Abstract:
A high-speed surgical handpiece ( 10 ) of the kind suitable for vitreoretinal surgery having a cutter ( 44 ) and an actuator ( 310 ). The cutter ( 44 ) is a guillotine-type cutter activated by a spring-mass system excited at harmonic frequency by a piezoelectric actuator ( 310 ) that receives a driving signal from a driving controller. The controller can have control and display units with a plurality of input mechanisms receiving input from a user. The control unit produces a piezoelectric actuator output signal to excite the spring-mass system at harmonic frequency. Fast cutting rates with reduced duty cycle as well as a proportional mode of operation are available. Low degrees of vibration and noise generation are produced.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention is related to electrically operated surgical systems, and more particularly to a surgical system of the kind suitable for vitreoretinal surgery powered by a resonating piezoelectric mechanism.  
       BACKGROUND OF THE INVENTION  
       [0002]     The intraocular portion of current vitrectomy probes typically consists in a closed end outer tube having a distal end sideport to aspirate the vitreous, and an inner tube that oscillates axially during operation in a way that the distal end sharp edge can displace with a cutting action across said sideport.  
         [0003]     Oscillation of the inner tube is typically provided by pneumatic turbines and electric rotary motors. Also, diaphragm based pneumatic systems have been used operated by fast changes in pressure levels inside a gas chamber at the handpiece proximal portion. These changes in pressure levels are console driven typically consisting in the alternation of positive and negative pressure cycles at the operation frequency desired for the cutter.  
         [0004]     Vacuum applied by a vacuum source in fluid communication with the hollow oscillating tube aspirates the vitreous into the sideport and the axially oscillating inner tube distal end sharp edges cut the vitreous allowing the aspiration and removal of the vitreous and any other intraocular material to be removed. A fluid source in direct communication with the intraocular cavity can provide pressurized balanced salt solution to replace the volume of the removed vitreous.  
         [0005]     There would be advantage in increasing the speed of operation of vitrectomy cutters as less traction would be applied to the vitreous body and the displacement of tissue into the aspirating sideport would be more controlled and continuous. Currently available pneumatic vitreous cutters can operate up to 2.500 cuts per minute but typically exhibit a reduced duty cycle.  
         [0006]     Electrically driven vitreous cutters can operate at higher speeds, up to 3.000 cuts per minute, but are typically heavy, delicate and vibrate during operation. These details have been exposed in U.S. Pat. No. 6,575,990 the one I incorporate here as a reference. U.S. Pat. No. 6,875,221 and USPTO co-pending application Ser. No. 11/164,164 are also cited here with its accompanying references to provide background for the present description.  
         [0007]     Typically, the speed of the cutting blade of currently available electrically operated vitrectomy handpieces is proportional to the cut rate. When operating at low cut rates, the blade traverses the cutting sideport at a lower speed than when operating at higher cutting rates. This mode of operation is related to the rotary coupled mechanism of many electric vitrectomy handpieces.  
         [0008]     Pneumatic handpieces exhibit a progressive increase of the closed-to-open ratio as the cut rate is increased, as physical limitations apply to recycle the guillotine cutter with its biasing preloading spring. One limitation of pneumatic vitreous cutters operating at high speed is that the closed-to-open ratio progressively increases as the operating speed is increased.  
         [0009]     This increase of the portion of the cycle where the sideport is closed with respect to the duration of one full cycle reduces cutter efficiency as less time is available for vacuum to aspirate vitreous tissue into the sideport for the cutting and aspirating action.  
         [0010]     The reduced efficiency increases surgical time increasing complications such as post-vitrectomy cataract formation and reduces operating room turn around.  
         [0011]     Another limitation of current vitrectomy cutters operating at high speed is that there can be vibration of the tip of the surgical instrument related to movements of the internal mechanisms used to power the cutting edges.  
         [0012]     Another limitation of current vitrectomy cutters is that regulation of the open sideport area cannot be adjusted or requires manual mechanical adjustments at handpiece level.  
         [0013]     Still another limitation of current vitrectomy cutters operated at high speed is that the vibration of the internal mechanisms used to power the cutting edges produces noise.  
         [0014]     There is still a need for vitrectomy cutters that can operate in the high speed range to cut the vitreous.  
         [0015]     Also, there is a need for vitrectomy cutters providing maximum sideport open ratios preferably above 50% when operating at cut rates above 1.500 cuts per minute.  
         [0016]     Also, there is a need for electric vitrectomy cutters that allow an operator to adjust the maximally open sideport dimensions.  
         [0017]     Also there is the need for a high speed vitreous cutting handpiece that is lightweight, operates silently and produces a minimum of vibration.  
         [0018]     Also there is the need for a high speed vitreous cutting handpiece that is mechanically simple allowing repeated sterilization and providing reduced wear and failure rates.  
         [0019]     It is an object of the present invention to provide a vitreous cutter mechanism that allows a fast cutting speed of the cutting edge across the aspirating sideport.  
         [0020]     It is another object of the present invention to provide a vitrectomy probe that can operate efficiently at speeds above 2.000 cuts per minute.  
         [0021]     It is still another object of the present invention to provide a vitreous cutter handpiece where the open sideport ratio is above 50% at high operating frequencies.  
         [0022]     It is still another object of the present invention to provide an electric vitreous cutter handpiece that allows adjustment of the position of the cutting border within a vitrectomy handpiece cutting sideport to regulate the effective area of the open sideport.  
         [0023]     It is still another object of the present invention to provide a vitreous cutter handpiece that also allows an operator to displace the cutting border across a vitrectomy sideport following a footpedal command or other proportional user interface inputs.  
         [0024]     It is still another object of the present invention to provide a vitreous cutter handpiece that operates silently and that produces a minimum of actuator-related vibration during operation.  
         [0025]     It is still another object of the present invention to provide a vitreous cutter handpiece that is lightweight and resistant to sterilization.  
         [0026]     It is still another object of the present invention to provide a vitreous cutter mechanism that is mechanically simple with reduced wear and failure rates. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     The features of the invention believed to be novel are set forth in the appended claims. The invention, however, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawing(s) summarized below.  
         [0028]      FIG. 1  depicts a schematic view of a vitrectomy system incorporating the handpiece of the present invention.  
         [0029]      FIG. 2  depicts a schematic external view of the vitrectomy handpiece.  
         [0030]      FIG. 3A  is a schematic lateral view of the handpiece of the present invention with a direct piezoelectric actuator and attached spring-mass system in compressed state driving the guillotine to the open position.  
         [0031]      FIG. 3B  is a schematic lateral view of the handpiece of the present invention with the direct piezoelectric actuator and attached spring-mass system in expanded state driving the guillotine to the closed position.  
         [0032]      FIG. 4A  is a schematic lateral view of the handpiece of the present invention with an amplified piezoelectric actuator and spring-mass system in compressed state driving the guillotine to the open position.  
         [0033]      FIG. 4B  is a schematic lateral view of the handpiece of the present invention with an amplified piezoelectric actuator and spring-mass system in expanded state driving the guillotine to the closed position.  
         [0034]      FIG. 5  is a schematic lateral view of the handpiece of the present invention with a direct piezoelectric actuator and attached spring-mass system mounted on an operator adjustable screw based support to regulate the maximally open sideport dimensions.  
         [0035]      FIG. 6  is a schematic lateral view of the handpiece of the present invention with a direct piezoelectric actuator and attached spring-mass system mounted on an axially adjustable support operated by a linear actuator to regulate the maximally open sideport dimensions.  
         [0036]      FIG. 7  is a schematic lateral view of the handpiece of the present invention including a twin mass system to provide axial vibration canceling.  
         [0037]      FIG. 8  is a schematic diagram of a vitrectomy system incorporating the handpiece of the present invention.  
         [0038]      FIG. 9  includes a graph depicting the typical behavior of an un-damped spring-mass system of the present invention excited at harmonic frequency. 
     
    
     LIST OF REFERENCE NUMERALS  
       [0039]     Surgical handpiece  10 , vitrectomy probe proximal end  11 , vitrectomy probe  12 , vitrectomy probe distal end  13 , vitrectomy probe sideport  14 , guillotine cutting edge  15 , surgical handpiece body  16 , detachable head  17 , aspiration port  18 , aspiration tubing  19 , surgical handpiece cable  20 , actuator driver cable  21 , piezoelectric actuator cable  22 , position sensor cable  23 , Vibration sensor cable  24 , body-head coupling  29 , amplified piezoelectric actuator  30 , actuator connection pad  32 , amplified piezoelectric actuator leveraging fame  34 , piezoelectric actuator  36 , interlock coupling  40 , aspiration duct  42 , guillotine  44 , surgical system console  70 , user interface  71 , controls  72 , display  73 , footpedal  74 , footpedal cable  75 , footpedal connector  76 , aspiration tubing connector  77 , surgical handpiece cable connector  78 , position sensor  80 , position sensor cable  81 , pressurized balanced salt solution  90 , solenoid  92 , infusion tubing  94 , eye  96 , irrigation incision  97 , vitrectomy probe incision  98 , spring  300 , rod guide  302 , cavity guide  304 , mass  306 , coupling connector  306 , piezoelectric actuator  310 , spring  400 , rod guide  402 , cavity guide  404 , mass  406 , piezoelectric actuator  408 , fixating assembly  450 , bias adjustment screw  500 , piezoelectric actuator support  502 , thread  504 , linear actuator  540 , stopper/damper  600 , spring  800 , male guide  802 , female guide  804 , mass  806 .  
       SUMMARY OF THE INVENTION  
       [0040]     A vitrectomy handpiece powered by a piezoelectric actuator driving a guillotine based vitreous cutter using a spring-mass mechanism under harmonic excitation to increase stroke and provide high speed of operation.  
       DETAILED DESCRIPTION  
       [0041]     A surgical system incorporating a vitrectomy handpiece  10  of the present invention as shown in FIGS.  1  to  8  is composed of a vitrectomy console  70  including a user interface  71  with operator controls  72  and a display  73 . A source of pressurized balanced salt solution  90  can be delivered into an eye  96  through an infusion tubing  94  placed across a solenoid  92  and into an irrigation incision  97  of an eye  96 . A footpedal  74  is connected to console  70  through a cable  75  and a connector  76 .  
         [0042]     Console  70  can also provide to vitrectomy handpiece  10  a source of vacuum through a connector  77  and an aspiration tubing  19  inserted into an aspiration port  18 , with vitrectomy handpiece  10  eventually inserted into eye  96  through a vitrectomy incision  98 . A connector  78  provides electric communication between console  70  across electric conductor cables  20 ,  21 ,  22 ,  23  with actuators  30 ,  310 ,  408  and sensor elements  80 ,  410  inside a body  16  of handpiece  10 . Referring now to  FIGS. 1 and 2 , handpiece  10  of the present invention is composed of a body  16  and a detachable head  17 .  
         [0043]     Detachable head  17  includes a hollow vitrectomy probe  12  having a proximal end  11  and a distal end  13 . A vitrectomy sideport  14  is preferably located near vitrectomy probe  12  distal end  13 . Aspiration port  18  is in fluid communication with sideport  14  through a tubing  42 .  
         [0044]     Aspiration port  18  can connect through aspiration tubing  19  and connector  77  with an aspiration source provided by vitrectomy console  70 . The vitreous cutting mechanism of handpiece  10  of the present invention is activated by the action of piezoelectric electro-mechanic actuators. It is known fact that typical single element or stack based piezoelectric actuators provide high force but limited displacement.  
         [0045]     The guillotine cutter of a vitrectomy handpiece will require a stroke above 700 microns to fully displace across a typical vitrectomy sideport. This stroke cannot be achieved using direct piezoelectric actuators in a typical configuration within the practical dimensions and weight of a standard vitrectomy handpiece. This invention is based on the use of conventional or leveraged piezoelectric actuators to activate a vitrectomy handpiece.  
         [0046]     Direct actuators such as Cedrat PPA-20M Parallel Pre-Stressed actuator or amplified piezoelectric actuators such as Cedrat APA50XS can be used with advantage in this application (Cedrat Technologies, 15 Chemin de Malacher, ZIRST, 38246 Meylan Cedex, France, http://www.cedrat.com). Also, piezoelectric actuators based on telescopic architectures or disk translators, such as P-288 HVPZT provided by Physik Instrumente can be used. Each of these architectures has its characteristic static, quasi-static and dynamic properties and can be used in different embodiments of this invention.  
         [0047]     The required stroke for a typical vitrectomy guillotine is above 700 microns. Piezoelectric actuators produce small strokes with high force. The present invention uses a piezoelectric actuator to produce harmonic excitation of a spring-mass system amplifying the stroke to operate a vitrectomy handpiece. Proper selection of spring characteristics, mass, and dampening allows operation of the vitrectomy guillotine at the desired stroke and frequency. In the preferred embodiment for the present invention handpiece body  16  contains a piezoelectric actuator  310  receiving cable  21  at connector  32 . One end of piezoelectric actuator  310  is fixed to handpiece body  16 , while the opposing free end of piezoelectric actuator  310  is coupled with a mass  306  through a spring  300 . Mass  306  connects through a connector/coupling  306  with a guillotine  44  having a cutting border  15 .  
         [0048]     A stopper/damper mechanism  600  fixated to handpiece body  16  can be incorporated to regulate system dynamics at resonant frequency. An optional male guide  302  fits in a complementary female guide  304  within mass  304  to allow a single degree of freedom (DOF) of displacement of mass  304  in the axis of operation of piezoelectric actuator  310 . As depicted in FIGS.  3  to  7 , detachable head  17  includes hollow vitrectomy probe  12  with an internally disposed guillotine cutter  44  with a cutting border  15  sliding with a cutting action across the inner aspect of sideport  12 . When not occluded by guillotine cutter  44 , sideport  12  is in fluid communication with aspiration port  18  through an aspiration channel inside hollow vitrectomy needle  12 , and fluid connector  42 .  
         [0049]     Aspiration port  18  can be connected to a vacuum source typically provided by vitrectomy console  70 . Hollow vitrectomy needle  12 , guillotine  44 , aspiration port  18  and vacuum connector  42  are incorporated into handpiece head  17  that can be detachably connected to operate in conjunction with handpiece body  16 . Head  17  is detachably connected using an attachment mechanism  19  preferably based on a bayonet or threaded coupling.  
         [0050]     The position sensor element  80  can be constituted by one or more strain gauges, Eddy current sensors, capacitive position sensors, optical position sensors, LVDTs or any other position sensor elements suitable to detect in real time the axial position and displacement information of the oscillating spring-mass mechanism and of the driving piezoelectric actuator. Position sensor element  80  connects to console  70  sequentially through cables  23 ,  20  and connector  78 .  
         [0051]     Piezoelectric actuator  310  can incorporate a position sensor  82  preferably in the form of a strain gage to inform a controller system the displacement of the actuator independently of the displacement of the complete spring mass system. Position sensor  82  connects to console  70  sequentially through cables  22 ,  20  and connector  78 .  
         [0052]     During operation, an operator holds handpiece  10  by its body  16  and the hollow vitrectomy needle  12  can be inserted into an eye  96  through an incision  98 . An aspiration source can be connected to port  18  in fluid communication with cutting port  14 . Irrigation solution can be provided to the interior of eye  96  through an irrigation line  94  using an irrigation incision  97 . Following an operator commands a suitable electrical signal is provided by vitrectomy console  70  through cables  20  and  21 , the voltage typically ranging between −20 and +150 volts and following a sine-wave.  
         [0053]     According to the piezoelectric effect, a varying voltage level will make the piezoelectric actuator  310  to axially expand and contract describing a sinusoidal path with a stroke proportional to the amplitude of the applied driving signal. For a typical direct piezoelectric actuator for use in this application, the maximum stroke can reach 20 microns. The axial displacement of actuator  310  is transmitted to the spring-mass system composed by spring  300 , mass  306  and the mass added by coupling  306  and guillotine  44 .  
         [0054]     An optional damper and stopper mechanism is conformed between the body of coupling  306  and handpiece body  16 . This miniature damper is preferably designed to operate in viscous under-damped modality. Shear forces and the under-dampening effect of the damper/stopper mechanism  600  are considered for tuning the system for operation.  
         [0055]      FIG. 11  depicts the formulas and dynamics that apply to the spring-mass mechanism of operation of the present invention. It is desirable that the spring-mass system is un-damped or under-damped to operate continuously at harmonic frequency. At design time, stiffness of spring  300  and the value of the total mass of the spring-mass system together with any present damping forces are determined to operate in harmonic excitation at a selected frequency of operation, with a desired stroke.  
         [0056]     As a mode of example only, by selecting a spring with a stiffness of 1 N/mm and a total mass of 10 grams, the system will have its first resonant frequency at 50.3 Hertz, allowing a guillotine cutter system to operate at approximately 3.000 cuts per minute. The PPA-20M actuator has a blocked-free resonating frequency of 21.250 Hertz. For this reason, to operate the system at 50.3 Hertz in the first resonant frequency, the actuator is driven in non-resonant mode to provide 20 microns of sinusoidal displacement at 50.3 hertz. In this way, the spring-mass system composed by spring  300 , mass  306 , and the masses of coupling  306  and of guillotine  44  are subjected to harmonic excitation, oscillating at amplitudes that are approximately 40 times bigger than the amplitude of oscillation of the excitation actuator  310  to achieve an axial stroke of guillotine  44  of 800 microns.  
         [0057]     An optional displacement sensor  80  can be used to continuously monitor operation of the handpiece by the surgical handpiece controller system to determine proper oscillation of guillotine  44 . Shifts in resonant frequency of the spring-mass system are corrected at controller level to maintain the stroke at a constant level during operation. Also, changes in the stroke of guillotine  44  are adjusted by modifying the driving signal provided to the piezoelectric actuator. Considering a stroke amplification of 40 times to obtain 800 microns guillotine stroke from a piezoelectric actuator providing 20 microns stroke, a proper combination of spring stiffness and total mass for the spring-mass system is selected at design time to operate at a desired frequency. In a simple mode of operation, the system is adjusted to have the cutting border  15  midway across sideport  14  in resting position. Once activated, the resonant system oscillates around this center point to the fully open and fully closed position to perform the vitreous aspiration and cutting action. This modality provides a sideport  14  open-to-closed ratio of 1/1 (or 50% duty cycle) and leaves sideport  14  half closed when not oscillating.  
         [0058]     To increase the open-to-closed ratio and also to provide a sideport  14  that is fully open when guillotine  15  is not oscillating, an offset can be applied to the cutting border  15  in resting position. This mode of operation requires an increase in stroke for proper operation up to 100%, but provides a fully open sideport  14  when guillotine  44  is not oscillating, and can also increase sideport  14  open-to-close ratio 2/1 (or 66% duty cycle) or above. A piezoelectric actuator controller system can keep track of proper operation of the actuator-spring-mass system by monitoring mass position sensor  80  and/or piezoelectric actuator position sensor  82 .  
         [0059]     As depicted in  FIGS. 4A and 4B , an amplified piezoelectric actuator  30  can be used instead of a direct piezoelectric actuator. In this configuration, the leveraged piezoelectric actuator has a piezoelectric element  36  perpendicularly disposed inside a frame  34 . Sinusoidal activation of the piezoelectric element  36  produces a sinusoidal oscillation of the amplified actuator with increased stroke. As a mode of example, using Cedrat&#39;s APA50XS amplified piezoelectric actuator can produce a stroke up to 80 microns. By using this kind of actuator, the stiffness of spring  300  and the magnitude of the total mass of the spring-mass system, including mass  306  can be recalculated with improved performance.  
         [0060]      FIG. 5  depicts an alternative embodiment incorporating an adjustment knob  500  with a female thread receiving a male thread  504  extending from support  502  holding piezoelectric actuator  301 . This configuration allows an operator to adjust the axial position of actuator  310 , spring-mass, coupling  306  and guillotine  44 . In this way the relative position of guillotine  15  with respect to sideport  14  can be regulated, modifying the maximally open dimensions of sideport  14  to accommodate to different surgical conditions.  
         [0061]      FIG. 6  depicts another alternative embodiment replacing the manual adjustment knob  500  depicted in  FIG. 5  with a miniature linear actuator  540 . Linear actuator  540  can axially displace  502  holding piezoelectric actuator  301 . This configuration allows adjustment of the axial position of actuator  310 , spring-mass, coupling  306  and guillotine  44  under controller command. In this way the relative position of guillotine  15  with respect to sideport  14  can be regulated, modifying the maximally open dimensions of sideport  14  to accommodate to different surgical conditions. Linear actuators suitable for this application are miniature actuators such as Smoovy Series 06A S2, from MicroMo Electronics, 14881 Evergreen Ave. Clearwater, Fla. 33762-3008, USA. Console controlled operation of linear actuator  540  can also allow proportional operation of surgical handpiece  10 .  
         [0062]      FIG. 7  depicts another embodiment with a spring mass-system incorporating a second spring  800  and mass  806 , with guides  802  and  804 . In this configuration both masses  306  and  806  oscillate along the same axis in mirror fashion. This structure and modality of operation is aimed to reduce handpiece  10  unwanted axial vibration during operation.  
         [0063]     Thus the reader will understand that the surgical system of the invention improves over the prior art by providing a surgical handpiece that incorporates a surgical handpiece powering method based on piezoelectric harmonic excitation of a spring-mass system. The introduction of a piezoelectric actuator driven spring-mass system for the operation of the handpiece allows high speed of operation. Complementary offset adjusting mechanism allows regulation of sideport functional dimensions. While the above description provides many specificities these should not be construed as limitations on the scope of the invention, but rather as exemplifications of preferred embodiments.  
         [0064]     For example, the illustrated piezoelectric actuator can be replaced by other architectures of piezoelectric actuators according to stroke, force and dynamic requirements for a particular system without departing from the scope of the present invention.  
         [0065]     Activation of the handpiece can be made using a footpedal, sensors in the handpiece or other suitable surgical instrument operator activation method.  
         [0066]     The controller of the handpiece can be located within the same handpiece using microelectronic circuits instead of a console located controller.  
         [0067]     The probe head can be detachable or permanently assembled to the handpiece body. Accordingly, the scope of the present invention should be determined not by the embodiments illustrated but by the appended claims and their legal equivalents.  
         [0068]     While only certain preferred features of the invention have been illustrated and described, many modifications, changes and substitutions will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.