Abstract:
An endoscopic vein dissector for removing a vein from a living body comprises a dissector tip adapted to penetrate between the vein and surrounding tissue. A handle is provided for manipulation by a device operator to guide the tip through an incision in the living body to the vicinity of the vein. A longitudinal rod is mounted between the dissector tip and handle such that the tip is movable with respect to the handle between a retracted position and an extended position. A driver applies motive power to move the dissector tip from the retracted position to the extended position. A control element is adapted to be activated by the device operator to assist in the desired penetration between the vein and the surrounding tissue.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention relates in general to endoscopic dissection of blood vessels within the limb of a patient, and, more specifically, to power-assisted, semi-automatic operation of a dissector tip so as to ease the separation of blood vessels, such as saphenous veins, from surrounding tissue so they may be removed for use as a coronary artery bypass graft. 
         [0004]    In connection with coronary artery bypass grafting (CABG), a blood vessel or vessel section, such as an artery or vein, is “harvested” (i.e., removed) from its natural location in a patient&#39;s body to use it elsewhere in the body. In CABG surgery, the blood vessel is used to form a bypass between an arterial blood source and the coronary artery that is to be bypassed. Among the preferred sources for the vessel to be used as the bypass graft are the saphenous veins in the legs and the radial artery in the arms. 
         [0005]    Endoscopic surgical procedures for harvesting a section of a vein (e.g., the saphenous vein) subcutaneously have been developed in order to avoid disadvantages and potential complications of harvesting through a continuous incision (e.g., along the leg) for the full length of the desired vein section in order to provide adequate exposure for visualizing the vein and for introducing surgical instruments to sever, cauterize and ligate the tissue and side branches of the vein. One such minimally-invasive technique employs a small incision for locating the desired vein and for introducing one or more endoscopic harvesting devices. Primary dissection occurs by introduction of a dissecting instrument through the incision to create a working space and separate the vein from the surrounding tissue. Then a cutting instrument is introduced into the working space to severe the blood vessel from the connective tissue surrounding the section to be harvested and any side branches of the blood vessel. The branches may be clipped and/or cauterized. 
         [0006]    In one typical procedure, the endoscopic entry site is located near the midpoint of the vessel being harvested, with dissection and cutting of branches proceeding in both directions along the vessel from the entry site. In order to remove the desired section of the blood vessel, a second small incision, or stab wound, is made at one end thereof and the blood vessel section is ligated. A third small incision is made at the other end of the blood vessel section which is then ligated, thereby allowing the desired section to be completely removed through the first incision. Alternatively, only the first two incisions may be necessary if the length of the endoscopic device is sufficient to obtain the desired length of the blood vessel while working in only one direction along the vessel from the entry point. 
         [0007]    An example of a commercially available product for performing the endoscopic vein harvesting described above is the VirtuoSaph™ Endoscopic Vein Harvesting System from Terumo Cardiovascular Systems Corporation of Ann Arbor, Mich. Endoscopic vein harvesting systems are shown in U.S. Pat. No. 6,660,016 to Lindsay and U.S. patent application publication 2005/0159764A1 in the name of Kasahara et al, both of which are incorporated herein by reference in their entirety. 
         [0008]    The dissector tool typically comprises a longitudinal stainless steel rod with a tip at one end and an operator handle at the other. The tip is tapered to a blunt end and is made of transparent plastic. An optical cable inserted through the hollow handle and hollow rod abuts the tip to allow for endoscopic viewing during dissection. The dissection proceeds along the perimeter of the vein being harvested to separate it from the surrounding tissue and to expose the side branches of the vein so that they can be severed with a cutting tool. 
         [0009]    During dissection, the operator grasps the handle and pushes the rod and tip into the limb. The force required to separate the tissue can become sufficiently large to cause significant effort and strain by the operator. The repetitive nature of the motions of the hand, elbow, and shoulder can lead to fatigue or pain for the operator. Thus, it would be desirable to make dissection less physically demanding on the operator. 
         [0010]    Any inefficiency in the dissection process lengthens the amount of time required for the vein harvesting. A quicker, more efficient procedure would lead to improved patient outcomes and better use of surgical resources. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention overcomes the foregoing disadvantages with a semi-automatic dissector unit having a tip that can be driven (e.g., pneumatically) from a retracted position to an extended position by manually actuating a control element or. pushbutton. By first aligning the dissector parallel with the vein, the extension force performs the tissue separation with reduced effort by the operator. In addition to reducing operator strain and speeding up the procedure, the use of a semi-automatic power assist improves the overall precision of the tissue dissection. 
         [0012]    In one aspect of the invention, an endoscopic vein dissector for removing a vein from a living body comprises a dissector tip adapted to penetrate between the vein and surrounding tissue. A handle is provided for manipulation by a device operator to guide the tip through an incision in the living body to the vicinity of the vein. A longitudinal rod is mounted between the dissector tip and handle such that the tip is movable with respect to the handle between a retracted position and an extended position. A driver applies motive power to move the dissector tip from the retracted position to the extended position. A control element is adapted to be activated by the device operator to assist in the desired penetration between the vein and the surrounding tissue. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is an illustration of the removal of the saphenous vein from the leg of a patient. 
           [0014]      FIG. 2  is a side view of a prior art dissector unit. 
           [0015]      FIG. 3  is a side view of a prior art cutting tool. 
           [0016]      FIG. 4  is a partial cross-sectional view of the dissection of a blood vessel using a prior art dissector. 
           [0017]      FIG. 5  is a partial cross-sectional view of dissection using the semi-automatic dissector unit of the present invention. 
           [0018]      FIG. 6  is a partial cross-sectional view of a first embodiment of the semi-automatic dissector. 
           [0019]      FIG. 7  shows the dissector tip in its extended position. 
           [0020]      FIG. 8  is a partial cross-sectional view of a second embodiment of the semi-automatic dissector. 
           [0021]      FIG. 9  is a diagram of the dissector system including a fixture for bracing the dissector during power-driven extension of the dissector tip. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]    Referring now to  FIG. 1 , a saphenous vein  10  is being removed from a patient&#39;s leg  11  through an incision  12 . During harvesting, main vessel  10  is severed from side branches extending from vessel  10  and then opposite ends of vessel  10  are cut at stab wounds  13  and  14  to free it for removal. The present invention may also be employed with blood vessels harvested using different surgical methods or from different areas of the patient&#39;s body. 
         [0023]    Referring to  FIG. 2 , a disposable dissector unit  15  is shown of a known type for endoscopic dissection of a saphenous vein or other vessel by insertion through an initial incision and then pressing a dissector tip  16  into the fat along the direction of the vessel to separate it from adjacent tissue. Dissector unit  15  has a handle  17  connected to a longitudinal rod  18  having dissector tip  16  at its distal end. A receiver  19  at the end of handle  17  receives an endoscope and optical cable (not shown) for extending through rod  18  to dissector tip  16  which is transparent in order to allow visualization of the vessel and surrounding tissue. An insufflation tube  20  is connected to a source of CO 2  gas for filling the cavity adjacent the vessel as it is being formed in a conventional manner (i.e., the CO 2  gas passes through rod  18  to a release hole in or near tip  16 ). 
         [0024]    After initial blunt dissection around the vein, a harvester rod  21  as shown in  FIG. 3  is used to grasp the vessel being dissected and to sever any branches or connective tissue connecting to the vessel. Harvester rod  21  has a handle  22  connected to an elongated sleeve member  23  and an endoscope receiver  24 . At the distal end of sleeve  23  are a V-keeper  25  for retaining the vessel being dissected and a V-cutter  26  for severing branches. V-keeper  25  is manipulated by V-keeper buttons  27  on handle  22 . V-cutter  26  is extended or retracted by manipulating a V-cutter extender button  28  on handle  22 . An endoscope wiper lever  29  is provided on handle  22  for controlling a wiper that clears the end of the endoscope when the endoscope optics become covered by material in the body cavity. An insufflator tube  30  can be connected to a source of gas such as CO 2  to deliver the gas to the distal end of sleeve  23 . A bipolar cord  31  has a connector  32  at one end for connecting to a source of high frequency voltage, and includes conductors for supplying the voltage to electrodes on V-cutter  26  for cutting and cauterizing the branches and connective tissue. 
         [0025]      FIG. 4  is cross-sectional view showing a prior art dissector unit inserted subcutaneously under the lower limb  35  via a trocar  36  from a skin incision  37  in the direction of the inguinal region, for example. Trocar  36  comprises a cylindrical guide tube portion  38  for inserting rod  18 , a sealing portion  40 , and a fixing portion  41  for fixing the trocar to the skin. Tip  16  and rod  18  of dissector  15  are inserted subcutaneously under the skin via the guide tube portion  38  of trocar  36 . An endoscope inserted through receiver  19  and handle  17  extends all the way to tip  16 . Since the inserting direction of dissector  15  is along the direction of the blood vessel  42 , the operator gradually inserts the dissector so as to dissect the peripheral tissue  43  from blood vessel  42  while viewing the endoscope image. By advancing dissector tip  16  along the inserting direction, the portion of blood vessel  11  leading to the inguinal region is gradually dissected and then a further portion of blood vessel  42  may be dissected in the opposite direction from incision  37  toward the ankle. 
         [0026]    An insufflation gas (e.g., carbon dioxide) may be fed from an air feed tube  44  connected to handle  17 . The gas is discharged from an opening  45  at a front end portion of rod  18 . As blood vessel  42  is dissected from the peripheral tissue, the CO 2  gas inflates the area between the dissected tissue and the blood vessel. Therefore, the field of view of the endoscope is opened wide and visible recognition is improved. 
         [0027]    An improved, semi-automatic dissector unit  50  is shown in  FIG. 5  for more efficiently separating surrounding tissue  43  from blood vessel  42 . Pressurized carbon dioxide from tube  44  or some other power-driven means are used to extend dissector tip  51  from its retracted position shown in dashed lines  52  to its extended position shown in solid lines. A control element or push button  53  is provided on handle  54  to control application of the motive power to dissector tip  51 . Thus, the operator maintains handle  54  stationary and in parallel alignment with blood vessel  42  and then actuates control element  53  to cause dissector tip  51  to automatically extend along blood vessel  42  to separate tissue  43  from it. After the operator releases control element  53  and dissector tip  51  retracts, the dissector unit can be repositioned through the newly dissected tissue and then activated again to dissect even more tissue. Thus, the dissector unit  50  can be more quickly and easily advanced along blood vessel  42  to perform the dissection. 
         [0028]    A first embodiment of the dissector unit is shown in  FIG. 6 . A handle  60  is rigidly mounted to a longitudinal hollow rod  61 . A dissector tip  62  is mounted to a sleeve  63  which slides on rod  61 . Tip  62  is transparent and is further mounted to a hollow central rod  64  which functions as an outer jacket for receiving an optical camera cable or an endoscope. Jacket  64  is slideably mounted within handle  60  so that tip  62  and sleeve  63  are slideable between a retracted position as shown in  FIG. 6  and in extended position as shown in  FIG. 7 . 
         [0029]    Handle  60  includes a first interior wall  66  and a second interior wall  67  having central apertures  68  and  69 , respectively, for receiving slideable central rod  64 . A spacer  70  is fixed to second wall  67  and has a central aperture  71  likewise receiving central rod  64 . A flange  72  is fixed to central rod  64  and has a working surface  73  abutting one end of a return spring  74  concentrically mounted on central rod  64 . The other end of return spring  74  abuts first wall  66  so that working surface  73  receives the spring force from spring  74  for urging central rod  64  into the retracted position. Thus, when tip  62  is moved to the extended position, central rod  64  and flange  72  move to the left in  FIG. 6  thereby compressing spring  74  between surface  73  and wall  66 . Without an extension force acting on the tip, the retraction force of return spring  74  keeps the dissector tip in the retracted position toward handle  60  with flange  72  bearing against spacer  70  (i.e., spacer  70  acts as a stop for the retracted position). 
         [0030]    Extension force to extend the tip/sleeve/central rod combination away from handle  60  is provided as follows. A pressurized gas such as the insufflation carbon dioxide gas is provided via a tube  75  to a control valve  76  which is manually operable. Control valve  76  is preferably a three-port, two-way valve having an inlet port  77  receiving the pressurized gas. An outlet port  78  is coupled to a tube  80  for supplying the pressurized gas to the interior of a chamber  81 . Exhaust port  79  is coupled to ambient (i.e., atmospheric) pressure either directly outside of the handle or through an opening in the handle (e.g., as provided by the receiver). Control valve  76  could alternatively be separate from handle  60 , such as an in-line valve remotely positioned along tube  75 . 
         [0031]    A manual push button  82  is mounted to control valve  76  for selecting either an open or closed state of valve  76 . In the open state, the inlet port is coupled to the outlet port for supplying pressurized gas to chamber  81 . In the closed state, outlet port  78  is coupled to exhaust port  79  so that any pressurized gas that is present will be removed from chamber  81 . Preferably, control valve  76  is normally closed so that an open state is obtained only during the manual activation of push button  82 . 
         [0032]    Chamber  81  is shaped as a hollow disk and has an opening  83  to the interior of longitudinal rod  61 . An aperture  84  in chamber  81  acts as a bearing and receives central rod  64  and preferably includes a seal in order to maintain pressure in chamber  81 . Tip  62  has an interior working surface  85  which is physically oriented such that an extension force applied against working surface  85  by the pressurized gas tends to extend tip  62  away from handle  60 . In other words, when pressurized gas is introduced into chamber  81  and the interior of longitudinal rod  61 , the gas pressure against working surface  85  becomes greater than the opposing forces on the exterior of tip  62  causing it to move to the extended position. The extension force also overcomes the retraction force from return spring  74  so that tip  62  and sleeve  63  moves toward the left as shown in  FIG. 7 . 
         [0033]    In order to insufflate the dissected regions with the carbon dioxide, one or more holes  86  and  87  may be provided in longitudinal rod  61  to allow the carbon dioxide gas to escape when the tip is in the extended position. It is desirable to keep the size and number of holes  86  and  87  to a minimum in order to avoid excessive pressure loss and oscillation of tip  62 . Alternatively, a pneumatically separate line can be provided through the dissector unit to provide insufflation independently. 
         [0034]    A second embodiment of the dissector unit is shown in  FIG. 8  wherein like components are designated by like reference numerals. Handle  60  is connected to a fixed outer sleeve  90  which surrounds a slideable longitudinal rod  91 . An adapter  92  couples rod  91  to a transparent dissector tip  93 . Alternatively, adapter  92  and tip  93  could be a single piece. A seal  94  may be captured between rod  91  and adapter  92  to provide a seal for the sliding engagement between rod  91  and sleeve  90 . Central rod  95  is hollow and acts as a jacket to receive an optical camera cable or an endoscope. Central rod  95  remains fixed in this embodiment. Tip  93  together with adapter  92  and rod  91  slide longitudinally between the retracted position shown by solid lines and extended position as shown in dashed lines. A support ring  65  is mounted between rod  95  and tip  93  and is fixed with respect to one of them and slidable with respect to the other, so that the end of rod  95  is supported. 
         [0035]    Longitudinal rod  91  has projections  96  extending through a sealing block  97  mounted in the interior of handle  60 . A piston  98  is fixedly mounted to longitudinal rod  91  creating a piston chamber  100  between sealing block  97  and piston  98 . A tube  101  couples pressurized gas (or other fluid) from control valve  76  through sealing block  97  to piston chamber  100 . Piston  98  has a first working surface  102  facing piston chamber  100  so that when pressurized gas is introduced into chamber  100  through valve  76 , an extension force is applied against first working surface  102  causing piston  98  and longitudinal rod  91  to move toward the left into the extended position. A return spring  103  abuts a second working surface  104  of piston  98  and is compressed between second working surface  104  and an end surface  105  within handle  60 . When control valve  76  is deactivated, pressurized gas from piston chamber  100  flows out through tube  101  to the exhaust port of control valve  76  so that a retraction force from return spring  103  applied against second working surface  104  causes piston  98  and longitudinal rod  91  to move back to the right into the retracted position. Adapter  92  includes a raised area  106  for abutting outer sleeve  90  to provide a stop limit for the retraction of tip  93 . 
         [0036]    As shown in  FIG. 8 , the pressurized gas for providing semi-automatic extension and retraction of the dissector tip may be a separate gas or other fluid provided by a compressor  110  as an alternative to using the same pressurized gas used to perform the insufflation function. Thus, a tube  111  may be provided for connecting to a standard carbon dioxide source so that the insufflation gas may be provided through sealing block  97  to the interior of longitudinal rod  91  and out a hole  112 , provided in dissector tip  93 . Although pressurized gas is shown herein as a source of motive power, the invention can use other means of driving the dissector tip such as an electric motor or solenoid. 
         [0037]      FIG. 9  shows a complete dissection system according to one embodiment of the invention. A dissector unit  120  with an extendable tip  121  under control of a push button  122  receives motive power for driving tip  121  from a supply of pressurized carbon dioxide  123 . An endoscope  124  and a light source  125  are connected to the dissecting unit  120  and a controller  126 . A patient having a vein being harvested is located on a table  127 . 
         [0038]    An operator utilizing the semi-automatic dissector unit may experience backlash from the extension forces when tip  121  is driven into the tissue of the patient. To address the backlash, a fixture  130  can be provided for bracing the operator handle against the extension force. Fixture  130  includes a mounting bracket  131  for attaching to either the handle or the receiver of dissector unit  120 . An arm  132  couples mounting bracket  131  to a spindle  133  which is joined to an arm  134 . A clip  135  is mounted to the end of arm  134  for mounting the fixture to a fixed object such as table  127 . Spindle  133  has adjustable damping and allows manipulation of the position of dissector unit  120  relative to the vein being dissected under control of the operator. Adjustable damping of rotational movement of arms  132  and  134  around spindle  133  may be controlled by push buttons  136 . For example, a first push button may lock spindle  133  into its current position and a second push button may unlock spindle  133  for free rotation. Alternatively, variable damping through hydraulic systems may be employed. Spindle  133  may include a ball and socket construction to allow multi-dimensional movement. Additional spindles connected in series along the arms can be used to add additional degrees of freedom for positioning dissector unit  120 . 
         [0039]    In operation, the damping response of the spindle(s) is switched to a low value to allow the operator to align the dissector tip and the longitudinal rod substantially parallel to a portion of the vein to be dissected. By selecting the low damping response, the location of the dissector unit is easily adjusted. The operator then selects a high damping response of the spindle  133  to substantially lock the dissector unit in position. Then the operator manually triggers extension of dissector tip  121  by pressing push button  122  on the handle. When the operator terminates the manual trigger by releasing push button  122 , the dissector tip is retracted to the retracted position by the retraction force from the return spring. The operator then selects the low damping response again in order to manually re-align the dissector tip and longitudinal rod. Keeping the dissector tip and longitudinal rod substantially parallel to the next portion of the vein to be dissected, the operator then again selects the high damping response to lock the dissected unit in position. In this manner, the operator alternates manual triggering of the dissector tip extension with repositioning of the tip by appropriate selection of the damping response of the fixture to thereby dissect the surrounding tissue from the vein.