Abstract:
A medical device is provided for removing material from a body vessel comprising a tube, a drive shaft extending through the tube, a cutter member rotatable around its access having a tip and relatively sharp cutting edges extending outwardly from the access, and a housing enclosing the cutting edges of the cutter member so that the tip of the cutter member extends outside the housing to cut material in cooperation with the housing.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to a surgical instrument for clearing obstructions in ducts, particularly but not exclusively arteries.  
         BACKGROUND OF THE INVENTION  
         [0002]    A number of techniques are known for clearing obstructions in coronary arteries. These include by-pass surgery, the use of a “balloon” to expand the arterial wall in the region of the obstruction, the use of a cutter passed along the artery to remove the obstruction and the use of a drill which is also passed along the artery to pulverize the obstruction. By-pass surgery is a major operation and is expensive. The use of surgical instruments in the above-described alternate methods involves the risk that the instrument which is passed along the artery will puncture the arterial wall during use or during passage along the artery to the location at which the obstruction is to be cleared. Additionally, the use of a drill which pulverizes the obstruction involves the risk of the pulverized material lodging in another part of the body and causing damage there.  
           [0003]    It is an object of the present invention to provide a surgical instrument for clearing obstructions in ducts in which the above described problems can be obviated or mitigated.  
         SUMMARY OF THE INVENTION  
         [0004]    According to the present invention, there is provided a surgical instrument for clearing obstructions in ducts, comprising a body having a forward end defined by a sleeve, a cutter member mounted in the sleeve for rotation relative thereto, and elongate flexible drive means connected to the cutter member and extending rearwardly of the body to enable rotation of the cutter member, wherein the cutter member includes an outer cutting edge cooperating with the sleeve to produce a circular cut upon rotation of the cutter member in use.  
           [0005]    With the above-described surgical instrument, the sleeve assists in preventing accidental penetration of the wall of the duct by the cutter member during use or when being manoeuvered into position for use. The instrument can be used percutaneously as a non-operative device.  
           [0006]    It is preferred for the cutter member to include a blade having a helical outer cutting edge, and particularly preferred for the cutter member to take the form of a screw whose outer surface cooperates with the sleeve to produce the circular cut. Such screw also serves, upon rotation, to transport material from the obstruction into the body of the instrument. Conveniently, a chamber is provided in the body to receive such material which can then be completely removed from the duct upon removal of the body of the instrument therefrom. Thus, the material which has been cleared away is completely removed from the duct.  
           [0007]    In a particularly preferred embodiment, the forward end of the cutter member protrudes through the forward open end of the body. To reduce the risk of such cutter member accidentally penetrating the wall of the duct in use or whilst it is being manoeuvred into position along a duct, it is convenient for the forward end of the cutter member to be relatively blunt. However, in the case where the cutter member takes the form of the screw, it is preferred for it to have a tapered forward end protruding from the forward end of the sleeve. Such tapered forward end can than serve to penetrate the obstruction and draw the body along the duct upon rotation of the screw. This is considered to be a particularly effective way of advancing the body along the duct since it does not require the body of the instrument to be pushed along the duct.  
           [0008]    The elongate flexible drive means preferably takes the form of a cable or the like mounted for rotary movement within a relatively fixed, flexible sleeve. The flexible sleeve preferably takes the form of a hollow helical spring which is preferably provided with a continuous cover of sheath to provide a smooth external surface for ease of passage along the duct to be cleared.  
           [0009]    The body and the cutter member may be provided with a passage extending axially therethrough so that the body and cutter can be mounted on an elongate guide wire or the like. In use, it will be appreciated that such guide wire can be passed along the duct relatively easily because of its small diameter, and then the body can be passed along the duct whilst being guided by the wire so as to facilitate safe passage along the duct to the site of the obstruction. The surgical instrument will normally be used whilst the patient is conscious, and its progress along the duct can be monitored by x-ray inspection.  
           [0010]    In the case of surgical instruments according to the present invention designed for clearing arterial obstructions, the external diameter of the body will be in the region of 2 to 4 mm. The instrument can be used for bioducts generally.  
           [0011]    Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:— 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is an axial section through a first example of surgical instrument according to the present invention;  
         [0013]    [0013]FIGS. 2 and 3 are schematic axial sections through parts of second and third examples of surgical instruments according to the present invention;  
         [0014]    [0014]FIG. 4 is a schematic view illustrating a detail of the instrument of FIG. 3; and  
         [0015]    [0015]FIG. 5 is an axial section through part of a fourth example of surgical instrument according to the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    Referring now to FIG. 1, the surgical instrument illustrated therein is for clearing obstructions in coronary arteries. The instrument comprises a body  10  formed in two parts consisting of a hollow bushing  12  and sleeve  14  extending forwardly of the bushing  12 . The sleeve  14  has an open forward end  16  and a rear end which has been inwardly deformed so as to define a stop  18 . The stop  18  abuts against a step  20  provided on the external surface of the bushing  12  between a larger diameter forward end portion  22  and a smaller diameter rear end portion  24  thereof. The sleeve  14  is slidable rearwardly (i.e. to the left as viewed in the drawing) relative to the bushing  12  from an extended position in which (a) the stop  18  abuts against step  20  and (b) a pip  26  formed by localized inward deformation of the sleeve  14  engages in an annular groove  28  formed in the surface of the larger diameter forward end portion  22  of the bushing  12 . The engagement of the pip  26  in the groove  28  serves as a releasable detect mechanism for retaining the sleeve  14  in its extended condition as illustrated in the drawing.  
         [0017]    The surgical instrument further includes a cutter member  30  which is mounted in the body  10  via a stepped root portion  32 . The root portion  32  engages in a stepped bore of the bushing  12  and is retained therein by an inwardly upset annular lip  34 . The root portion  32  is rotable relative to the bushing  12  which acts as a bearing therefor. The root portion  32  carries a tapered shaft  36  which projects forwardly and axially of the sleeve  14  so as to pass through the open end  16  of the sleeve  14 . At a position which is spaced forwardly of the bushing  12 , the shaft  36  provided with integral screw threading  38  thereon. The screw threading  38  starts within the sleeve  14  and extends forwardly to the tip of the shaft  36 , the screw threading tapering inwardly over a region thereof which is disposed externally of the sleeve  14 . The forward end of the screw threading  38  and the forward end of the shaft  36  are relatively blunt and have no sharp edges whereby to minimize risk of inadvertent penetration of the arterial wall during use. The portion of the screw threading  38  which is disposed within the sleeve  14  has a peripheral surface which is relatively sharp and which is in close sliding contact with the internal wall surface of the sleeve  14 .  
         [0018]    The root portion  32  has a blind axial bore  40  therein in which one end of a flexible drive cable  42  is firmly secured. The drive cable  42  extends through a flexible outer sleeve or sheath  44  and is rotatable relative thereto. In the drawing, only a short length of the cable  42  and sheath  44  are illustrated. In practice, these latter two parts will extend for a considerable distance rearwardly of the body  10 , with the cable  42  terminating externally of the sheath  44  in a formation which facilitates manual rotation of the cable  42  at a remote location.  
         [0019]    In use, the body  10  including the cutter member  30  is passed along an artery of a conscious patient until it meets the obstruction to be cleared. This is effected by appropriately manoeuvering the body  10  using the sheath  44  with the aid of an x-ray camera. When the body  10  has been manoeuvred into the correct position along the artery, the cable  42  is rotated relative to the sheath  44  so as to cause the cutter member  30  to rotate in a direction in which it causes the forward end of the screw threading  38  to dig into the material of the obstruction and thereby draw itself and the body  10  along the artery and further into the obstruction. A circular cutting action is provided by mutual cooperation of (a) the outer cutting edge of that portion of the screw threading  36  which is disposed within the sleeve  14  and (b) the inner peripheral wall of the sleeve  14 . The cut material is carried between the flights of the screw threading  38  within the sleeve  14  to be discharged into collection chamber  46  disposed within the sleeve  14  and between the screw threading  38  and the bushing  12 . When it is seen on the x-ray camera that the obstruction has been cleared, rotation of the cable  42  is stopped and the body  10  is withdrawn by employing a pulling action on the sheath  44 . Once the body  10  has been removed from the artery  10 , material which has been collected in the chamber  46  can be easily removed upon retraction of the sleeve  14  relative to the bushing  12 .  
         [0020]    It will be appreciated that, because the cutting action takes place by cooperation of the screw threading  38  with the internal wall of the sleeve  14 , there is a minimum of risk that the wall of the artery will be inadvertently penetrated. In order to assist insertion of the body  10  and to minimize risk of damage to the artery wall, the leading edge of the sleeve  14  around the open end  16  is conveniently radiussed. In order to facilitate withdrawal of the body  10  along the artery, the rear end of the smaller diameter portion  24  of the bushing  12  and the rear edge of the sleeve  14  adjacent the stop  18  are both appropriately tapered.  
         [0021]    Referring now to FIG. 2, the surgical instrument illustrated therein is similar to that of FIG. 1 and similar parts are accorded the same reference numerals but in the  100  series. In this example, cutter member  130  is rounded at its forward end to minimize risk of arterial wall penetration in use. Sleeve  114  of body  110  is flexible, but is fitted with a metal ring  150  to define open forward end  116 . The rotary cutting action takes place between cutter member  130  and metal ring  150 . The body is internally screw-threaded at its rearward end to engage with external screw-threading on the forward end of sheath  144 . The screw-threading is directed so that the screw-threaded joint between the body  110  and the sheath  144  tends to be tightened during forward rotation of the cutter member  130  in use. The sheath  144  may have a smaller diameter than the body  110 . At its rear end, the sheath  144  is provided with a formation  152  to facilitate gripping of the instrument during use. Cable  142  passes out of the rear end of the sheath  144  and is connected to a hand wheel  154  (only schematically shown). The cable  142  is connected to shaft  136  by connecter  156  which also acts as a bearing.  
         [0022]    Referring now to FIGS. 3 and 4, the surgical instrument illustrated therein is similar to that of FIG. 2 and similar parts are accorded the same reference numerals but in the  200  series. In this example, cutter member  230  and shaft  236  have aligned axial passages therethrough, and the cable  142  is replaced by a flexible tube  242  which is joined to the shaft  236  at connector  256  which is hollow. These axial passages typically have a diameter of about 0.4-0.46 mm In use, a guide wire  258  typically having a diameter of about 0.36 mm is passed into and along the artery to a position beyond the location at which the obstruction exists. The body  210  can then be passed along the artery to the location of the obstruction whilst being continually guided by the wire  258  so as to minimize the risk of penetration of or damage to the wall of the artery.  
         [0023]    Referring now to FIG. 5 of the drawings, the surgical instrument illustrated therein is similar to the preceding examples and similar parts are accorded the same reference numerals but in the  300  series. In this example, sheath  344  has a diameter which is substantially less than that of body  310  except for an enlarged forward end portion  360  by which it is screw-engaged with body  310 . A bushing  356  around cable  342  assists in correctly locating the latter within the portion  360 . A washer  362  in the body  310  and lodged between the portion  360  and an internal rib  364  serves to limit passage of debris into the sheath  344  from chamber  346  and can be readily removed upon detachment of the body  310  from the portion  360  to facilitate removal of debris from the chamber  346  after use.