Patent Publication Number: US-10758225-B2

Title: System and method for calibrating a surgical instrument

Description:
CLAIM OF PRIORITY 
     This application is a continuation application of U.S. patent application Ser. No. 12/862,054, filed on Aug. 24, 2010, which is a continuation application of U.S. patent application Ser. No. 10/309,532, filed on Dec. 4, 2002, now U.S. Pat. No. 7,803,151, which claims the benefit of and priority to U.S. Patent Application Ser. No. 60/337,544, filed on Dec. 4, 2001, the entire disclosures of all of which are incorporated by reference herein. 
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application incorporates by reference in its entirety U.S. application Ser. No. 09/723,715, filed on Nov. 28, 2000, now U.S. Pat. No. 6,793,652, U.S. application Ser. No. 09/836,781, filed on Apr. 17, 2001, now U.S. Pat. No. 6,981,941, U.S. application Ser. No. 09/887,789, filed on Jun. 22, 2001, now U.S. Pat. No. 7,032,798, U.S. application Ser. No. 09/324,451, filed on Jun. 2, 1999, which issued as U.S. Pat. No. 6,315,184 on Nov. 13, 2002, U.S. application Ser. No. 09/324,452, filed on Jun. 2, 1999, which issued as U.S. Pat. No. 6,443,973 on Sep. 3, 2002, U.S. application Ser. No. 09/351,534, filed on Jul. 12, 1999, which issued as U.S. Pat. No. 6,264,087 on Jul. 24, 2001, U.S. application Ser. No. 09/510,923, filed on Feb. 22, 2000, now U.S. Pat. No. 6,517,565, U.S. application Ser. No. 09/510,927, filed on Feb. 22, 2000, now U.S. Pat. No. 6,716,233, U.S. application Ser. No. 09/510,932, filed on Feb. 22, 2000, now U.S. Pat. No. 6,491,201, U.S. application Ser. No. 09/510,926, filed on Feb. 22, 2000, now U.S. Pat. No. 6,348,061, U.S. application Ser. No. 09/510,931, filed on Feb. 22, 2000, now U.S. Pat. No. 6,533,157, U.S. application Ser. No. 09/510,933, filed on Feb. 22, 2000, now U.S. Pat. No. 6,488,197, U.S. application Ser. No. 09/999,6342, 10/099,634 filed on Mar. 15, 2002, now U.S. Pat. No. 7,951,071, and U.S. application Ser. No. 09/836,781, filed on Apr. 17, 2001, now U.S. Pat. No. 6,981,941. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a system and method for calibrating a surgical instrument. More particularly, the present invention relates to a system and method for calibrating the movement of components of a surgical instrument. 
     BACKGROUND OF THE INVENTION 
     Surgeons utilize various surgical instruments for performing surgical procedures. One surgical instrument commonly used is a surgical linear clamping and stapling instrument. Such a stapler is typically used for joining and repairing tissue. Another type of surgical instrument is a circular stapler, used to perform a circular anastomosis. These staplers, and many other types of surgical instruments, usually includes components that move relative to each other. For instance, a stapler may have a body portion that stores staples and an anvil. 
     During a stapling procedure, the anvil is caused to move toward the body portion in order to clamp a section of tissue. When the section of tissue is adequately clamped between the body portion and the anvil, staples stored in the body portion are driven into the tissue and closed against the anvil. In order to ensure that the section of tissue is adequately clamped, and to ensure that the staples are properly closed, the relative positions of the components of the stapler, e.g., the body portion and the anvil, should to be known by the user of the stapler device. 
     U.S. patent application Ser. No. 09/723,715 filed on Nov. 28, 2000, which is incorporated in its entirety herein by reference, describes an electro-mechanical surgical system which includes a motor system, a control system and a remote control unit. A surgical instrument (e.g., a surgical attachment such as a surgical stapler) connects either fixedly or detachably to a distal end of a flexible shaft. A proximal end of the flexible shaft connects to a housing which encloses the motor system. Rotatable drive shafts are disposed with the flexible shaft and are rotated by the motor system. The remote control unit enables a user to control the motor system in accordance with software corresponding to the surgical instrument connected to the flexible shaft. 
     Surgical instruments, such as surgical staplers, may incorporate various control mechanisms, see, U.S. Pat. No. 5,915,616 to Viola et al. and U.S. Pat. No. 5,609,285 to Grant et al., to ensure the proper positioning and firing of the circular surgical stapler. Other conventional control and sensing mechanisms for use with surgical instruments include lasers, proximity sensors and endoscopes, see, U.S. Pat. No. 5,518,164 to Hooven and U.S. Pat. No. 5,573,543 to Akopov et al. Additional control features described may assist the surgeon in ensuring that the firing of the staples corresponds to the approach of the anvil toward the body portion. A number of conventional circular surgical staplers attached to a shaft are manipulated and actuated using hand held controls, see, U.S. Pat. No. 4,705,038 to Sjostrem; U.S. Pat. No. 4,995,877 to Ams et al., U.S. Pat. No. 5,249,583 to Mallaby, U.S. Pat. No. 5,383,880 to Hooven, and U.S. Pat. No. 5,395,033 to Byrne et al. 
     When a surgical instrument, e.g., a surgical stapler, is connected to a drive shaft of a surgical system such as described above, it may be important that the components of the surgical instrument, e.g., the anvil, anvil stem and body portion, are properly calibrated in order to ensure proper functioning in conjunction with the control system. If the components are not properly calibrated, errors may occur in the operation of the surgical instrument and consequently the control system may lose its effectiveness. Furthermore, a variety of different types of surgical instruments may be used with the electro-mechanical device described above. 
     Thus, there is a need to provide a calibration system and method that provides improved effectiveness in calibrating the components of a surgical instrument. 
     It is therefore an object of the present invention to provide a calibration system and method that provides improved effectiveness in calibrating the components of a surgical instrument. 
     It is another object of the present invention to provide a calibration system and method that enables different types of surgical instruments attached to an electro-mechanical surgical system to be calibrated. 
     SUMMARY OF THE INVENTION 
     According to one example embodiment of the present invention, a calibration system for a surgical instrument is provided. The calibration system may include an actuator, such as a motor system and flexible shaft. The calibration system may also include a surgical instrument having a first component actuatable by the actuator and a second component, the first component disposed in a first position relative to the second component. The calibration system may also include a sensor configured to provide a signal corresponding to a movement of the actuator, and calibration data corresponding to the surgical instrument. In addition, the calibration system includes a processor configured to process the calibration data and the signal from the sensor for determining, upon actuation of the actuator, a second position of the first component relative to the second component. 
     In one example embodiment of the present invention, the sensor is a Hall-effect sensor and the processor is configured to determine the second position of the first component relative to the second component in accordance with a number of rotations of the rotatable drive shaft. The calibration data may include data corresponding to a relative distance between the first component and the second component in the first position, e.g., the distance between the two components when the surgical instrument is in the fully-open or fully-closed position. In addition, the calibration data may include data correlating the movement of the actuator to a change in the relative position of the first component to the second component, e.g., correlating the number of number of rotations of a rotatable drive shaft to a change in the distance between the components of the surgical instrument. The calibration data may also include a correction factor stored in the memory unit of the surgical instrument, such that the processor is configured to determine the second position of the first component relative to the second component in accordance with the correction factor. The correction factor may correspond to a difference between an actual amount of actuation, e.g., an actual number of rotations of a drive shaft, and an expected amount of actuation, e.g., an expected number of rotations of the drive shaft, required to actuate the first component from the first position to the second position relative to the second component. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an electro-mechanical surgical system, according to one example embodiment of the present invention; 
         FIG. 2  is a diagram that shows schematically an electro-mechanical surgical system, in accordance with one embodiment of the present invention; 
         FIG. 3( a )  is a diagram that illustrates schematically a memory unit in a surgical instrument, in accordance with one embodiment of the present invention; 
         FIG. 3( b )  is a diagram that illustrates schematically a memory unit in a remote power console, in accordance with one embodiment of the present invention; 
         FIG. 4  is a schematic view of an encoder, which includes a Hall-effect device, in accordance with one embodiment of the present invention; 
         FIG. 5  is a flowchart that illustrates a method for calibrating a surgical instrument, in accordance with one example embodiment of the present invention; 
         FIG. 6  is a flowchart that illustrates a method for calibrating a surgical instrument, in accordance with another example embodiment of the present invention; 
         FIG. 7  is a flowchart that illustrates a method for calibrating a surgical instrument using a correction factor, in accordance with one embodiment of the present invention; and 
         FIG. 8  is a diagram that illustrates schematically an esophageal expander surgical instrument having a strain gauge, in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a perspective view of an electro-mechanical surgical system  10 , according to one example embodiment of the present invention. The electro-mechanical surgical system  10  may include, for example, a remote power console  12 , which includes a housing  14  having a front panel  15 . Mounted on the front panel  15  are a display device  16  and indicators  18   a ,  18   b . A flexible shaft  20  may extend from the housing  14  and may be detachably secured thereto via a first coupling  22 . The distal end  24  of the flexible shaft  20  may include a second coupling  26  adapted to detachably secure a surgical instrument  100 , e.g., a surgical attachment, to the distal end  24  of flexible shaft  20 . Alternatively, the distal end  24  of the flexible shaft  20  may be adapted to fixedly secure the surgical instrument  100  to the distal end  24  of flexible shaft  20 . The surgical instrument  100  may be, for example, a surgical stapler, a surgical cutter, a surgical stapler-cutter, a linear surgical stapler, a linear surgical stapler-cutter, a circular surgical stapler, a circular surgical stapler-cutter, a surgical clip applier, a surgical clip ligator, a surgical clamping device, a vessel expanding device, a lumen expanding device, a scalpel, a fluid delivery device or any other type of surgical instrument. 
     Such surgical instruments are described, for example, in U.S. Pat. No. 6,315,184, entitled “A Stapling Device for Use with an Electromechanical Driver Device for Use with Anastomosing, Stapling, and Resecting Instruments,” U.S. Pat. No. 6,443,973, entitled “Electromechanical Driver Device for Use with Anastomosing, Stapling, and Resecting Instruments,” U.S. Pat. No. 6,264,087, entitled “Automated Surgical Stapling System,” U.S. patent application Ser. No. 09/510,926, entitled “A Vessel and Lumen Expander Attachment for Use with an Electromechanical Driver Device,” U.S. patent application Ser. No. 09/510,927, entitled “Electromechanical Driver and Remote Surgical Instruments Attachment Having Computer Assisted Control Capabilities,” U.S. patent application Ser. No. 09/510,931, entitled “A Tissue Stapling Attachment for Use with an Electromechanical Driver Device,” U.S. patent application Ser. No. 09/510,932, entitled “A Fluid Delivery Mechanism for Use with Anastomosing, Stapling, and Resecting Instruments,” and U.S. patent application Ser. No. 09/510,933, entitled “A Fluid Delivery Device for Use with Anastomosing, Stapling, and Resecting Instruments,” each of which is expressly incorporated herein in its entirety by reference thereto. 
     The remote power console  12  also includes a motor  1010  for driving the surgical instrument  100 . The surgical instrument may include an end effector. The end effector may be connected to a handheld electromechanical driver assembly. In one example embodiment, the driver assembly has a first drive component and a second drive component. The first drive component may actuate a first flexible drive shaft and the second drive component may actuate a second flexible drive shaft. In one another example embodiment, the motor  1010  couples to the surgical instrument  100  via a rotatable drive shaft  630  within the flexible shaft  20 . As the drive shaft  630  rotates, a first component  100   a  of the surgical instrument  100  moves relative to a second component  100   b  of the surgical instrument  100 . For instance, depending on the type of surgical instrument that is used, actuation via the rotatable drive shaft  630  of the first component  100   a  relative to the second component  100   b  may, for example, include opening or closing a clamp, moving a cutting edge and/or firing staples or any other type of movement. Examples of such a remote power console  12  is described in U.S. patent application Ser. No. 09/723,715, now U.S. Pat. No. 6,793,652, entitled “Electro-Mechanical Surgical Device,” and U.S. patent application Ser. No. 09/836,781, now U.S. Pat. No. 6,981,941, entitled “Electro-Mechanical Surgical Device,” each of which is expressly incorporated herein by reference in its entirety. The power console  12  may also include a processor  1020 . 
       FIG. 2  is a diagram that shows schematically the electro-mechanical surgical system  10 , in accordance with one embodiment of the present invention. The processor  1020  may be disposed in the remote power console  12 , and is configured to control various functions and operations of the electro-mechanical surgical system  10 . A memory unit  130  is provided and may include memory devices, such as, a ROM component  132  and/or a RAM component  134  for storing programs or algorithms employed by the processor  1020 . The ROM component  132  is in electrical and logical communication with processor  1020  via line  136 , and the RAM component  134  is in electrical and logical communication with processor  1020  via line  138 . The RAM component  134  may include any type of random-access memory, such as, for example, a magnetic memory device, an optical memory device, a magneto-optical memory device, an electronic memory device, etc. Similarly, the ROM component  132  may include any type of read-only memory, such as, for example, a removable memory device, such as a PC-Card or PCMCIA-type device. It should be appreciated that the ROM component  132  and the RAM component  134  may be embodied as a single unit or may be separate units and that the ROM component  132  and/or the RAM component  134  may be provided in the form of a PC-Card or PCMCIA-type device. 
     The processor  1020  is further connected to the display device  16  via a line  154  and to the indicators  18   a ,  18   b  via respective lines  156 ,  158 . The line  124  electrically and logically connects the processor  1020  to the motor  1010 . The motor  1010  is coupled via the rotatable drive shaft  630  to the surgical instrument  100 . A sensor  1030 , which may include an encoder  1106 , is electrically and logically connected to processor  1020  via line  152 . The sensor  1030  may be disposed in the second coupling  26  of the flexible shaft  20  and may be configured to provide a signal corresponding to a movement of the drive shaft  630  via line  152  to the processor  1020 . The surgical instrument  100  may include a memory unit  1741 , an example of which is illustrated schematically in  FIG. 3( a )  and described in greater detail below, which is electrically and logically connected to the processor  1020  by a line  1749 . The processor  1020  may also include an additional memory unit  1742 , an example of which is illustrated schematically in  FIG. 3( b )  and described in greater detail below, which may be disposed within the remote power console  12  and which is electrically and logically connected to the processor  1020  by a line  278 . 
     As mentioned above, according to one embodiment of the present invention, the surgical instrument  100  may include a memory unit, such as memory unit  1741  illustrated schematically in  FIG. 3( a ) . The memory unit  1741  may store information as described, for example, in U.S. patent application Ser. No. 09/723,715, filed on Nov. 28, 2000, U.S. patent application Ser. No. 09/836,781, filed on Apr. 17, 2001, U.S. patent application Ser. No. 09/887,789, filed on Jun. 22, 2001, and U.S. patent application Ser. No. 10/099,634, filed on Mar. 15, 2002 each of which is expressly incorporated herein by reference in its entirety. For instance, as illustrated in  FIG. 3( a ) , the memory unit  1741  may include a data connector  2721  that includes contacts  2761 , each electrically and logically connected to memory unit  1741  via a respective line  1749 . The memory unit  1741  may be configured to store, for example, serial number data  1801 , attachment type identifier data  1821  and calibration data  1841 . The memory unit  1741  may additionally store other data. Both the serial number data  1801  and the attachment type identifier data  1821  may be configured as read-only data. In the example embodiment, serial number data  1801  is data uniquely identifying the particular surgical instrument  100 , whereas the attachment type identifier data  1821  is data identifying the type of the surgical instrument  100 , such as, for example, a circular stapler. The calibration data  1841  may be any type of data used to calibrate the surgical instrument  100 . For instance, the calibration data  1841  may include data correlating a movement of an actuator, e.g., a number of rotations of a rotatable drive shaft  630 , to a change in the distance between the first component  100   a  and the second component  100   b  of the surgical instrument  100 . Furthermore, the calibration data  1841  may include data corresponding to a position of first and second components of the surgical instrument relative to one another, such as a distance of the first component  100   a  of the surgical instrument  100  relative to the second component  100   b  when in a particular position, e.g., a fully-open or a fully-closed position. In addition, the calibration data  184  may include a correction factor, as more fully described below, in order to account for gearing backlash or other types of mechanical variables of the particular type of surgical instrument  100 . Generally, the calibration data  184  may provide any type of data corresponding to any mechanical variable specific to the particular surgical instrument  100 . 
     As mentioned above, according to one embodiment of the present invention, the remote power console  14 , e.g., the processor  1020  may also include a memory unit, such as memory unit  1742  illustrated schematically in  FIG. 3( b ) . It should be understood that, while the memory unit  1742  is shown as being discrete, some or all of the data stored thereby may alternatively be stored in the memory unit  130 . Referring to  FIG. 3( b ) , the memory unit  1742  may include a data connector  2722  that includes contacts  2762 , each electrically and logically connected to the memory unit  1742  via a respective line  278 . The memory unit  1742  may be configured to store, for example, serial number data  1802 , attachment type identifier data  1822  and calibration data  1842  for a number of different surgical attachments. The memory unit  1742  may additionally store other data. Both the serial number data  1802  and the attachment type identifier data  1822  may be configured as read-only data. In the example embodiment, serial number data  1802  is data uniquely identifying particular surgical instruments, whereas the attachment type identifier data  1822  is data identifying various types of surgical instruments, such as, for example, a circular stapler. The calibration data  1842  may be any type of data used to calibrate a surgical instrument. For instance, the calibration data  1842  may include data correlating a movement of an actuator, e.g., a number of rotations of a rotatable drive shaft  630 , to a change in the distance between the first component  100   a  and the second component  100   b  of the surgical instrument  100 . Furthermore, the calibration data  1842  may include data corresponding to a position of first and second components of the surgical instrument relative to one another, such as a distance of the first component  100   a  of the surgical instrument  100  relative to the second component  100   b  when in a particular position, e.g., a fully-open or a fully-closed position. As stated above with respect to calibration data  1841 , the calibration data  1842  may provide any type of data corresponding to any mechanical variable specific to a surgical instrument  100 . 
     Referring to  FIG. 2 , the electro-mechanical surgical system  10  may also include the sensor  1030 . The sensor  1030  is connected to the processor  1020  via a line  152 . The sensor  1030  may provide signals related to the movement of actuators, e.g., rotation of the drive shaft  630 , within the flexible shaft  20 . In one embodiment, the sensor  1030  is positioned at the distal end  24  of the flexible shaft  20 . For instance, according to one example embodiment of the present invention, the sensor  1030  includes a first encoder  1106  provided within the second coupling  26  and configured to output a signal in response to and in accordance with the rotation of the first drive shaft  630 . The signal output by the encoder  1106  may represent the rotational position of the rotatable drive shaft  630  as well as the rotational direction thereof. The encoder  1106  may be, for example, a Hall-effect device, an optical devices, etc. Although the encoder  1106  is described as being disposed within the second coupling  26 , it should be appreciated that the encoder  1106  may be provided at any location between the motor  1010  and the surgical instrument  100 . It should be appreciated that providing the encoder  1106  within the second coupling  26  or at the distal end  24  of the flexible shaft  20  provides for an accurate determination of the drive shaft rotation. If the encoder  1106  is disposed at the proximal end of the flexible shaft  20 , windup of the rotatable drive shaft  630  may result in measurement error. 
       FIG. 4  is a schematic view of an encoder  1106 , which includes a Hall-effect device. Mounted non-rotatably on drive shaft  630  is a magnet  240  having a north pole  242  and a south pole  244 . The encoder  1106  further includes a first sensor  246  and second sensor  248 , which are disposed approximately 90° apart relative to the longitudinal, or rotational, axis of drive shaft  630 . The output of the sensors  246 ,  248  is persistent and changes its state as a function of a change of polarity of the magnetic field in the detection range of the sensor. Thus, based on the output signal from the encoder  1106 , the angular position of the drive shaft  630  may be determined within one-quarter revolution and the direction of rotation of the drive shaft  630  may be determined. The output of the encoder  1106  is transmitted via a respective line  152  to processor  1020 . The processor  1020 , by tracking the angular position and rotational direction of the drive shaft  630  based on the output signal from the encoder  1106 , can thereby determine the position and/or state of the first component  100   a  of the surgical instrument  100  relative to the second component  100   b . That is, by counting the revolutions of the drive shaft  630 , the processor  1020  can determine the position and/or state of the first component  100   a  of the surgical instrument relative to the second component  100   b.    
       FIG. 5  is a flowchart that illustrates a method for calibrating a surgical instrument  100 , in accordance with one example embodiment of the present invention. At step  200 , a user attaches the surgical instrument  100  to the distal end  24  of the flexible shaft  20 . At step  210 , the processor  1020  reads calibration data corresponding to the surgical instrument  100 . The calibration data corresponding to the surgical instrument  100  may be calibration data  1841  stored in the memory unit  1741  in the surgical instrument  100  and may be provided to the processor  1020  via line  1749  after attachment of the surgical instrument  100  to the flexible shaft  20 . Alternatively, the calibration data may be calibration data  1842  stored in the memory unit  1742  of the remote power console  12  or in any other data storage location. In another embodiment, attachment type identifier data  1821  corresponding to the surgical instrument  100  is stored in the memory unit  1741  in the surgical instrument  100 , and calibration data corresponding to more than one different type of surgical instrument may be stored as calibration data  1842  in a memory unit  1742  in the remote power console  12 —after attachment of the surgical instrument  100  to the flexible shaft  20 , the processor  1020  is configured to read the attachment type identifier data  182  of the surgical instrument  100 , to identify the type of surgical instrument that has been attached, and to select from the calibration data  1842  of the memory unit  1742  the calibration data corresponding to the particular surgical instrument being used. 
     At step  220 , the processor  1020  determines a first position of the surgical instrument  100 , e.g., a first position of the first component  100   a  of the surgical instrument  100  relative to the second component  100   b . For example, the processor  1020  may determine a distance between the first component  100   a  and the second component  100   b  in the first position. This first position may be, for example, a position employed during shipping of the surgical instrument  100 , e.g., a fully-open or a fully-closed position. In one embodiment, one or both of the calibration data  1841 ,  1842  corresponding to the surgical instrument  100  includes data corresponding to the distance between the first and second components  100   a ,  100   b  of the surgical instrument  100  when in the first position, thereby enabling the processor  1020  to determine the first position of the first component  100   a  of the surgical instrument  100  relative to the second component  100   b  by merely reading one or both of the calibration data  1841 ,  1842  corresponding to the surgical instrument  100 . 
     At step  230 , the first component  100   a  of the surgical instrument  100  is actuated so as to move relative to the second component  100   b . The actuation of the first component  100   a  at step  230  may be for the purposes of clamping a section of tissue, for driving staples, etc., depending on the type of surgical instrument being used. In one embodiment, the first component  100   a  of the surgical instrument  100  is actuated relative to the second component  100   b  by the motor  1010  rotating the rotatable drive shaft  630  in the flexible shaft  20 . At step  240 , the sensor  1030  provides a signal to the processor  1020  corresponding to the movement of the actuator. For instance, the sensor  1030  may be a Hall-effect sensor that provides a signal corresponding to, the number of rotations that has been made by the rotatable drive shaft  630 , as described more fully above. At step  250 , the processor  1020  may process the data corresponding to the first position of the first component  100   a  relative to the second component  100   b , the signal received from the sensor  1030 , and one or both of the calibration data  1841 ,  1842  corresponding to the surgical instrument  100  in order to determine a second position of the first component  100   a  of the surgical instrument  100  relative to the second component  100   b . For instance, where either of the calibration data  1841 ,  1842  includes data correlating a number of rotations of the rotatable drive shaft  630  to a change in the distance between the first component  100   a  and the second component  100   b  of the surgical instrument  100 , the processor  1020  may determine from the signal provided by the Hall-effect sensor  1030  the distance traveled by the first component  100   a  relative to the second component  100   b . Where either of the calibration data  1841 ,  1842  also includes an initial distance between the first and second components  100   a ,  100   b  in the first position, the processor  1020  may determine the difference between the initial distance between the first and second components  100   a ,  100   b  and the distance traveled by the first component  100   a  during step  230  in order to ascertain the actual distance between the first and second components  100   a ,  100   b  after the first component  100   a  has been actuated. Thus, the surgical instrument  100  may be calibrated thereby ensuring that the relative position of the first and second components  100   a ,  100   b  are known during operation of the surgical instrument  100 , and the position of the surgical instrument  100 , e.g., the position of the first component  100   a  relative to the second component  100   b , may be monitored during operation. 
       FIG. 6  is a flowchart that illustrates a method for calibrating a surgical instrument  100 , e.g., a 55 mm linear stapler/cutter surgical attachment, in accordance with another example embodiment of the present invention. At step  300 , a user attaches the surgical instrument  100  to the distal end  24  of the flexible shaft  20 . At step  310 , the processor  1020  reads calibration data corresponding to the surgical instrument  100 . As described above, the calibration data corresponding to the surgical instrument  100  may be the calibration data  1841  stored in the memory unit  1741  of the surgical instrument  100  and may be provided to the processor  1020  via line  120  upon attachment of the surgical instrument  100  to the flexible shaft  20 , or may be the calibration data  1842  stored in the memory unit  1742  of the remote power console  12  or in any other data storage location. 
     At step  320 , the first component  100   a  is either automatically or selectively actuated into a first position relative to the second component  100   b  upon the surgical instrument  100  being connected to the flexible shaft  20 . For instance, upon the surgical instrument  100  being connected to the flexible shaft  20 , the first component  100   a  may be actuated relative to the second component  100   b  into a fully-open or a fully-closed position. This fully-open or fully-closed position may be a “hard-stop” position, e.g., a position past which the first component  100   a  is mechanically unable to travel. The processor  1020  may detect when the first component  100   a  of the surgical instrument  100  reaches the first position when, for example, the drive shaft  630  is unable to further rotate, or after the expiration of a predetermined time period. 
     At step  330 , the processor  1020  determines a first position of the first component  100   a  of the surgical instrument  100  relative to the second component  100   b . For example, the processor  1020  may determine a distance between the first and second components  100   a ,  100   b  in the first position. As previously mentioned, one or both of the calibration data  1841 ,  1842  corresponding to the surgical instrument  100  may include data corresponding to the distance between the first and second components  100   a ,  100   b  of the surgical instrument  100  when in the first position, thereby enabling the processor  1020  to determine the first position of the first component  100   a  of the surgical instrument  100  relative to the second component  100   b  by merely reading one or both of the calibration data  1841 ,  1842  corresponding to the surgical instrument  100 . 
     At step  340 , the first component  100   a  of the surgical instrument  100  is again actuated so as to move relative to the second component  100   b . The actuation of the first component  100   a  at step  340  may be for the purpose of clamping a section of tissue, for firing staples, etc., depending on the type of surgical instrument being used. In one embodiment, the first component  100   a  of the surgical instrument  100  is actuated relative to the second component  100   b  by the motor  1010  rotating the rotatable drive shaft  630  of the flexible shaft  20 . 
     At step  350 , the sensor  1030  provides a signal to the processor  1020  corresponding to the movement of the actuator, e.g., a signal corresponding to the number of rotations that has been made by the rotatable drive shaft  630 , as described more fully above. At step  360 , the processor  1020  may process the data corresponding to the first position of the first component  100   a  relative to the second component  100   b , the signal received from the sensor  1030 , and one or both of the calibration data  1841 ,  1842  corresponding to the surgical instrument  100  in order to determine a second position of the first component  100   a  of the surgical instrument  100  relative to the second component  100   b . For instance, the processor  1020  may determine from the signal provided by the Hall-effect sensor  1030  the distance traveled by the first component  100   a  relative to the second component  100   b  during step  340 , and may further determine the difference between the initial distance between the first and second components  100   a ,  100   b  in the first position. Thus, the processor  1020  may also determine the distance traveled by the first component  100   a  during step  340 , in order to ascertain the actual distance between the first and second components  100   a ,  100   b  after the first component  100   a  has been actuated. 
     The method described by the flowchart of  FIG. 6  may be used even when a surgical instrument  100  is calibrated, e.g., moved to a fully open or fully closed position, prior to packaging and shipping. For instance, although a surgical instrument  100  is calibrated prior to packaging and shipping, the surgical instrument  100  may be subjected to vibration or shock prior to use, thereby causing the components of the surgical instrument to be moved from their original calibrated positions. The method of  FIG. 6  may be used to ensure that the processor  1020  may accurately determine the relative positions of the components of the surgical instrument  100  even if the components are inadvertently moved prior to their use. 
     In one embodiment of the present invention, a correction factor is used when calibrating the surgical instrument  100 . A correction factor may be any type of calibration data corresponding to a surgical instrument. For instance, a correction factor may correspond to a difference between expected calibration data of a typical surgical instrument and actual calibration data of a particular surgical instrument of that type. Such a correction factor may be employed to account for gearing backlash or any other mechanical variables that may be distinct to a particular surgical instrument. 
     For instance, a surgical instrument  100  may be packaged with a first component  100   a , e,g., an anvil, in contact with a solid mechanical buffer that defines a first, fully-open position. In the first, fully-open position of a surgical instrument  100 , the first component  100   a  may be positioned at a distance of, e.g., 16 mm, from the second component  100   b . The surgical instrument  100  may also have a second, fully-closed position in which the first component  100   a  is positioned at a distance of, e.g., 1 mm, from the second component  100   b . The memory unit  1742  of the remote power console  12  may include calibration data  1842  that correlates the expected movement of an actuator to the relative movement of the components  100   a ,  100   b . For instance, the memory unit  1742  of the remote power console  12  may include calibration data  1842  that correlates an expected number of rotations of drive shaft  630  to a change in the linear distance between the first and second components of the surgical instrument  100 . In this example, the memory unit  1742  of the remote power console  12  may include calibration data  1842  that correlates  550  rotations of drive shaft  630  to a 15 mm change in the linear distance between the first and second components  100   a ,  100   b  of the surgical instrument  100 . Thus, the calibration data  1842 , when read by the processor  1020 , may instruct the processor  1020  to rotate the rotatable drive shaft  630  a total of 550 times in order to close the jaws of the surgical instrument  100  from a first, fully-open position to a second, fully-closed position. However, the correction factor accounts for the situation in which, while  550  turns may be required to fully close the components  100   a ,  100   b  of a typical surgical instrument of this type, a particular surgical instrument may require a different number of turns of the drive shaft  630  in order to fully close the components  100   a ,  100   b.    
       FIG. 7  is a flowchart that illustrates a method for calibrating a surgical instrument  100  using a correction factor, in accordance with one embodiment of the present invention. At step  400 , a particular surgical instrument  100  is placed in a test fixture, e.g., during manufacture, and opened to a first, fully-open position. The surgical instrument  100  may be opened by the test fixture at a speed and torque equivalent to speed and torque at which the surgical instrument  100  will be driven when connected to the flexible shaft  20  of the remote power console  12 . At step  410 , the test fixture drives the surgical instrument  100  to the second, fully-closed position. However, instead of the  550  turns required to fully close the components  100   a ,  100   b  of a typical surgical instrument of this type, this particular surgical instrument  100  may require a different number of turns, e.g.,  562 , of the drive shaft  630  in order to fully close the components  100   a ,  100   b.    
     At step  420 , a correction factor equal to the difference between the expected number of turns required to fully close the components  100   a ,  100   b  in a typical surgical instrument and the actual number of turns required to fully close the components  100   a ,  100   b  in the particular surgical instrument  100  is stored as a correction factor in the calibration data  1841  in the memory unit  1741  of the surgical instrument  100 . At step  430 , the surgical instrument  100  is attached to the flexible shaft  20 . At step  440 , the processor  1020  reads the correction factor from the memory unit  1741  in the surgical instrument  100 . In addition, the processor  1020  may read the calibration data  1842  stored in the memory unit  1742  of the remote power console  12 , which may store the expected number of turns required for a typical surgical instrument of the same type as the surgical instrument  100 . 
     At step  450 , the processor  1020  determines, from the calibration data  1842  stored in the memory unit  1742  in the remote power console  12  and from the correction factor stored as calibration data  1841  in the memory unit  1741  in the surgical instrument  100 , the correct amount of actuation, e.g., the correct number of turns of the drive shaft  630 , that is required to move the first and second components  100   a ,  100   b  a desired distance relative to each other. For instance, in the above example, in order to move the first and second components  100   a ,  100   b  from the first, fully-open position to the second, fully-closed position, the processor  1020  may add the expected calibration data  1842  stored in the memory unit  1742  of the remote power console  12 , e.g., 550 turns, to the correction factor stored in the memory unit  1741  of the surgical instrument  100 , e.g., 12 turns, to determine that the correct number of turns required to move the first and second components  100   a ,  100   b  between the fully-open and fully-closed positions is 562 turns. Of course, the processor  1020  may also use the calibration data  1842  and the correction factor to determine the correct number of turns required to move the first and second components  100   a ,  100   b  any distance relative to each other. In addition, it should be understood that other types of correction factors, stored in other data storage locations, may also be employed by the system  10 . 
     At step  460 , the first component  100   a  is moved into the first, fully-open position relative to the second component  100   b , so as to prepare for operation. Alternatively, the surgical instrument  100  may be shipped having the first component  100   a  in the fully-open position relative to the second component  100   b . At step  470 , the first component  100   a  is actuated from the fully-open position to the fully-closed position, or is actuated to any desired position relative to the second component  100   b , by rotating the drive shaft  630  the number of turns determined in step  450 . 
     The above method may also be used with an esophageal expander surgical instrument that may use a strain gauge to measure esophageal compression.  FIG. 8  is a diagram that illustrates schematically an esophageal expander surgical instrument  800  having a strain gauge  202 . Mounted strain gauges may require calibration, e.g., of gain and offset. Correction factors associated with the gain and offset may be derived during the final assembly of an esophageal expander surgical instrument, and may be stored electronically in a memory device  204  contained within the esophageal expander surgical instrument  800 . The strain gauge  202  may also use a signal-conditioning amplifier  206 . The signal-conditioning amplifier  206  may be located in an adapter  208  for a flexible shaft  810  or in a power console  212 . The signal-conditioning amplifier  206  also may require calibration, e.g., of gain and offset. The signal-conditioning amplifier  206  may include a memory device  214  to store its respective correction factors. Accordingly, when an esophageal expander surgical instrument  800  is coupled to a flexible drive shaft  810 , a processor  216  in the remote power console  212  may read the stored calibration data from the memory devices  204 ,  214  in the esophageal expander surgical instrument  800  and in the signal-conditioning amplifier  206 , respectively, and use the correction factors to calibrate the esophageal expander surgical instrument  800  prior its operation. 
     Several example embodiments of the present invention are specifically illustrated and/or described herein. However, it will be appreciated that modifications and variations of the present invention are covered by the above teachings without departing from the spirit and intended scope of the present invention.