US20140100567A1 - Surgical cutting instrument with electromechanical cutting - Google Patents

Abstract

A mechanical cutting device that makes use of mechanical (rotary) motion and suction to engage tissue also applies a cutting energy sufficient to vaporize the tissue. The rotation and suction are used to engage the tissue (sucking tissue into cutting windows when the cutting windows of inner and outer blades are aligned), and then the cutting member(s) function as an electrode(s) by having an electrical cutting signal applied thereto so that the cutting member(s) electrically cut the tissue as the cutting members relatively rotate. The electrical cutting signal is only applied as the windows become aligned up until the cutting of the tissue is completed. The cutting signal preferably is stopped after the cutting windows become misaligned. While the cutting windows are misaligned, a coagulation signal can be supplied to the cutting member so that the device functions as an electrocautery device.

Description

BACKGROUND
• This disclosure relates to surgical instruments, and in particular to surgical cutting instruments having mechanical cutting blades and one or more electrodes for providing surgical energy to the treatment area (e.g., for coagulation, vaporization of tissue, and/or other treatment effects).
• Surgical apparatus used to shave, cut, resect, abrade and/or remove tissue, bone and/or other bodily materials are known. Such surgical apparatus can include a cutting surface, such as a rotating blade disposed on an elongated inner tube that is rotated within an elongated outer tube having a cutting window. The inner and outer tubes together form a surgical cutting instrument or unit. In general, the elongated outer tube includes a distal end defining an opening or cutting window disposed at a side of the distal end of the outer tube. The cutting window of the outer tube exposes the cutting surface of the inner tube (typically located at a side of the distal end of the inner tube) to tissue, bone and/or any other bodily materials to be removed. A powered handpiece is used to rotate the inner tube with respect to the outer tube while an outer tube hub (connected to the proximal end of the outer tube) is fixed to the handpiece and an inner tube hub (connected to the proximal end of the inner tube) is loosely held by the powered handpiece and is rotated by a motor of the handpiece.
• In some instruments, the inner tube is hollow and has a cutting window on a side surface near its distal end such that tissue, bone, etc., will be cut or shaved as the cutting window of the inner tube aligns with and then becomes misaligned with the cutting window of the outer tube as the inner tube is rotated within the outer tube. In this regard, it can be said that the cutting device nibbles or takes away small pieces of the bone, tissue, etc., as the inner tube is rotated within the outer tube.
• In some instruments, a vacuum is applied through the inner tube such that the bodily material that is to be cut, shaved, etc., is drawn into the windows of the inner and outer tubes when those windows become aligned, thereby facilitating the cutting, shaving, etc., of the tissue, which then travels through the inner tube due to the suction. It also is common to supply an irrigation fluid, which can include a liquid, to the surgical site via a passage provided between the inner and outer tubes.
• Microdebrider shaver blades are common instruments used in endoscopic surgery. The shaver blade delivers high speed mechanical cutting of tissue at a specified area of anatomy that the surgeon can reach through a minimally invasive incision or natural orifice. One challenge during procedures using such instruments can be the slowing down or stopping of bleeding (hemostasis) during the procedure. One solution for maintaining proper hemostasis during a procedure is to utilize an electrocautery instrument that can be used inside the same minimally invasive surgical corridor. In a minimally invasive procedure, every time the surgeon exchanges the cutting instrument for the electrocautery instrument there is a corresponding increase in the time required to perform the procedure and there is a risk of traumatizing the anatomy due to the exchange of the instruments. Thus, it is convenient to combine the mechanical cutting and electrocautery instruments to form one instrument performing both functions. By providing a microdebrider shaver blade that also can perform electrocautery, the need to perform tool exchanges at the surgical site is reduced and can even be eliminated.
• There are two standard types of electrocautery: bipolar and monopolar. Monopolar cautery uses one electrode at the surgical site and then relies on a neutral electrode placed somewhere else on the patient (typically on the skin of the patient) to help disburse the energy enough to pass the energy safely through the patient. Bipolar cautery does not use a separate neutral electrode. Instead, bipolar cautery delivers the energy and returns the energy through the device using two electrodes at the surgical site. That is, a bipolar device will provide two electrodes at the surgical site, one active electrode and one return electrode.
• It is known to provide microdebrider shaver blades with bipolar energy electrodes to perform the electrocautery. As is known, cutting or shaving takes place by rotating (or oscillating with some devices) the inner cutting blade while suction is applied through the device. An electrical signal appropriate for achieving electrocautery is applied to the active electrode so that tissue is cauterized to achieve hemostasis during use of the device.
• It also is known to perform surgical cutting using only electrical energy. For example, a cutting device such as an electrical scalpel can be used to completely remove the surgical area. Such devices are used, for example, to perform tonsillectomies. These electro-surgical devices generally have no moving parts to engage the tissue. Thus, these procedures in which electrical energy is used to remove tissue are often performed “open” and make use of manual grasping instruments to bring the tissue into contact with the cutting electrode.
SUMMARY
• In accordance with some aspects of the invention, a mechanical cutting device which makes use of mechanical motion and suction to engage tissue also applies a cutting energy sufficient to vaporize the tissue. When the device uses a rotary motion (for example, the device includes a rotating inner blade having a sideward-facing cutting window that rotates within an outer cutting blade having a sideward-facing cutting window) the rotary motion (of the inner blade) can be much slower than typical microdebrider speeds (in one illustrative example, speeds as low as about 60 rpm or less). The rotation and suction are used to engage the tissue (sucking tissue into the cutting windows when the cutting windows of the inner and outer blades are aligned), and then the cutting member (or members) function as an electrode and have an electrical cutting signal applied thereto so that the cutting member (or members) electrically cut the tissue as one of the cutting members (i.e., the inner cutting blade) rotates. The electromechanical action may provide a cleaner, more precise cut of larger “bites” of tissue compared with mechanical cutting. Purely mechanical cutting at higher speeds often chews (multiple rotations required to take a large “bite”) tissue, and may be limited to smaller “bites” of tissue due to the relatively small time frame in which the cutting window is open.
• Preferably, the electrical cutting signal is only applied as the windows become aligned and then become misaligned by rotation (or other oscillating motion) of the inner cutting blade until the cutting of the tissue is completed. The cutting signal preferably is then stopped after the cutting windows become misaligned so that undesired tissue vaporization does not occur. While the cutting windows are misaligned, a coagulation signal nonetheless can be supplied to the cutting member so that the device functions as an electrocautery device thereby minimizing or eliminating bleeding.
• The electrocautery-inducing signal preferably is applied during only part of the rotation of the inner cutting blade. Preferably, the electrocautery-inducing signal is applied only when the cutting windows are misaligned (that is, the electrocautery-inducing signal is not applied when tissue can be sucked into the aligned windows). Applying the electrocautery-inducing signal at all times can increase the temperature of the tip of the instrument, causing eschar buildup (burned tissue/blood buildup) and potentially galling the mechanical bearing surfaces of the cutting instrument. Intermittently applying the electrocautery-inducing signal reduces the amount of energy delivered to the tissue, reducing heat buildup of the instrument, thereby minimizing or eliminating eschar buildup. This aspect of the invention is applicable to mechanical cutting microdebriders with or without the electro-cutting (tissue vaporization) capability.
• In accordance with some aspects of the invention, a surgical cutting instrument includes a first cutting blade, a second cutting blade, at least one first electrode and control circuitry. The first cutting blade has a tubular body with a distal end and a proximal end, and includes a cutting window that is sideward-facing disposed at the distal end of the first cutting blade. The cutting window includes a cutting edge. The second cutting blade is movably disposed inside the first cutting blade and has a distal cutting portion that, together with the cutting edge of the cutting window, cuts tissue by moving within the first cutting blade. The at least one first electrode is located adjacent to at least the cutting edge at the distal end of the first cutting blade. The control circuitry is configured to control an electrical power signal supplied to the at least one first electrode. The control circuitry varies the electrical power signal based on a position of the second cutting blade relative to the first cutting blade, a rotating speed of the second cutting blade, or both.
• A surgical cutting instrument having the above structure can selectively vaporize tissue or coagulate tissue depending on the electrical power signal supplied to the at least one first electrode by the control circuitry.
• According to some embodiments, the second cutting blade moves between a first position, at which the tissue to be cut is permitted to enter the cutting window of the first (outer) cutting blade, and a second position at which the tissue has been cut by the cutting window. The control circuitry supplies a first electrical power signal at least part of the time while the second cutting blade is in the first position, and supplies a second electrical power signal, which is different from the first electrical power signal, at least part of the time while the second cutting blade is in the second position. The first electrical power signal, for example, causes the tissue to be cut/vaporized. In accordance with some embodiments, the second electrical power signal causes the tissue to be coagulated/cauterized.
• According to other embodiments, the second electrical power signal is a zero power signal (that is, the second electrical power signal does not cause tissue vaporization or coagulation).
• According to some embodiments, the electrical power signal supplied by the control circuitry is a monopolar signal.
• According to some embodiments, an insulation layer is disposed over at least a portion of the distal end of the first cutting blade. In addition, at least one second electrode is located over at least a portion of the insulation layer and is electrically coupled to the control circuitry. In such an arrangement, the electrical power signal supplied by the control circuitry is a bipolar signal.
• According to preferred embodiments, suction is applied through the cutting window at the distal end of the first cutting blade.
• According to some embodiments, the second cutting blade rotates about a longitudinal axis of the surgical cutting instrument.
• According to other embodiments, the second cutting blade reciprocates in a longitudinal direction of the surgical cutting instrument.
• According to some embodiments, the control circuitry includes a sensor that senses a position of the second cutting blade relative to the first cutting blade, a rotational speed of the second cutting blade, or both. The control circuitry also preferably includes a processor that varies the electrical power signal based on the sensed position of the second cutting blade relative to the first cutting blade.
• According to some embodiments, the control circuitry includes at least one moving electrical contact coupled to the second cutting blade and at least one fixed contact that intermittently contacts the at least one moving electrical contact as the second cutting blade moves.
• According to some embodiments, the second cutting blade moves between a first position at which at least a part of the distal cutting portion faces the cutting window and a second position at which the distal cutting portion does not face the cutting window. In addition, the control circuitry supplies a first electrical power signal at least part of the time while the second cutting blade is in the first position, and a second electrical power signal, which is different from the first electrical power signal, at least part of the time while the second cutting blade is in the second position. The first electrical power signal can be sufficient to cause vaporization (electrical cutting) of tissue. The second electrical power signal can be sufficient to cause coagulation.
• A surgical cutting instrument according to another aspect of the invention includes a first cutting blade, a second cutting blade, at least one first electrode, a sensor and a processor. The first cutting blade has a tubular body with a proximal end and a distal end, and a cutting window is disposed at a side of the first cutting blade near the distal end. The second cutting blade has a tubular body with a proximal end and a distal end, and a cutting window is disposed at a side of the second cutting blade near the distal end. The second cutting blade is rotatably disposed inside of the first cutting blade such that the surgical cutting instrument cuts tissue by rotating the second cutting blade within the first cutting blade while a vacuum is applied through an internal bore of the second cutting blade to draw the tissue into the cutting windows of the first and second cutting blades and sever the tissue by rotation of the second cutting blade. The at least one first electrode is located adjacent to at least the cutting window at the distal end of the first cutting blade. The sensor senses a rotational position of the second cutting blade relative to the first cutting blade. The processor controls an electrical power signal supplied to the at least one first electrode at least partially based on the sensed rotational position of the second cutting blade relative to the first cutting blade. In particular, the processor supplies (i) a first electrical power signal at least part of the time while the cutting windows of the first and second cutting blades are aligned with each other, and (ii) a second electrical power signal, which is different from the first electrical power signal, at least part of the time while the cutting windows of the first and second cutting blades are not aligned with each other. The first electrical power signal can be sufficient to cause vaporization (electrical cutting) of tissue. The second electrical power signal can be sufficient to cause coagulation.
• A surgical cutting instrument according to another aspect of the invention includes first and second cutting blades, at least one first electrode, and control circuitry. The first cutting blade has a tubular body with a proximal end and a distal end, and a cutting window is disposed at a side of the first cutting blade near the distal end. The second cutting blade has a tubular body with a proximal end and a distal end, and a cutting window is disposed at a side of the second cutting blade near the distal end. The second cutting blade is rotatably disposed inside of the first cutting blade such that the surgical cutting instrument cuts tissue by rotating the second cutting blade within the first cutting blade while a vacuum is applied through an internal bore of the second cutting blade to draw the tissue into the cutting windows of the first and second cutting blades and sever the tissue by rotation of the second cutting blade. The at least one first electrode is located adjacent to at least the cutting window at the distal end of the first cutting blade. The control circuitry is coupled to at least the second cutting blade and supplies an electrical power signal to the at least one first electrode. In particular, the control circuitry supplies (i) a first electrical power signal at least part of the time while the cutting windows of the first and second cutting blades are aligned with each other, and (ii) a second electrical power signal, which is different from the first electrical power signal, at least part of the time while the cutting windows of the first and second cutting blades are not aligned with each other. The first electrical power signal can be sufficient to cause vaporization (electrical cutting) of tissue. The second electrical power signal can be sufficient to cause coagulation.
BRIEF DESCRIPTION OF THE DRAWINGS
• Various exemplary embodiments of the disclosed surgical instrument will be described in detail with reference to the following drawings in which:
• FIG. 1 illustrates a perspective view of a powered surgical instrument system that incorporates a surgical instrument, control unit, fluid source and suction source;
• FIG. 2 is a perspective view of an exemplary embodiment of a surgical instrument in accordance with the present disclosure;
• FIG. 3 is a side view, partially in perspective and partially in cross-section, of a surgical instrument having a rotation sensor system in accordance with an embodiment of the present disclosure;
• FIG. 4 is a side, cross-sectional view of theFIG. 3 surgical instrument distal tip with the cutting windows being in complete alignment;
• FIG. 5 is a side, cross-sectional view similar toFIG. 4, but with the cutting windows being in complete mis-alignment so that suction is not applied through the cutting windows;
• FIG. 6A is a cross-sectional view showing the magnetic members of an inner cutting blade and the magnetically permeable pieces of ferromagnetic material of the outer cutting blade;
• FIG. 6B is a view similar toFIG. 6A except that the inner cutting blade has rotated by 180° such that the direction of the magnetic flux induced in the magnetically permeable pieces has reversed;
• FIG. 7 shows a dual axis linear magnetic sensor positioned relative to the magnetically permeable member of the outer cutting blade;
• FIGS. 8A-8C show one embodiment in which the cutting instrument is provided with an electrode for receiving a monopolar signal;
• FIG. 9 shows an embodiment in which the cutting instrument is provided with two electrodes for receiving a bipolar signal;
• FIG. 10 is a side view of an embodiment in which a leaf spring contacts the drive gear of the inner cutting blade to provide a coagulation signal;
• FIG. 11 is a perspective view of theFIG. 10 inner cutting blade;
• FIG. 12 is a side view of an embodiment in which a leaf spring contacts an outer surface of the inner cutting blade to provide a coagulation signal;
• FIG. 13 is a cross-sectional view of theFIG. 12 inner cutting blade;
• FIG. 14 shows an embodiment that includes LVDTs to determine the relative positions of the inner and outer cutting blades;
• FIG. 15 is an end view of theFIG. 14 inner cutting blade;
• FIG. 16 shows another type of sensor arrangement for sensing the position of a cutting blade;
• FIGS. 17 and 18 are similar toFIGS. 10 and 11, but show an embodiment in which both coagulation energy and vaporization energy are selectively applied;
• FIG. 19 is a schematic view of a surgical cutting instrument in which the inner cutting blade reciprocates; and
• FIGS. 20 and 21 are perspective views of an embodiment in which the inner cutting blade rotates (about the longitudinal axis of the device) and reciprocates (along the longitudinal axis of the device).
DETAILED DESCRIPTION OF THE EMBODIMENTS
• The following exemplary embodiments are described below with reference to the figures in the context of human surgery, such as ear, nose and throat surgery, and in particular sinus surgery as well as head and neck surgery. The following exemplary embodiments may also be utilized in spinal surgery, orthopedic surgery, and various other surgical applications. All exemplary embodiments of the invention are intended to be used in any applicable field of endeavor.
• FIG. 1 is a schematic of a powered surgical instrument system. Except for the rotation sensor system, the electrodes and the control system, to be described hereafter, the system may be in accordance with the system described in U.S. Pat. No. 7,247,161, the disclosure of which is incorporated herein by reference in its entirety. Another system to which the invention is applicable is described in U.S. Pat. No. 7,318,831, the disclosure of which is incorporated herein by reference in its entirety. As shown inFIG. 1, the poweredsurgical instrument system1 includes a handle (or handpiece)2, a footswitch4 (with pedal12), fluid (liquid and/or gas)source22,suction source28, acontrol unit6,fluid pump5 and a fluid inlet/irrigation outlet7. The system is supplied with power from apower source16 such as a wall outlet. Thesuction source28 may be an external suction source such as provided by attachment to a facility suction outlet provided on a wall. Thehandpiece2 is connected, at its distal end, to asurgical instrument8. Thesurgical instrument8 in this embodiment includes a cutting tip at itsdistal end8A that is used, for example, to cut, shave, remove, resect and/or abrade tissue, bone and/or other bodily materials. One or more electrodes (to be discussed later) are provided on thesurgical instrument8. In order to simplify the drawings, the electrodes are not labeled inFIGS. 1-5.
• FIG. 2 illustrates a perspective view of an exemplary embodiment of thesurgical instrument8 in accordance with aspects of the invention. Theinstrument8 incorporates aninner tube9 and anouter tube10. In this exemplary embodiment, aninner tube hub13 is formed on the second end14 (seeFIG. 3) of theinner tube9 and anouter tube hub15 is formed on the second end17 (seeFIG. 3) of theouter tube10. For purposes of this disclosure, eachtube9/10 and itshub13/15 are collectively referred to as a “tube” or “member.” Theinner tube9 is inserted into afluid passage20 formed within theouter tube10 so that theinner tube9 is co-axially disposed within theouter tube10 until the external distal tip of theinner tube9 contacts the internal distal surface of theouter tube10. Theouter tube10 has a larger diameter than theinner tube9, thus allowing for insertion of theinner tube9 within theouter tube10. However, it should be appreciated that the inner and outer tubes will be pre-assembled prior to delivery to the customer. Thus, a customer will most likely not be inserting the inner tube into the outer tube. Irrigation liquid can be supplied to the surgical site by supplying the liquid to thepassage20 via aninlet26.
• The inner andouter tube hubs13,15 couple the inner andouter tubes9,10, respectively, to thehandpiece2. Once coupled to thehandpiece2, theouter tube10 will be fixed relative to thehandpiece2, but theinner tube9 will be rotatable relative to theouter tube10 and thehandpiece2.
• Referring toFIG. 3, which shows a perspective view of the tip8aand a cross-sectional view of thehandpiece2 and proximal ends of thecutting blades9 and10, theouter tube10 includes a cuttingwindow40 disposed at a side of its distal end. Thus, theouter tube10 can be referred to as a first cutting blade. Theinner tube9 also includes a cuttingwindow30 disposed at a side of its distal end. Thus, theinner tube9 can be referred to as a second cutting blade. The edges of the cuttingwindows30 and40 can be serrated, smooth or a combination of serrated and smooth to form cutting surfaces. As mentioned previously, theinner cutting blade9 rotates within theouter cutting blade10, and thus as theinner cutting blade9 rotates, the cuttingwindows30 and40 become aligned with each other as shown inFIG. 4 and then become misaligned with each other as shown inFIG. 5. When the cuttingwindows30 and40 are misaligned with each other as shown inFIG. 5, the side of theinner tube9 distal tip opposite from the cuttingwindow30 blocks the cuttingwindow40 of theouter cutting blade10.
• The first, orouter cutting blade10 thus is an outer tube having a proximal end and a distal end, with a cuttingwindow40 disposed at a side of thefirst cutting blade10 near the distal end.
• The inner,second cutting blade9 is a tubular body having a proximal end and a distal end, with cuttingwindow30 disposed at a side of its distal end. As mentioned previously, the second,inner cutting blade9 is rotatably disposed inside of the first,outer cutting blade10 such that thesurgical instrument8 cuts tissue by rotating the second,inner cutting blade9 within the first,outer cutting blade10 while a vacuum is applied through aninternal bore25 of thecutting blade9 to draw the tissue into the cuttingwindows30 and40 of thecutting blades9 and10 and sever the tissue by rotation of thecutting blade9. Thus, thecutting blade9 is an inner rotating member having a cutting member near its distal end. The inner rotating member need not be a tube. For example, the inner rotating member could be a shaft with a cutting member at its distal end. With such an arrangement, suction would be applied through the hollowouter tube10. Furthermore, the inner cutting member could be a tube or shaft that reciprocates in the direction of longitudinal axis LA instead of rotating. The inner member tube or shaft could rotate and reciprocate longitudinally.
• FIG. 3 also shows a rotation sensor system in accordance with an embodiment of the invention. The rotation sensor system of this embodiment is described in more detail in U.S. patent application Ser. No. 13/251,493 filed Oct. 3, 2011, the disclosure of which is incorporated herein by reference in its entirety. In order to detect the rotational position ofinner cutting blade9 relative toouter cutting blade10, a rotation sensor system is provided. The rotation sensor system includes amagnetic member50 provided on theinner cutting blade9 near the proximal end of the inner cutting blade9 (on hub13), a magneticallypermeable member60 provided on theouter cutting blade10 near the proximal end of the outer cutting blade (on hub15), and asensor70 provided on thehandpiece2. Thesensor70 senses the magnetic flux of the magneticallypermeable member60 adjacent to thesensor70. The output of thesensor70 is provided to acontroller100, which is part of thecontrol unit6, and includes, for example, a microprocessor (CPU), working memory (RAM) and storage (ROM) in which appropriate programs for using the output ofsensor70 are stored.
• The manner in which one embodiment functions will be described in conjunction withFIGS. 3,6A and6B. Thehandpiece2 includes a longitudinal axis LA. As shown inFIG. 3, themagnetic member50, the magneticallypermeable member60 and thesensor70 are radially aligned with each other with respect to the longitudinal axis of thehandpiece2. In particular, themagnetic member50 is disposed radially inward of the magneticallypermeable member60. (That is,magnetic member50 is closer to the longitudinal axis LA than is the magneticallypermeable member60.) In addition, the magneticallypermeable member60 is disposed radially inward of thesensor70. As shown inFIGS. 6A and 6B, themagnetic member50 includes two oppositely polarized magnets50aand50bdisposed at diametrically opposite positions relative to the longitudinal axis LA of theinner cutting blade9, which also corresponds to the longitudinal axis LA of thehandpiece2. The magnets50aand50bare positioned such that a polarity of an outwardly-facing pole of a first one of the magnets (50a) is opposite to a polarity of an outwardly-facing pole of a second one of the magnets (50b). If the symbol + signifies the North pole and the symbol − signifies the South pole, as shown inFIGS. 6A and 6B, magnet50ais arranged with its North pole facing radially outward, whereas magnet50bis arranged with its South pole facing radially outward.
• The magneticallypermeable member70 includes two semicircular pieces60aand60bof magnetically permeable material such as a ferromagnetic material (for example, NiFe). The two semicircular pieces60aand60bare located on opposite circumferential segments near the proximal end of thehub15 associated with theouter cutting blade10. Each of the pieces60aand60bextends almost one-half around the circumference of thehub15. Opposing ends of the two semicircular pieces of ferromagnetic material60a,60bare separated from each other by gaps G as shown inFIGS. 6A and 6B. Magnetic flux will be induced in the ferromagnetic pieces60aand60bbased on the polarity of the magnet surface (of magnets50aand50b) that is located adjacent to each particular ferromagnetic piece. When theinner cutting blade9 is positioned with its magnets50aand50bas shown inFIG. 6A, magnetically permeable material piece60awill have the same magnetic polarity as the outer face of magnet50a, whereas magnetically permeable piece60hwill have the same magnetic polarity as the outer face of magnet50b. When theinner cutting blade9 has rotated by 180°, as shown inFIG. 6B, the polarities of the magnetically permeable material pieces60aand60bwill be the opposite of that shown inFIG. 6A. Thus, as theinner cutting blade9 rotates relative to theouter cutting blade10, the polarities of the magnetically permeable material pieces60aand60bwill fluctuate (instantaneously switch) between the states shown inFIGS. 6A and 6B, with their polarities switching each time the magnets50aand50bpass by the gaps G. Accordingly, thesensor70 disposed adjacent to a portion of the magneticallypermeable material60 will sense the magnetic flux of the magnetically permeable material adjacent thereto, and thus will output a signal that fluctuates as theinner cutting blade9 rotates.
• FIG. 7 shows one example ofsensor70. According to a preferred embodiment,sensor70 is a dual axis linear magnetic sensor that senses magnetic flux in two perpendicular directions (the X direction and the Y direction). Thesensor70 is positioned relative to the magnetically permeable material pieces60aand60bsuch that one of its measurement axes (the X axis shown inFIG. 7) is normal to the adjacent surface of the magnetically permeable structure.
• It has been determined that, as long as thesensor70 is positioned radially close enough to the magnetically permeable pieces60aand/or60b, thesensor70 can effectively sense the instantaneous switching of the polarities of the magnetically permeable material located adjacent to the sensor regardless of where the sensor is located around the circumference of the magnetically permeable member defined by the magnetically permeable material pieces60aand60b. Accordingly, the disclosed arrangement is very effective at detecting the position of theinner cutting blade9 relative to theouter cutting blade10 even if the rotational orientation of theouter cutting blade10 relative to the handpiece2 (and thus relative to the sensor70) is changed.
• Because the positional relationship between the magnets50aand50band the cuttingwindow30 of theinner cutting blade9 is fixed, and because the positional relationship between the magnetically permeable material pieces60aand60band the cuttingwindow40 of theouter cutting blade10 is fixed, the signal output bysensor70 can be interpreted by signal processing software and/or hardware of thecontroller100 to determine the position of the cuttingwindows30 and40 relative to each other. For example, referring toFIG. 3, if the cuttingwindow40 ofouter cutting blade10 faces out of the page, the magnetically permeable material pieces60aand60bcould be arranged on thehub15 so that the gaps G are on the top side and the bottom side inFIG. 3 of thehub15. Similarly, if the cuttingwindow30 of theinner cutting blade9 faces out of the page as shown inFIG. 3, the magnets50aand50bcould be arranged so that they extend from the upper side and the lower side of thehub13 inFIG. 3. Accordingly, each time the magnets50aand50bare aligned with the gaps G, thewindows30 and40 either will be completely aligned as shown inFIG. 3 andFIG. 4, or completely misaligned as shown inFIG. 5. Thus, the position of the inner blade relative to the outer blade can be determined. The signal output bysensor70 also can be used to determine the rotational speed of the inner cutting blade.
• FIGS. 8A-8B show an embodiment in which the control circuitry (included in controller100) applies a monopolar signal to at least one electrode provided adjacent to the cutting edge of the cuttingwindow40 at the distal end of the first (outer) cuttingblade10. Because theouter cutting blade10 can be made of an electrically conductive material such as stainless steel, an electrical signal sufficient to perform electrical cutting (vaporization of tissue) or coagulation can be provided to the area adjacent to the cuttingwindow40 of theouter cutting blade10 simply by providing anelectrical connector40A (seeFIG. 3) near the proximal end of theouter cutting blade10. Theelectrical connector40A is attached to thecontroller100 and is provided with the appropriate signal (vaporization or coagulation) based on the detected position of theinner cutting blade9 relative to theouter cutting blade10 in accordance with one embodiment of the invention. As shown inFIGS. 8A-8C, aninsulative sheath90 is provided over theouter cutting blade10 so that the electrical energy (for vaporization or coagulation) is provided to tissue only at the distal end of theouter cutting blade10. In this regard, the distal end of cuttingblade10 functions as anelectrode10A.
• When the cuttingwindows30 and40 of the inner and outer cutting blades are in complete alignment as shown inFIG. 8A, thecontroller100 sends a first electrical signal that is sufficient to cause vaporization of tissue to theelectrode10A formed at the distal end of theouter cutting blade10. The first electrical signal continues to be applied as theinner cutting blade9 rotates from the open position shown inFIG. 8A to the closed position shown inFIG. 8C. That is, the first electrical signal, which is sufficient to induce tissue vaporization, also is applied while the instrument is in the state shown inFIG. 8B with the cuttingwindow40 partially closed due to rotation of theinner cutting blade9. Thus, tissue is cut due to the mechanical cutting action of the cuttingwindows30 and40 and due to the electrical vaporization signal provided to theelectrode10A. Once thewindow40 of theouter cutting blade10 becomes completely closed due to rotation of theinner cutting blade9, supply of the first electrical signal is stopped. Supply of the first electrical (vaporization) signal can start just before thewindows30/40 become aligned (or when or slightly after they become aligned) and can be stopped when (or slightly before or after) the cuttingwindow40 becomes completely blocked by theinner cutting blade9.
• If coagulation is desired, then a second electrical signal, different from the first electrical signal, is provided by thecontroller100 to theelectrode10A while the instrument is not performing any mechanical (or electrical) cutting of tissue. The second electrical signal is sufficient to achieve tissue coagulation, but preferably is not sufficient to achieve vaporization of tissue. Depending on the surgical procedure, hemostasis may not be an issue, and thus the value of the second electrical signal could be zero such that no coagulation energy is applied. If coagulation is desired, then the value of the second electrical signal can be a well known value effective at achieving coagulation of tissue.
• In the embodiment shown inFIGS. 8A-8B, the material of theouter cutting blade10 functions as an electrode. In order to restrict the area of the patient that receives the electrical energy, an electrically non-conductive coating or shrink tubing can be formed over the outer surface ofblade10, leaving the portion of the blade that is to function as the electrode uncovered. Alternatively, a separate electrically-conductive layer can be provided over the material that forms theouter cutting blade10 to form theelectrode10A. The electrically-conductive material could be provided over the entire outer surface of theouter cutting blade10, or it could be provided only at the distal end of theouter cutting blade10 adjacent to the cuttingwindow40.
• The embodiment shown inFIGS. 8A-8C is a monopolar embodiment and thus a separate return electrode is provided, for example, as a patch attached to the skin of the patient. The invention also is applicable to bipolar systems.
• FIG. 9 shows an example of a bipolar system. InFIG. 9, the distal end of theouter cutting blade10 forms anelectrode10A, which will function as a return electrode of the bipolar system. Aninsulation layer92 is formed over theouter cutting blade10. Anotherelectrode10B is formed as a layer of electrically-conductive material over theinsulation layer92.Electrode10B can function as the active electrode and will receive the signal (for example, to perform vaporization or coagulation) from thecontroller100. Anouter insulation layer90 is formed over theelectrode layer10B and protects areas of the patient which are not to be subjected to coagulation or cutting from receiving energy from theelectrode10B.
• In the embodiments described above, thecontroller100 is coupled to the electrode(s) of the outer cutting blade via anelectrical connector40A provided on an external surface near the proximal end of theouter cutting blade10. However, other connection arrangements are possible. For example, thecontroller100 could be coupled to the electrode(s) through thehub15 located within thehandpiece2.
• In the embodiment described above, the signal output fromrotation sensor70 is used bycontroller100 to determine the position of theinner cutting blade9 relative to theouter cutting blade10. Based on the determined relative position, an appropriately-controlled signal is provided bycontroller100 to the electrode(s) provided adjacent to the distal end of theouter cutting blade10. The signal can be sufficient for performing electrical cutting (vaporization) of tissue as described above. In addition, or alternatively, the signal can be appropriate for achieving coagulation of tissue as described above. Because it is only desirable to cut/vaporize tissue that is grasped by thewindows30/40 of thecutting blades9/10, the vaporization signal preferably is only supplied while tissue is being grasped by the cutting surfaces of thewindows30/40. That is, when theouter cutting window40 is completely closed due to the rotational position of theinner cutting blade9, the vaporization signal should not be supplied. Otherwise, other tissue in contact with the distal tip of theouter cutting blade10 could be undesirably vaporized. In addition, because there generally is no reason to coagulate tissue while the cutting is occurring, the coagulation signal (if it is provided) preferably is provided only while tissue cutting is not occurring (that is, while the cuttingwindow40 of theouter cutting blade10 is closed due to the rotational position of the inner cutting blade9). The coagulation signal also could be supplied during the period when the cuttingwindow40 begins to open because cutting is not occurring at that time. As noted previously, the coagulation signal can be provided even when the instrument is being used to perform only mechanical cutting (that is, the vaporization signal is not being used in conjunction with the mechanical cutting). In such an embodiment, the coagulation signal preferably is supplied only when the cuttingwindows30/40 are not cutting through tissue.
• As also noted previously, if electromechanical cutting is being conducted, then it is preferable to rotate theinner cutting blade9 at a speed slower than what is usually used to perform mechanical cutting. For example, the inner cutting blade can be rotated at less than about 60 rpm (revolutions per minute) if electromechanical cutting is being conducted. The slower rotation speed can be used due to the cutting assistance provided by the vaporization signal. Additionally, the slower rotation speed is preferable because it will make it easier for the surgeon to grasp more tissue with the instrument. The electromechanical action may provide a cleaner, more precise cut of larger “bites” of tissue compared with mechanical cutting. Purely mechanical cutting at higher speeds often chews (multiple rotations required to take a large “bite”) tissue, and may be limited to smaller “bites” of tissue due to the relatively small time frame in which the cutting window is open.
• In the first described embodiment,magnetic sensor70 is used to sense the relative positions of the inner and outer cutting blades, and then that sensed information is used bycontroller100 to control the signal that is supplied to the electrode(s). Some of the following more simple embodiments directly supply a signal (for example, a coagulation signal) to the electrode based on the relative positions of the inner and outer cutting blades without using a sensor.
• In the following embodiments, the electrical signal is provided to the inner cutting blade, and the electrical signal is provided only for performing coagulation. Because the inner andouter cutting blades9/10 preferably are made from electrically conductive material, supplying the electrical signal to theinner cutting blade9 will still result in the coagulation energy reaching the tissue after traveling through the distal end of theouter cutting blade10. That is, the inner and outer cutting blades are in physical and electrical contact with each other at least at their distal ends so that the signal will be conducted from the inner cutting blade to the outer cutting blade.
• FIGS. 10 and 11 show an embodiment in which the electrical signal is supplied to theinner cutting blade9 through agear9A that is used to couple theinner cutting blade9 to a motor that rotates the blade. InFIG. 10, the relative positions of the inner andouter cutting blades9/10 is such that the inner andouter cutting windows30/40 are misaligned (that is, theouter cutting window40 is blocked by the distal end of the inner cutting blade9). This is one position where it is desirable to provide coagulation energy. A generator supplies the coagulation signal to the handpiece. Inside the handpiece, anelectrical leaf spring200 made from a material such as BeCu is connected to the inner cutting blade9 (the distal tip of which functions as an electrode) through thegear9A. In particular, anelectrical pad210 is provided on a side surface of thedrive gear9A. Thedrive gear9A is made from a non-conducting material such as, for example, acetal.FIG. 11 shows theelectrical pad210 in more detail. Theelectrical pad210 is electrically connected to theinner cutting blade9 via aconductor220 such as a wire. As can be appreciated fromFIGS. 10 and 11, thepad210 extends along an arc such that it will remain in contact with theleaf spring200, and thus receive the coagulation signal, for a portion of each revolution of thecutting blade9. By precisely controlling the length of thepad210, the portion of each rotation of theinner cutting blade9 during which the coagulation signal is supplied to the distal tip of the instrument can be precisely controlled.
• FIGS. 12 and 13 show another embodiment. In the embodiment ofFIGS. 12 and 13, aleaf spring230, connected to a generator so as to receive the coagulation signal, rides on the outer surface of theinner cutting blade9. A portion of the outer surface ofinner cutting blade9 is covered by an electricallynon-conductive pad9B. When theleaf spring230 directly contacts the outer surface of theinner cutting blade9, the distal tip of the instrument will receive and apply coagulation energy to tissue in contact with the distal tip. When theleaf spring230 contacts thepad9B, no coagulation signal is provided to the distal tip of the instrument because thepad9B is electrically non-conductive and thus insulates thecutting blade9 from theleaf spring230. Again, the radial extent of thepad9B can be precisely controlled to affect the portion of theinner blade9 rotation during which the coagulation signal will not be supplied to the distal tip of the instrument.
• In the embodiments shown inFIGS. 10-13, the orientation of theouter cutting blade10 relative to thehandpiece2 is fixed and not adjustable. However, as is well known in the art, it is possible to adjust the orientation of theouter cutting blade10 relative to the handpiece (for example, so that the orientation of theouter cutting window40 can be adjusted).
• If the orientation of theouter cutting blade10 is adjustable, then information is needed with respect to the orientation of the outer cutting blade10 (more specifically, of the orientation of the outer cutting window40) so that the coagulation signal can be provided at the appropriate time (for example, when the cuttingwindows30 and40 are not in alignment).FIGS. 14-16 show embodiments in which information about the orientations of the inner andouter cutting blades9/10 can be obtained in order to control when the coagulation signal is to be supplied.
• In the embodiment ofFIGS. 14 and 15, each of thecutting blades9/10 includes an eccentric cam. In addition, a transducer or sensor such as, for example, a linear variable displacement transducer (LVDT) is provided to interact with each of the cams so as to obtain information about the position of the cutting blade associated with that cam. As shown inFIG. 14,inner cutting blade9 havinggear9A includes a cam320. LVDT340 having a sensor arm which contacts the outer periphery of the cam320 is used to detect the rotational position ofinner cutting blade9. As theinner cutting blade9 rotates, the sensor arm of LVDT340, which is biased toward and against the outer periphery of the cam, will move up and down, thus indicating the rotational position of theinner cutting blade9. Because the orientation of the cam with respect to the cuttingwindow30 of theblade9 is known, the signal will indicate the position of the cutting window30 (for example, with respect toFIGS. 14 and 15, information can be determined as to whether the cuttingwindow30 is pointing upward, downward, or to positions therebetween).Outer cutting blade10 has a similar cam310 and LVDT330. Before a cutting operation begins, the rotational position of theouter cutting blade10 can be adjusted relative to the handpiece2 (although theblade10 will not rotate during a cutting operation), and thus the LVDT330 can be used to determine the position to whichouter cutting blade10 has been adjusted. Thus, the location/orientation of theouter cutting window40 will be known.Controller100 receives the signals output from the LVDTs330 and340, and can thus determine when the cuttingwindows30 and40 are aligned and misaligned. Accordingly,controller100 can determine when the coagulation signal should be supplied to theinner cutting blade9, which is electrically coupled to a generator via thecontroller100.
• FIG. 16 shows a different type of transducer system. InFIG. 16, theinner cutting blade9 is provided with an outer ring400 having electrically conductive portions410 and electrically non-conductive portions420. Three electrically conductive pins450A,450B and450C are biased against the ring400. When the pins come into contact with one of the electrically conductive portions410, that condition can be detected. The positions of the pins450A-450C and of the electrically conductive portions410 can be chosen such that information about the position of the cuttingwindow30 on cuttingblade9 can be known. More or less than three pins can be provided as needed. A similar arrangement can be provided for theouter cutting blade10 if the outer cutting blade is adjustable relative to the handpiece.
• Although the embodiments ofFIGS. 10-16 were described with respect to applying a coagulation signal, the embodiments could be used to apply a vaporization signal or to apply both a coagulation signal and a vaporization signal. For example, referring to the embodiment ofFIGS. 10 and 11, an electrical pad similar toelectrical pad210 can be provided in alignment with the cutting window30 (rather than out of alignment with the cuttingwindow30 as is pad210) and an additional leaf spring similar toleaf spring200 but coupled to a vaporization signal generator can be provided to alternately contact the electrical pad. If both vaporization and coagulation signals are to be applied, the electrical pad for vaporization and theelectrical pad210 for coagulation can be provided at different radial positions on thegear9A.
• FIGS. 17 and 18 show a modified version of the embodiment ofFIGS. 10 and 11 in which coagulation and vaporization signals are selectively applied. A generator supplies the coagulation signal and the vaporization signal to the handpiece. Inside the handpiece, a firstelectrical leaf spring200 made from a material such as BeCu is connected to the inner cutting blade9 (the distal tip of which functions as an electrode) through thegear9A. In particular, a firstelectrical pad210 is provided on a side surface of thedrive gear9A. Thedrive gear9A is made from a non-conducting material such as, for example, acetal.FIG. 18 shows the firstelectrical pad210 in more detail. The firstelectrical pad210 is electrically connected to theinner cutting blade9 via afirst conductor220 such as a wire. As can be appreciated fromFIGS. 17 and 18, thefirst pad210 extends along an arc such that it will remain in contact with thefirst leaf spring200, and thus receive the coagulation signal, for a portion of each revolution of thecutting blade9. By precisely controlling the length of thefirst pad210, the portion of each rotation of theinner cutting blade9 during which the coagulation signal is supplied to the distal tip of the instrument can be precisely controlled. A secondelectrical pad210A is provided on the side surface of thedrive gear9A. Thesecond pad210A can be provided on the same side of thedrive gear9A as thefirst pad210, or on the opposite side of thegear9A.FIG. 18 shows the secondelectrical pad210A in more detail. The secondelectrical pad210A is electrically connected to theinner cutting blade9 via asecond conductor220A such as a wire. As can be appreciated fromFIGS. 17 and 18, thesecond pad210A extends along an arc such that it will remain in contact with asecond leaf spring200A, and thus receive the vaporization signal, for a portion of each revolution of thecutting blade9. By precisely controlling the length of thesecond pad210A, the portion of each rotation of theinner cutting blade9 during which the vaporization signal is supplied to the distal tip of the instrument can be precisely controlled. Thesecond pad210A is located radially farther away from the center of thegear9A than is thefirst pad210 so thatsecond pad210A will only contactsecond leaf spring200A, and so thatfirst pad210 will only contactfirst leaf spring200.
• As noted previously, theinner cutting blade9 can reciprocate along the longitudinal axis LA of the instrument instead of rotating about the longitudinal axis. In addition, theinner cutting blade9 can reciprocate and rotate.FIG. 19 shows an example of an inner cutting blade that reciprocates and rotates.
• FIG. 19 is a schematic drawing of a variation of any of the previously described embodiments in which theinner cutting blade9′ (having cutting window30) reciprocates in the direction of arrow A in the longitudinal axis direction of the surgical instrument. Adrive mechanism180 drives the inner cutting blade in the longitudinal axis direction. Any well known type of drive mechanism can be used. For example, the longitudinal reciprocation drive mechanism disclosed in U.S. Pat. No. 5,106,364, the disclosure of which is incorporated herein by reference in its entirety, can be used. Theinner cutting blade9/9′ also could be rotated and reciprocated.
• FIGS. 20 and 21 are perspective, exploded views of a drive mechanism that rotates and reciprocates theinner cutting blade9. The reciprocal gear mechanism is based on a level-wind gear mechanism commonly seen in various consumer products such as fishing reels and hose take-up reels. The reciprocal gear has a single continuous helical groove, or track,110 that winds in both right-hand and left-hand directions along the outer surface of thegear body105. An inner hub (not shown) is rigidly affixed to the proximal portion of the inner drive member and transfers the input rotational motion from the powered handpiece. A proximal portion of the inner drive member is rigidly fixed to the proximal end of the gear. Afollower pin120 is mounted in a stationaryouter tube assembly130 and extends throughhole132 in that assembly, and causes thegear105 to reciprocate axially as it is driven by the handpiece. Thepin120 is allowed to rotate on its axis at the ends of the stroke, as thetrack110 changes direction and rotates the opposite way. Theouter tube assembly130 and pin120 are rigidly affixed to anouter hub150, all of which remain stationary while the device is in use. Thepin120 is constructed with a “wishbone” shape, which allows the leading edge of the pin to be guided into thecorrect track110 by the trailing edge of the pin. Because thepin120 straddles thegear105, either the leading or trailing portion of thepin120 is always engaged in the groove of the gear, even where the right-hand and left-hand portions of the track cross one another.
• On the distal end of thegear body105, the distal portion of theinner cutting blade9 is axially constrained (but not necessarily rotationally constrained) to the gear such that the linear motion of thegear105 is translated to the distal section of theinner cutting blade9. If theinner cutting blade9 both rotates and reciprocates, thecutting blade9 is fixed to thegear105 with respect to both rotation and translation. If theinner cutting blade9 only reciprocates (but remains in plane with the outer cutting blade10), thecutting blade9 is allowed to rotate with respect to thegear105. However, the distal section of theinner cutting blade9 is pinned or otherwise affixed in plane to theouter cutting blade10 to allow reciprocation, but not rotation. For example, aguide pin140 extends through a hole in thecutting blade9 and rides in a channel on an outer surface of thegear105 near the distal end of thegear105 so that thecutting blade9 is axially fixed to thegear105, but can rotate with respect to thegear105. Theguide pin140 also passes through aslot134 in theouter tube assembly130 so that the inner andouter blades9 and10 remain properly aligned (if theinner blade9 only reciprocates). Theguide pin140 and slot would be omitted if theinner blade9 also rotated with respect to theouter blade10.
• The construction of the remainder of the device (for example, the distal ends of the inner and outer cutting blades and the vacuum and liquid supply passages) can be similar to what was described above for the previous embodiments. The stroke of the inner cutting blade assembly is determined by the axial length of the groove. The gear relationship between rotation and reciprocation is based on the number of turns in the gear to complete the length of the track (stroke) on the gear. For example, if the gear track makes three turns to complete the retrograde stroke and three turns to complete the prograde stroke, and the input speed from the handpiece is 12,000 rpm, then, for a device that rotates and reciprocates, the distal cutting tip will rotate at 12,000 rpm and reciprocate at 2,000 rpm (three turns retrograde and three turns prograde equals six rotations to complete one full reciprocal stroke). In general, a longer stroke allows a greater motion ratio between rotation and reciprocation.
• In the illustrated embodiment, the inner andouter cutting blades9 and10 are straight. However, thesurgical instrument8 can have one or more bends in it such that it is not straight. In such an arrangement, theinner cutting blade9 would be flexible. Flexible hollow cutting blades are known and used with curved cutting instruments. See, for example, U.S. Pat. No. 4,646,738, the disclosure of which is incorporated herein by reference in its entirety, and see, for example, U.S. Pat. No. 5,707,350, the disclosure of which is incorporated herein by reference in its entirety.
• The illustrated exemplary embodiments of the surgical tool as set forth above are intended to be illustrative and not limiting. Various changes may be made without departing from the spirit and scope of the invention.

Claims (17)

What is claimed is:

1. A surgical cutting instrument comprising:

a first cutting blade having a tubular body with a distal end and a proximal end, a cutting window that is sideward-facing disposed at the distal end and including a cutting edge;

a second cutting blade movably disposed inside the first cutting blade and having a distal cutting portion that, together with the cutting edge of the cutting window, cuts tissue by moving within the first cutting blade;

at least one first electrode located adjacent to at least the cutting edge at the distal end of the first cutting blade; and

control circuitry configured to control an electrical power signal supplied to the at least one first electrode, the control circuitry varying the electrical power signal based on a position of the second cutting blade relative to the first cutting blade, a rotating speed of the second cutting blade, or both.

2. The surgical cutting instrument ofclaim 1, wherein:

the second cutting blade moves between a first position at which the tissue to be cut is permitted to enter the cutting window, and a second position at which the tissue has been cut by the cutting window, and

the control circuitry supplies (i) a first electrical power signal at least part of the time while the second cutting blade is in the first position, and (ii) a second electrical power signal, which is different from the first electrical power signal, at least part of the time while the second cutting blade is in the second position.

3. The surgical cutting instrument ofclaim 2, wherein the first electrical power signal causes the tissue to be cut.

4. The surgical cutting instrument ofclaim 3, wherein the second electrical power signal causes the tissue to be coagulated.

5. The surgical cutting instrument ofclaim 3, wherein the second electrical power signal is a zero power signal.

6. The surgical cutting instrument ofclaim 2, wherein the second electrical power signal causes the tissue to be coagulated.

7. The surgical cutting instrument ofclaim 6, wherein the first electrical power signal is a zero power signal.

8. The surgical cutting instrument ofclaim 1, wherein the electrical power signal supplied by the control circuitry is a monopolar signal.

9. The surgical cutting instrument ofclaim 1, further comprising:

an insulation layer disposed over at least a portion of the distal end of the first cutting blade; and

at least one second electrode located over at least a portion of the insulation layer and electrically coupled to the control circuitry,

wherein the electrical power signal supplied by the control circuitry is a bipolar signal.

10. The surgical cutting instrument ofclaim 1, wherein suction is applied through the cutting window at the distal end of the first cutting blade.

11. The surgical cutting instrument ofclaim 1, wherein the second cutting blade rotates about a longitudinal axis of the surgical cutting instrument.

12. The surgical cutting instrument ofclaim 1, wherein the second cutting blade reciprocates in a longitudinal direction of the surgical cutting instrument.

13. The surgical cutting instrument ofclaim 1, wherein the control circuitry includes:

a sensor that senses a position of the second cutting blade relative to the first cutting blade, a rotational speed of the second cutting blade, or both, and

a processor that varies the electrical power signal based on the sensed position of the second cutting blade relative to the first cutting blade.

14. The surgical cutting instrument ofclaim 1, wherein the control circuitry includes:

at least one moving electrical contact coupled to the second cutting blade, and

at least one fixed contact that intermittently contacts the at least one moving electrical contact as the second cutting blade moves.

15. The surgical cutting instrument ofclaim 1, wherein:

the second cutting blade moves between a first position at which at least a part of the distal cutting portion faces the cutting window, and a second position at which the distal cutting portion does not face the cutting window, and

the control circuitry supplies (i) a first electrical power signal at least part of the time while the second cutting blade is in the first position, and (ii) a second electrical power signal, which is different from the first electrical power signal, at least part of the time while the second cutting blade is in the second position.

16. A surgical cutting instrument comprising:

a first cutting blade having a tubular body with a proximal end and a distal end, a cutting window disposed at a side of the first cutting blade near the distal end;

a second cutting blade having a tubular body with a proximal end and a distal end, a cutting window disposed at a side of the second cutting blade near the distal end, the second cutting blade rotatably disposed inside of the first cutting blade such that the surgical cutting instrument cuts tissue by rotating the second cutting blade within the first cutting blade while a vacuum is applied through an internal bore of the second cutting blade to draw the tissue into the cutting windows of the first and second cutting blades and sever the tissue by rotation of the second cutting blade;

at least one first electrode located adjacent to at least the cutting window at the distal end of the first cutting blade;

a sensor that senses a rotational position of the second cutting blade relative to the first cutting blade; and

a processor that controls an electrical power signal supplied to the at least one first electrode at least partially based on the sensed rotational position of the second cutting blade relative to the first cutting blade, the processor supplying (i) a first electrical power signal at least part of the time while the cutting windows of the first and second cutting blades are aligned with each other, and (ii) a second electrical power signal, which is different from the first electrical power signal, at least part of the time while the cutting windows of the first and second cutting blades are not aligned with each other.

17. A surgical cutting instrument comprising:

a first cutting blade having a tubular body with a proximal end and a distal end, a cutting window disposed at a side of the first cutting blade near the distal end;

a second cutting blade having a tubular body with a proximal end and a distal end, a cutting window disposed at a side of the second cutting blade near the distal end, the second cutting blade rotatably disposed inside of the first cutting blade such that the surgical cutting instrument cuts tissue by rotating the second cutting blade within the first cutting blade while a vacuum is applied through an internal bore of the second cutting blade to draw the tissue into the cutting windows of the first and second cutting blades and sever the tissue by rotation of the second cutting blade;

at least one first electrode located adjacent to at least the cutting window at the distal end of the first cutting blade; and

control circuitry coupled to at least the second cutting blade and that supplies an electrical power signal to the at least one first electrode, the control circuitry supplying (i) a first electrical power signal at least part of the time while the cutting windows of the first and second cutting blades are aligned with each other, and (ii) a second electrical power signal, which is different from the first electrical power signal, at least part of the time while the cutting windows of the first and second cutting blades are not aligned with each other.

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