Patent Publication Number: US-2005119790-A1

Title: Microwrist system for surgical procedures

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
      This is a continuation patent application which claims priority from U.S. patent application Ser. No. 10/013,067 filed on Dec. 7, 2001, the full disclosure of which is incorporated herein by reference. 
    
    
     STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
      NOT APPLICABLE  
     REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON A COMPACT DISK  
      NOT APPLICABLE  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a handle assembly for a medical robotic system.  
      2. Background Information  
      Historically, surgery has been performed by making large incisions in a patient to provide access to the surgical site. There has been developed instruments that allow a surgeon to perform a procedure through small incisions in the patient. The instruments include an endoscope which has a camera that allows the surgeon to view the internal organs of the patient through a small incision. Such procedures are less traumatic to the patient and have shorter recovery times than conventional surgical procedures. Endoscopic instruments have even been used to perform minimally invasive heart surgery. Blockage of a coronary artery may deprive the heart of blood and oxygen required to sustain life. The blockage may be removed with medication or by an angioplasty. For severe blockage, a coronary artery bypass graft (CABG) is performed to bypass the blocked area of the artery. CABG procedures are typically performed by splitting the sternum and pulling open the chest cavity to provide access to the heart. An incision is made in the artery adjacent to the blocked area. The internal mammary artery is then severed and attached to the artery at the point of incision. The internal mammary artery bypasses the blocked area of the artery to again provide a full flow of blood to the heart. Splitting the sternum and opening the chest cavity can create a tremendous trauma to the patient.  
      C OMPUTER  M OTION  of Goleta, Calif. provides a system under the trademark ZEUS® that allows a surgeon to perform a minimally invasive surgery, including CABG procedures. The procedure is performed with instruments that are inserted through small incisions in the patient&#39;s chest. The instruments are controlled by robotic arms. Movement of the robotic arms and actuation of instrument end effectors are controlled by the surgeon through a pair of handles and a foot pedal that are coupled to an electronic controller. Alternatively, the surgeon can control the movement of an endoscope used to view the internal organs of the patient through voice commands. Additionally, the cracked sternum prolongs the recovery period of the patient.  
      The incisions create pivot points for the medical instruments. The pivot points constrain movement of the instruments within the patient to four degrees of freedom; translation, pan, tilt and rotation of the instrument shaft. Additionally, the pivot point may cause a reverse movement of the instrument. For example, leftward movement of the system input handle may actually cause a rightward movement of the instrument. The surgeon must compensate for such constraints, thereby increasing the difficulty of using the system for performing a medical procedure.  
      It would be desirable to provide a robotic handle that gives the user the sensation of controlling the tip of the instrument. It would also be desirable to generally improve the ergonomics of medical robotic master handles.  
      There have been developed medical robotic systems that create six degrees of freedom for the surgical instruments. Six degrees of freedom requires relatively complex mechanism that increases the size and cost of the system. It would be desirable to provide an effective medical robotic system that would only require five degrees of freedom.  
     BRIEF SUMMARY OF THE INVENTION  
      A master robotic handle assembly that has only five degrees of freedom. The master handle assembly is used to move a robotically controlled surgical instrument. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a top view of an illustration of a robotic system;  
       FIG. 2  is a perspective view of a surgeon control area of the robotic system;  
       FIG. 3  is a perspective view of a handle assembly of the robotic system used to control a medical instrument;  
       FIG. 4  is an enlarged perspective view of a wrist assembly of the robotic system controlled by a user&#39;s hand;  
       FIG. 5  is a sectional perspective view of the handle/wrist assembly. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Disclosed is a medical robotic system with a handle assembly that is used to control a medical instrument. The handle assembly and medical instrument have five degrees of freedom. Five degrees of freedom may provide greater dexterity than medical robotic systems of the prior art with four or less degrees of freedom. Five degrees of freedom reduces the size and complexity of the instrument and the overall robotic system.  
      Referring to the drawings more particularly by reference numbers,  FIG. 1  shows a robotic system  10 . The system  10  may include a plurality of robotic arms  12  located adjacent to a table  14 . Two of the robotic arms  12  may control the movement of corresponding medical instruments (not shown). The third robotic arm  12  may control the movement of an endoscope (not shown). The robotically controlled instruments and endoscope may be used to perform a minimally invasive medical procedure on a patient lying on the table  14 .  
      The robotic arms  12  and accompanying instruments may be the same or similar to robotic products sold by Computer Motion under the trademarks AESOP® and ZEUS®. Although three robotic arms  12  are shown and described, it is to be understood that the system  10  may have a different number of arms  12 .  
      The robotic arms  12  are controlled from a “surgeon” area  16 . The surgeon area  16  may be located adjacent to the table  14 . Alternatively, the surgeon area  16  may be coupled to the robotic arms  12  through a telecommunications link to allow a surgeon to have remote input into the system  10 .  
       FIG. 2  shows a surgeon area  16 . The surgeon area  16  includes a pair of handle assemblies  18  located adjacent to a surgeon&#39;s chair  20 . The handle&#39; assemblies  18  are coupled to a controller  22  that is also coupled to the robotic arms  12  and medical instruments. The controller  22  may include one or more microprocessors, memory devices, drivers, etc. that convert input information from the handle assemblies  18  into output control signals which move the robotic arms and/or actuate the medical instruments.  
      The surgeon&#39;s chair  20  and handle assemblies  18  may be in front of a video console  24 . The video console  24  may be linked to the endoscope to provide video images of the patient. The surgeon&#39;s area  16  may also include a computer screen  26  coupled to the controller  22 . The screen  26  may display graphical user interfaces (GUIs) that allow the surgeon to control various functions and parameters of the system  10 .  
      Each handle assembly  18  may include a handle/wrist assembly  30 . The handle/wrist assembly  30  has a handle  32  that is coupled to a wrist  34 . The wrist  34  is connected to a forearm linkage  36  that slides along a slide bar  38 . The slide bar  38  is pivotally connected to an elbow joint  40 . The elbow joint  40  is pivotally connected to a shoulder joint  42  that is attached to the controller  22 .  
       FIG. 3  shows a handle assembly  18  superimposed with a medical instrument  50 . The instrument  50  includes an end effector  52  attached to an instrument shaft  54 . The shaft  54  extends through a cannula  56  inserted through an incision of a patient  58 . The incision defines a pivot point P for the medical instrument  50 .  
      The shoulder joint  42  includes a sensor (not shown) that provides feedback on the movement of the handle about a shoulder axis  60 . The sensor may be a mechanical encoder, optical encoder, etc. or other device which provides an output signal that corresponds to a position of the handle  32  about the shoulder axis  60 . The output of the shoulder sensor is provided to the controller  22 . The controller  22  performs a series of computations to determine a corresponding movement of the medical instrument  50 . The computations may include one or more transformation and kinematic equations. The controller  22  provides output signals to the corresponding robotic arm  12  to move the instrument  50  about point P as indicated by the arrow  62 .  
      The elbow joint  40  includes a sensor (not shown) that provides positional feedback on the position of the assembly about an elbow axis  64 . The controller  22  utilizes the positional feedback to drive the robotic arm and move the instrument in the direction indicated by the arrow  66 .  
      The forearm linkage  36  and slide bar  38  create a translator  68  that allows linear movement of the linkage  36  along a translator axis  70 . The translator axis  70  intersects with the axes  60  and  64 . The translator  68  has a sensor (not shown) that provides feedback information that is used to drive the robotic arm and move the instrument  50  in the direction indicated by the arrows  72 .  
      When transforming movement of the handle  32  to movement of the instrument  50  the controller  22  may equate the intersection of the axes  60 ,  64  and  70  to the instrument pivot point P. Equating the intersection of the axis  60 ,  64  and  70  with the pivot point P provides a kinematic relationship such that the surgeon “feel” like they are actually moving the instrument  50 . Additionally, the length of the forearm linkage and location of the handle are such that the surgeon is provided with the sensation that they are holding and moving the distal end of the instrument. These relationships also improve the ergonomics of the handle assembly and the ease of use of the robotic system as a whole. The transformation and kinematic equations may be similar to the equations used in the AESOP® and ZEUS® products with the signs (+/−) reversed to account for the elbow axis  64  being behind the surgeon.  
      The handle assembly  18  has only five degrees of freedom; handle spin, wrist, translator, elbow and shoulder. Having only five degrees of freedom reduces the complexity of the system  10 . The medical instrument  50  thus only needs a wrist with one degree of freedom which reduces the complexity, size and corresponding cost of the instrument. The configuration of the handle assembly allows the surgeon to perform any movement of the instrument with only five degrees of freedom.  
       FIGS. 4 and 5  show the wrist/handle assembly  30 . The wrist  34  includes a joint shaft  74  that is coupled to the forearm linkage  36  by a roll bearing  76 . The roll bearing  76  allows the handle  32  to rotate about a roll axis  78 . The roll axis  32  may further include a sensor  80  that provide positional feedback to the controller  22 . Movement of the handle  32  about the roll axis  78  may cause a corresponding rotation of the instrument end effector  52  in the direction indicated by the arrows  110  in  FIG. 3 .  
      The handle  32  includes a grasper  84  that is coupled to a handle housing  86 . The housing  86  and grasper  84  are preferably shaped as an ellipsoid that allows the user to more easily grasps the handle  32  with their hand. The housing  86  may have a thumb groove  88  that receives the user&#39;s thumb. The grasper  84  may have a pair of grooves  90  and  92  to receive the index and middle fingers of the user respectively.  
      The handle  32  can rotate about a wrist axis  94 . The wrist  32  provides a fifth degree of freedom not found in medical robotic systems of the prior art. The wrist  32  may include a sensor  104  that provides positional feedback for the controller  22 . To improve the ergonomics of the wrist/handle assembly  30  the wrist axis  94  preferably intersects the roll axis  78  at a centroid  96  located between the thumb  98 , index finger  100  and middle finger  102  of the user&#39;s hand. It has been found that such a configuration creates a more ergonomically correct feel of the handle  32  and movement of the handle assembly  30 .  
      The sensors  104  provide positional feedback information to the controller  22  which is used to spin the medical instrument  50  as indicated by the arrows  82  in  FIG. 3 .  
      The grasper  84  can be depressed by user. The grasper  84  is coupled to a sensor  112  which provides feedback information to the controller  22 . The feedback information is used by the controller  22  to actuate the end effector  52  shown in  FIG. 3 . By way of example, depressing the grasper  84  may close the end effector  52 . The grasper  84  may include a switch  114  that allows the user to lock the position of the grasper  84  and the end effector  52  of the corresponding medical instrument. The locking switch  114  may be coupled to a ratchet (not shown) that allows the grasper  84  and corresponding end effector  52  to be locked at a number of different positions.  
      The handle  32  may have a plurality of buttons  116 ,  118  and  120  that can be depressed by the user. By way of example, button  116  may be used to activate a cutting mode on a cauterizing end effector. Button  118  may be used to activate a coagulating medical instrument. The button  120  may be used to used to vary different functions of the system.  
      While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.