Abstract:
A device and method for cutting tissue to a precise depth in which a surgical blade with a rounded cutting edge, including a guard to limit the depth of penetration of the blade, is operatively connected to a handle. The device and method are particularly adapted to an endoluminal knife for cutting only the intima and media layers of a blood vessel wall during a endarterectomy procedure where the non-incised tissue is protected by the guard as the blade passes along the vessel to the point of incision. The angle of the blade may be fixed relative to the handle, or may be controllably varied by a movable cord catheter from an axial, non-contact position for the insertion and removal of the device into the artery to a radial or longitudinal, cutting position once the blade is in the desired location. Once the blade is embedded into the tissue, the device may be rotated by the handle, or by the rotation of the lumen or multilimenal catheter through which the knife has been inserted into the artery.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a knife and surgical procedure where the depth of the incision is precisely limited. 
     It is known to provide surgical knives with an adjustable guard for limiting the depth of an incision. One such guard is described in the Beaver U.S. Pat. No. 3,945,117 dated Mar. 23, 1976, and comprises a plastic material which resiliently grips the blade. However, such guards are limited by their size and construction to incisions through the skin or other exposed surfaces and the depth of the incision may require great control over the angle at which the knife is held during the procedure, i.e., variation in the angle of the knife to the skin may significantly vary the dept of incision. 
     In one aspect, it is an object of the present invention to provide a novel knife and surgical method which obviates many of the problems associated with the use of guards on surgical knives, and which may be safely used in confined areas. Accordingly, it is an object of the present invention to provide a novel knife and method of making incisions of precise and easily controllable depth. 
     However, the present invention finds particular utility in making incisions within the confines of blood vessels, e.g., in the treatment of alterosclerosis by the removal of diseased tissue from an artery. As is well known, endarterectomy is the removal of the intimal and media layers of an artery from the inside of an artery leaving the radially outer adventitia layer intact as the conduit for the blood. A continuing problem with this long used medical procedure is that the withdrawal of the plaque from the artery may result in a “feathered” endpoint or flap at the point where the removal of tissue stops. Such flaps can limit blood flow and/or be thrombogenic. This possibility is reduced by the termination of the tissue and removal by an incision to provide a clear endpoint, i.e., a termination where all three layers remain attached to each other to thereby prevent blood flow between any two adjacent layers. 
     As shown in cross-section in FIG. 1, an artery  10  is comprised of three layers, i.e., an outer layer or adventitia  12 , a middle or media layer  14 , and an intima-tunica or intimal lining  16 . Deposits collect on the intimal wall and result in stenosis, blockage or complete obstruction of the flow of blood through the artery. The procedure for removal of a diseased intima and media layer from within the adventitia is known as an endarterectomy, and a new and healthy intima will grow from the adventitia. Devices for performing an endarterectomy are well known and an endarterectomy instrument and method are disclosed in U.S. patent application Ser. No. 09/286,653, entitled “ENDARTERECTOMY LOOP”, filed Apr. 6, 1999, by the present inventor, the disclosure of which is hereby incorporated herein by reference. 
     The intima is a thin, several cell thick membrane which is not easily torn but which is readily separated from the media. The media comprises a much thicker layer of muscle cells circular in orientation and the adventitia is the layer which provides the strength of the artery. The media is easily separated from the adventitia and it these two radially inner layers, together with any associated plaque, which it is desirable to remove from the vessel. The media is generally separated from the outer wall by a ring stripper for some axial distance upstream of the endpoint where the media and intima are to be severed. Once the diseased tissue is loosened from the adventia, the diseased tissue may be removed from the vessel. 
     As shown in FIG. 2, a feathered endpoint may be formed if all three layers do not remain attached to each other. Separation of the layers from each other at the endpoint may result in the formation of a flap  22  between the media  14  and intima  12  or a flap  24  between the adventitia  16  and the media  14  and intima  12 . Such a flap  22 ,  24  in the artery  10  may be flow limiting and/or thrombogenic in nature. FIG. 3 shows a clear endpoint  32  formed in an artery  10  by the use of the present invention. 
     It is known to address this intima flap problem by vascular stents, but such stents are expensive and reduce the flexibility of the vessel. An alternative is described in the Cox U.S. Pat. No. 5,820,629 dated Oct. 13, 1998, in which a smooth transition in the intimal lining is attempted by an electrocautery coil or a radially extending blade which is inserted down the artery beyond the area of separation of the media, expanded, and then withdrawn to effect cutting of the intima and media. This procedure requires the mechanical operation of the device within the artery and great precision in the angling of the blades and depth of insertion to effect the meeting of the point of separation of the media from the adventitia at the end of the angled cut. 
     The risk of separation of the three layers is significantly reduced by cutting the media and intima together. It is accordingly an object of the present invention to provide an endarterectomy knife and method which obviates many of the deficiencies of known devices and methods for cutting of the intima and media layers of a blood vessel wall. 
     It is another object of the present invention to provide a novel device and method in which the blade is shielded from contact with the vessel during insertion and removal thereof and exposed only for the surgical procedure. 
     It is still another object of the present invention to provide a novel hand held device and method in which the blade is shielded from contact with the vessel during insertion and removal thereof and exposed for the surgical procedure by the angulation of the shaft relative to the vessel or the rotation of the blade relative to the shaft. 
     These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a pictorial view of an artery in cross-section showing the layers thereof. 
     FIG. 2 is a pictorial view of an artery in longitudinal section with an endarterectomized portion of the artery showing an endpoint with flap formation by separation of the intima from the media and by separation of the media and intima from the adventitia. 
     FIG. 3 is a pictorial view of an artery in longitudinal section with an endarterectomized portion of the artery showing a clear endpoint where the three sections of the artery remain attached. 
     FIGS.  4 ( a ) and  4 ( b ) are a pictorial view of a first embodiment of the endoluminal knife of the present invention with the position of the blade and its protective housing fixed relative to the shaft. 
     FIG. 5 is a pictorial view of a second embodiment of the endoluminal knife of the present invention with the position of the blade and its protective housing movable relative to the shaft from the insertion and removal position of FIG.  5 ( a ) to the cutting position of FIG.  5 ( b ). 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 4 illustrates one embodiment of the present invention. Referring to FIG. 4, the device  40  may be used for cutting only the intima and media layers of a blood vessel wall during a endarterectomy procedure without forming a flap of the intimal and media layers which could potentially obstruct the flow of blood through the vessel. The device  40  may comprise a handle  42 , surgical blade  44 , and guard  46 . 
     The handle  42  may be suitable for gripping by the hand of a physician externally of the blood vessel. The handle  42  may be any suitable material and is desirably comprised of bendable material, e.g., the handle  42  may be a wire coil with coated plastic or the handle  42  may be made of material similar to biopsy forceps. The handle  42  may be fairly stiff to retain its shape while in use and may allow for axial rotation with close to a one-to-one ratio. 
     The handle  42  may include ridges or serration grooves to allow for a better grip of the handle  42  by the physician. The length of the handle  42  may vary from about 5 cm to about 20 cm. The handle  42  may be malleable so that the handle  42  may be angled or adjusted nearest the guard  46  to allow the physician to determine the angle of approach of the blade  44  to the vessel wall. 
     The surgical blade  44  may be operatively connected to the handle  42  by any suitable means or the blade  42  and handle  44  may be a unitary structure. The blade  44  may be stainless steel or may be an alloy, and may be rounded or arcuate so that the blade  44  may gradually engage the surface to be cut. The blade  44  may be generally arcuate with a radius approximating the radius of the guard  46  so that the exit of the cutting edge from the guard  46  may be generally tangential to the outer surface of the guard  46  at both ends of the cutting edge. 
     The cutting edge of the blade  44  is desirably smooth and extremely sharp. The length of the cutting edge of the blade  44  may be substantially greater than the maximum distance from the cutting edge to the guard  46 . The distance from the cutting edge of the blade  44  to the guard  46  may range between about 0.1 mm and 2.0 mm. The ratio of the length of the cutting edge of the blade  44  to the maximum distance from the cutting edge to the guard  46  may be not less than about 3, and may be about 5. 
     The guard  46  may be any suitable inert material, e.g., nonreactive plastic or hydrophilic plastic. The guard  46  may be any suitable shape, e.g., a perfect sphere, generally spherical or ellipsoidal. The size of the guard  46  may be chosen by the physician to hold the wall of the vessel open during the rotation of the device  40 , to minimize trauma to the artery, and/or to minimize the risk of the blade  44  contacting the vessel wall as the blade  44  passes within the vessel. The ratio of the diameter of the guard to the diameter of the vessel may range between 0.2 and 1. When the guard is generally spherical, for example, the ratio of the radius of the cutting edge of the blade  44  to the radius of the guard  46  may range between about 0.8 and 1.2. A device  40  having a guard diameter of 1 mm may be used with a vessel with a 4 mm diameter or a 20 mm diameter. 
     The physician may choose the configuration of the device  40  or device  60  (as shown in FIG. 5) to be used in the endarterectomy procedure based on the a variety of factors, e.g., the size of the vessel, the location of the vessel within the body, and the location of the diseased tissue within the vessel. The possible configurations of the device  40 ,  60  may vary based on (1) the size and shape of the guard  44 ,  64 ; (2) the size and shape of the blade  46 ,  66 ; (3) the length of the handle  42 ,  62 ; and (4) the angle between the handle  42 ,  62  and the blade  46 ,  66 . 
     Referring again to FIG. 4, the device  40  may be used by the physician to perform an endarterectomy procedure from a single incision point transverse to the longitudinal axis of the blood vessel. The vessel may be exposed by conventional methods and then an incision may be made from the exterior of the vessel wall to obtain an entry point for the device  40  into the vessel. The physician may choose the device  40  to perform the endarterectomy as described herein. The physician may then manually adjust the angle of the handle  42  to set the angle at which the blade  44  may engage the vessel wall, e.g., approximately 90° to the longitudinal axis of the vessel. 
     The device  40  may then be inserted into the vessel via the incision point and the handle  42  may be pushed by the physician to position the blade  44  and guard  46  along the longitudinal axis of the vessel up to the location of the endpoint. Often times the physician utilizes a conventional high intensity light to illuminate the vessel and to show the position of the blade  44  within the vessel. The device  40  may be pushed in a manner to avoid contact between the blade  44  and the vessel wall. A lumen may also be inserted within the vessel up to the point where the endpoint may be cut and the device  40  inserted therein. 
     When the blade  44  is properly positioned within the vessel, the physician may manipulate the handle  42  to allow the blade  44  to gradually embed itself into the vessel wall. The blade  44  may penetrate the vessel wall through the intima and media layers with the guard  46  preventing the blade  44  from entering the adventia layer. Once the blade  44  has penetrated the vessel wall, the physician may rotate the handle  42  through 360°, which in turn causes the blade  44  to circumferentially cut the intima and media layers to form a clean endpoint. The physician may then manipulate the handle  42  to remove the blade  44  from the vessel wall, and may then remove the device  40  from the vessel by pulling the handle  42  while keeping the blade  44  from contacting the vessel wall. 
     The diseased intima and media layers of the vessel may be then loosened from the adventia up to the endpoint by any suitable means, e.g., endarterectomy loop or ring stripper. The instrument described in the Harkrider U.S. Pat. No. 6,146, 397 dated Nov. 14, 2000, for an ENDARTERECTOMY LOOP may be suitable. The loosened diseased layers may then be removed by any suitable means, e.g., suction or clamp. After the diseased layers are removed, the vessel incision may be closed. 
     The device  40  may also be used by the physician to perform an endarterectomy from an incision point made along the length of the artery or vessel. The physician may gain access to the exposed artery by making a longitudinal incision through the blood vessel wall from the exterior of the artery. The longitudinal incision will cause the artery to lay in a flat open position exposing the interior of the artery. The physician may choose the device  40  to perform the endarterectomy as described herein. 
     The physician may then utilize the device  40  to make a first and second transverse cut through the intima and media layers of the artery nearest the ends of the longitudinal incision which will result in the formation of two clear endpoints. After the two cuts are made into the exposed artery, the physician may use the blade  44  to peel the intimal and media layers from the adventia layer. The physician may also make additional longitudinal or transverse cuts into the artery wall, as needed, to facilitate the peeling of the intima and media layers from the artery wall. The intima and media layers may be completely peeled from the adventia between the two endpoints and completely removed from the artery wall. Once the diseased inner layers are removed the artery may be closed. 
     FIG. 5 illustrates another embodiment of the present invention. Referring to FIGS.  5 ( a ) and  5 ( b ), the device  60  may be used in an endarterectomy procedure and may be operated through the lumen of a catheter  68  to cut the intima and media layers of a blood vessel without severing the adventia of the blood vessel. The device  60  may also be used within the vessel without a catheter  68  or within a multilumen catheter. The device  60  may comprise an elongated handle  62 , blade  64 , guard  66  and a means to pivot the guard  66  to rotate the blade  64  from a first position to a second position within the vessel. 
     The guard  66  may be pivotally carried by the handle  62  and the device  60  may include a means for pivoting the guard  66  from the proximate end of the handle  62  so that the blade  64  may be rotated from a first position facing along the axis of the vessel to a second position. The guard  66  may be pivotably carried by the handle  62  by any suitable means, e.g., pin, bolt, or ball joint. The length of handle  62  may vary from 5 cm to 100 cm or longer as needed depending on the procedure to be performed. The guard  66  may be pivoted by any suitable means, e.g., a wire  70  connected to the guard  66  or two wires connected to the guard  66 . The wire  70  may be sufficiently rigid to allow the physician to manipulate the wire to push or pull the guard  66  and blade  64  into position. The device  60  may also include a latch  72  for selectively maintaining the position of the guard  66  and blade  64 . The latch  72  may be any suitable means, e.g., locking screw, ratchet and handle, or locking nut. 
     The guard  66  may be pivoted from the proximate end of the handle  62  by a wire  70  in order to rotate the blade  64  from a first position facing forwardly along the axis of the vessel to a second position. The second position may be either facing transversely to the axis of the vessel or facing longitudinal to the axis of the vessel. In yet another embodiment of the invention, the device  60  may include  2  wires which may be attached to the guard  66 , so that the guard  66  and blade  64  may be pivoted from the proximate end of the handle  62  from a first wire so that the blade  64  may be rotated from a first position facing forwardly along the axis of the vessel to a second position facing transversely to the axis of the vessel or rotated by a second wire so that the blade  64  may be rotated to a third position facing longitudinal to the axis of the vessel. 
     Referring again to FIGS.  5 ( a ) and ( b ), the device  60  may be used within the lumen of a catheter  68  to perform an endarterectomy procedure. The physician may first insert a catheter  68  into the artery. The physician will normally view the diseased tissue within the artery by first inserting optics within the lumen of the catheter  68  and viewing the diseased tissue to determine where to locate the endpoints. 
     The device  60  may then be inserted into the lumen of the catheter  68  with the blade  64  facing forward along the longitudinal axis of the vessel. The position of the blade  64  facing forward allows the blade  64  to pass through the catheter  68  without damaging the catheter  68  wall. Once the blade  64  exits the catheter  68 , the physician may rotate the blade  64  by pushing or pulling the wire  70  to change the orientation of the blade  64  from facing forward along the longitudinal axis of the vessel to facing transversely to the longitudinal axis of the vessel. The wire  70  may then be locked in place by the latch  72  to position the blade  64  at the endpoint location. 
     The handle  62  may then be manipulated by the physician to allow the blade  64  to gradually embed into the vessel wall as shown in FIG.  5 ( b ). The blade  64  may penetrate the vessel wall through the intima  16  and media  14  layers. The guard  66  prevents the blade  64  from entering the adventia  12  layer. Once the blade  64  has penetrated the vessel wall, the physician may rotate the catheter  68  through 360° which in turn causes the blade  64  to circumferentially cut the intima  16  and media  14  layers to form a clean endpoint. The physician may then manipulate the handle  62  to remove the blade  64  from the vessel wall and face the blade  64  away from the vessel wall. The wire  70  may then be pushed to position the blade  64  to face forward and the handle  62  may be pulled to return the blade back within the lumen of the catheter  68 . 
     After the first endpoint is cut, the physician may remove the catheter  68  a predetermined distance to position the end of the catheter  68  at the location of the second endpoint. These same steps used in cutting the first endpoint are repeated to establish a second endpoint. The physician may then again rotate the blade  64  back into a position facing forward along the longitudinal axis of the vessel and pull the blade  64  back into the lumen of the catheter  68 . The device  60  may then be removed from the catheter  68 . In some instances the physician may not cut a second endpoint. 
     After the device  60  is removed from the catheter, the diseased tissue may be loosened from the adventia between the two endpoints, or up to the single endpoint, by any suitable means, e.g., endarterectomy loop or ring stripper. For example, the physician may insert an endarterectomy loop into the catheter  68  to loosen the diseased tissue from the adventia  12  layer between the first and second endpoints. After the diseased tissue is loosened from the adventia  12  layer, the diseased tissue may then be removed through the catheter  68  by any suitable means, e.g., suction. Once the diseased tissue is removed, the catheter  68  may be removed from the vessel. 
     Referring again to FIG. 5, the device  60  may also be used within a multilumen catheter to perform an endarterectomy. The instrument described in the Harkrider U.S. patent application Ser. No. 09/276,679 for ENDOLUMINAL MULTI-LUMINAL SURGICAL SHEATH AND METHOD is a suitable catheter. 
     An exterior incision may be made in the vessel and the multilumen catheter may be inserted into the vessel. The physician may then insert optics into the first lumen of the catheter for viewing and to thereby locate the diseased tissue. The physician may choose the device  60  to perform the endarterectomy as described herein. The physician may then position multilumen catheter to a position adjacent the location of the first endpoint. 
     The physician may then insert the device  60  into a second lumen of the multilumen catheter with the blade  64  facing forward along the longitudinal axis of the vessel. The blade  64  and guard  66  may be pushed by the handle  62  within the second lumen until the blade  64  and guard  66  exit the second lumen as viewed by the physician through the optics in the first lumen. 
     The blade  64  may then be rotated about the pivot point of the handle  62  by pulling the wire  70  to change the orientation of the blade  64  from facing forward along the longitudinal axis of the vessel to facing transversely to the longitudinal axis of the vessel. The position of the guard  66  and blade  64  may then be locked by latch  72  at the position of the second endpoint location. The position may be latched by any suitable means, e.g., locking screw, ratchet and handle, or locking nut. 
     The handle  62  may then be manipulated to allow the blade  64  to gradually embed into the vessel wall. The blade  64  may penetrate the vessel wall through the intima and media layers. The guard  66  prevents the blade  64  from entering the adventia layer. Once the blade  64  has penetrated the vessel wall, the physician may rotate the multilumen catheter 360° which in turn causes the blade  44  to circumferentially cut the intima and media layers to form a clear endpoint. The physician may then manipulate the handle  62  to remove the blade  64  from the vessel wall and face the blade  64  away from the vessel wall. 
     After the first endpoint is established the physician may remove the multilumen catheter a predetermined distance to the location of the second endpoint. These same steps used in cutting the first endpoint are repeated to establish a second endpoint. The physician may then manipulate the handle  62  to remove the blade  64  from the vessel wall and to face the blade  64  away from the vessel wall. The latch  72  may be released and the wire  70  may be pushed to position the blade forward along the longitudinal axis of the vessel and the device  60  may then be removed from the multilumen catheter. The physician may then loosen the diseased tissue between the two endpoints or up to a single endpoint. For example, the physician may insert an endarterectomy loop to loosen the diseased tissue from the adventia layer. Once the diseased tissue is loosened from the vessel wall, the diseased tissue may be removed through a lumen of the multilumen catheter by any suitable means e.g., suction or by inserting a clamping device into the multilumen catheter. Once the diseased tissue is removed, the multilumen catheter may be removed from the vessel. 
     The device  60  may also be used to cut the vessel wall in a longitudinal direction. After the blade  64  exits the catheter  68  or multilumen catheter the blade  64  may be rotated from a position facing forward along the longitudinal axis of the vessel to a position longitudinal to the vessel and the blade  64  may be embedded into the vessel wall. The catheter  68  or multilumen catheter may then be pulled or pushed to cut longitudinal incisions into the vessel. The blade  64  may then be rotated back to a position where the blade  64  faces forward along the longitudinal axis of the vessel. 
     In another embodiment of the invention the device  60  may also include two wires which may rotate the blade  64  in two different directions, i.e., longitudinally and transversely, so that the endpoint and longitudinal incisions may be made by only one device  60  within the vessel. A wire  70  may be used to position the blade  64  transversely to the axis of the vessel and a wire  74  (not shown) may be used to position the blade longitudinally to the axis of the vessel. 
     While preferred embodiments of the present invention have been described, it is to be understood that the embodiments described are illustrative only and the scope of the invention is to be defined solely by the appended claims when accorded a full range of equivalence, many variations and modifications naturally occurring to those of skill in the art from a perusal hereof.