Abstract:
A surgical instrument for excising includes an endoscopic portion with an ultrasonically vibratable loop. The loop is positioned around the tissue and closed, whereupon ultrasonic energy is transmitted to the loop to cut and cauterize the body tissue. The apparatus and method described herein are particularly suitable for colonoscopic polypectomy procedures.

Description:
This application claims the benefit of Provisional No. 60/095,420 filed Aug. 5, 1998. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a surgical instrument assembly for use in excising body tissue from an internal body cavity, and more particularly to a snare device for removing polyps. 
     2. Background of Related Art 
     Colonoscopic polypectomy is a commonly used method for removing and optionally retrieving polyps from the colon. Such operations are performed so that the polyps can be examined by a pathologist for malignancy. Devices for such removal and retrieval of tissue are disclosed and described in U.S. Pat. Nos. 5,486,182, 5,336,227, 5,201,740 and 5,190,542, to Nakao et al. 
     Typically, a snare device is used which has a distal loop of wire which can be inserted into the colon and positioned around the base of the polyp. Thereafter, the loop is closed around the stalk of the polyp to sever the tissue. 
     One complication which can develop with simple mechanical excision of the polyp is excessive bleeding. In order to reduce the amount of bleeding that can result from severing the polyp from its stalk some surgical apparatus employ an electrocautery snare. The electrocautery device can be monopolar as disclosed for example in U.S. Pat. No. 5,158,561, or bipolar as disclosed for example in U.S. Pat. Nos. 5,026,371 and 4,905,691. Monopolar devices generally use radio frequency (“rf”) current. 
     Nevertheless complications can occur during electrocautery polypectomy procedures. For example, colonic perforation can result from the electrocautery current travelling via blood vessels to the base of the polyp and the wall of the colon, from the current travelling through the head of the polyp to the opposite wall, and from the accidental contact of the active electrode with surrounding tissue. Also, unobserved damage can occur from microperforations of the bowel wall and from pooled body fluids which contact the electrified wire and carry the current along unintended pathways to locations outside the field of view. 
     There yet remains a need for a polypectomy snare which provides the advantage of tissue cutting and coagulation while avoiding the disadvantages of electrocautery current. 
     SUMMARY 
     A surgical instrument is provided herein for cutting body tissue. The instrument includes a housing, an endoscopic portion including an ultrasonically vibratable element at least partially extending from the housing, an actuator movably connected to the housing and fixedly attached to the ultrasonically vibratable element, and an ultrasonic transducer operatively connected to the ultrasonically vibratable element. 
     The ultrasonically vibratable element possesses a loop at a distal end, the loop being movable between an open configuration for the reception of the body tissue therethrough and a closed configuration. Movement of the actuator between a first position and second position effects corresponding movement of the loop between the open configuration and closed configuration. 
     Also provided herein is a method for surgically removing polyps by employing the surgical instrument described herein. 
     The surgical instrument described herein advantageously limits bleeding during polypectomy operations while providing a greater margin of safety to the patient. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various embodiments are described below with reference to the drawings wherein: 
     FIG. 1 is a perspective view of the ultrasonic system for excising body tissue; 
     FIG. 2 is an exploded perspective view of the hand held ultrasonic surgical instrument including the ultrasonic snare; 
     FIG. 3 is a side view illustrating the use of the apparatus in conjunction with a cannula assembly; 
     FIG. 4 is a cut-away side view of the hand-held ultrasonic surgical instrument in an initial configuration; 
     FIG. 4A is a cutaway perspective view of the colon showing the placement of the snare loop around a polyp; 
     FIG. 5 is a sectional side view of the hand-held ultrasonic surgical instrument in a closed configuration; 
     FIG. 5A is a cutaway perspective view of the colon showing the closure of the snare loop around the base of the polyp; and 
     FIG. 6 is a cutaway perspective view showing the colon with the polyp removed. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The apparatus of the present disclosure is intended to snare body tissue and deliver ultrasonic energy to the snared tissue for the purpose of excising the tissue while limiting bleeding. The apparatus may be used in any minimally invasive surgical procedure where removal of tissue growths is desired, and it has particular application for the removal of polyps from the colon, although the apparatus is not limited to such application. 
     The apparatus is particularly intended to be used in conjunction with an endoscope such as a cystoscope, fiber scope, laparoscope, urethroscope or the like, to provide the scope with ultrasonic treatment capabilities. More specifically, the apparatus is at least partially insertable within the working channel of an endoscope which has been positioned in the body to access a targeted tissue area to treat the desired tissue. 
     Referring to FIG. 1, the ultrasonic system  10  for excising body tissue includes a hand-held ultrasonic surgical instrument  100  including a body portion  110  and an endoscopic snare portion  120 . The ultrasonic system  10  further includes a control module  160 , and optionally a pedal switch  170 . 
     Referring also now to FIG. 2, endoscopic portion  120  includes a flexible wire snare  121  terminating in a distal loop  122 . Snare  121  extends through tubular outer sheath  125  having a cylindrical retainer  126  at the proximal end thereof. The snare wire is preferably fabricated from a biocompatible metal alloy such as stainless steel, titanium, and alloys of titanium, aluminum and vanadium, and may optionally be coated with an electrically insulative polymeric material such as polyimide. Snare  121  is slidably disposed within sheath  125  and is movable between a distal position wherein loop  122  is outside the distal edge  125   a  of sheath  125  and resiliently expanded to an open configuration, and a proximal position wherein loop  122  is at least partially withdrawn into outer sheath  125  and cammed by the distal edge  125   a  of sheath  125  into a closed configuration. Sheath  125  can be fabricated from a flexible plastic or metal alloy. 
     The endoscopic portion  120  is connected to the body portion  110 . The left and right body halves  110   a  and  110   b , respectively, can be fabricated from polymeric resin by any suitable method such as, for example, injection molding, and can be joined to form body portion  110  by solvent welding, adhesive bonding, heat welding or any other appropriate method. When joined, left and right body halves  110   a  and  110   b  define an axially extending distal channel  113  having a recess  114  configured and dimensioned for reception of retainer portion  126  of outer casing  125 , an interior chamber  115 , a proximal channel  116 , and proximal cavity  117 . Handle  111  of the body portion  110  includes a grip  112  for the user&#39;s fingers. 
     Clamp  150  includes left and right halves  151  and  152 , respectively, each having a laterally extending boss  153  and  154 , respectively. When joined, halves  151  and  152  define an axial channel  155  through which wire snare  121  is disposed. Clamp  150  frictionally engages and securely holds snare  121 . 
     Trigger  130  is pivotally mounted to body portion  110  by means of a pin  138  which extends laterally through aperture  118  in the body portion and through aperture  137  in the trigger  130 . The body  131  of the trigger is elongated and terminates at one end at ring portion  132  adapted to receive the finger of a user. At the end opposite ring  132 , body  131  includes left and right projections  135  and  136 , respectively, which are separated by a space into which clamp  150  is received. Projections  135  and  136  each include an elongated aperture  133  and  134  respectively, which are adapted to receive a respective one of bosses  153  and  154 . 
     The ultrasonic transducer  140  includes a transducer unit  141  having a distal plug portion  142  which is adapted to engage and be received into proximal cavity  117  of the body portion  110 . Optionally, the distal plug portion  142  can frictionally engage proximal cavity  117  or may alternatively be secured by, for example, a bayonet type mounting feature or screw-in type mounting. The ultrasonic transducer  140  includes a transducer horn actuated by one or more piezoelectric crystals. Snare wire  121  extends through opening  143  in the ultrasonic transducer  140  and is operatively connected to the transducer horn. The piezoelectric crystals are electrically connected to a control module  160  by means of a conductive cable  145 . The control module  160  provides a regulated power supply to the ultrasonic transducer  140  and can optionally be actuated by a pedal switch  170  via cable  164 . Cable  162  supplies power to the control module  160  from a standard electrical outlet. The ultrasonic transducer  140  causes linear oscillation of the wire snare  121  at frequencies above about 20 kHz, typically about 30 kHz to about 50 kHz. The ultrasonic oscillations of the wire snare generate shear waves which facilitate cutting of tissue by fragmenting cellular material. 
     The ultrasonic energy advantageously promotes clotting of blood. The high frequency shear waves induced by the ultrasonic vibrations cannot be supported by body tissue. Therefore, the energy of the shear waves is absorbed by the surrounding tissue and dissipated in the form of heat. This promotes fibrin formation and clotting of blood. Damage to underlying tissue is minimized because the shear waves do not travel far from the vicinity of the cutting site. 
     Referring now to FIG. 3, use of the ultrasonic snare assembly  100  in conjunction with an endoscope is shown. An endoscope suitable for use with the apparatus of the present disclosure is a cystoscope such as the ACN Cysto Nephroscope, which is available from Circon ACMI. 
     Cystoscope  200  includes handle  202  and a flexible elongated portion  204  connected to the handle  202  and extending distally therefrom. Cystoscope  200  incorporates an optical system to permit viewing of the tissue to be treated. The optical system preferably consists of flexible fiber optic bundles (not shown) which are accommodated within a longitudinal bore extending through the elongated portion  204  of the scope  200 . The fiber optic bundles extend to eyepiece  208  where the surgeon can view the image transmitted by the optical system. 
     Cystoscope  200  also includes an illumination system which provides illuminating light to the targeted tissue area. The illumination system includes a plurality of optical fibers (not shown) which are accommodated within a plurality of longitudinal channels (not shown) of elongated portion  204  and extend within handle  202  where they terminate at illumination coupler  212 . Illumination coupler  212  is connectable to a conventional light source as is known in the art. Cystoscope  200  further includes a working channel extending through flexible elongated portion  204  and terminating at channel port  216  of handle  202 . The working channel is adapted to receive various surgical instrumentation through channel port  216  to permit the performance of surgical procedures at the distal end of the cystoscope  200 . 
     In use the cystoscope flexible elongated portion  204  is inserted into the colon of the patient. The endoscopic portion  120  of the ultrasonic snare assembly  100  is inserted through channel port  216  of the cystoscope. 
     Referring now to FIGS. 4 and 4A, the loop  122  is positioned around polyp  501  within the colon  500  of the patient. The ultrasonic surgical instrument  100  is initially in the configuration shown in FIG.  4 . Clamp  150  and trigger  130  are in their respective initial positions. 
     Referring now to FIGS. 5 and 5A, the snare loop  122  is tightened around polyp  501  by pivoting trigger  130  clockwise (as shown), which pulls clamp  150  and the snare wire  121  proximally. The elongated configuration of slot  153  accommodates the arcuate motion of the upper end of trigger  130  by permitting the bosses  153  and  154  of clamp  150  to slide along the length of slot  133 . This permits the clamp to be moved linearly. The user can then apply ultrasonic energy to the snare wire  121  to facilitate the cutting of the polyp. As shown in FIG. 6 after the main portion of the polyp is removed, there remains the base area of the polyp cut and cauterized by the ultrasonic snare. Ultrasonic cauterization limits the amount of bleeding while reducing the risk of unintended and perhaps unobserved damage to body tissue. 
     Although shown for removing polyps it should be understood that the ultrasonic instrument  100  could alternatively be used in other surgical procedures. 
     It will be understood that various modifications may be made to the modifications shown herein. For example, the body portion  110  can be fabricated from various metal alloys, as well as from various polymers such as acrylics, polycarbonates, and the like. Therefore, the above description should not be construed as limiting but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.