Abstract:
A robotic system for performing an arthroplasty procedure of a patient is provided. The robotic system includes a robotic mechanism including an adaptive arm, an oscillating saw coupled to the robotic mechanism and configured to resect a portion of a bone of the patient. The robotic mechanism is configured to control movement of the saw during the resection. The system also includes a computer coupled to the robotic mechanism which is configured to control the robotic mechanism. The robotic mechanism is configured to position a prosthetic implant relative to the bone. The system also includes an electric motor coupled to the robotic mechanism and the computer. The electric motor is configured to facilitate movement of the robotic mechanism. The system also includes a position sensor configured to provide movement information of the prosthetic implant relative to the bone. The system also includes an adaptive arm interface coupled to the adaptive arm and the computer wherein the adaptive arm interface is configured to operate the computer.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 15/218,608 filed Jul. 25, 2016, which is a continuation of U.S. patent application, which is a continuation of U.S. patent application Ser. No. 13/951,073 filed Jul. 25, 2013, which is a continuation of U.S. patent application Ser. No. 13/923,944 filed Jun. 21, 2013, which is a continuation of U.S. patent application Ser. No. 13/912,730, now U.S. Pat. No. 9,149,281, filed Jun. 7, 2013, which is a continuation of U.S. patent application Ser. No. 13/888,957, now U.S. Pat. No. 9,192,395, filed May 7, 2013, which is a continuation of U.S. patent application Ser. No. 10/102,413, now U.S. Pat. No. 9,155,544, filed Mar. 20, 2002, which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to the securing of body tissue. 
         [0003]    Body tissue has previously been secured utilizing sutures, staples, pegs, screws, and/or other fasteners. When one or more of these known devices is to be utilized to secure body tissue, the device may be concealed from view within a patient&#39;s body. Of course, this makes the securing of the body tissue more difficult. The manner in which a suture may be utilized to secure body tissue is disclosed in U.S. Pat. No. 6,159,234. The manner in which a staple may be utilized in association with body tissue is disclosed in U.S. Pat. No. 5,289,963. It has previously been suggested that a robotic mechanism may be utilized to assist in the performance of surgery. Various known robotic mechanisms are disclosed in U.S. Pat. Nos. 5,078,140; 5,572,999; 5,791,231; 6,063,095; 6,231,565; and 6,325,808. 
       SUMMARY 
       [0004]    The present invention relates to a method of securing either hard or soft body tissue. A robotic mechanism or manual effort may be used to position a fastener relative to the body tissue. The fastener may be a suture, staple, screw, or other known device. 
         [0005]    The fastener may be a suture which is tensioned with a predetermined force by a robotic mechanism or manual effort. The robotic mechanism or manual effort may also be used to urge a retainer toward body tissue with a predetermined force. The suture may be gripped with the retainer while the suture is tensioned with a predetermined force and while the retainer is urged toward the body tissue with a predetermined force. 
         [0006]    Alternatively, the fastener may be a staple. A robotic mechanism or manual effort may be utilized to position the staple relative to body tissue. The robotic mechanism or manual effort may effect a bending of the staple to move legs of the staple into engagement with each other. The legs of the staple may be bonded together at a location where the legs of the staple are disposed in engagement. 
         [0007]    Regardless of what type of fastener is utilized, a positioning apparatus may be used to position the body tissue before and/or during securing with a fastener. The positioning apparatus may include a long thin member which transmits force to the body tissue. Force may be transmitted from an expanded end portion of the long thin member to the body tissue. A second member may cooperate with the long thin member to grip the body tissue. The long thin member may be positioned relative to the body tissue by a robotic mechanism or manual effort. 
         [0008]    Various imaging devices may be utilized to assist in positioning a fastener, such as a rivet suture or staple, relative to body tissue. Under certain circumstances at least, it may be desirable to utilize two or more different types of imaging devices. Thus, an endoscope and a magnetic resonance imaging apparatus (MRI) may be utilized to provide an image. Alternatively, an endoscope and a fluoroscopic device may be utilized. If desired, ultrasonic imaging devices may be utilized in association with another imaging device, such as an endoscope or magnetic resonance imaging device. One or more markers may be provided on fasteners to facilitate location of the fasteners in an image. 
         [0009]    A fastener may be utilized to secure a scaffold containing viable tissue components in place on body tissue. The tissue components may be stem cells, fetal cells, mesenchymal cells, and/or any desired type of precursor cells. It is contemplated that the scaffold with one or more different types of tissue components may be positioned at any desired location within a patient&#39;s body, such as within an organ, by the robotic mechanism. For example, the scaffold could be positioned in the pancreas or liver of a patient. Alternatively, the scaffold could be connected with a bone in the patient&#39;s body. The scaffold may be positioned relative to the body tissue by the robotic mechanism or manual effort. One or more markers may be provided on the scaffold to facilitate location of the scaffold in an image. 
         [0010]    It is contemplated that the robotic mechanism may advantageously be utilized to position surgical implants other than fasteners in a patient&#39;s body. For example, the robotic mechanism may be utilized to position a prosthesis in a patient&#39;s body. If desired, the robotic mechanism may be utilized to position a screw type fastener at a specific location in a patient&#39;s body. The robotic mechanism may be used to position a scaffold containing viable tissue components relative to body tissue. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The foregoing and other features of the invention will become more apparent upon a consideration of the following description taken in connection with the accompanying drawings wherein: 
           [0012]      FIG. 1  is a schematic illustration depicting the manner in which a robotic mechanism and an imaging device are positioned relative to a patient&#39;s body; 
           [0013]      FIG. 2  is a schematic illustration depicting the manner in which the robotic mechanism of  FIG. 1  is utilized to move a suture anchor into a patient&#39;s body; 
           [0014]      FIG. 3  is a schematic illustration depicting the manner in which the robotic mechanism of  FIG. 1  is utilized to tension a suture with a predetermined force and urge a suture retainer toward body tissue with a predetermined force; 
           [0015]      FIG. 4  is a schematic illustration depicting the manner in which the robotic mechanism of  FIG. 1  is utilized to grip the suture with a suture retainer while the suture is tensioned with a predetermined force and the retainer is urged toward body tissue with a predetermined force; 
           [0016]      FIG. 5  is a schematic illustration depicting the linear apposition of body tissue with sutures, anchors and retainers which were positioned by the robotic mechanism of  FIG. 1  in the same manner as illustrated in  FIGS. 2-4 ; 
           [0017]      FIG. 6  is a schematic illustration depicting an alternative manner in which body tissue may be secured by the robotic mechanism of  FIG. 1  using an anchor, suture and retainer; 
           [0018]      FIG. 7  (on sheet  5  of the drawings) is a schematic illustration, similar to  FIG. 4 , illustrating the manner in which a pair of suture retainers are connected with a suture by the robotic mechanism of  FIG. 1  to secure body tissue; 
           [0019]      FIG. 8  is a schematic illustration, similar to  FIG. 5 , illustrating the linear apposition of body tissue with a fastener which includes a suture and plurality of suture retainers which are positioned by the robotic mechanism of  FIG. 1  in the manner illustrated in  FIG. 7 ; 
           [0020]      FIG. 9  is a schematic illustration depicting the manner in which a long thin member of a tissue positioning assembly is moved into body tissue by the robotic mechanism of  FIG. 1 ; 
           [0021]      FIG. 10  is a schematic illustration of a manner in which a leading end portion of the long thin member of  FIG. 9  is expanded by the robotic mechanism of  FIG. 1  and transmits force from the robotic mechanism to body tissue; 
           [0022]      FIG. 11  is a schematic illustration depicting the manner in which an anchor is moved along the long thin member of  FIG. 10  into body tissue by the robotic mechanism of  FIG. 1 ; 
           [0023]      FIG. 12  is a schematic illustration depicting the manner in which a gripper member is moved along the long thin member of  FIG. 10  by the robotic mechanism of  FIG. 1  to grip body tissue and an alternative manner in which a fastener is moved into the gripped body tissue by the robotic mechanism; 
           [0024]      FIG. 13  is an enlarged, fragmentary sectional view further depicting the manner in which the leading end portion of the long thin member of  FIG. 9  is expanded by the robotic mechanism of  FIG. 1 ; 
           [0025]      FIG. 14  is an enlarged, fragmentary sectional view depicting another manner in which the leading end portion of the long thin member of  FIG. 9  may be expanded by the robotic mechanism of  FIG. 1 ; 
           [0026]      FIG. 15  is an enlarged, fragmentary sectional view depicting another manner in which the leading end portion of the long thin member of  FIG. 9  may be expanded by the robotic mechanism of  FIG. 1 ; 
           [0027]      FIG. 16  is a schematic illustration depicting the manner in which a long thin member of an alternative embodiment of the tissue positioning assembly is moved into body tissue by the robotic mechanism of  FIG. 1 ; 
           [0028]      FIG. 17  is a schematic illustration depicting how a space between upper and lower body tissues of  FIG. 16  is closed by movement of the tissue positioning assembly by the robotic mechanism of  FIG. 1 ; 
           [0029]      FIG. 18  is a schematic illustration depicting the manner in which a fastener is moved into the body tissue of  FIG. 16  by the robotic mechanism of  FIG. 1  while the body tissue is positioned in the manner illustrated in  FIG. 17 ; 
           [0030]      FIG. 19  is a schematic illustration depicting the manner in which a retainer may be connected with the long thin member of the tissue positioning assembly of  FIGS. 16 and 17  by the robotic mechanism of  FIG. 1  utilizing the apparatus of  FIGS. 4 and 7 ; 
           [0031]      FIG. 20  is a schematic illustration depicting an alternative manner of utilizing the robotic mechanism of  FIG. 1  to secure body tissue with a suture and retainer; 
           [0032]      FIG. 21  is a schematic illustration depicting the manner in which a staple is positioned relative to body tissue by the robotic mechanism of  FIG. 1 ; 
           [0033]      FIG. 22  is a schematic illustration depicting the manner in which the staple of  FIG. 21  is bent and end portions of the staple are bonded together by the robotic mechanism of  FIG. 1 ; 
           [0034]      FIG. 23  is a schematic illustration depicting the relationship of a staple to a portion of a stapling mechanism prior to insertion of the staple into body tissue during operation of the robotic mechanism of  FIG. 1 ; 
           [0035]      FIG. 24  is a schematic illustration, depicting the manner in which the stapling mechanism of  FIG. 23  is pressed against body tissue with a predetermined force by the robotic mechanism of  FIG. 1  prior to insertion of a staple; 
           [0036]      FIG. 25  is a schematic illustration depicting the manner in which the staple of  FIG. 24  is inserted into body tissue by operation of the stapling mechanism by the robotic mechanism of  FIG. 1 ; 
           [0037]      FIG. 26  is a schematic illustration depicting the manner in which the staple of  FIG. 25  is bent and legs of the staple are bonded together by operation of the robotic mechanism of  FIG. 1 ; 
           [0038]      FIG. 27  is a schematic illustration depicting the relationship of viable tissue components to a scaffold or matrix; 
           [0039]      FIG. 28  is a schematic illustration, generally similar to  FIG. 27 , depicting the relationship of viable tissue components to a different scaffold or matrix; 
           [0040]      FIG. 29  is a schematic illustration depicting the manner in which the scaffold and viable tissue components of either  FIG. 27  or  FIG. 28  are connected with body tissue by staples in the manner illustrated in  FIGS. 24-26  by operation of the robotic mechanism of  FIG. 1 ; 
           [0041]      FIG. 30  is a schematic illustration depicting the manner in which the positioning assembly of  FIGS. 9 and 10  is utilized to position the scaffold of  FIG. 27 or 28  relative to body tissue during operation of the robotic mechanism of  FIG. 1 ; 
           [0042]      FIG. 31  is a schematic illustration depicting the manner in which an expandable retractor assembly is positioned by the robotic mechanism of  FIG. 1  to separate body tissue; 
           [0043]      FIG. 32  is a schematic illustration depicting the manner in which an expandable retractor assembly is positioned relative to a shoulder joint by the robotic mechanism of  FIG. 1 ; 
           [0044]      FIG. 33  is a schematic illustration depicting the manner in which an expandable retractor assembly is positioned relative to a vertebra by the robotic mechanism of  FIG. 1 ; 
           [0045]      FIG. 34  is a schematic illustration depicting the manner in which the robotic mechanism of  FIG. 1  is utilized to position a threaded fastener in body tissue; 
           [0046]      FIG. 35  is a schematic illustration depicting the manner in which the robotic mechanism of  FIG. 1  is utilized to position a prosthesis in body tissue; 
           [0047]      FIG. 36  is a schematic illustration, depicting the manner in which a plurality of imaging devices are used in association with the robotic mechanism of  FIG. 1 ; 
           [0048]      FIG. 37  is a schematic illustration depicting the manner in which a fluoroscope is utilized in association with an endoscope and a robotic mechanism during the securing of body tissue in any one of the ways illustrated in  FIGS. 2 through 32 ; and 
           [0049]      FIG. 38  is a schematic illustration depicting the manner in which the robotic mechanism of  FIG. 1  is utilized, with a magnetic resonance imaging unit (MRI) and an endoscope, to secure body tissue in any one of the ways illustrated in  FIGS. 2 through 32 . 
       
    
    
     DETAILED DESCRIPTION 
     Robotic Securing of Tissue 
       [0050]    An apparatus  30  for use in securing tissue in a patient&#39;s body is illustrated schematically in  FIG. 1 . Although the apparatus  30  will be described herein as being used to secure tissue, it is contemplated that the apparatus  30  may be used for other surgical procedures if desired. 
         [0051]    The apparatus  30  includes an operating table  32  which is disposed in a sterile operating room environment. A patient  34  may be covered by a known sterile drapery system. Alternatively, the patient  34  may be covered by a drapery system which is connected with a surgeon so as to maintain a sterile field between the surgeon and the patient in the manner disclosed in U.S. patent application Ser. No. 09/941,185 Filed Aug. 28, 2001 by Peter M. Bonutti. Of course, any desired sterile drapery system may be provided to cover the patient  34 . 
         [0052]    A robotic mechanism  38  is provided to position a tissue securing device, fastener, or other apparatus at a desired location within the patient during performance of a surgical procedure. An imaging device  40  is operable to provide an image of a location where the robotic mechanism  38  is securing the body tissue with a fastener or performing other steps in a surgical procedure. A programmable computer  44  is connected with the robotic mechanism  38  through a robotic arm interface  46 . In addition, the computer  44  is connected with the imaging device  40  and a monitor or display  48 . The monitor or display  48  is visible to a surgeon operating the apparatus  30  and provides an image of the location where the robotic mechanism  38  is being utilized in the performance of a surgical procedure on the patient  34 . 
         [0053]    The robotic mechanism  38  is guided by automatic controls which include the computer  44  and robotic arm interface  46 . The robotic mechanism  38  may have a construction which is different than the illustrated construction and may include one or more adaptive arms. The robotic mechanism  38  is a reprogrammable, multifunctional manipulator designed to move through various programmed motions for the performance of a surgical procedure. The robotic mechanism  38  may have manually operable controls which provide for interaction between the surgeon and the robotic mechanism. The robotic mechanism  38  is utilized in the securing of a patient&#39;s body tissue. However, it is contemplated that the robotic mechanism  38  will be utilized during the performance of other surgical steps in addition to the securing of body tissue. 
         [0054]    The robotic mechanism  38  may have many different constructions, including constructions similar to those disclosed in U.S. Pat. Nos. 5,078,140; 5,572,999; 5,791,231; 6,063,095; 6,231,565; and/or 6,325,808. The specific robotic mechanism  38  illustrated in  FIG. 1  has a construction and mode of operation generally similar to that disclosed in U.S. Pat. No. 5,876,325. However, it should be understood that the robotic mechanism  38  could have any desired construction. The robotic mechanism  38  may have one or more known adaptive arms. 
         [0055]    The use of the robotic mechanism  38  and imaging device  40  enables the size of incisions  52  and  54  in the patient&#39;s body to be minimized. Of course, minimizing the size of the incisions  52  and  54  tends to reduce patient discomfort and recovery time. It contemplated that the robotic mechanism  38  and imaging device  40  will be utilized during the performance of many different surgical procedures. 
         [0056]    During the performances of these surgical procedures, the robotic mechanism  38  may be utilized to secure body tissue. The robotic mechanism  38  may be used to position a suture anchor  60  ( FIG. 2 ) relative to body tissue  64  in the patient  32  during the performance of any one of many known surgical procedures. The body tissue  64  may be hard and/or soft body tissue. 
         [0057]    Once the anchor  60  has been positioned relative to the body tissue  64 , the robotic mechanism  38  is operated to tension a suture  66  connected with the anchor  60  with a predetermined force, in the manner indicated schematically by an arrow  70  in  FIG. 3 . At the same time, the robotic mechanism  38  of  FIG. 1  presses a suture retainer  72  against the body tissue  64  with a predetermined force, indicated schematically by an arrow  74  in  FIG. 3 . The force  74  may be equal to, greater than, or less than the force  70  with which the suture  66  is tensioned. 
         [0058]    The anchor  60 , suture  66 , and suture retainer  72  may be formed of any desired material. The illustrated anchor  60 , suture  66  and suture retainer  77  are all formed of a polymeric material. The anchor  60 , suture  66 , and suture retainer  72  may all be formed of a biodegradable polymeric material. However, the anchor  60 , suture  66 , and/or suture retainer  72  could be formed of metal or other known materials if desired. 
         [0059]    The suture  55  is a monofilament. However, the suture  66  could be formed by a plurality of filaments and could have a braided construction. The suture  66  could have a construction similar to the construction of a rope or cable if desired. 
         [0060]    While the suture  66  is tensioned with the predetermined force  70  and while the suture retainer  72  is pressed against the body tissue  64  with a force  74 , the robotic mechanism  38  plastically deforms the polymeric material of the suture retainer  72  in the manner illustrated schematically in  FIG. 4 . The plastic deformation of the suture retainer  72  by the robotic mechanism  38  may take place at a temperature which is either below or in the transition temperature range for the polymeric material of the suture retainer  72 . Thus, the suture retainer  72  may be plastically deformed by cold flowing material of the suture retainer. 
         [0061]    Alternatively, the suture retainer  72  may be deformed by transmitting force from the robotic mechanism  38  to the retainer after the polymeric material of the retainer has been heated into a transition temperature range of the material of the suture retainer. When the material of the suture retainer  72  has been heated into its transition temperature range, the material can be readily plastically deformed with a viscous flow or movement of the material. It is believed that it may be preferred to maintain the material of the suture  66  at a temperature which is below the transition temperature range for the material of the suture. The suture retainer  72  may be formed of the materials disclosed in U.S. Pat. No. 6,203,565 and heated in the manner disclosed in the patent. 
         [0062]    It is contemplated that the anchor  60 , suture  66 , and suture retainer  72  may all be formed of biodegradable polymeric materials. However, it is believed that it may be desired to form the suture retainer  72  of a biodegradable material having a lower transition temperature range than the transition temperature range for the material of the suture  66 . This would facilitate operation of the robotic mechanism  38  to heat the suture retainer  72  into its transition temperature range without heating the material of the suture  66  into the transition temperature of the material of the suture. This would minimize damage to or deformation of the suture  66  when the suture retainer  72  is deformed by operation of the robotic mechanism  38 . Of course, the anchor  60 , suture  66  and suture retainer  72  could all be formed of the same biodegradable material if desired. 
         [0063]    It is contemplated that, in some circumstances at least, it may be desired to heat both the polymeric material of the suture  66  and the polymeric material of the retainer  72  into their transition temperature ranges. If this is done, the material of the suture  66  and the retainer  72  could be fused together. This would result in a blending of the material of the suture  66  and suture retainer  72  in the area where they are disposed in engagement. 
         [0064]    During operation of the robotic mechanism  38 , the suture retainer  72  is bonded to the suture  66  without significant deformation of the suture. When the polymeric material of the suture retainer  72  is heated into its transition temperature range, the material of the suture retainer softens and loses some of its rigidity. By applying force against the heated material of the suture retainer  72 , the robotic mechanism  38  can be operated to cause the material of the suture retainer to plastically deform and flow around and into engagement with the suture  66 . 
         [0065]    When the material of the suture retainer  72  cools, a secure bond is formed between the material of the suture retainer and the suture  66 . This bond may be formed in the manner disclosed in the aforementioned U.S. Pat. No. 6,203,565. However, it is contemplated that the material of the suture retainer  72  could be plastically deformed and bonded without heating, in the manner disclosed in U.S. Pat. No. 6,010,525. 
         [0066]    It is contemplated that the suture retainer  72  may be plastically deformed by operating the robotic mechanism  38  to press the force transmitting members  80  and  82  against opposite sides of the suture retainer  72  in the manner indicated by arrows  84  and  86  in  FIG. 4 . The force transmitting members  80  and  82  may be pressed against opposite sides of the suture retainer  72  with sufficient force to plastically deform the material of the suture retainer. The resulting cold flowing of the material in the suture retainer  72  would result in the suture retainer bonding to the suture  66 . 
         [0067]    It is contemplated that the suture retainer  72  may be heated by the robotic mechanism into the transition temperature range of the material of the suture retainer in many different ways. For example, the suture retainer  72  may be heated into its transition temperature range by the application of ultrasonic vibratory energy to the suture retainer. If this is to be done, the force transmitting member  80  functions as an anvil and the force transmitting member  82  functions as a horn. To enable the force transmitting member  82  to function as a horn, the force transmitting member is connected with a source  90  of ultrasonic vibratory energy by the robotic mechanism  58 . One commercially available source of ultrasonic vibratory energy is provided by Dukane Corporation Ultrasonics Division, 2900 Dukane Drive, St. Charles, Ill. Of course, there are other sources of apparatus which can be utilized to provide ultrasonic vibratory energy. 
         [0068]    When the ultrasonic vibratory energy is to be applied to the suture retainer  72  by the robotic mechanism, the force transmitting member or horn  82  is vibrated at a rate in excess of 20 kilohertz. Although the horn or force transmitting member  82  may be vibrated at any desired frequency within a range of 20 kilohertz to 70 kilohertz, it is believed that it may be desirable to vibrate the force transmitting member or horn  82  at a rate which is close to or greater than 70 kilohertz. The force transmitting member or horn  82  is vibrated for a dwell time which is sufficient to transmit enough ultrasonic vibratory energy to the suture retainer  72  to heat at least a portion of the material of the suture retainer into its transition temperature range. 
         [0069]    The frictional heat created by the ultrasonic vibratory energy transmitted to the suture retainer  72  is sufficient to heat the material of the suture retainer at locations adjacent to the suture  66 , into the transition temperature range of the material of the suture retainer. As this occurs, the softened material of the suture retainer  72  is plastically deformed by force applied against the suture retainer by the anvil or force transmitting member  80  and the horn or force transmitting member  82 . After interruption of the transmission of ultrasonic vibratory energy to the suture retainer  72 , the material of the suture retainer cools and bonds to the suture  66 . 
         [0070]    The general manner in which ultrasonic vibratory energy is applied to the suture retainer  72  and in which the suture retainer is plastically deformed to grip the suture  66  is the same as disclosed in U.S. patent application Ser. No. 09/524,397 Filed Mar. 13, 2000 by Peter M. Bonutti, et al. and entitled Method of Using Ultrasonic Vibration to Secure Body Tissue. However, it is contemplated that the material of the suture retainer  72  could be heated in ways other than the application of ultrasonic vibratory energy. For example, the suture retainer  72  could be heated by an electrical resistance heater element or by a laser. 
         [0071]    It is contemplated that the robotic mechanism  38  may be operated to secure the body tissue  64  in many different ways utilizing the anchor  60 , suture  66 , and suture retainer  72 . One way in which the body tissue  64  may be secured is by linear apposition in the manner illustrated schematically in  FIG. 5 . A plurality of sutures  66  have a linear configuration and extend between anchors  60  disposed on one side of the body tissue  64  and retainers  72  disposed on the opposite side of the body tissue. 
         [0072]    The sutures  66  are connected with openings which extend diametrically across the cylindrical anchors  60 . However, it is contemplated that the sutures  66  could be connected with the anchors  60  in a different manner by operation of the robotic mechanism  38 . For example, it is contemplated that the sutures  66  could be connected with the anchors  60  in any one of the ways disclosed in U.S. Pat. Nos. 5,534,012; 5,713,921; 5,718,717; or 5,845,645. It is also contemplated that the anchors could have the same construction and/or be formed of materials disclosed in any one of the aforementioned U.S. patents. 
         [0073]    In the embodiment illustrated in  FIG. 5 , the body tissue  64  is formed by a pair of layers  116  and  118  of soft tissue which are held in flat abutting engagement by forces transmitted between the suture anchors  60  and retainers  72  through the sutures  66 . However, the suture anchors  60 , sutures  66 , and retainers  72  could be utilized to secure many different types of body tissue. For example, the anchors  60  could be disposed in a bone and the sutures  66  and retainers  72  utilized to secure soft tissue, such as a tendon or ligament with the bone. The suture anchors  60 , sutures  66  and retainers  72  may be utilized for rotator cuff repairs or meniscus repairs. 
         [0074]    The suture anchor  60 , suture  66  and retainer  72  form a fastener assembly which is used by surgeon controlling operation of the robotic mechanism  38  to secure body tissues together or with surgical implants. The robotic mechanism  38  may be used with many different types of fastener assemblies during performance of surgical procedures at many different locations in a patient&#39;s body. The fastener assembly positioned by the robotic mechanism  38  may be a bonded rivet of the type disclosed in the aforementioned U.S. Pat. No. 6,203,565. However, it should be understood that the fastener assembly may have any desired construction. 
         [0075]    The fastener assembly utilized with the robotic mechanism  38  may be used to secure soft body tissues to each other and/or to secure soft body tissues with hard body tissues. The fastener assembly utilized with the robotic mechanism  38  may be used to secure hard body tissues together. The robotic mechanism  38  may be used to secure a surgical implant, such as a prosthesis, with hard and/or soft body tissue. 
       Anchor, Suture and Retainer Assembly 
       [0076]    In the embodiment invention illustrated in  FIGS. 1-5 , the body tissue  64  is secured with a fastener assembly formed by the anchor  60 , suture  66  and retainer  72 . The fastener assembly is positioned relative to body tissue  64  by the robotic mechanism  38 , that may include one or more adaptive arms having a known construction. 
         [0077]    The use of the robotic mechanism  38  to position the anchor  60 , suture  66  and retainer  72  enables tension force in the suture  66  and force applied against the body tissue by the anchor  60  and retainer  72  to be accurately controlled. By using the imaging device  40  in association with the robotic mechanism  38 , a surgeon can view the monitor  48  and be certain that the anchor  60 , suture  66  and retainer  72  are being positioned in the desired manner in the patient&#39;s body. This enables the surgeon to minimize the size of the incisions  52  and  54  and still have visual assurance that the surgical procedure is being properly performed in the patient&#39;s body by the robotic mechanism. When the robotic mechanism  38  includes adaptive arms, input by the surgeon in response to an image on the monitor  48  is facilitated. 
         [0078]    The robotic mechanism  38  includes a cylindrical tubular inserter member  102  ( FIG. 2 ). The inserter member  102  has a cylindrical passage  104  which extends through the inserter member  102 . The cylindrical passage  104  has a diameter which is slightly greater than the diameter of the cylindrical anchor  60 . 
         [0079]    Although the cylindrical anchor  60  has been illustrated in  FIG. 2  as having a blunt leading end portion, it is contemplated that the cylindrical anchor  60  could have a pointed leading end portion in the manner disclosed in U.S. Pat. No. 5,718,717. Alternatively, the anchor could be constructed as disclosed in U.S. patent application Ser. No. 09/556,458 filed May 3, 2000 by Peter M. Bonutti and entitled Method and Apparatus for Securing Tissue and have a pointed leading end portion. 
         [0080]    The anchor  60  may be formed of a material which absorbs body liquid while the pointed leading end portion of the anchor is formed of a different material that is relatively rigid and capable of piercing the imperforate body tissue  64 . When the body of the anchor  60  absorbs body liquid, the anchor expands in all directions and forms an interlock with the body tissue  64  in the manner disclosed in U.S. Pat. No. 5,718,717. Of course the pointed end portion of the anchor could be omitted in the manner also disclosed in the aforementioned U.S. Pat. No. 5,718,717. 
         [0081]    When the anchor  60  is to be inserted into the body tissue by the robotic mechanism, a cylindrical pusher member  108  is pressed against the trailing end of the anchor  60 . The pusher member  108  is telescopically moved along the passage  104  by a suitable drive assembly in the robotic mechanism  38 . When the pusher member  108  has moved the anchor to a desired position relative to the body tissues  64 , the robotic mechanism  38  is operated to extend a push rod  112  from the pusher member  108 . The push rod  112  applies a force to the anchor  60  at a location offset from a central axis of the anchor. The resulting torque on the anchor  60  causes the anchor to pivot relative to the body tissue  64  and change orientation relative to the body tissue. 
         [0082]    The manner in which the pusher member  108  is moved along the passage  104  in the inserter member  102  by the robotic mechanism  38  may be the same as is disclosed in U.S. patent application Ser. No. 09/789,621 filed Feb. 21, 2001 by Peter M. Bonutti and entitled Method of Securing Body Tissue. The manner in which the anchor  60  pivots relative to the body tissue  64  when the push rod  112  is extended from the pusher member  108  may be the same as is disclosed in U.S. Pat. No. 5,814,072. However, the anchor  60  may be pivoted relative to the body tissue  64  in a different manner if desired. For example, the anchor  60  could be pivoted relative to the body tissue  64  in the manner disclosed in U.S. Pat. No. 5,782,862. 
         [0083]    In the embodiment invention illustrated in  FIG. 2 , the body tissue  64  includes an upper or first layer or segment  116  and a lower or second layer or segment  118 . The two layers  116  and  118  are soft body tissues through which the anchor  60  is pushed by the pusher member  80 . As the anchor  60  emerges from lower layer  118  of the body tissue  64 , the push rod  112  is extended to cause the anchor  60  to pivot or toggle relative to the lower layer  118  of body tissue. 
         [0084]    In the embodiment invention illustrated in  FIG. 2 , the anchor  60  is pushed through the two layers  116  and  118  of body tissue. However, it is contemplated that the anchor  60  could be pushed through only the upper layer  116  of body tissue. The anchor would be moved into the lower layer  118  of body tissue and pivoted or toggled by extension of the push rod  112  from the pusher member  108 . This would position the anchor in the lower layer  118  of body tissue. It is contemplated that lower portion  118  of the body tissue could be relatively thick, compared to the upper layer  116 . 
         [0085]    If desired, the anchor  60  may not be moved through the upper layer  116  of body tissue. The anchor  60  may be moved into and/or through only the layer  118  of body tissue. Once this has been done, the suture  66  may be moved through the layer  116  of body tissue. 
         [0086]    It is also contemplated that the anchor could be positioned in hard body tissue. For example, the anchor  60  could be positioned in bone in the manner disclosed in U.S. Pat. No. 6,033,430. When the anchor  60  is positioned in bone, the suture  66  may be used to secure a tendon or ligament to the bone in the manner disclosed in U.S. Pat. No. 6,152,949. Regardless of whether the anchor  60  is positioned in hard body tissue or soft body tissue, the anchor may be formed of any one of the materials and/or constructed in any one of the ways disclosed in the aforementioned U.S. Pat. No. 6,152,949. 
         [0087]    Once the anchor  60  has been moved to the desired orientation relative to the body tissue ( FIG. 3 ), the retainer  72  is positioned relative to the suture  66  and body tissues. The retainer  72  has a spherical configuration with a diametrically extending central passage  120 . However, the retainer  72  may have any desired construction, for example, any one of the constructions disclosed in U.S. Pat. No. 6,159,234. Alternatively, the retainer  72  may have any one of the constructions disclosed in U.S. patent application Ser. No. 09/524,397 filed Mar. 13, 2000 by Peter M. Bonutti et al. and entitled Method of Using Ultrasonic Vibration to Secure Body Tissue. 
         [0088]    The suture retainer  72  and suture  66  are both preferably formed of a biodegradable polymer, such as polycaperlactone. Alternatively, the suture  66  and/or suture retainer  72  could be formed of polyethylene oxide terephthalate or polybutylene terephthalate. It is contemplated that other biodegradable or bioerodible copolymers could be utilized if desired. The suture anchor  60  may be formed of the same material as the suture  66  and/or retainer  72 . Also, the suture  66  and/or retainer  72  could be formed of an acetyl resin, such as “Delrin” (Trademark). Alternatively, the suture  66  and/or suture retainer  72  could be formed of a pora-dimethylamino-benzenediazo sodium sulfonate, such as “Dexon” (Trademark). The suture  66  may also be a monofilament or formed of a plurality of interconnected filaments. 
         [0089]    Although it may be desired to form the anchor  60  of the same material as the suture  66  and/or retainer  72 , the anchor could be formed of a different material if desired. For example, the anchor  60  may be formed of body tissue, such as bone or other dense connective tissue. The anchor  60  may be formed of many different materials containing collagen. The anchor  60  may be formed of natural or synthetic materials which absorb body fluid and expand when positioned in a patient&#39;s body. As the anchor expands in the patient&#39;s body, a solid interlock is obtained with adjacent tissue in the patient&#39;s body. The anchor  60  may be formed of any of the materials disclosed in the aforementioned U.S. Pat. Nos. 5,713,921 and/or 5,718,717. 
         [0090]    Once the anchor  60  has been moved to the position illustrated in  FIG. 3  by operation of the robotic mechanism  38 , the suture  66  is tensioned with a predetermined force in the manner illustrated schematically by the arrow  70 . To tension the suture  66 , the robotic mechanism  38  ( FIG. 1 ) includes a tensioner  122  ( FIG. 3 ). The tensioner  122  determines when a predetermined tension force has been applied to the suture. The tensioner  122  is then effective to maintain the predetermined tension force. 
         [0091]    The tensioner  122  and computer  44  may be set to limit the magnitude of the tension applied to the suture  66  to a preselected magnitude. Alternatively, the tensioner  122  and computer  44  may have a visual readout which enables a surgeon to determine the magnitude of the tension in the suture  66  and to maintain the tension in the suture at a desired magnitude. The image provided at the monitor  48  facilitates control of the tension in the suture  66  by the surgeon. If this is done, the tensioner  122  may be set to limit the tension in the suture to a desired maximum. 
         [0092]    The tensioner  122  may include a gripper which grips the suture  66 . A drive mechanism is operable to move to the gripper to tension the suture  66 . The drive mechanism includes a pezielectric cell which detects when the tension transmitted from the gripper to the suture  66  has reached the predetermined magnitude. The drive mechanism may move the gripper to maintain the tension in the suture at the predetermined magnitude. Alternatively, the drive mechanism may respond to inputs from the surgeon. 
         [0093]    Of course, the tensioner  122  could have a different construction if desired. For example, the tensioner  122  could include a spring, deflected through a predetermined distance to maintain a predetermined tension on the suture  66 . The tensioner  122  could also have a construction similar to construction disclosed in U.S. patent application Ser. No. 09/556,458 Filed May 3, 2000 by Peter M. Bonutti and entitled Method and Apparatus for Securing Tissue. 
         [0094]    While the suture  66  is tensioned with a predetermined force by the tensioner  122 , a retainer pusher member  126  is pressed against the retainer  72  with a predetermined force indicated schematically by an arrow  74  in  FIG. 3 . The retainer pusher member  126  is pressed against the retainer  72  by a pusher assembly  128  disposed in the robotic mechanism  38  ( FIG. 1 ). The pusher assembly  128  includes a drive assembly which applies a predetermined force to the retainer pusher member  126 . This force presses the retainer  72  against the upper layer  116  of body tissue  64 . 
         [0095]    While the retainer  72  is being pressed against the body tissue  64  with a predetermined force, the suture  66  is tensioned with a predetermined force by the tensioner  122 . The force transmitted through the suture  66  presses the anchor  60  against the lower layer  118  of body tissue with a predetermined force. The force with which the anchor  60  is pressed against the body tissue  118  may be the same as, less than, or greater than the force with which the retainer is pressed against the tissue  116 . This results in the two layers  116  and  118  of body tissue being clamped between the suture  60  and retainer  72  with a predetermined force. 
         [0096]    The anchor  60  is pulled against a bottom surface  132  of the lower layer  118  of body tissue and the retainer  72  is pressed upper against the surface  134  of the upper layer  116  of body tissue. This results in the two layers  116  and  118  of body tissue being gripped between the retainer  72  and anchor  60  with a predetermined compressive force. This compressive force is a function of the sum of the tension force  70  transmitted to suture  66  by the tensioner  122  and the force  74  transmitted to the retainer pusher member  126  by the pusher assembly  128 . A force distribution member, such as a button, may be provided between the anchor  60  and surface  132  of the body tissue  118 . Another force distribution member may be provided between the retainer  120  and the surface  134  of the body tissue  116 . 
         [0097]    The pusher assembly  128  may have any desired construction, including for example, a hydraulically actuated piston and cylinder type motor in which the fluid pressure determines the magnitude of the force  74 . Alternatively, an electric motor could be associated with a screw type drive and a force measurement device to apply the force  74  to the retainer pusher member  126 . The force measurement device may be a piezoelectric cell or a spring assembly to control energization of the electric motor. 
         [0098]    While anchor  60  and retainer  72  are being pressed against their respective body tissues, the robotic mechanism  38  is effective to plastically deform the retainer  72  to grip the suture  66 . A retainer deformation assembly  144  ( FIG. 4 ) in the robotic mechanism  38  is moved along the retainer pusher member  126  and suture  66  into engagement with the upper layer  116  of body tissue. A drive assembly  148  in the robotic mechanism  38  is effective to press the retainer deformation assembly  144  against the upper layer  116  of body tissue with a predetermined force. The force with which the retainer deformation assembly  144  is pressed against the upper layer  116  of body tissue may be of the same magnitude or less than the force  74  with which the retainer  72  is pressed against the upper layer  116  of body tissue by the robotic mechanism  38 . 
         [0099]    The retainer deformation assembly  144  includes a tubular cylindrical inner member  152  having a central cylindrical passage  154  in which the retainer pusher member  126  is telescopically received. A cylindrical outer member  156  extends around the cylindrical inner member  152  and is disposed in a coaxial relationship with the inner member  152  and retainer pusher member  126 . 
         [0100]    The force transmitting members  80  and  82  are carried by the inner member  152 . When the inner member  152  is pressed against the upper layer  116  body tissue, the force transmitting members  80  and  82  are aligned with the suture retainer  72 . At this time, the force transmitting members  80  and  82  are disposed below (as viewed in  FIG. 4 ) a lower end of the pusher member  126  and are disposed radially outward from the spherical retainer  72 . 
         [0101]    When the retainer  72  is to be plastically deformed to grip the suture  66 , the outer member  156  is moved downward (as viewed in  FIG. 4 ) toward the upper layer  116  of body tissue by a drive assembly  160  disposed in the robotic mechanism  38 . The drive assembly  160  presses the lower (as viewed  FIG. 4 ) end of the outer member  156  against the force transmitting member  84  and  86  with a predetermined force, indicated schematically at  162  in  FIG. 4 . This force cams the force transmitting members  80  and  82  radially inward against the suture retainer  72 . 
         [0102]    The camming force  162  transmitted from the outer member  156  to the force transmitting members  80  and  82  causes the force transmitting members to move inward toward the suture retainer  72 , as indicated by arrows  84  and  86 . The force indicated by the arrows  84  and  86  causes the passage  120  ( FIG. 3 ) to collapse and the material of the suture retainer  72  to move into engagement with and grip the suture  66 . The manner in which the material of the retainer  72  is plastically deformed by the force transmitting members  80  and  82  may be the same as is disclosed in U.S. Pat. No. 6,159,234. 
         [0103]    In order to facilitate deformation of the retainer  72 , the material of the suture retainer may be heated. Heating of the material of the retainer  72  results in the material becoming soft and malleable under the influence of forces  84  and  86  applied by the force transmitting members  80  and  82 . Ultrasonic vibratory energy is transmitted to the force transmitting member  82  from a source or generator  90  of ultrasonic vibratory energy. The force transmitting member  82  functions as a horn and applies the ultrasonic vibratory energy to the retainer  72 . The force transmitting member  80  acts as an anvil which presses against the opposite side of the retainer  72 . 
         [0104]    As ultrasonic vibratory energy is transmitted to the retainer  72  and the temperature of the retainer increases, the material of the retainer is heated into its transition temperature range and softens. As the material of the retainer  72  softens, the forces  84  and  86  applied against the retainer by the force transmitting members  80  and  82  cause the material of the suture retainer to flow or ooze around and engage the suture  66 . 
         [0105]    The softened material of the retainer  72  engages the suture and bonds to the suture without significant deformation of the suture. Materials of the suture  66  and retainer  70  are chemically compatible so that a molecular bond can be established between the retainer and the suture. Like materials, that is materials having chemical properties which are the same or very similar, usually bond together. However, dissimilar materials may bond if their melt temperatures are reasonably close and they are of like molecular structure. Generally speaking, amorphous polymers are readily bonded to each other. 
         [0106]    While it is preferable to heat the material of the retainer  72  by the application of energy, such as ultrasonic vibratory energy, other sources of energy could be used. For example, the retainer  72  could be heated by a laser or resistance wire. Regardless of whether or not the material of the retainer  72  is heated, the suture  66  is tensioned with the predetermined force  70 . At the same time, the retainer  72  is urged toward the body tissue  64  of the predetermined force  74  when the retainer  72  is plastically deformed to grip the suture  66 . 
         [0107]    The anchor  60  could be formed out of body tissue in the manner disclosed in the aforementioned U.S. Pat. No. 5,713,921. The body tissue may be bone. If the anchor is formed of bone, the anchor may be formed with either the configuration illustrated in  FIGS. 2-4  or may have a configuration similar to that disclosed in U.S. patent application Ser. No. 09/556,458 Filed May 3, 2000, by Peter M. Bonutti and entitled Method And Apparatus For Securing Tissue. Alternatively, the anchor could have any one of the constructions disclosed in U.S. Pat. Nos. 5,527,343; 5,534,012 and 5,718,717. 
         [0108]    The inserter member  102  could have a construction different from the construction illustrated in  FIG. 2 . For example, the inserter member  102  could have a construction similar to any one of the constructions disclosed in U.S. Pat. No. 6,033,430. 
       Linear Apposition 
       [0109]    The robotic mechanism  38  may be operated to place the layers  116  and  118  of body tissue in a side-by-side relationship, in the manner illustrated schematically in  FIG. 5 . When the layers of body tissue have been placed in the side-by-side relationship by the robotic mechanism  38 , the pusher member  108  and inserter member  102  are utilized to move each of the anchors  60  in turn through the two layers  116  and  118  of body tissue in the manner previously discussed in connection with  FIGS. 2-4  herein. While each of the sutures  66  in turn is tensioned, the retainer  72  is plastically deformed to securely grip the suture. Although each of the anchors  60 , sutures  66  and retainers  72  of  FIG. 5  was positioned relative to the body tissue  64  by the robotic mechanism  38  in turn, the robotic mechanism could be constructed so as to position a plurality of the anchor  60 , suture  66  and retainers  72  relative to the body tissue  64  at one time. 
         [0110]    Regardless of how the anchor  60 , suture  66  and retainers  72  are positioned relative to the body tissue  64 , each of the sutures  66  is tensioned so that it extends in a straight line between an anchor  60  and retainer  72  in the manner illustrated in  FIG. 5 . The anchors  60 , sutures  66  and retainers  72  are spaced a desired distance apart along the edges of the body tissue  64  to secure the body tissue in linear apposition, as illustrated in  FIG. 5 . It is also possible that the layers  116  and  118  could be interconnected in a different manner if desired. For example, the robotic mechanism  38  could be operated to connect the layers  116  and  188  of body tissue in the manner disclosed in U.S. Pat. No. 5,549,631. 
         [0111]    Under certain circumstances, body tissues are preferably joined in end-to-end relationship rather than the side-by-side relationship illustrated schematically in  FIG. 5 . For example, a break  172  may be formed between portions  174  and  176  of body tissue  64  ( FIG. 6 ) by operation of the robotic mechanism  38 . When the portions  174  and  176  of the body tissue are to be secure in this orientation, the suture anchor inserter member  102  and pusher number  108  ( FIG. 2 ) are skewed at an acute angle relative to an upper (as viewed in  FIG. 6 ) side surface  178  and to a lower side surface  180  of the portions  174  and  176  of the body tissue  64 . Of course, the retainer deformation assembly  144  would also be skewed at a similar angle relative to the side surfaces  178  and  180  of the body tissue  64 . This would allow the sutures  66  to be tensioned across the joint  172  between the two portions  174  and  176  of the body tissue  64 . This would be particularly advantageous to provide the sutures  66  with the orientation illustrated in  FIG. 6  when the portions  174  and  176  of body tissue to be interconnected are formed of bone. 
         [0112]    A plurality of anchors  60 , sutures  66  and retainer  72  may be provided across the break  172  between the portions  174  and  176  of a bone to be interconnected in the manner disclosed U.S. Pat. No. 6,117,160. It should be understood that the suture  66  could be utilized to connect soft body tissue with the portions  174  and  176  of bone in much the same manner as is disclosed in U.S. Pat. No. 6,117,160 and/or U.S. Pat. No. 6,152,949. The anchor  60 , suture  66 , and retainer  72  may be utilized to interconnect bone fragments in a manner similar to that disclosed in U.S. Pat. No. 6,117,160. 
       Plural Retainers 
       [0113]    In the embodiments of the invention illustrated in  FIGS. 2-6 , an anchor  66  and retainer  72  have been connected with a suture. However, it is contemplated that a plurality of retainers  72  could be connected with a single suture. This could result in the suture  66  being tensioned between a pair of retainers  72  in the manner illustrated in  FIG. 7  by operation of the robotic mechanism  38 . 
         [0114]    The two layers  116  and  118  of body tissue  64  ( FIG. 7 ) are moved into a side-by-side relationship by operation of the robotic mechanism  38 . The robotic mechanism  38  then utilizes a needle or other suture passer to move the suture  66  through the two layers of body tissue. The suture  66  may be moved through the body tissue  64  in the manner disclosed in U.S. patent application Ser. No. 10/005,652 filed Dec. 3, 2001, by Peter M. Bonutti for Magnetic Suturing System and Method. Of course, other known methods could be utilized in association with the robotic mechanism  38  to move the suture through the body tissue  64 . 
         [0115]    The retainers  72 , ( FIG. 7 ) are moved into engagement with the suture  66 . The suture  66  is tensioned between upper and lower tensioners  122 . While the suture  66  is tensioned by a pair of tensioners  122  ( FIG. 7 ), a pair of retainer pusher members  126  press the retainers  72  against the upper and lower layers  116  and  118  of body tissue with predetermined forces, indicated by arrows  74  in  FIG. 7 . This results in the layers  116  and  118  of body tissue being firmly gripped between the upper and lower retainers  72  with a predetermined force. 
         [0116]    While the suture  66  is being tensioned with a predetermined force and while the retainers  72  are being pressed against the layers  116  and  118  with a predetermined force, the pair of retainer deformation assemblies  144  are pressed against opposite sides of the body tissue  64  by drive assemblies  148 . The retainer deformation assemblies  144  are pressed against the body tissue with a predetermined force which may be the same as the force with which the retainers  72  are pressed against the two layers  116  and  118  of body tissue. 
         [0117]    The force transmitting members  80  and  82  are moved radially inward against spherical outer side surfaces of the upper and lower retainers  72 . To press the force transmitting members  80  and  82  against the retainers  72  with a predetermined force, an upper tubular cylindrical outer member  156  is moved downward toward the upper layer  116  of body tissue  64  by a drive assembly  160 . At the same time, a lower tubular cylindrical outer member  156  is moved upward toward the lower layer  118  of body tissue by a drive assembly  160 , causing the upper and lower force transmitting members  80  and  82  to be jammed radially inward toward the retainers  72  to plastically deform the retainers and securely grip the suture  66 . 
         [0118]    As it was previously described in conjunction with the embodiment of the invention illustrated in  FIG. 4  ultrasonic vibratory energy can be transmitted from a generator  90  connected with the upper force transmitting member  82  and from a generator  90  connected with the lower force transmitting member  82  to effect a heating of the material of the suture retainers  72 . Of course, heat energy could be transmitted to the retainers  72  in a different manner if desired. Also, the retainers  72  could be plastically deformed without being heated. 
         [0119]    Once the two retainers  72  have gripped the suture  66 , the robotic mechanism  38  is operated to withdraw the retainer deformation assemblies  144  and pusher members  126 , suitable cutters are then utilized to trim the suture  66 . This may be accomplished in the manner disclosed in the aforementioned U.S. patent application Ser. No. 09/556,458 filed May 3, 2000. 
         [0120]    A plurality of retainer and suture assemblies may be utilized to effect the linear apposition of body tissue in the manner illustrated in  FIG. 8 . The sutures  66  are tensioned and connected in a straight line relationship between retainers  72 . This enables the sutures  66  and retainers  72  to hold the two layers  116  and  118  of body tissue in a side-by-side relationship with each other. 
         [0121]    The linear apposition of the layers  116  and  118  of body tissue in the manner illustrated in  FIGS. 5 and 8  and the linear interconnection of portions  174  and  176  of body tissue  64  in  FIG. 6  result in a spot weld effect between separate pieces of body tissue at the locations where the sutures  66  extend through the of body tissue. The straight line connection provided by the suture  66  extending between either an anchor  60  and retainer  72  or two retainers  72 , holds the portions  116  and  118  of body tissue against movement relative to each other when the patient&#39;s body moves. If the portions of body tissue were interconnected with a looped suture, the pieces of body tissue could shift relative to each other when the patient moves. 
         [0122]    Although only a single suture  66  has been illustrated in  FIG. 6 , it should be understood that a plurality of sutures are disposed in a linear array along the joint  172 . Although the suture  66  has been illustrated in  FIG. 6  as being connected between an anchor  60  and retainer  72 , the suture  66  could be connected a plurality of retainers  72  in the same manner as illustrated in  FIG. 8 . 
         [0123]    In  FIGS. 5 through 8 , the anchors  60 , sutures  66  and retainers  72  are preferably all formed of the same biodegradable polymeric material. However, it is contemplated that the anchors  60 , sutures  66 , and/or retainers  72  could be formed of different materials if desired. For example, the anchors  60  and/or retainers  72  could be formed of collagen. Alternatively, the anchors  60  and/or retainers  72  could be formed of body tissue, such as bone, in the manner disclosed in U.S. Pat. No. 5,713,921 and/or U.S. patent application Ser. No. 09/556,458 Filed May 3, 2000 and entitled Method and Apparatus For Securing Tissue. 
         [0124]    Although it is preferred to utilize the robotic mechanism  38  to position the anchors  60 , sutures  66  and retainers  72 , they could be manually positioned in the body tissue if desired. For example, the anchors could be positioned in either hard or soft body tissue in the manner disclosed in U.S. Pat. No. 5,527,343 or U.S. Pat. No. 6,033,430. However, it is preferred to utilized the robotic mechanism  38  to position the anchors  60 , sutures  66  and retainers  72  in the manner previously described in order to facilitate accurate positioning and tensioning of the sutures with minimally invasive surgery. 
       Tissue Positioning Assembly 
       [0125]    A tissue positioning assembly  200  ( FIGS. 9-15 ) forms part of the robotic mechanism  38  ( FIG. 1 ), but may be manually operated separately. Although the tissue positioning assembly  200  is advantageously utilized in conjunction with the robotic mechanism  38 , it may be utilized without the robotic mechanism  38 . Thus, the tissue positioning assembly may advantageously be utilized when body tissue  64  is to be manually secured utilizing prior art methods. 
         [0126]    The tissue positioning assembly  200  includes a long thin member  202  connected with and moved by the robotic mechanism  38 . The long thin member  202  has a leading end portion  204  which is utilized to pierce the layers  116  and  118  of body tissue  64 . The leading end portion  204  of the long thin member  202  is pointed to facilitate piercing imperforate surface areas on the layers  116  and  118  of body tissue  64 . 
         [0127]    The long thin member  202  is illustrated in  FIG. 9  as being moved through the layers  116  and  118  of body tissue while there is a space  208  between the layers of body tissue. Although it is believed that the long thin member  202  may advantageously pierce imperforate surfaces on the layers  116  and  118  of body tissue  64  while they are spaced apart in the manner illustrated schematically in  FIG. 9 , the long thin member  202  may be utilized to pierce the layers  116  and  118  of body tissue while they are disposed in engagement with each other. The long thin member  202  pierces the layers  116  and  118  of body tissue under the influence of force transmitted to the long thin member from the robotic mechanism  38 , but may be moved manually. 
         [0128]    The tissue positioning assembly  200  may be utilized in association with two or more pieces of bone. Thus, the long thin member  202  could be moved across a fracture or break in a bone or could extend through a main portion of a bone and a bone fragment during interconnection of the separate portions of the bone in a manner similar to that disclosed in U.S. Pat. No. 6,045,551. Similarly, the tissue positioning assembly  200  may be used with both hard and soft body tissue, as disclosed in U.S. Pat. No. 5,527,343 and/or U.S. patent application Ser. No. 09/789,621 filed Feb. 21, 2001, by Peter M. Bonutti and entitled Method of Securing Body Tissue. 
         [0129]    The leading end portion  204  of the long thin member  202  is expandable from the contracted condition of  FIG. 9  to the expanded condition of  FIG. 10  after the long thin member  202  has been inserted through the two layers  116  and  118  of body tissue and while the space  208  is present between the two layers of body tissue. Once the leading end portion  204  of the long thin member  202  has been expanded, a force indicated schematically in  212  in  FIG. 10 , is applied to the long thin member  202 . The axial force applied to the long thin member  202  pulls the long thin member upward (as viewed in  FIGS. 9 and 10 ). 
         [0130]    As the long thin member  202  is pulled upward, the expanded leading end portion  204  ( FIG. 10 ) moves into abutting engagement with a surface on the lower layer  118  of body tissue  64 . The force  212  is transmitted from the expanded leading end portion  204  to the lower (as viewed in  FIG. 10 ) surface  132  of the layer  118  of body tissue. The force  212  is transmitted to the long thin member  202  from the robotic mechanism  38 . However, the force  212  could be manually applied to the long thin member if desired. 
         [0131]    The force on the lower layer  118  of body tissue pulls the lower layer of body tissue upward toward the upper layer  116  of body tissue, eliminating space  208  ( FIG. 9 ) between the layers  116  and  118  of body tissue. Therefore, an upper surface of the layer  118  of body tissue moves into engagement with a lower surface of the layer  116  of body tissue. 
         [0132]    The tissue positioning assembly  200  may be used to move the layers  116  and  118  of body tissue together to a desired position in a patient&#39;s body. Thus, after the upper and lower layers  116  and  118  of body tissue  64  have been moved into engagement ( FIG. 10 ), they may be moved sidewardly in the patient&#39;s body. This may be accomplished by applying, to the long thin member  202 , a force which extends transverse to central axis of the long thin member. This transverse force moves the long thin member  202  and the layers  116  and  118  of body tissue to either the left or the right as viewed in  FIG. 10 . The transverse force can be transmitted from the robotic mechanism or manually applied. 
         [0133]    If desired, a cannulated anchor  216  ( FIG. 11 ) may be moved along the long thin member  202  into the body tissue  64 . The anchor  216  is moved under the influence of force applied against the trailing end of the anchor  216  by a tubular cylindrical pusher member  220  ( FIG. 11 ). The pusher member  220  has a cylindrical central passage  222  through which the long thin member  202  and suture  66  extend. The suture  66  is connected to the cannulated anchor  216 . 
         [0134]    The pusher member  220  applies an axial force to the cannulated anchor  216 . This force slides the anchor  216  along the long thin member  200  to move the anchor  216  through the upper (as viewed in  FIG. 11 ) layer  116  of body tissue into the lower layer  118  of body tissue. 
         [0135]    As the anchor  216  moves through the lower layer  118  of body tissue to a position adjacent to the expanded leading end portion  204 , the leading end portion  204  is returned to the contracted condition of  FIG. 9 . The anchor  216  is then pushed downward (as viewed in  FIG. 11 ) through the lower layer  118  of body tissue, becoming disengaged from the long thin member  202 . Thus, the cannulated anchor  216  is pushed or slid off of the contracted leading end portion  204 . 
         [0136]    The long thin member  202  is then withdrawn from the body tissue  64  and, contemporaneously with withdrawal of the long thin member  202 , the anchor  216  is pivoted or toggled to the orientation of the anchor  60  in  FIG. 3 . Once this has been accomplished, tensioning of the suture  66  is effective to press the anchor  216  firmly against the surface  132  of the lower (as viewed in  FIG. 11 ) layer  118  of body tissue. 
         [0137]    A retainer  72  is then pressed against the upper layer  116  of body tissue by a retainer pusher member, corresponding to the retainer pusher member  126  of  FIG. 3 . While the retainer is pressed against the body tissue with a predetermined force and the suture  66  is tensioned with a predetermined force, the suture retainer is deformed to grip the suture  66  in the same manner as previously described in conjunction with  FIG. 4 . 
         [0138]    The cannulated anchor  216  has been illustrated as having a fustro conical leading end  226  which is connected with a cylindrical body  228 . The conical configuration of the leading end  226  of the anchor facilitates movement of the anchor through the body tissue  64  under the influence of force applied against the trailing end of the anchor by the pusher member  220 . However, the anchor  216  could have a different configuration, for example, a configuration corresponding to the configuration of the anchors  FIGS. 2 and 3  herein. 
         [0139]    The long thin member  202  is moved into the body tissue  64 , the leading end portion  204  expanded, and the long thin member pulled upward, as viewed in  FIG. 10 , under the control of the robotic mechanism  38 . However, these steps could all be performed apart from the robotic mechanism  38  if desired. For example, these steps could be performed by a mechanism which is separate from the robotic mechanism  38 . Alternatively, these steps could be performed manually. 
         [0140]    In the embodiment illustrated in  FIG. 11  the anchor  216  is moved along the long thin member  202  with a central axis of the anchor coincident with a central axis of the long thin member. In the embodiment illustrated in  FIG. 12 , the anchor  60  is moved along the long thin member with the anchor offset to one side of the long thin member. As the anchor  60  transmits a downwardly directed (as viewed in  FIG. 12 ) force from the pusher member  108  to the body tissue  64 , the long thin member  202  transmits an upwardly directed force  212  to the body tissue. As was previously mentioned, the long thin member  202  may also apply a sideward force, that is, a force transverse to the central axis of the long thin member, to the body tissue  64 . The results in the body tissue  64  being maintained in a desired position during movement of the anchor  60  through the layer  116  of body tissue into the layer  118  of body tissue. 
         [0141]    The anchor  60  may be pivoted or toggled in the layer of body tissue  118  in response to axially downward movement of the push rod  112  ( FIG. 12 ). As the push rod  112  is pressed downward against the anchor  60  by the robotic mechanism  38 , a torque is applied to the anchor  60 . This torque causes the anchor  60  to pivot and deflect body tissue  118  in the manner disclosed in U.S. Pat. No. 6,033,430. Once the anchor  60  has pivoted to the orientation shown in  FIG. 3  with the anchor enclosed by the body tissue  118 , tension forces in the suture  66  are transmitted through the anchor  60  to the body tissue  118 . Downward forces applied to the body tissue  64  by the anchor  60  during pivoting of the anchor are offset by upward force transmitted through the thin elongated member  202  to the body tissue. 
         [0142]    After the anchor  60  has been pivoted to the desired orientation in the body tissue  118 , the long thin member  202  is withdrawn from the two layers  116  and  118  of body tissue  64 . Before this can be done, the leading end portion  204  of the long thin member  202  is operated from the expanded condition of  FIG. 12  to the contracted condition of  FIG. 9 . The long thin member  202  can then be pulled from the body tissue  64  by either operation of the robotic mechanism  38  or the application of manual force to the long thin member. 
         [0143]    Although the anchor  60  has been described above as moving only part way through the lower layer  118  of body tissue, the anchor  60  could be moved completely through the lower layer  118  of body tissue and into the orientation shown in  FIG. 3 . Tensioning the suture  66  would then result in force being transmitted from the anchor  60  to the lower (as viewed in  FIG. 12 ) surface  132  of the layer  118  of body tissue. 
         [0144]    It is contemplated that it may be desired to grip the two layers  116  and  118  of body tissue with a clamping action. When this is to be done, a tubular cylindrical gripper member  232  is pressed against the surface  134  on the upper (as viewed in  FIG. 12 ) layer  116  of body tissue  64 . This clamps the two layers  116  and  118  of body tissue between the gripper member  232  and the expanded leading end portion  204  of the long thin member  202 . Thus, the long thin member  202  is pulled upward (as viewed in  FIG. 12 ) with the force  212  to press the expanded leading end portion  204  of the long thin member against the lower surface  132  of the layer  118  of body tissue. At the same time, the gripper member  232  is pressed against the upper surface of the layer  116  of body tissue with a force indicated at  234  in  FIG. 12 . 
         [0145]    The anchor  60  is moved along the long thin member  202  into the body tissue  64  at a location offset to one side of and disposed adjacent to the long thin member  202 . The tissue positioning assembly  200  ( FIG. 12 ) is effective to grip the body tissue  64  between the gripper member  232  and the expanded end portion  204  of the long thin member  202 . The tissue positioning assembly  200  is effective to hold the gripped body tissue  64  in any desired position in the patient&#39;s body. 
         [0146]    The gripped body tissue  64  can be moved to any desired position in the patient&#39;s body by moving the long thin member  202  and gripper member  232 . Thus, the long thin member  202  and gripper member  232  can be moved upward, downward, and/or sideward while gripping the body tissue  64 . The long thin member  202  and gripper member  232  can be moved manually or by the robotic mechanism  38  to move the body tissue  64  to a desired location in a patient&#39;s body. 
         [0147]    While the anchor  60  is pushed through the two layers  116  and  118  of body tissue by the pusher member  108  as previously described in conjunction with  FIG. 2  herein, the body tissue is gripped by the long thin member  202  and gripper member  232 . Since the body tissue  64  is securely held, the body tissue does not move under the influence of force transmitted from the pusher member  108  through the anchor  60  to the body tissue as the anchor moves through the body tissue. Thus, when the anchor  60  moves into the body tissue, the anchor applies a force which urges the body tissue to move downward (as viewed in  FIG. 12 ). The upward (as viewed in  FIG. 12 ) force  212  transmitted to the leading end portion  204  of the long thin member  202  through the body tissue  64  holds the body tissue in a desired position as the anchor  60  moves into the body tissue. In addition, the long thin member  202  is effective to hold the body tissue against sideways movement during insertion of the anchor  60  into the body tissue. 
         [0148]    Once the anchor  60  has been moved to a desired position relative to the body tissue  64 , the long thin member  202  and gripper member  232  ( FIG. 12 ) hold the gripped body tissue in a desired position against the influence of force transmitted through the suture  66 . This enables the suture  66  to be tensioned without moving the body tissue  64 . After the suture  66  has been connected in any desired manner, the long thin member  202  and gripper member  232  are disengaged from the body tissue  64 . 
         [0149]    It is preferred to have the tissue positioning assembly  200 , the inserter member  102 , and the pusher member  108  be part of the robotic mechanism  38 . The force transmitted from the robotic mechanism to the inserter member  102  and pusher member  108  enables the anchor  60  to be pushed into the body tissue  64  with a desired force. However, it should be understood that the tissue positioning assembly  200 , the inserter member  102 , and the pusher member  108  could be separate from the robotic mechanism  38  and could be manually operated. 
         [0150]    The tissue positioning assembly  200  may also be utilized to indicate the depth to which the anchor  60  must be moved into the body tissue  64  by the pusher member  108 . The leading ending portion  204  of the long thin member  202  ( FIG. 12 ) is disposed at a known depth relative to the body tissue. By moving the anchor  60  to a depth which slightly exceeds the depth of the leading end portion  204  of the long thin member  202 , the anchor  60  is pushed to a known depth relative to the body tissue. 
         [0151]    An encoder connected with a drive assembly in the robotic mechanism  38  may be utilized to indicate the depth to which the long thin member  202  is moved into the patient&#39;s body. By comparing the depth of the thin member  202  in the patient&#39;s body with the depth to which the gripper member  232  is moved into the patient&#39;s body, the thickness of the body tissue  64  can be determined. This enables the robotic mechanism  38  to move the inserter member  102  to a position in engagement with the upper surface  134  of the layer  116  of body tissue  64 . It also enables the robotic mechanism  38  to be operated to move the pusher member  108  through a distance sufficient to push the anchor  60  through both the upper layer  116  of body tissue and the lower layer  118  of body tissue to the position corresponding to the position illustrated in  FIG. 3 . If desired, the anchor  60  may be moved to a position in the lower layer  118  of body tissue. 
         [0152]    When the tissue positioning assembly  200 , inserter member  102 , and pusher member  108  are to be manually moved relative to the body tissue  64 , indicia to indicate the depth of movement of the various members may be provided on the outside of various members. The indicia may be numerical indicia indicating the depth of insertion of a member into the body tissue. Alternatively, the indicia may be colored bands or other markings. If the indica is to be colored bands, the indicia may be similar to the indicia disclosed in U.S. Pat. No. 6,056,772. 
         [0153]    Once the anchor  60  ( FIG. 12 ) has been moved through layers  116  and  118  of the body tissue  64  while the tissue positioning assembly  200  grips the body tissue and holds it into a desired position, the suture  66  is tensioned with a predetermined force and a retainer is deformed to grip the suture. The retainer may have the same construction as the retainer  72  of  FIG. 4 . Alternatively, the suture retainer may have any one of the constructions disclosed in U.S. Pat. No. 6,159,234. 
         [0154]    A retainer deformation assembly having the same construction as the retainer deformation assembly  144  ( FIG. 4 ) may be utilized to deform the retainer to grip the suture  66  of  FIG. 12 . This results in the body tissue  64  being clamped or gripped between the anchor  60  and a retainer  72  which grips the suture  66 . This holding or gripping action would be the same as was previously described in conjunction with  FIGS. 2-4  herein. Of course, other known retainer deformation assemblies could be utilized if desired, as noted above. 
         [0155]    Once the body tissue has been gripped between the anchor  60  and the retainer  72  and the retainer secured to the suture  66 , the tissue positioning assembly  200  is disengaged from the body tissue as noted above. 
         [0156]    It is contemplated that the leading end portion  204  of the long thin member  202  may include a resilient panel  240  ( FIG. 13 ). The panel  240  is moved from a contracted condition, shown in dashed lines in  FIG. 13 , to the expanded condition of  FIGS. 10, 11, 12 and 13  with fluid pressure. When the leading end portion  204  of the long thin member  202  is in the contracted condition of  FIG. 9 , the resilient panel collapses radially inward from the expanded condition to the contracted condition under the influence of its own natural resilience. When the panel  240  is in the contracted condition, a cylindrical outer side surface of the resilient panel  240  is aligned with a cylindrical outer side surface  244  of the long thin member  202 . At this time, the resilient panel  240  is disposed in an annular recess  246  formed in the leading end portion  204  of the long thin member  202 . 
         [0157]    When the leading end portion  204  of the long thin member  202  is to be expanded, fluid under pressure is conducted through a passage  250  in the long thin member to the annular recess  246  in the leading end portion of the long thin member. This fluid pressure is applied against an inner side surface of the resilient panel  240 . The fluid pressure forces the resilient panel  240  to expand outward to the annular configuration illustrated in solid lines in  FIG. 13 . The fluid pressure applied against the inner side of the panel  240  could be either a liquid or gas pressure. Thus, the robotic mechanism  38  is operable force either a gas or a liquid through the passage  250 . 
         [0158]    When relatively large forces are to be transmitted from the leading end portion  204  of the long thin member  202  to the body tissue  64 , it may be preferred to utilize a liquid to effect radial expansion of the panel  240 . When somewhat smaller forces are to be transmitted from the long thin member  202  to the body tissue  64 , the resilient panel  240  may be expanded under the influence of gas pressure. 
         [0159]    The long thin member  202  has a pointed end  254  which is utilized to pierce imperforate areas on upper and lower surfaces of the upper layer  116  of body tissue and on upper and lower surfaces of the lower layer  118  of body tissue. The pointed end  254  of the long thin member  202  is coaxial with the longitudinal central axis of the long thin member and has a conical configuration. The pointed end  254  of the long thin member  202  is immediately ahead of and coaxial with the resilient panel  240 . 
         [0160]    The resilient panel on the leading end portion  204  of the long thin member may be formed of any desired resilient material which can be expanded under the influence of fluid pressure. It is contemplated that the resilient panel  240  will be formed of a polymeric material. The remainder of the long thin member  202  may be formed of either metal or a polymeric material. 
         [0161]    An alternative embodiment of the long thin member  202  is illustrated in  FIG. 14 . In this embodiment, the resilient panel  240  is formed as a portion of a circle. This results in the resilient panel bulging outward from one side of the long thin member  202  when fluid pressure is connected through the passage  250  to a recess  246  in the leading end portion  204  of the long thin member  202 . The recess  246  has a configuration corresponding to a portion of a cylinder. 
         [0162]    When the leading end portion  204  is in the contracted condition, the resilient panel  240  is disposed in the position indicated in dash lines in  FIG. 14 . At this time, the resilient panel  240  is disposed within the recess  246 . When fluid pressure is conducted through the passage  250  to the recess  246 , the resilient panel  240  is expanded radially outward from the long thin member  202  to the position shown in solid lines in  FIG. 14 . Other than the configuration of the resilient panel  240 , the long thin member  202  of  FIG. 14  has the same construction as the long thin member  202  of  FIG. 13 . 
         [0163]    In the embodiment of the long thin member  202  illustrated in  FIG. 15 , a plurality of longitudinally extending elements  260  are disposed in a cylindrical array on the leading end portion  204  of the long thin member  202 . The longitudinally extending elements  260  are spaced apart from each other and have longitudinal central axes extending parallel to a longitudinal central axis of the long thin member  202 . The longitudinally extending elements  260  are pivotally connected at  264  to a cylindrical main portion  266  of the long thin member  202 . A pointed end  254  of the long thin member  202  is connected with a cylindrical actuator rod  268  which extends through the main portion  266  of the long thin member to the pointed end  254 . By pulling upwards (as viewed in  FIG. 15 ) on the long thin member, the longitudinally extending elements  260  are bent at central pivots  272 . The long thin elements are connected with the pointed end  254  at pivots  274 . 
         [0164]    Pulling upward, in the manner indicated by an arrow  276  in  FIG. 15  transmits force through the actuator rod  268  to the pointed end  254  of the long thin member  202 . This moves the pointed end  254  of the long thin member toward the main portion  266  of the long thin member. As this occurs, the longitudinally extending elements  260  are bent at the pivot connections  264 ,  272  and  274  and move radially outward away from a longitudinal central axis of the long thin member  202 . This results in the longitudinally extending elements performing an annular projection which extends around the long thin member  202 . This annular projection is pressed against body tissue by pulling upward on the main portion  266  of the long thin member  202 . 
         [0165]    The longitudinally extending elements  260  of  FIG. 15  are formed separately from the main portion  266  of the long thin member  202 . However, the longitudinally extending elements  260  may be integrally formed as one piece with the main portion  266  of the long thin member  202 . If this was done, the longitudinally extending elements  260  would be resiliently deflected radially outward from the contracted condition to the expanded condition. This may be accomplished in the manner disclosed in U.S. Pat. No. 5,667,520. 
         [0166]    Although the long thin member  202  has been illustrated in  FIGS. 9-12  in association with layers  116  and  118  of soft body tissue  64 , it is contemplated that the long thin member  202  could be utilized with hard body tissue if desired. For example, the pointed leading end  254  of the long thin member  202  could be forced through a hard cortical outer layer of a portion of a bone in a patient&#39;s body. Alternatively, the leading end portion  204  could be moved into the bone through a drilled passage. 
         [0167]    The leading end portion  204  of the long thin member  202  would then be expanded in the bone, under the influence of fluid pressure and/or force transmitted through the long thin member. Expansion of the leading end portion  204  of the long thin member  202  would deflect the relatively soft consellous bone enclosed by the hard cortical outer layer of bone. This would result in the long thin member being secured with the bone. 
         [0168]    After the leading end portion  204  of the long thin member  202  has been expanded in a bone, the gripper member  232  ( FIG. 12 ) may be moved axially along the long thin member  202  to press soft body tissue, such as the layer  116  of soft body tissue, against the bone. This would result in the soft body tissue and the hard cortical outer layer of the bone being gripped between the leading end portion  204  of the long thin member  202  and the gripper member  232  in the same manner as in which the layers  116  and  118  of soft body tissue are clamped between the gripper member  232  and the expanded leading end portion  204  of the long thin member  202  in  FIG. 12 . 
         [0169]    In the embodiment illustrated in  FIGS. 9-12 , the leading end portion  204  of the long thin member  202  is moved through the body tissue and is effective to apply force against an outer surface  132  of the lower layer  118  of body tissue. However, it is contemplated that the long thin member may be moved only part way through the layer  118  of body tissue. This would result in the leading end portion  204  of the long thin member being operated from the contracted condition of  FIG. 9  to the expanded condition of  FIGS. 11 and 12  while the leading end portion of the long thin member is disposed in the layer  118  of body tissue. As the leading end portion  204  of the long thin member is expanded in the layer  118  of body tissue, the outer side surface of the resilient panel  240  applies force against the soft tissue of the layer  118  to move the tissue sufficiently to accommodate expansion of the leading end portion  204  of the long thin member  202 . 
         [0170]    When the tissue positioning assembly  200  is to be used in association with a fractured bone or bone fragments, the long thin member  202  is moved through portions of the bone while the leading end portion  204  of the long thin member is in the contracted condition. Once the leading end portion  204  of the long thin member  202  has moved through portions of the bone separated by a fracture or break, the leading end portion of the long thin member may be expanded. The expanded leading end portion  204  of the long thin member  202  would engage an outer surface of a portion of a bone in the same manner as in which the expanded leading end portion engages an outer surface of the tissue layer  118  in  FIGS. 10-12 . 
         [0171]    A gripper member, corresponding to the gripper member  232  of  FIG. 12 , is then moved axially along the long thin member  202  to press the portion of the bone disposed on one side of the fracture against a portion of the bone disposed on the opposite side of the fracture. In this instance, the leading end portion  204  of the long thin member  202  is expanded at a location outside of the bone. However, in other situations, it may be advantageous to expand the leading end portion  204  of the long thin member  202  in the bone. The relatively soft cancellous bone can be deflected by expansion of the leading end portion  204  of the long thin member  202  in a bone. 
         [0172]    In the embodiment of the tissue positioning assembly  200  illustrated in  FIGS. 16-19 , the long thin member  202  has a leading end portion  204  with an external thread convolution  278 . When the long thin member  202  is rotated about its longitudinal central axis, the external thread convolution  278  engages body tissue. This enables force to be transmitted from the long thin member  202  to the body tissue engaged by the external thread convolution  278 . The body tissue  64  can then be moved to and held in a desired position in a patient&#39;s body. 
         [0173]    When the tissue positioning assembly  200  is to be utilized to position the layers  116  and  118  of the body tissue  64  relative to each other, the long thin member  202  is extended through the upper (as viewed in  FIG. 16 ) layer  116  of body tissue. This may be done by forcing the long thin member  202  to move axially through the layer  116  of body tissue with a piercing action. Alternatively, the long thin member  202  may be rotated about its longitudinal central axis. As the long thin member  202  is rotated, force is transmitted between the body tissue  116  and the external thread convolution  278 . This force is effective to pull the long thin member  202  through the body tissue  116 . In order to minimize damage to the body tissue  116 , the long thin member  202  should rotate about its longitudinal central axis so that the external thread convolution  278  engages the body tissue  116  and is effective to pull the long thin member  202  through the body tissue. 
         [0174]    Once the long thin member  202  ( FIG. 16 ) has moved through the upper layer  116  of body tissue, the external thread convolution  278  on the leading end portion  204  of the long thin member  202  moves into engagement with an upper side surface of the layer  118  of body tissue. When this happens, the long thin member  202  is again rotated about its longitudinal central axis. This causes the external thread convolution  278  to engage the lower layer  118  of body tissue with a screw action. The screw action between the thread convolution  278  and lower layer  118  of body tissue is effective to pull the long thin member  202  into the lower layer  118  body tissue. When the external thread convolution  278  has been screwed into the lower layer  118  of body tissue to a desired depth, rotation of the long thin member  202  about its longitudinal central axis is interrupted. 
         [0175]    In order to close a space  208  between the upper layer  116  and the lower layer  118  body tissue  64 , the long thin member is pulled upward as indicated by the arrow  212  in  FIG. 17 . The upward force  212  applied to the long thin member is transmitted through the external thread convolution  278  to the lower layer  118  of body tissue. This pulls the lower layer  118  of body tissue upwards (as viewed in  FIGS. 16 and 17 ) into engagement with the upper layer  116  of body tissue. If desired, the gripper member  232  ( FIG. 12 ) may be used with the long thin member  202  of  FIGS. 17 and 18  to grip body tissue in the manner previously explained. 
         [0176]    Once the two layers  116  and  118  of body tissue have been moved to a desired position in the patient&#39;s body by the tissue positioning assembly  200 , the anchor  60  ( FIG. 18 ) may be moved into the body tissues  116  and  118  by the robotic mechanism  38  in the same manner as previously discussed in conjunction with  FIGS. 2 and 3 . Thus, the inserter member  102  may be moved into engagement with the upper layer  116  of body tissue. The pusher member  108  then applies force against the anchor  60  to push the anchor through the lower layer  116  of body tissue and into the lower layer  118  of body tissue. As was previously mentioned, the anchor  60  may be pushed through the lower layer  118  of body tissue or have its movement into the lower layer interrupted when it is midway between upper and lower side surfaces of the lower layer  118  of body tissue. 
         [0177]    While the anchor  60  is being pushed into the body tissue  116  and the body tissue  118 , an upwards force  212  is transmitted from the long thin member  202  through the external thread convolution  278  to the lower layer  118  of body tissue. This force holds the lower layer of body tissue in engagement with the upper layer  116  of body tissue in the manner illustrated schematically in  FIG. 18 . 
         [0178]    It is contemplated that the long thin member  202  may be utilized as part of a fastener to interconnect the two layers  116  and  118  of body tissue in the manner illustrated schematically in  FIG. 19 . When this is to be done, a retainer  72  is positioned along the long thin member  202  with the long thin member extending through the retainer ( FIG. 19 ). The retainer pusher member  126  is then effective to press the retainer  72  against the upper layer  116  of body tissue. 
         [0179]    The retainer deformation assembly  144  can then be utilized to deform the retainer  72  in the manner previously discussed in conjunction with  FIG. 4 . As force is applied against the retainer  72  by the force transmitting members  80  and  82 , the retainer  72  is deformed and grips the long thin member  202  to establish an interconnection between the retainer and the long thin member. This interconnection results in force being transmitted through the long thin member  202  between the external thread convolution  278  which engages the lower layer  118  of body tissue and the retainer  72  which engages the upper layer  116  of body tissue. After the retainer  72  has gripped the long thin member  202 , the retainer pusher member  126  and retainer deformation assembly  144  are removed from the patient&#39;s body. This results in the long thin member  202  and the retainer  72  functioning as a fastener to interconnect the two layers  116  and  118  of body tissue. 
         [0180]    The long thin member  202 , the external thread convolution  278 , and the retainer  72  may be formed of either biodegradable or non-biodegradable material. When the long thin member  202 , external thread convolution  278  and retainer  72  are formed of biodegradable material, they will degrade and be absorbed by the patient&#39;s body with passage of time. However, when the long thin member  202 , external thread convolution, and retainer  72  are formed of non-biodegradable material, they are effective to maintain the two layers  116  and  118  of body tissue in engagement with each other, in the manner illustrated in  FIG. 19 , for a long period of time. 
         [0181]    The long thin member  202  and external thread convolution  278  are illustrated in  FIG. 19  in association with soft body tissue. However, it is contemplated that the long thin member  202  and external thread convolution may be utilized in association with hard body tissue, such as bone. When this is to be done, the external thread convolution  278  of the long thin member  202  may be screwed into the bone. Alternatively, the long thin member  202  and external thread convolution  278  may be moved through a passage drilled in the bone and into a layer of soft tissue. This would enable force to be transmitted from the external thread convolution  278  to the layer of soft tissue to pull the layer of soft tissue into engagement with the bone. 
         [0182]    It is believed that it may be particularly advantageous to utilize the external thread convolution  278  in association with the long thin member  202  when pieces of bone are to be positioned relative to each other. Thus, the long thin member  202  may be moved through a passage drilled or formed in another manner, in one piece of bone and the external thread convolution moved into engagement with a second piece of bone. The long thin member  202  would then be rotated about its central axis to screw the external thread convolution  278  into the second piece of bone. Force applied to the long thin member  202  could then be utilized to pull the second piece of bone into engagement with the first piece of bone. 
         [0183]    It is also contemplated that the long thin member  202  and external thread convolution  278  may be advantageously utilized to close a fracture or break in a bone. This is because the thread convolution  278  may engage one portion of the bone to enable it to be pulled into engagement with another portion of the bone. Once the two portions of the bone have been pulled into engagement with each other, they may be interconnected in the manner disclosed in U.S. Pat. No. 6,117,160. Alternatively, they may be interconnected by securing a retainer  72  to the long thin member  202  in the manner previously discussed herein. 
         [0000]    Securing with Suture and Retainer 
         [0184]    In the embodiments of the invention illustrated in  FIGS. 2-8  the suture  66  extends in a straight line between an anchor  60  and a retainer  72  or in a straight line between two retainers. However, under certain circumstances at least, it may be desired to form the suture  66  into a loop which extends through body tissue  64  in the manner illustrated in  FIG. 20 . 
         [0185]    The suture  66  is sewn through the two layers  116  and  118  of body tissue using a needle or other known device. The suture is moved through the body tissue  64  by the robotic mechanism  38 . It is contemplated that the magnetic suturing system and method disclosed in the aforementioned U.S. patent application Ser. No. 10/005,652, will be used by the robotic mechanism  38 . Alternatively, the needle could be manually moved through the two layers  116  and  118  of body tissue  64 . 
         [0186]    The suture  66  has a connector section  280  ( FIG. 20 ) which extends between a pair of a leg sections  282  and  284 . The leg sections  282  and  284  extend through the layers  116  and  118  of tissue  64  to the retainer  72 . The leg sections  282  and  284  extend through the retainer  72  and are tensioned by a tensioner  122  which applies a predetermined force  70  to the two leg sections  282  and  284  of the suture  66 . 
         [0187]    While the suture  66  is being tensioned with the predetermined force  70 , the retainer  72  is pressed against the body tissue  64  by the retainer pusher member  126 . The retainer pusher member  126  is pressed against the retainer  72  by the pusher drive assembly  128 . The pusher drive assembly  128  causes the retainer pusher member  126  to press the retainer  72  against the body tissue  64  with a predetermined force indicated at  74  in  FIG. 16 . This results in the retainer member  72  being pressed against the body tissue  64  with a predetermined force while the leg sections  282  and  284  and connector section  280  of the suture  66  are tensioned with a predetermined force. 
         [0188]    While the retainer  72  is pressed against the body tissue, the retainer deformation assembly  144  deforms a retainer  72  to grip the two leg sections  282  and  284  of the suture  66 . Thus, the outer member  156  is moved axially downward, as viewed in  FIG. 20 , to move the force transmitting members  80  and  82  radially inward toward the spherical retainer  72 . The force applied to the retainer  72  by the force transmitting members  80  and  82  deforms the retainer so that it grips the sutures  66 . As was previously explained, the force transmitting members  80  and  82  may be utilized to cause a cold flow of the material of the retainer  72  to grip the two legs  282  and  284  of the suture  66 . Alternatively, ultrasonic vibratory energy from a source  90  may be transmitted to the force transmitting member  82  and the retainer  72  to heat the retainer. 
         [0189]    Although the retainer has been illustrated in  FIG. 16  as having a spherical configuration, it is contemplated that the retainer  72  could have a different configuration if desired. For example, the retainer  72  could have any one of the configurations disclosed in U.S. Pat. No. 6,159,234. The manner in which the retainer  72  is plastically deformed to grip the two legs  282  and  284  of the suture  66  may also be the same as is disclosed in the aforementioned U.S. Pat. No. 6,159,234. Alternatively, the retainer  72  may be heated and then deformed in the manner disclosed in the aforementioned U.S. patent application Ser. No. 09/524,397 or in U.S. Pat. No. 6,203,565. 
         [0190]    In order to facilitate positioning of the suture  66  ( FIG. 20 ) relative to the body tissue  64 , iron particles may be embedded in the suture throughout the length of the suture. To move the suture  66  to a desired position in the patient&#39;s body, a magnet is positioned close enough to the suture  66  to attract the iron particles in the suture. The magnet is then moved relative to the body tissue to move the suture  66  relative to the body tissue. The magnet may be positioned inside the patient&#39;s body or outside the patient&#39;s body. The magnet may be electromagnet or a permanent magnet. 
         [0191]    Similarly, iron particles may be embedded in the suture retainer  72 . To move the suture retainer  72  to a desired position in the patient&#39;s body, a magnet is positioned close enough to the retainer to attract the iron particles in the retainer. The magnet is then moved relative to the body tissue to move the suture retainer  72  relative to the body tissue. The magnet may be positioned inside the patient&#39;s body or outside the patient&#39;s body. The magnet may be an electromagnet or a permanent magnet. 
         [0192]    When iron particles are to be provided in the suture  66  and/or retainer  72 , the suture and/or retainer may advantageously be formed of a biodegradable material. As the biodegradable material of the suture  66  and/or retainer  72  degrades in the patient&#39;s body, the iron particles also degrade. The iron particles are subsequently absorbed by the patient&#39;s body. 
       Staple—Bonded 
     Leg Ends 
       [0193]    In the embodiments of the invention illustrated in  FIGS. 2-8 , the robotic mechanism  38  is utilized to secure body tissue with a suture  66 . However, it is contemplated that a staple  300  ( FIGS. 21 and 22 ) may be utilized to secure the body tissue  64 . When the staple  300  is utilized to secure the body tissue, end portions  302  and  304  of legs  306  of the staple are moved into engagement ( FIG. 22 ) and bonded together. By bonding the end portions  302  and  304  of the legs  306  and  308  of the staple  300  together, the staple is locked into the tissue  64 . Any tendency for the resilient legs  306  and  308  to spring back to their original positions ( FIG. 21 ) is prevented by the interconnected the end portions  302  and  304  of the legs. 
         [0194]    When the upper and lower layers  116  and  118  of the body tissue  64  are to be interconnected, the long thin member  202  ( FIGS. 9-12 ) is inserted through the layers  116  and  118  of body tissue. The leading end portion  204  of the long thin member  202  is then expanded. The gripper member  232  ( FIG. 12 ) may then be moved along the long thin member  202  to clamp the layers  116  and  118  of body tissue as illustrated in  FIG. 12 . It is preferable to clamp the layers  116  and  118  of body tissue, but use of the gripper member may be eliminated. If desired, use of the entire tissue positioning assembly  200  could be eliminated. 
         [0195]    Once the layers  116  and  118  of body tissue  64  have been gripped as illustrated schematically in  FIG. 12 , the two layers  116  and  118  of body tissue are moved to a desired position in the patient&#39;s body and are held there by the tissue positioning assembly  200 . The robotic mechanism  38  is then operated to move the staple  300  to a desired position relative to the body tissue  64  ( FIG. 21 ). At this time, the legs  306  and  308  of the staple  300  are in their initial or relaxed condition illustrated in  FIG. 21 . The end portions  302  and  304  of the staple legs are spaced apart. This enables the staple  300  to be moved by the robotic mechanism  38  to a position in which body tissue  64  is disposed between the end portions  302  and  304  of the staple legs  306  and  308  ( FIG. 21 ). 
         [0196]    Force transmitting members  312  and  314  ( FIG. 21 ) are then moved by the robotic mechanism  38  to deflect the staple legs  306  and  308 . The staple legs  306  and  308  are deflected from their initial or unrestrained positioned illustrated in  FIG. 21  to a bent or deflected position, illustrated in  FIG. 22 . As the staple legs  306  and  308  are bent under the influence of force applied against the legs by the force transmitting members  312  and  314 , the end portions  302  and  304  of the legs move into engagement ( FIG. 22 ) in the body tissue  64 . Although the force transmitting members  312  and  314  are moved by the robotic mechanism  38 , it is contemplated that the force transmitting members  312  and  314  could be moved manually if desired. 
         [0197]    While the end portions  302  and  304  of the staple legs  306  and  308  are pressed together, ultrasonic vibratory energy is transmitted to the staple  300  to effect the heating of the end portions  302  and  304  of the staple legs  306  and  308  and a bonding of the staple legs together. To this end, ultrasonic vibratory energy is transmitted from the force transmitting member  312  to the staple legs  306  and  308 . This results in the force transmitting member  312  functioning as a horn for ultrasonic vibratory energy. The force transmitting member  314  functions as an anvil. 
         [0198]    The apparatus for transmitting ultrasonic vibratory energy to the staple legs  306  and  308  may have a construction and mode of operation which is similar to the construction and mode of operation of the apparatus disclosed in U.S. Pat. Nos. 5,836,897 and 5,906,625 and in U.S. patent application Ser. No. 09/524,397. However, it should be understood that the staple legs  306  and  308  could be heated with devices other than sources of ultrasonic vibratory energy. For example, a laser and/or resistance wire could be used to heat the staple legs  306  and  308 . 
         [0199]    The staple  300  is formed of a biodegradable polymeric material. However, staple  300  may be formed of any one of many different type of materials, including polymers of lactic acid, lactides, l-lactides, and isomers of lactic acids and/or lactides. Although it is believed that it may be desired to form the staple  300  of polycaperlactone, other known biodegradable or non-biodegradable polymers may be utilized to form the staple  300 . 
         [0200]    To effect a bonding of the end portions  302  and  304  of the staple legs  306  and  308  together, the material of the end portions of the staple legs is heated to a temperature in its transition temperature range by the application of ultrasonic vibratory energy to the end portions  302  and  304  of the staple legs  306  and  308 . This results in the polymeric material of the end portions  302  and  304  of the staple legs  306  and  308  changing from a rigid solid condition in which it has a fixed form to a soft or viscous condition. The material of the staple legs  306  and  308  adjacent to the end portions  302  and  304  is not heated into its transition temperature range and maintains its original configuration. 
         [0201]    After the material the end portions  302  and  304  of the staple leg  306  and  308  has been heated into the transition temperature range and has a soft moldable condition, the material moves under the influence of the force applied against the staple legs  306  and  308  by the force transmitting members  312  and  314 . The heated material of the staple legs  306  and  308  molds itself together and blends at the end portions  302  and  304  of the suture legs  306  and  308 . The staple leg end portions  302  and  304  are cooled to a temperature below the transition temperature range of the material of the staple  300  and a secure bond is obtained between the polymeric material of the end portion  302  and the end portion  304  of the staple legs. This secure bond prevents a springing back of the resilient staple legs  306  and  308  toward their initial positions ( FIG. 21 ) relative to each other. Therefore, a portion of the body tissue  64  is gripped between the end portions  302  and  304  of the staple legs  306  and  308  and a connector or bight portion  318  of the staple  300  ( FIG. 22 ). The grip obtained by the staple  300  on the body tissue  64  holds the layers  116  and  118  in secure engagement with each other. 
         [0202]    Although only a single staple  300  has been illustrated in  FIG. 21  a linear array of staples is provided along the ends of the side-by-side layers  116  and  118  of body tissue  64 . This results in linear apposition of the layers  116  and  118  of body tissue  64 . The two layers  116  and  118  are interconnected in a side-by-side relationship by a plurality of staples in much the same manner as in which the layers  116  and  118  of body tissue are interconnected in  FIG. 5 . 
         [0203]    One or more of the staples  300  and/or the anchors  60 , sutures  66  and retainers  72  may be used for purposes other than the interconnecting of layers  116  and  118  of body tissue. They may be used in association with the repair of cartilage, pancreas, kidney, a stomach, a colon, etc. They may also be utilized in open or endoscopic surgery and may be applied by a robotic mechanism, similar to the robotic mechanism  38 , or may be manually applied. Additionally, they may be utilized for many different purposes, including rotator cuff repair, meniscus repair, the attachment of soft tissue, such as a ligament or tendon to bone, interconnection of various soft tissues to each other, and interconnections of portions of bone, or with many different types of surgical implants, such as a prosthesis in a patient&#39;s body. 
         [0204]    In the embodiment of  FIGS. 21 and 22 , the staple  300  forms a loop which extends around a portion of the body tissue disposed between the end portions  302  and  304  of the staple legs  306  and  308  and the connector or bight portion  318  of the staple ( FIG. 22 ). However, it is contemplated that the staple  300  may be embedded in body tissue at a location spaced from edge portions of the body tissue. For example, the staple may be utilized to connect a layer of body tissue or other material with a relatively large portion of body tissue which forms an organ or gland or muscle in a patient&#39;s body, such as a pancreas or kidney. The staple  300  ( FIGS. 21 and 22 ) and/or suture connections of  FIGS. 5, 6 and 8  may be utilized in association with components of a patient&#39;s body cardiovascular system including the heart and/or blood vessels. 
         [0205]    The tissue positioning assembly  200  of  FIGS. 9-19  may be utilized to position body tissue at any location where a staple  300  or suture connection of  FIG. 5  is utilized. It should be understood that the components of the tissue positioning assembly  200  will vary depending upon the location where the staple or suture connection is to be positioned. Thus, the tissue positioning assembly  200  may include only the long thin member  202 . Alternatively, the tissue positioning assembly  200  may include both the long thin member  202  and the gripper member  232  ( FIG. 12 ). The leading end portion  204  of the long thin member  202  may be expanded at a location where expansion of the end portion  204  deflects body tissue. Alternatively, the leading end portion  204  of the long thin member  202  may be expanded at a location where the expansion does not deflect body tissue ( FIG. 10 ). It is believed that the tissue positioning assembly  200  will be particularly advantageous in holding body tissue during the application of a staple  300  or a suture connection. However, the tissue positioning assembly  200  may be used during many other surgical procedures on many different types of body tissue. 
       Staple—Bonded 
     Leg Sides 
       [0206]    The sides of legs of a staple  330  ( FIGS. 23-26 ) are bonded together to hold the staple in the closed condition of  FIG. 26 . The staple  330  is formed of a polymeric material which may be either biodegradable or nonbiodegradable. 
         [0207]    When the staple  330  ( FIG. 23 ) is to be embedded into body tissue, the robotic mechanism  38  moves a staple mechanism  332  to a desired position relative to body tissue  334  ( FIG. 24 ). The robotic mechanism  38  urges the staple mechanism toward the body tissue  334  with a predetermined force. When the staple mechanism  300  has been moved to the desired position relative to the body tissue  334 , a pusher plate  338  is advanced or lowered from the position show in  FIG. 23  through the position show in  FIG. 24  to the position shown in  FIG. 25 . As the pusher plate  338  is lowered or advanced to the position shown in  FIG. 25 , legs  342  and  344  of the staple  330  are moved from a position spaced from the body tissue  334  ( FIG. 24 ) to a position in which the legs extend into the body tissue ( FIG. 25 ). 
         [0208]    The staple  330  enters the body tissue  334 , a connector or bight portion  346  of the staple  330  moves into engagement with a pair of anvils  350  and  352  ( FIGS. 23-25 ). The anvils  350  and  352  are integrally formed with an anvil plate  354  ( FIG. 23 ) disposed in the stapling mechanism  332 . At this time, the legs  342  and  344  of the staple  330  extend into the body tissue  334  ( FIG. 25 ). However, the legs  342  and  344  extend in a generally perpendicular relationship with the connector or bight portion  346  of the staple  330  and do not engage each other. Although there is some gripping action between the legs  342  and  344  of the staple  330  and the body tissue  334  at this time ( FIG. 25 ), the staple  330  is not secured in the body tissue. 
         [0209]    Continued downward movement of the pusher plate  338  causes force transmitting members or lands  356  and  358  connected to the pusher plate  338  to press against the connector or bight portion  346  of the staple  330  ( FIG. 25 ). As the pusher plate  338  continues to be advanced or lowered to the position shown in  FIG. 26 , the lands or force transmitting members  356  and  358  deflect or bend the legs  342  and  344  to the gripping position illustrated in  FIG. 26 , to dispose a portion of the body tissue  334  between the legs  342  and  344  and the connector or bight portion  346  of the staple  330  ( FIG. 26 ). 
         [0210]    Longitudinally extending side surfaces of the staple legs  342  and  344  are disposed in engagement with each other when the staple  330  is in the bent or deflected condition of  FIG. 26 . The longitudinally extending side surfaces on the staple legs  342  and  344  engage at a location where the staple legs cross beneath (as viewed in  FIG. 26 ) the connector or bight portion  346  of the staple. 
         [0211]    Once the staple  330  has been bent or deformed to grip the body tissue  334  in the manner illustrated schematically in  FIG. 26 , the legs  342  and  344  of the staple are bonded together. The location where the end portions of the legs  342  and  344  cross and engage each other. To effect a bonding of the legs  342  and  344  to each other, the polymeric material of the staple  330  is heated into its transition temperature range at the location where the end portions of the legs  342  and  344  of the staple legs are disposed in engagement. 
         [0212]    To effect a heating of the legs  342  and  344  of the staple, ultrasonic vibratory energy is transmitted from the land or force transmitting member  356  to the staple  330 . As this is done, the land or force transmitting member  356  functions as a horn for ultrasonic vibratory energy. The opposite land or force transmitting member  358  functions as an anvil of the ultrasonic vibratory energy application system. The ultrasonic vibratory energy application system may have a construction similar to the construction disclosed in the aforementioned U.S. Pat. Nos. 5,836,897 and 5,906,625 or in U.S. patent application Ser. No. 09/524,397. It should be understood that other known devices could be used to heat the staple  330 . Thus, an electrical resistance wire heater or a laser could be used to heat the staple  330 . 
         [0213]    The staple  330  is formed of a polymeric material. The ultrasonic vibratory energy transmitted to the staple  330  from the force transmitting member  356  is effective to heat the polymeric material of the staple legs  342  and  344  into a transition temperature range for the material. When the material of the staple legs  342  and  344  is cooled, a bond is formed between the staple legs in the same manner as previously explained in conjunction with the staple  300  of  FIGS. 21 and 22 . 
         [0214]    Once the legs  342  and  344  of the staple have been bonded together, the staple is released or disengaged from the anvils  350  and  352  by an injector spring  362  having legs  364  and  366  ( FIG. 23 ) which are pressed against the staple  330 . This force separates the staple from the anvils  350  and  352 . 
         [0215]    It is contemplated that the staple mechanism  332  may have any one of many known constructions. It is also contemplated that the staple  330  could have a configuration other than the configuration illustrated in  FIGS. 23-26 . For example, the staple  330  could have a construction somewhat similar to the construction of the staple  300  of  FIG. 21 . 
         [0216]    The stapling mechanism  332  has a general construction and mode of operation which is similar is to the construction and mode of operation of a known stapling mechanism disclosed in U.S. Pat. No. 5,289,963. However, this known stapling mechanism does not bond the legs of a staple together. By bonding the legs  342  and  344  of the staple  330  together, a resilient springing back of the legs toward their initial positions and a resulting release of the body tissue  334  is prevented. 
         [0217]    The staple  330  ( FIGS. 23-26 ) is advantageously formed of a biodegradable polymeric material, such as polycaperlatone. Staple  330  may also be formed of any one of many known biodegradable materials, including polymers or co-polymers of lactic acid, lactides, l-lactides, and isomers of lactic acids and/or lactides. Of course, the staple  330  may be formed of many different known biodegradable materials. If desired, the staple  330  may be formed of a material which is not biodegradable. 
         [0218]    The staple  330  will be utilized for tissue repair within a patient&#39;s body and in the locations on the surface of the patient&#39;s body. Regardless of whether the stapling mechanism  332  is used to staple outside of a patient&#39;s body or within the patient&#39;s body, the stapling mechanism may advantageously be utilized as part of the robotic mechanism  38  of  FIG. 1 . However, it should be understood that the stapling mechanism  332  could be manually actuated rather than be robotically actuated if desired. 
         [0219]    The stapling mechanism  332  is illustrated in  FIGS. 24-26  as connecting a flexible surgical mesh  380  with the body tissue  334 . The robotic mechanism  38  may be used to position the surgical mesh  380  in the patient&#39;s body. Movement of the surgical mesh  380  through the limited incision  52  by the robotic mechanism  38  may be facilitated by moving the mesh into the patient&#39;s body in a rolled up condition. The robotic mechanism  38  would then be operated to unroll the surgical mesh  380  in the patient&#39;s body and position the surgical mesh relative to the body tissue  334 . 
         [0220]    Although only a single staple  330  is illustrated in  FIGS. 24-26 , a plurality of staples  330  are utilized to connect the surgical mesh  380  with the body tissue  334 . In addition to staples  330 , suture anchors  60 , sutures  66  and retainers  72  ( FIG. 5 ) may be utilized to connect the surgical mesh  380  with the body tissue  334  in the manner previously described in conjunction with  FIGS. 2-4 . Both staples and suture connections may be utilized to connect the mesh  380  with the body tissue  334 . Alternatively, only staples or only suture connections may be used to connect the surgical mesh  380  with the body tissue  334 . 
       Implant of Viable Tissue Components 
       [0221]    Rather than using the staple  330  to connect the surgical mesh  380  with the body tissue  334 , the staple  330  may be used to connect a scaffold or framework  382  ( FIGS. 27-29 ) with the body tissue  334 . The scaffold  382  provides a non-living three dimensional matrix or supporting framework on which viable body tissue components  384  ( FIGS. 27 and 28 ) are disposed. The three dimensional framework or scaffold  382  may be formed of either biodegradable or a non-biodegradable material. 
         [0222]    When the scaffold or framework  382  is formed of a non-biodegradable material, body tissue will grow through the scaffold or framework so that the scaffold becomes embedded in new tissue growth. When the scaffold or framework  382  is formed of a biodegradable material, the scaffold will eventually degrade and be absorbed by body tissue. The scaffold  382  may have fibers of biodegradable material randomly arranged in the manner illustrated schematically in  FIG. 27  to form a supporting framework. Alternatively, the scaffold or framework  382  may have biodegradable fibers arranged in an ordered relationship similar to the relationship illustrated schematically in  FIG. 28 . 
         [0223]    It is contemplated that the scaffold or framework  382  may have either a flexible or rigid construction. The scaffold  382  could be formed of a biodegradable material such as polyglycolic acid or polylactic acid. If desired, the scaffold or framework  382  could be formed of fibrous connective materials such as portions of body tissue obtained from human and/or animal sources. The scaffold or framework  382  may be formed of collagen or submucosal tissue. 
         [0224]    The scaffold or matrix  382  forms a supporting framework for tissue inductive factors and viable tissue components  384 . The viable tissue components  384  may be mesenchymal cells which are introduced into the scaffold or framework in the operating room. Thus, the matrix or scaffold  382  may be constructed at a location remote from an operating room. After the scaffold  382  has been transported to the operating room, the viable tissue components  384 , such as mesenchymal cells, may be introduced into the scaffold. 
         [0225]    It is contemplated that the matrix or scaffold  382  may contain viable tissue components  384  which include stem cells and/or fetal cells. The stem cells and/or fetal cells may be introduced into the matrix or scaffold  382  in the operating room. It is contemplated that tissue growth inductive factors may be provided in the matrix or scaffold  382  along with any desired type of precursor cells. The scaffold or matrix  382  may also contain viable tissue components  384  which are viable platelets centrifuged from blood in a manner similar to that described in U.S. patent application Ser. No. 09/483,676, filed Jan. 14, 2000 and U.S. Pat. No. 6,174,313. The viable tissue components  384  may be fragments harvested from a patient in the manner disclosed in the aforementioned U.S. Pat. No. 6,174,313. 
         [0226]    The scaffold or matrix  382  may have a layered construction with each of the layers being formed at different materials. Each of the layers of the scaffold or matrix may be impregnated with a different material and/or contain different viable tissue components  384 . For example, precursor cells may be provided in one layer of the scaffold or matrix  382  and tissue growth inductive factors and/or antibiotics may be provided in another layer of the scaffold or matrix. The scaffold or matrix  382  may be formed of body tissue such as allograft or autograft. The viable tissue components  384  in the scaffold or matrix  382  may be obtained from the patient or from another human being. Alternatively, the viable tissue components  384  may be obtained from an animal. 
         [0227]    The scaffold  382  and viable tissue components  384  may be utilized to create organ or gland structure or tissue, such as structural tissue of a pancreas, liver, or kidney. The scaffold or matrix  382  and viable tissue components  384  may be used in the repair of components of a patient&#39;s cardiovascular system including the heart and/or blood vessels. It should be understood that a plurality of different types of viable cells may be provided on a single three dimensional matrix or scaffold  382 . 
         [0228]    The scaffold  382  and viable tissue components  384  may advantageously be positioned in the patient&#39;s body by the robotic mechanism  38 . When the scaffold  382  and viable tissue components  384  are to be positioned in the patient&#39;s body by the robotic mechanism  38 , the scaffold and viable tissue components are moved through the limited incision  52  ( FIG. 1 ) by the robotic mechanism  38 . When the scaffold or matrix  382  has a rigid structure, the scaffold may be formed as a plurality of separate sections. The rigid sections of the scaffold  382  are sequentially moved through the limited incision  52  and secured to tissue in the patient&#39;s body with suitable fasteners, such as the staple  330  and/or suture  66 , anchor  60  and retainer  72  fasteners of  FIG. 5 , by the robotic mechanism  38 . The sections of the scaffold  382  may be secured in any desired manner, including the manner illustrated in  FIGS. 2-4  or  FIGS. 23-26  herein. 
         [0229]    When the scaffold or matrix  382  ( FIGS. 27-29 ) has a flexible structure, the scaffold may be rolled up outside the patient&#39;s body to form a cylinder. The rolled up scaffold  382 , with the viable tissue components  384  thereon, is moved through the limited incision  52  ( FIG. 1 ) into the patient&#39;s body by operation of the robotic mechanism  38 . Once the rolled up scaffold  382  and viable tissue components  384  ( FIGS. 27-29 ) have been moved into the patient&#39;s body by the robotic mechanism  38 , the robotic mechanism unrolls the flexible scaffold  382  with the viable tissue components  384  on the scaffold. The robotic mechanism  38  is then operated to position the unrolled scaffold  382  and viable tissue components  384  relative to tissue in the patient&#39;s body. The unrolled scaffold  382  is connected with the patient&#39;s body tissue with suitable fasteners, such as the staples  330  and/or suture, anchor and retainer fasteners of  FIG. 5 , by the robotic mechanism  38 . The scaffold  382  may be secured in any desired manner, including the manner illustrated in  FIGS. 2-4  or  FIGS. 23-26  herein. While the robotic mechanism  38  may position and secure the scaffold  382  with the viable tissue components  384  on the scaffold, this may also be done manually. 
         [0230]    The tissue positioning assembly  200  ( FIG. 30 ) may be used to position the scaffold  382  and viable tissue components  384  relative to the body tissue  334 . When this is to be done, the long thin member  202  is moved through the scaffold  382  into the body tissue  334  with the leading end portion  204  of the long thin member in the contracted condition of  FIG. 9 . The leading end portion  204  is then expanded in the body tissue  334  ( FIG. 30 ). Alternatively, the leading end portion  204  may be moved through the body tissue and then expanded, in the manner illustrated in  FIGS. 10, 11, and 12 . 
         [0231]    A gripper member  232  ( FIG. 30 ) may be moved along the long thin member  202 . The gripper member  232  is pressed against the scaffold  382 , in the manner indicated by the arrow  234 . This results in the scaffold  382  being pressed against the body tissue  334 . The scaffold  382  and a portion of the body tissue  334  are clamped between the gripper member  232  and expanded end portion  204  of the long thin member  202 . 
         [0232]    The long thin member  202  ( FIG. 30 ) and gripper member  232  are used to grip the scaffold  382  and body tissue  334  and to move them to any desired position in the patient&#39;s body. In addition, the gripper member  232  and long thin member  202  hold the scaffold  382  and body tissue  334  in a desired relationship to each other and to other tissue in the patient&#39;s body during securing of the scaffold to the body tissue with the staple  330  and/or other fasteners. If desired, a retainer  72  may be secured to the long thin member, in the manner illustrated in  FIG. 19 . This would enable the long thin member  202  ( FIG. 30 ) to be used as a portion of a fastener interconnecting the scaffold  382  and body tissue  334 . 
         [0233]    The viable tissue components  384  may be positioned in the patient&#39;s body in ways other than using the scaffold or matrix  382 . Thus, body tissue components, including viable body tissue components  384 , may be harvested from a human or animal body in the manner disclosed in the aforementioned U.S. Pat. No. 6,174,313. The tissue components may then be shaped to form a body having a desired configuration. The tissue components may be shaped using a press in the manner disclosed in U.S. Pat. No. 6,132,472. Alternatively, the tissue components may be shaped to a desired configuration by a molding process. The molding process may be performed using a press similar to any one of the presses disclosed in U.S. Pat. No. 6,132,472. Alternatively, the molding process may be performed using an open mold. The resulting shaped body of tissue components, including viable tissue components, may be secured in a patient&#39;s body using the robotic mechanism  38  and one or more of the fasteners disclosed herein. 
       Tissue Retractors 
       [0234]    The robotic mechanism  38  ( FIG. 1 ) may be used to position a tissue retractor assembly  392  ( FIG. 31 ) relative to body tissue. The robotic mechanism effects operation of the tissue retractor assembly  392  from a contracted condition to an expanded condition to move body tissue. This movement of body tissue may advantageously create a space for the performance of a surgical procedure by the robotic mechanism  38 . Thus, space could be created for the positioning of a suture connection of the type illustrated in  FIG. 5  and/or for a staple connection of the type illustrated in  FIGS. 22 and 26 . Of course, other surgical procedures could be conducted in the space created by expansion of the tissue retractor assembly  392 . 
         [0235]    The tissue retractor assembly  392  ( FIG. 31 ) includes a tubular, cylindrical cannula or scope  396 . A tubular, cylindrical shaft  398  is disposed in a coaxial relationship with the cannula or scope  396  and extends axially through the cannula or scope. However, if desired, the shaft  398  may be offset to one side of the cannula or scope  396 . This would facilitate the insertion of one or more surgical instruments through the cannula  396  to a working space  400  created by expansion of a balloon or bladder  402  from the contracted condition shown in dash lines in  FIG. 31  to the expanded condition in solid lines in  FIG. 31 . 
         [0236]    As the bladder or balloon expands, portions of body tissue  406  are deflected under the influence of force applied to the body tissue by the bladder or balloon  402 . If desired, the bladder or balloon  402  may have a toroidal configuration with a central passage so that surgical instruments may be inserted through the balloon to a working space  404  offset to the right (as viewed in  FIG. 31 ) of the balloon. Expansion of the balloon  402  may be utilized to conduct a surgical procedure, such as dissection. 
         [0237]    The tubular shaft  398  has a central passage through which fluid, such as a liquid or gas, may be conducted to the bladder or balloon  402  to effect expansion of the bladder or balloon from the contracted condition to the expanded condition. The shaft  398  and cannula or scope  396  are connected with the robotic mechanism  38  ( FIG. 1 ) to enable the robotic mechanism to position the tissue retractor assembly  392  relative to the body tissue  406  and to enable the robotic mechanism to control the flow of fluid to the bladder or balloon  402  to thereby control the extent of expansion of the bladder or balloon. 
         [0238]    It is contemplated that the tissue retractor assembly  392  may have a construction which is different than the construction illustrated in  FIG. 26 . Thus, the tissue retractor assembly  392  may have any one of the constructions disclosed in U.S. Pat. Nos. 6,042,596 and 6,277,136. The robotic mechanism may be utilized to effect operation of a selected tissue retractor assembly in the same manner as is disclosed in the aforementioned U.S. Pat. Nos. 6,042,596 and 6,277,136. 
         [0239]    If the tissue retractor assembly is to effect separation of body tissues along naturally occurring planes, the robotic mechanism  38  may be operated to move the tissue retractor assembly  392  to the desired position in a patient&#39;s body where the balloon or bladder  402  is filled with fluid to effect expansion of the bladder or balloon to the condition illustrated in solid lines in  FIG. 26 . The bladder or balloon is then contracted, by exhausting fluid from the bladder or balloon  402  through the shaft  398 . The robotic mechanism  38  may be then operated to advance either just the contracted bladder or balloon  402  relative to the body tissue  406  or to advance the entire tissue retractor assembly  392  relative to the body tissue. Once the bladder or balloon  402  has been advanced, with or without the cannula scope  396 , by operation of the robotic mechanism  38 , the bladder or balloon  402  is again expanded. This sequential contraction, advancement, and expansion of the bladder or balloon may be repeated any desire number of times to effect the desired separation of portions of the body tissue  406 . 
         [0240]    It is contemplated that the balloon or bladder  402  may be left in a patient&#39;s body. When this is to be done, the balloon or bladder  402  may be formed of a biodegradable material. Of course, components of the retractor assembly  392  other than the balloon bladder  402  may be formed of biodegradable material. 
         [0241]    A tissue retractor assembly may be utilized to separate bones at a joint. In  FIG. 32 , a tissue retractor assembly  410  is positioned in a shoulder joint  412 . Specifically, the robotic mechanism  38  is operated to position the tissue retractor assembly  410  relative to a humeral head  414 , achromium  416  and rotator cuff  418  in the shoulder joint  412 . 
         [0242]    Once the tissue retractor assembly  410  has been positioned at a desired location in the shoulder joint  412 , the robotic mechanism  38  effects expansion of a balloon or bladder in the tissue retractor assembly  410  from a contracted condition to an expanded condition. This effects movement of the achromium  416  relative to the rotator cuff  418 . This increases the space in the shoulder joint for the surgeon to work on the body tissue. The manner in which the tissue retractor assembly  410  is used in the shoulder joint  412  is similar to the manner disclosed in the aforementioned in U.S. Pat. No. 6,277,136. 
         [0243]    In  FIG. 32 , the tissue retractor assembly  410  is utilized to create space within a shoulder joint  412 . However, it is contemplated that the robotic mechanism  38  may be utilized to position a contracted tissue retractor assembly relative to other joints in a patient&#39;s body and to effect expansion of the tissue retractor assembly to create space in these joints. For example, the tissue retractor assembly may be utilized in association with a knee joint in a leg of a patient or with vertebrae in a patient&#39;s spinal column. 
         [0244]    When a tissue retractor assembly is to be utilized to create space in a joint in a patient&#39;s spinal column, the contracted tissue retractor assembly may be inserted between adjacent vertebrae. A balloon or bladder in the tissue retractor assembly is then expanded under the influence of fluid pressure to increase the space between the vertebrae. Depending upon the construction of the tissue retractor assembly and the position where it is located in the patient&#39;s spinal column by the robotic mechanism  38 , the expansion of the tissue retractor assembly can separate adjacent vertebrae without significantly changing the spacial orientation of vertebrae relative to each other. Alternatively, the tissue retractor assembly may be positioned by the robotic mechanism  38  at a location where expansion of the tissue retractor assembly results in a tilting or pivoting movement of one vertebra relative to an adjacent vertebra. The tissue retractor assembly may have any one of the constructions disclosed in the aforementioned U.S. Pat. Nos. 6,042,596 and 6,277,136. 
         [0245]    A tissue retractor assembly  422  ( FIG. 33 ) is moved through an opening formed in a vertebrae  424  in a patient&#39;s spinal column. The robotic mechanism  38  may be utilized to form the opening in the vertebrae  424  and to move the contracted tissue retractor assembly  422  into the vertebra. 
         [0246]    Once the robotic mechanism  38  has been operated to position the tissue retractor assembly relative to the vertebra  424 , the robotic mechanism effects expansion of a bladder or balloon  426  from a contracted condition to the expanded condition illustrated schematically in  FIG. 33 . As this occurs, marrow is compressed within the vertebra  424 . The tissue retractor assembly  422  includes a cannula or scope  428  which is utilized to position the balloon or bladder  426  relative to the vertebra  424  and to conduct the fluid (gas or liquid) into the balloon or bladder  426  to effect expansion of the balloon or bladder. The balloon or bladder  426  may be formed of a biodegradable material. 
         [0247]    The tissue retractor assembly  422  is subsequently contracted from the expanded condition of  FIG. 33  and withdrawn from the vertebra  424 . When this has been done, flowable synthetic bone material or cement may be conducted through a cannula into the space in the vertebra  424 . It is contemplated that the robotic mechanism  38  will be utilized to position the cannula through which the flow of synthetic bone material or cement is conducted into the space created in the vertebra  424  by expansion of the balloon or bladder  426 . The manner in which the balloon or bladder  426  may compress the marrow within the vertebra  424  and create a space which is subsequently filled with synthetic bone material or cement is the same as is disclosed in U.S. Pat. No. 4,969,888. 
         [0248]    The balloon or bladder  426  may be formed of a biodegradable material and filled with bone growth inductive factors. The bone growth inductive factors may include bone particles and bone morphogenetic protein. Viable tissue components may be provided in the balloon or bladder  426 . The balloon or bladder  426  will degrade with the passage of time and enable bone or other tissue to grow in the space created in the vertebra  424 . The balloon or bladder  426  may be filled with a patient&#39;s body tissue components harvested in the manner disclosed in U.S. Pat. No. 6,174,313. 
         [0249]    In  FIG. 33 , the tissue retractor assembly  422  has been illustrated in conjunction with a vertebra in a patient&#39;s body. It is contemplated that the tissue retractor assembly could be utilized in association with other bones in a patient&#39;s body. By utilizing the robotic mechanism  422  to position the tissue retractor assemblies  392 ,  410  and  422  ( FIGS. 31-33 ) relative to a patient&#39;s body, the tissue retractor assemblies can be accurately positioned. The robotic mechanism  38  controls the fluid pressure and thus the force conducted to the bladder or balloon in the tissue retractor assemblies  392 ,  410  and  422 . In addition, the use of the robotic mechanism  38  to control the operation of the tissue retractor assemblies  392 ,  410  and  422  enables the size of an incision through which the tissue retractor assemblies are inserted to be minimized and the size of an incision for surgical instruments to perform the surgical procedure in space created by operation of the tissue retractor assemblies is minimized. 
       Threaded Fasteners 
       [0250]    The robotic mechanism  38  may also be utilized to secure body tissue with a threaded fastener  440  as illustrated in  FIG. 34 . Of course, the robotic mechanism  38  may be used with other fasteners if desired. For example, the robotic mechanism  38  could be used in association with fasteners having any one of the constructions disclosed in U.S. Pat. Nos. 5,293,881; 5,720,753; 6,039,753; and 6,203,565. 
         [0251]    The robotic mechanism  38  includes a programmable computer  444  ( FIG. 34 ) which is connected with a fastener drive member  446  by a motor  448 . In addition to the motor  448 , a force measurement assembly  450  is connected with fastener drive member  446  and computer  444 . The force measurement assembly  450  has an output to the computer  444  indicating the magnitude of resistance encountered by the fastener drive member  446  to rotation of the fastener  440 . A position sensor  452  is connected with fastener drive member  446  and the computer  444 . The position sensor  452  has an output which is indicative of the position of the fastener drive member  446 . The output from the position sensor  452  indicates the depth or distance to which the threaded fastener is moved into body tissue by operation of the motor  448  to rotate the fastener drive member  446 . 
         [0252]    The threaded fastener  440  includes a head end portion  456  with a recess  458  which receives a polygonal projection  460  from the fastener drive member  446 . Rotation of the fastener drive member  446  by the motor  448  causes the projection  460  to transmit drive torque to the head end portion  456  of the fastener  440 . 
         [0253]    As the fastener  440  is rotated, a thread convolution  462  on a shank portion  464  engages body tissue. The thread convolution  462  has a spiral configuration. The thread convolution cooperates with the body tissue to pull the threaded fastener into the body tissue as the threaded fastener is rotated. 
         [0254]    By utilizing the robotic mechanism  38  to manipulate the fastener  440 , the fastener can be accurately positioned relative to body tissue. The output from the force measurement assembly  450  to a computer  444  enables the force, that is resistance to rotation on the threaded fastener  440 , to be controlled during rotation of the fastener. This prevents the application of excessive force to the body tissue. In addition, the position sensor  452  enables the distance to which the fastener  440  is moved into the body tissue to be accurately controlled. 
       Implant 
       [0255]    In addition to fasteners to secure tissue in a patient&#39;s body, the robotic mechanism  38  may be utilized to position prosthetic implants in a patient&#39;s body. During joint replacement surgery and other surgical procedures, prosthetic implants may be placed in a patient&#39;s body. The robotic mechanism  38  may be utilized to control movement of a cutting tool during resection of bone in a patient&#39;s body. 
         [0256]    It is contemplated that the joint replacement surgery may include knee joint replacement. The computer  38  may be utilized to effect a cutting of end portions of a tibia and/or femur in the manner disclosed in U.S. patent application Ser. No. 09/976,396 filed Oct. 11, 2001, by Peter M. Bonutti and entitled Method of Performing Surgery. In addition, the robotic mechanism  38  may be utilized to position a prosthetic implant, such as a tibial tray  470  ( FIG. 35 ) relative to a proximal end portion  472  of a tibia  474  in a leg  476  of a patient. The tibial tray  470  has a keel  478  which is inserted into the proximal end portion  472  of the tibia  474  in the leg  476  of the patient during a knee replacement operation. 
         [0257]    During the knee replacement operation, the robotic mechanism  38  effects a resection of both the tibia  474  and femur  480  in the leg  476  of the patient. The robotic mechanism  38  then moves a force transmitting member  484  to move the keel  478  of the tibial tray  470  through a limited incision  488  in the leg  476  of the patient. 
         [0258]    The robotic mechanism  38  includes a programmable computer  444  which is connected with the force transmitting member  484  by a motor  492 . Operation of the motor  492  is effective to move the force transmitting member and tibial tray  470  relative to the tibia  472  to force the keel  478  of the tibial tray  470  into the tibia  472 . A force measurement assembly  494  is connected with the force transmitting member  484  and the computer  444 . The output from the force measurement assembly  494  is indicative of a resistance encountered by the force transmitting member  484  in moving the tibial tray  470  into the tibia  474 . By monitoring the output from the force measurement assembly  494 , the computer  444  can provide an indication to a surgeon of the resistance being encountered to movement of the keel  478  of the tibial tray into the tibia  474  in the patient&#39;s leg  476 . 
         [0259]    A position sensor  496  is connected with the force transmitting member  484  and the computer  444 . The position sensor  496  has an output indicative of the position of the force transmitting member  484  relative to the proximal end portion  472  of the tibia  474 . This enables a surgeon to monitor the extent movement of the keel  478  on the tibial tray into the proximal end portion  472  of the tibia  474 . 
         [0260]    The motor  492  has an operating mechanism which effects a pounding of the tibial tray  470  into the proximal end portion  472  of the tibia  474  in much the same manner as in which a hammer has previously been utilized to pound the tibial tray  470  into the  474 . However, it is believed that it may be desired to effect the operation of the motor  492  to move the force transmitting member  484  and tibial tray  470  with a continuous insertion stroke without pounding on the tibial tray. This would result in the tibial tray  470  being slowly pressed into the proximal end portion  472  of the tibia  474  with a continuous movement which is monitored by the output from the force measurement assembly  494  and the position sensor  496 . By moving the tibial tray  470  with a smooth insertion stroke, accurate insertion of the tibial tray into the tibia  474  is facilitated. 
         [0261]    Once the robotic mechanism  38  has been utilized to position the tibial tray  470 , a related component of a replacement knee joint may be positioned on the femur  480  by the robotic mechanism. The robotic mechanism  38  may also be utilized to check stability of the knee joint in flexion, extension, and/or rotation. In the manner in which the robotic mechanism is utilized to perform these functions is the same as disclosed in the aforementioned U.S. patent application Ser. No. 09/976,396. 
         [0262]    Imaging 
         [0263]    It is contemplated that various imaging arrangements may be utilized to enable a surgeon to monitor a surgical procedure, while using the robotic mechanism  38 . In the embodiment illustrated in  FIG. 1 , the single imaging device  40  is utilized to enable imaging of a location where a surgical procedure is being conducted by the robotic mechanism  38  to be transmitted to a monitor  48 . Stereoscopic and video stereoscopic viewing of the location where a surgical procedure is being performed by the robotic mechanism  38  may also be desired. 
         [0264]    A pair of endoscopes  502  and  504  ( FIG. 36 ) may be used in association with the robotic mechanism  38 . The endoscopes  502  and  504  are disposed in predetermined angular orientations relative to each other. The output from the endoscopes  502  and  504  is conducted to the computer  44 . 
         [0265]    The viewing screen of the monitor  48  may be divided into two sections with one section being a monoscopic, that is, two dimensional, image resulting from the output of the endoscope  502 . The other section of the screen of the monitor  48  has a monoscopic, that is, two dimensional, image resulting from the output of the endoscope  504 . The monitor  508  may be utilized to provide a steroscopic image, that is, a three dimensional image, resulting from the output of both of the endoscopes  502  and  504 . The manner in which the stereoscopic images may be obtained from the two endoscopes  502  and  504  at the monitor  508  is similar to that disclosed in U.S. Pat. Nos. 4,651,201 and 5,474,519. 
         [0266]    By providing a three dimensional image at the monitor  508 , a surgeon has a realistic view of the area where the robotic mechanism  38  is performing a surgical procedure. This enables the surgeon to conduct stereotactic surgery. 
         [0267]    A navigation system may also provide inputs to the computer  44  to assist in the control of the robotic mechanism  38  and the performance of the surgical procedure. The navigation system may include transmitters connected with the robotic mechanism  38 . Transmitters may also be connected with the endoscope  502  and  504 . 
         [0268]    If desired, a plurality of navigation members may be connected with tissue in the patient&#39;s body by the robotic mechanism  38 . Reflective end portions of the navigation members are disposed in the patient&#39;s body and are illuminated by light conducted along fiber optic pathways in the endoscopes  502  and  504 . Images of the ends of the navigation members are conducted from the endoscopes  502  and  504  to the monitors  48  and  508 . The images of the ends of the navigation members enable a surgeon to determine the relative positions of body tissue in the patient&#39;s body during performance of a surgical procedure with the robotic mechanism. 
         [0269]    Alternatively, the navigation members may extend through the patient&#39;s skin into engagement with one or more tissues in a patient&#39;s body. Reflective ends of the navigation members would be disposed outside of the patient&#39;s body and would be visible to the surgeon. In addition, the reflective ends of the navigation members would be visible to an optical sensing system connected with the computer  44  and robotic mechanism  38 . Relative movement between the reflective ends of the navigation members would be sensed by the optical sensing system and would enable the computer  44  to determine the relative positions of tissues in the patient&#39;s body. In addition, relative movement between the reflective ends of the navigation members could be visually sensed by the surgeon and would enable the surgeon to determine the relative positions of tissues in the patient&#39;s body based on direct observation of the navigation members. 
         [0270]    For example, the navigation members could be connected with one or more bones in a patient&#39;s body. When the reflective ends of the navigation members are disposed in the patient&#39;s body, the endoscope  502  and  504  can be used to determine the location of one or more bones relative to other tissues. When the reflective ends of the navigation members are disposed outside the patient&#39;s body, the surgeon and/or an optical sensing system can determine the location of one or more bones relative to other tissues. 
         [0271]    Rather than using two endoscopes  502  and  504  to obtain images, an ultrasonic imaging device may be used with only one of the endoscopes. For example, the endoscope  504  could be omitted or merely turned off. A known ultrasonic imaging device may be used to provide images which are transmitted to the computer  44 . The ultrasonic imaging device may be constructed and operated in a manner similar to that disclosed in U.S. Pat. Nos. 5,897,495 and 6,059,727. The images which are transmitted to the computer  44  from the ultrasonic imaging device may be used to create monoscopic images at the monitor  48 . Alternatively, the images from the ultrasonic imaging device may be combined with images from the endoscope  502  to create stereoscopic images. If desired, the stereoscopic images may be created in the manner disclosed in U.S. Pat. No. 6,059,727. 
         [0272]    The images provided by the endoscopes  502  and  504  and/or an ultrasonic imaging device enable the surgeon to monitor the performance of any of the surgical procedures disclosed herein. Additionally, various combinations of the foregoing steps may be included in the surgical procedures. For all surgical procedures, the images provided at the monitors  48  and  508  ( FIG. 36 ) by the endoscopes  502  and  504  and/or the ultrasonic imaging device will facilitate performance of the surgical procedure in the patient&#39;s body with the robotic mechanism  38 . 
         [0273]    The robotic mechanism  38  may be utilized with a fluoroscope  520  ( FIG. 37 ). The general construction and mode of operation of the fluoroscope  520  and an associated control unit  522  is the same as is disclosed in U.S. Pat. Nos. 5,099,859; 5,772,594; 6,118,845 and/or 6,198,794. The output from an endoscope  524  is transmitted to a computer  526 . An image resulting from operation of the fluoroscope  520  is transmitted from the control unit  522  to the computer  526 . This enables a monitor for the computer  526  to provide either two separate monoscopic, that is two dimensional, and/or a single stereoscopic or three dimensional view corresponding to the output from both the fluoroscope  520  and the endoscope  524 . This may be done by having the computer  526  connected with two monitors, corresponding to the monitors  48  and  508  of  FIG. 36 . 
         [0274]    The three dimensional image provided by the monitor connected with the computer  526  results from a combining of images obtained with the endoscope  524  and fluoroscope  520 . The three dimensional image enables a surgeon to have a clear view of a location in a patient&#39;s body where the robotic mechanism  38  is being utilized to perform a surgical procedure. Of course, the surgical procedure performed by the robotic mechanism  38  may involve the securing of body tissue and/or a scaffold containing viable tissue components with fasteners in the manner previously explained herein. Alternatively, the surgical procedure may involve the moving and/or dissecting of body tissue with one of the retractors of  FIGS. 31-33 . The cooperation between the fluoroscope  520  and endoscope  524  facilitates the performance of stereotactic surgical procedures utilizing the robotic mechanism  38 . 
         [0275]    If desired, an ultrasonic imaging device may be used with either or both of the fluoroscope  520  and endoscope  524 . Images obtained with the ultrasonic imaging device may be used with images from the fluoroscope and/or endoscope to provide wither stereoscopic or monoscopic images at monitors which are visible to the surgeon and correspond to the monitors  48  and  508  of  FIG. 36 . 
         [0276]    A magnetic resonance imaging unit  530  ( FIG. 38 ) may be utilized in association with the robotic mechanism  38  during performance of a surgical procedure on the patient  34 . The magnetic resonance imaging unit  530  (MRI) provides an image of a location where the surgical procedure is being performed in a patient&#39;s body. The portion of the robotic mechanism  38  exposed to a magnetic field generated during use of the magnetic resonance imaging unit  530  (MRI) is formed of non-magnetic materials. Thus, the portion of the robotic mechanism  38  which extends into the magnetic field of the magnetic resonance imaging unit  530  is formed of a material which does not respond to a magnetic field. These materials may include polymeric materials and metals which are not responsive to a magnetic field. 
         [0277]    An endoscope  534  ( FIG. 38 ) cooperates with the magnetic resonance imaging unit  530  (MRI) to provide for imaging of the location in the patient  34  where a surgical procedure is being conducted by the robotic mechanism  38 . Nonmagnetic materials, primarily polymeric materials, may be used in the endoscope  534 . A monitor  538  is disposed at a location where it is visible to the surgeon and is outside of a magnetic field resulting from operation of the magnetic resonance imaging unit  530 . The monitor  538  is connected with a computer (not shown) which is connected with both the endoscope  534  and the magnetic resonance imaging unit  530 . 
         [0278]    The monitor  538  may provide the surgeon a stereoscopic image, that is, a three dimensional image, resulting from outputs of the magnetic resonance imaging unit  530  and the endoscope  534 . Alternatively, the imaging unit  538  may provide one monoscopic image, that is, a two dimensional image corresponding to the output of the magnetic resonance imaging unit  530  and a second monoscopic image corresponding to the output of the endoscope  534 . The endoscope  534  is constructed of non-magnetic materials which are not effected by the magnetic field of the magnetic resonance imaging unit  530 . 
         [0279]    Rather than using a magnetic resonance imaging unit  530  to provide an image in association with the endoscope  534 , the image may be provided by computerized tomographic scanning and/or positron emission tomography. Regardless of which of the imaging devices is utilized to provide an image of the area where surgical procedure is being conducted, it is believed that it would be advantageous to utilize the robotic mechanism  38  to conduct the surgical procedure. 
       Markers 
       [0280]    In order to facilitate a surgeon&#39;s visualization of the location of articles utilized during the performance of surgical procedures by the robotic mechanism  38 , markers may be provided in association with the articles. The markers which are utilized in association with one or more articles should be readily detected in an image provided by an imaging unit associated with the robotic mechanism  38 . When the endoscopes  40 ,  502 ,  504 ,  524  and/or  534  are associated with the robotic mechanism  38 , the markers should be clearly visible in an image transmitted to a monitor, such as the monitor  48 ,  508 , and/or  538  from one or more of the endoscopes. When the fluoroscope  520  ( FIG. 27 ) is associated with the robotic mechanism  38 , the markers should be clearly visible in images transmitted to a monitor from the fluoroscope and/or an associated endoscope. Similarly, when a magnetic resonance imaging unit  530  ( FIG. 38 ) is associated with the robotic mechanism  38 , the markers should be clearly visible in an image transmitted to the monitor  538  from the magnetic resonance imaging unit. 
         [0281]    To facilitate locating articles with the endoscopes  40 ,  502 ,  504 ,  524 , and/or  534 , light reflective particles may be used as markers. The light reflective particles are illuminated by light conducted along fiber optic pathways in the endoscopes. The light reflective particles may be embedded in the material of the anchor  60  and the suture retainer  72 . Alternatively, a light reflective coating could be provided on the exterior of the anchor  60  and/or suture retainer  72 . It is also contemplated that light reflective particles could be included in the material of the suture  66 . 
         [0282]    The staples  300  and  330  ( FIGS. 21-26 ) may be provided with markers to facilitate locating the staples in an image from the endoscopes  40 ,  502 ,  504 ,  524  and/or  534 . The markers may be reflective particles embedded in the material of the staple  300  or  330 . Alternatively, a reflective coating could be provided on the staple  300  or  330 . The reflective particles may be embedded in only the connector or bight portions  318  and  346  of the staples  300  and  330 . Similarly, the coating of reflective material may be applied to only the connector or bight portions  318  and  346  of the staples  300  and  330 . 
         [0283]    In order to facilitate positioning of the scaffold  382  and viable tissue components  384 , light reflective particles may be connected with portions of the scaffold  382 . Thus, a marker formed of light reflective particle may be provided at each of the corners of the rectangular scaffold  382  illustrated in  FIG. 29 . Of course, if the scaffold  382  had a different configuration, light reflective particles would be provided at different locations on the scaffold. Regardless of the configuration of the scaffold  382 , it is preferable to locate the light reflective particles adjacent to the periphery of the scaffold. 
         [0284]    The light reflective particles may be disposed in small groups at spaced locations on the scaffold. Alternatively, the light reflective particles may be disposed in one or more threads which extend along one or more edges of the scaffold. The light reflective particles are formed of a substance which is compatible with the patient&#39;s body and reflects light. For example, polished titanium, gold, or platinum particles could be utilized. Alternatively, crystals which reflect light may be used as markers. The crystals may be formed of a salt and dissolve in a patient&#39;s body. 
         [0285]    When the markers are to be used with the fluoroscope  520  and endoscope  524 , it is believed that it may be preferred to form the marker of a radiopaque material which is also reflective. For example, polished particles of titanium, would reflect light so as to be visible in an image transmitted from the endoscope  524  and would be radiopaque so as to be visible in an image transmitted from the fluoroscope  520 . It is contemplated that the radiopaque and light reflective particles could be formed off of other materials if desired. For example, a particle which is radiopaque and another particle which is reflective may be utilized. The radiopaque particle would be visible in the image transmitted from the fluoroscope  520  and the reflective particle would be visible in an image transmitted from the endoscope  534 . 
         [0286]    The reflective radiopaque particles may be embedded in the material of the anchor  60  and suture retainer  72 . In addition, the particles may be embedded in the material of the suture  66 . Alternatively, the radiopaque and light reflective particles may be provided as a coating on at least a portion of the anchor  60 , suture retainer  72  and/or suture  66 . 
         [0287]    When the robotic mechanism  38  of  FIG. 37  is to be utilized in association with the fluoroscope  520  and endoscope  524  to position the scaffold  382 , a light reflective and radiopaque marker may be connected with the scaffold. The light reflective and radiopaque marker may be formed by polished particles of titanium disposed at selected locations along the periphery of the scaffold  382 . Alternatively, the marker could be formed of a combination of light reflective particles and radiopaque particles. The light reflective particles would be visible in images transmitted by the endoscope  524  and the radiopaque particles would be visible in images transmitted by the fluoroscope  520 . 
         [0288]    The magnetic resonance imaging unit  530  has a relatively strong magnetic field. Therefore, markers provided in association with articles to be used during performance of a surgical procedure to be imaged with the magnetic resonance imaging unit  530  cannot be formed of a magnetic or magnetizable material. Images transmitted to the monitor  538  from the magnetic resonance imaging unit  530  ( FIG. 38 ) are readily visible if they have a relatively high water or hydrogen content. Therefore, capsules of Vitamin E may be associated with articles to be used during the performance of surgery by the robotic mechanism  38  and imaging with the magnetic residence imaging unit  530 . These capsules may be connected with the article or may be embedded in the article. When the capsules are to be embedded in the article, it is believed that it may be preferred to utilize relatively small microcapsules which will not significantly impair the strength of the materials in which they are embedded. The microcapsules may contain Vitamin E, water, or air. 
         [0289]    The microcapsules may be embedded in the material of the anchor  60  and/or suture retainer  72 . The microcapsules may also be embedded in the material of the staples  300  and  330 . This would enable the anchor  60 , suture retainer  72  and/or staples  300  and  330  to be readily visible in an image transmitted from the magnetic resonance imaging unit  530 . 
         [0290]    When articles are to be imaged with the magnetic resonance imaging unit  530 , the articles may be marked by a coating of hydrophilic material. The coating of hydrophilic material absorbs body liquid and increases the contrast between the articles and the surrounding environment. For example, the staple  300  ( FIGS. 21 and 22 ) and/or the staple  330  ( FIGS. 23-26 ) may be coated with hydrophilic material. The areas of the staples which are to be bonded together, that is, the end portions  302  and  304  of the staple  300  and the side surfaces of the legs  342  and  344  of the staple  330  ( FIGS. 24 and 26 ), may be left free of the hydrophilic material to promote a formation of a bond between the legs of the staple. They hydrophilic material may be a jell formed of materials such as algin, vegetable gums, pectins, starches, and/or of complex proteins such as gelatin and collagen. 
         [0291]    The scaffold  382  may have one or more fibers formed of a hydrophilic material. Alternatively, small bodies of hydrophilic material could be positioned at various locations along the periphery of the scaffold  382 . It is contemplated that the entire scaffold  382  could be formed a hydrophilic material, such as collagen. 
         [0292]    A marker which is to be used with an endoscope  40 ,  502 ,  504 ,  524 , and/or  534  may be a luminescent material. The luminescent material may be in the form of crystals such as zinc or cadmium sulfide. Alternatively, the luminescent material may be a dye. The marker may have chemiluminescence, bioluminescence, photoluminescence or triboluminescence. 
         [0293]    The luminescent material forming a marker may be disposed on the surface of the anchor  60 , suture retainer  72 , and/or the suture  66 . It is contemplated that the luminescent material forming a marker may form a coating over a portion of either the staple  300  ( FIGS. 21 and 22 ) or the staple  330  ( FIGS. 23-26 ). 
         [0294]    It is contemplated the markers for use with the endoscopes  40 ,  502 ,  504 ,  524  and/or  534  may be used with fasteners other than the particular fasteners enclosed herein. Thus, one or more of the various markers previously described herein may be utilized in connection with a bonded rivet of the type disclosed in U.S. Pat. No. 6,203,565. Of course, the makers may be used in association with any of the other surgical implants disclosed in the aforementioned U.S. Pat. No. 6,203,565. 
         [0295]    The markers previously described herein may be utilized with any one of the expandable retractor assemblies  392 ,  410 , or  422  ( FIGS. 31-33 ) to indicate the positions of the retractor assemblies in an image on a monitor visible to a surgeon. The markers may be positioned on the balloons or bladders in the retractor assemblies  392 ,  410  and  422 . Thus, a marker may be provided on the balloon or bladder  402  in the retractor assembly  392 . 
         [0296]    The marker on the balloon or bladder  402  ( FIG. 31 ) may be light reflective so as to be detectable in an image provided by an endoscope  40  ( FIG. 1 ). The marker on the balloon or bladder  402  may also be radiopaque so as to be detectable in an image provided by a fluoroscope  520  ( FIG. 37 ). It is contemplated that a layer or coating of hydrophilic material could be provided on the balloon or bladder  402  to facilitate detection of the balloon or bladder in an image provided by the magnetic resonance imaging unit  530  ( FIG. 38 ). 
       CONCLUSION 
       [0297]    In view of the foregoing description, it is clear that the present invention relates to a method of securing either hard or soft body tissue. A robotic mechanism  38  or manual effort may be used to position a fastener relative to the body tissue. The fastener may be a suture  66 , staple  300  or  330 , screw  440 , or other known device. 
         [0298]    The fastener may be a suture  66  which is tensioned with a predetermined force by a robotic mechanism  38  or manual effort. The robotic mechanism  38  or manual effort may also be used to urge a retainer  72  toward body tissue  64  with a predetermined force. The suture  66  may be gripped with the retainer  72  while the suture is tensioned with a predetermined force and while the retainer is urged toward the body tissue  64  with a predetermined force. 
         [0299]    Alternatively, the fastener may be a staple  300  or  330 . A robotic mechanism  38  or manual effort may be utilized to position the staple relative to body tissue. The robotic mechanism  38  or manual effort may effect a bending of the staple  300  or  330  to move legs of the staple into engagement with each other. The legs of the staple  300  or  330  may be bonded together at a location where the legs of the staple are disposed in engagement. 
         [0300]    Regardless of what type of fastener is utilized, a positioning apparatus  200  may be used to position the body tissue  64  before and/or during securing with a fastener. The positioning apparatus may include a long thin member  202  which transmits force to the body tissue. Force may be transmitted from an expanded end portion  204  of the long thin member  202  to the body tissue  64 . A second member  232  may cooperate with the long thin member  202  to grip the body tissue. The long thin member  202  may be positioned relative to the body tissue by a robotic mechanism  38  or manual effort. 
         [0301]    Various imaging devices may be utilized to assist in positioning a fastener, such as a rivet suture or staple, relative to body tissue. Under certain circumstances at least, it may be desirable to utilize two or more different types of imaging devices. Thus, an endoscope  534  and a magnetic resonance imaging apparatus (MRI)  530  may be utilized to provide an image. Alternatively, an endoscope  524  and a fluoroscopic device  520  may be utilized. If desired, ultrasonic imaging devices may be utilized in association with another imaging device, such as an endoscope or magnetic resonance imaging device. One or more markers may be provided on fasteners to facilitate location of the fasteners in an image. 
         [0302]    A fastener ( FIG. 5, 22 , or  26 ) may be utilized to secure a scaffold  382  containing viable tissue components  384  in place on body tissue  334 . The tissue components  384  may be stem cells, fetal cells, mesenchymal cells, and/or any desired type of precursor cells. It is contemplated that the scaffold  382  with one or more different types of tissue components may be positioned at any desired location within a patient&#39;s body, such as within an organ, by the robotic mechanism  38 . For example, the scaffold  382  could be positioned in the pancreas or liver of a patient. Alternatively, the scaffold  382  could be connected with a bone in the patient&#39;s body. The scaffold  382  may be positioned relative to the body tissue by the robotic mechanism  38  or manual effort. One or more markers may be provided on the scaffold to facilitate location of the scaffold in an image. 
         [0303]    It is contemplated that the robotic mechanism  38  may advantageously be utilized to position surgical implants other than fasteners in a patient&#39;s body. For example, the robotic mechanism  38  may be utilized to position a prosthesis  470  in a patient&#39;s body. If desired, the robotic mechanism  38  may be utilized to position a screw type fastener  440  at a specific location in a patient&#39;s body. The robotic mechanism  38  may be used to position a scaffold  382  containing viable tissue components relative to body tissue.