Ultrasonic snare for excising tissue

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.

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.

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 125a 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 125a 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 110a and 110b, 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 110a and 110b 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'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.