Patent Publication Number: US-2018028213-A1

Title: Unitary Endoscopic Vessel Harvesting Devices

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 14/303,970, filed Jun. 13, 2014, which is a continuation-in-part of U.S. application Ser. No. 14/190,873, filed Feb. 26, 2014, now U.S. Pat. No. 9,498,246, which claims priority to and the benefit of U.S. Provisional Application No. 61/782,034, filed Mar. 14, 2013, and U.S. Provisional Application No. 61/833,814, filed Jun. 11, 2013, all of these applications are incorporated herein by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The presently disclosed embodiments relate to endoscopic cannulas and methods of their use. 
     BACKGROUND 
     Vessel harvesting is a surgical technique that is commonly used in conjunction with coronary artery bypass surgery. During a bypass surgery, blood is rerouted to bypass blocked arteries to restore and improve blood flow and oxygen to the heart. The blood may be rerouted using a bypass graft, where one end of the by-pass graft is attached to a blood source upstream of the blocked area and the other end is attached downstream of the blocked area, creating a “conduit” channel or new blood flow connection bypassing the blocked area. Commonly, a surgeon will remove or “harvest” healthy blood vessels from another part of the body to create the bypass graft. The success of coronary artery bypass graft surgery may be influenced by the quality of the conduit and how it is handled or treated during the vessel harvest and preparation steps prior to grafting. 
     Vessel harvesting methods involve selecting a vessel, traditionally, the great saphenous vein in the leg or the radial artery in the arm to be used as a bypass conduit sealing off and cutting smaller blood vessels that branch off the main vessel conduit and harvesting the main conduit from the body. This practice does not harm the remaining blood vessel network, which heals and maintains sufficient blood flow to the extremities, allowing the patient to return to normal function without noticeable effects. 
     Minimally invasive technique for vessel harvesting is known as endoscopic vessel harvesting, a procedure that requires only small incisions. While the endoscopic vessel harvesting procedure is an improvement over a traditional “open” procedure that required a single, long incision from groin to ankle, the endoscopic procedure is still cumbersome and difficult. In particular, current endoscopic harvesting systems require multiple tools, which increases the potential for injury to the bypass conduit as well as increases the duration of the procedure. Accordingly, improvements in systems and methods for endoscopic vessel harvesting are still needed. 
     SUMMARY 
     Unitary endoscopic vessel harvesting devices are disclosed. In some embodiments, such devices may comprise an elongated body having a proximal end and a distal end. A conical tip may be disposed at the distal end of the elongated body. In addition, the surgical instrument may include one or more surgical instruments moveable in a longitudinal direction along an axis substantially parallel to a central longitudinal axis of the cannula from a retracted position proximally of a distal end of the tip to an advanced position toward the distal end of the tip to seal and cut a blood vessel. 
     In some embodiments, a surgical device of the present disclosure may include an elongated body having a proximal end and a distal end, with a conical tip disposed at the distal end of the elongated body, the tip having one or more openings in a wall of the tip. The surgical device may further include a cutting unit having a first cutting portion and a second cutting portion, the first cutting portion and the second cutting portion being moveable in a longitudinal direction relative to the elongated body to capture a blood vessel between the first cutting portion and the second cutting portion, and being rotatable relative to one another circumferentially about the tip to cut the captured blood vessel. 
     In some embodiments, a method for harvesting a blood vessel may begin by advancing a cannula having a conical dissection tip disposed at a distal tip of an elongated body along a main vessel to separate the main vessel and its branch vessels from the surrounding tissue. One or more surgical instruments may be moved in a longitudinal direction along an axis substantially parallel to a central longitudinal axis of the cannula from a retracted position proximal of a distal end of the tip to an advanced position toward the distal end of the tip to seal and cut the branch vessel. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The presently disclosed embodiments will be further explained with reference to the attached drawings, wherein like structures are referred to by like numerals throughout the several views. The drawings shown are not necessarily to scale, with emphasis instead generally being placed upon illustrating the principles of the presently disclosed embodiments. 
         FIG. 1A  illustrates a side view of an embodiment of an endoscopic cannula of the present disclosure. 
         FIG. 1B  and  FIG. 1C  illustrate an embodiment of a dissection tip of the present disclosure having an indent at the distal tip. 
         FIGS. 2A-2C  illustrate a dissection procedure using an endoscopic cannula of the present disclosure. 
         FIG. 3A ,  FIG. 3B  and  FIG. 3C  illustrate an embodiment of a cutting unit of an endoscopic cannula of the present disclosure. 
         FIGS. 4A-4D  illustrates an embodiment of a cutting unit of an endoscopic cannula of the present disclosure. 
         FIG. 5  illustrates an embodiment of a control handle suitable for use with an endoscopic cannula of the present disclosure. 
         FIGS. 6A-6F  illustrate an embodiment of an endoscopic cannula of the present disclosure in operation being controlled by the control handle of  FIG. 5 . 
         FIGS. 7A-7B  illustrate an embodiment of a cutting unit of an endoscopic cannula of the present disclosure. 
         FIG. 8  illustrates an embodiment of a cutting unit of an endoscopic cannula of the present disclosure. 
         FIG. 9A ,  FIG. 9B  and  FIG. 9C  illustrate an embodiment of a cutting unit of an endoscopic cannula of the present disclosure. 
         FIG. 10A  and  FIG. 10B  illustrate an embodiment of a cutting unit of an endoscopic cannula of the present disclosure. 
         FIGS. 11A-11C  illustrate embodiments of a removable or retractable dissection tip. 
         FIGS. 12A-12B  illustrate an embodiment of a dissection tip with optical windows. 
         FIGS. 13A-16E  illustrate various embodiments of a cannula of the present disclosure having one or more retractable surgical instrument. 
         FIGS. 17A-17B  illustrate an embodiment of a dissection tip with an opening at the distal tip. 
         FIGS. 18A-18C  illustrate an embodiment of a control handle for use with cannulas of the present disclosure. 
     
    
    
     While the above-identified drawings set forth presently disclosed embodiments, other embodiments are also contemplated, as noted in the discussion. This disclosure presents illustrative embodiments by way of representation and not limitation. Numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of the presently disclosed embodiments. 
     DETAILED DESCRIPTION 
     The present disclosure provides a unitary device for endoscopic vessel harvesting. Present systems for endoscopic vessel harvesting contain multiple components. Typically, an endoscopic dissection device is used to isolate the main vessel from the surrounding connective tissue by dissecting the main vessel from surrounding connective tissue. An endoscopic cannula is then used to introduce yet another device, an endoscopic tributary sealing instrument, to seal and sever side branches. Once the side branches are sealed, yet another device is used to harvest a section of the main vessel to be used as a bypass graft. The unitary devices of the present disclosure combine the dissection function, the tributary sealing and severing function, and, optionally, main vessel sealing and severing function, which can result in decreased vessel manipulation and improvement in ease of the procedure. The devices of the present disclosure may also be used to extract the sealed and severed main vessel from the patient. 
     Decreased vessel manipulation may decrease the potential for injury to the graft. Repeated vessel contact with multiple passes of harvesting instrumentation increases potential vessel injury. A unitary device such as the device of the present disclosure may dissect, i.e., separate the main vessel, from surrounding tissue, cauterize and transect the tributaries and the main vessel as the device is advanced, and the vessel may be harvested with a single passage of the device, rather than multiple device insertions and retractions. Such a device with a decreased diameter may be used for dissection as well as tributary ligation; graft trauma should be decreased. The relative smaller diameter of the present device can also facilitate harvesting of more tortuous vessels; for example, the internal mammary artery. 
     Referring to  FIG. 1A , an endoscopic cannula  100  of the present disclosure includes an elongated body  102  having a proximal end  104  and a distal end  106 , terminating with a dissection tip  120 , which may, in some embodiments, be conical as shown in  FIG. 1A . A central axis  101  extends between the proximal end  104  and the distal end  106  through the center of the cannula  100 . The cannula  100  further includes an cutting unit  150  disposed about the distal end  106  for sealing and cutting a blood vessel and a control handle  160  for controlling the cutting unit  150 . 
     In some embodiments, the elongated body  102  is configured for passing extravascularly through an entry incision to a vessel harvesting site. To aid in navigating the elongated body  102  to a site of harvesting, the elongated body  102  may be sufficiently rigid axially along its length. To provide the elongated body  102  with such characteristic, in an embodiment, the elongated body  102  may be made from a biocompatible material, such as, plastic material, elastomeric material, metallic material, shape memory material, composite material or any other materials that has the desired characteristics. To the extent desired, the elongated body  102  may be provided with some flexibility to move radially or laterally from side to side depending on the application. 
     In some embodiments, the elongated body  102  of the cannula  100  may be solid. In other embodiments, the endoscopic cannula  100  may include one or more lumen with lumena that accommodate advancing instruments or materials therethrough. In some embodiments, the endoscopic cannula  100  may include an endoscopic lumen  103  through which an endoscope  116  may be advanced for visualizing procedures performed using the cannula  100 . The endoscopic cannula  100  may include an adapter  114  at the proximal end  104  for advancing the endoscope  116  into the endoscopic cannula  100 . Additional lumens of the cannula  100  are described below. 
     In some embodiments, the endoscopic cannula  100  may include a dissection tip  120  disposed at or about the distal end  106  of the endoscopic cannula  100 . The viewing tip of the endoscope may be positioned inside the dissection tip  120 . In some embodiments, the dissection tip  120  may include an inner cavity in fluid communication with the endoscopic lumen  103  to enable the endoscope  116  to be advanced into the dissection tip  120 . In some embodiments, a chip-on-a-tip type of an endoscope may be integrated inside the dissection tip  120 . The tip  120  may also be transparent to allow for endoscopic viewing through the tip  120  of the procedures performed using the cannula  100 . The dissection tip  120  in some embodiments, may be provided with any shape as long as it facilitates endoscopic viewing therethrough, and allows for necessary control during tissue dissecting, i.e. separation. In some embodiments, the dissection tip may be generally conical. 
     In some embodiments, the dissection tip  120  may include a generally flat shoulder  122 , and a tapered section  124  which terminates in blunt end  126  for atraumatic separation of a vessel segment, being harvested from surrounding tissue, while minimizing or preventing tearing or puncturing of nearby vessels or tissue as the endoscopic cannula  100  is navigated along the vessel segment. Although illustrated as being blunt, it should of course be understood that, to the extent desired, the end  126  of the dissection tip  120  may be made relatively pointed to enhance advancement of the cannula  100 . 
     In reference to  FIG. 1B  and  FIG. 1C , in some embodiments, the dissection tip  120  may be cone shaped, and may be shaped at its distal end in a manner so as to minimize the negative effects of visual distortion or blinding at the center of the endoscopic view field when viewing through an endoscope inserted into the cannula  100 , with a light source and camera system. Internal surface  121  of the dissection tip  120  may be tapered, with a relatively constant slope toward the distal end  126  of the dissection tip  120 , terminating at an internal apex  123 , which may be a sharp point, as shown in  FIG. 1C . External surface  125  of the dissection tip  120  may also be tapered with a constant slope toward the distal end  126  of the dissection tip  120 ; however, at the distal end  126 , a relatively rounded, blunt end may be formed to minimize tissue damage during dissection. As illustrated, at the distal end, the external surface  125  of the dissection tip  120  may be folded back on itself in a proximal direction to then terminate at an external apex  127 , maintaining the blunt exterior surface and forming an indent in the distal end of the dissection tip  120 . Both the internal apex  123  and the external apex  127  may be collinear with the central longitudinal axis of the cannula  100  and, thus, in some embodiments, the endoscope  116 . In other words, the centers of the internal apex  123  and the external apex  127  are located on the central longitudinal axis of the cannula  100 . By providing an apex on each of the internal surface  121  and the external surface  125  of the dissection tip  120  that are also collinear with the axis of the endoscope  116 , those surfaces perpendicular to the light path (which is parallel to the endoscope axis) may be eliminated, which then may eliminate light refraction from the perpendicular surface back into the camera and, thus, may minimize or eliminate the visual distortion or blinding when viewing through the endoscope  116  with a light source and camera system. 
     To reduce likelihood of trauma during the dissection process, in some embodiments, the dissection tip  120  may be radially pliable, flexible or deformable so that the dissection tip may deflect slightly under exertion of force applied to the dissection tip  120 . In some embodiments, the dissection tip  120  is radially compressible so that the walls of the dissection tip  120  can deform under exertion of force normal to the tip surface. To that end, the dissection tip  120  may be formed from thin wall plastic material to enable the dissection tip to flex under load. Suitable materials include, but are not limited to, polycarbonate, polyethylene terephthalate glycol-modified (PETG), polyethylene terephthalate (PET) and other materials that provide enough optical clarity while allowing the dissection tip to flex under load. At the same time, the dissection tip  120  may be provided with sufficient column strength in axial or longitudinal direction to allow dissection of the vessel from the surrounding connective tissue. 
     In reference to  FIGS. 2A-2C , blood vessels used in bypass grafting (e.g. greater saphenous vein or radial artery), lie in the subcutaneous space, beneath the surface of the skin. The vessel  200  is composed of a main trunk  210 , and branch vessels  220  that emanate from the vessel trunk  210 , as shown in  FIG. 2A . The vessel  200  and its branches  210  are encased in subcutaneous fatty connective tissue  230 , and need to be dissected free of the surrounding fatty connective tissue  230  before the main vessel  200  may be harvested. The subcutaneous fat  230  is softer than skin, muscle, fascia or other connective tissues. Although adherent to the vessel  200 , the fatty connective tissue  230  forms an interface  240  with the vessel  200  that may be cleanly dissected; that is, there is a natural dissection plane between the outer layer of the vessel  200  (the adventitia), and the surrounding subcutaneous fat  230 . 
       FIG. 2B  illustrates dissection of the main trunk  210  of the vessel  200  with the dissection tip  120  along the natural dissection plane, with the dissection tip  120  advanced along the adventitial surface of the vessel  200 . Isolation of the vessel  200  from surrounding fatty connective tissue  230  along this plane, typically, does not require high dissection forces. In some embodiments, the dissection tip may  120  be provided with sufficient column strength to dissect the vessel  200  from the surrounding tissue  230  along the natural dissection plane between them. 
     On the other hand, as is illustrated in  FIG. 2C , as the dissection tip  120  approaches a branch vessel  220 , the dissection tip  120  may catch the branch vessel  220  at a junction  250  between the branch vessel  220  and the main vessel  200 . Application of excessive force with the dissection tip  220  may avulse the branch vessel and sever it from the trunk vessel, or may otherwise cause damage to the main vessel  200 . To that end, in some embodiments, the dissection tip  120  is provided with sufficient column strength to dissect the vessel  200  from the surrounding tissue  230  along the natural dissection plane between them, while being sufficiently pliable to deform or deflect from the branch vessel  220  with the application of increased force, to decrease the potential of trauma to the graft vessel during dissection around branch vessels. It should of course be understood that the rigidity of the dissection tip  120  may be varied from fully flexible to semi-rigid to rigid, in accordance with requirements of the procedure. 
     The cannula  100  may further include one or more end-effectors for cauterizing or sealing and cutting a blood vessel, either a branch vessel or the main vessel. 
     In reference to  FIG. 3A , in some embodiments, the cutting unit  150  of the cannula  100  may include a first cutting member  302  and a second cutting member  304 , each having a cutting portion  310 ,  312  extending from their respective distal ends. 
     The first cutting member  302  and the second cutting member  304  may be moveable in a longitudinal direction relative to the elongated body  102  of the cannula  100 . In this manner, the cutting portions  310 ,  312  may be moved from an initial, retracted position during the dissection, in which the cutting portions  310 ,  312  are retracted substantially proximally of the dissection tip  120  not to interfere with the dissection, to an operational or extended position for sealing and cutting, in which the cutting portions  310 ,  312  may be advanced distally for the user to see the cutting portions and to provide enough capture length for the vessel. In some embodiments, the cutting portions  310 ,  312  may at least partially extend beyond the dissection tip  120  to capture a blood vessel the cutting portions  310 ,  312 . In addition, in some embodiments, the first cutting member  302  and the second cutting member  304  may be rotatable relative to one another. In this manner, the cutting portions  310 ,  312  may be moved from an open position when the cutting portions  310 ,  312  are apart or spaced away from one another to capture a blood vessel therebetween, as shown in  FIG. 3B , to a closed position when the cutting portions  310 ,  312  are brought towards one another around the dissection tip  120  to seal and cut the blood vessel, as shown in  FIG. 3C . In some embodiments, the first cutting member  302  and the second cutting member  304  are configured so both cutting portions  310 ,  312  can be rotated circumferentially about the dissection tip  120  toward one another in both clockwise and counterclockwise direction depending on the location of the blood vessel to be captured between the cutting portions  310 ,  312 . Such bi-directional, circumferential movement of the cutting portions  310 ,  312  may allow the user to operate on blood vessels on all sides of the cannula  100  to save time and reduce cannula manipulation during the procedure as the user does not need to be concerned about the orientation and position of the cannula  100  in relation to the blood vessel. In addition, it may reduce the potential for the cutting portions to twist the side branches, thereby exerting traction on the blood vessel and consequent damage to the graft. The bi-directional movement may also be more-intuative to the user and eliminates the need to remember which side is the active side for cautery and cutting. In other embodiments, one of the cutting portions  310 ,  312  may be stationary and the other one may rotate in both clockwise and counterclockwise toward the stationary cutting portion for easier manipulation and visualization of the cutting portions  310 ,  312 . Of course, the stationary cutting portion may also be moved to a desired orientation by moving the cannula  100 . 
     The cutting portions of the cutting members  302 ,  304  may generally be elliptical or blade-like with a rounded distal tip, but any other shape that enables the cutting and sealing of a blood vessel may also be used. To facilitate sealing of the blood vessel, one or both of the cutting portions  310 ,  312  may be energized, when needed, using various sources of energy, including, but not limited to, resistive heating, ultrasound heating, and bipolar or monopolar RF energy. In some embodiments, the electrodes can be controlled independently of one another. In some embodiments, the cutting portions  310 ,  312  may be made from a material such as metal that would enable the cutting portions  310 ,  312  themselves to be energized. Additionally or alternatively, energizing elements, such as metal wires, may be disposed on the cutting portions  310 ,  312 . When energized, the energizing elements may be brought in contact with the blood vessel by the cutting portions  310 ,  312  to seal the blood vessel. In some embodiments, one or both of the cutting members  310 ,  312  may include protrusions for use as spot cautery. In some embodiments, one or both of the cutting members  310 ,  312  may have a sharpened, thin edge for concentrated application of energy to the blood vessel. Such concentrated energy application may require less energy to be applied to the side branch, thereby minimizing extension of cauterizing energy from the side branch towards the main trunk of the blood vessel, and thus eliminating potential trauma to the blood vessel. 
     To facilitate cutting of the blood vessel subsequent to sealing of the blood vessel, in some embodiments, one of the opposing edges  318 ,  320  of the cutting portions  310 ,  312  between which cutting occurs may have a leveled face while the other one may be a sharpened, thin or pointed so that the tissue is not cut in a scissor-like motion but with a thin edge against a flat surface. To that end, in some embodiments, both edges of the cutting members  310  may be sharpened edges, while both edges of the cutting portion  312  may be flat, or vise versa. Alternatively, the cutting portions  310 ,  312  may have one sharp edge or blade edge and one flat edge with the sharp edge of one cutting portion facing the flat edge of the other cutting portion. It should be noted that in some embodiments, the blood vessel may be both sealed and cut using energy, as described above. It should of course be understood that, in some embodiments, the opposing edges the opposing edges  318 ,  320  of the cutting portions  310 ,  312  may both be sharpened so the tissue is cut in a scissor-like manner. 
     As shown in  FIG. 3B  and  FIG. 3C , in some embodiments, the cutting members  302 ,  304  may be substantially u-shaped and disposed in the same plane relative to the cannula body  102 . In some embodiments, the cutting members  302 ,  304  may include respective cutouts and fingers  314 ,  316  along the edges to enable circumferential movement of the cutting members  302 ,  304  relative to one another. 
     In reference to  FIG. 4A  and  FIG. 4B , in some embodiments, the cutting members  302 ,  304  may be substantially tubular and be disposed in different planes of the cannula body  102 . As shown in  FIG. 4A , in some embodiments, the cutting member  304  may be concentrically disposed inside within the cutting member  302 . Referring to  FIG. 4B , in some embodiments, the elongated body  102  of the cannula  100  may be constructed of a series of coaxial tubes, both metal and plastic, that may act as the structural main shaft, the electrical conductive and insulative paths, and the end-effectors, i.e. cutting portions  310 ,  312 . In some embodiments, there may be three plastic sheaths acting as electrical insulators and mechanical bearing surfaces sandwiched in between two metal conductive tubes for the entire length of the device. The innermost layer may be the inner sheath  402  (plastic) defining an internal lumen  403 . The inner sheath  402  may be followed outwardly by the inner electrode tube  404  (metal), middle sheath  406  (plastic), outer electrode tube  408  (metal) and outer sheath  410  (plastic), and finally a shrink jacket  412 . In some embodiments, instead of three plastic sheaths, the electrical insulation may be provided using non-conductive coatings or similar means. For example, in some embodiments, the electrodes  404 ,  408  may be coated with polyvinyldyne flouride (PVDF), but other non-conductive coating may also be used. 
     The inner electrode tube  404  and the outer electrode tube  408  may be used to form the first cutting member  302  and the second cutting member  304 , with the cutting portions  310 ,  312  being formed at the distal ends of the inner electrode tube  404  and the outer electrode tube  408 . To enable the cutting portions  310 ,  312  to capture, seal and cut blood vessels, the inner electrode tube  404  and the outer electrode tube  408  may be slidable in the longitudinal direction relative to the cannula  100  and rotatable relative to one another. Further, because the cutting portions  310 ,  312  are formed from the inner electrode tube  404  and the outer electrode tube  408 , the cutting portions  310 ,  312  can be easily energized through the inner electrode  404  and the outer electrode  408 . In some embodiments, the cutting portion formed from the inner electrode tube  404  (i.e. inner cutting portion  411 ) may be bent out of the plane of the inner electrode  404  to enable it to rotate along the same axis and be co-radial with the cutting portion formed in the outer electrode  408  (i.e. outer cutting portion  413 ). In some embodiments, the inner cutting portion  411  may have a flat face  416  on either side of the inner cutting portion, while the outer cutting portion  413  may have a sharpened or blade edge  418  on both sides, or vice versa. In other embodiments, as described above, each cutting portion  411 ,  413  may have one sharpened edge and one flat edge, with the flat edge of one cutting portion facing the sharpened edge of the other cutting portion. 
     In reference to  FIG. 4C , in some embodiments, the dissection tip  120  may be connected to the inner sheath  402  to enable the advancement of the endoscope  116  into the dissection tip though the internal lumen  403 . A sleeve  414 , or transition, may be used to protect tissue from damage during dissection by smoothing the geometry between the dissection tip  120  and the cannula body  102 . The distal end of the sleeve  414  may be left unattached to the dissection tip  120  to allow the cutting portions  312 ,  314  to be advanced distally through the sleeve  414 , as shown in  FIG. 4D . In some embodiments, the sleeve  414  may be made of a flexible material so during dissection the sleeve  414  would comply with the dissection tip creating a smooth transition and also a tight seal to prevent tissue or bodily fluids from entering the cannula  100 . On the other hand, a flexible sleeve would be able to deflect and expand to allow the cutting portions  312 ,  314  to be advanced out distally though the sleeve  414 . In some embodiments, the surface of the sleeve may be coated with a lubricious substance to make the extension of the cutting portions  312 ,  314  through the sleeve  414  easier and smoother by decreasing friction between the cutting portions  312 ,  314  and the sleeve  414 . The thin-walled shrink tube  412  may be placed over the outer surface of the cannula body for aesthetic purposes and to assist in securing the transition. 
       FIG. 5  illustrates an embodiment of the control handle  160  for controlling the cutting members  310 ,  312 . In some embodiments, the control handle  160  may include a translation control  502  for advancing and retracting the cutting members  310 ,  312 . The control handle further includes a rotation control  504  for rotating the cutting members with respect to one another. Finally, the control handle  160  includes an energy control  506  for supplying energy (such as bipolar RF energy) to the cutting portions  310 ,  312 . The adapter  114  may be located at the proximal end of the control handle  500  for advancing the endoscope  116  into the endoscopic cannula  100 . 
     In operation, an initial incision may be made in conventional manner to expose the target vessel (e.g., the saphenous vein). The cannula  100  may be inserted into the incision and guided to the target vessel. In some embodiments, the cannula  100  may include a smooth tubular sheath around the elongated body  102  for sealing the cannula  102  within the port through which the cannula  102  is introduced into the patient. The cannula  100  may then be advanced substantially along the target vessel to dissect the target vessel from the surrounding tissue. In some embodiments, the cannula  100  may be introduced through a sealable port used to seal the incision to allow insufflation of the space created by the dissection of the target vessel from surrounding tissues. 
     As the cannula  100  is being advanced, the cutting portions  310 ,  312  of the cutting elements  302 ,  304  may be kept in a retracted position so not to interfere with tissue dissection until a branch vessel is encountered. At that point, the cutting portions  310 ,  312  may be advanced beyond the dissection tip  120 , as described above, to capture, seal and cut the branch vessel. 
     In reference to  FIGS. 6A-6F , in some embodiments using the control handle  160 , the cutting portions  310 ,  312  may be moved from a retracted position, as shown in  FIGS. 6A-6B , in the distal direction beyond the dissection tip  120  by advancing the translational control  504  on the handle to its distal position, as shown in  FIGS. 6C-6D . The cutting portions  310 ,  312  may be advanced out together and enter into the field of view of the endoscope in the dissection tip  120 . Next, the cutting portions  310 ,  312  may be rotated with respect to one another using the rotation control  504 , as shown in  FIGS. 6E-6F , for sealing and cutting the branch vessel. The cutting portions  310 ,  312  may be rotated around the dissection tip  120  in a circular arc motion. The endoscopic cannula  100  may be positioned such that the target branch vessel may lay across one of the cutting portions  310 ,  312 , regardless of orientation of the branch vessel in relation to the main blood vessel to be harvested. The endoscopic cannula  100  may be designed such that the user can place the endoscopic cannula  100  and the cutting portions  310 ,  312  as far away from the target main vessel as possible to avoid injury to the main vessel. Once in position, the user may rotate one of the cutting portions  310 ,  312  toward the other one until the branch vessel is captured. If positioned properly, the rotation is preferably always away from the main vessel, thus increasing and further maximizing the potential negative effects of lateral thermal spread. Next, when the branch vessel is positioned in between the cutting portions  310 ,  312 , the user may depresses the energy control  508  button to transfer the energy into the tributary to seal the vessel. After sealing is complete and the energy control button  508  is released, the user may continue to advance the rotation control  504  until the cutting portions  310 ,  312  transect the branch vessel. The user may then retract the cutting portions  312 ,  314  with the translation control  502  and advance the device to the next branch vessel until all tributaries have been successfully ligated and transected. 
     After the branch vessel has been hemostatically severed, the cannula  100  may be advanced forward until the next branch vessel is encountered, at which point the branch vessel may be sealed and severed using the cutting unit  300 . Once all branch vessels along a desired length of the target vessel have been sealed and severed, the cannula  100  may be used to seal and cut the target vessel according to procedure similar to the procedure used to cut and seal the branch vessels. Alternatively, the cannula  100  may be withdrawn, and another surgical device may be used to seal and cut the main vessel. 
     In some embodiments, the cannula  100  of the present disclosure may allow vessel sealing and cutting to be performed in a small cavity. Accordingly, when using the cannula  100  of the present disclosure there may not be a need to maintain the perivascular cavity in an expanded state and thus the procedure may be performed without gas insufflation of the perivascular cavity. In operation, the transparent dissection tip  120  can deflect a vessel to one side, so that the members of the cutting unit can capture the vessel, while maintaining visualization of all components in a collapsed tissue tunnel. Vessel harvesting in a small or collapsed cavity may be useful in anatomic situations characterized by vessel tortuosity, such as the internal mammary artery and vein. Harvesting without gas insufflation may also be beneficial to the graft. The carbonic acid environment of a cavity maintained by carbon dioxide gas insufflation may be detrimental to the graft vessel. A lower pH atmosphere surrounding the vessel may alter the cellular viability of the graft, potentially leading to early graft failure. Positive pressure produced by gas insufflation may also collapse the vessel, causing hemostasis, and may increase the potential for intraluminal clot formation. Presence of intraluminal clot may cause graft thrombosis and early graft failure. 
     In reference to  FIG. 7A  and  FIG. 7B , the cutting unit  150  may include a first member  702  and a second member  704 . In some embodiments, the first member  702  and second member  704  may be translatable relative to the dissection tip  120  from a proximal position, during the dissection, to a more distal position to capture, seal and cut the blood vessel. Moreover, the first member  702  and second member  704  may also be moveable relative to one another so the first member  702  and second member  704  can be space away from one another capture a blood vessel therebetween and then may be compressed against one another to seal and cut the blood vessel. To permit such movements of the first member  702  and second member  704 , in some embodiments, the first member  702  and second member  704  may be mounted on one or more actuating rods for advancing and retracting. It should, of course, be understood that other mechanisms for translating the first member  702  and second member  704  relative to the dissection tip  120  and one another may be employed. 
     The first member  702  may include four circumferentially-disposed proximal electrode segments  706  for bipolar RF cutting. The proximal electrode segments may be connected by 0.020″ conductor. The second member  704  may include two circumferentially-disposed distal electrode segments  708  for bipolar RF cutting. The distal electrode segments may be connected by 0.020″ conductor. In addition, the second member  704  may include two segments  710  for resistive heat cautery  706  disposed distally of the distal electrode segments, and a distal ring electrode  712  for monopolar cautery. The actuating rods may be employed to energize the electrodes  706 - 712 . 
     In reference to  FIG. 8 , in some embodiments, the cutting unit  150  may include a first member  802  and a second member  804 . The first member  802  and the second member  804  are translatable relative to the dissection tip and one another, as described above. In this embodiment of the cutting unit  150 , the three electrodes  708 ,  710 , and  712  of the second member  704  (see  FIGS. 7A and 7B ) are combined into one solid ring. In bipolar mode the only one side of the ring may work with active proximal segment. In monopolar mode, the entire ring may work with outside returned electrode. In some embodiments, two large cross-section conductors may also replace four electrode segments, two for RF cutting and two for resistive heat cautery, which may increase rigidity of the distal structure. 
     Moreover, the four electrodes  706  of the first member  702  can also be combined into two hemispheric electrodes  806 , which can be individually controlled. In this manner, only two larger cross-section conductors  808  may be used instead of four small ones, as in the cutting unit illustrated in  FIGS. 7A and 7B . Rigidity of the proximal structure may also increase by combining the four electrodes into two. 
     In reference to  FIG. 9A , in some embodiments, the cutting unit  150  may include a first member  902  having a proximal electrode  916  for bipolar RF cutting. The cutting unit  150  may also include a second member  904  having a distal electrode  918  for bipolar RF cutting. The cutting unit  150  may further include an electrode  914  for monopolar spot cautery disposed over the dissection tip  120 . In some embodiments, the first member  902  and the second member  904  may be made of a conductive material, with optional coating, and the electrodes  914 ,  916 ,  918  may be energized through the cutting member  902 ,  904 . 
     In reference to  FIG. 9B  and  FIG. 9C , in some embodiments, the first member  902  and the second member  904  may be tubular, with the first member  902  slidably disposed relative to the second member  904  to enable the first member  902  and the second member  904  to be biased relative to one another in a longitudinal direction. In some embodiments, the first member  902  and the second member  904  may be move in a distal direction between an inactive position proximal of the dissection tip  120 , as shown in  FIG. 9A , and an active position in the field of view of the endoscope, as shown in  FIG. 9B  and  FIG. 9C , for capturing, cutting and sealing the blood vessel. 
     The second member  904  may include one or more hooks  906  at a distal region of the second member  904 . The hook  906  may be configured to capture the branch vessel, as shown in  FIG. 9B . In some embodiments, the second member  904  may include two hooks  910  and  912 , in a spaced relation to one another, so that the branch vessel may be contacted, at a minimum, by one of the hooks. 
     In operation, the cannula  100  may be advanced to a vessel with the first member  902  and the second member  904  of the cutting unit  150  positioned proximally to the dissection tip  120 . As the vessel is encountered, as shown in  FIG. 9B , first, the second member  904  may be extended in the distal direction to capture the branch vessel by the hook of the second member  904 . Spot cautery may also be performed in this position, as desired, by a spot cautery electrode  914 . Next, the first member  902  may be advanced to pinch the branch vessel between the electrodes  916 ,  918  of the first member  902  and the second member  904 , and the RF current may be turned on for sealing and cutting the branch vessel captured in the cutting unit  150 . 
       FIG. 10A  and  FIG. 10B  illustrate yet another embodiment of the cutting unit  150  having a first member  1002  and a second member  1004 . In comparison to the embodiment of the cutting unit shown in  FIGS. 9A-9C , the second member  1004  may include only a single hook  1010  on one side of the second member  1004 , as compared to two hooks  910 ,  912  on the second member  904 . Removing one of hooks may improve visualization of the procedure by the endoscope  116  disposed within the cannula  100 . Otherwise, the structure and operations of this embodiment of the cutting unit  150  may similar to those of the embodiment of the cutting unit  150  disclosed in  FIGS. 9A-9C . 
     It should be noted while preferred types of energy for various electrodes are indicated in the present disclosure, all electrodes can be energized using various sources of energy, including, but not limited to, resistive heating, ultrasound heating, and bipolar or monopolar RF energy. In some embodiments, the electrodes can be controlled independently of one another. It should also be noted that, when appropriate, the electrodes may be insulated with an insulating coating or insulating sheath. 
     In reference to  FIG. 11A , as noted above, the endoscopic cannula  100  of the present disclosure includes the dissection tip  120  at its distal tip that may enable dissection circumferentially about a vein or an artery. The dissection tip  120 , in some embodiments, may cover the distal end of the cannula  100  and may allow for an endoscope of appropriate dimension to be advanced into the dissection tip from the proximal end of the cannula  100 . In some embodiments, as described above, the dissection tip  120  may be left on the cannula after the dissection step and throughout the entire procedure. In other embodiments, however, the dissection tip  120  may be removable from the cannula  100  or may be removably tethered to the cannula  100  to allow the user to displace the dissection tip  120  after the dissection to provide visualization without a tip. 
     In some embodiments, the dissection tip  120  may be split or peeled to render the dissection tip  120  retractable over the cannula  100  during ligation. As shown in  FIG. 11B , the dissection tip  120  can be split into multiple sections  1100 . During the dissection, the when the dissection tip  120  is advanced over the distal tip of the cannula  100 , the sections  1100  come together into a sufficiently rigid tip in a longitudinal direction to enable dissection. However, as shown in  FIG. 11C , when the dissection tip  120  is retracted, the sections  1100  are pulled apart, thereby creating an opening in the dissection tip  120  through which an endoscope or a surgical instrument can be advanced. In some embodiments, the dissection tip may be opened by exerting force on the dissection tip by an advancing endoscope to allow the endoscope to provide direct visualization by the endoscope. 
     In reference to  FIG. 12A  and  FIG. 12B , the dissection tip  120  may include optical windows  1210 . In some embodiments, windows  1210  may be placed proximally to the distal end of the dissection tip  120 . The windows  1210  may allow for visualization through an open window without the need to view through the dissection tip  120 . In some embodiments, a removable cover  1212  may positioned over the windows  1200  during dissection, as shown in  FIG. 12B , to prevent tissue and fluids from entering the inside of the dissection tip  120  through the windows  1210 . The cover  1212 , in some embodiments, may be retracted or otherwise removed during ligation, as shown in  FIG. 12A , to provide visualization through the windows  1210 . 
     In some embodiments, various surgical instruments can be provided inside the cannula  100 . Such surgical instruments may be extended out of the cannula  100 , and retracted back inside the cannula  100  when necessary, via an activation switch on the control handle (as described below). In some embodiments, the surgical instruments may be translated linearly along a line off-set and parallel to the central longitudinal axis of the cannula  100 . In some embodiments, the surgical instruments may be extended while the dissection tip  100  remains in place at the distal tip of the cannula  100 . In other embodiments, the surgical instruments may be designed to be advanced when the dissection tip  120  is removed from the cannula  100 . In some embodiments, such devices may be connected to any standard cautery source and activated via a switch or button on the handle or foot switch. Such devices can also facilitate cautery through other sources of energy such as resistive heating elements or mechanical means. This source can also do the ligating without mechanical features. 
     In some embodiments, the surgical instruments may be made of a shape-memory material. When extended substantially into the field of view, the surgical instruments may take an intended shape due to the shape memory material properties. In some embodiments, the end effector may take a shape that facilitates vessel sealing and/or ligation. 
     In some embodiments, the end effector may be a wire, rod, tube, or sheet that can extend colinear to the central axis of the cannula. Upon exiting the cone, the shape memory material may fold into a shape to facilitate coagulation and ligation. 
     In some embodiments, the end effector may be a wire, rod, tube, or sheet that can extend parallel to the central axis of the cannula along the periphery of the cannula. Upon exiting the cannula into the field of view, the shape memory material can fold into a shape to facilitate coagulation and ligation. 
     In some embodiments, the end effector may be a wire, rod, tube, or sheet that can extend out a window in the cone. Upon exiting the cone into the field of view, the shape memory material can fold into a shape to facilitate coagulation and ligation. 
     In some embodiments, the surgical instruments can be used to deliver metallic, polymeric, ceramic, elastomeric, or bio-absorbable clips or ties to facilitate vessel sealing and/or ligation. 
     In some embodiments, the surgical instruments can be used to deliver one or more energy sources, such as RF, microwave, ultrasonic, resistive heating, and laser energy to facilitate vessel sealing and/or ligation 
     In reference to  FIG. 13A  and  FIG. 13B , in some embodiments, the cannula  100  may include a split rotating finger  1310 , which may be housed or hidden proximal to the dissection tip  120 . The finger  1310  may have a spring loaded actuation switch or lever on the control handle. In this manner, the finger  1310  may be actuated to spread out into two pieces, as shown in  FIG. 13B . The finger  1310  may then be advanced over a vessel and then closed again reversing the switch/lever mechanism. Using the control handle, the finger  1310  may be energized, as discussed above, seal and cut the vessel. 
     In reference to  FIG. 14A , the cannula  100  may include a vessel capturing member  1410  that can be moved along an axis substantially parallel to the longitudinal axis of the cannula  100  from a retracted position inside the cannula  100  to an advanced position, as shown in  FIG. 14A . The vessel capturing member  1410  may be provided with various configuration to facilitate vessel capturing, such as having a J hook or an L hook at its distal end. In some embodiments, the vessel capturing member  1410  is made of a wire with a hook at its distal end. In some embodiments, the vessel capturing member  1410  may be designed to supply the needed coagulation and cutting or transection of the captured vessel by energizing the vessel capturing member  1410  while exerting pressure on the captured vessel. 
     In some embodiments, such as shown in  FIG. 14B  and  FIG. 14C , the vessel capturing member  1410  may work in cooperation with a cutting member  1420 . In some embodiments, the vessel capturing member  1410  may capture the vessel and pull the vessel against the cutting member  1420 . The cutting member  1420 , in some embodiments, may be rotatable to mate with the vessel capturing member  1410  thereby trapping the vessel and coagulating and/or cutting the captured vessel. In some embodiments, in addition to or instead of the rotatable cutting member, the vessel capturing member  1410  may also be rotatable, either with the cutting member  1420  or independent of the cutting member  1420 . As shown in  FIG. 14B , the cutting member  1420  may be a full ring. In other embodiments, as shown in  FIG. 14C , the cutting member  1420  may be a partial ring. 
     In reference to  FIG. 15A  and  FIG. 15B , in some embodiments, the cannula  100  may include a laser element  1510 , which may be housed proximal to the dissecting cone  120 . This laser element  1510  may be extendable to meet the vessel, and may be used in combination with other surgical instruments. The laser element  1510  may be connected to a laser, for example, by an optical fiber, and may be activated using the control handle or on the console of the laser. In some embodiments, the laser element may be used to transect the vessel and then can be retracted back, allowing for further dissection or advancement of the cannula  100  within the space created. In some embodiments, a window  1520  may be provided in the dissection tip  120  to allow the light from the laser  1510  to reach the vessel. 
     In reference to  FIG. 16A-16E , in some embodiments, the cannula  100  may be used to deliver and place a securing mechanism  1610 , such as a vessel clip, as staple or a suture, around a vessel to interrupt blood flow through the vessel, prior to ligating the vessel by a surgical instrument  1620 . In some embodiments, the securing mechanism may be placed on the vessel to seal the vessel and a blade  1620  or other transection device may be used to cut the vessel. 
     For example, in reference to  FIG. 16B , the surgical instrument  1620  may be used to staple the vessel with staples  1610  to stop blood flow through the vessel prior, and the same or different surgical instrument may be used to cut the vessel in between the staples. For example, in reference to  FIGS. 16C-16E , the vessel may be secured in  2  spots by  2  arms  1612 ,  1614  of the securing mechanism  1610  to seal the vessel and a blade may be used to cut the vessel in between. 
     In some embodiments, as dissection is occurring, a securing mechanism may be placed around the vessel coagulate and cut the vessel. The securing mechanism can then be retracted into the cannula  100  as it moves to the next vessel to be sealed and cut. 
     In some embodiments, the cannula  100  may include one or more surgical instruments, which can be retracted proximally substantially behind the field of view of the camera into and/or around the cannula  100  during dissection. The surgical instruments may be extended substantially in front of the field of view of the camera during vessel sealing and ligation. 
     In some embodiments, the degrees of freedom of the surgical instruments may include 1) rotation of one or more of the surgical instruments around an axis that is parallel or perpendicular to the central axis of the dissection cannula; 2) Rotation of one or more of the surgical instruments around an axis that is parallel or perpendicular to the axis of one of the other surgical instruments; 3) Translation of one or more of the surgical instruments along an axis that is parallel or perpendicular to the central axis of the dissection cannula; and 4) Translation of one or more of the surgical instruments along an axis that is parallel or perpendicular to the axis of one of the other surgical instruments. 
     In reference to  FIG. 17A  and  FIG. 17B , in some embodiments, the dissection tip  120  may be provided with a membrane  1710  at its distal tip. During the dissection, the membrane may be closed to facilitate dissection. On the other hand, during ligation, the endoscope may be advanced through the membrane  1710 , either by advancing the endoscope  116  or by retracting the dissection tip, to allow the endoscope  116  to penetrate the membrane  1710  for direct viewing during ligation. 
     In some embodiments, the surgical instruments may be controlled by a control handle  1800 . In some embodiments, as shown in  FIG. 18A  and  FIG. 18B , the control handle may have a first primary control  1810  moveable substantially parallel to the central axis of the cannula. Moving the first primary control  1810  distally may translate one or more surgical instruments parallel to the central axis of the cannula. In embodiments with multiple surgical instruments, the surgical instruments may be translated together by the first primary control  1810 . In some embodiments, the first primary control  1810  may be rotatable when fully extended, to allow for rotation the surgical instruments about the central axis of the cannula. In some embodiments, only one of the surgical instruments may be allowed to rotate with rotational movement of the first primary control. 
     In some embodiments, the control handle  1800  may include a second primary control in addition to the first primary control for independently controlling multiple surgical instruments. Each primary control may control one or more surgical instruments, independent of the other primary control. Once fully extended, one or both of the primary controls  1810 ,  1820  may be rotatable, which may allow for rotation of the surgical instruments about the central axis of the cannula. 
     Surgical devices of the present disclosure may be used in a variety of medical applications. As described above, various embodiments of the endoscopic cannula  100  of the present disclosure can be used for vessel harvesting. In some embodiments, the cannulas of the present disclosure may be used to endoscopically ligate perforator veins. In some embodiments, an incision in the skin above the perforator in need of ligation can be made and the perforator can be exposed. Then, an endoscopic cannula  100  of the present disclosure can be used to cauterize and cut the perforator, thereby eliminating the need for a large incision to access the target perforator. In some embodiments, an endoscopic cannula  100  of the present disclosure can be used in a femoral popliteal by-pass surgery. Using an endoscopic cannula  100  of the present disclosure may allow the surgeon to dissect and isolate the targets in a minimally invasive fashion to dissect and isolate large segments of vein/artery and thereby saving an entire length of the leg incision. The incision point may be only around the actual bypass points. In general, the cannulas of the present disclosure may be used in any procedure that requires ligation, cauterization or both. 
     All patents, patent applications, and published references cited herein are hereby incorporated by reference in their entirety. It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiment(s) without departing substantially from the spirit and principles of the disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. All such modifications and variations are intended to be included herein within the scope of this disclosure, as fall within the scope of the appended claims.