tension to the proximal end  5  of either wire  6  causes distal end  4  of extrusion  3  to deflect in the direction of the wire  6 , to which tension was applied, relative to the centerline of extrusion  3 . For example,  FIG. 2  illustrates that tension has been applied to rightmost steering wire  6 R causing distal end  4  to deflect to the right. Similarly, applying tension to steering wire  6 L (the figure does not illustrate this scenario for clarity) would cause distal end  4  of extrusion  3  to deflect to the left, or the opposite direction as that shown in the figure, but in the same plane as the movement depicted in  FIG. 2 . 
     In a two-wire configuration, such as the Naviscope® steerable catheter product line sold by Myelotec, Inc., a user may steer in only one plane at a time. Although the steering plane may be rotated 90° via a steering yoke and external collar from horizontal to vertical (See  FIG. 3 ), compound movements, such as left-to-right sweeps while pointing downward, cannot be performed using two steering wires. As shown in  FIG. 3 , yoke bearing  8  receives rotation yoke  10  and rotation pin  11  protrudes through rotation slot  13 . When housing halves  15  and  17  are mated together, collar  22  slides over the end of the mated housing halves and engages pin  11 . Thus, a user gripping collar  22  can rotate extrusion  3  by turning collar  22 . The extent of slot  13  limits the amount of rotation so that wires  6 R and  6 L remain untangled. When steering bearing  16  has received axle  18  of steering wheel  20 , manipulating buttons  12  and  14  causes the distal end of extrusion  3  to deflect correspondingly. For example, pressing button  14  induces tension in steering wire  6 R, which causes the distal end to deflect to the right as described above in connection with the discussion of  FIG. 2 . Similarly, pressing button  12  would induce tension in steering wire  6 L and cause the distal end to deflect to the left. 
     A user may be able to rotate the steering plane (via collar  22 ) and re-point distal end  4  toward a desired location within a body, but only if the desired location falls within the area depicted in  FIG. 7A . Should the location fall outside the possible steering planes (the point depicted with an X in FIG.  7 A e.g.) the user must rotate housing halves  15  and  17  for viewing. However, since the optical fiber is attached to the housing, the image seen will be tilted with respect to the previous orientation of the image. Thus, there is a need for a catheter steering device that can steer a distal end of a catheter extrusion in multiple planes rather than one plane without causing image tilt as occurs when the distal end is rotated via the housing halves rather than being steered. Also, a need occasionally arises to cut bone without cutting a patient. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a catheter extrusion for facilitating two-way steering of a distal end. 
         FIG. 2  illustrates the distal end of a catheter extrusion deflected in a rightward direction. 
         FIG. 3  illustrates a Naviscope steerable catheter pistol grip assembly for facilitating two-way steering of a catheter extrusion distal end. 
         FIG. 4A  illustrates a sectional view of a catheter extrusion for facilitating two-way steering. 
         FIG. 4B  illustrates a sectional view of a catheter extrusion for facilitating three-way steering. 
         FIG. 5  illustrates a catheter extrusion for facilitating three-way steering of a distal end. 
         FIG. 6  illustrates a Naviscope steerable catheter pistol grip assembly modified to facilitate three-way steering of a catheter extrusion distal end. 
         FIG. 7A  illustrates the possible steering planes of a two-wire steered extrusion. 
         FIG. 7B  illustrates possible planes of a three-way steered extrusion. 
         FIG. 8  illustrates a Naviscope steerable catheter pistol grip assembly modified to motivate a flexible shaft in a back and forth motion through a catheter to shave bone. 
         FIG. 9  illustrates a bone shaving implement with canted teeth projecting from a cutter coupled to a flexible shaft. 
     
    
    
     DETAILED DESCRIPTION 
     Turning now to the figures,  FIG. 4  illustrates an aspect by comparing a sectional plan view of a catheter extrusion  3  for two way steering that uses two steering wires in  FIG. 4A  with a sectional plan view in  FIG. 4B  of a catheter that facilitates multiway steering using three steering wires. As discussed in connection with previous figures, steering wires  6 R and  6 L enter extrusion  3  through respective steering wire lumens  24 R and  24 L. Operational lumens  26  and  28  are shown larger than the steering wire lumens  24 R and  24  L because they facilitate operational items such as, for example, fiber for passing light to and from a distal end of extrusion  3  and possibly a tube carrying air or wires for manipulating a cutter for abscising tissue. In the two steering wire system facilitated by the section of extrusion  3  shown in  FIG. 4A , lumens  26  and  28 , although of equal diameter, are sized so that they equitably share the sectional area of the section shown in the figure with lumens  24 L and  24 R. 
     Turing now to  FIG. 4B , extrusion  30  defines center steering wire lumen  24 C. Lumen  24 C receives and routes steering wire  6 C, which transfers force from a hand grip to a distal end of extrusion  30 , causing the distal end to move in a plane orthogonal to the plane within which wires  6 L and  6 R cause movement. Since only center wire  6 C causes motion in what will be referred to herein as a second plane (the first plane being the plane in which tension in wires  6 L and  6 R cause motion), the motion in the second plane will occur in only one direction away from a relaxed, or straight-extending, position of the distal end of extrusion  30 . To accommodate the extra area of the illustrated section of extrusion  30 , the extrusion defines smaller lumen  32  rather than lumen  28 , which is similarly sized as lumen  26 . Extrusion  30  defines the size of smaller lumen  32  to make room for the addition of steering wire lumen  24 C while still being large enough in diameter to accommodate items described above, such as light fiber or possibly wires for manipulating a biopsy tissue sample: collector. Alternatively, a designer/manufacturer may increase the size of the extrusion from, for example, 3.0 mm to 3.3 mm, to facilitate the extra operational lumen(s) of suitable size. 
     Turning now to  FIG. 5 , the figure illustrates steering wires  6 L,  6 R and  6 C being routed through corresponding steering wire lumens defined by extrusion  30 . Tension in center steering wire  6 C causes distal tip to deflect downward as shown in the figure. It will be appreciated that a fourth steering wire and corresponding steering wire lumen could be added to cause motion of distal end  4  in the up direction as well as the down direction. 
     Turning now to  FIG. 6 , the figure illustrates a second plane steering dial  34  added to the Naviscope steerable catheter assembly that is shown in  FIG. 3 . Manipulation of steering tab  36  in the clockwise direction causes tension in center steering wire  6 C, which causes motion in the down direction of distal tip  4 . Center steering wire  6 C shares guide wheel  38  with left steering wire  6 L, which is already present in a two wire steering system, thus reducing the number of addition parts to facilitate three wire steering as compared to two wires steering. Steering wire  6 R continues to use guide wheel  40  as it does in a two wire steering arrangement. 
     Turning now to  FIG. 7B , for the figure shows that, the point depicted with an X can be viewed in proper orientation by first deflecting distal end  4  downward, and then steering left to right as normal. Thus, image orientation does not change as a user steers extrusion  3  as compared to the image orientation change that occurs when a user rotates the steering handgrip housing in a two-wire steering system. 
     Turning now to  FIG. 8 , the figure illustrates a steerable catheter handle grip housing  41  as described above. Housing  41  provide a structure for mounting an electric motor  42 , or similar motivating component. A user may turn on or off the motor by using a button mounted on the housing, or squeezing a switch grip that operates electrical switch contacts. Other than a motor, manually operated buttons on the outside of housing  41  may cause an output shaft to rotate when a user manipulates the buttons. Motor  42  couples to flexible shaft  44 , preferably a wire, which projects through shaver shaft catheter  25 . Catheter  25  slidingly covers wire  44 , acting as a sheath, so the wire can slide back and forth (substantially coaxially) inside the catheter. Wire  44  extends through proximal end  46  of catheter  25 . It will be appreciated that proximal end  46  of catheter  25  may terminate where the catheter enters steering collar  22 . Or, catheter  25  may extend through collar  22  and terminate near motor  42 . If catheter  25  extends through collar  22 , the catheter should terminate far enough away from motor  42  to permit clearance for movement of conversion means  48 . Conversion means  48  may be a cam, a crank, a lever, a wheel with a attachment screw at a point on the perimeter of the wheel, or other means, that can convert rotational movement of an output shaft from motor  42  into reciprocating motion, or back and forth motion. 
     An example of the wheel and attachment point is similar to the operation of a steam locomotive&#39;s drive wheel in reverse. In a locomotive scenario, reciprocating motion of the piston pushing a rod attached near the perimeter of the wheel converts into rotational motion of the drive wheel. In the bone shaver apparatus described herein, the turning wheel driven by the motor can couple to the flexible shaft at an attachment point near the perimeter of the wheel. Thus the wheel and attachment point convert rotational motion of the wheel into reciprocating, or back and forth, motion of the flexible shaft. 
     Alternatively, in another aspect, a trigger hinged from housing  41  to move similar to how a gun trigger moves may be used to cause shaft  44  to move back and forth axially with respect to an axis of catheter shaft  25 . It will be appreciated that the closer catheter  25  terminates with respect to conversion means  48 , the more flexible wire  44  can be before buckling of the shaft occurs. 
     Shaft  44  exits catheter  25  at a distal end (distal and proximal terminology refers to location relative to housing  41 ). At distal end  50 , a cutting portion comprising a cutter, or shaver tip  52 , couples to wire  44 . Clearance  54  between the shaver tip  52  and the extent of catheter  25  where it ends should be enough to prevent interference between the tip and the catheter when conversion means  48  has moved tip  52  back towards proximal end  46  at the maximum displacement of the conversion means. 
     Conversion means  48  places wire  44  in tension as it moves in a back direction (toward the proximal end). This can transfer substantial force axially with respect to the wire to shaver tip  52 . However, when conversion means  48  moves in a forward, or forth, direction (toward the distal end), wire  44  cannot transfer much force to tip  52  because the wire is placed in a compression condition. Thus, shaver tip  52  is designed to impart cutting force to a bone when moving in a backward direction and not impart much force in the forward direction. 
     Turning now to  FIG. 9 , the figure illustrates different views of shaver tip  52 . View A and view B illustrate canted cutting teeth  56 . The cant angle is toward the direction of backward motion of wire  44  shown in  FIG. 8 . Thus, when wire  44  moves in the backward direction, canted teeth  56  cut bone. But, when wire  44  moves in the forward direction, since teeth  56  angle away from the direction of motion, the teeth essentially glide over the bone, thus not imparting much, if any, resistive force that the shaft, or wire, which is in a compression state, need overcome. Although wire  44  typically is sheathed in catheter  25 , trying to cut bone when tip  52  moves in the forward direction would tend to cause buckling which could lead to binding of the wire in the catheter. More importantly, even with minimal distance between the end of the proximal end of catheter  25  and the conversion means, more than a very minimal compression of wire  44  between the extent at the proximal end of the catheter and the attachment point where wire  44  attaches to the conversion means  48  would cause buckling of the wire in that unguided portion. If the wire buckles in the unguided portion between the extent of catheter  25  and conversion means  48  rather than staying relatively rigid, the motion of the conversion means does not translate into forward motion at tip  52 . And, if tip  52  does not move in a forward motion after moving in a backward motion, it will not perform cutting again because motion on the conversion means in the backward motion would not move the cutting tip, but would only straighten the buckled wire portion. Thus, canted teeth  54  on cutting tip  52  provide cutting in the backward motion of wire  44  while allowing the tip to slide over the just-cut bone when moving in the forward direction. 
     It will be appreciated that cutting tip  52  may be manufactured separately from wire  44  and coupled to the wire by welding, clamping, gluing, pressing, stamping, or other similar methods. Alternatively, cutting tip  52  may be formed into the end of wire  44  by pressing, or smashing, the distal end of the wire into an oblong shape and then machining canted teeth  54  in to the formed oblong shape. 
     It will also be appreciated that the electric, motor can be powered by batteries housed in the housing handle and electrically coupled to the motor in series with the switch means discussed above. Or, an external power supply can provide power to the motor through a plugged connection mounted on the housing with the switch electrically in series with the motor. In addition, a trigger, or a squeeze grip switch can comprise a potentiometer means, or other means for regulating power delivery from the power source to the motor, so that a user operating the bone shaving apparatus can vary the speed of the cutting tip in proportion to pressure on the trigger or grip.