Abstract:
A surgical apparatus is provided having a first instrument and a second instrument which are independently operable, but may be used in tandem. The first instrument may comprise a needle and the second instrument may comprise a snare for cutting, excising, or trapping tissue. An actuator extends the needle a fixed first length relative to a distal end of the catheter for independently extending or retracting the second instrument a variable second length relative to the catheter distal end. The needle may be biased to retract relative to the distal end of the catheter. The actuator has a support and a slider. The slider is connected to the support for movement in opposite directions relative the support to allow freedom of action. The first instrument is secured to the support and rail, and the second instrument is secured to the slider. A rail enables independent but non-simultaneous sliding movement of the first instrument, or needle, while the slider facilitates independent operation of the second instrument, or snare.

Description:
This application is a continuation of 08,633,958 filed Apr. 15, 1996 now U.S. Pat. No. 5,947,978. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to surgical apparatus including a pair of instruments, sheathing means for the instruments and actuating means for extending one or the other instrument from the sheathing means, and more particularly to such apparatus which is a surgical combination inject and snare apparatus. 
     Commonly owned copending U.S. patent application Ser. No. 08/248,504, filed May 24, 1994, now U.S. Pat. No. 5,542,948, discloses surgical apparatus comprising a first instrument (which may be an injection needle), a second instrument (which may be a snare) and sheathing means (such as a catheter) for sheathing both instruments. Actuator means are provided for simultaneously extending the first instrument relative to the distal end of the sheathing means in a first direction and retracting the second instrument in an opposed second direction relative to the distal end of the sheathing means, and for simultaneously extending the second instrument relative to the distal end of the sheathing means in the first direction and retracting the first instrument in the second direction relative to the distal end of the sheathing means. In other words, the actuator means extends one of the two instruments while simultaneously retracting the other instrument. 
     The patented apparatus is used by inserting the distal tip thereof into a patient with both the first and second instruments being in an intermediate position, wherein both are covered by the sheathing means. When the distal tip of the sheathing means is properly positioned, the first instrument (typically an injection needle) is extended beyond the sheathing means and into an adjacent polyp. Fluid is then introduced into the polyp causing it to project further inwardly from the wall. At this point the first instrument is withdrawn, and the second instrument (typically a snare) is extended and used to snare the inwardly protruding polyp. This snare may be used simply for physical cutting of the polyp, or it may be electrified to facilitate separation of the polyp from the wall with minimal bleeding. The detached polyp may be withdrawn through the distal tip of the surgical apparatus, or it may be trapped within the interior of the sheathing means to facilitate its withdrawal with the distal tip of the surgical apparatus. 
     The aforementioned surgical apparatus is susceptible to improvement. For example, in the aforementioned surgical apparatus the force which must be exerted by the surgeon to extend the snare must also include the force required to overcome the friction involved in dragging the injection needle proximately through the sheathing means. A surgeon would be able to manipulate the snare with greater accuracy if he had to exert only the force required to move the snare, and not simultaneously also the force required to move the injection needle. 
     Further, the surgeon has to manually maintain the injection needle in the extended position during the entire time that it takes to inject sufficient fluid therethrough to cause the polyp to project inwardly from the wall, this step being unnecessarily time-consuming to a surgeon who might have better use for at least one of his hands during this interval if he could lock the needle into an injection position. 
     Ideally, it should not be necessary for the surgeon to manually retract the injection needle when it is no longer needed, and he should be able to rely on some type of automatic needle retraction mechanism which he could actuate. 
     The injection needle, like the snare, can be extended a variable and sizable distance distally relative to the distal tip of the sheathing means. However, while it is desirable for the snare to be extendable a variable and sizable distance up to about 5 inches, it is better for the injection needle to be extendable only about 0.75 inch, just sufficient to reach the interior of the polyp. A shorter throw of the needle would also enable a greater curve at the distal end of the sheathing means without danger of the needle becoming caught in the sheathing means (i.e., the catheter) during extending of the needle. 
     Further, the possibility exists that the injection needle will accidentally be extended when the surgeon&#39;s intent is to extend the snare. Thus it would be desirable to have a safety mechanism which had to be disabled in order to enable extension of the needle. 
     Surgeons acquire great expertise in utilizing hypodermic-type handles (that is, surgical apparatus operated by the first three fingers of a hand), but are typically less familiar with the wheel arrangement of the patented apparatus which must be rotated, say, to withdraw the injection needle and extend the snare. 
     Accordingly, it is an object of the present invention to provide surgical apparatus, such as a combination inject and snare apparatus, wherein the movement of the first instrument (typically an injection needle) is independent of the movement of the second instrument (typically a snare), thereby to reduce the force which must be exerted during either movement. 
     Another object is to provide such apparatus which in one embodiment maintains the injection needle in the extended position without further action on the part of the surgeon. 
     A further object is to provide such surgical apparatus which in one embodiment provides a mechanism for automatic retraction of the needle when it is no longer required. 
     It is another object to provide such surgical apparatus which in one embodiment incorporates a locking mechanism which must be unlocked in order to enable extension or retraction of the needle. 
     It is also an object of the present invention to provide such surgical apparatus which in one embodiment enables the snare to be extended a variable and sizeable distance while the injection needle is extendable only a much shorter distance, but typically the full extent of the shorter distance. 
     SUMMARY OF THE INVENTION 
     It has now been found the above and related objects of the present invention are obtained in a novel surgical apparatus. The novel surgical apparatus comprises a first instrument (typically, an injection needle), a second instrument (typically, a snare), and sheathing means for sheathing the first and second instruments, the sheathing means having a proximal end and a distal end. An actuator means is provided for manually extending the first instrument a substantially fixed first length (preferably about 0.75 inch) relative to the distal end of the sheathing means and for independently extending or retracting the second instrument a variable second length relative to the distal end of the sheathing means. Biasing means bias the first instrument into retracting relative to the distal end of the sheathing means. 
     In a preferred embodiment of the surgical apparatus, the actuator means comprises a support assembly, a slider assembly and a rail assembly. The support assembly has a support and means for grasping thereof, the first instrument being secured to the support for movement therewith. The slider assembly has a slider and means for grasping thereof, the slider being secured to the support for sliding movement in opposite directions relative thereto, and the second instrument being secured to the slider for movement therewith. The rail assembly has rail means for enabling independent but non-simultaneous sliding movement of the first instrument in opposite directions relative to the distal end of the sheathing means, the rail means being longitudinally slideable with respect to the support and operatively connected to the slider. Thus, forcible movement of the slider and the rail means to one extreme relative to the support causes the first instrument to extend relative to the distal end of the sheathing means against the biasing means, while release of the slider and the rail means enables the biasing means to return the slider and the rail means from the one extreme, thereby to cause the first instrument to retract. Also, movement of the slider towards the opposite extreme relative to the support causes the second instrument to extend relative to the distal end of the sheathing means. 
     In a particularly preferred embodiment, movement of the slider towards the one extreme relative to the support causes the second instrument to retract relative to the distal end of the sheathing means. The surgical apparatus additionally includes first automatically engaging and manually disengeable lock means for precluding forcible movement of the slider to the one extreme relative to the support once the biasing means returns the slider from the one extreme, whereby manual disengagement of the lock means is required prior to extension of the first instrument relative to the distal end of the sheathing means. The surgical apparatus additionally includes second automatically engaging and manually disengeable lock means for precluding the biasing means from moving the slider from the one extreme relative to the support after forcible movement of the slider to the one extreme, whereby manual disengagement of the second lock means is required prior to retraction of the first instrument relative to the distal end of the sheathing means. 
     The present invention also encompasses surgical apparatus comprising a first instrument extendable in a first direction and retractable in a second direction, a second instrument extendable in the first direction and retractable in the second direction, and sheathing means for sheathing the first and second instruments, the sheathing means having a proximal end and a distal end. Means are provided to bias the first instrument in the second direction. A support assembly has a support and means for grasping thereof, the first instrument being secured to the support for movement therewith. A slider assembly has a slider and means for grasping thereof, the slider being secured to the support for sliding movement in opposite directions relative thereto and the second instrument being secured to the slider for movement therewith. A rail assembly has rail means for enabling independent but non-simultaneous sliding movement of the first instrument in opposite directions relative to the distal end of the sheathing means, the rail means being longitudinally slideable with respect to the support and operatively connected to the slider. Thus, forcible movement of the slider and the rail means to one extreme relative to the support causes the first instrument to extend relative to the distal end of the sheathing means against the biasing means, while release of the slider and the rail means enables the biasing means to return the slider and the rail means from the one extreme and the first instrument to retract, and movement of the slider towards the opposite extreme relative to the support causes the second instrument to extend relative to the distal end of the sheathing means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The above and related objects, features and advantages of the present invention will be more fully understood by reference to the following detailed description of the presently preferred, albeit illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawing wherein: 
     FIGS. 1 and 2 are fragmentary top plan and side elevational views, respectively, of surgical apparatus according to the present invention, in a “neutral” or “needle in, snare in” orientation; 
     FIGS. 3,  4 , and  5  are fragmentary top plan, side elevational and bottom plan views, respectively, of the surgical apparatus in a “needle in, snare out” orientation; 
     FIGS. 6 and 7 are fragmentary sectional views thereof, taken along the lines 6—6 of FIG. 4 and 7—7 of FIG. 6, respectively; 
     FIGS. 8,  9  and  10  are fragmentary top plan, side elevational and bottom plan views, respectively, of the surgical apparatus, in a “needle out, snare in” orientation; 
     FIGS. 11 and 12 are fragmentary sectional views thereof, taken along the lines 11—11 of FIG. 10 and 12—12 of FIG. 11, respectively; and 
     FIGS. 13A,  13 B and  13 C together form an exploded top plan view thereof separated into independently moveable assemblies. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The improved surgical combination apparatus according to the present invention may incorporate various first and second instruments. While the apparatus shown and described herein is a surgical combination inject and snare apparatus, wherein the first instrument is an injection needle and the second instrument is a snare, those skilled in the surgical arts will readily appreciate that the principles of the present invention have applicability to various other surgical combination apparatus. 
     Referring now to FIGS. 1 and 2, therein illustrated is a surgical combination apparatus according to the present invention, generally designated by the reference numeral  10 . More particularly, the surgical apparatus  10  is a surgical combination inject and snare apparatus including, as a first instrument, a hollow injection needle  12  (best seen in FIGS. 8-12) and, as a second instrument, a snare  14  (best seen in FIGS.  3 - 7 ). In addition to the needle  12  and snare  14 , the surgical apparatus  10  includes sheathing means  16  for sheathing the first and second instruments  12 ,  14 , actuator means, generally designated  18 , for manually controlling movement of the various elements  12 ,  14  relative to one another, and biasing means  20 . 
     The sheathing means  16  is a conventional catheter, formed of a flexible plastic and defining both an enlarged proximal end  30  fixedly secured to the actuator  18  and a distal or free end  32  for insertion into a patient. 
     As will become clearer hereinafter, the actuator means  18  includes means for manually extending the first instrument or needle  12  a substantially fixed first length, relative to the distal end  32  of the sheathing means  16 , and for independently but non-simultaneously extending or retracting the second instrument or snare  14  a variable second length, relative to the distal end  32  of the sheathing means  16 . 
     The biasing means  20  may be a conventional spring for biasing the first instrument or needle  12  into retracting relative to the distal end  32  of the sheathing means  16 . 
     The actuator means  18  and biasing means  20  together enable the first and second instruments  12 ,  14  to be both extended and retracted, relative to the distal end  32  of the sheathing means  16 . 
     Turning now in greater detail to the actuator means  18 , broadly speaking the actuator means  18  comprises a support assembly generally designated  40 , a slider assembly generally designated  44 , and a rail assembly generally designated  50 . 
     More particularly, as best seen in FIG. 13A, the axially or longitudinally extending rigid support assembly  40  comprises a support  41  and means  42  for grasping thereof, such as a thumb ring at one end. The first instrument or hollow injection needle  12  is secured to the support  41  by a hollow, flexible wire  43  for movement therewith as a unit. The support  41  at its proximal end, adjacent the grasping means  42 , defines an interior longitudinally-extending channel  60  therethrough. The support  41  at its distal end, adjacent the sheathing means  16 , defines a hollow cylinder  62  with a closed proximal end and an open distal end. The hollow, flexible wire  43  passes through cylinder  62  and provides fluid communication between needle  12  and hollow tubing  68 , the latter being adapted for connection to a fluid source (not shown) and secured to support  41  for movement therewith. 
     As best seen in FIG. 13B, the slider assembly  44  comprises a slider  45  and means  46  for grasping thereof, such as a pair of finger rings on opposite sides thereof. The slider  45  is secured to the support assembly  40  for sliding longitudinal movement therealong in both directions. The second instrument or snare  14  is secured to the slider  45  by a typically solid, flexible electrically conductive wire  47  for movement therewith as a unit. An electrical contact  66 , adapted for conductive communication with a power source (not shown), is secured to slider  45  for movement as a unit therewith and provides for the communication of electrical energy to sheath  14  via conductive wire  47  passing through channel  60  and cylinder  62 . 
     The support  41  and channel  60  of support assembly  40  are configured and dimensioned to receive the slider  45  of slider assembly  44  within the channel  60  and the grasping means  46  of slider assembly  44  laterally outwardly of the support  41 , thereby permitting relative movement of the slider  45  and its finger rings  46  relative to the support  41  and its thumb ring  42 . As the needle  12  is connected to the support assembly  40  by a flexible wire  43  and the snare  14  is connected to the slider assembly  44  by a flexible wire  47 , the needle  12  and snare  14  are in turn capable of relative, albeit non-simultaneous, motion. 
     As best seen in FIG. 13C, the axially or longitudinally extending rail assembly  50  is provided for enabling independent but non-simultaneous sliding movement of the first instrument or needle  12  in opposite directions relative to the distal end  32  of the sheathing means  16 . The rail assembly  50  includes a pair of parallel rail means  51  longitudinally slidable with respect to the support assembly  40 . 
     The proximal ends of the two rail means  51  each define a small outer lug  70  facing outwardly from the rail means  51  and a small inner lug  72  facing inwardly from the rail means  51  (toward the support  41 ). The inner lugs  72  are received within longitudinal recesses  75  on the outer surfaces of the rail means  51 . The outer lugs  70  act as a stop to limit relative proximal movement of the slider  45  relative to the rail means  51 . Accordingly, neglecting any locking means discussed hereinafter, a proximal movement of the slider  45  until it contacts the outer lugs  70  of the rail means  51  results in a retraction of the second instrument or snare  14  relative to the distal end  32  of the sheathing means  16 . Further proximal movement of the slider  45  causes a corresponding proximal movement of the rail means  51  along longitudinal recesses  75  (best seen in FIGS. 2 and 4) due to the engagement of the slider  45  and the outer lugs  72 , with a resultant exposure of the first instrument or needle  12  distally beyond the distal end  32  of the sheathing means  16 . 
     The distal ends of the two rail means  51  are secured together by a connector  74 . The distal end of the connector  74  tapers inwardly and defines a surface  76  adapted to receive the proximal end  78  of catheter  16 , such that the entire catheter  16  (including its distal tip  32 ) moves as a unit with the connector  74  and rail means  51 , and thus as a part of the rail assembly  50 . Rotatably secured to the proximal end of the connector  74  is a piston  80 , which is configured and dimensioned to be slidingly received within the interior of cylinder  62  (along with the spring  20 ) through the cylinder open distal end. The piston  80  is freely rotatable relative to the connector  74  over at least 45 degrees, but secured to the connector  74  for longitudinal movement as a unit. 
     It will be appreciated that the support assembly  40  of FIG. 13A, the slider assembly  44  of FIG.  13 B and the rail assembly  50  of FIG. 13C are each capable of independent sliding movement relative to one another, thereby to enable the unique motions of the present invention. 
     Movement of the slider assembly  44  toward the distal extreme relative to the support assembly  40  causes the second instrument or snare  14  to extend relative to the distal end  32  of the sheathing means  16 , as illustrated in FIGS. 3-7. Movement of the slider assembly  44  towards the proximal extreme relative to the support assembly  40  causes the second instrument or snare  14  to retract relative to the catheter distal end  32  of the sheathing means  16 , as illustrated in the neutral orientation of FIGS. 1-2. 
     Neglecting for the moment the various locking means provided relative to needle movement, as discussed hereinafter, forcible proximal movement of the slider assembly  44  and the rail assembly  50  to the proximal extreme relative to the support assembly  40  causes the first instrument or needle  12  to extend relative to the distal end  32  of the sheathing means  16  against the biasing means  20 , as illustrated in FIGS. 8-12. Release of the slider assembly  44  and rail assembly  50  enables the biasing means  20  to return the slider assembly  44  and rail assembly  50  distally from the proximal extreme, and the first instrument or needle  12  to retract into the sheathing means  16 , as illustrated in the neutral orientation of FIGS. 1-2. 
     Considering now the locking mechanisms, a lever  82  projects radially outwardly from the proximal end of the piston  80  and for rotational and longitudinal travel herewith is configured and dimensioned for travel (with the entire rail assembly  50 ) along the L-shaped pathway  64  formed within the side wall of cylinder  62 . The distal face  84  of piston  80  is at all times disposed within the interior of cylinder  62  (e.g., due to stop pins, not shown) and acts to maintain the spring  20  within the interior of cylinder  62 . However, the spring  20  in turn acts to bias the piston  80  for rotation. 
     Once the lever  82  is manually moved from transverse leg  646  into longitudinal leg  64   a,  and the rail assembly  50  then moved distally relative to the support assembly  40  (such that lever  82  travels distally along the longitudinal leg  64   a  and eventually leaves the confines of the longitudinal leg  64   a  of the L-shaped passageway  64 ), the spring  20  causes the piston  80  to rotate out of alignment with the longitudinal leg  64   a . Because the inner lugs  72  on rail means  51  preferably abut the distal end of the longitudinal recesses  75 , lever  82  cannot move distally (and the piston  80  is thus kept at least partially within cylinder  62  even in the absence of the aforementioned stop pins). Because the lever  82  abuts the distal end of the cylinder  62 , it cannot move proximally. Thus, longitudinal movement of the lever  82  (and thus the entire rail assembly  50 ) relative to the cylinder  62  (and thus the entire support assembly  40 ) is precluded until the lever  82  is manually rotated back into alignment with the longitudinal leg  64   a  of the L-shaped passageway  64  for distal movement therealong. 
     Similarly, once the lever  82  has been manually moved from in front of cylinder  62  to within longitudinal leg  64   a  of the L-shaped passageway  64 , and then moved proximally therealong (against the bias of spring  20 ) until it is aligned with the transverse leg  64   b  of the L-shaped slot  64 , the spring  20  forces the entry of the lever  82  into the transverse leg  64   b , thereby to preclude any relative movement longitudinally of the lever  82  (and thus the entire rail assembly  50 ) relative to the transverse leg  64   b  (and thus the entire support assembly  40 ). 
     Operation of the apparatus is very simple. Referring now to FIGS. 1 and 2, the apparatus  10  is illustrated therein a “neutral” or “needle in, snare in” orientation such as might be used for introduction of the catheter distal tip  32  to the desired location within the patient&#39;s body. Neither the needle  12  nor the snare  14  project distally of the catheter distal tip  32  where they might interfere with the threading of the tip  32  through the patient&#39;s body. The piston  80  is disposed almost entirely distally of the cylinder  62  with the lever  82  resting on the distal face of the cylinder  62 . The proximal end of slider  45  is adjacent to or contacting the outer lugs  70  of the rail means  51 . 
     Referring now to FIGS. 8-12, the apparatus  10  is illustrated therein in the “needle out, snare in” orientation. Once the distal end  32  of catheter  16  has been properly located within the patient, the lever  82  is rotated until it is aligned with the longitudinal leg  64   a  of the L-shaped passageway  64  of cylinder  62 . At the same time the finger grips  46  and thumb grip  42  are used to move the slider  45  proximally first against the outer lugs  70  of the rail means  51  and then even further proximally until the rail means  51  (and thus the entire rail assembly  50 ) moves proximally. The inner lugs  72  of the rail means  51  (best seen in FIG. 13C) slidingly travel distally within the longitudinal recesses  75  on the outer surfaces of the support  41  (best seen in FIGS.  2  and  4 ). At this point, as best seen in the FIGS. 8 and 9, the finger grips  46  are closely disposed relative to the thumb grip  42 . 
     During the above-described movement of the rail means  51  proximally relative to the support  41 , the lever  82  travels along the longitudinal leg  64   a  and the piston  80  progressively enters the hollow cylinder  62 . Finally, the lever  82  becomes aligned with the transverse leg  64   b  and, under the influence of spring  20 , moves along the transverse leg  64   b,  thereby blocking any further longitudinal movement of the rail assembly  50  relative to the support assembly  40 . Typically, although not necessarily, there is still room within the longitudinal recesses  75  for further proximal movement of the rail assembly  50  relative to the support assembly  40  as the relative motion therebetween is best precluded by the interaction of the lever  82  and passageway  64  in order to achieve a locking effect. The length of longitudinal leg  64   a  is preferably about 0.75 inch, although it may be shorter or longer depending upon the desired travel of the first instrument  12 . 
     Depending upon what one uses as the point of reference, in the “needle out, snare in” orientation, either the distal movement of the support assembly  40  relative to the rail assembly  50  results in a distal movement of the needle  12  relative to the catheter  16  or the distal movement of the rail assembly  50  relative to the support assembly  40  causes the catheter  16  to move proximally relative to the needle  12  such that the catheter distal tip  32  now exposes the distal tip of the needle  12 . In actuality, typically the catheter distal tip  32  is initially set against the polyp by the surgeon and the movement to the “needle out, snare in” orientation is effected by a forward movement of the support assembly  40  relative to the rail assembly  50 . The forward motion is driven and controlled by the thumb movement in thumb ring  42 , but it must first be enabled by the manual pivoting of lever  82  into alignment with the longitudinal leg  64   a  (i.e., unlocking of lever  82 ). In any case, it will be appreciated that once the lever  82  has traversed the length of the longitudinal leg  64   a , and then entered into the transverse leg  64   b  (under the influence of spring  20 ), the apparatus is locked in the “needle out, snare in” orientation. At this time, the desired fluid may be introduced into the polyp through hollow tubing  68 , hollow wire  43 , and needle  12  without further action on the part of the surgeon to maintain the injection needle  12  in place. On the other hand, it should also be appreciated that the lever  82  initially acted as a safety or locking mechanism, precluding any distal advancement of the needle  12  until the lever  82  was manually aligned with the longitudinal leg  64   a.    
     After sufficient fluid has been introduced into the polyp through hollow tubing  68 , wire  43 , and injection needle  12 , the fluid flow is terminated. Then the lever  82  need only be back rotated along transverse leg  64   b  until it is again in alignment with longitudinal leg  64   a  (i.e., again unlocked). At this point the energy stored in the compressed spring  20  will force piston  80  almost entirely out of the cylinder  62  and cause the piston  80  to rotate until lever  82  returns to its normal locked position outside of the passageway  64 . Further forward movement of the rail assembly  50  relative to the support assembly  40  is precluded by the abutment of the inner lugs  72  on the distal ends of the recesses. Due to the biasing of spring  20 , it is almost impossible to manually maintain piston  80  in an intermediate position within cylinder  62 —i.e., with the lever  82  in the middle of longitudinal leg  64   a —so that the needle/piston travel is typically for the full length of longitudinal leg  64   a.  Thus, the surgeon has only to release the thumb pressure exerted on thumb grip  42  and rotate lever  82  within the transverse leg  64   b ; thereafter, the apparatus automatically returns itself, under the influence of spring  20 , to the “neutral” orientation illustrated in FIGS. 1 and 2. 
     Referring now to FIGS. 3-7, the apparatus  10  is illustrated therein in the “needle in, snare out” orientation. Once the polyp has been injected with fluid from the injection needle  12 , the latter is returned to the neutral orientation. From there, the surgeon has only to move the slider assembly  44  distally relative to the rail assembly  50 . This is easily accomplished by separating the fingers in the finger grips  46  from the thumb in the thumb grip  42 . The abutment of the distal end of the slider  45  against the distal end of the channel  60  limits the forward movement of the slider  45  (and hence the slider assembly  44 ) relative to the now locked together supra-assembly formed by the support assembly  40  and the rail assembly  50 . It will be appreciated that the piston  80  and lever  82  and the cylinder  62  and passageway  64  play no role in the movement of the sheath  14  relative to the catheter distal end  32 . 
     The surgeon has only to manipulate reciprocatingly the finger grips  46  relative to the thumb grip  42  in order to cause distal emergence of the sheath  14 , trapping of the protruding polyp thereby, and withdrawal of the sheath  14  (either with or without the polyp) back into the catheter  16 . Electrical energy may be introduced into the sheath  14  via contact  66  and electrically conductive wire  47 . 
     To summarize, in the present invention the movement of the injection needle  12  is independent of the movement of the snare  14 , thereby to reduce the force which must be exerted during either movement. The interaction of the lever  82  and the passageway  64  provides a locking mechanism which must be manually unlocked in order to enable either extension or retraction of the needle, which enables the injection needle  12  to be maintained in the extended position without further action on the part of the surgeon, and which provides automatic retraction of the needle  12  when it is no longer required. The preferred embodiment allows the snare  14  to be extended a variable and sizable distance, limited essentially only by the length of channel  60 , while the injection needle  12  is extendable only a much shorter distance, typically limited by the length of the longitudinal leg  64   a . Typically the extension of the needle  12  is for the full extent of the short distance as the maintenance of the lever  82  within the longitudinal leg  64   a  is unstable due to the biasing of spring  20 . 
     Now that the preferred embodiments of the present invention have been shown and described, various modifications and improvements thereon will become readily apparent to those skilled in art. Accordingly, the spirit and scope of the present invention is to be construed broadly and limited only by the following claims, and not by the foregoing specification.