Abstract:
The present invention is an ultrasonic surgical instrument having an altered cross sectional area and/or stiffness of ½ wave segments of a waveguide and/or end effector. The waveguide is coupled to an ultrasonic transducer. The ½ wave segments of the waveguide or end effector comprise a number of geometries and function to extend or decrease the length of a waveguide and/or end effector without adding or removing ½ wave segments. The present invention is intended to function with conventional ultrasonic transducers at conventional frequencies.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application claims the priority benefit of U.S. provisional patent application, serial No. 60/413,120, filed on Sep. 24, 2002, the contents of which are incorporated by reference in their entirety herein. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to an ultrasonic surgical instrument for cutting, coagulating, grasping and blunt-dissecting tissue, and particularly relates to an ultrasonic surgical instrument having longer working lengths. The present invention is, in one embodiment, specifically adapted for endoscopic surgery, although it has other surgical applications as well.  
         BACKGROUND OF THE INVENTION  
         [0003]    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.  
           [0004]    [0004]FIG. 1 illustrates an exemplary ultrasonic system  10  comprising an ultrasonic signal generator  15  with ultrasonic transducer  82 , hand piece housing  20 , and clamp coagulator  120  in accordance with the present invention. Clamp coagulator  120  may be used for open or laparoscopic surgery. The ultrasonic transducer  82 , which is known as a “Langevin stack”, generally includes a transduction portion  90 , a first resonator or end-bell  92 , and a second resonator or fore-bell  94 , and ancillary components. The ultrasonic transducer  82  is preferably an integral number of one-half system wavelengths (nλ/2) in length as will be described in more detail later. An acoustic assembly  80  includes the ultrasonic transducer  82 , mount  36 , velocity transformer  64  and surface  95 .  
           [0005]    The distal end of end-bell  92  is connected to the proximal end of transduction portion  90 , and the proximal end of fore-bell  94  is connected to the distal end of transduction portion  90 . Fore-bell  94  and end-bell  92  have a length determined by a number of variables, including the thickness of the transduction portion  90 , the density and modulus of elasticity of the material used to manufacture end-bell  92  and fore-bell  94 , and the resonant frequency of the ultrasonic transducer  82 . The fore-bell  94  may be tapered inwardly from its proximal end to its distal end to amplify the ultrasonic vibration amplitude as velocity transformer  64 , or alternately may have no amplification.  
           [0006]    The piezoelectric elements  100  may be fabricated from any suitable material, such as, for example, lead zirconate-titanate, lead meta-niobate, lead titanate, or other piezoelectric crystal material. Each of the positive electrodes  96 , negative electrodes  98 , and piezoelectric elements  100  has a bore extending through the center. The positive and negative electrodes  96  and  98  are electrically coupled to wires  102  and  104 , respectively. Wires  102  and  104  are encased within cable  25  and electrically connectable to ultrasonic signal generator  15  of ultrasonic system  10 .  
           [0007]    Wires  102  and  104  transmit the electrical signal from the ultrasonic signal generator  15  to positive electrodes  96  and negative electrodes  98 . The piezoelectric elements  100  are energized by an electrical signal supplied from the ultrasonic signal generator  15  in response to a foot switch  118  to produce an acoustic standing wave in the acoustic assembly  80 . The electrical signal causes disturbances in the piezoelectric elements  100  in the form of repeated small displacements resulting in large compression forces within the material. The repeated small displacements cause the piezoelectric elements  100  to expand and contract in a continuous manner along the axis of the voltage gradient, producing longitudinal waves of ultrasonic energy.  
           [0008]    An ultrasonic transmission  80  is generally defined as a waveguide  179 , an end effector  88  and an ultrasonic transducer  82 . Further, the ultrasonic waveguide  179  and end effector  88  are, in combination, referred to as a “blade”. Ultrasonic transducer  82  converts the electrical signal from ultrasonic signal generator  15  into mechanical energy that results in primarily longitudinal vibratory motion of the ultrasonic transducer  82 , waveguide  179  and end-effector  88  at ultrasonic frequencies. Ultrasonic end effector  88  and ultrasonic transmission waveguide  179  are illustrated as a single unit construction from a material suitable for transmission of ultrasonic energy such as, for example, Ti6Al4V (an alloy of titanium including aluminum and vanadium), aluminum, stainless steel, or other known materials. Alternately, end effector  88  may be separable (and of differing composition) from waveguide  179 , and coupled by, for example, a stud, welding, gluing, or other known methods.  
           [0009]    When the acoustic assembly  80  is energized, a vibratory motion standing wave is generated through the acoustic assembly  80 . The amplitude of the vibratory motion at any point along the acoustic assembly  80  depends on the location along the acoustic assembly  80  at which the vibratory motion is measured. A minimum or zero crossing in the vibratory motion standing wave is generally referred to as a node (i.e., where motion is usually minimal), and an absolute value maximum or peak in the standing wave is generally referred to as an anti-node. The distance between an anti-node and its nearest node is one-quarter wavelength (λ/4).  
           [0010]    In order for the acoustic assembly  80  to deliver energy to end-effector  180 , all components of acoustic assembly  80  must be acoustically coupled to the ultrasonically active portions of clamp coagulator  120 . The distal end of the ultrasonic transducer  82  may be acoustically coupled at surface  95  to the proximal end of an ultrasonic waveguide  179  by a threaded connection such as stud  50 .  
           [0011]    The components of the acoustic assembly  80  are preferably acoustically tuned such that the length of any assembly is an integral number of one-half wavelengths (nλ/2), where the wavelength λ is the wavelength of a pre-selected or operating longitudinal vibration drive frequency f d  of the acoustic assembly  80 , and where n is any positive integer. It is also contemplated that the acoustic assembly  80  may incorporate any suitable arrangement of acoustic elements.  
           [0012]    The clamp coagulator  120  may include an instrument housing  130 , and an elongated member  150 . The elongated member  150  can be selectively rotated with respect to the instrument housing  130 . Located at the distal end of the outer tube  160  is an clamp element  180 , which comprises the end effector  88  and clamp arm  300  for performing various tasks, such as, for example, grasping tissue, cutting tissue and the like.  
           [0013]    The ultrasonic waveguide  179  of the elongated member  150  extends through an aperture of an inner tube. The ultrasonic waveguide  179  is preferably substantially semi-flexible. It will be recognized that the ultrasonic waveguide  179  may be substantially rigid or may be a flexible wire. Ultrasonic vibrations are transmitted along the ultrasonic waveguide  179  in a longitudinal direction to vibrate the ultrasonic end effector  88 .  
           [0014]    The ultrasonic waveguide  179  may, for example, have a length substantially equal to an integral number of one-half system wavelengths (nλ/2). The ultrasonic waveguide  179  may be preferably fabricated from a solid core shaft constructed out of material that propagates ultrasonic energy efficiently, such as titanium alloy (i.e., Ti-6Al-4V) or an aluminum alloy. The ultrasonic waveguide  179  may also amplify the mechanical vibrations transmitted to the ultrasonic end effector  88  as is well known in the art.  
           [0015]    The ultrasonic end effector  88  may have a length substantially equal to an integral multiple of one-half system wavelengths (nλ/2). The distal end of ultrasonic end effector  88  may be disposed near an antinode in order to provide the maximum longitudinal excursion of the distal end. When the transducer assembly is energized, the distal end of the ultrasonic end effector  88  is configured to move in the range of, for example, approximately 10 to 500 microns peak-to-peak, and preferably in the range of about 30 to 150 microns at a predetermined vibrational frequency.  
           [0016]    Ultrasonic generators, such as the model number GEN01, from Ethicon Endo-Surgery, Inc., Cincinnati, Ohio, can lock onto any longitudinal frequency between 51 and 57.5 kHz. Ultrasonic end effectors are designed to have only one resonance in this range. Presently, ultrasonic blades are limited to a working length of about 36 cm, though a need has arisen for end effectors having a working length of 40-45 cm in order to perform applications requiring additional length. The addition of ½ waves in an ultrasonic transmission assembly incurs the penalty of having mode shape frequencies closer together. At some point, the mode shape frequencies are so close together that two or more will be within the lock range of a generator/transducer. Each half wave of Ti6A4V is currently limited to about 1.7 inches long unless the cross section is modified. Presently, the ultrasonic generators in use are not compatible with end effectors having more than 9 (½ wave) sections, thereby limiting the working length of a titanium end effector to 15.4 inches or 39 cm.  
           [0017]    The present invention addresses the deficiencies of the prior art.  
         BRIEF SUMMARY OF THE INVENTION  
         [0018]    The present invention provides the operator with an ultrasonic device having a long working length for use in applications where this feature is desired, such as in the field of bariatrics, without adding ½ wave segments and yet providing the generator the same effective modes to lock onto. The present invention also provides for a reduction in the overall length of an ultrasonic waveguide, which may be beneficial for applications where a shorter waveguide is desirable. The present invention provides for a blade having altered cross sectional areas and/or stiffness of ½ wave segments of the waveguide and/or end effector.  
           [0019]    The ½ wave segments of the waveguide or end effector comprise a number of geometries and function to extend or decrease the length of a waveguide and/or end effector without adding or removing ½ wave segments. The present invention is intended to function with conventional ultrasonic transducers at conventional frequencies.  
           [0020]    It would be advantageous to provide an ultrasonic surgical instrument with a longer working length that does not require the addition of ½ wave segments. It would be further advantageous to provide an end effector with a longer working length that is simple to manufacture, thereby reducing both production and patient costs. It would also be advantageous to provide an ultrasonic instrument with an extended work length that is compatible with generators presently available. It would be even further advantageous to provide a means of reducing the overall length of a waveguide without having to remove ½ wave segments, for applications where a shorter wavelength is desirable.  
           [0021]    A further advantage of the present invention is that it provides serial amplification/deamplification. If a series of extended ½ waves are joined, and the nodes at resonance are biased to one side, each ½ wave will act as an amplifier or deamplifier. As a portion of a end effector warms up, frequency and node bias will change. This changes the serial amplification/deamplification, whereby functioning to decrease net amplification and net heat and creating a feedback loop. The feedback loop functions to maintain end effector temperature below a designated point intrinsic in the design of the end effector.  
           [0022]    A still further advantage of the present invention comprises multi-mode resonance. Serial expanded ½ waves will maintain the same longitudinal frequency N, but N−1 and N+1 will decrease. This is of no concern in regards to N−1 , but N+1 will converge on N, thereby initiating a multi-mode resonance. However, most of the nodes for N and N+1 are close to each other. The one exception is where N&#39;s node is N+1&#39;s anti-node surrounded by 2 nodes. Furthermore, the expanded ½ waves up to that point act as deamplifiers and afterwards as amplifiers. Therefore, the 90 degree out of phase anti-node tends to have low amplitude, resulting in a end effector (or waveguide) that can run at two frequencies with low impedence and low heat generation at the same time. It is also possible to create a device with the two mode shapes running at the same frequency.  
           [0023]    The restriction is that the two mode shapes will be in phase at one end, and 180degrees out of phase at the other end. If the two modes are at the same frequency, in phase at one end, out of phase and with equal amplitude at the other end, the canceled end can be extended by adding uniform diameter rods, maintaining both modes out of phase, superimposed. As many ½ waves can be added as desired.  
           [0024]    Finally, if an equivalent system is joined to the one described above, it will reconvert the canceling waves into reinforcing waves. The result is a very long, thin, ultrasonic waveguide with zero motion over the bulk of the length. It may be possible to use a thin, flexible wire over this null zone to effectively guide ultrasonic energy from outside the body, through an uninsulated flexible catheter to a working end effector.  
           [0025]    The present invention is useful in for endoscopic and open surgical applications. It is also useful for robotic-assisted surgery applications.  
         BRIEF DESCRIPTION OF THE FIGURES  
         [0026]    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:  
           [0027]    [0027]FIG. 1 is a partial cut-away elevation view of a representative ultrasonic surgical instrument of the prior art;  
           [0028]    [0028]FIG. 2 is a partial elevation view of a waveguide having two different cross-sectional areas;  
           [0029]    [0029]FIG. 2 a  is a partial elevation view of an alternate embodiment of a waveguide in FIG. 2 having at least two different cross-sectional areas;  
           [0030]    [0030]FIG. 3 is a partial elevation view of an alternate embodiment of a waveguide having two different cross-sectional areas; and  
           [0031]    [0031]FIG. 3 a  is a partial elevation view of an alternate embodiment of a waveguide in FIG. 3 having at least two different cross-sectional areas. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0032]    Before explaining the present invention in detail, it should be noted that the invention is not limited in its application or use to the details of construction and arrangement of parts illustrated in the accompanying drawings and description. The illustrative embodiments of the invention may be implemented or incorporated in other embodiments, variations and modifications, and may be practiced or carried out in various ways. Furthermore, unless otherwise indicated, the terms and expressions employed herein have been chosen for the purpose of describing the illustrative embodiments of the present invention for the convenience of the reader and are not for the purpose of limiting the invention.  
         [0033]    It is also understood that any one or more of the following-described embodiments, expressions of embodiments, examples, methods, etc. can be combined with any one or more of the other following-described embodiments, expressions of embodiments, examples, methods, etc.  
         [0034]    The present invention is useful in combination with an end effector only, an end effector and a clamp, a shear configuration, or numerous other end-effectors.  
         [0035]    Examples of ultrasonic surgical instruments are disclosed in U.S. Pat. Nos. 5,322,055 and 5,954,736 and in combination with ultrasonic end effectors and surgical instruments as, for example, disclosed in U.S. Pat. Nos. 6,309,400 B2, 6,283,981 B1, and 6,325,811 B1 all of which are incorporated in their entirety by reference herein.  
         [0036]    [0036]FIG. 2 of the present invention illustrates a ½ wave segment  20  having a proximal reduced cross section segment  21 , a central segment  22 , and a distal reduced cross section segment  23 . ½ wave segment  20  is part of an ultrasonic transmission assembly comprising a waveguide, an end effector, and an ultrasonic transducer as previously described. FIG. 2 further illustrates a first anti-node  24 , a node  25 , and a second anti-node  26 , wherein at a standard frequency, the proximal most portion of proximal reduced cross section segment  21  is substantially aligned with first anti-node  24 , the central symmetry line of central segment  22  is substantially aligned with node  25 , and the distal most portion of distal segment  23  is substantially aligned with second anti-node  26 . The segment distal to antinode  24  may have the same or different cross section than segment  21 . Additionally, the segment proximal to antinode  26  may have the same or different cross section than segment  23 .  
         [0037]    Such cross section reductions may be applied on the distal portion of the ½ wave  20  or the proximal portion of the ½ wave  20  only, but the effect of lengthening ½ wave  20  will be reduced by a corresponding amount. A cross section increase of substantially short length in segment  21  or  23  will reduce the effect of lengthening the ½ wave  20 , but can still be incorporated without eliminating the effect.  
         [0038]    One representative embodiment of the present invention excited at a conventional frequency of 55 kHz comprises an overall ½ wave segment  20  length of 2.417″, a central segment  22  diameter of 0.140″, a proximal and distal segment  21  and  23  having a length of 0.585″, and a proximal and distal segment  21  and  23  having a diameter of 0.070″. This design of ½ wave segment  20  extends the length of the ½ wave segment  20  to 2.417″, as opposed to a ½ wave having no cross sectional or stiffness variation, which is limited to about 1.7″ at that frequency when composed of the same material. The present invention contemplates combining ½ wave segment  20  with other ½ wave segments that are substantially the same as ½ wave segment  20 , although other ½ wave segments may proximally begin at an anti-node and end distally at a node. Further, the present invention contemplates the use of a number of variations in cross sectional dimension that may be used to extend the length of ½ wave segment  20 .  
         [0039]    Stiffness and density may be used in place of cross-sectional variation to achieve a similar lengthening effect as above, wherein stiffness is increased in the range of central segment  22 , and/or density is decreased in the range of proximal and distal tapered segments  21  and  23 . This could be accomplished through various means including, but not limited to, increasing stiffness by local heat treatment, adding high modulus ceramic particles such as boron carbide, or using another alloy such as an iron or cobalt based alloy and decreasing density by using another alloy such as aluminum or adding ceramic particles such as boron carbide.  
         [0040]    The combination of ½ wave segment  20  with other ½ wave segments having substantially the same features of ½ wave segment  20  functions to extend the length of the waveguide and/or end effector resulting in greater overall working length than that achieved by instruments having ½ wave segments with no cross-sectional area variation or stiffness variation.  
         [0041]    Referring to FIG. 2 a , a plurality of such cross section reductions may be used, with smaller cross sections preferentially from node  25   a  towards antinodes  26   a  and  24   a . In the extreme, this leads to a tapered shape from node  25   a  to nodes  26   a  and  24   a . One representative embodiment of the present invention excited at a conventional frequency of 55 kHz comprises an overall ½ wave segment  20   a length of 2.214″, having a diameter of 0.140″ at node  25   a  and a diameter of 0.070″ at antinodes  24   a  and  26   a . This design of ½ wave segment  20   a  extends the length of the ½ wave segment  20  to 2.214″, as opposed to a ½ wave having no cross sectional or stiffness variation, which is limited to about 1.7″ at that frequency when composed of the same material. The present invention contemplates combining ½ wave segment  20   a  with other ½ wave segments that are substantially the same as ½ wave segment  20   a  or  20 , although other ½ wave segments may proximally begin at an anti-node and end distally at a node. Further, the present invention contemplates the use of a number of variations in cross sectional dimension that may be used to extend the length of ½ wave segment  20   a.    
         [0042]    [0042]FIG. 3 illustrates an alternate embodiment of the present invention comprising a ½ wave segment  30 , wherein ½ wave segment  30  further comprises a first segment  31 , a central segment  32 , and a second segment  33 , wherein first segment  31  is, at a normal operating frequency (55.5 kHz), substantially aligned with first anti-node  35 , central segment  32  is substantially aligned with node  36 , and second segment  33  is substantially aligned with second anti-node  37 . First segment  31  and second segment  33  comprise a larger cross sectional area than central segment  32 . The measurements of first segment  31 , central segment  32 , and second segment  33 , comprise a number of variations in order to facilitate a reduction in the overall length of ½ wave segment  30 .  
         [0043]    In one embodiment of the present invention, the measurement parameters of ½ wave segment  30  are designed in such a way as to function with a conventional ultrasonic transducer at a conventional frequency (55.5 kHz). Overall length of of ½ wave segment  30  is 0.993″, a central segment  32  diameter of 0.070″ and length 0.495″, proximal and distal segments  31  and  33  having a length of 0.249″ and a diameter of 0.140 ″. ½ wave segment  30  may be attached to a number of other ½ wave segments having similar measurements substantially similar to ½ wave segment  30 . The change in cross sectional area of ½ wave segment  30  functions to reduce the overall length of ½ wave segment  30 , thereby reducing the overall length of the waveguide. The shortened waveguide is useful for procedures in which a shorter waveguide is beneficial. The segment distal to antinode  35  may have the same or different cross section than segment  31 .  
         [0044]    Additionally, the segment proximal to antinode  37  may have the same or different cross section than segment  33 .  
         [0045]    Such larger cross sections may be applied on the distal portion ½ wave  30  or the proximal portion of the ½ wave  30  only, but the effect of shortening ½ wave  30  will be reduced by a corresponding amount. A cross section decrease of substantially short length in segment  31  or  33  will reduce the effect of lengthening the ½ wave  30 , but can still be incorporated without eliminating the effect.  
         [0046]    Referring to FIG. 3 a , a plurality of such cross section reductions may be used, with smaller cross sections preferentially from antinodes  35   a  and  37   a  towards node  36   a . In the extreme, this leads to a tapered shape. One representative embodiment of the present invention excited at a conventional frequency of 55 kHz comprises an overall ½ wave segment  30   a  length of 1.273″, having a diameter of 0.070″ at node  36   a  and a diameter of 0.140″at antinodes  35   a  and  37   a.    
         [0047]    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. In addition, it should be understood that every structure described above has a function and such structure can be referred to as a means for performing that function. 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.