Patent Publication Number: US-2016242839-A1

Title: Blood vessel dissecting device, blood vessel dissecting method and blood vessel harvesting method

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of Japanese Application No. 2015-032246 filed on Feb. 20, 2015, the entire content of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure generally relates to a blood vessel dissecting device, a blood vessel dissecting method and a blood vessel harvesting method. 
     BACKGROUND DISCUSSION 
     It is widely known to use an artery graft represented by an internal thoracic artery, a gastroepiploic artery and a radial artery or a vein graft represented by a great saphenous vein as a bypass vessel in performing vascular bypass grafting at the heart (coronary artery bypass grafting: CABG). At present, it has been reported that artery grafts (particularly, internal thoracic artery grafts) offer higher long-term patency rates than vein grafts. Thus, vein grafts are commonly said to be poor in long-term patency rate. In recent years, however, it has been reported that the long-term patency rate concerning a vein graft is enhanced when the vein graft is harvested in the state of being covered with the surrounding tissue (for example, fat, connective tissue, tissue between a skin layer and a muscle layer, tissue between a skin layer and an interosseous membrane, branch vessels, etc.) and is used as a bypass vessel while remaining covered with the tissue. An example of a device by which a vein graft can be harvested in the state of being covered with the surrounding tissue is disclosed in US Application Publication No. 2006/0276815. 
     In using the device disclosed in US Application Publication No. 2006/0276815, a guide wire (support member 50) is inserted into a blood vessel to be harvested as a bypass vessel, and a tubular member (portion 40) is pushed forward while being guided by the guide wire, whereby the blood vessel can be harvested in the state of being covered with the surrounding tissue. The device disclosed in US Application Publication No. 2006/0276815, however, has drawbacks in that the guide wire may damage the internal wall of the blood vessel being harvested and that the workability in blood vessel harvesting (blood vessel dissection) is poor. 
     SUMMARY 
     The blood vessel dissecting device, blood vessel dissecting method and blood vessel harvesting method disclosed here permit dissection of a blood vessel with good workability. 
     In an aspect, there is provided a blood vessel dissecting device including: an elongated guide configured to be inserted into a living body along a blood vessel; a cutting device connectable to the guide and configured to be inserted into the living body and moved in the living body while connected to the elongated guide so that the cutting device is guided by the guide and cuts tissue surrounding the blood vessel in a direction of alignment with the blood vessel. The cutting device is deformable by an external force applied to the cutting device while the cutting device is in the living body. 
     Preferably, the blood vessel dissecting device includes two of the guides configured to be disposed to face each other, with the blood vessel interposed therebetween, in a state of being inserted in the living body, and the cutting device is connected with both of the two guides. 
     In the blood vessel dissecting device, the cutting device may be deformed in a direction in which the two guides are aligned, in accordance with a separated distance between the two guides. 
     In the blood vessel dissecting device, preferably, the cutting device is deformed so as to protrude toward an outer side of a region between the two guides. 
     In the blood vessel dissecting device, the cutting device may have a bendable/curvable section which is bent or curved by the external force. 
     In the blood vessel dissecting device, preferably, the cutting device includes: a first portion; and a second portion provided to be slidable relative to the first portion in a direction intersecting an insertion direction of the cutting device into the living body. 
     In the blood vessel dissecting device, the guide may have a function to be inserted between adjacent tissues different in properties so as to dissect the adjacent tissues from each other. 
     In the blood vessel dissecting device, preferably, the cutting device includes: a cutting section adapted to cut tissue surrounding the blood vessel; and a treating section adapted to cut and stanch a branch vessel branched from the blood vessel. 
     In another aspect, there is provided a blood vessel dissecting method including: inserting a guide into a living body; moving the guide along a blood vessel in the living body to dissect tissue in a direction of alignment of the blood vessel and the guide; inserting a cutting device into the living body and moving the cutting device along the blood vessel while guiding the cutting device with the guide; and cutting tissue surrounding the blood vessel in a direction of alignment of the blood vessel and the cutting device, with the cutting of the tissue being performed by the cutting device. The cutting device is deformed by an external force in the living body during the cutting of the tissue by the cutting device. 
     In a further aspect, there is provided a blood vessel harvesting method including: inserting a guide into a living body and moving the guide along a blood vessel in the living body to dissect tissue in a direction of alignment of the blood vessel and the guide; inserting a cutting device into the living body and moving the cutting device along the blood vessel while guiding the cutting device by the guide to cut tissue surrounding the blood vessel in a direction of alignment of the blood vessel and the cutting device; ligating the blood vessel after dissecting the tissue and after cutting the tissue surrounding the blood vessel, and then cutting the blood vessel; and harvesting the blood vessel, after ligating the blood vessel, so that the blood vessel which is harvested is covered with the tissue. During the cutting of the tissue, the cutting device is deformed by an external force in the living body. 
     According to the described aspects of the present disclosure, with the cutting device deformed according, for example, to the thickness of fat surrounding a blood vessel, it is possible to perform a blood vessel dissecting operation smoothly, without forcibly pressing the skin or fascia, by using the blood vessel dissecting device. Therefore, according to the described aspects of the present disclosure, a blood vessel dissecting operation can be carried out smoothly, irrespectively of the thickness of tissue such as fat, for example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view illustrating a blood vessel dissecting device according to a first embodiment of the present disclosure. 
         FIGS. 2A and 2B  illustrate a connected state in which a dissecting device and a cutting device possessed by the blood vessel dissecting device according to the first embodiment are connected, wherein  FIG. 2A  depicts a natural state, and  FIG. 2B  shows a deformed state. 
         FIGS. 3A and 3B  illustrate the dissecting device forming a part of the blood vessel dissecting device of  FIG. 1 , wherein  FIG. 3A  is a sectional view, and  FIG. 3B  is a sectional view taken along the section line  3 B- 3 B of  FIG. 3A . 
         FIGS. 4A and 4B  are plan views illustrating the cutting device forming a part of the blood vessel dissecting device of  FIG. 1 , wherein  FIG. 4A  shows a natural state, and  FIG. 4B  depicts a deformed state. 
         FIGS. 5A and 5B  are views for explaining a blood vessel harvesting method carried out using the blood vessel dissecting device of  FIG. 1 , wherein  FIG. 5A  is a cross-sectional view, and  FIG. 5B  is a longitudinal sectional view. 
         FIGS. 6A and 6B  are views for explaining the blood vessel harvesting method carried out using the blood vessel dissecting device of  FIG. 1 , wherein  FIG. 6A  is a cross-sectional view, and  FIG. 6B  is a longitudinal sectional view. 
         FIGS. 7A and 7B  are views for explaining the blood vessel harvesting method carried out using the blood vessel dissecting device of  FIG. 1 , wherein  FIG. 7A  is a cross-sectional view, and  FIG. 7B  is a longitudinal sectional view. 
         FIGS. 8A and 8B  are plan views illustrating a cutting device forming a part of a blood vessel dissecting device according to a second embodiment of the present disclosure, wherein  FIG. 8A  depicts a natural state, and  FIG. 8B  shows a deformed state. 
         FIGS. 9A and 9B  are cross-sectional views illustrating a cutting device forming a part of a blood vessel dissecting device according to a third embodiment of the present disclosure, wherein  FIG. 9A  shows a natural state, and  FIG. 9B  depicts a deformed state. 
         FIGS. 10A and 10B  are plan views illustrating a cutting device forming a part of a blood vessel dissecting device according to a fourth embodiment of the present disclosure, wherein  FIG. 10A  shows a natural state, and  FIG. 10B  depicts a deformed state. 
         FIGS. 11A and 11B  are sectional views illustrating a connected state in which the cutting device shown in  FIGS. 10A and 10B  and a dissecting device are connected, wherein  FIG. 11A  depicts a natural state, and  FIG. 11B  shows a deformed state. 
         FIGS. 12A and 12B  are sectional views illustrating a connected state in which a dissecting device and a cutting device forming a part of a blood vessel dissecting device according to a fifth embodiment of the present disclosure are connected, wherein  FIG. 12A  shows a natural state, and  FIG. 12B  depicts a deformed state. 
         FIG. 13  is a plan view illustrating a cutting device forming a part of a blood vessel dissecting device according to a sixth embodiment of the present disclosure. 
         FIGS. 14A and 14B  are sectional views illustrating a connected state in which the cutting device shown in  FIG. 13  and a dissecting device are connected, wherein  FIG. 14A  depicts a natural state, and  FIG. 14B  shows a deformed state. 
         FIGS. 15A and 15B  are views explaining a blood vessel harvesting method carried out using the blood vessel dissecting device possessing the cutting device shown in  FIG. 13 . 
         FIG. 16  is a plan view illustrating a cutting device forming a part of a blood vessel dissecting device according to a seventh embodiment of the present disclosure. 
         FIGS. 17A, 17B and 17C  are views explaining a blood vessel harvesting method carried out using the blood vessel dissecting device possessing the cutting device shown in  FIG. 16 . 
         FIGS. 18A and 18B  are views explaining a blood vessel harvesting method carried out using the blood vessel dissecting device possessing the cutting device shown in  FIG. 16 . 
         FIGS. 19A to 19C  illustrate a dissecting and cutting device forming a part of a blood vessel dissecting device according to an eighth embodiment of the present disclosure, wherein  FIG. 19A  is a plan view,  FIG. 19B  is a side view, and  FIG. 19C  is a sectional view taken along the section line  19 C- 19 C of  FIG. 19B . 
         FIGS. 20A and 20B  are views explaining a blood vessel harvesting method carried out using the blood vessel dissecting device possessing the dissecting and cutting device shown in  FIGS. 19A to 19C . 
     
    
    
     DETAILED DESCRIPTION 
     A blood vessel dissecting device, a blood vessel dissecting method, and a blood vessel harvesting method according to the described aspects of the present disclosure will be described in detail below, with reference to several embodiments illustrated in the attached drawings, which embodiments represent examples of the inventive blood vessel dissecting device, blood vessel dissecting method, and blood vessel harvesting method disclosed here. 
       FIG. 1  is a plan view illustrating a blood vessel dissecting device according to a first embodiment of the present disclosure.  FIGS. 2A and 2B  illustrate a connected state in which a dissecting device and a cutting device forming a part of the blood vessel dissecting device according to the first embodiment are connected, wherein  FIG. 2A  depicts a natural state, and  FIG. 2B  shows a deformed state.  FIGS. 3A and 3B  illustrate the dissecting device forming a part of the blood vessel dissecting device of  FIG. 1 , wherein  FIG. 3A  is a sectional view, and  FIG. 3B  is a sectional view taken along the section line  3 B- 3 B of  FIG. 3A .  FIGS. 4A and 4B  are plan views illustrating the cutting device forming a part of the blood vessel dissecting device of  FIG. 1 , wherein  FIG. 4A  shows a natural state, and  FIG. 4B  depicts a deformed state.  FIGS. 5A to 7B  are views for explaining a blood vessel harvesting method carried out using the blood vessel dissecting device of  FIG. 1 , wherein  FIGS. 5A, 6A and 7A  are cross-sectional views, and  FIGS. 5B, 6B and 7B  are longitudinal sectional views. In the following detailed description, for convenience of explanation, the right side in  FIG. 1  will be referred to as the “distal (side)” or distal end and the left side in  FIG. 1  will be referred to as the “proximal (side) or proximal end.” 
     A blood vessel dissecting device  100  shown in  FIG. 1  is a device used to harvest a blood vessel for use as a bypass vessel in carrying out blood vessel bypass grafting (particularly, coronary artery bypass grafting: CABG). By use of the blood vessel dissecting device  100 , a blood vessel can be harvested in the state in which the blood vessel is covered with the surrounding tissue (fat, connective tissue, etc.). The blood vessel to be harvested using the blood vessel dissecting device  100  is not particularly limited insofar as it is a blood vessel that can be used as a bypass vessel. Examples of the applicable blood vessel include an internal thoracic artery, a gastroepiploic artery, a radial artery, and a great saphenous vein. 
     It is preferable, however, that the blood vessel to be harvested is the great saphenous vein. As aforementioned, the use of the blood vessel dissecting device  100  facilitates harvesting of a blood vessel in the state in which the blood vessel is covered with the surrounding tissue. When the great saphenous vein is harvested by using the blood vessel dissecting device  100  and is used as a bypass vessel, therefore, an enhanced long-term patency rate is obtained after the bypass grafting operation. In view of this, in the following, an example of harvesting a great saphenous vein by use of the blood vessel dissecting device  100  will be described on a representative basis. 
     As illustrated in  FIG. 1 , the blood vessel dissecting device  100  includes a dissecting device  200  (guide) and a cutting device  300 . Both the dissecting device  200  and the cutting device  300  are devices which are inserted into a living body along the great saphenous vein. In addition, the blood vessel dissecting device  100  in the present embodiment includes two dissecting devices  200  and two cutting devices  300 , and the dissecting devices  200  and the cutting devices  300  can be used in a connected state in which they are connected as depicted in  FIG. 2A . The blood vessel dissecting device  100  shown in  FIG. 2A  is so configured that, when a pressure is externally exerted on the blood vessel dissecting device  100 , the blood vessel dissecting device  100  can be deformed in the vertical direction as depicted in  FIG. 2B . The dissecting device  200  and the cutting device  300  will now be described in detail below. 
     As shown in  FIG. 1 , the dissecting device  200  has an elongated bar-like shape (bar-shaped) extending substantially straight, and is provided at its distal end with a dissecting section  220  for dissecting tissue. In addition, as shown in  FIG. 3B , the dissecting device  200  has a flat or flattened shape (vertically flattened shape) in section (transverse cross-section) as seen in  FIG. 3B . The sectional shape of the dissecting device  200  is not specifically restricted; for example, the sectional shape may be a crushed-circle-like shape, such as an oblong and an ellipse, a rectangle rounded at corners, or the like. 
     The width (the length in the major axis direction of the cross-sectional shape) W 1  of the dissecting device  200  is greater than the outside diameter of the blood vessel to be harvested (in this embodiment, the great saphenous vein). To be more specific, the width W 1  is preferably about 4 mm to 4 cm greater than the outside diameter of the blood vessel to be harvested. This ensures that the possibility of contact between the cutting device  300  and the great saphenous vein can be effectively lowered at the time of inserting the cutting device  300  into the living body along the dissecting device  200 , as will be explained in the “blood vessel harvesting method” described later. 
     In addition, the dissecting device  200  is provided, at both ends of the major axis of the cross-sectional shape thereof, with rails  231  and  232  in the form of linear stretches of recesses (or trenches) which extend in the axial direction of the dissecting device  200 . The rails  231  and  232  are each a rail which is used for connection of the dissecting device  200  with the cutting device  300 , and which functions as a guide section for guiding the cutting device  300 . The rails  231  and  232  are not limited to the linear stretches of recesses (or trenches) but may be, for example, linear stretches of projection (or ridges or ribs), insofar as they each enable connection of the dissecting device  200  with the cutting device  300 . 
     As shown in  FIG. 3A , the dissecting device  200  is provided with an insertion hole  210  which opens at the proximal end and extends to a distal portion (the dissecting section  220 ). Into the insertion hole  210  is inserted an imaging device  400 . The imaging device  400  is not specifically restricted. For example, the imaging device  400  in this embodiment, as depicted in  FIG. 3A , includes an elongated main body section  410 , and an illuminating section for emitting illumination light and an imaging section  430  for imaging the forward side of the dissecting device  200  are disposed at a distal portion of the main body section  410 . The imaging section  430  includes, for example, an objective lens system disposed at the distal portion of the main body section  410  and an imaging element (e.g., solid state image sensor such as complementary metal oxide semiconductor (CMOS) image sensor or charge coupled device (CCD) sensor) disposed opposite to the objective lens system. 
     The dissecting section  220  is tapered in a narrowing manner toward the distal end of the dissecting device  200 . More specifically, the distal end portion of the dissecting section  220  possesses a tapered roughly conical shape so that the length in the minor axis direction and the length in the major axis direction of the cross-sectional shape of the dissecting section  220  both gradually decrease toward the distal end. Such a dissecting section  220  is blunt in the thickness direction, and has such a degree of sharpness (bluntness) as to be able to dissect tissues having different properties (for example, fat and skin, fat and fascia, fat and blood vessel, fat and bone, etc.) from each other without cutting branch vessels branched from the great saphenous vein. This helps ensure that a dissecting function can be sufficiently exhibited and the branch vessels are restrained from being damaged or cut by the dissecting section  220 . Accordingly, bleeding can be suppressed, and the intended procedure can be performed safely and smoothly. The shape of the dissecting section  220  is not particularly limited insofar as it enables dissection of tissues in the thickness direction (minor axis direction) of the dissecting section  220 . For example, the dissecting section  220  may be in the shape of a duck bill such that the length in the minor axis direction of the cross-sectional shape of the dissecting section  220  is gradually decreased (tapered) toward the distal end and the cross-sectional shape at the distal end is a line segment along the major axis direction. 
     The dissecting section  220  is substantially colorless and transparent and is light-transmitting. This helps ensure that when the imaging device  400  is inserted into the insertion hole  210 , the forward side of the dissecting device  200  can be observed through the dissecting section  220  by the imaging device  400 . In other words, the dissecting section  220  functions as an observation section for observation of the inside of the living body (the great saphenous vein and its surroundings), in addition to the aforementioned function as the dissecting section. The dissecting section  220  is not limited to the colorless transparent property but may be colored in red, blue, green or the like, insofar as it is light-transmitting. 
     The cutting device  300 , at the time of moving along a great saphenous vein, cuts the fat (inclusive of connective tissue) surrounding the great saphenous vein and, in addition, cuts and stanches the branch vessels branched from the great saphenous vein. As illustrated in  FIG. 1 , the cutting device  300  includes a main body section  320 , and a bar-like operation section  310  provided on the proximal side of the main body section  320  for operation to press the main body section  320 . 
     As shown in  FIG. 4A , the main body section  320  includes a base portion  330  connected to the operation section  310 , and movable portions  350   a  and  350   b  provided on both sides of the base portion  330 . 
     The base portion  330  has an elongated plate-like shape (plate-shape) extending in the major axis direction of the cutting device  300 , and has a blood vessel treating groove section  332  opening at a distal end portion of the base portion  300 . The blood vessel treating groove section  332  is a groove section which has a straight shape with a substantially constant width W 2  and which is for cutting and stanching a branch vessel  1100 . The blood vessel treating groove section  332  is provided with a treating section  340  for cutting and stanching a branch vessel. 
     As depicted in  FIG. 4A , the treating section  340  has a bipolar structure including a pair of electrodes  341  and  342  which generate an electric field inside the blood vessel treating section  332 . The electrode  341  is provided at a proximal portion of the blood vessel treating groove section  332 , whereas the electrode  342  is provided on both sides with respect to the width direction of the blood vessel treating groove section  332 . With a high-frequency alternating voltage impressed between the electrodes  341  and  342 , it is possible to heat and cut the branch vessel  1100  guided into the blood vessel treating groove section  332  and to stanch through thermal coagulation. A distal portion (a portion exposed to the blood vessel treating groove section  332 )  341   a  of the electrode  341  is preferably so sharp as to be able to cut the branch vessel  1100 . This helps ensure that if thermal coagulation (stanching) of the branch vessel  1100  can at least be achieved by the electric field generated between the electrodes  341  and  342 , the branch vessel  1100  can be physically cut by the distal portion  341   a  of the electrode  341 . Accordingly, the assuredness of the treatment by the treating section  340  is enhanced. 
     The width W 2  of the blood vessel treating groove section  332  is not particularly limited but it is preferably narrower than the outside diameter of the branch vessel  1100 . This helps ensure that the branch vessel  1100  can be pressed flat inside the blood vessel treating groove section  332  as depicted in  FIG. 4A , and, as a result, the treatment (cutting and stanching) at the treating section  340  can be performed with enhanced reliability. 
     The movable portions  350   a  and  350   b  are provided on both sides of the base portion  330  and are each connected to the base portion  330 . The movable portions  350   a  and  350   b  possess the same configuration except that they are symmetrical about, and on the upper and lower sides of, the base portion  330 , as illustrated in  FIG. 4A . Specifically, each of the movable portions  350   a  and  350   b  includes a first link  351  and bendable/curvable sections  361  and  362  for connecting the first link  351  with the base portion  330 , and constitutes a parallelogram-shaped link mechanism together with the base portion  330 . The movable portions  350   a  and  350   b  are each provided on substantially the same plane as the base portion  330 . The components of the movable portions  350   a  and  350   b  will be described below. 
     The first link  351  is provided spaced from the base portion  330 , and extends along the major axis direction of the base portion  330 . The bendable/curvable section  361  is connected to a distal end portion of the first link  351 , and the bend portion  362  is connected to a proximal portion of the first link  351 . 
     The bendable/curvable section  361  includes a second link  352  fixed to the first link  351 , and a fourth link  354  connecting the second link  352  with the base portion  330 . The bend portion  362  includes a third link  353  fixed to the first link  351 , and a fifth link  355  connecting the third link  353  with the base portion  330 . 
     The second link  352  and the third link  353  extend in substantially the same direction. That is, as illustrated, the second link  352  and the third link  353  are substantially parallel. 
     The fourth link  354  can be rotationally moved relative to each of the second link  352  and the base portion  330 . A spring member (biasing member) is provided at a connection portion between the fourth link  354  and the second link  352 , and also at a connection portion between the fourth link  354  and the base portion  330 , whereby the fourth link  354  is located on the same straight line as the second link  352  in a natural state (i.e., in a state in which no external force is applied, e.g., before use). 
     The fifth link  355  can be rotationally moved relative to each of the third link  353  and the base portion  330 . A spring member (biasing member) is provided at a connection portion between the fifth link  355  and the third link  353 , and also at a connection portion between the fifth link  355  and the base portion  330 , whereby the fifth link  355  is located on the same straight line as the third link  353  in a natural state. 
     In the natural state in which no external force is exerted, each of the movable portions  350   a  and  350   b  is in the form of a parallelogram together with the base portion  330  in plan view as shown in  FIG. 4A . When an external force is exerted, on the other hand, each of the movable portions  350   a  and  350   b  is deformed as depicted in  FIG. 4B . The movable portions  350   a ,  350   b  in the deformed configuration possessing a different configuration/shape compared to the configuration/shape of the movable portions  350   a ,  350   b  in the natural state or non-deformed state. 
     Specifically, the movable portions  350   a  and  350   b , when external forces in such directions as to bring their first links  351  closer to each other are exerted on the movable portions  350   a  and  350   b , have their fourth links  354  and fifth links  355  tilted (falling) down to the front side, as shown in  FIG. 4B , thereby being deformed so that the width W 3  of the main body section  320  becomes smaller than in the natural state shown in  FIG. 4A . Though not shown, the movable portions  350   a  and  350   b , when external forces are exerted on the movable portions  350   a  and  350   b  in such directions as to move their first links  351  away from each other are, have their fourth links  354  and fifth links  355  erected to the rear side, thereby being deformed so that the width W 3  of the main body section  320  becomes larger than in the natural state shown in  FIG. 4A . In each of these deformed states, when the external forces are removed, the movable portions  350   a  and  350   b  are returned to their natural state shown in  FIG. 4A  by the restoring forces of the aforementioned spring members. 
     Examples of the external forces include a force which the cutting device  300  receives from tissue when the cutting device  300  is inserted into a living body, and forces which the cutting device  300  receives from the two dissecting devices  200  as the cutting device  300  moves along the separated distance between the dissecting devices  200  when the cutting device  300  is inserted into a living body in the state of being connected to the two dissecting devices  200 . 
     In addition, as depicted in  FIG. 4A , the bendable/curvable section  361  of the movable portion  350   a  and the bendable/curvable section  361  of the movable portion  350   b  form a blood vessel guide groove section (first groove section)  331 . The blood vessel guide groove section  331  has a tapered shape with a width gradually decreasing toward the proximal side. The blood vessel guide groove section  331  functions as a groove section for guiding a branch vessel to the blood vessel treating groove section  332  when the cutting device  300  is pushed forward inside a living body. With the blood vessel guide groove section  331  formed in a tapered shape, the branch vessel can be guided smoothly. 
     The bendable/curvable sections  361  forming a part of the movable portions  350   a  and  350   b  are each provided with a cutting edge section (cutting section)  370  for cutting fat surrounding a great saphenous vein  1000 . As will be explained also in the “blood vessel harvesting method” described later, the cutting edge section  370  has a function to cut fat surrounding the great saphenous vein  1000  when the cutting device  300  is pushed forward in the distal direction inside a living body. Such a cutting edge section  370  preferably has such a degree of sharpness as to be able to cut fat without cutting the branch vessels  1100 . This helps ensure that the possibility of cutting of the branch vessels  1100  by the cutting edge sections  370  is lowered, so that bleeding can be restrained, and the intended procedure can be performed safely and smoothly. 
     In addition, the first links  351  have peripheral surfaces (side surfaces and distal surfaces) rounded so as to function as protection sections. As will be explained also in the “blood vessel harvesting method” described later, the first links  351  are moved along and between fat and skin while dissecting them from each other when the cutting device  300  is pushed forward in the distal direction inside a living body. Since the fat and the skin having different properties are easy to dissect from each other, the first links  351  can sufficiently exhibit a dissecting function to dissect the fat and the skin from each other, notwithstanding their distal portions are rounded. In addition, rounding the first links  351  can lower the possibility that branch vessels might be damaged or cut by the first links  351 . Further, skin can be restrained from being damaged (cauterized) by sliding against (friction with) the first links  351 . 
     As shown in  FIG. 2A , the first links  351  are provided with connection sections  381 ,  382 ,  383  and  384  connectable with the rails  231  and  232  of the dissecting devices  200 . The connection sections  381  and  382  are disposed on opposite surface sides of the first links  351 . Similarly, the connection sections  383  and  384  are disposed on opposite surface sides of the first links  351 . These connection sections  381  to  384  extend in the axial direction of the cutting devices  300 , and include stretches of projections (or ridges or ribs) corresponding to the stretches of recesses (or trenches) of the rails  231  and  232 . The cutting devices are thus connected to the dissecting devices  200  by virtue of connecting protuberances  381 - 384  fitted into connecting grooves  231 ,  232 . The provision of such connection sections  381  to  384  enables the dissecting devices  200  and the cutting devices  300  to be easily connected, as shown in  FIG. 2A . In addition, the provision of such connection sections  381  to  384  prevents unintended detachment of the dissecting devices  200  and the cutting devices  300  from each other, so that the intended procedure can be carried out smoothly and accurately. 
     A blood vessel harvesting method carried out using a blood vessel dissecting device  100  includes: a first step (blood vessel dissecting operation) of dissecting a great saphenous vein  1000  which is covered with surrounding fat  1200  by use of the blood vessel dissecting device  100 ; a second step of ligating the great saphenous vein  1000  and then cutting the great saphenous vein  1000 ; and a third step of extracting the great saphenous vein  1000  as the vein  1000  is in the state of being covered with the surrounding fat  1200  from the living body. 
     Here, the thickness of the fat  1200  surrounding the great saphenous vein  1000 , or the separated distance from the skin  1400  to the fascia  1500 , may not be constant over the entire length of the great saphenous vein  1000  but may vary. For example, there may be a part where the thickness of the fat  1200  is relatively larger as shown at the left side in  FIG. 5A  and a part where the thickness of the fat  1200  is relatively smaller as depicted at the right side in  FIG. 5A . The blood vessel dissecting device  100  in this embodiment is particularly suitable for use in the blood vessel harvesting method in the case where the thickness of the fat  1200  is not constant. In the following, therefore, description will be made of the blood vessel harvesting method in the case where the thickness of the fat  1200  is not constant as illustrated in  FIG. 5A  but is decreasing toward the right side in  FIG. 5A . 
     For convenience of explanation, in the following description of the blood vessel harvesting method, one of the two dissecting devices  200  possessed by the blood vessel dissecting device  100  will be referred to as “dissecting device  200   a ” and the other will be referred to “dissecting device  200   b .” In the following description, one of the two cutting devices  300  will be referred to as “cutting device  300   a ” and the other will be referred to as “cutting device  300   b.”   
     First, the position of the great saphenous vein  1000  to be harvested is confirmed, and a skin is incised on the basis of the position of the vein. 
     Next, the dissecting device  200   a  with the imaging device  400  inserted therein is prepared, and, while observing the inside of the living body by the imaging device  400 , the dissecting device  200   a  is inserted via an incision  1300  into the living body along the great saphenous vein  1000  while keeping the dissecting device  200   a  spaced from the great saphenous vein  1000 . Then, as shown in  FIG. 5A , the dissecting device  200   a  is disposed on the upper side (the skin  1400  side) of the great saphenous vein  1000 . In this case, the dissecting device  200   a  is so disposed that the thickness direction of the dissecting device  200   a  agrees substantially with the aligning direction in which the dissecting device  200   a  and the great saphenous vein  1000  are aligned. It is thus intended that the dissecting device  200   a  (and  200   b ) may be arranged in the vertical direction with a little position gap in the horizontal direction. The device  200   a  (and  200   b ) and the great saphenous vein  1000  can thus be positioned so that they lie in a common plane. In this operation, the dissecting device  200   a  is inserted between the fat  1200  and the skin  1400  (between tissues having different properties), and the skin  1400  and the fat  1200  are dissected or separated from each other in the thickness direction of the dissecting device  200  (in the aligning direction in which the dissecting device  200  and the great saphenous vein  1000  are aligned). Such an area is an area where dissection can be achieved particularly easily, so that this operation can be carried out with enhanced smoothness and accuracy. 
     In addition, like the dissecting device  200   a , the dissecting device  200   b  with the imaging device  400  inserted therein is inserted into the living body. In this instance, the dissecting device  200   b  is inserted between the fat  1200  and the fascia  1500  (into a boundary portion between tissues having different properties), on the lower side (the fascia  1500  side (bone side)) of the great saphenous vein  1000 . Such an area, also, is an area where dissection can be achieved particularly easily, so that this operation can be performed with enhanced smoothness and accuracy. 
     In the above-mentioned manner, the dissecting devices  200   a  and  200   b  are disposed in facing relation to each other, with the great saphenous vein  1000  interposed between the two dissecting devices  200   a  and  200   b  as illustrated in  FIG. 5B . 
     Subsequently, the cutting device  300   a  is prepared, the connection section  381  of the cutting device  300   a  is connected to the rail  231  of the dissecting device  200   a , and the connection section  383  of the cutting device  300   a  is connected to the rail  231  of the dissecting device  200   b . By this, the cutting device  300   a  is connected to both of the two dissecting devices  200   a  and  200   b . Similarly, the cutting device  300   b  is prepared, the connection section  382  of the cutting device  300   b  is connected to the rail  232  of the dissecting device  200   a , and the connection section  384  of the cutting device  300   b  is connected to the rail  232  of the dissecting device  200   b . By this, the cutting device  300   b  is connected to both of the two dissecting devices  200   a  and  200   b.    
     Next, the cutting devices  300   a  and  300   b  are inserted into the living body while guiding the cutting devices  300   a  and  300   b  by way of the two dissecting devices  200   a  and  200   b . In this case, the cutting devices  300   a  and  300   b  are moved forward while dissecting the skin  1400  from the fat  1200  by the first link  351  forming a part of the movable portion  350   a  and while dissecting the fascia  1500  from the fat  1200  by the first link  351  forming a part of the movable portion  350   b . Furthermore, the cutting devices  300   a  and  300   b  each cut the fat  1200  present on a lateral side of the great saphenous vein  1000  by the cutting edge section  370  in the left-right direction (in the aligning direction in which the cutting device  300  and the great saphenous vein  1000  are aligned), and, concurrently, cut and stanch the branch vessel  1100  by the treating section  340 . 
     In addition, in the operation of inserting the cutting devices  300   a  and  300   b , the cutting devices  300   a  and  300   b  are moved forward while being deformed in accordance with the separated distance between the dissecting devices  200   a  and  200   b , in the aligning direction in which the dissecting devices  200   a  and  200   b  are aligned. Specifically, when the separated distance between the dissecting devices  200   a  and  200   b  is substantially the same as the width W 3  of the main body section  320  of the cutting devices  300   a  and  300   b , the cutting devices  300   a  and  300   b  are not deformed and are in a natural state, as illustrated in  FIGS. 6A and 6B . On the other hand, when the separated distance between the dissecting devices  200   a  and  200   b  decreases, the cutting devices  300   a  and  300   b  are deformed so that the width W 3  of the main body section  320  is smaller than in the natural state, following the decrease in the separated distance, as shown in  FIGS. 7A and 7B . Further, though not illustrated, when the separated distance between the dissecting devices  200   a  and  200   b  increases, the cutting devices  300   a  and  300   b  are deformed so that the width W 3  of the main body section  320  is greater than in the natural state, following up to the increase in the separated distance. In this way, in this operation, the cutting devices  300   a  and  300   b  are moved while being deformed in accordance with the separated distance between the dissecting devices  200   a  and  200   b.    
     Where such deformable cutting devices  300   a  and  300   b  are used, the cutting devices  300   a  and  300   b  can be smoothly inserted irrespective of the thickness of the fat  1200 . Therefore, the blood vessel dissecting operation can be performed smoothly and with low invasiveness, without forcibly pressing the skin  1400  or the fascia  1500 . 
     Even when the cutting devices  300   a  and  300   b  are deformed, the cutting edge sections  370  provided at the bendable/curvable sections  361  are oriented forward, in the same manner as in the natural state. Therefore, the cutting devices  300   a  and  300   b  can, even in the deformed state, cut the fat surrounding the great saphenous vein  1000  in the same manner as when they are in the natural state. 
     In addition, as described above, even when the cutting devices  300   a  and  300   b  are deformed, the blood vessel guide groove sections  331  possessed by the cutting devices  300   a  and  300   b  are in the shape of gradually decreasing in width from the distal end of the main body section  320  toward the blood vessel treating groove section  332 . Therefore, the cutting devices  300   a  and  300   b  can, even in the deformed state, smoothly guide the branch vessel  1100  to the blood vessel treating groove section  332  by the blood vessel guide groove section  331 , and, as a result, can cut and stanch the branch vessel  1100 , in the same manner as when they are in the natural state. 
     Since the width W 1  of the dissecting devices  200   a  and  200   b  is greater than the outside diameter of the great saphenous vein  1000  as aforementioned, the cutting devices  300   a  and  300   b  can be pushed forward along the great saphenous vein  1000  while keeping the cutting devices  300   a  and  300   b  laterally spaced from the great saphenous vein  1000 , as shown in  FIGS. 6B and 7B . Therefore, the great saphenous vein  1000  can be prevented from being damaged during this operation. Since the first links  351  are rounded, the possibility of damaging the skin  1400  or the fascia  1500  by contact with the cutting device  300  can be lowered. 
     In addition, the dissecting devices  200   a  and  200   b  and the cutting devices  300   a  and  300   b  are separate bodies from each other, and are freely detachable from each other, as described above. Therefore, it is possible to insert the dissecting devices  200   a  and  200   b  and then insert the cutting devices  300   a  and  300   b  while guiding the cutting devices  300   a  and  300   b  with the dissecting devices  200   a  and  200   b . Therefore, the risk of cutting a part that is not to be cut, by the cutting device  300   a  or  300   b  by mistake, can be avoided. 
     By the operations as above, the fat  1200  surrounding the great saphenous vein  1000  is dissected over the entire perimeter thereof, and the great saphenous vein  1000  is dissected in the state in which the great saphenous vein  1000  is covered with the surrounding fat  1200 . The thickness of the fat  1200  dissected together with the great saphenous vein  1000  and surrounding the great saphenous vein  1000  is not particularly limited. It is preferable, however, that the thickness is about 0.1 mm to 10 mm, more preferably about 1 mm to 8 mm, and further preferably about 3 mm to 5 mm. 
     Next, the two cutting devices  300   a  and  300   b  and the two dissecting devices  200   a  and  200   b  are drawn out, and both ends of that part of the great saphenous vein  1000  which is to be harvested are ligated and then cut. 
     Subsequently, the great saphenous vein  1000  is extracted, in the state in which the great saphenous vein  1000  is covered with the surrounding fat  1200 , to the outside of the living body via the incision  1300 . 
     By the steps (first to third steps) as described above, the great saphenous vein  1000  is harvested in a state in which the great saphenous vein  1000  is covered with the surrounding fat  1200 . In such a method, while using the dissecting device  200  for treating a part which is easy to dissect so as to reduce such damages as bleeding and while using the cutting device  300  for treating the fat which is difficult to dissect, the great saphenous vein  1000  can be harvested smoothly and with low invasion. In addition, since the first step can be carried out without cutting the great saphenous vein  1000 , blood can be kept flowing through the great saphenous vein  1000  for a time as long as possible. Accordingly, the great saphenous vein  1000  is placed in an ischemic state for a shortened period of time, so that the great saphenous vein  1000  can be harvested with less damage. 
     Here, it is possible that a great saphenous vein  1000  covered with fat  1200  constitutes a bypass vessel having a superior long-term patency rate, as compared with a great saphenous vein  1000  not covered with fat  1200 . The reason is considered as follows. While the great saphenous vein  1000  is used as an artery bypass vessel, arteries are considered to be higher than veins in the blood pressure (the internal pressure exerted on the vein by blood). When a great saphenous vein in an exposed state of being not covered with tissue is used as a bypass vessel, therefore, the great saphenous vein cannot endure the blood pressure and is therefore expanded by the blood pressure, possibly resulting in lowered blood flow. In addition, thickening of blood vessel wall occurs in the process of remodeling (structural alteration) or in the process of recovery from damage to tissue. Such thickening of blood vessel wall is considered to influence the development of arterial sclerosis. From such a cause, the use of a great saphenous vein in the exposed state of being not covered with tissue as a bypass vessel is considered to lead, in the long run, to vascular occlusion. 
     On the other hand, where the great saphenous vein  1000  is covered with fat  1200 , there is a possibility that expansion of the great saphenous vein  1000  is restrained by the fat  1200 , and bending and the like of the great saphenous vein  1000  are also restrained. It is considered, therefore, that the lowering in blood flow as above-mentioned can be inhibited. In addition, it is possible that the covering with the fat  1200  reduces damages to the great saphenous vein  1000 , specifically, damages to endotheliocytes, smooth muscles, nutrient vessels (capillary plexus), etc. It is considered, therefore, that the aforementioned thickening of blood vessel walls can be restrained. For these reasons, the use of the great saphenous vein  1000  covered with the fat  1200  as a bypass vessel enables an excellent long-term patency rate. Especially, in this embodiment, nutrient vessels are left at the blood vessel walls of the great saphenous vein  1000  and in the fat  1200 . For this reason, nutrients are supplied to the great saphenous vein  1000  serving as the bypass vessel, even after the bypass grafting. This is considered to be the reason why the aforementioned effect is enhanced. 
     While this embodiment has been described, the configuration of the blood vessel dissecting device  100  is not limited to the one in this embodiment. For example, the rails  231  and  232  may be omitted from the dissecting device  200 , and the connection sections  381  to  384  may be omitted from the cutting device  300 . In this case, for example, it may be sufficient to insert the cutting device  300  into a living body along the dissecting device  200  which is inserted into the living body earlier. That is, the cutting device(s)  300  can be inserted at positions similar to that shown in  FIG. 6B , but not connected to the dissecting devices  200 . 
     The blood vessel harvesting method is not limited to the procedure adopted in this embodiment. For example, the order in which the two cutting devices  300   a  and  300   b  are inserted is not specifically restricted. The fat  1200  present on a lateral side of the great saphenous vein  1000  may be cut to the left and right by the cutting device  300   a  on one side, and, after this cutting is finished, the fat  1200  present on a lateral side of the great saphenous vein  1000  may be cut to the left and right by the cutting device  300   b  on the other side. 
     While two dissecting devices  200  and two cutting devices  300  are used in this embodiment, it is sufficient for the blood vessel dissecting device  100  to have at least one dissecting device  200  and at least one cutting device  300 . For instance, where the blood vessel dissecting device  100  has two dissecting devices  200  and one cutting device  300 , a method may be adopted in which, first, the two dissecting devices  200  are disposed on the upper and lower sides of a great saphenous vein  1000 , then the one cutting device  300  is disposed for example on one lateral side of the great saphenous vein  1000 , and fat on the one lateral side of the great saphenous vein  1000  is cut, after which the cutting device  300  is drawn out of the living body. Then, the cutting device  300  thus drawn out is disposed for example on the other lateral side of the great saphenous vein  1000 , and fat on the other lateral side of the great saphenous vein  1000  is cut. 
     While the dissecting device  200  is inserted between the fat  1200  and the skin  1400  and between the fat  1200  and the fascia  1500  in this embodiment, the insertion position of the dissecting device  200  is not particularly limited. For instance, the dissecting device  200  may be inserted between tissues having different properties, such as between the fat  1200  and a blood vessel (other than the great saphenous vein  1000 ), between the fat  1200  and a bone, between the fascia  1500  and a bone, or the like. Further, the insertion between tissues having different properties (insertion into the boundary between tissues having different properties, insertion into tissue between tissues having different properties, or the like) is not restrictive; for example, the dissecting device  200  may be inserted into the fat  1200 , thereby dissecting the fat  1200 . 
     While fat is cut by the cutting device  300  in this embodiment, the tissue to be cut by the cutting device  300  is not restricted to the fat. For instance, tissue between a skin-fat boundary and a fat-muscle boundary, tissue between a skin-fat boundary and a fat-interosseous membrane boundary, connective tissue, tissue between a skin layer and a muscle layer, tissue between a skin layer and an interosseous membrane, branch vessels, and the like may also be cut by the cutting device. 
     While the dissecting device  200  is disposed spaced from the great saphenous vein  1000  so as not to contact the great saphenous vein  1000  in this embodiment, the dissecting device  200  may be disposed in contact with the great saphenous vein  1000 . In other words, the dissecting device  200  may be inserted between the great saphenous vein  1000  and the fat  1200 . 
     While the cutting device  300  is guided into a living body by the dissecting device  200  in this embodiment, the member for guiding the cutting device  300  is not limited to the dissecting device  200 . The member for guiding the cutting device  300  may not have a function to dissect tissues having different properties, insofar as the member can guide the cutting device  300  into the living body. In this case, the dissecting device  200  may be omitted, as required. 
     While the movable portions  350   a  and  350   b  possessed by the cutting device  300  are provided at a distal portion of the cutting device  300  in this embodiment, the movable portions  350   a  and  350   b  may be provided over substantially the entire length of the cutting device  300 . 
     The blood vessel dissecting device  100  may have a fixation mechanism for maintaining a deformed state of the movable portions  350   a  and  350   b  possessed by the cutting device  300  when the movable portions  350   a  and  350   b  have been deformed. Where the blood vessel dissecting device  100  has the fixation mechanism, it is possible, for example, to preliminarily fix the width of the cutting device  300  according to the thickness of the fat  1200  by the fixation mechanism and then to perform a blood vessel dissecting operation. Where the fixation mechanism is thus provided for the deformable cutting device  300 , a cutting device  300  having a suitable width according to the thickness of the fat  1200  can be easily prepared. As a result, the need to separately prepare a new blood vessel dissecting device  100  according to the thickness of the fat  1200  can be eliminated. 
     While the movable portions  350   a  and  350   b  are the same in configuration in this embodiment, the movable portions  350   a  and  350   b  may have different configurations, or either one of them may be omitted. While the cutting device  300  has two movable portions  350   a  and  350   b  in this embodiment, the cutting device  300  may be configured by use of three or more movable portions. 
     In this embodiment, the movable portions  350   a  and  350   b  are deformable both in such a direction that the width W 3  of the main body section  320  becomes smaller than in the natural state and in such a direction that the width W 3  becomes greater than in the natural state. However, the movable portions  350   a  and  350   b  may be configured to be deformable in only either one of the just-mentioned directions. For instance, the movable portions  350   a  and  350   b  may be configured to be deformable only in such a direction that the width W 3  of the main body section  320  becomes smaller than in the natural state, or may be configured to be deformable only in such a direction that the width W 3  of the main body section  320  becomes greater than in the natural state. 
     While the length of the second link  352  and the length of the third link  353  are substantially the same as the length of the fourth link  354  and the length of the fifth link  355  respectively in this embodiment, the corresponding lengths may not necessarily be the same or comparable but may be different. Thus, the length of the second link  352  and the length of the third link  353  may be shorter, or may be longer, than the length of the fourth link  354  and the length of the fifth link  355 , respectively. In addition, for example, the second link  352  and the third link  353  may be omitted. Where the second link  352  and the third link  353  are omitted, it is sufficient that the fourth link  354  and the fifth link  355  can be rotationally moved in relation to the first link  351  and the base portion  330 . 
       FIGS. 8A and 8B  are plan views illustrating a cutting device forming part of a blood vessel dissecting device according to a second embodiment of the present disclosure, wherein  FIG. 8A  depicts a natural state, and  FIG. 8B  shows a deformed state. 
     Referring to these figures, the second embodiment will be described below. Features associated with this second embodiment that are similar to those in the first embodiment are identified by common reference numbers. The following detailed description will primarily focus on differences between this second embodiment and the first embodiment described above, and a detailed description of features already described above will not be repeated. 
     This second embodiment is the same as the first embodiment above, except for differences in the configuration of moving portions forming a part of the cutting device. 
     In a cutting device  300  in this embodiment, as illustrated in  FIGS. 8A and 8B , the second links  352  and the third links  353  forming a part of the movable portions  350   a  and  350   b  are rotationally movable in relation to first links  351 . On the other hand, the fourth links  354  and the fifth links  355  are fixed to a base portion  330 . 
     Like in the first embodiment above, the thus configured movable portions  350   a  and  350   b , when external forces are exerted on the movable portions  350   a  and  350   b  in such a direction that their first links  351  are brought closer to each other, are deformed so that the width W 3  of a main body section  320  becomes smaller than in the natural state shown in  FIG. 8A , as depicted in  FIG. 8B . In addition, though not illustrated, the movable portions  350   a  and  350   b , when external forces are exerted on the movable portions  350   a  and  350   b  in such a direction that their first links  351  are spaced away from each other, are deformed so that the width W 3  of the main body section  320  becomes greater than in the natural state shown in  FIG. 8A . 
     By the second embodiment as above, also, the same or equivalent effects to those of the aforementioned first embodiment can be produced. 
       FIGS. 9A and 9B  are cross-sectional views illustrating a cutting device forming a part of a blood vessel dissecting device according to a third embodiment of the present disclosure, wherein  FIG. 9A  shows a natural state, and  FIG. 9B  depicts a deformed state. 
     Referring to these figures, the third embodiment will be described below. Features associated with this third embodiment that are similar to those in the embodiments described above are identified by common reference numbers. The following detailed description will focus primarily on differences between this third embodiment and the embodiments described above, and a detailed description of features already described above will not be repeated. 
     This third embodiment is the same as the embodiments described above, except mainly for differences in the configuration of movable portions forming a part of a cutting device. 
     In a cutting device  300  in this embodiment, as illustrated in  FIGS. 9A and 9B , fourth links  354  and fifth links  355  are fixed to a base portion  330 . In addition, a second link (second portion)  352  forming a part of each of the movable portions  350   a  and  350   b  is slidable relative to a fourth link (first portion)  354  in an axial direction thereof, and a third link (second portion)  353  forming a part of each of the movable portions  350   a  and  350   b  is slidable relative to a fifth link (first portion)  355  in an axial direction thereof. 
     Specifically, as depicted in  FIG. 9A , each fourth link  354  is provided therein with a hole  3541  which opens to the second link  352  side and extends to the base portion  330  side, and the second link  352  is slidably disposed in the hole  3541 . In addition, a spring member  365  is provided in the hole  3541 . The spring member  365  has its one end fixed to the fourth link  354 , and has its other end fixed to the second link  352 . 
     Similarly, each fifth link  355  is provided therein with a hole  3551  which opens to the third link  353  side and extends to the base portion  330  side, and the third link  353  is slidably disposed in the hole  3551 . A spring member  366  is provided in the hole  3551 . The spring member  366  has its one end fixed to the fifth link  355 , and has its other end fixed to the third link  353 . 
     The thus configured movable portions  350   a  and  350   b , when external forces are exerted on the movable portions  350   a  and  350   b  in such a direction that their first links  351  are brought closer to each other, have their second links  352  and third links  353  slid toward a base portion  330  (in directions intersecting the direction of insertion into the living body), as depicted in  FIG. 9B . Consequently, the movable portions  305   a  and  350   b  are deformed so that the width W 3  of a main body section  320  becomes smaller than in the natural state shown in  FIG. 9A , as depicted in  FIG. 9B . Though not illustrated, the movable portions  350   a  and  350   b , when external forces are exerted on the movable portions  350   a  and  350   b  in such a direction that their first links  351  are spaced away from each other, have their second links  352  and third links  353  slid in the direction for spacing away from the base portion  330 . As a result, the movable portions  350   a  and  350   b  are deformed so that the width W 3  of the main body section  320  becomes greater than in the natural state shown in  FIG. 9A . 
     By the third embodiment as above, also, the same or equivalent effects to those of the aforementioned embodiments can be produced. 
       FIGS. 10A and 10B  are plan views illustrating a cutting device forming a part of a blood vessel dissecting device according to a fourth embodiment of the present disclosure, wherein  FIG. 10A  depicts a natural state, and  FIG. 10B  shows a deformed state.  FIGS. 11A and 11B  are sectional views illustrating a connected state in which the cutting devices shown in  FIGS. 10A and 10B  and dissecting devices are connected, wherein  FIG. 11A  shows a natural state, and  FIG. 11B  depicts a deformed state. 
     Referring to these figures, the fourth embodiment will be described below. Features associated with this fourth embodiment that are similar to those in the embodiments described above are identified by common reference numbers. The following detailed description will primarily focus on differences between this fourth embodiment and the embodiments described above, and a detailed description of features already described above will not be repeated. 
     This fourth embodiment is the same as the aforementioned embodiments, except for differences in the configuration of cutting device. 
     A main body section  320  of each cutting device  300  in this embodiment, as shown in  FIG. 10A , includes first links  351 , and a bendable/curvable section  363  including a base portion  330  and plate members (rotary movement portions)  356 . 
     Each plate member  356  has an elongated plate-like shape (plate-shaped) along the first link  351 , and is provided between the first link  351  and the base portion  330 . The plate member  356  is connected to the first link  351  and the base portion  330  so that the plate member  356  can be rotationally moved relative to the first link  351  and to the base portion  330 . In addition, a spring member (biasing member) is provided at a connection portion between the plate member  356  and the first link  351  and also at a connection portion between the plate member  356  and the base portion  330 . By this, the plate member  356  is located on the same plane as the base portion  330 , in the natural state. 
     In addition, distal portions of the plate members  356  and a distal portion of the base portion  330  form a blood vessel guide groove section  331 . A cutting edge section (cutting section)  370  is provided at each of the distal portions of the plate members  356  and the distal portion of the base portion  330 . 
     The thus configured main body section  320 , when external forces are exerted main body section  320  in such a direction that its first links  351  are brought closer to each other, have the plate members  356  tilted in the manner of bending at the connection portion between the plate member  356  and the base portion  330  so that the plate members  356  are oriented in an angled manner (not parallel) to the base portion  330 . As a result, the main body section  320  is deformed (i.e., does not lie in a common plane) so that the width W 3  of the main body section  320  (the separated distance between the first links  351 ) becomes smaller than in the natural state. 
     In this embodiment, the aforementioned spring member provided at the connection portion between the plate member  356  and the first link  351  functions as a rotary movement restriction unit for biasing the plate member  356  so as to rotationally move the plate member  356  to one side, with its position in the natural state as a reference point. Therefore, the two cutting devices  300  forming a part of the blood vessel dissecting device  100  in their state in connection with the dissecting devices  200 , when external forces are exerted on the cutting devices in such a direction that their first link  351  are brought closer to each other, are deformed so as to protrude toward the outer side of the region between the two dissecting devices  200  (toward the side opposite from a great saphenous vein  1000 ) as depicted in  FIG. 11B . 
     By the fourth embodiment as above, also, the same or equivalent effects to those of the aforementioned embodiments can be produced. 
       FIGS. 12A and 12B  are sectional views illustrating a connected state in which dissecting devices and cutting devices forming a part of a blood vessel dissecting device according to a fifth embodiment of the present disclosure are connected, wherein  FIG. 12A  depicts a natural state, and  FIG. 12B  shows a deformed state. 
     Referring to these figures, the fifth embodiment will be described below. Features associated with this fifth embodiment that are similar to those in the embodiments described above are identified by common reference numbers. The following detailed description will primarily focus on differences between this fifth embodiment and the embodiments described above, and a detailed description of features already described above will not be repeated. 
     This fifth embodiment is the same as the aforementioned embodiments, except mainly for differences in the configuration of dissecting device. 
     Plate members (rotary movement portions)  356  forming a part of a bendable/curvable section  363  of a cutting device  300  in this embodiment is flexible. In addition, plate members  356  are each fixed to a base portion  330 , and are each connected to a first link  351  in a rotationally movable manner. 
     A main body section  320  having such plate members  356 , when external forces are exerted on the main body section  320  in such a direction that the first links  351  are brought closer to each other, have the plate members  356  bent, whereby the main body section  320  is deformed so that the width W 3  of the main body section  320  (the separated distance between the first links  351 ) becomes smaller than in the natural state. Such a deformation of the main body sections  320  helps ensure that the two cutting devices  300  forming a part of the blood vessel dissecting device  100 , in the connected state, when external forces are exerted on the main body section  320  in such a direction that the first links  351  are brought closer to each other, are deformed so as to protrude toward the outer sides of the region between the two dissecting devices  200 , as depicted in  FIG. 12B . 
     By the fifth embodiment as above, also, the same or equivalent effects to those of the aforementioned embodiments can be produced. 
       FIG. 13  is a plan view illustrating a cutting device forming a part of a blood vessel dissecting device according to a sixth embodiment of the present disclosure.  FIGS. 14A and 14B  are sectional views illustrating a connected state in which the cutting devices shown in  FIG. 13  and dissecting devices are connected, wherein  FIG. 14A  depicts a natural state, and  FIG. 14B  shows a deformed state.  FIGS. 15A and 15B  are views for explaining a blood vessel harvesting method carried out using the blood vessel dissecting device forming a part of the cutting device shown in  FIG. 13 . 
     Referring to these figures, the sixth embodiment will be described below. Features associated with this sixth embodiment that are similar to those in the embodiments described above are identified by common reference numbers. The following detailed description primarily focuses on differences between this sixth embodiment and the embodiments described above, and a detailed description of features already described above of will not be repeated. 
     This sixth embodiment is the same as the aforementioned embodiments, except mainly for differences in the configuration of cutting device. 
     A main body section  320  forming a part of a cutting device  300  in this embodiment, as illustrated in  FIG. 13 , includes two first links  351 , and a flat plate-shaped base portion (rotary movement portion)  330  connected to these first links  351 . 
     The base portion  330  includes: a blood vessel guide groove section  331  which opens to a distal portion and has a tapered shape with a width gradually decreasing toward the proximal side; and a blood vessel treating groove section  332  located on the proximal side of the blood vessel guide groove section  331 . In addition, the base portion  330  is provided at its distal portion with cutting edge sections  370  along the blood vessel guide groove section  331 . 
     The base portion  330  as above is rotationally movable in relation to each of the first links  351 . A spring member (biasing member) is provided at each connection portion between the base portion  330  and each first link  351 . 
     A blood vessel dissecting device  100  that includes the cutting devices  300  configured as above, when external forces are not exerted on the cutting devices in a connected state, have two dissecting devices  200  overlapping each other in plan view as viewed in the thickness direction of the dissecting devices  200 , as shown in  FIG. 14A . On the other hand, when external forces are exerted in such a direction that the two dissecting devices  200  are brought closer to each other, the blood vessel dissecting device  100  has the two cutting devices  300  tilted in the same direction, thereby being deformed so that the two dissecting devices  200  are positionally deviated from each other in plan view. 
     In a first step, the two cutting devices  300   a  and  300   b  are inserted into a living body. During this insertion, as the separated distance between the dissecting devices  200   a  and  200   b  is decreased, the cutting devices  300   a  and  300   b  are displaced so as to be tilted relative to the dissecting devices  200   a  and  200   b , as depicted in  FIG. 15B  from the natural state shown in  FIG. 15A . Under the influence of this tilting (inclination), the dissecting devices  200   a  and  200   b  are moved sideways. In this instance, the dissecting device  200   a  is moved toward the right side in  FIG. 15A  while dissecting the skin  1400  from the fat  1200 , whereas the dissecting device  200   b  is moved toward the left side in  FIG. 15A  while dissecting the fascia  1500  from the fat  1200 . In other words, the dissecting devices  200   a  and  200   b  are moved in opposite directions. In this way, the blood vessel dissecting device  100  in this embodiment changes in posture according to the thickness of the fat  1200 . 
     By use of the blood vessel dissecting device  100  whose posture can be changed, the cutting devices  300   a  and  300   b  can be smoothly inserted, irrespective of the thickness of the fat  1200 . Therefore, the blood vessel dissecting operation can be carried out smoothly and with less invasion, without forcibly pressing the skin  1400  or the fascia  1500 . 
     By the sixth embodiment as above, also, the same or equivalent effects to those of the aforementioned embodiments can be produced. 
       FIG. 16  is a plan view illustrating cutting devices forming a part of a blood vessel dissecting device according to a seventh embodiment of the present disclosure.  FIGS. 17A to 18B  are views explaining a blood vessel harvesting method carried out using the blood vessel dissecting device that includes the cutting devices shown in  FIG. 16 . 
     Referring to these figures, the seventh embodiment will be described below. Features associated with this seventh embodiment that are similar to those in the embodiments described above are identified by common reference numbers. The following detailed description primarily focuses on differences between this seventh embodiment and the embodiments described above, and a detailed description of features already described above will not be repeated. 
     This seventh embodiment is the same as the aforementioned embodiments, except for differences in the configuration of cutting devices. 
     As shown in  FIG. 16 , a blood vessel dissecting device  100  in this embodiment has a cutting device set  30  including three cutting devices  300   x ,  300   y  and  300   z . In addition, the blood vessel dissecting device  100  in this embodiment has two such cutting device sets  30 . 
     The cutting devices  300   x ,  300   y  and  300   z  are elongated plate-like in shape, and are configured in the same manner, except for differing in width. 
     Specifically, each of the cutting devices  300   x ,  300   y  and  300   z  includes a tapered blood vessel guide groove section  331 , and a blood vessel treating groove section  332  which is located on the proximal side of the blood vessel guide groove section  331  and has a straight shape with a substantially constant width. In addition, each of the cutting devices  300   x ,  300   y  and  300   z  is provided at its distal portion with cutting edge sections  370  provided along the blood vessel guide groove section  331 . The blood vessel treating groove section  332  of each of the cutting devices  300   x ,  300   y  and  300   z  is provided with a treating section  340 . 
     In a first step, first, the dissecting device  200   a  is inserted via an incision, as illustrated in  FIG. 17A .  FIG. 5A  illustrates an example of an incision  1300 . 
     Next, as shown in  FIG. 17B , the two cutting devices  300   x  are connected to the dissecting device  200   a , and are inserted into the living body while guiding the cutting devices  300   x  with the dissecting device  200   a . Subsequently, the two cutting devices  300   x  are drawn out, then, as depicted in  FIG. 17C , the two cutting devices  300   y  are connected to the dissecting device  200   a , and are inserted into the living body while guiding the cutting devices  300   y  with the dissecting device  200   a . Next, the two cutting devices  300   y  are drawn out, then, as illustrated in  FIG. 18A , the two cutting devices  300   z  are connected to the dissecting device  200   a , and are inserted into the living body while guiding the cutting devices  300   z  with the dissecting device  200   a . Then, as shown in  FIG. 18B , the dissecting device  200   b  is connected to the two cutting devices  300   z , and is inserted into the living body while being guided by the two cutting devices  300   z.    
     Thus, the cutting devices  300   x ,  300   y  and  300   z  differing in width are sequentially inserted into the living body in the order of increasing width. By this, the blood vessel dissecting operation can be carried out more smoothly, as compared with the case where the blood vessel dissecting operation is performed at a time by use of only the cutting device  300   z  having the large width. 
     By the seventh embodiment as above, also, the same or equivalent effects to those of the aforementioned embodiments can be produced. 
       FIGS. 19A to 19C  illustrate a dissecting and cutting device forming a part of a blood vessel dissecting device according to an eighth embodiment of the present disclosure, wherein  FIG. 19A  is a plan view,  FIG. 19B  is a side view, and  FIG. 19C  is a sectional view taken along line  19 C- 19 C of  FIG. 19B .  FIGS. 20A and 20B  are views for explaining a blood vessel harvesting method carried out using the blood vessel dissecting device including the dissecting and cutting device shown in  FIGS. 19A to 19C . 
     Note that in the following, for convenience of explanation, the upper side in  FIG. 19B  will be referred to as “upper side,” the lower side in  FIG. 19B  will be referred to as “lower side,” the right side in  FIG. 19B  will be referred to as “forward side” or “distal side (or end),” and the left side in  FIG. 19B  will be referred to as “rearward side” or “proximal side (or end).” 
     Referring to these figures, the eighth embodiment will be described below. Features associated with this eight embodiment that are similar to those in the embodiments described above are identified by common reference numbers. The following detailed description will primarily focus on differences between this eighth embodiment and the embodiments described above, and a detailed description of features already described above will not be repeated. 
     This eighth embodiment is the same as the embodiments described above, except for having a dissecting and cutting device in which a dissecting device and a cutting device are united with each other. 
     A blood vessel dissecting device  100  in this embodiment includes a dissecting and cutting device  600  as illustrated in  FIGS. 19A to 19C . In addition, the blood vessel dissecting device  100  in this embodiment includes two such dissecting and cutting devices  600 . 
     The dissecting and cutting device  600  is elongated in overall shape, and is provided at its distal portion with a dissecting and cutting section  620  having an arched shape projecting while curving from both ends toward outer sides (toward the lower side in  FIG. 19B ). The distal end of the dissecting and cutting section  620  has a rounded distal surface, so as to function as a dissecting section. In addition, the dissecting and cutting section  620  is provided at both lower end portions thereof with cutting edge sections (cutting sections)  370  for cutting the fat surrounding a great saphenous vein  1000 . Further, both lower end portions of the dissecting and cutting section  620  are provided with respective treating sections  340  for cutting and stanching branch vessels. Each treating section  340  has an electrode  346 . 
     As shown in  FIG. 19A , the dissecting and cutting device  600  is provided therein with an insertion hole  210  which opens at the proximal end and extends to a distal portion (the dissecting and cutting section  620 ). Into the insertion hole  210  is inserted an imaging device  400 . 
     In a first step, as illustrated in  FIG. 20A , the two dissecting and cutting devices  600  are inserted through an incision  1300  (shown in  FIG. 5A ) into the living body along a great saphenous vein  1000  while keeping the dissecting and cutting devices  600  spaced from the great saphenous vein  1000 . Then, one of the dissecting and cutting devices  600  is disposed on the upper side (the skin  1400  side) of the great saphenous vein  1000 , whereas the other of the dissecting and cutting devices  600  is disposed on the lower side (the fascia  1500  side (the bone side)) of the great saphenous vein  1000 . In this instance, the two dissecting and cutting devices  600  are so disposed that inner peripheral surfaces of their dissecting and cutting sections  620  are oriented toward (face toward) the great saphenous vein  1000  side. In this operation, one of the dissecting and cutting devices  600  is inserted between fat  1200  and a skin  1400 , thereby dissecting the fat  1200  and the skin  1400  from each other. Similarly, the other of the dissecting and cutting devices  600  is inserted between the fat  1200  and a fascia  1500 , thereby dissecting the fat  1200  and the fascia  1500  from each other. 
     In the above-mentioned way, as shown in  FIG. 20A , the two dissecting and cutting devices  600  are disposed in facing relation to each other, with the great saphenous vein  1000  interposed between the two dissecting and cutting devices  600 . 
     Next, as shown in  FIG. 20B , the two dissecting and cutting devices  600  are moved closer to each other, and lower end portions of their dissecting and cutting sections  620  are mated with each other. In this instance, the two dissecting and cutting devices  600  cut the fat  1200  present on lateral sides of the great saphenous vein  1000  to the left and right with their cutting edge sections  370 . Further, when the lower end portions of the dissecting and cutting sections  620  of the two dissecting and cutting devices  600  come close to each other, the two dissecting and cutting devices  600  generate an electric field between the electrodes  346  possessed by the treating sections  340 , thereby cutting and stanching the branch vessels  1100 . 
     Then, the two dissecting and cutting devices  600  are moved away from each other. Thereafter, the operation of dissecting the skin  1400  from the fat  1200  and dissecting the fascia  1500  from the fat  1200  as depicted in  FIG. 20A  and the operation of cutting and stanching the branch vessels  1100  while cutting the fat  1200  as depicted in  FIG. 20B  are repeated. By these operations, the great saphenous vein  1000  can be dissected in a state in which the great saphenous vein  1000  is covered with the surrounding fat  1200 . 
     By the eighth embodiment as above, also, the same or equivalent effects to those of the aforementioned first embodiment can be produced. 
     The length of the treating section  340  may, at maximum, be comparable to the length of the blood vessel to be harvested. When the length of the treating section  340  is large, the current passing area would be enlarged, possibly lowering the efficiency of coagulation and cutting. In such a situation, the current passing part may be set to be variable, and current passing may be conducted selectively and sequentially, whereby the lowering in the efficiency due to the increase in the current passing area can be prevented. 
     While the blood vessel dissecting device, the blood vessel dissecting method and the blood vessel harvesting method according to the described aspects of the present disclosure have been described above on the basis of the embodiments illustrated in the drawings, the disclosure is not limited to the embodiments. The configuration of each component can be replaced by any configuration that has a function equivalent to the original. Any other structure may be added to the configuration according to the present disclosure. In addition, the embodiments may be combined in a desired manner. 
     While the great saphenous vein is dissected in the state of being covered with fat over the entire perimeter of the vein in the aforementioned embodiments, the great saphenous vein may not necessarily be covered with fat over the entire perimeter thereof. Thus, the great saphenous vein may be dissected in a state where the periphery thereof is partly covered with fat, or in a state of being not covered with fat. 
     While the case of harvesting a bypass vessel for use in vascular bypass grafting has been described in the aforementioned embodiments, the use of the harvested blood vessel is not limited to the bypass vessel. 
     The detailed description above describes a blood vessel dissecting device, a blood vessel dissecting method and a blood vessel harvesting method according to various embodiments representing examples of the inventive blood vessel dissecting device, blood vessel dissecting method and blood vessel harvesting method disclosed here. The invention is not limited, however, to the precise embodiments and variations described. Various changes, modifications and equivalents can be effected by one skilled in the art without departing from the spirit and scope of the invention as defined in the accompanying claims. It is expressly intended that all such changes, modifications and equivalents which fall within the scope of the claims are embraced by the claims.