Abstract:
Ultrasonic instruments, and particularly solid core ultrasonic instruments, are advantageous because they may be used to cut and/or coagulate organic tissue using energy in the form of mechanical vibrations transmitted to a surgical end-effector at ultrasonic frequencies. The present invention provides a surgical instrument including force feedback system, in a closed loop arrangement that modulates the force applied to tissue from a surgical instrument. A generator provides electrical energy to the surgical instrument and an electrical signal representative of the generator load. The surgical instrument includes a handle that includes an actuating lever, and an end-effector located at the distal end of the handle. A force responsive element is operatively coupled to the actuating lever and the end-effector, wherein the force responsive element is adapted to alter a force on the end-effector in response to the electrical signal from the generator.

Description:
FIELD OF THE INVENTION 
     The present invention relates, in general, to ultrasonic surgical instruments and, more particularly, to active load feedback control of ultrasonic surgical clamping instruments. 
     BACKGROUND OF THE INVENTION 
     Ultrasonic instruments, including both hollow core and solid core instruments, are used for the safe and effective treatment of many medical conditions. Ultrasonic instruments, and particularly solid core ultrasonic instruments, are advantageous because they may be used to cut and/or coagulate organic tissue using energy in the form of mechanical vibrations transmitted to a surgical end-effector at ultrasonic frequencies. Ultrasonic vibrations, when transmitted to organic tissue at suitable energy levels and using a suitable end-effector, may be used to cut, dissect, or cauterize tissue. Ultrasonic instruments utilizing solid core technology are particularly advantageous because of the amount of ultrasonic energy that may be transmitted from the ultrasonic transducer through the waveguide to the surgical end-effector. Such instruments are particularly suited for use in minimally invasive procedures, such as endoscopic or laparoscopic procedures, wherein the end-effector is passed through a trocar to reach the surgical site. 
     Ultrasonic vibration is induced in the surgical end-effector by, for example, electrically exciting a transducer which may be constructed of one or more piezoelectric or magnetostrictive elements in the instrument handpiece. Vibrations generated by the transducer section are transmitted to the surgical end-effector via an ultrasonic waveguide extending from the transducer section to the surgical end-effector. 
     U.S. Pat. No. 5,322,055 describes an ultrasonic surgical apparatus that includes a surgical instrument having a transducer for converting an electrical signal into longitudinal vibratory motion. The longitudinal vibratory motion is transmitted to an ultrasonic blade that is connected to the handpiece. An accessory is releasably connected to the handpiece to enable clamping of tissue against the vibrating blade to afford improved coagulating and cutting of tissue. In U.S. Pat. No. 5,322,055 scissors-like grips actuate a pivoted clamp jaw along one side of the ultrasonically vibrating blade to compress and bias tissue against the blade in a direction which is substantially normal to the direction of longitudinal vibratory motion. U.S. Pat. No. 5,322,055 is hereby incorporated herein by reference. 
     Hemostatic devices have been described in various instruments for cutting, cauterization, coagulation or tissue welding. Most of the devices used are either monopolar or bipolar, for example, bipolar forceps, monopolar or bipolar scissors, and cutting and coagulating devices. See, for example, U.S. Pat. No. 5,707,369 that describes a temperature feedback system for closed loop control of the tissue temperature induced by the surgical instrument wherein a function of the temperature is used to determine when coagulation of tissue has occurred to a desired degree. 
     Although open loop electrosurgical and ultrasonic instruments have been used successfully to control bleeding during surgical procedures, when such instruments are used, the primary control is the experience of the surgeon who responds to what is observed to be happening to the tissue as it is treated with energy. Often, particularly for endoscopic procedures, surgeons cannot readily see what is happening to the tissue. Also, the change in tissue properties due to the energy may occur so quickly so as not to afford time for the surgeon to react soon enough to turn off the energy to the instrument. As a result, the tissue treatment may not be as precisely controlled as may be desirable. Some problems that may occur include tissue charring, sticking of the tissue to the electrodes of electrosurgical instruments, and over or under treatment of the tissue. 
     There is a continuing need to improve the control of energy delivery to tissue and/or to determine when tissue treatment has reached an optimal or desired level. The amount of ultrasonic energy coupled into tissue is a function of the force applied to the tissue by the ultrasonic end-effector. Prior instruments, such as those described in U.S. Pat. No. 5,947,984 hereby incorporated herein by reference, have limited the maximum amount of force that a surgeon could apply to tissue. However this is a single maximum set-point, and does not actively control the force applied to the tissue below the set limit. In particular there is a need to provide a device and method for active control of ultrasonic instruments that must perform both cutting and coagulating functions. 
     SUMMARY OF THE INVENTION 
     The present invention meets the needs described above by providing a system including a force feedback system for use in surgical procedures. The force feedback system is a closed loop arrangement that can modulate the force applied to tissue from a surgical instrument. A generator produces an electrical signal, which has a load parameter indicative of generator load. A load parameter may be, for example, current, voltage, impedance or temperature. A surgical instrument is electrically connected to the generator. The surgical instrument includes a handle that includes an actuating lever, and an end-effector located at the distal end of the handle. A force responsive element is operatively coupled to the actuating lever and the end-effector, wherein the force responsive element is adapted to alter a force on the end-effector in response to the electrical signal from the generator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to organization and methods of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a perspective view illustrating a surgical system including an actively controlled ultrasonic surgical shears according to the present invention, wherein the surgical shears are illustrated in combination with an ultrasonic transducer and a plan view of an ultrasonic signal generator; 
     FIG. 2 is an exploded perspective view of a first embodiment of a surgical instrument according to the present invention; 
     FIG. 3 is an exploded perspective view of a second embodiment of a surgical instrument according to the present invention; 
     FIG. 4 is a partial cutaway perspective view of the internal mechanism of the surgical instrument shown in FIG. 2; 
     FIG. 5 is a partial cutaway perspective view of the internal mechanism of the surgical instrument shown in FIG. 3; 
     FIG. 6 is a side view of the force mechanism of the surgical instrument shown in FIGS. 2 and 4; and 
     FIG. 7 is a side view of the force mechanism of the surgical instrument shown in FIGS.  3  and  5 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention relates, in general, to ultrasonic surgical clamping instruments and, more particularly, to active load feedback control of ultrasonic surgical clamping instruments. The present invention will be described in combination with ultrasonic instruments described herein such as, for example, an ultrasonic clamp coagulator instrument described in U.S. Pat. No. 5,947,984. Such description is exemplary only, and is not intended to limit the scope and applications of the invention. 
     FIG. 1 illustrates ultrasonic system  10  comprising an ultrasonic signal generator  15  with an ultrasonic surgical instrument  11 . Ultrasonic surgical instrument  11  includes a sandwich type ultrasonic transducer  82 , a hand piece housing  20 , and a clamp coagulator  120  in accordance with the present invention. Clamp coagulator  120  may be used for open or laparoscopic surgery. Clamp coagulator  120  includes instrument handle  14 , and elongated member  150  including ultrasonic end-effector  18 . End-effector  18  includes a clamp arm assembly  200  and a blade  81 . Ultrasonic transducer  82  includes a power supply cable  32 . Ultrasonic transducer  82 , which may also be referred to as a handpiece, comprises transduction elements (not shown), preferably piezeoceramic elements, for converting an electrical signal, for example, a 55,000 Hz sinusoidal waveform, into a mechanical longitudinal vibration. A suitable ultrasonic handpiece is available from Ethicon Endo-Surgery, Inc. as make ULTRACISION HARMONIC SCALPEL® and model HP051. 
     Power supply cable  32  transmits electrical energy from the ultrasonic signal generator  15  to ultrasonic transducer  82 . Ultrasonic transducer  82  converts electrical energy into ultrasonic energy in the form of mechanical motion. A suitable generator is available as model number GEN01, from Ethicon Endo-Surgery Inc., Cincinnati, Ohio. The ultrasonic energy is transmitted from ultrasonic transducer  82 , through the clamp coagulator  120 , to the end-effector  18 . 
     A surgical instrument such as, for example, clamp coagulator  120 , places a load on the output stage of generator  15 . A surgical instrument load is the load seen by the output stage of generator  15 , that is controlling and driving the surgical instrument. A portion of the surgical instrument load may include tissue load, as end-effector  18  is used to affect tissue. 
     Referring now to FIGS. 2, and  3 , clamp coagulator  120  is preferably attached to and removed from the ultrasonic transducer  82  as a unit. The proximal end of the clamp coagulator  120  preferably acoustically couples to ultrasonic transducer  82  as shown in FIG.  1 . It will be recognized that the clamp coagulator  120  may be coupled to the ultrasonic transducer  82  by any suitable means. 
     Referring to FIGS. 1 through 3, the elongated member  150  can be selectively rotated with respect to the instrument housing  130  as further described below. The instrument housing  130  (FIG. 1) includes a actuation trigger  24 , and a finger grip  22 , a left shroud  137  and a right shroud  138  (FIGS.  2  and  3 ). Elongated member  150  includes a support tube designated as outer sheath  28 , ultrasonic waveguide  30 , rotation knob  26 , actuating arm  34 , O-ring  38 , pin  27 , tubular collar  160 , and end-effector  18 . End-effector  18  includes ultrasonic blade  81  and clamp arm assembly  200 , which comprises clamp arm  57  and tissue pad  58 . Actuating arm  34  includes keyways  25 , openings  168 , pin-slot  31 , O-ring groove  29 , and lever-arms  61 . 
     The right shroud  138  is adapted to snap fit on the left shroud  137 . The right shroud  138  is preferably coupled to the left shroud  137  by a plurality of inwardly facing prongs  70  (not shown) formed on the right shroud  138 . The plurality of prongs  70  are arranged for engagement in corresponding holes or apertures  140 , which are formed in the left shroud  137 . When the left shroud  137  is attached to the right shroud  138 , a cavity is formed therebetween to accommodate various components, such as an active force mechanism as further described below. 
     Indexing mechanism  155  is disposed in the cavity of the instrument housing  130 . The indexing mechanism  155  is preferably coupled or attached on actuating arm  34  to translate movement of the actuation trigger  24  to linear motion of the actuating arm  34  to open and close the clamp arm assembly  200 . When the actuation trigger  24  is moved toward the finger grip  22 , the indexing mechanism  155  slides the actuating arm  34  rearwardly to pivot the clamp arm assembly  200  into a closed position. The movement of the actuation trigger  24  in the opposite direction slides the indexing mechanism  155  to displace the actuating arm  34  in the opposite direction, i.e., forwardly, and hence pivot the clamp arm assembly  200  into its open position. Actuation trigger  24  includes a thumb loop  142  with a first hole  124 . A yoke  180  includes a second hole  126 . A pivot pin  153  is disposed through first hole  124  and second hole  126  to allow pivoting. 
     The indexing mechanism  155  also provides a ratcheting mechanism to allow the elongated member  150  to rotate about its longitudinal axis relative to instrument housing  130 . The rotation of the elongated member  150  enables the clamp arm assembly  200  to be turned to a selected or desired angular position. The indexing mechanism  155  preferably includes a tubular collar  160  and yoke  180 . The tubular collar  160  of the indexing mechanism  155  is preferably snapped onto the proximal end of the actuating arm  34  and keyed into opposing openings  168 . The tubular collar  160  is preferably fabricated from polyetherimide. It is contemplated that the tubular collar  160  may be constructed from any suitable material. Tubular collar  160  may also be keyed to actuating arm  34  by keys  23  insertable into keyways  25 . 
     The tubular collar  160  preferably includes an enlarged section  162 , and a bore  166  extending therethrough. The enlarged section  162  preferably includes rings  42  formed around the periphery of the tubular collar  160  to form groove  43 . The groove  43  has a plurality of detents or teeth  44  (see FIGS. 4 and 5) for retaining the elongated member  150  in different rotational positions as the elongated member  150  is rotated about its longitudinal axis. Preferably, the groove  43  has twelve ratchet teeth to allow the elongated portion to be rotated in twelve equal angular increments of approximately 30 degrees. It is contemplated that the tubular collar  160  may have any number of teeth-like members. It will be recognized that the teeth-like members may be disposed on any suitable part of the tubular collar  160  without departing from the scope and spirit of the present invention. 
     Yoke  180  generally includes a holding or supporting member  182 . The supporting member  182  is preferably semi-circular and has a pair of opposing pawls  186  that extend inwardly to engage with the teeth  44  of the tubular collar  160 . It is contemplated that the pawls  186  may be disposed on any suitable part of the yoke  180  for engagement with the teeth  44  of the tubular collar  160 . It will also be recognized that the yoke  180  may have any number of ratchet arms. 
     The clamp arm assembly  200  is pivotally connected to the distal end of outer sheath  28 . Tissue pad  58 , preferably formed from Teflon or other suitable low-friction material, is mounted on the surface of the clamp arm for cooperation with the blade  81 , with pivotal movement of the clamp arm assembly  200  positioning the tissue pad  58  in substantially parallel relationship to, and in contact with, the blade  81 . By this construction, tissue to be clamped is grasped between the tissue pad  58  and the blade  81 . Tissue pad  58  is preferably provided with a sawtooth-like configuration to enhance the gripping of tissue in cooperation with the blade  81 . 
     Pivotal movement of the clamp arm assembly  200  with respect to the end-effector is effected by the provision of at least one, and preferably a pair of levers  193  of the clamp arm assembly  200  at the proximal end thereof. The levers  193  are positioned on respective opposite sides of the blade  81 , and are in operative engagement with lever arms  61  of the reciprocable actuating arm  34 . Reciprocal movement of the actuating arm  34 , relative to the outer tubular sheath  160  and the blade  81 , thereby affects pivotal movement of the clamp arm assembly  200  relative to the blade  81 . The levers  193  can be respectively positioned in a pair of openings defined by the lever arms  61 , or otherwise suitably mechanically coupled herewith, whereby reciprocal movement of the actuating member acts through the lever arms  61  and levers  193  to pivot the clamp arm. 
     Pawls  186  transfer opening force to actuating arm  34  through tubular collar  160 , resulting in the opening of clamp arm assembly  200 . The yoke  180  is preferably fabricated from polycarbonate. The yoke  180  may also be made from a variety of materials including other plastics, such as ABS, NYLON, or polyetherimide. It is contemplated that the yoke  180  may be constructed from any suitable material. 
     Yoke  180  also transfers a closing force to clamp arm assembly  200  as actuation trigger  24  is moved toward instrument housing  130 . Actuator travel stop  190  contacts actuation trigger  24  at the bottom of the stroke of actuation trigger  24 , stopping any further movement, or over-travel, of actuation trigger  24 . 
     To assemble the instrument  11  and accessory clamp coagulator  120 , the clamp coagulator  120  is screw-threaded onto the end of ultrasonic transducer  82 . In using the device it will be appreciated that the clamp can be used to coagulate and cut with ultrasonic energy applied, can be used to grasp tissue without application of ultrasonic energy, can be used to coagulate/cut with the clamp arm assembly  200  open and tissue unclamped, can be used to probe or manipulate tissue without application of ultrasonic energy, and can be used, with the clamp arm assembly  200  closed, for blunt dissection. The desired clamp arm assembly  200  rotational alignment is accomplished by use of rotation knob  26 , that can be rotated while holding the instrument housing  130  to thereby rotate the elongated member  150  relative to the instrument housing  130 . The detents provided by teeth  44  maintain this selected rotary alignment. The scissors-like grips are activated to close the clamp arm assembly  200  and ultrasonic power may be applied by activating a switch such as, for example, a foot switch. The longitudinal blade  81  vibration relative to the clamp arm assembly  200  couples to the tissue, causing coagulation, cutting or other desirable effects. Desirable tissue effects can be optimized by active pressure control as described below. 
     Active load control of clamp arm  57  against blade  81  is performed by a pressure control system  84  illustrated in FIGS. 2 through 7. A first embodiment of a pressure control system  84  is illustrated in FIGS. 2,  4 , and  6 . A second embodiment of a pressure control system  84  is illustrated in FIGS. 3,  5 , and  7 . Both embodiments are illustrated utilizing a pressure transducer  86  including a piston  87 , such as, for example, an electro-mechanical solenoid. It will be understood by those skilled in the art that any force or pressure transducer may be utilized with pressure control system  84 , such as, for example, servo-motors, hydraulics, pneumatics, and bi-metallics. 
     Referring to the first embodiment illustrated in FIGS. 2,  4  and  6 , pressure control system  84  includes pressure transducer  86 , wires  88 , connector  90 , spring  92 , spring cage  94 , yoke  180 , and actuating arm  34 . Pressure transducer  86  is electrically connected to ultrasonic signal generator  15  via wires  88 , through connector  90  and cable  32  (FIG.  1 ). Pressure transducer  86  changes in response to an electrical signal from ultrasonic signal generator  15 , altering the force or load exerted from actuating arm  34 , through pressure control system  84 , to end-effector  18 . 
     As illustrated in FIGS. 4 and 6, pressure transducer  86  actively alters spring  92  compression. Actuation trigger  24  delivers force through spring  92  to yoke  180 . As spring  92  is compressed, or released, the force delivered to end-effector  18  can be actively altered. Ultrasonic signal generator  15  may be programmable such that, for example, when an overload condition is detected by ultrasonic signal generator  15 , an electrical signal may be sent to pressure transducer  86  causing pressure transducer  86  to release compression of spring  92 , thereby mitigating the overload condition. 
     The load parameter for voltage in the ultrasonic signal generator  15  in, for example, the GEN01 generator disclosed previously, may be found on the generator PC board at location TP 6 . TP 6  is illustrated in Appendix B of the Generator PCB schematic, which may be found in the ULTRACISION HARMONIC SCALPEL service manual. The GEN01 generator attempts to maintain constant current to the transducer  82 . Therefore, voltage is adjusted as load varies, such that the voltage at TP6 is proportional to tissue load. Ultrasonic signal generator  15  may be programmed such that when TP6 reaches a set-point such as, for example, 200 Volts DC, the electrical signal is sent to pressure transducer  86  causing pressure transducer  86  to release compression of spring  92 . When compression of spring  92  is released, the force that is transferred through the yoke  180  to actuating arm  34  reduces the force of clamp arm assembly  200  against blade  81 . As may be understood by those skilled in the art, ultrasonic signal generator  15  may be programmed for other conditions such as, for example, a constant current load parameter, a constant voltage load parameter, an impedance parameter, an increased load after a set-point, a decreased load after a set-point, or a constantly decreasing load. Further, the temperature at the end effector is an indicator of load on the generator. A temperature feedback system, such as described in U.S. Provisional application Ser. No. 60/136,106, which is incorporated by reference herein, can be implemented to generate a electrical signal indicative of tissue load from generator  15  to pressure transducer  86 . 
     In the first embodiment of the present invention, the active load control of pressure control system  84  worked in conjunction with the ultrasonic system  10  operator through actuation trigger  24 . The operator can over-ride the active system by manually modulating the actuation trigger  24 . Referring now to FIGS. 3,  5  and  7 , a second embodiment of the present invention is illustrated wherein the operators&#39; use of actuation trigger  24  can be over-ridden by pressure control system  84 . 
     In the second embodiment, pressure transducer  86  delivers force directly to yoke  180 . Pressure transducer  86  is rigidly attached to left shroud  137 . Piston  87  is operatively connected to yoke  180 . Yoke  180  may be rigidly attached to actuation trigger  24  by gluing, ultrasonic welding or the like. Alternately, yoke  180  may be flexibly mounted to actuation trigger  24  through a spring, such as described in U.S. Pat. No. 5,947,984. As piston  87  of pressure transducer  86  is extended or retracted, the force felt by the operator is reduced or enhanced respectively. Ultrasonic signal generator  15  may be programmable such that, for example, when an overload condition is detected by ultrasonic signal generator  15 , an electrical signal may be sent to pressure transducer  86  causing piston  87  to retract, thereby decreasing the force of clamp arm assembly  200  against blade  81 . As may be understood by those skilled in the art, ultrasonic signal generator  15  may be programmed for other conditions such as, for example, an increasing clamp arm force, a decreased clamp arm force, maintaining constant clamp arm force, an increased clamp arm force after a predetermined time, a decreased load after a set-point, or a constantly decreasing load. 
     While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.