WO2010045158A2 - Tool for incising tissue - Google Patents

Abstract

A medical device for reducing the force necessary to penetrate tissue by reciprocating a cutting member in a direction that is parallel to the tissue and using a feedback system to indicate when different layers of tissue are being encountered. Although a variety of driving mechanisms can be used to generate the reciprocating motion, the preferred method is via the use of piezoelectric elements, such as flextensional transducers, amplified piezoelectric actuators, along with a bender bar, and voice coil motor motors. The feedback system utilizes any number of acoustic properties, such as controller impedance, phase lag, conductivity, or resistivity density variable. A vibrating reference member is passed through various tissues and the change in acoustic property is associated with the tissue. A look-up table can be developed that can be used by the feedback system to automatically alert the medical operator (e.g., visual, audible, tactile or display) that a different tissue is being encountered. A power shut-off can be provided as another alternative when a different tissue is encountered.

Description

TOOL FOR INCISING TISSUE

SPECIFICATION CROSS-REFERENCE TO RELATED APPLICATIONS

This PCT Application claims the benefit under 35 U.S. C. §119(e) of Provisional Application Serial No. 61/104,821 filed on October 13, 2008 entitled TOOL FOR INCISING TISSUE and whose entire disclosure is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. FIELD OF INVENTION

The present invention generally pertains to surgical instruments, and more specifically to high-speed electrically driven surgical blades. The invention is applicable to the cutting of skin and other tissues or materials found within the body.

2. DESCRIPTION OF RELATED ART

Cataract surgery is the most common surgical procedure in the United States today with close to 2 million procedures performed annually. Ocular keratomes are used to create self sealing incisions entering through the conjunctiva, scleara or cornea to form clear corneal incisions during cataract surgery. Self sealing incisions may also be referred to as self healing incisions as there is no need to cauterize tissue to prevent further tissue damage and prevent bleeding.

In general surgical applications, percutaneous access to tissues and vasculature as well as access through body-surface organ tissues like the conjunctiva and sclera is typically accomplished with non-vibrating cutting and shearing edges. Due in part to the variability of sharpness of conventional metal ophthalmic knife blades, the force required to create an incision into the eye tissue can cause significant tissue trauma, separating stromal layers and causing delamination of the Descemets membrane. As the surgeon applies force through the handle to a non-actuated blade, the point ruptures the surface membrane of the tissue and the edges cut and divide the tissue. Essentially, the blade is resisted by the force of the elastically deforming tissue. The blade is also resisted by the force required to divide the tissue at the cutting edges and the force created by the adhesive bonds between the blade and the tissue.

Several advances have been attempted to reduce the force necessary to penetrate a blade through tissue. Most of these, such as U.S. Patent No. 6,554,840 (Matsutani et al.) for example, simply reduce the cutting edge to blade thickness ratio to lower the penetration force. Others, such as U.S. Patent No. 6,547,802 (Nallakrishnan et al.) seek to improve incisions to the eye by maximizing the surface area of the cut with a blade having a wide surface area comprised of two cutting edges disposed at an angle greater than 90°. Meanwhile, U.S. Patent No. 6,056,764 (Smith) not only changes the blade tip angle, or angle between cutting edges on either side of a sharp tip, but also offers alternative blade materials such as diamond, sapphire, ruby, and cubic zirconia. Additionally, the 764 patent teaches the use of coatings over stainless steel blades to add strength to the blade. Other conventional attempts also disclose applying a surface treatment in the form of a hydrophobic/hydrophilic coating to the blade. However, while some reduction of force may be attained by the aforementioned disclosures, they are limited to only reducing the bulk surface friction between the instrument surface and the tissue surface being cut, and changing the surface area of the blade or changing the coefficient of friction between the surfaces.

One of the problems associated with surface treatment of surgical blades is that the blade sharpness is sacrificed for a lowering of mechanical friction. Also, an associated problem with changing the dimensions of the blade is faster dulling, further resulting in increased friction at the blade-tissue interface. These results only further promote cauterization and do not contribute to reducing the force necessary for penetration.

Another approach to cutting and penetrating through tissue is to sonically or ultrasonically vibrate the cutting edges of a surgical blade. Because piezoelectric ceramics deform when exposed to an electrical input, a phenomenon known as the converse piezoelectric effect, current technologies utilize stacks of piezoelectric material such as lead-zirconate-titanate (PZT) to produce the mechanical, ultrasonic motion. For example, U.S. Patent No. 4,587,958 (Noguchi) discloses an ultrasonic surgical device that focuses on the application of ultrasonic energy to shatter tissue. Unfortunately, it is apparent from the '958 disclosure that the express purpose of the ultrasonic vibrations applied upon the device is to "exhibit a satisfactory tissue shattering capacity". As a result, this type of tissue penetration does not minimize scarring but instead creates a blunt incision by shattering the tissue.

On the other hand, U.S. Patent No. 5,935,143 (Hood) attempts to minimize the "thermal footprint" of an ultrasonic blade. This is done by using a Langevin or dumbbell type transducer to produce axial motion of the cutting blade, thereby providing tactile feedback and enhanced ergonomics to the surgeon using the blade. The combination of ultrasonic vibration coupled with sinusoidal axial motion of the '143 blade perpendicular to the tissue surface plane also causes coagulation and cauterization of the tissue being incised and therefore does not increase the quality of the incision. While it has been shown in the art that ultrasonically vibrating a blade enhances its sharpness, U.S. Patent No. 5,324,299 (Davison, et al.) teaches that without proper configuration and design, an ultrasonic blade's "sharpness" is not enhanced when cutting through relatively loose and unsupported tissues. Therefore the '299 reference teaches ultrasonically driven scalpel blades having a hook tip design which focuses some of the vibration in a particular direction but does not actually increase the quality of the incision as it serves to enhance coagulation of the tissue being incised. Furthermore, a hooked tip prevents the blade from being optimally tuned for stab type incisions.

Unfortunately the focus of the improvements of vibrating blades found in the aforementioned prior-art disclosures were made with little regard to secondary issues related to incising tissue. For example, secondary issues such as those aspects of surgical procedure beyond simply incising the tissue include minimizing the pain experienced by patients during tissue penetration, minimizing scarring, and improving wound healing all of which are the result of having created a high quality incision at a reduced force necessary for cutting, incising, penetrating and the like.

Advancements in the surgical arts have been attempted to address these secondary issues. For instance, it has been shown that oscillating the blade of a surgical tool laterally or parallel to the tissue surface, rather than axially or perpendicular to its surface, may reduce pain during incising. As is disclosed in U.S. Patent No. 6,210,421 (Bocker, et al.), the lateral motion of the blade against the skin reduces the pressure waves that would otherwise be directed perpendicular to the skin in an axially driven blade, resulting in a smaller number of pain receptors being activated. The '421 patent however, is directed to a blood lancet which is not optimal for cutting tissue to a depth necessary as in ocular or minimally invasive surgery.

In an attempt to optimize tissue incising, U.S. Patent No. 6,254,622 (Hood) discloses an ultrasonically driven blade having an unsymmetrical cutting surface which causes an offset center of gravity that creates transverse movement of the blade, perpendicular to the longitudinal axis of the surgical device. The blade, having a low attack angle to form the asymmetric shape that gives the blade a sharp point, is able to then effectively cut both hydrogenous tissue and non hydrogenous tissue without requiring tension on the cutting medium. The transverse movement of the blade provides an efficient means of transferring the ultrasonic energy directly into the tissue and also moves the blood away from the cutting edge, allowing for a more efficient transfer of ultrasonic energy to the tissue. Unfortunately, the '622 patent relies on a driving frequency from 60,000 - 120,000 Hz_r a frequency range that is generally too high for preserving the soft tissue as it usually causes thermal damage.

In yet another attempt to transform the axial motion of a driving piezoelectric transducer into transverse motion of a surgical blade, U.S. Patent No. 6,585,745 (Cimino) discloses a split- electrode configuration to drive a bolt-type, or Langevin transducer. The patent discloses the use of lower frequencies such as 1OkHz in an axial or longitudinal direction causing a transverse motion of the blade perpendicular to the long axis of the device. While the 745 patent attempts to disclose that the device produces improved cutting, it is inherently flawed as it depends on the split-electrode configuration which is complex as compared to a single-phase pattern. Because the split-electrode configuration causes the piezoelectric transducers that drive the device to contract on one half and expand on the other, the device is vulnerable to induced stress and cracking, thereby reducing life and efficiency.

Lateral motion of the blade in a surgical tool has also been combined with longitudinal motion such as that which is described in U.S. Patent Publication No.2005/0234484 (Houser, et al.). While the '484 application discloses that longitudinal ultrasonic vibration of the blade generates motion and heat, thereby assisting in the coagulating of the tissue, the disclosure also recognizes that transverse ultrasonic vibration of the blade offers beneficial results. One such result is a total ultrasonic vibration having an amplitude that is larger and more uniform over a long distance of the blade as compared to surgical blades having only longitudinal vibrations. Yet, the invention relies solely on ultrasonic vibrations which inherently limits the invention to incising specific tissues only, and not the wide range of tissues that are encountered during a surgical procedure. A weakness of all blades which are solely ultrasonically driven is that they atomize the surrounding fluids. Because fluids are broken into small droplets when they encounter a solid mass vibrating at ultrasonic frequencies, the fluids becomes a mobile "mist" of sorts. As droplets, which have a size inversely proportional to the vibrating frequency, the fluid "mist" is similar to that of room humidifiers and also to the droplets created by industrial spray nozzles. One negative aspect of creating a mobile mist during a surgical procedure is that these particles may contain viral or bacterial agents. By ultrasonically vibrating the moisture surrounding unhealthy tissue as it is being incised, it is possible to unknowingly transport the bacterial or viral agent to healthy tissue. It therefore is an inherent weakness of ultrasonically driven surgical blades that they increase the chance of spreading disease or infection.

Therefore, a need exists for an improved surgical blade that is able to be vibrated sonically and ultrasonically, reduces the force required to penetrate tissue, and thereby reduces the amount of resulting tissue damage and scarring while also improving wound healing. All references cited herein are incorporated herein by reference in their entireties.

BRIEF SUMMARY OF THE INVENTION

Transducer technologies that rely on conventional, single or stacked piezoelectric ceramic assemblies for actuation are hindered by the maximum strain limit of the piezoelectric materials themselves. Because the maximum strain limit of conventional piezoelectric ceramics is about 0.1 % for polycrystalline piezoelectric materials such as ceramic lead zirconate titanate (PZT) and 0.5% for single crystal piezoelectric materials, it would require a large stack of cells to approach useful displacement or actuation of for example, a handheld device usable for processes such as cutting, slicing, penetrating, incising and the like. However, using a large stack of cells to actuate components of a handpiece would also require that the tool size to increase beyond usable biometric design for handheld instruments.

Flextensional transducer assembly designs have been developed which provide amplification in piezoelectric material stack strain displacement. The flextensional designs comprise a piezoelectric material transducer driving cell disposed within a frame or housing. The geometry of the frame or housing provides amplification of the transverse, axial, radial or longitudinal motions of the driver cell to obtain a larger displacement of the flextensional assembly in a particular direction. Essentially, the flextensional transducer assembly more efficiently converts strain in one direction into movement (or force) in a second direction. The present invention comprises a handheld device including a cutting, slicing, incising member which is actuated by a flextensional transducer assembly. For example, the flextensional transducer assembly may utilize amplified piezoelectric actuator (APA) transducer technology. The flextensional transducer assembly provides for improved amplification of displacement and improved performance which are above that of conventional handheld device. For example, the displacement may be improved by up to about 50-fold. Additionally, the flextensional transducer assembly enables handpiece configurations to have a more simplified design and a smaller format.

The present invention relates generally to a minimally invasive surgical blade for the cutting and incising of various materials and tissues within a body. Specifically, the present invention is a handpiece comprising a body, at least one piezoelectric transducer driver disposed within the body, a motion transfer adaptor, and a surgical blade for cutting, incising and penetrating.

In operation, at least one piezoelectric transducer disposed with a body of the handheld surgical tool oscillates sinusoidally in a frequency range of 10 - 5000 Hertz (Hz) and at an electric field in the range of about 300 - 500 V/mm. Specifically, the blade is driven sinusoidally at such a frequency and displacement so as to attain a peak velocity in the range of 0.9 - 2.5 m/s, more preferably in the range of 1.0 - 2.5 m/s and most preferably in the range of 1.5-2.0 m/s. The sinusoidal vibrations are transferred mechanically to the motion transfer adapter coupled at the proximal end to the piezoelectric transducer. The vibrations are further transferred mechanically to the surgical blade attached to a proximal end of the motion transfer adaptor. The surgical blade is configured in such a manner so as to oscillate in a direction that comprises an in-plane motion. In particular, the in plane motion comprises motion that is primarily in one plane. Most preferably, the surgical blade of the present invention is parallel to the surface of the tissue which is being incised, cut, penetrated or the like, by the blade. The in- plane motion is such a motion that is primarily perpendicular to the long axis of the device handle. In other words, the sinusoidal vibrations are an axial driving motion produced parallel to a hypothetical, centrally located axis which extends through a distal end and through a proximal end of a surgical tool's handle portion. The axial driving motion is transposed into lateral motion, perpendicular to the direction of the originating sinusoidal vibrations. It is an object of this invention to reduce tissue deformation. By way of example only, in ophthalmologic surgical procedures, a reduction in tissue deformation results in superior shaped flap peripheries and flap or stromal bed apposition. However, the advantages of using the present invention can be obtained in other surgical applications, such as, but not limited to, restorative or reconstructive microsurgery, cardiology or neurology, where reciprocally-driven cutting edges may be used to precisely pierce or incise tissues.

In yet another embodiment, the piezoelectric transducer is an APA transducer similar to, but not limited to that which is described in U.S. Patent No. 6,465,936 (Knowles) which is incorporated by reference herein.

In one embodiment, the piezoelectric transducer is a standard bimorph actuator or a variable thickness bimorph similar to but not limited to, those configurations which are described by Cappalleri, D. et al in "Design of a PZT Bimorph Actuator Using a Metamodel- Based Approach", Transactions of the ASME, Vol. 124 June 2002 and those described in U.S. Patent No. 6,665,917 (Knowles) both of which are hereby incorporated by reference.

Electrical signal control of the present invention is facilitated by an electrically coupled feedback system which provides the capability of high cut rate actuation, control over cut width, and low traction force for these procedures. Additional feedback may include means for identifying type of material being penetrated at the blade cutting edge such as one which measures electromechanical impedance at the blade tip or edge for example. Such a system could be that which is disclosed in U.S. Provisional Patent Application No. 61/037,700 filed on March 18, 2008 and entitled "Minimally Invasive Surgical Tool" and U.S. Application Serial No. 12/559,383 filed on September 14, 2009 entitled "Medical Tool for Reduced Penetration Force with Feedback Means" both of which are incorporated by reference herein in their entirety and both of which are owned by the same Assignee, namely, Piezo Resonance Innovations, Inc., as the present application.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein:

FIG. 1 is a graph illustrating the reduction of force response; FIG. 2 is a perspective view of a first embodiment of the handheld surgical device; FIG.3A is a cross sectional view of the piezoelectric bender type actuator shown in Fig. 2;

FIG. 3B is a perspective view of the piezoelectric bender type actuator shown in Fig. 3A;

FIG.3C is a general illustration showing the relative orientation of the bender of Fig.2; FIG.3D a general illustration showing a first orientation of the bender of Fig. 2 relative to a central axis of the device;

FIG. 3E a general illustration showing a second orientation of the bender of Fig. 2 relative to a central axis of the device;

FIG. 3F is a cross sectional view of one embodiment of the piezoelectric bender type actuator shown in Fig. 2 showing the polarization of the piezoelectric plates; FIG.4A is a perspective view of a second embodiment of the handheld surgical device;

FIG.4B is a perspective view of an alternative configuration of the second embodiment of the handheld surgical device;

FIG. 4C is a cross-sectional view of the amplified piezoelectric actuator used in the second embodiment of the handheld surgical device; FIG. 5 A is a perspective view of a third embodiment of the handheld surgical device;

FIG. 5B is similar to the device in Fig. 5A but springs are included to provide bias or dampening to the arcuate motion of the motion transfer device;

FIG. 6A is a perspective view of a fourth embodiment of the handheld surgical device;

FIG. 6B is a cross sectional view of the electromagnetic motor used in the fourth embodiment of the handheld surgical device of FIG.6A;

FIG. 7 is a flow diagram of how the feedback subsystem of the present invention operates;

FIG. 7 A is a graph of test data (e.g., device impedance data) of the vibrating reference member versus the material being tested; and

FIG. 8 is an exemplary schematic of a feedback subsystem for use in the various embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiments of the present invention are illustrated in FIGS.1 through 8 with the numerals referring to like and corresponding parts.

The effectiveness of the invention as described, for example, in the aforementioned preferred embodiments, relies on the reduction of force principle in order to optimize incising, cutting, or penetrating through tissue or materials found within the body. Essentially, when tissue is incised, cut, penetrated or separated by the high speed operation of the surgical blade of the present invention, the tissue is held in place purely by its own inertia. In other words, a reduction of force effect is observed when a knife blade, for example a slit knife blade, is vibrated with an in-plane motion during the incision process and enough mechanical energy is present to break adhesive bonds between tissue and blade. The threshold limits of energy can be reached in the sonic or ultrasonic frequency ranges if the necessary amount of blade displacement is present.

To exploit the reduction of force effect, the surgical blade of the present invention is designed such that the blade attains a short travel distance or displacement, and vibrates sinusoidally with a high cutting frequency. Utilizing the various device configurations as described in the aforementioned embodiments, it has been determined that the sinusoidal motion of the blade must include at least a peak velocity in the range of 0.9 - 2.5 m/s, more preferably between 1.0 - 2.25 m/s and most preferably at a velocity of 1.5 - 2.0 m/s. For example, Fig. 1 shows a graphical representation of the resisting force versus depth of a surgical blade penetrating into material. In Fig. 1, the curve labeled A represents data for a blade in an "off or non vibrating condition and the curve labeled B represents data for a surgical tool having a blade that is vibrated at 450Hz and at a displacement of 500μm. As is apparent from Fig. 1, curve A shows that without being vibrated, the force necessary to penetrate into a material is much higher than that for a blade being vibrated, such as that represented by curve B.

In a first embodiment of the present invention as shown in Fig. 2, a bender actuated surgical tool 100 comprises a body 110, and a bimorph piezoelectric transducer 111 disposed within body 110. The bimorph piezoelectric transducer 111 comprises at least one piezoelectric plate 112, but preferably comprises more than one of piezoelectric plates 112 attached longitudinally upon at least one side of a bender support bar 113. The bender support bar 113 comprises a proximal end 117 and a distal end 118, with a bender motion constraint 114 at the proximal end 117. The bender motion constraint 114 attaches bender support bar 113 to support surface 116 of the body 110. In one embodiment, the bender motion constraint 114 of the present embodiment comprises at least one thru-hole 115 (see Fig. 3B) and a bolt 115' passing at least partly through the bender support bar 113 and into an attachment slot (not shown) formed on support surface 116. The attachment slot may be for example a threaded hole or the like. The bender actuated surgical tool 100 further comprises a blade 119 having a collar 120. The blade collar 120 is directly and mechanically attached to the bender distal end 118 of bender support bar at collar attachment node 121. Blade 119 may preferably comprise first cutting edge 122, second cutting edge 123, blade tip 124, first blade ear 125 and second blade ear 126. Collar attachment node 121 may comprise a threaded slot, compression slot, 1/4"- cam lock slot, or the like. The bender actuated surgical tool 100 of the present invention also comprises a hypothetical long axis BA which is oriented centrally to run through a proximal end 134 and a distal end 135 of body 110, further passing through the centers of each of body 110, bimorph piezoelectric transducer 111, and blade 119. Blade tip 124 is located externally to body 110.

Now, with respect to Fig.3A, a cross section of the bimorph piezoelectric transducer 111 of the bender actuated surgical tool 100 of Fig. 2 is described. Preferably, the bimorph piezoelectric transducer 111 comprises at least one layer of a plurality of piezoelectric plate 112 formed side by side, each plate being formed longitudinally on, against, and in direct physical and electrical contact to a first side surface 113' of bender support bar 113, thereby forming first piezoplate stack 127. The bimorph piezoelectric transducer 111 may also comprise a second piezoplate stack 128 configured in a similar fashion as the first piezoplate stack 127 except each of piezoelectric plate 112 being formed on, against and in direct physical and electrical contact to a second side surface 113" formed opposite to the first side surface 113' of bender support bar 113.

With respect to Fig. 3B, a perspective view of an embodiment of the bimorph piezoelectric transducer 111 with the blade 119 of the bender actuated surgical tool 100 of Fig.2 is described. At least one, but preferably two or more of thru-hole 115 are located at bender proximal end 117 of bender support bar 113. A plurality of piezoelectric plates 112 formed side by side, each plate being formed longitudinally on, against and in direct physical and electrical contact to a first side surface (equivalent to 113' as shown in Fig. 3A) of bender support bar 113, thereby forming first piezoplate stack 127. Again, the bimorph piezoelectric transducer 111 may also comprise a second piezoplate stack 128 configured in a similar fashion as the first piezoplate stack 127 except each of piezoelectric plate 112 being formed on, against and in direct physical and electrical contact to a second side surface (equivalent to 113" as shown in Fig. 3A) formed opposite to the first side surface 113' of bender support bar 113. During manufacture, a predetermined dipole, or pole direction is applied to the piezoelectric plates 112. In operation, electrically activating the piezoelectric plates 112 will cause them to either expand or contract, depending on whether the pole direction and electric field are applied in the same direction or opposite. It is an especially important aspect of the current invention that the piezoelectric plates 112 are stacked relative to one another, and attached to bender support bar 113 such that when an electric field is applied across each of the plates, a resulting net-expansion or net-contraction of the piezoelectric stack causes a net bending of the bender bar 113.

For example, as shown in Fig.3C, bender bar 113 maintains a configuration which runs parallel to hypothetical long axis BA. However, upon exposing a stack of piezoelectric plates (not shown) to an electric field, the stack experiences either a net compression or net expansion which then translates to a displacement of at least a portion of bender bar 113 relative to BA as shown in Fig. 3D. In fact, rather than just a single stack on only one side of bender bar being exposed to an electric field and experiencing a resulting compression or expansion, a stack on each of opposite sides of bender bar 113 can be exposed to appropriate electric fields so as to cause one of the stacks to expand and the other to contract. This configuration could provide for an even higher displacement. Conversely, as shown in Fig. 3E, the stacks can be exposed to an electric field opposite in direction to the one applied in Fig.3D to cause the stacks to cause the bender bar 113 displace in an opposite direction. To impart a vibration so as to reduce the penetration force of the example device of Fig. 2, the displacements shown in Figs. 3D -3E would be alternated at an appropriate frequency.

It will be apparent to one of ordinary skill in the art that for Figs.3C-3E there are several ways in which the piezoelectric plates and their corresponding electrodes (not shown) may be configured with respect to their dipole directions relative to the poled directions of other piezoelectric plates in the stack to impart an optimal displacement force on the bender bar in the present embodiment. Furthermore, one having ordinary knowledge of unimorph, bimorph and multimorph technologies will recognize that several configurations may be implemented that can take advantage of an applied electric field so that the stacks optimally translate a constriction or an expansion into an alternating displacement of the bender bar to which they are attached.

One such configuration, as shown in Fig. 3F for which the relative pole directions of the piezoelectric plates are indicated with arrows, is presented with respect to the bender of Fig.3B.

In this embodiment, first and second stacks 127 and 128 comprise a plurality of alternately poled plates separated by electrodes. A common electrode may separate consecutively placed, alternately poled plates. Now, describing the components of the stacks longitudinally from a proximal to a distal portion of bar 113, second piezoplate stack 128 comprises a ground electrode 137 formed in electrical contact to a distally placed first poled plate 112+. Next, is second poled plate 112- having a pole direction opposite to that of 112+ with positive electrode 136 formed between 112+ and 112-. Another of first poled plate 112+ is now formed with another ground electrode 137 formed between 112- and this poled plate 112+. This configuration, of alternating first and second poled plates having common electrodes of alternating positive or negative electrical contact is repeated as necessary. Additionally, a similar configuration may be disposed along an opposite side of bar 113 forming first piezoplate stack 127. It is important to note that the bender support bar 113 is electrically insulated from the piezoplates and the electrodes . One method to achieve electrical insulation of the bender bar from the stacks is by coating each of stacks 127 and 128 with an insulating material, coating bender support bar 113 with an insulating coating, or both. Alternatively, bender support bar 113 may itself be of an insulating material such as plastic.

While Fig.3F has been described with reference to a single layer of piezoelectric plates to form stacks 127 and 128, it is hereby noted that several layers of piezoelectric plates may be formed one over the other in such a manner so long as that individual electrical activation of each of the individual plates is still maintained. Alternatively, several plates may be replaced with a single larger plate, but will require a higher induced electric field in order to operate.

Returning again to Fig. 2, but noting that the descriptions of Figs. 3A-3F as disclosed above are equally transferable to the bimorph 111, in operation an electric field is induced across at least one of piezoelectric plates 112 of either first piezoplate stack 127 or second piezoplate stack 128, or both by application of a voltage across the electrical contacts (not shown). As described previously with respect to Figs.3C-3E, as a result of an applied alternating electrical signal, such as an AC signal, the result is an alternating electric field across the piezoelectric plates. In effect, bender support bar 113 then experiences a constricting force at its first side surface and a tensional force on its second side surface as translated by the constriction and expansion of the piezoelectric plates forming first piezoplate stack 127 and second piezoplate stack 128, respectively, during one cycle of the applied voltage. During the opposite phase of the applied AC signal, bender support bar 113 then experiences a tensional force at its first side surface and a compressive force on its second side surface as a result of expansion and compression of the first piezoplate stack 127 and second piezoplate stack 128, respectively, during the opposite cycle of the applied current. The voltages across positive and negative electrodes are alternated at an appropriate frequency so as to induce the condition necessary to reduce the penetration force as described above for Fig. 1.

While the actuator of the bender actuated surgical tool has been described mainly with emphasis to a bimorph type actuator, a unimorph type actuator may easily replace the bimorph piezoelectric transducer 111. Li essence, when the bimorph piezoelectric transducer 111 comprises at least one layer of at least one of piezoelectric plate 112 formed side by side, each plate of a first layer being formed longitudinally against and in direct physical contact to only a first side surface 113' of bender support bar 113 so as to form first piezoplate stack 127, and for example, second piezoplate stack 128 is not formed, the piezoelectric transducer is a unimorph piezoelectric transducer. Furthermore, a unimorph or a bimorph may be of variable thickness in that they may comprise a plurality of stacked layers, each additional layer being shorter in length than the previously stacked layer, typically by at least the length of one piezoelectric plate 112.

In an additional embodiment of the present invention, an Amplified Piezoelectric Actuator (APA) transducer driven surgical tool 400 is shown in Fig.4 A. The APA transducer driven surgical tool 400 comprises a body 410, an APA transducer 411, a motion transfer member 417 attached to the APA transducer, a body opening 418', a blade 419 and a blade neck 420 attached to the motion transfer member. As shown in Fig.4A, the APA transducer 411 is a flextensional transducer assembly including piezoelectric cells 412 housed within a flexible frame 413. The cells 412 may include a spacing member 416 separating at least two stacks of piezoelectric material. Regardless of frame dimensions, at rest, the piezoelectric cells are held in a compressed state by the sidewalls of frame 413. Any expansion or contraction of the cells is translated to the sidewalls of the frame 413. The frame 413 typically includes either an elbow at the intersection of walls with corrugated pattern along the top and bottom walls, 414 and 415 respectively, of the assembly frame.

In operation, the piezoelectric cells 412 expand during the positive cycle of an AC voltage, which causes top wall 414 and bottom wall 415 of the frame 413 to approach one another. Conversely, cells 412 moves constrict during the negative AC cycle, resulting in an outward displacement of the top 414 and bottom 415 walls of the frame 413. However, in the present embodiment, bottom wall 415 is fixedly attached to body 410 so that any movement in the cell will result in only a relative motion of top wall 414 with respect to the body 410 and bottom wall 415. Furthermore, a first end portion of motion transfer member 417 is coupled to the top wall 414, and coupled to the blade neck 420 at an opposite end portion. Additionally, blade neck 420 and motion transfer member 417 are slidably disposed within opening 418' of the body 410. Thereby, in operation, an applied electrical signal such as an AC electrical signal causes an expansion or contraction of piezoelectric cell 412 depending on the direction of the electric field across the cells. As the sidewalls of the frame are pushed against by the piezoelectric cells during their expansion, or alternatively, as the sidewalls and frame relax to keep the piezoelectric cells under compression as the piezoelectric cells constrict, a resulting movement of top wall 414 relative to bottom wall 415 results. As top wall 414 moves reciprocally, the reciprocating motion is translated to transfer member 417 as it is attached to frame 413 at top wall 414, and further translated to a reciprocating motion of blade neck 420 and blade 419 which are attached to motion transfer member 417. In an alternative embodiment of APA transducer driven surgical tool 400, as shown in

Fig. 4B, first end portion of motion transfer member 417 extends beyond the APA transducer 411 and instead is coupled to a pivot member 421. Pivot member 421 may be a hinge or a flexible material which is fixed to body 410 at a pivot attaching member 422 and is able to move relative the body at an opposite end, for example the end attached to motion transfer member 417. The opposite end of motion transfer member 417, located a first length 423 from pivot member 421 is still similarly attached to neck 420 as described above for Fig. 4A, however a middle portion located a second length 424 from pivot member 421 is attached to top wall 414 of frame 413 of APA transducer 411. Similarly to APA transducer 411 as described in Fig.4A, bottom wall 415 is fixed to body 410. In operation, an applied electrical signal such as an AC electrical signal causes an expansion or contraction of piezoelectric cell 412 depending on the direction of the electric field across the cells. As the sidewalls of the frame are pushed against by the piezoelectric cells during their expansion, or alternatively, as the sidewalls and frame relax to keep the piezoelectric cells under compression as the piezoelectric cells constrict, a resulting movement of top wall 414 relative to bottom wall 415 results. As top wall 414 moves reciprocally, the reciprocating motion is translated to transfer member 417 as it is attached to frame 413 at top wall 414 in a motion constrained by pivot 421, the motion being further translated to a reciprocating motion of blade neck 420 and blade 419 which are attached to motion transfer member 417.

Two examples of applicable APA transducers available in the prior art are the non- hinged type, and the grooved or hinged type. Details of the mechanics, operation and design of an example hinged or grooved APA transducer are described in U.S. Patent No. U.S.6,465,936, which is hereby incorporated by reference in its entirety. An example of a non-hinged APA transducer is the Cedrat APA50XS, sold by Cedrat Technologies, and described in the Cedrat Piezo Products Catalogue "Piezo Actuators & Electronics" (Copyright ©Cedrat Technologies June 2005) also hereby incorporated by reference.

In the present invention, the APA transducer may include a particular symmetry or asymmetry which determines the response of frame 413 to piezoelectric cells 412. For example, as shown in Fig.4C, top wall 414 and bottom wall 415 of frame 413 are formed such that they are parallel to one another and their lengths are equivalent. Typically, the APA transducer frame is symmetric with opposing walls being of equivalent length; with first frame length 413a equal to second frame length 413b and third frame length 413d equal to fourth frame length 413e. In the present invention, there is a need to provide alternate modes of displacement which can be attained by an alternative design of the APA transducer 411. Li the alternative design of APA transducer 411, an asymmetry in the width of frame 413 adds a significant angular component to the direction of motion of the top wall 414 relative to bottom wall 415 when cells 412 constrict or expand upon proper electrical activation, rather than only a vertical component such as that in the conventional APA design of the prior art disclosed above. In this alternative design of APA transducer 411, first frame length 413a remains equal to second frame length 413b, but the length of third frame length 413d is greater than fourth frame length 413e. Li fact, an alternative design of APA transducer 411 includes frame 413 having an asymmetric shape, with the ratio of third frame length 413d to fourth frame length 413e being in the range of greater than 1 : 1 up to and including 3:1, wherein the lengths of each of cells 412 on either side of spacing member 416 remain equal. So long as the ratio of third frame length 413d to fourth frame length 413e is greater than 1 : 1 and lengths of each of cells 412 remain equal, spacer 416 need not be perfectly aligned and centered relative to top wall 414 and bottom wall 415.

While the embodiments disclosed above in reference to Figs.4A - 4B relied on an APA transducer, other components may replace the transducer to cause motion to the blade. For example, in Fig. 5A an electric motor driven surgical tool 500, a portion of an electric motor 511, for example an AC or a DC motor, is fixed to body 410. A motor shaft 513 protruding from and controlled by the electric motor 511 is able to rotate in one direction or another, or alternates between two rotation directions, and translates this motion to a rotating cam 514 to which motor shaft 513 is attached. A cam is a projecting part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path. The rotating cam 514 can be an eccentric disc or other shape that produces a smooth reciprocating (back and forth) motion in a separate arm which is a lever making contact with the cam, for example motion transfer member 417 physically contacts cam 514 a second length 424 from a pivot member 421. In other words, the cam is a device that translates the circular motion provided by the electric motor 511 to motor shaft 513 into a reciprocating motion of motion transfer member 417 about a moving portion of pivot member 421. It is noted that the automotive industry often relies on the basic principles of cams such as that disclosed in U.S. Patent No. 4,662,323 (Moriya) while similar principles for use of cams have been introduced in devices, such as that disclosed in U.S. Patent No. 6,402,701 (Kaplan et al.), both of which are hereby incorporated by reference. The reciprocating motion translated to member 417 allows a blade 419 to reciprocate as blade neck 420 is slidably disposed to travel in a back-and-forth motion with motion transfer member 417 within opening 418'. The embodiment shown in Fig. 5B is similar to the device shown in Fig. 5A but further includes springs 501 to provide bias or dampening to the arcuate motion of the motion transfer member 417.

Alternatively, another motor type can be used to cause reciprocating motion of the blade as a substitute for the APA transducer disclosed with respect to Fig. 6A. For example, in Fig. 6A, an electromagnetic motor driven surgical tool 600 uses an electromagnetic motor, for example voice coil motor 611, to reciprocate a blade attached to an arm. In this case, a driving member 613 being the electromagnetically actuated portion of the voice coil motor is attached to an adaptor 617 portion of a motion transfer member 617 located a second length 424 from a pivot member 421. As the voice coil motor 611 reciprocates driving member 613 linearly, this motion is translated to a reciprocating motion of motion transfer member 617 about pivot member 421. As a result, blade 419 is similarly reciprocated as it is attached to neck 420 which of course is attached to member 617 as described previously and is slidably disposed relative to opening 418'.

As shown in more detail in Fig. 6B, the voice coil motor 611 comprises a conducting coil 612 wound on the exterior diameter of a coil support tube 614, a magnetic member (621 and/or 622), dampers 624, and end caps 616. The magnetic member of voice coil motor 611 comprises a first magnetic driving member 621, second driving magnetic member 622 and pole pieces 618, 619, and 620. The first magnetic driving member 621 may be a single annular permanent magnet or a plurality of annular permanent magnets being positioned side by side and having a common pole direction and attached to a driving member 613. Additionally, second magnetic driving member 622 may also be a single permanent magnet or a plurality of permanent magnets being positioned side by side and having a common pole direction, preferably opposite in direction as that of 621. For example, first magnetic driving member 621 is positioned such that each of its magnets' north poles face toward the driver upper portion 615 while second magnetic driving member 622 is configured such that each of its magnets' south poles face toward the driver lower portion 615'. First magnetic driving member 621 is separated from second magnetic driving member 622 by second pole piece 619. First pole piece 618 is fixed on a distal end of first magnetic driving member 621, opposite pole piece 619 with first magnetic driving member 621 being disposed between 618 and 619, while pole piece 620 is fixed on a proximal end of second magnetic driving member 622, opposite pole piece 619 with second magnetic driving member 622 being disposed between 619 and 620. Pole pieces 618, 619 and 620 are typically a ferro-magnetic and are preferably stainless steel. In one embodiment, with respect to voice coil motor 611, the south poles of first magnetic driving member 621 and second magnetic driving member 622 are fixedly secured to the opposing faces of pole piece 619 in order to provide a zone of maximum magnetic flux density which extends radially outwardly from the central portion of pole piece 619 similar to the configuration disclosed in U.S. Patent No. 4,363,980 (Petersen) which is hereby incorporated by reference.

From the above description, it may be appreciated that the present invention provides significant benefits over conventional surgical tools. The configuration of the actuating means described above such as embodiments comprising a bender transducer actuator such as a unimorph, bimorph, or multiniorph, an APA transducer actuator, an electric motor such as a DC motor or AC motor, or an electromagnetic motor such as a voice-coil motor each accommodate the use of actuating members in a surgical instrument by enabling the displacement of the cutting member or blade to such velocities that cause a reduction of force needed for cutting, incising, or penetrating of tissue during surgical procedures. As mentioned previously, electrical signal control facilitated by an electrically coupled feedback system provide the capability of high cut rate actuation, control over cut width, and low traction force for these procedures. As discussed above, the configuration of the various embodiments of the present invention accommodates the use of piezoelectric actuating members (or voice coil actuating members) in a medical instrument by enabling the transverse displacement of the blade 119/419 to such frequencies that cause a reduction of force needed for penetrating through tissue during various surgical procedures. Electrical signal control facilitated by an electrically coupled feedback system may also provide the capability of high oscillation rate actuation, control over penetration depth, electrical cut off (faster response than human) and low traction force for these procedures.

In particular, FIG.7 provides a general method of implementing the feedback subsystem of the present invention. Using a predetermined association of electromechanical properties regarding various tissues (e.g., fat, muscle, cartilage, bone, etc.), as described with regard to FIG.7A below, the feedback subsystem includes a sensor for detecting system/device changes as the cutting member 119/419 cuts through tissue and wherein the sensor generates a signal characteristic of the electromechanical property being monitored. The sensor (e.g., impedance analyzer, such as the Hewlett Packard, HP 4192A) feeds this signal to a microcontroller that references a look-up table to determine the material that the blade 119/419 is currently cutting. The microcontroller can drive a display or other indicators or alerts for informing the operator of the present invention 100 just what the cutting member 119/419 is currently cutting. One alternative is for the microcontroller to de-energize the device 100, if necessary. FIG. 7A shows data which demonstrates an exemplary methodology for determining characteristic electromechanical properties (e.g., system/device impedance, system/device phase lag, system/device conductivity, density variability, etc.) to be used for generating a "look-up" table or other association of tissue with the changing electromechanical property as part of the feedback subsystem. By way of example only, a 1.5 inch long, hollow, 3 faceted, Trocar needle (vibrating reference member) is mounted on a bolted Langevin transducer. The resonance frequency of the system in air is -47 kHz. The tip is inserted 5mm into different test media with a variety of densities. FIG. 7 A is a plot of the amplitude of the impedance (by way of example only) curve as a function of frequency. The peak is the anti-resonant frequency. The dip downward to the left is the resonant frequency. The upper curve is the needle/transducer assembly in air. The lower curves show a reduction in amplitude, and slight shift in anti- resonant frequency, as the needle is inserted into media of increasing stiffness (e.g., sponge, dense foam, apple, potato). The lowest curve shows the result when the needle was inserted ~ 1 inch into the potato. These shifts in amplitude and frequency (and other potential measurements such as phase lag, resistance, and density) provide various electromechanical (EM) properties that can be used for distinguishing between different tissues, and also the depth of insertion.

FIG.8 provides an exemplary block diagram of a feedback subsystem 700 for use in the present invention. The microncontroller 702 may comprise a look-up table in an internal memory generated in accordance with that described with regard to FIG. 7A. Depending on which EM property is being monitored (e.g., device impedance, device conductivity, device phase lag, density variability, etc.) a corresponding sensor feeds back the corresponding EM property signal to the microcontroller 702 which uses the process of FIG.7 to drive indicators or the display to alert the device operator as to the tissue that the cutting member 119/419 is currently cutting. The microcontroller 702 also controls the device energization via drive electronics 704. It should be noted that the present invention 100 may be powered from an external AC power source or batteries. In either case, power to the invention 100 can be immediately controller or even interrupted when particular tissue penetration is detected.

It is within the broadest scope of the present invention to encompass a variety of feedback configurations, including solid state switching and/or digital controls. Additionally, the present invention comprises sensors for providing feedback, either visually, audibly, or by tactile response, using a variety of detection mechanisms (such as, but not limited to, electrical, magnetic, pressure, capacitive, inductive, etc. means) to indicate successful penetration of various tissues, or of voids within the body so that the clinician is aware of the tissue being cut. Additionally, the feedback control of the electronics enables the device 100 to be vibrated in such a way that the force is also reduced as blade cutting edges 122/123 are retracted from the living being. Even pressure transducers can be coupled at the blade 119/419 or neck 420 or even to the bender motion constraint 114 where blade pressure against the tissue being cut can is transferred from the blade edges 122/123 through the blade body and/or bender body for EM property detection.

As mentioned previously, see also U.S. Provisional Patent Application No. 61/037,700 filed on March 18, 2008 and entitled "Minimally Invasive Surgical Tool" and U.S. Application Serial No. 12/559,383 filed on September 14, 2009 entitled "Medical Tool for Reduced Penetration Force with Feedback Means" both of which are incorporated by reference herein in their entirety and both of which are owned by the same Assignee, namely, Piezo Resonance

Innovations, Inc., as the present application.

Now that exemplary embodiments of the present invention have been shown and described in detail, various modifications and improvements thereon will become readily apparent to those skilled in the art. While the foregoing embodiments may have dealt with the incision of an eyeball as an exemplary biological tissue, the present invention can undoubtedly ensure similar effects with other tissues commonly incised during surgery. For example, as mentioned previously, there are multiplicities of other applications like restorative or reconstructive microsurgery, cardiology or neurology, to name a few, where embodiments disclosed herein comprising reciprocally driven cutting edges may be used to precisely pierce or incise tissues other than that forming an eyeball. Furthermore, while the previous embodiments have relied heavily on examples in which the surgical blades are vibrated sinusoidally in a direction parallel to the surface of the tissue or material being incised, cut, divided or penetrated by the blade, they are not limited to such locomotion in such a relative direction. For example, the motion of the blades of the previously described embodiments may actually be sinusoidal and in a direction that is perpendicular to the surface of the tissue or material being incised, cut, divided or penetrated by the blade. Accordingly, the spirit and scope of the present invention is to be construed broadly and limited only by the appended claims, and not by the foregoing specification.

REFERENCE LABELS

A Static blade force curve

APA Amplified Piezoelectric Actuator B Vibrating blade force curve

BA Hypothetical Bender long axis N North S South

100 Bender actuated surgical tool 110 Body

111 Bimorph piezoelectric transducer

112 Piezoelectric plate 112+ First poled plate 112- Second poled plate 113 Bender support bar 113' First side surface 113" second side surface

114 Bender motion constraint

115 Bolt through hole 115' Bolt

116 Support Surface

117 Bender proximal end

118 Bender distal end

119 Blade 120 Blade collar

121 Collar Attachment node

122 First cutting edge

123 Second cutting edge

124 Blade tip 125 First blade ear

126 Second blade ear

127 First piezoplate stack

128 Second piezoplate stack 134 Body proximal end 135 Body distal end

136 Positive Electrode

137 Ground Electrode

400 APA transducer driven surgical tool 410 Body 411 APA transducer

412 Piezoelectric cell

413 Frame 413a First frame length 413b Second frame length 413c Third frame length 413d Fourth frame length 414 Top Wall

415 Bottom wall

416 Spacing member

417 Motion transfer member 418' Body Opening 419 Blade

420 Blade Neck

421 Pivot Member

422 Pivot Attaching Member

423 First Length 424 Second Length

500 Electric Motor driven surgical tool

501 Spring

511 Electric Motor 513 Motor Shaft 514 Rotating Cam

600 Electromagnetic Motor driven surgical tool

611 Voice-coil Motor

612 Conducting coil

613 Driving member 614 Coil support tube

615 Driver upper portion 615' Driver lower portion 616 End caps

617 Motion Transfer Member 617' Adaptor

618 First pole piece 619 Second pole piece

620 Third pole piece

621 First magnetic driving member

622 Second magnetic driving member 624 Dampers 700 Feedback subsystem

702 Microcontroller 704 Drive electronics

While the invention has been described in detail and with reference to specific examples thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

Claims

WHAT IS CLAIMED IS:

1. An apparatus for automatically controlling the incision of tissue based on the tissue being encountered during incision, said apparatus comprising: a cutting member which is reciprocated in a direction transverse to a longitudinal axis of said apparatus for reducing the force needed to cut the tissue by said cutting member; an actuator coupled to said cutting member for converting electrical energy into said transverse motion of said cutting blade; and a feedback subsystem that detects any change of electromechanical properties related to the operation of the cutting member for indicating to an apparatus operator that a different type of tissue has been contacted by said cutting member.

2. The apparatus of Claim lwherein said feedback system comprises: a sensor for detecting a change in said electromechanical property and outputting a signal characteristic of said change in said electromechanical property; a microcontroller coupled to said sensor for receiving and processing said signal, said microprocessor having access to a correlation between changes in said electromechanical property and various tissues; and an indicator, driven by said microcontroller, for alerting an operator of a change in tissue that said cutting member is currently cutting.

3. The apparatus of Claim 2 wherein said indicator comprises a display that informs the operator of an identity of said tissue being currently encountered by said cutting member. 4. The apparatus of Claim 2 wherein said microcontroller controls the energization provided to said apparatus.

5. The apparatus of Claim 4 wherein said feedback system automatically de-energizes said cutting member when a different type of tissue is encountered.

6. The apparatus of Claim 3 wherein said electromechanical property is apparatus impedance.

7. The apparatus of Claim 3 wherein said electromechanical property is phase lag experienced by said apparatus.

5 8. The apparatus of Claim 3 wherein said clectrorntdumical property is conductivity of said apparatus.

9. The apparatus of Claim 2 wherein said actuator composes a piezoelectric actuator interfaced with a bender bar which is coupled to said cutting member, said piezoelectric actuator vibrating at a frequency to produce a sinusoidal displacement of said blade. 0 10. The apparatus of Claim 2 wherein said piezoelectric actuator comprises a unimorph configuration.

11. The apparatus of Claim 2 wherein said piezoelectric actuator comprises a bimorph configuration.

12. The apparatus of Claim 2 wherein said piezoelectric actuator comprises a5 multimorph configuration.

13. The apparatus of Claim 2 wherein said piezoelectric actuator comprises an amplified piezoelectric actuator (APA).

14. The apparatus of Claim 2 wherein said piezoelectric actuator comprises a voice coil motor. 0 IS. The apparatus of Claim 13 wherein said amplified piezoelectric actuator is coupled to a motion transfer member that converts APA movement into transverse blade movement

16. The apparatus of Claim 15 wherein said motion transfer member is an elongated element and wherein said APA is coupled to said motion transfer member at a point between S endpoints of said morion transfer member.

17. A method for automatically controlling the incision of tissue based on the tissue being encountered during the incision, said method comprising: establishing characteristic electromechanical propeity changes of a vibrating reference member that passes through various tissues that correlates0 said changes with particular tissues; reciprocating a cutting member of a device in a direction that is parallel to the tissue being cut for reducing the force needed to cut the tissue by said cutting member; detecting a change in said characteristic electromechanical property; 5 comparing said detected change against said correlation; and indicating to an operator of said cutting member the type of tissue that is being currently being encountered based on said change in said characteristic electromechanical property. IS. The method of Claim 17 wherein said step of indicating to an operator comprising displaying or informing the operator of an identity of the tissue being currently encountered by said cutting member.

19. The method of Claim 17 wbeiein said step of indicating comprises de-energizing said cutting member. 20. The method of Claim 17 wherein said step of establishing characteristic electromechanical property comprises coupling said vibrating reference member to an apparatus having apparatus impedance, said apparatus having characteristic impedances corresponding to every change in vibration of said vibrating reference member as it passes through various tissues, said characteristic impedances being associated with a corresponding tissue.

21. The method of Claim 17 wherein said electromechanical property is phase lag experienced by said device.

22. The method of Claim 17 wherein said electromechanical property is conductivity of said device. 23. The method of Claim 17 wherein said electromechanical property is density variability.

24. The method of Claim 17 wherein said cutting member is vibrated using a piezoelectric member and at a peak velocity in the range of 0.9 -2.S m/s.

25. The method of Claim 24 wherein said piezoelectric member is energized with an AC signal at an electric field of between 300-500 V/mm and at a frequency of 450 Hz.

26. The method of Claim 25 wherein said piezoelectric member is vibrated at a frequency to produce sinusoidal displacement of the cutting member in the range of 25O-500μm.