Abstract:
A microsurgical system capable of hydraulic actuation of microsurgical instruments. Such a system will provide greater force/mass and force/volume ratios, allow for better open loop control, and provide force to overcome tissue resistance.

Description:
[0001]    This application claims the priority of U.S. Provisional Application No. 60/952,426 filed Jul. 27, 2007. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention generally pertains to microsurgical systems. More particularly, but not by way of limitation, the present invention pertains to a microsurgical system capable of providing hydraulic actuation to microsurgical instruments. 
       DESCRIPTION OF THE RELATED ART 
       [0003]    Many microsurgical procedures require precision cutting and/or removal of various body tissues. For example, certain ophthalmic surgical procedures require the cutting and/or removal of the vitreous humor, a transparent jelly-like material that fills the posterior segment of the eye. The vitreous humor, or vitreous, is composed of numerous microscopic fibers that are often attached to the retina. Therefore, cutting and removal of the vitreous must be done with great care to avoid traction on the retina, the separation of the retina from the choroid, a retinal tear, or, in the worst case, cutting and removal of the retina itself. 
         [0004]    The use of microsurgical cutting instruments (i.e. vitrectomy probes, powered scissors, or powered forceps) in posterior segment ophthalmic surgery is well known. Such instruments are actuated with pneumatic pressure or electric motors and are typically inserted via an incision in the sclera near the pars plana. The surgeon may also insert other microsurgical instruments such as a fiber optic illuminator, an infusion cannula, or an aspiration probe during the posterior segment surgery. The surgeon performs the procedure while viewing the eye under a microscope. 
         [0005]    In such conventional microsurgical instruments, the use of compressible gasses results in a loss of mechanical actuation force. This reduces the precision of open loop control, and causes difficulty overcoming static or tissue resistance. 
         [0006]    Therefore, a need exists for improved devices for actuating microsurgical instruments. Such devices would demonstrate more precise open loop control, as well as force to mass and force to volume ratios that far exceed the mechanical capabilities of pneumatic or electrically actuated devices. 
       SUMMARY OF THE INVENTION 
       [0007]    In a preferred embodiment, the present invention comprises a microsurgical system capable of providing hydraulic actuation of a microsurgical instrument. The microsurgical system has a microsurgical instrument having an internal hydraulic actuator, a computer, a storage reservoir containing a non-compressible hydraulic fluid, a tube fluidly coupling the reservoir and the actuator of the instrument, and a solenoid valve located along the tube. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    For a more complete understanding of the present invention, and for further objects and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings, in which: 
           [0009]      FIG. 1  is a schematic view of a microsurgical system of the present invention. 
           [0010]      FIG. 2  is an enlarged cross sectional view of a surgical instrument of the microsurgical system of the present invention. 
           [0011]      FIG. 3  is a schematic view of a proportional controller of the microsurgical system of the present invention. 
           [0012]      FIG. 4  is a schematic view of a second embodiment of a microsurgical system of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0013]    The preferred embodiments of the present invention and their advantages are best understood by referring to  FIGS. 1-4  of the drawings, like numerals being used for like and corresponding parts of the various drawings. 
         [0014]      FIG. 1  illustrates that microsurgical system  10  comprises microsurgical instrument  12 , computer or microprocessor  14 , surgical console  16 , proportional solenoid valve  18 , and user controller  34 . Microsurgical instrument  12  is fluidly coupled to valve  18  via tube  22 , and is electrically coupled to computer  14  via interface  28 . Microsurgical instrument  12  may be any microsurgical instrument having mechanically driven components such as a vitreous cutter, powered proportional scissors, or powered proportional forceps, but is most preferably powered proportional scissors. As best shown in  FIG. 2 , microsurgical instrument  12  has hydraulic actuator  40  disposed therein. Hydraulic actuator  40  may be any mechanism appropriate for transmitting mechanical force such as a diaphragm, bellows, piston, or bourdon actuator, but is most preferably a diaphragm or bellows. Actuator  40  is mechanically coupled, at the distal end, to a movable cutting or gripping member (not shown), and is disposed within cylinder  42  which is fluidly coupled, at its proximal end, to tube  22  via port  21 . Spring  44  applies a restoring force on actuator  40 . 
         [0015]    Computer  14  is preferably integrated within surgical console  16 , but may alternatively be a stand alone unit. Surgical console  16  has fluid reservoir  30  disposed therein. Reservoir  30  contains hydraulic fluid  32 , and is fluidly coupled to valve  18  via tube  20 . Fluid  32  is preferably a non-compressible hydraulic fluid such as BSS® irrigating solution available from Alcon Laboratories, Inc. of Fort Worth, Tex.; saline solution; or deionized water, and is most preferably sterile saline solution. Fluid  32  may be added to reservoir  30  at the time of equipment manufacture, but is most preferably added by operating room personnel before a surgical procedure via port  33 . Reservoir  30  is also fluidly coupled to source of pressure  60 . Pressure transducer  36  is fluidly coupled to tube  20  between reservoir  30  and valve  18 . Pressure transducer  36  is electrically coupled to computer  14  via interface  24 . 
         [0016]    Valve  18  is most preferably a proportional solenoid-actuated valve. Valve  18  is electrically coupled to computer  14  via interface  26 . Valve  18  is most preferably a bias-closed type valve, such that when no electrical current is applied, valve  18  is closed. Conversely, when current is applied, valve  18  opens. 
         [0017]    System  10  also includes proportional controller  34 . Proportional controller  34  is preferably a foot-pedal type controller, but may be any type of proportional controller appropriate for microsurgery. As best shown in  FIG. 3 , proportional controller  34  preferably also includes a force feedback motor  50  and an encoder  56 . Motor  50  is mechanically coupled to shaft  66  via a conventional gear assembly (not shown). Motor  50  is driven by a signal generated by system  10 . Encoder  56  is preferably an optical encoder. Encoder  56  monitors the number of rotations of the shaft of motor  50 . Encoder  56  includes position detect logic  57  capable of transforming the number of rotations of shaft of motor  50  into the rotational displacement of pivotable treadle  54 . One or more return springs  58  are also coupled to shaft  66 . Springs  66  and motor  50  combine to provide a torque or force that resists actuation of treadle  54  by a surgeon&#39;s foot. Proportional controller  34  is electrically coupled to computer  14  via interface  38 . 
         [0018]    During operation, fluid  32 , if necessary, is added to reservoir  30  via port  33 , and all compressible gas is purged allowing fluid  32  to completely fill tubes  20  and  22  as well as cylinder  42 . Reservoir  30  is then pressurized to a predetermined amount. Pressure transducer  36  reads the pressure in tube  20  and transmits this information to computer  14  via interface  24 . When the surgeon actuates controller  34  with his or her foot, an electrical signal with a magnitude proportional to the position of treadle  54  is transmitted to computer  14  via interface  38 . Computer  14  then supplies a proportional electrical signal to valve  18  via interface  26 . This causes valve  18  to begin to open. Because of the proportional nature of system  10 , if the surgeon presses treadle  54  closer to the base of controller  34 , valve  18  opens further. As valve  18  is opened, pressure is transmitted through tube  22  to cylinder  42 . The pressure then acts on actuator  40  causing it to move and actuate the cutting or gripping member of instrument  12 . Position of the cutting or gripping member of instrument  12  is transmitted to computer  14  via interface  28  using a conventional position sensor disposed in instrument  12 . 
         [0019]    Motor  50  functions to provide resistance to treadle  54  of controller  34 . If greater force is needed to move the cutting or gripping member of instrument  12  through its complete cycle, such as when attempting to move scissors through thicker or more resistive tissue, computer  14  detects that the cutting or gripping member of instrument  12  has not moved through the complete cycle and signals motor  50  via interface  52  to provide increased resistance to treadle  54 . This results in controller  34  having a stiffer feeling to the surgeon when instrument  12  is working in more resistive tissue, thereby allowing system  10  the capability of providing tactile feedback to the surgeon regarding the amount of pressure required to fully actuate instrument  12 . Such tactile feedback is not possible with an instrument  12  which is pneumatically actuated due to the compressing of the working gas. 
         [0020]    In a second embodiment, best illustrated in  FIG. 4 , instrument  112  is a vitreous cutter of similar construction to surgical instrument  12 . Valve  118  is a simple on/off solenoid valve which is biased in the closed position. During operation, when the surgeon actuates controller  34 , an electrical signal is again sent to computer via interface  38 . Computer  14  then sends an alternating electrical signal to valve  18  via interface  26 , proportional in frequency to the position of treadle  54  of controller  34 . The alternating signal causes valve  118  to open and close in rapid succession delivering rapid pulses of pressure to instrument  112 . In this embodiment, when control surface  54  is depressed further, the open/close rate of valve  118  is increased, and the cycle rate of instrument  112  increases. 
         [0021]    The present invention is illustrated herein by example, and various modifications may be made by a person of ordinary skill in the art. For example, although the microsurgical instruments of the present invention have been described above as having a spring to deliver a restoring force to the actuator, the microsurgical instrument can also be operated with a dual hydraulic drive mechanism having a second tube fluidly coupling reservoir  30  with an opposing side of actuator  40 , and a second solenoid valve fluidly coupled to the second tube between reservoir  30  and actuator  40  and electrically coupled to computer  14 . In this system, pressure is transmitted to alternating sides of actuator  40 , resulting in reciprocal motion. As another example, hydraulic actuator  40  may comprise a linear electric actuator that drives a master diaphragm, bellows, piston, or bourdon actuator disposed in surgical console  16  that is fluidly coupled to slave diaphragm, bellows, piston, or bourdon actuator disposed in instrument  12 . 
         [0022]    It is believed that the operation and construction of the present invention will be apparent from the foregoing description. While the apparatus and methods shown or described above have been characterized as being preferred, various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined in the following claims.