Patent Publication Number: US-2021161556-A1

Title: Cannula, cannula system, and manipulator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of International Application PCT/JP2018/030409 which is hereby incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to cannulas, cannula systems, and manipulators. 
     BACKGROUND ART 
     A known medical manipulator is equipped with a medical treatment device, such as surgical forceps having a distal-end treatment section and a proximal-end operating section (e.g., see Patent Literature 1 and Patent Literature 2). The medical manipulator described in Patent Literature 1 moves the medical treatment device about a trocar serving as a fulcrum attached to the body wall of a patient, so that the proximal-end operating section disposed outside the body cavity and the distal-end treatment section to be inserted into the body cavity move in directions opposite to each other. This is problematic in terms of poor operability of the medical treatment device, thus requiring a highly skilled surgeon. 
     In contrast, the manipulator described in Patent Literature 2 is for an endoscopic surgical device and transmits the movement of the proximal-end operating section to the distal-end treatment section by means of a pulley or a pantograph, thereby synchronizing the movement of the proximal-end operating section at the hands of the surgeon with the movement of the distal-end treatment section within the body cavity. 
     CITATION LIST 
     Patent Literature 
     {PTL 1} 
     Japanese Unexamined Patent Application, Publication No. 2006-150105 
     {PTL 2} 
     Japanese Unexamined Patent Application, Publication No. 2009-018027 
     SUMMARY OF INVENTION 
     A first aspect of the present invention provides a cannula including a first tubular member having a first longitudinal axis, a second tubular member having a second longitudinal axis, a connector that connects the first tubular member and the second tubular member in series, and a rear bearing that supports the second tubular member in a three-dimensionally pivotable manner around an axis intersecting the second longitudinal axis. The first tubular member has a first through-hole into which a flexible and elongated medical treatment device is insertable, and is supported by a trocar in a state where the first tubular member extends through the trocar attached to a body wall of a patient. The second tubular member has a second through-hole into which the medical treatment device is insertable. The connector connects the first tubular member and the second tubular member in a pivotable manner around an axis orthogonal to a plane including the first longitudinal axis and the second longitudinal axis. 
     A second aspect of the present invention provides a cannula including a first tubular member having a first longitudinal axis, a second tubular member having a second longitudinal axis, a connection mechanism that connects the first tubular member and the second tubular member in series, a front bearing that supports the first tubular member in a three-dimensionally pivotable manner around an axis intersecting the first longitudinal axis, a rear bearing that supports the second tubular member in a three-dimensionally pivotable manner around an axis intersecting the second longitudinal axis, and a support member configured to accommodate the connection mechanism therein and that secures a relative position between the front bearing and the rear bearing with a distance therebetween. The first tubular member has a first through-hole into which a flexible and elongated medical treatment device is insertable. The second tubular member has a second through-hole into which the medical treatment device is insertable. The connection mechanism connects the first tubular member and the second tubular member in a pivotable manner around an axis orthogonal to a plane including the first longitudinal axis and the second longitudinal axis. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates the overall configuration of a cannula and a manipulator according to a first embodiment of the present invention. 
         FIG. 2A  illustrates the overall configuration of a medical treatment device in  FIG. 1 . 
         FIG. 2B  illustrates a state where a gripping section in  FIG. 2A  is bent. 
         FIG. 3  is an enlarged view of a handle in  FIG. 2A . 
         FIG. 4A  illustrates the overall configuration of the cannula in  FIG. 1 . 
         FIG. 4B  illustrates a state where a first tubular member and a second tubular member of the cannula in  FIG. 4A  are pivoted. 
         FIG. 5A  is a cross-sectional view of the cannula in  FIG. 1 . 
         FIG. 5B  is a vertical sectional view of the cannula in  FIG. 1 . 
         FIG. 6A  illustrates the overall configuration of a connection mechanism in  FIG. 4A . 
         FIG. 6B  is a perspective view illustrating a state where the connection mechanism in  FIG. 6A  is pivoted around a rotation axis. 
         FIG. 7A  illustrates the overall configuration of a front bearing (or a rear bearing) in  FIG. 4A . 
         FIG. 7B  is a vertical section view of the front bearing (or the rear bearing) in  FIG. 7A . 
         FIG. 8A  illustrates a state where the cannula and the medical treatment device in  FIG. 1  are linearly extended. 
         FIG. 8B  illustrates a state where the medical treatment device in  FIG. 8A  is bent together with the cannula. 
         FIG. 9A  illustrates a state where the medical treatment device is moved forward while the cannula and the medical treatment device in  FIG. 1  are linearly extended. 
         FIG. 9B  illustrates a state where the cannula and the medical treatment device in  FIG. 9A  are moved forward while being bent. 
         FIG. 10A  illustrates a state where a port is attached to the body wall of a patient while extending therethrough. 
         FIG. 10B  illustrates a state where the first tubular member of the cannula is inserted in and supported by the port in  FIG. 10A  while extending therethrough. 
         FIG. 100  illustrates a state where the gripping section of the medical treatment device is inserted in a body cavity via the cannula in  FIG. 10B . 
         FIG. 10D  illustrates a state where the medical treatment device in  FIG. 100  is bent together with the cannula. 
         FIG. 11   FIG. 11  illustrates a state where medical treatment devices are inserted in the body cavity of a patient with two manipulators being disposed parallel to each other. 
         FIG. 12   FIG. 12  illustrates a state where medical treatment devices are inserted in the body cavity of the patient with the two manipulators being oriented inward. 
         FIG. 13A  illustrates an example, as a modification of the handle in  FIG. 3 , in which an axis of a shaft and an axis of a rotation control section are aligned with each other. 
         FIG. 13B  illustrates an example, as another modification of the handle in  FIG. 3 , in which the axis of the shaft and the axis of the rotation control section are disposed on different axes that are parallel to each other. 
         FIG. 13C  illustrates an example, as another modification of the handle in  FIG. 3 , in which the axis of the shaft and the axis of the rotation control section are aligned with each other and in which a rotation axis of a swing control section is disposed in an open-close control section. 
         FIG. 14   FIG. 14  is a plan view illustrating the connection mechanism having a universal joint structure according to a first modification of the first embodiment of the present invention. 
         FIG. 15   FIG. 15  is a perspective view illustrating the connection mechanism having a component connection structure according to a second modification of the first embodiment of the present invention. 
         FIG. 16   FIG. 16  is a vertical sectional view of the front bearing and the rear bearing that use fastening tools according to another modification of the first embodiment of the present invention. 
         FIG. 17A  is a cross-sectional view illustrating the front bearing (or the rear bearing) that supports the first tubular member (or the second tubular member) by means of elastic wires according to a fourth modification of the first embodiment of the present invention. 
         FIG. 17B  illustrates a state where the first tubular member (or the second tubular member) in  FIG. 17A  is pivoted. 
         FIG. 18A  illustrates the front bearing (or the rear bearing) in  FIG. 17A , as viewed in the axial direction. 
         FIG. 18B  illustrates an example, as a modification of the front bearing (or the rear bearing) in  FIG. 17A , in which the first tubular member (or the second tubular member) is supported by four elastic wires uniformly arranged in the circumferential direction. 
         FIG. 18C  illustrates an example, as another modification of the front bearing (or the rear bearing) in  FIG. 17A , in which the first tubular member (or the second tubular member) is supported by four elastic wires, that is, two on each side, arranged parallel to each other in the radial direction. 
         FIG. 19A  is a plan view illustrating an example where two swing wires are provided in a medical treatment device according to a fifth modification of the first embodiment of the present invention. 
         FIG. 19B  illustrates a state where the gripping section in  FIG. 19A  is bent. 
         FIG. 19C  is a vertical sectional view of the shaft in  FIG. 19A , taken in a direction orthogonal to the longitudinal direction thereof. 
         FIG. 20A  is a plan view illustrating an example where four swing wires are provided in another medical treatment device according to the fifth modification of the first embodiment of the present invention. 
         FIG. 20B  illustrates a state where the gripping section in  FIG. 20A  is bent. 
         FIG. 20C  is a vertical sectional view of the shaft in  FIG. 19A , taken in a direction orthogonal to the longitudinal direction thereof. 
         FIG. 21A  illustrates the overall configuration of a medical treatment device according to a sixth modification of the first embodiment of the present invention. 
         FIG. 21B  illustrates a state where the gripping section in  FIG. 21A  is bent. 
         FIG. 22  illustrates the overall configuration of manipulators according to a seventh modification of the first embodiment of the present invention. 
         FIG. 23A  illustrates a reference example of the present invention in which a medical treatment device is manipulated in accordance with a laparoscopic procedure. 
         FIG. 23B  illustrates how the manipulators in  FIG. 22  are operated by a surgeon. 
         FIG. 24  illustrates an example where an affected site in the body cavity of a patient is treated by using the manipulators in  FIG. 22 . 
         FIG. 25  illustrates an example where affected sites located at different positions are treated by moving the gripping sections in  FIG. 24 . 
         FIG. 26  illustrates a state where two medical treatment devices are inserted into a single port by using the two manipulators in  FIG. 22 . 
         FIG. 27  illustrates a detector of a cannula and a manipulator according to a second embodiment of the present invention. 
         FIG. 28A  is a cross-sectional view of a driver of the cannula and the manipulator according to the second embodiment of the present invention. 
         FIG. 28B  is a vertical sectional view of the driver of the cannula and the manipulator according to the second embodiment of the present invention. 
         FIG. 29A  is a cross-sectional view illustrating how a medical treatment device is moved forward by the driver in  FIG. 28A . 
         FIG. 29B  is a cross-sectional view illustrating how the medical treatment device is moved rearward by the driver in  FIG. 28A . 
         FIG. 29C  is a cross-sectional view illustrating how the medical treatment device is rotated rightward by the driver in  FIG. 28A . 
         FIG. 29D  is a cross-sectional view illustrating how the medical treatment device is rotated leftward by the driver in  FIG. 28A . 
         FIG. 30A  illustrates an insertion section of a cannula and a manipulator according to a third embodiment of the present invention. 
         FIG. 30B  illustrates a support member and a parallel link of the cannula and the manipulator according to the third embodiment of the present invention. 
         FIG. 30C  illustrates a state where the insertion section in  FIG. 30A  is inserted in the support member and the parallel link in  FIG. 30B . 
         FIG. 31A  illustrates the overall configuration of a cannula according to a fourth embodiment of the present invention. 
         FIG. 31B  illustrates a state where the first tubular member and the second tubular member of the cannula in  FIG. 31A  are pivoted. 
         FIG. 32A  illustrates the overall configuration of a medical treatment device according to a fourth embodiment of the present invention. 
         FIG. 32B  illustrates the overall configuration of the medical treatment device in  FIG. 32A , as viewed from a different angle. 
         FIG. 33A  illustrates a state where the cannula and the medical treatment device according to the fourth embodiment of the present invention are linearly extended. 
         FIG. 33B  illustrates a state where the medical treatment device in  FIG. 33A  is bent together with the cannula. 
         FIG. 34A  illustrates a state where the medical treatment device is moved forward while the cannula and the medical treatment device in  FIG. 33A  are linearly extended. 
         FIG. 34B  illustrates a state where the medical treatment device in  FIG. 34A  is moved forward while being bent. 
         FIG. 35  is a cross-sectional view of a cannula according to a fifth embodiment of the present invention. 
         FIG. 36  illustrates a state where a medical treatment device in  FIG. 35  is bent in left and right directions. 
         FIG. 37  is a cross-sectional view illustrating a state where the angle of a rotor in the cannula according to the fifth embodiment of the present invention is changed. 
         FIG. 38  illustrates a state where the medical treatment device in  FIG. 35  is bent in up and down directions. 
         FIG. 39A  is a cross-sectional view of a cannula according to a sixth embodiment of the present invention. 
         FIG. 39B  illustrates a state where the first tubular member and the second tubular member of the cannula in  FIG. 39A  are pivoted. 
         FIG. 40A  illustrates a state where the first tubular member of the cannula in  FIG. 39A  is inserted in a trocar. 
         FIG. 40B  illustrates a state where the first tubular member and the second tubular member of the cannula in  FIG. 40A  are pivoted. 
         FIG. 41A  illustrates a state where the rear bearing of the cannula in  FIG. 39A  is fixed to the trocar by means of a trocar fastening tool. 
         FIG. 41B  illustrates a state where the first tubular member and the second tubular member of the cannula in  FIG. 41A  are pivoted. 
         FIG. 42A  is an enlarged view of the trocar fastening tool in  FIG. 41A . 
         FIG. 42B  illustrates a state where the angle of an insertion body is changed relative to arms in  FIG. 42A . 
         FIG. 42C  illustrates the trocar fastening tool in  FIG. 42A , as viewed in the thickness direction of the insertion body. 
         FIG. 42D  illustrates a state where a flip mechanism in  FIG. 42C  is closed. 
         FIG. 43  illustrates a manipulator equipped with a cannula system according to a seventh embodiment of the present invention. 
         FIG. 44A  is a front view of a cannula provided in the cannula system in  FIG. 43 . 
         FIG. 44B  is a side view of the cannula in FIG.  44 A. 
         FIG. 45  is a front view illustrating an example of a medical treatment device provided in the manipulator in  FIG. 43 . 
         FIG. 46A  is a front view illustrating one of the cannulas and one of the medical treatment devices in the manipulator in  FIG. 43 . 
         FIG. 46B  is a side view illustrating the cannula and the medical treatment device in  FIG. 46A . 
         FIG. 47  illustrates a state where handles are moved away from each other from the state in  FIG. 43 . 
         FIG. 48  illustrates a state where one of the gripping sections is moved forward from the state in  FIG. 47 . 
         FIG. 49  illustrates a state where the gripping section moved forward in the state in  FIG. 48  is rotated. 
         FIG. 50  illustrates the overall configuration of the manipulator in  FIG. 43 . 
         FIG. 51  illustrates a manipulator equipped with a cannula system according to an eighth embodiment of the present invention. 
         FIG. 52  illustrates the internal configuration of an angle changing mechanism of a cannula holder provided in the cannula system in  FIG. 51 . 
         FIG. 53  illustrates the internal configuration of the cannula holder and shows a state where movable bases are tilted from the state in  FIG. 52 . 
         FIG. 54  illustrates a method of fixing each support member to the corresponding movable base of the cannula holder in  FIG. 51 . 
         FIG. 55  illustrates a state where the handles are positioned away from each other by actuating the angle changing mechanism from the state in  FIG. 51 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     A cannula  3  and a manipulator  100  according to a first embodiment of the present invention will be described below with reference to the drawings. 
     As shown in  FIG. 1 , the manipulator  100  according to this embodiment includes a medical treatment device  1  used for preforming treatment inside the body cavity of a patient, and also includes the cannula  3  that ensures an insertion path used for inserting the medical treatment device  1  into the body cavity. 
     Examples of the medical treatment device  1  include gripping forceps, dissecting forceps, scissors, a high-frequency treatment device, an ultrasonic treatment device, and a needle holder. In this embodiment, gripping forceps shown in  FIGS. 2A and 2B  will be described as an example of the medical treatment device  1 . The medical treatment device  1  includes an elongated shaft  11 , a gripping section (distal-end treatment section)  13  connected to the distal end of the shaft  11  and having a pair of openable-closable gripping segments  12 , and a handle (proximal-end operating section)  15  that is connected to the proximal end of the shaft  11  and that controls the opening and closing of the gripping segments  12 . 
     In the following order from the proximal end, the shaft  11  is constituted of a first rigid segment  11 A formed of a rigid material, such as a pipe, a flexible segment  11 B, such as a coil tube, bendable in a direction intersecting the longitudinal direction, and a second rigid segment  11 C formed of a pipe similar to the first rigid segment  11 A. For example, the shaft  11  has a rigid-flexible-rigid (1:2:1) connection structure from the proximal end, such that the first rigid segment  11 A has a length of 180 mm, the flexible segment  11 B has a length of 350 mm, and the second rigid segment  11 C has a length of 180 mm. 
     The gripping section  13  includes a link mechanism (not shown) that connects the pair of gripping segments  12  to each other. The pair of gripping segments  12  open and close about the link mechanism acting as an axis. The gripping section  13  is connected to the handle  15  by means of a wire (not shown), such that three degrees of freedom, namely, the opening and closing (i.e., gripping) of the pair of gripping segments  12 , the rotation of the shaft  11  around the longitudinal axis, and the swinging of the shaft  11  in the direction intersecting the longitudinal axis, are controllable by using the handle  15 . 
     As shown in  FIG. 3 , the handle  15  includes an open-close control section  17  for opening and closing the pair of gripping segments  12 , a rotation control section  18  for rotating the gripping section  13  around the longitudinal axis of the shaft  11 , and a swing control section  19  for swinging the gripping section  13  in the direction intersecting the longitudinal axis of the shaft  11 . When the handle  15  is tilted in a yawing direction (i.e., left-right direction), the gripping section  13  is tilted by the same angle as the handle  15 . 
     As shown in  FIGS. 4A and 4B  and  FIGS. 5A and 5B , the cannula  3  includes a first tubular member  21 , a second tubular member  22 , and a third tubular member  23  that are ring-shaped and elongated and are arranged in series, a connection mechanism  25  that connects the first tubular member  21  and the second tubular member  22  to each other, a support member  30  that accommodates the connection mechanism  25  therein and supports the first tubular member  21  and the second tubular member  22  in a state where they extend through the support member  30 , and a parallel link  35  connected to the support member  30  and extending parallel to the second tubular member  22 . 
     The first tubular member  21 , the second tubular member  22 , and the third tubular member  23  respectively have a first through-hole  21   a , a second through-hole  22   a , and a third through-hole  23   a  through which the medical treatment device  1  is insertable. The first tubular member  21 , the second tubular member  22 , and the third tubular member  23 , in a linearly extended state, can allow the gripping section  13  of the medical treatment device  1  to continuously move into and out of the through-holes  21   a ,  22   a , and  23   a.    
     As shown in  FIGS. 6A and 6B , the connection mechanism  25  has a universal joint structure obtained by connecting two connection members  29  that are pivotable around rotation shafts  27  extending orthogonally to each other. With the connection mechanism  25 , the pivoting of the second tubular member  22  can be transmitted to the first tubular member  21  efficiently with high rigidity. Each of the connection members  29  has a through-hole  29   a  that engages with the first tubular member  21  or the second tubular member  22 . 
     The connection mechanism  25  arranges the first through-hole  21   a  of the first tubular member  21  and the second through-hole  22   a  of the second tubular member  22  in series by means of the two connection members  29  and connects the first tubular member  21  and the second tubular member  22  in a pivotable manner around an axis extending orthogonally to a plane including the axes of the through-holes  21   a  and  22   a.    
     The support member  30  has a front bearing  31  that supports the first tubular member  21  in a state where the first tubular member  21  extends therethrough, and also has a rear bearing  33  that supports the second tubular member  22  in a state where the second tubular member  22  extends therethrough. 
     The front bearing  31  and the rear bearing  33  are arranged on the same axis with a distance therebetween, and are secured by means of the support member  30 . 
     The front bearing  31  and the rear bearing  33  each have a spherical bearing structure shown in  FIGS. 7A and 7B . Moreover, the front bearing  31  and the rear bearing  33  each include a ring-shaped outer frame  32 A fixed to the support member  30  and a ring-shaped movable section  32 B engaged with the outer frame  32 A and supported in a movable manner by the outer frame  32 A. 
     The front bearing  31  and the rear bearing  33  respectively allow the first tubular member  21  and the second tubular member  22  to extend through the movable section  32 B, and support the first tubular member  21  and the second tubular member  22  in a three-dimensionally pivotable manner (i.e., pivotably movable manner) around an axis intersecting the longitudinal direction. 
     With each of the front bearing  31  and the rear bearing  33  having such a spherical bearing structure, the first tubular member  21  and the second tubular member  22  pivoted by any angle can be moved with similar low resistance regardless of the pivoting direction and the pivoting angle. 
     The front bearing  31  supports the first tubular member  21  in a longitudinally positioned state. Therefore, the distal end protruding from the front bearing  31  of the first tubular member  21 , that is, an insertion area to be inserted into the body cavity of a patient, constantly has a fixed length (cannula length). In contrast, the rear bearing  33  supports the second tubular member  22  in a slidable manner in the longitudinal direction. Therefore, when the first tubular member  21  and the second tubular member  22  are pivoted by the connection mechanism  25 , the second tubular member  22  slides in the longitudinal direction within the rear bearing  33 , thereby allowing for smooth movement. 
     The parallel link  35  includes three or more (four in this embodiment) fulcrum members  37  extending parallel to one another in the longitudinal direction of the second tubular member  22 , and also includes a blocking member  38  that blocks the other end of each of the fulcrum members  37 . 
     Each fulcrum member  37  has one end connected to the support member  30  in a three-dimensionally pivotable manner relative to the rear bearing  33  around an axis intersecting the axial direction, and the other end connected in a three-dimensionally pivotable manner relative to the blocking member  38  around an axis intersecting the axial direction. Accordingly, the four fulcrum members  37  can pivot three-dimensionally relative to the support member  30  and the blocking member  38  while maintaining their parallel positions. 
     The parallel link  35  is provided with a retainer  39  that maintains the four fulcrum members  37  and the second tubular member  22  parallel to one another. The retainer  39  is disposed at the blocking member  38  side of the parallel link  35  in the longitudinal direction and is fixed to the four fulcrum members  37 . For example, the retainer  39  is similar to the front bearing  31  and the rear bearing  33  in that it has a spherical bearing structure that allows the second tubular member  22  to extend therethrough and supports the second tubular member  22  in a three-dimensionally pivotable manner around an axis intersecting the longitudinal direction. 
     The third tubular member  23  has a third through-hole  21   c  that is disposed in series relative to the second through-hole  22   a  of the second tubular member  22  and has one end connected to the blocking member  38  of the parallel link  35 . With the parallel link  35 , the third tubular member  23  and the outer frame  32 A of the rear bearing  33  are connected to each other while the axes thereof are maintained in a parallel state. 
     The operation of the cannula  3  and the manipulator  100  according to this embodiment having the above-described configuration will be described below. 
     The cannula  3  supports the first tubular member  21  and the second tubular member  22 , connected to each other by the connection mechanism  25 , in a three-dimensionally pivotable manner around an axis intersecting the longitudinal direction by means of the front bearing  31  and the rear bearing  33  fixed to the support member  30 , so that when the first tubular member  21  and the second tubular member  22  are pivoted around the an axis in the connection mechanism  25 , the ends of the first tubular member  21  and the second tubular member  22  move in the same direction. 
     Therefore, as shown in  FIGS. 8A and 8B , when the handle  15  is moved in the direction orthogonal to the longitudinal direction of the shaft  11  in a state where the medical treatment device  1  is inserted in the cannula  3 , the first tubular member  21  and the second tubular member  22  pivot around the axis and move in the same direction due to the connection mechanism  25 , whereby the handle  15  and the gripping section  13  can be moved in the same direction. Furthermore, as shown in  FIGS. 9A and 9B , by moving the handle  15  forward, the shaft  11  is moved forward within the cannula  3 , so that the gripping section  13  can protrude by a large amount from the distal end of the first tubular member  21 . 
     The following description relates to a case where an affected site within the body cavity of a patient is treated by using the cannula  3  and the manipulator  100  according to this embodiment. 
     First, based on a procedure similar to that of normal laparoscopic surgery, an observation port (not shown) is attached in a penetrating state to the body wall of the patient, and an endoscope (not shown) is inserted into the body cavity through the port. 
     Then, the body wall is incised for forming a port installation opening (not shown), and a port  5  is set in the incision, as shown in  FIG. 10A . Subsequently, as shown in  FIG. 10B , the first tubular member  21  of the cannula  3  is inserted into the port  5  and is supported by the port  5  in a state where the first tubular member  21  extends therethrough, and the cannula  3  is fixed to a surgical table (not shown) by using a surgical arm  7 . Alternatively, a cannula holder (not shown) integrated with a surgical arm (not shown) may be set in the port  5  and be fixed to the surgical table, and the cannula  3  may be inserted into and fixed to the cannula holder. 
     It is desirable that the cannula  3  be inserted into the body cavity in a state where a trocar with a blunt tip is set in the cannula  3  so as not to damage the interior of the body with the tip of a cylinder. Moreover, when the cannula  3  is to be set, it is desirable that the central position of the front bearing  31  be disposed as close to the patient&#39;s body surface or the center between the body surface and the peritoneum as possible. Accordingly, the fulcrum to be used when operating the manipulator is located at the body surface or the center between the body surface and the peritoneum, so that the force applied to the patient&#39;s body tissue during the operation can be reduced, thereby reducing invasiveness. 
     Subsequently, a video image of the endoscope inserted in the body cavity is observed to confirm that the distal end of the first tubular member  21  is disposed at a location suitable for the procedure, and the support member  30  of the cannula  3  is fixed to the body wall. After the cannula  3  is fixed, the first tubular member  21 , the second tubular member  22 , and the third tubular member  23  are linearly extended, as shown in  FIG. 100 , and the gripping section  13  of the medical treatment device  1  is inserted through the third through-hole  23   a  in the third tubular member  23 . By linearly extending the first tubular member  21 , the second tubular member  22 , and the third tubular member  23 , the gripping section  13 , which is rigid, becomes insertable. Accordingly, the gripping section  13  of the medical treatment device  1  is introduced into the body cavity of the patient. 
     Then, appropriate treatment is performed by using the medical treatment device  1  inserted in the body cavity through the cannula  3 . For example, as shown in  FIG. 10D , treatment, such as surgery, is performed within the body cavity by operating the handle  15  for guiding the gripping section  13  as well as for controlling, for example, swinging, rotating, and gripping operations. In this case, the manipulator  100  according to this embodiment synchronizes the moving direction of the handle  15  with the moving direction of the gripping section  13 , so that the surgeon can perform the operation intuitively. 
     When the medical treatment device  1  is to be replaced in accordance with the progress of the procedure, the replacing process is performed in a state where the first tubular member  21 , the second tubular member  22 , and the third tubular member  23  of the cannula  3  are fixed in a linearly extended state, similarly to the inserting process. 
     As described above, in the cannula  3  and the manipulator  100  according to this embodiment, when the gripping section  13  inserted in the body cavity is to be directly manipulated by using the handle  15  disposed outside the body cavity, the surgeon can perform the operation intuitively by synchronizing the moving direction of the handle  15  with the moving direction of the gripping section  13 . 
     In this embodiment, it is desirable that manipulators  100  be tilted toward the affected site of the patient and the support members  30  be disposed such that the axes of the front bearings  31  are oriented toward the affected site within the body cavity, as shown in  FIG. 12 , as compared with a case where the manipulators  100  are disposed parallel to each other and the support members  30  are fixed such that the axes of the front bearings  31  are orthogonal to the body wall of the patient, as shown in  FIG. 11 . Accordingly, the substantial movable range of the gripping sections  13  can be increased. Moreover, an angular deviation occurring when the gripping sections  13  are moved forward and rearward may be reduced, so that the operation can be performed more naturally. 
     This embodiment relates to an example where two manipulators  100  are used simultaneously. Alternatively, for example, one manipulator  100  may be used alone. 
     Furthermore, in this embodiment, in order to allow for smooth insertion of the medical treatment device  1  into the cannula  3 , the cannula  3  may be provided with a locking mechanism that locks the tubular members  21 ,  22 , and  23  in a linearly extended state. In this case, for example, the locking mechanism may include a movable tubular member (not shown) at the second tubular member  22  side of the third tubular member  23  and may move the movable tubular member to cover the second tubular member  22 , thereby achieving the locked state. 
     Furthermore, in this embodiment, for example, the handle  15  may be configured such that the axis of the shaft  11  and the rotation axis of the rotation control section  18  are aligned with each other, as shown in  FIG. 13A . Accordingly, natural movement of the gripping section  13  can be achieved. Alternatively, as shown in  FIG. 13B , the axis of the shaft  11  and the rotation axis of the rotation control section  18  may be disposed on different axes that are parallel to each other. As another alternative, as shown in  FIG. 13C , the axis of the shaft  11  and the rotation axis of the rotation control section  18  may be aligned with each other, and the rotation axis of the swing control section  19  may be disposed in the open-close control section  17 . 
     This embodiment may be modified as follows. 
     In this embodiment, the connection mechanism  25  is described as having a universal joint structure obtained by connecting two connection members. As a first modification, for example, a connection mechanism  25 A may have a universal joint structure obtained by connecting three or more connection members  29  in series, as shown in  FIG. 14 . 
     The connection mechanism  25 A shown in  FIG. 14  includes three connection members  29 . The ends of the connection member  29  in the middle and the connection members  29  at the opposite sides thereof are connected in a pivotable manner around axes intersecting each other. Accordingly, the connected area between the first tubular member  21  and the second tubular member  22  can be pivoted by a large angle while maintaining high rigidity. Consequently, the operating range of the medical treatment device  1  can be increased. 
     As a second modification, for example, a connection mechanism  25 B has a component connection structure obtained by connecting a plurality of components  28 , as shown in  FIG. 15 . Accordingly, the medical treatment device  1  to be inserted into the through-holes  21   a  and  22   a  in the first tubular member  21  and the second tubular member  22  can be pivoted by a large fixed angle. 
     In this modification, the pivoting angle of the connection mechanism  25 B can be further increased by increasing the number of components  28 . Accordingly, the medical treatment device  1  can be maintained at a large fixed curvature even with a large pivoting angle. This enables smoother forward and rearward movement of the medical treatment device  1 , so that the medical treatment device  1  can be moved more finely. 
     As a third modification, for example, the connection mechanism  25  may have a tube structure like that of a flexible cylindrical tube. Accordingly, the connected area between the first tubular member  21  and the second tubular member  22  can be pivoted by a natural angle due to the connection mechanism  25 , thereby allowing for smoother movement of the medical treatment device  1 . Consequently, the gripping section  13  can be manipulated more finely. 
     Furthermore, cost reduction can be achieved, as compared with the case where the connection mechanism  25  has the component connection structure. Therefore, with the connection mechanism  25  being used alone, high cost efficiency can be expected when the connection mechanism  25  is to be replaced each time. The tube structure may be composed of, for example, a simple plastic material, such as PTFE. Moreover, for example, the structure may be increased in strength by covering the plastic material with a metallic mesh. 
     Furthermore, as an alternative to this embodiment in which the front bearing  31  and the rear bearing  33  each have a spherical bearing structure, at least one of the front bearing  31  and the rear bearing  33  may have a spherical structure. Moreover, for example, as shown in  FIG. 16 , fastening tools  34  through which the first tubular member  21  (or the second tubular member  22 ) is to extend may be disposed at opposite sides of the front bearing  31  (or the rear bearing  33 ) having the spherical structure, and the fastening tools  34  may be screwed to the first tubular member  21  (or the second tubular member  22 ). 
     As a fourth modification, as shown in  FIGS. 17A and 17B , the front bearing  31  and the rear bearing  33  may have a structure that pulls the first tubular member  21  and the second tubular member  22  from opposite sides evenly in the radial direction by means of elastic wires  41  extending in the radial direction, in place of the spherical structure. 
     In this case, the first tubular member  21  (or the second tubular member  22 ) and a ring-shaped frame  43  that surrounds the first tubular member  21  (or the second tubular member  22 ) may be connected by a plurality of elastic wires  41 . It is desirable that the elastic wires  41  be disposed at positions where they are point symmetrical with respect to the center point of the first tubular member  21  (or the second tubular member  22 ), that is, positions where they are disposed evenly in the circumferential direction of the first tubular member  21  (or the second tubular member  22 ), so that the force applied to the first tubular member  21  (or the second tubular member  22 ) is as uniform as possible during the pivoting motion. 
     For example, if two elastic wires  41  are used, as shown in  FIG. 18A , the front bearing  31  (or the rear bearing  33 ) can have an extremely small area. In particular, reduced invasiveness can be achieved by using two elastic wires  41  in the front bearing  31  that needs to be brought into contact with the patient&#39;s body surface. 
     Alternatively, as shown in  FIG. 18B , three or more elastic wires  41  may be disposed uniformly apart from one another in the circumferential direction, so that the resistance acting on the first tubular member  21  (or the second tubular member  22 ) may be made more uniform during the pivoting motion. As another alternative, as shown in  FIG. 18C , in order to achieve both thickness reduction of the front bearing  31  (or the rear bearing  33 ) and a uniform force applied to the first tubular member  21  (or the second tubular member  22 ), two elastic wires  41  may be connected to each side of the first tubular member  21  (or the second tubular member  22 ) in the radial direction, such that the first tubular member  21  (or the second tubular member  22 ) is pulled from opposite sides by four elastic wires  41 . 
     In this modification, the elastic wires  41  used may be composed of steel. Moreover, if the elastic wires  41  used have a low elastic modulus, the elastic wires  41  may be connected with springs (not shown) for assisting with the expansion and contraction during the pivoting motion. Alternatively, a plastic material, such as polyimide, having both stretchability and strength may be used in place of springs. As another alternative, the first tubular member  21  (or the second tubular member  22 ) and the frame  43  may be connected by a membrane structure having elasticity, such as a structure composed of rubber, in place of the elastic wires. 
     As a fifth modification, for example, as shown in  FIGS. 19A to 19C , the medical treatment device  1  may include two swing wires  45 A and  45 B that cause the gripping section  13  to move in a swinging motion, and a single grip-rotation wire  47  that causes the gripping section  13  to move in a rotating motion and a gripping motion. In this case, as shown in  FIG. 19C , the handle  15  and the gripping section  13  may be connected by these wires  45 A,  45 B, and  47 . 
     Furthermore, the swing wires  45 A and  45 B and the grip-rotation wire  47  may be inserted into coil tubes  49 , the grip-rotation wire  47  may be disposed in the middle of the interior of the shaft  11 , and the swing wires  45 A and  45 B may be respectively disposed at the opposite sides of the grip-rotation wire  47  in the radial direction. Accordingly, the two swing wires  45 A and  45 B can cause the gripping section  13  to bend (yaw or pitch) in two directions intersecting the longitudinal direction. 
     In this modification, as shown in  FIGS. 20A to 20C , four swing wires  45 A,  45 B,  45 C, and  45 D may be used. In this case, the four swing wires  45 A,  45 B,  45 C, and  45 D may be individually inserted into the coil tubes  49 , and may be disposed uniformly apart from one another in the circumferential direction around the grip-rotation wire  47  inside the shaft  11 . Accordingly, the four swing wires  45 A,  45 B,  45 C, and  45 D can be bent (yawed and pitched) in four directions intersecting the longitudinal direction. 
     In this modification, the shaft  11  may have a second flexible segment  11 B with a component connection structure composed of a flexible material between the second rigid segment  11 C and the gripping section  13 . Alternatively, the flexible segment  11 B may have a component connection structure. 
     Furthermore, the medical treatment device  1  may be multi-degree-of-freedom forceps in which the gripping section  13  bends and rotates by being driven by a driving force via an elastic wire extending through the shaft  11 . By electrically driving the gripping section  13 , the operational amount of the handle  15  can be made to match the rotational amount and the bending amount of the gripping section  13  even when the slide resistance of the elastic wire for driving the gripping section  13  changes due to a change in the pivoting angle of the connection mechanism  25 . Moreover, the amount of force applied to the handle  15  when being operated can be maintained constant and small, thereby allowing for an accurate and high-quality procedure. 
     As a sixth modification, for example, as shown in  FIGS. 21A and 21B , the shaft  11  may have a second flexible segment  14 C, such as a bendable coil tube composed of a flexible material, in place of the second rigid segment  11 C. In this case, the second flexible segment  14 C may have a bending strength higher than that of the flexible segment  11 B. Moreover, the second flexible segment  14 C may have a length of 180 mm, similar to the second rigid segment  11 C, and the shaft  11  may have a flexible-flexible-rigid (1:2:1) connection structure from the proximal end. 
     With the distal end of the shaft  11  being bendable due to the second flexible segment  14 C in this manner, the forceps are replaceable even in a state where the cannula  3  is bent. In this case, if the distal end of the shaft  11  that is to be exposed to the body cavity from the first tubular member  21  has low elasticity, the distal end of the shaft  11  flexes during an operation, thus making it difficult to achieve the movement desired by the operator. On the other hand, unless the area of the shaft  11  that is bent by the connection mechanism  25  is reduced in elasticity so that the area bends easily, the resistance during the operation increases, thus making it difficult to achieve the movement desired by the operator. By relatively increasing the elasticity of the second flexible segment  14 C at the distal end of the shaft  11  that is to be exposed to the body cavity and relatively reducing the elasticity of the flexible segment  11 B in the central area that does not protrude from the shaft  11 , such conflicting issues can be resolved. 
     As a seventh modification, as shown in  FIG. 22 , the rear bearing  33  may be fixable after changing the angle thereof around a pivot axis intersecting the axis of the outer frame  32 A. Accordingly, the axis of the outer frame  32 A of the rear bearing  33  can be oriented in a direction different from the axis of the outer frame  32 A of the front bearing  31 . 
     In this case, one end of each fulcrum member  37  of the parallel link  35  may be directly connected to the rear bearing  33  in a three-dimensionally pivotable manner around an axis orthogonal to the axial direction. Moreover, the rear bearing  33  may be preliminarily changed in angle around the pivot axis before the procedure is performed, and may be fixed to the changed angle during the procedure. 
     Accordingly, the first tubular member  21  and the second tubular member  22  can be pivoted without being limited by the pivoting angle range of the front bearing  31  or the rear bearing  33 . Furthermore, the same angular relationship can be constantly maintained between the rear bearing  33  and the handle  15 . Consequently, the angle between the first tubular member  21  that is to be brought into contact with the body surface and the handle  15  can be freely adjusted. 
     With regard to the positioning of a port in laparoscopic surgery, it is extremely important that the gripping section  13  be set at an appropriate angle (i.e., triangulation) relative to the site to be treated. With this triangulation, the procedure can be carried out appropriately and accurately. On the other hand, since the position of the handle  15  is set in accordance with the position of the port  5 , for example, the surgeon may sometimes stretch both arms above the body of the patient to bring the handle  15  to the surgeon&#39;s hands, such as when the handle  15  is positioned toward the trunk of the body. In such a case, the surgeon is in a physiologically poor posture and may experience fatigue if the procedure involves long hours, possibly resulting in a low-quality procedure. 
     As a reference example, for example, in a normal laparoscopic procedure, as shown in  FIG. 23A , if the pelvic cavity is to be treated, the surgeon may sometimes need to perform the treatment in a posture that requires an extremely large load by stretching his/her arm straight. In contrast, in this modification, the rear bearing  33  is pivoted around the pivot axis intersecting the axis, so that the surgeon can bend his/her arms and perform the procedure in a comfortable posture, as shown in  FIG. 23B . 
     Furthermore, according to this modification, as shown in  FIGS. 24 and 25 , by pivoting the rear bearing  33  around the pivot axis intersecting the axis, different positions within the body cavity can be accessed with the gripping section  13  without having to change the position and the angle of the handle  15 , that is, without the surgeon changing his/her the posture. Consequently, a wide range within the body cavity can be treated quickly and readily. 
     Furthermore, according to this modification, the support member  30  may be set at an angle relative to the body wall of the patient, or the rear bearing  33  may be pivoted around the pivot axis intersecting the axis, so that even when a plurality of medical treatment devices  1  are inserted into a single port  5  by using a plurality of manipulators  100 , as shown in  FIG. 26 , the operating space of the surgeon can be ensured, whereby the procedure can be performed appropriately without interference between the handles  15 . 
     Second Embodiment 
     Next, a cannula  103  and a manipulator  100  according to a second embodiment of the present invention will be described. 
     As shown in  FIGS. 27 and 28 , the cannula  103  and the manipulator  100  according to this embodiment are different from the first embodiment in being provided with a detector  50  that detects the amount of rotation and the amount of forward-rearward movement of the medical treatment device  1  manipulated using the handle  15 , and a driver  55  that causes the medical treatment device  1  inserted in the first tubular member  21  to move forward and rearward in the longitudinal direction and to rotate around the axis in accordance with the amount of rotation and the amount of forward-rearward movement detected by the detector  50 . 
     In the following description, sections having configurations identical to those of the cannula  3  and the manipulator  100  according to the first embodiment are given the same reference signs, and descriptions thereof will be omitted. 
     As shown in  FIG. 27 , the detector  50  includes a rotational-amount detecting roller  51  that comes into contact with the medical treatment device  1  inserted in the third tubular member  23  so as to be rotated by friction caused as a result of rotation of the medical treatment device  1 , a forward-rearward-movement-amount detecting roller  52  that comes into contact with the medical treatment device  1  inserted in the third tubular member  23  so as to be rotated by friction caused as a result of forward or rearward movement of the medical treatment device  1 , and detectors  53 A and  53 B that detect the rotational amounts and the rotational directions of the rotational-amount detecting roller  51  and the forward-rearward-movement-amount detecting roller  52 . 
     The rotational-amount detecting roller  51  is rotatable around an axis parallel to the axis of the third tubular member  23 . 
     The forward-rearward-movement-amount detecting roller  52  is rotatable around an axis orthogonal to the axis of the third tubular member  23 . 
     The detectors  53 A and  53 B transmit the detected rotational amounts and the detected rotational directions of the rotational-amount detecting roller  51  and the forward-rearward-movement-amount detecting roller  52  to the driver  55 . 
     As shown in  FIGS. 28A and 28B , the driver  55  includes motors  57 A and  57 B that are accommodated in the support member  30  and that rotate around predetermined rotation axes intersecting the longitudinal direction of the first tubular member  21  and parallel to each other, rollers  59 A and  59 B connected to the motors  57 A and  57 B and rotated around the same axes as the motors  57 A and  57 B, and a controller  56  that drives the motors  57 A and  57 B in accordance with the rotational amounts and the rotational directions of the rotational-amount detecting roller  51  and the forward-rearward-movement-amount detecting roller  52  transmitted from the detectors  53 A and  53 B. 
     The motor  57 A and the roller  59 A, as well as the motor  57 B and the roller  59 B, are provided between the front bearing  31  and the connection mechanism  25  and are disposed with the first tubular member  21  interposed therebetween in the radial direction. 
     The motor  57 A and the motor  57 B are capable of rotating independently of each other. 
     The roller  59 A and the roller  59 B are disposed at an angle of 45 degrees relative to the first tubular member  21  and are brought into contact with the shaft  11  of the medical treatment device  1 . Furthermore, the roller  59 A and the roller  59 B rotate outward to cause the shaft  11  to move forward, as shown in  FIG. 29A , and rotate inward to cause the shaft  11  to move rearward, as shown in  FIG. 29B . Moreover, the roller  59 A and the roller  59 B rotate counterclockwise with respect to the advancing direction to cause the shaft  11  to rotate rightward with respect to the advancing direction, as shown in  FIG. 29C , and rotate clockwise with respect to the advancing direction to cause the shaft  11  to rotate leftward with respect to the advancing direction, as shown in  FIG. 29D . 
     Based on the amount of rotation and the amount of forward-rearward movement transmitted from the detectors  53 A and  53 B of the detector  50 , the controller  56  causes the roller  59 A and the roller  59 B to rotate in rotational directions corresponding to the rotational directions of the rotational-amount detecting roller  51  and the forward-rearward-movement-amount detecting roller  52 , and causes the roller  59 A and the roller  59 B to rotate by rotational amounts equal to the rotational amounts of the rotational-amount detecting roller  51  and the forward-rearward-movement-amount detecting roller  52 . 
     In the cannula  103  and the manipulator  100  according to this embodiment having the above-described configuration, the detector  50  and the driver  55  can cause the gripping section  13  of the medical treatment device  1  to actually rotate and move forward and rearward by an amount of rotation and an amount of forward-rearward movement that match the amount of rotation and the amount of forward-rearward movement of the medical treatment device  1  manipulated by using the handle  15 . 
     Accordingly, even when the slide resistance of the medical treatment device  1  changes due to a change in the pivoting angle of the connection mechanism  25 , the operational amount of the handle  15  can be made to match the amount of movement of the gripping section  13 , and the amount of force applied to the handle  15  when being operated can be maintained constant and small, thereby allowing for an accurate and high-quality procedure. 
     Third Embodiment 
     Next, a cannula  203  and a manipulator  100  according to a third embodiment of the present invention will be described. 
     As shown in  FIGS. 30A to 30C , the cannula  203  and the manipulator  100  according to this embodiment are different from the first embodiment in being provided with an insertion section  60  having the first tubular member  21 , the second tubular member  22 , and the third tubular member  23  as a single unit, and in that the insertion section  60 , the support member  30 , and the parallel link  35  have isolated structures. 
     In the following description, sections having configurations identical to those of the cannulas  3  and  103  and the manipulator  100  according to the first and second embodiments are given the same reference signs, and descriptions thereof will be omitted. 
     In the insertion section  60 , an area corresponding to the first tubular member  21  is composed of a rigid material, and areas corresponding to the second tubular member  22  and the third tubular member  23  are composed of a flexible material. 
     The parallel link  35  is provided with a tubular member  61  into which the insertion section  60  is insertable, and the insertion section  60  can be secured by being inserted into the tubular member  61 . 
     In the cannula  203  according to this embodiment having the above-described configuration, the insertion section  60  alone can be removed so that the insertion section  60  can be cleaned and sterilized. Moreover, the support member  30  and the parallel link  35  may be used continuously, whereas the insertion section  60  may be replaced after each use. 
     Fourth Embodiment 
     Next, a cannula  303  and a manipulator  100  according to a fourth embodiment of the present invention will be described. 
     As shown in  FIGS. 31A and 31B , the cannula  303  and the manipulator  100  according to this embodiment are different from the first to third embodiments in being not provided with the parallel link  35  and the third tubular member  23 . 
     In the following description, sections having configurations identical to those of the cannulas  3 ,  103 , and  203  and the manipulator  100  according to the first to third embodiments are given the same reference signs, and descriptions thereof will be omitted. 
     As shown in  FIGS. 32A and 32B , in the medical treatment device  1 , the first rigid segment  11 A, the flexible segment  11 B, and the second rigid segment  11 C have the same length, and are slightly shorter than the first tubular member  21 . The handle  15  and the second rigid segment  11 C are connected by a joint member  65  pivotable in up-down and left-right directions. With the joint member  65 , the handle  15  can be maintained at a desired angle, regardless of the angle of the second rigid segment  11 C. 
     The operation of the cannula  303  and the manipulator  100  having the above-described configuration will now be described. 
     With regard to the cannula  303  and the manipulator  100  according to this embodiment, when the handle  15  is moved in a direction intersecting the longitudinal direction of the shaft  11  in a state where the medical treatment device  1  is inserted in the cannula  303 , as shown in  FIGS. 33A and 33B , the gripping section  13  can be moved in the moving direction of the handle  15 . Furthermore, when the handle  15  is moved forward, the gripping section  13  can be moved forward, as shown in  FIGS. 34A and 34B . 
     As described above, in the cannula  303  and the manipulator  100  according to this embodiment, the pivotable joint member  65  allows the handle  15  to be maintained at a fixed angle even when the angle of the second rigid segment  11 C is changed. Therefore, the moving direction of the handle  15  can be synchronized with the moving direction of the gripping section  13 , so that the surgeon can perform the operation intuitively. 
     Fifth Embodiment 
     Next, a cannula  403  and a manipulator  100  according to a fifth embodiment of the present invention will be described. 
     As shown in  FIGS. 35 and 36 , the cannula  403  and the manipulator  100  according to this embodiment are different from the first to fourth embodiments in that the front bearing  31  is offset from the axis of the first tubular member  21 . 
     In the following description, sections having configurations identical to those of the cannulas  3 ,  103 ,  203 , and  303  and the manipulator  100  according to the first to fourth embodiments are given the same reference signs, and descriptions thereof will be omitted. 
     In the cannula  403 , the front bearing  31  includes a rotor  71  disposed away from the first tubular member  21  and rotatable around a rotation axis intersecting the axis of the rear bearing  33 , a pair of first links  73  each having one end connected to the rotor  71  and extending parallel to the first tubular member  21  and to each other, and a pair of second links  75  extending parallel to each other and each having one end connected to the corresponding first link  73  and the other end connected to the first tubular member  21 . 
     The rotor  71  and the first links  73 , the first links  73  and the second links  75 , and the second links  75  and the first tubular member  21  are connected to each other in a pivotable manner around a pivot axis orthogonal to the rotation axis of the rotor  71 . 
     The operation of the cannula  403  having the above-described configuration will now be described. 
     As shown in  FIGS. 35 and 36 , the first links  73  and the second links  75  are caused to pivot around the pivot axis, so that the first tubular member  21  can be pivoted in the same plane as the first links  73  and the second links  75 . Moreover, by rotating the rotor  71  around the rotation axis, the first tubular member  21  can be pivoted in a plane intersecting the first links  73  and the second links  75 . 
     In this case, the front bearing  31  is connected to the first tubular member  21  by means of the second links  75 , so that the first tubular member  21  can be supported in a three-dimensionally pivotable manner without having to dispose a bearing structure on the axis of the first tubular member  21 . Accordingly, the first tubular member  21  can be inserted into the body cavity through a normal trocar to be attached to the body wall of the patient. Moreover, a pivot point (indicated with an X in the drawing) where the first tubular member  21  pivots three-dimensionally can be disposed at the center of the body wall of the patient in the thickness direction, so that a procedure with reduced invasiveness can be achieved. 
     As an alternative to this embodiment in which the first links  73  are a pair of shafts that are parallel to each other, a first link  73  constituted of a single shaft is also possible, as shown in  FIGS. 37 and 38 . Even in such a case, advantages similar to those in the case where the first links  73  are constituted of two parallel shafts are achieved. 
     Sixth Embodiment 
     Next, a cannula  503  and a manipulator  100  according to a sixth embodiment of the present invention will be described. 
     As shown in  FIGS. 39A and 39B , the cannula  503  according to this embodiment is different from the first to fifth embodiments in that the support member  30  and the front bearing  31  are not provided, and that the first tubular member  21  is inserted in a trocar  9  attached to the body wall of the patient and is supported the trocar  9  in a state where the first tubular member  21  extends therethrough, as shown in  FIGS. 40A and 40B . 
     In the following description, sections having configurations identical to those of the cannulas  3 ,  103 ,  203 ,  303 , and  403  and the manipulator  100  according to the first to fifth embodiments are given the same reference signs, and descriptions thereof will be omitted. 
     In this embodiment, as shown in  FIGS. 41A and 41B , the parallel link  35  includes a blocking member  36  that blocks one end of each fulcrum member  37  and secures the rear bearing  33 , and also includes a trocar fastening tool  80  that fixes the rear bearing  33  to the body wall of the patient via the trocar  9 . 
     As shown in  FIGS. 41A, 41B, 42A, and 42B , the trocar fastening tool  80  includes a pair of arms  81  each having one end fixed to the parallel link  35 , and a trocar insertion section  85  that is connected to the other end of each of the pair of arms  81 , secures the trocar  9  by having the trocar  9  extending therethrough, and is to be attached to the body surface of the patient. In the drawings, only one of the arms  81  is shown. 
     The pair of arms  81  extend in the longitudinal direction of the cannula  3  and are disposed parallel to each other with the connection mechanism  25  interposed therebetween. Each arm  81  has one end connected to the blocking member  36  of the parallel link  35  by means of a screw, and the other end attached to the trocar insertion section  85  in a pivotable manner by means of a hinge  83 . 
     As shown in  FIGS. 42C and 42D , the trocar insertion section  85  includes a plate-shaped insertion body  87  having a recessed cutout  87   a  into which the trocar  9  is fittable, and also includes a flip mechanism  89  that partially blocks the cutout  87   a  in the insertion body  87  and secures the trocar  9  in the cutout  87   a  in a state where the trocar  9  extends therethrough. 
     The insertion body  87  is attached to the other end of each of the pair of arms  81  by means of the hinge  83  and can change the angle relative to the arms  81  by means of the hinge  83 . The insertion body  87  is attached to the body surface of the patient so as to support the parallel link  35  via the arms  81 . 
     The cutout  87   a  extends from an edge of the insertion body  87  to near the center thereof, and has a width that is slightly larger than the diameter of the trocar  9 . Moreover, the terminal end of the cutout  87   a  has a substantially circular-arc shape that conforms to the outer peripheral shape of the trocar  9 . 
     The flip mechanism  89  is capable of blocking the opening of the cutout  87   a . The flip mechanism  89  has a recess  89   a  with a substantially circular-arc shape that conforms to the outer peripheral shape of the trocar  9 . The flip mechanism  89  blocks the opening of the cutout  87   a  so that the recess  89   a  limits the cutout  87   a  to a through-hole through which the trocar  9  is extendable. Specifically, when the flip mechanism  89  opens, the trocar  9  can be fitted into the cutout  87   a . When the flip mechanism  89  closes in a state where the trocar  9  is fitted in the cutout  87   a , the trocar  9  can be fixed in the cutout  87   a  in a state where the trocar  9  extends therethrough. 
     It is more preferable that the cutout  87   a  be large enough to have a gap with respect to the trocar  9  when the trocar  9  is fitted in the cutout  87   a  and the flip mechanism  89  is closed. By having a gap between the cutout  87   a  and the trocar  9 , the degree of freedom for the pivoting motion of the trocar  9  can be ensured, thereby achieving improved operability. 
     The operation of the cannula  503  and the manipulator  100  having the above-described configuration will now be described. 
     When an affected site within the body cavity of a patient is to be treated by using the cannula  503  and the manipulator  100  according to this embodiment, the first tubular member  21  of the cannula  3  is first inserted into the trocar  9  attached to the body wall of the patient. Then, the trocar  9  is fitted into the cutout  87   a  in the insertion body  87  of the trocar fastening tool  80 , the flip mechanism  89  is closed, the insertion body  87  is set on the body surface of the patient, and the cannula  3  is fixed by using, for example, a surgical arm (not shown). 
     Accordingly, even if the cannula  503  is not provided with the front bearing  31 , a fixed relative position of the pivot point where the first tubular member  21  pivots three-dimensionally can always be maintained. Therefore, this configuration is similar to each of the above-described embodiments in that the moving direction of the handle  15  can be synchronized with the moving direction of the gripping section  13 , so that the surgeon can manipulate the medical treatment device  1  intuitively by using the trocar  9  as a fulcrum. 
     As an alternative to this embodiment in which the trocar fastening tool  80  is provided, it is possible to operate the cannula  503  without the trocar fastening tool  80 . If the trocar fastening tool  80  is not provided, for example, the distance between the body surface and the blocking member  36  may be measured and adjusted such that the distance is fixed when the cannula  503  is set on the body surface of the patient. 
     Although the embodiments of the present invention have been described above in detail with reference to the drawings, specific configurations are not limited to these embodiments, and design alterations are also included so long as they do not depart from the scope of the invention. For example, the present invention is not limited to each of the above-described embodiments and modifications and may be applied to an embodiment obtained by appropriately combining these embodiments and modifications; it is not particularly limited. 
     Furthermore, as an alternative to each of the above-described embodiments in which gripping forceps are described as an example of the medical treatment device  1 , other examples include dissecting forceps, scissors, a high-frequency treatment device, an ultrasonic treatment device, a needle holder, a treatment tool used in laparoscopic surgery, such as a clip for sealing a blood vessel, a stapler for cutting and sealing tissue, a basket for collecting tissue, or a water suction tube, and an observation device, such as an endoscope. 
     Next, a cannula system  600  according to a seventh embodiment of the present invention will be described below with reference to the drawings. 
     As shown in  FIG. 43 , the cannula system  600  according to this embodiment includes two cannulas  603  and a cannula holder  90  that supports the cannulas  603 . 
     As shown in  FIGS. 44A and 44B , each cannula  603  is similar to the cannula  3  in  FIG. 4A  in that it includes a first tubular member  21 , a second tubular member  22 , and a third tubular member  23  that are ring-shaped and elongated and are arranged in series, a connection mechanism  25  that connects the first tubular member  21  and the second tubular member  22  to each other, a support member  30  that is located at the opposite sides of the connection mechanism  25  and that supports the first tubular member  21  and the second tubular member  22  in a state where they extend through the support member  30 , and a parallel link  35  that is connected to the support member  30  and extends parallel to the second tubular member  22 . 
     This embodiment is different from the cannula  3  according to the first embodiment in that the first tubular member  21  is bent in one direction. 
     Furthermore, as shown in  FIG. 45 , a medical treatment device  601  used together with the cannula system  600  according to this embodiment includes an elongated shaft  611 , a gripping section (distal-end treatment section)  613  connected to the distal end of the shaft  611  and having a pair of openable-closable gripping segments  612 , and a handle (proximal-end operating section)  615  that is connected to the proximal end of the shaft  611  and that controls the opening and closing of the gripping segments  612 . 
     In the following order from the proximal end, the shaft  611  is constituted of a rigid segment  611 A formed of a rigid material, such as a pipe, and a semi-rigid segment  611 B formed of a plastic pipe that is bendable in a direction intersecting the longitudinal direction. As shown in  FIGS. 46A and 46B , the semi-rigid segment  611 B can be freely bent at the connection mechanism  25 , and bends in conformity to the shape of the first tubular member  21  within the bent first tubular member  21 . 
     As shown in  FIG. 43 , in a state where the third tubular members  23  of the two cannulas  603  are disposed close to each other, the cannula holder  90  secures the support members  30  of the two cannulas  603  to achieve a positional relationship where the first tubular member  21  of one of the cannulas  603  bends toward the other cannula  603  such that the two first tubular members  21  intersect each other. 
     The operation of the cannula system  600  according to this embodiment will be described below. 
     When the medical treatment devices  601  are inserted into the two cannulas  603  of the cannula system  600  according to this embodiment, the bent first tubular members  21  intersect each other in a state where the third tubular members  23  are disposed closest to each other, as shown in  FIG. 43 , such that the two gripping sections  613  are disposed at different positions. From this state, the third tubular members  23  are translationally moved away from each other, as shown in  FIG. 47 , so that the intersecting state between the first tubular members  21  becomes canceled, whereby the two gripping sections  613  can be disposed close to each other. 
     Specifically, in the cannula system  600  according to this embodiment, the two gripping sections  613  are brought close to each other in a state where the handles  615  of the two medical treatment devices  601  are positioned away from each other, so that when the same target site is to be treated by using the two medical treatment devices  601 , interference between the handles  615  can be prevented. This is advantageous in that reduced workability for the surgeon can be prevented. 
     In this cannula system  600 , an open-close control section  617  of each handle  615  may be operated to open and close the pair of gripping segments  612  of each gripping section  613 , as shown in  FIG. 43 , the handle  615  may be moved in the longitudinal direction of the third tubular member  23  to move the gripping section  613  forward and rearward, as shown in  FIG. 48 , the handle  615  may be moved in the direction intersecting the longitudinal axis of the third tubular member  23  to move the gripping section  613  in the same direction as the handle  615 , as shown in  FIG. 47 , and the handle  615  may be rotated around the longitudinal axis of the third tubular member  23  to rotate the gripping section  613  around the longitudinal axis of the semi-rigid segment  611 B, as shown in  FIG. 49 . Furthermore, the handle  615  may be tilted in the yawing direction (i.e., left-right direction) to tilt the gripping section  613  by the same angle as the handle  615 . 
     Furthermore, as shown in  FIG. 50 , in a manipulator  100  equipped with the cannula system  600  according to this embodiment, the cannula holder  90  may be fixed to a body insertion port  91 , such as a trocar, and forceps drivers  618  connected to the handles  615  of the medical treatment devices  601  may be driven by being controlled by the controller  56 . 
     Next, a cannula system  700  according to an eighth embodiment of the present invention will be described below with reference to the drawings. 
     The cannula system  700  according to this embodiment is different from the cannula system  600  according to the seventh embodiment with respect to the bent shape of the first tubular members  21  of two cannulas  703 , as well as the cannula holder  90 . 
     As shown in  FIG. 51 , in this embodiment, the first tubular members  21  of the two cannulas  703  are bent in the shape of the letter S. The first tubular member  21  of each of the two cannulas  703  is supported by the cannula holder  90  in a position in which the first tubular member  21  bends away from the other cannula  703  and then bends toward the other cannula  703  from the proximal end toward the distal end. Accordingly, as shown in  FIG. 51 , the two gripping sections  613  are disposed away from each other when the two handles  615  are positioned closest to each other. 
     The cannula holder  90  includes an angle changing mechanism  92  that changes the tilt angle of each support member  30  around an axis orthogonal to the direction in which the front bearing  31  and the rear bearing  33 , provided in the support member  30  of each cannula  703  supported by the cannula holder  90 , are separated from each other. 
     For example, as shown in  FIG. 52 , the angle changing mechanism  92  includes two movable bases  94  supported in a pivotable manner around parallel axes relative to a holder base  93 , a handle  95  supported by the holder base  93  in a rotatable manner around an axis parallel to the axes of the movable bases  94 , a pinion gear  96  fixed to the handle  95 , a pair of slide members  97  moved rectilinearly in the direction in which the movable bases  94  are separated from each other, and rack gears  98  that are provided in the slide members  97  and that mesh with the pinion gear  96 . 
     The slide members  97  and the movable bases  94  are connected by inserting pins  99  provided in the movable bases  94  into long holes  97 A provided in the slide members  97 . Accordingly, as shown in  FIG. 53 , when the operator rotates the handle  95 , the pinion gear  96  rotates, and the rotation of the handle  95  is converted into a rectilinear motion of the slide members  97  by the rack gears  98  meshed with the pinion gear  96 , whereby the movable bases  94  are pivoted away from each other. 
     With the support member  30  of each cannula  703  being fixed to the corresponding movable base  94 , the tilt angle of the cannula  703  can be changed by simply rotating the handle  95 . As shown in  FIG. 54 , the support member  30  may be fixed to the movable base  94  in a one-touch operation by fitting a dovetail section  30 A provided in the support member  30  into a dovetail groove  94 A fixed to the movable base  94 . 
     In the cannula system  700  according to this embodiment, the handle  95  of the cannula holder  90  is operated from a state where the second tubular members  22  of the two cannulas  703  are parallel to each other, as shown in  FIG. 51 , so that the tilt angle of the support members  30  can be changed in the direction in which the third tubular members  23  of the two cannulas  703  move away from each other, as shown in  FIG. 55 , whereby an overlapping region (indicated with an oblique line) between the movable ranges of the gripping sections  613  of the two medical treatment device  601  can be increased. Consequently, this is advantageous in that treatment can be performed using the two medical treatment devices  601  over a wide range. 
     Furthermore, the two gripping sections  613  can be brought close to each other in a state where the handles  615  of the two medical treatment devices  601  are positioned away from each other by the angle changing mechanism  92  of the cannula holder  90 . Consequently, when the same target site is to be treated by using the two medical treatment devices  601 , interference between the handles  615  can be prevented, thereby preventing reduced workability for the surgeon. 
     The above-described embodiment also leads to the following aspects. 
     A first aspect of the present invention provides a cannula including a first tubular member having a first longitudinal axis, a second tubular member having a second longitudinal axis, a connection mechanism that connects the first tubular member and the second tubular member in series, and a rear bearing that supports the second tubular member in a three-dimensionally pivotable manner around an axis intersecting the second longitudinal axis. The first tubular member has a first through-hole into which a flexible and elongated medical treatment device is insertable, and is supported by a trocar in a state where the first tubular member extends through the trocar attached to a body wall of a patient. The second tubular member has a second through-hole into which the medical treatment device is insertable. The connection mechanism connects the first tubular member and the second tubular member in a pivotable manner around an axis orthogonal to a plane including the first longitudinal axis and the second longitudinal axis. 
     According to this aspect, the first tubular member and the second tubular member connected by the connection mechanism in a pivotable manner around the axis orthogonal to the plane including the first axis and the second axis are supported by the trocar and the rear bearing in a three-dimensionally pivotable manner around the axis intersecting the first longitudinal axis or the second longitudinal axis. Therefore, when the first tubular member and the second tubular member are pivoted around the axis by the connection mechanism, the other end of the first tubular member and the other end of the second tubular member move in the same direction. 
     Furthermore, the first tubular member and the second tubular member are connected by the connection mechanism with the first through-hole and the second through-hole being disposed in series, so that the medical treatment device can be introduced into the body cavity through the through-holes of the first tubular member and the second tubular member in a state where the first tubular member is supported by the trocar while extending therethrough. Then, the first tubular member and the second tubular member are pivoted around the axis by the connection mechanism, so that the proximal-end operating section and the distal-end treatment section of the medical treatment device can be moved in the same direction. Furthermore, because the proximal-end operating section and the distal-end treatment section are integrated with each other, the proximal-end operating section and the distal-end treatment section can also be moved in the same direction with respect to the axial direction of the medical treatment device. 
     Accordingly, when the distal-end treatment section inserted into the body cavity is to be directly manipulated by using the proximal-end operating section disposed outside the body cavity, the moving directions of the proximal-end operating section and the distal-end treatment section can be synchronized with each other, so that the surgeon can perform the operation intuitively. 
     A second aspect of the present invention provides a cannula including a first tubular member having a first longitudinal axis, a second tubular member having a second longitudinal axis, a connection mechanism that connects the first tubular member and the second tubular member in series, a front bearing that supports the first tubular member in a three-dimensionally pivotable manner around an axis intersecting the first longitudinal axis, a rear bearing that supports the second tubular member in a three-dimensionally pivotable manner around an axis intersecting the second longitudinal axis, and a support member that accommodates the connection mechanism therein and that secures a relative position between the front bearing and the rear bearing with a distance therebetween. The first tubular member has a first through-hole into which a flexible and elongated medical treatment device is insertable. The second tubular member has a second through-hole into which the medical treatment device is insertable. The connection mechanism connects the first tubular member and the second tubular member in a pivotable manner around an axis orthogonal to a plane including the first longitudinal axis and the second longitudinal axis. 
     According to this aspect, the first tubular member and the second tubular member connected by the connection mechanism in a pivotable manner around the axis orthogonal to the plane including the first axis and the second axis are supported by the front bearing and the rear bearing, the relative position between which is secured by the support member, in a three-dimensionally pivotable manner around the axis intersecting the first axis or the second axis. Therefore, when the first tubular member and the second tubular member are pivoted around the axis by the connection mechanism, the ends of the first tubular member and the second tubular member move in the same direction. 
     Furthermore, the first tubular member and the second tubular member are connected by the connection mechanism with the first through-hole and the second through-hole being disposed in series, so that, by inserting the first tubular member into the body cavity and fixing the support member to the body wall of a patient, the medical treatment device can be introduced into the body cavity through the through-holes of the first tubular member and the second tubular member. Then, the first tubular member and the second tubular member are pivoted around the axis by the connection mechanism, so that the proximal-end operating section and the distal-end treatment section of the medical treatment device can be moved in the same direction. Furthermore, because the proximal-end operating section and the distal-end treatment section are integrated with each other, the proximal-end operating section and the distal-end treatment section can also be moved in the same direction with respect to the axial direction of the medical treatment device. 
     Accordingly, when the distal-end treatment section inserted into the body cavity is to be directly manipulated by using the proximal-end operating section disposed outside the body cavity, the moving directions of the proximal-end operating section and the distal-end treatment section can be synchronized with each other, so that the surgeon can perform the operation intuitively. 
     In the above aspect, at least one of the front bearing and the rear bearing may have a spherical bearing structure. 
     According to this configuration, when the first tubular member or the second tubular member supported by the front bearing or the rear bearing having a spherical bearing structure is pivoted by any angle, the first tubular member or the second tubular member can still be moved with similar low resistance regardless of the pivoting direction and the pivoting angle. Therefore, the medical treatment device can be moved finely. 
     In the above aspect, at least one of the front bearing and the rear bearing may be fixable after being changed in angle around a pivot axis intersecting the axis. 
     According to this configuration, the first tubular member and the second tubular member can be pivoted without being limited by the pivoting angle range of the front bearing or the rear bearing. 
     In the above aspect, the cannula may further include a parallel link extending parallel to a longitudinal direction of the second tubular member and having one end connected to the rear bearing in a three-dimensionally pivotable manner around an axis intersecting an axial direction, a retainer that maintains the parallel link and the second tubular member parallel to each other, and a third tubular member that is elongated and is connected to another end of the parallel link. The third tubular member has a third through-hole into which the medical treatment device is insertable and that is disposed in series relative to the second through-hole. The parallel link may connect the rear bearing and the third tubular member while maintaining axes thereof parallel to each other. 
     According to this configuration, when the connected area between the first tubular member and the second tubular member is pivoted by the connection mechanism, the third tubular member can be constantly maintained parallel to the axis of the rear bearing. Moreover, the distal-end treatment section of the medical treatment device can be inserted through the third through-hole in the third tubular member and can protrude through the first through-hole in the first tubular member via the second tubular member. 
     Accordingly, the distal-end treatment section can be pivoted three-dimensionally while the proximal-end operating section of the medical treatment device disposed at the proximal end of the third tubular member is maintained parallel to the axis of the rear bearing. Consequently, the surgeon can manipulate the medical treatment device naturally as if the surgeon is directly holding the distal-end treatment section. 
     In the above aspect, the connection mechanism may be a cylindrical tube composed of a flexible material. 
     According to this configuration, the connected area between the first tubular member and the second tubular member can be pivoted by a natural angle due to the connection mechanism, thereby allowing for smoother movement of the medical treatment device. Consequently, the distal-end treatment section can be manipulated more finely. Moreover, cost reduction can be achieved, as compared with a case where the connection mechanism has a component connection structure. Therefore, with the connection mechanism being used singularly, high cost efficiency can be expected when the connection mechanism is to be replaced each time. 
     In the above aspect, the connection mechanism may have a component connection structure obtained by connecting a plurality of components. 
     According to this configuration, the medical treatment device to be inserted into the through-holes in the first tubular member and the second tubular member can be pivoted by a large fixed angle. Furthermore, the pivoting angle of the connection mechanism can be increased by increasing the number of components. Accordingly, the medical treatment device can be maintained at a large fixed curvature even with a large pivoting angle. This enables smoother forward and rearward movement of the medical treatment device, so that the medical treatment device can be moved more finely. 
     In the above aspect, the connection mechanism may have a universal joint structure obtained by connecting connection members that are pivotable around rotation axes intersecting each other. 
     According to this configuration, the pivoting of the second tubular member can be transmitted to the first tubular member efficiently with high rigidity. Consequently, the movement of the proximal-end operating section of the medical treatment device can be transmitted to the distal-end treatment section with high rigidity, whereby the distal-end treatment section can be manipulated finely. 
     In the above aspect, the connection mechanism may have a universal joint structure obtained by connecting three or more of the connection members in series. 
     According to this configuration, the connected area between the first tubular member and the second tubular member can be pivoted by a large angle while maintaining high rigidity. Consequently, the operating range of the medical treatment device can be increased. 
     In the above aspect, the cannula may further include a driver that causes the medical treatment device inserted in the first tubular member to move forward and rearward in a longitudinal direction and/or rotate around an axis. 
     According to this configuration, the medical treatment device can be moved forward and rearward or rotated freely by the driver. 
     In the above aspect, the driver may be accommodated inside the first tubular member. 
     According to this configuration, the medical treatment device can be moved forward and rearward or rotated directly by the driver. 
     In the above aspect, the front bearing may include a rotor disposed away from the first tubular member and rotatable around a rotation axis intersecting the axis of the rear bearing, a first link having one end connected to the rotor and extending parallel to the first tubular member, and a pair of second links extending parallel to each other and each having one end connected to the first link and another end connected to the first tubular member. The rotor and the first link, the first link and the second links, and the second links and the first tubular member may be connected to each other in a pivotable manner around a pivot axis orthogonal to the rotation axis of the rotor. 
     According to this configuration, the first tubular member can be pivoted in the same plane as the first link and the second links by pivoting the first link and the second links around the pivot axis. Moreover, the first tubular member can be pivoted in a plane intersecting the first link and the second links by rotating the rotor around the rotation axis. 
     In this case, the front bearing is connected to the first tubular member by means of the second links, so that the first tubular member can be supported in a three-dimensionally pivotable manner without having to dispose a bearing structure on the axis of the first tubular member. Accordingly, the first tubular member can be inserted into the body cavity through a normal trocar attached to the body wall of the patient. Moreover, a pivot point where the first tubular member pivots three-dimensionally can be disposed at the center of the body wall of the patient in the thickness direction, so that a procedure with reduced invasiveness can be achieved. 
     A third aspect of the present invention provides a cannula system including two cannulas according to one of the above aspects and a cannula holder that supports support members in a state where the two cannulas are arranged parallel to each other. The first tubular member of each cannula has a bent shape obtained by bending at least a distal end of the first tubular member toward the other cannula. 
     According to this aspect, the distal-end treatment sections of the two medical treatment devices can be brought closest to each other in a state where the proximal-end operating sections of the medical treatment devices disposed at the proximal ends of the third tubular members of the two cannulas are positioned away from each other from the position where they are closest to each other. Consequently, when the same target site is to be treated by using the two medical treatment devices, interference between the proximal-end operating sections can be prevented, so that reduced workability for the surgeon can be prevented. 
     In the above aspect, the cannula holder may include a mechanism that adjusts a tilt angle of each support member around an axis intersecting a direction in which the front bearing and the rear bearing are separated from each other. 
     According to this configuration, the tilt angles of the support members are adjusted so that the relative tile angle between the two cannulas is changed, whereby the proximal ends of the third tubular members can be moved away from each other. With each first tubular member having a bent shape in which the first tubular member bends away from the other cannula and subsequently bends toward the other cannula, when the relative tilt angle between the two cannula is changed to move the proximal ends of the third tubular members away from each other, the distal-end treatment sections of the two medical treatment devices can be disposed closest to each other. Consequently, when the same target site is to be treated by using the two medical treatment devices, interference between the proximal-end operating sections can be prevented, so that reduced workability for the surgeon can be prevented. 
     A fourth aspect of the present invention provides a manipulator including the cannula according to one of the above aspects and a medical treatment device. The medical treatment device includes a shaft that is inserted into the first tubular member and the second tubular member and that is bendable by the connection mechanism, a distal-end treatment section that is connected to a distal end of the shaft and that treats an affected site, and a proximal-end operating section that is connected to a proximal end of the shaft and that controls the distal-end treatment section. 
     According to this aspect, in the cannula, the other end of the first tubular member and the other end of the second tubular member move in the same direction when the connected area between the first tubular member and the second tubular member is bent by the connection mechanism. When the cannula is used for introducing the medical treatment device into the body cavity through the through-holes in the first tubular member and the second tubular member and the distal-end treatment section inserted into the body cavity is to be directly manipulated by using the proximal-end operating section disposed outside the body cavity, the movement of the proximal-end operating section can be synchronized with the movement of the distal-end treatment section, so that the surgeon can perform the operation intuitively. 
     REFERENCE SIGNS LIST 
     
         
           1 ,  601  medical treatment device 
           3 ,  103 ,  203 ,  303 ,  403 ,  503 ,  603 ,  703  cannula 
           11 ,  611  shaft 
           13 ,  613  gripping section (distal-end treatment section) 
           15 ,  615  handle (proximal-end operating section) 
           21  first tubular member 
           22  second tubular member 
           23  third tubular member 
           25 ,  25 A,  25 B connection mechanism 
           29  connection member 
           30  support member 
           31  front bearing 
           33  rear bearing 
           35  parallel link 
           39  retainer 
           55  driver 
           71  rotor 
           73  first link 
           75  second link 
           90  cannula holder 
           100  manipulator 
           600 ,  700  cannula system