Abstract:
A present invention relates to a surgical retractor that immobilizes tissue at a surgical site. A preferred embodiment of the retractor is used during minimally invasive direct coronary bypass procedures to arrest movement of the grafting site while the heart continues pumping. Tape or thread can be used to connect the artery to the retractor with a holder.

Description:
RELATED APPLICATIONS 
   This is a continuation application of U.S. Ser. No. 09/307,195 filed on May 7, 1999 now U.S. Pat. No. 7,235,049 which is a continuation application of International Application No. PCT/US98/08348, filed on Apr. 24, 1998 and designating the United States which is a continuation-in-part application of U.S. Ser. No. 08/845,333 filed on Apr. 25, 1997 now U.S. Pat. No. 6,033,362, the entire teachings of the above applications being incorporated herein by reference. 

   BACKGROUND OF THE INVENTION  
   Numerous devices have been used to position tissue at a surgical site to aid in the performing of surgical procedures. Retractors, for example, have been used to hold an artery in position during operations adjacent to the heart to prevent movement of the artery. This serves to minimize the risk of injury to the artery and adjacent tissue and can facilitate the desired anastomosis. 
   A recently developed procedure, referred to as the minimally invasive direct coronary artery bypass procedure, has been used to graft onto a coronary artery without cardiopulmonary bypass. This procedure involves the grafting of the left internal mammary artery (LIMA) onto the left anterior descending (LAD) or other artery. As this procedure does not require the use of a heart lung machine to oxygenate and pump blood, the morbidity and mortality associated with this procedure is substantially lower than previous bypass techniques. A problem associated with the minimally invasive procedure, however, is that while the heart continues to pump during the procedure, the motion of the heart can interfere with the surgeon&#39;s task of attaching the LIMA to the LAD. There is also a need to stop blood flow in the area of the graft to maintain a clear field of view and provide precise suture placement. 
   Two basic strategies have been employed to address the problem of operating on a moving site, one being the use of pharmacological agents to limit heart motion, and the other being mechanical, such as a two prong retractor that is pushed down against the heart on both sides of the artery, or alternatively, upward traction away from the moving heart by traction tape or suture thread. Both of these options, however, have problems associated with them. Both options are susceptible to some movement of the vessel grafting site. The use of pharmacological agents is undesirable and impairs circulatory function. Traction by compression of the heart against the spine does serve to immobilize the site but can compromise the ability of the heart to maintain circulation and result in hypotension. Upward traction can involve circumferential compression of the artery to occlude the artery and prevent blood flow, however upward traction that is sufficient to immobilize the site can cause injury, stenosis or occlusion of the vessel. 
   There is a continuing need however for improvement in devices and methods for retaining tissue at surgical sites to further reduce the risks associated with surgical procedures where the devices and methods are inexpensive, safe and reliable. 
   SUMMARY OF THE INVENTION  
   The present invention relates to a surgical retractor for immobilizing tissue at a surgical site and to a method of using the retractor during a surgical procedure. A preferred embodiment of the retractor includes a retaining element having an aperture that exposes the surgical site and a holder that is used to position tissue at the surgical site relative to the retaining element. A handle can be attached to or fabricated with the retaining element or platform so that the user can manipulate the position of the retractor as needed. 
   In a preferred embodiment of the invention a connector such as elastic tape or thread is used to position tissue at the surgical site within the retractor aperture and to prevent movement of the tissue during the procedure. The connecting cord, thread or tape also aids in the compression of the artery in a grafting procedure to occlude flow on one or both sides of the surgical site. The cord is attached to the holder on the retaining element. A preferred embodiment of the holder can be a plurality of slits or openings positioned on both sides of the retractor that receive and frictionally secure the cord on both sides of the aperture. In another preferred embodiment a mechanical fastener is used to grip both sides of the cord. The fastener can be a spring mounted valve, for example, that allows the user to adjust the tension in the cord. 
   A preferred embodiment of the invention comprises a retaining element or base having two sections that can be separated after the procedure is complete to permit removal of the retractor from under the grafted artery. Another preferred embodiment uses a side opening in the platform of the retractor that extends to the aperture so that the grafted artery slips through the side opening during removal. During minimally invasive direct coronary artery bypass operations, one or more surface sections of the retractor platform can be positioned against the inner surface or posterior aspect of one or both ribs adjacent to the surgical site. Thus, the size and geometry of the platform are selected to utilize the adjoining ribs where the upper surface of the platform frictionally engages the inner surface one or more ribs to hold the retractor in a fixed position. The retractor can be beneficial in any procedure where it is necessary to stabilize a surgical site. For example, the retractor can also be used for grafting onto the diagonal, right or other coronary arteries without altering the heart&#39;s pumping function. 
   The coronary arteries are about 1-2 mm in diameter, and the pumping heart can move these arteries over distances of several millimeters during each heartbeat. As the movement of even 1 or 2 millimeters can result in a displacement of the grafting site that can substantially interfere with effective anastomosis, it is desirable to restrain movement of the artery at the surgical site in any direction to less than 1 mm. The retractor of the present invention restrains movement in the plane of the base to less than 0.5 mm, and preferably less than 0.2 mm. 
   In a preferred embodiment of the invention, the handle or articulating arm that is secured to the platform can be held in position by the user, attached to a frame that is fixed around the operative site or simply clipped to a drape around the site. 
   When used in a minimally invasive coronary bypass procedure, the retractor is positioned to expose the left anterior descending (LAD) artery grafting site after incision, removal of the rib section and dissection of the left internal mammary artery (LIMA) from the chest wall. A pair of cords, for example, sialastic tape (i.e. a silicon elastomer) or suture thread, are passed through the myocardium at two locations flanking the artery grafting site with blunt needles. The four ends of the two cords are connected to the platform holder with sufficient tension to occlude blood flow on both sides of the operative site. The tapes compress the artery against the bottom surface of the platform while they hold the artery grafting site in a fixed position relative to the aperture. The coronary artery is opened longitudinally and the end of the mammary artery is sewn to the graft opening with multiple fine sutures. The cords are released, blood flow is restored and the anastomosis is inspected for hemostatis and other defects and the wound is closed. 
   The platform can include tabs or cord retainers that extend into the aperture to provide a surface against which the arteries can be compressed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a surgical retractor in accordance with a preferred embodiment of the invention. 
       FIG. 2  is a perspective view of a surgical site illustrating a surgical procedure. 
       FIG. 3  is a perspective view of a surgical retractor for a grafting procedure in accordance with the invention. 
       FIG. 4  is a bottom perspective view of a surgical retractor in accordance with the invention. 
       FIG. 5  is a cross-sectional view of a surgical retractor during a surgical procedure. 
       FIGS. 6A and 6B  are partial cross-sectional views of a holder in accordance with the invention. 
       FIG. 7  is a top view of a two piece retainer in accordance with the invention. 
       FIG. 8  is a top perspective view of another preferred embodiment of a surgical retractor in accordance with the invention. 
       FIG. 9  is a top perspective view of another preferred embodiment of a surgical retractor in accordance with the invention. 
       FIG. 10  is a schematic diagram illustrating a surgical procedure in accordance with the invention. 
       FIG. 11  is a perspective view of a frame supporting a retractor in accordance with the invention. 
       FIGS. 12A and 12B  are enlarged detailed views of a surgical retractor in accordance with the invention. 
   

   The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
   DETAILED DESCRIPTION OF THE INVENTION  
   A preferred embodiment of the invention is illustrated in connection with  FIG. 1 . A retractor  10  includes a retaining element or base  12  having an aperture  16  that is positioned to expose tissue at a surgical site. The base  12  can be made with a metal or a molded plastic material. The retractor  10  can be sterilized after each use, or alternatively, can be disposable after one procedure. A handle  30  or articulating arm can be permanently attached to the base  12 , or as described below in connection with other preferred embodiments, can be detachable. 
   A suction tube  32  can be attached to the handle  30  or integrated therein and is used to remove material such as blood from the operative site. In this particular embodiment the tube  32  is connected at one end to a tube  34  from a suction pump and connected at a second end to a port  36  in fluid communication with a channel within tube  28  that extends around the periphery of base  12 . The peripheral tube can have small openings  38  positioned on the sides or top thereof through which fluid such as blood or other debris can be suctioned from the surgical site to maintain a clear field. 
   A preferred embodiment of the invention can be used at a surgical site  66  such as the example illustrated in  FIG. 2 . In this particular procedure for coronary graft without coardiopulmonary bypass, a section of the 4 th  costal cartilage or rib  56  is removed to expose a section of the LAD artery  61 . 
   A proximal portion of the LIMA  62  is dissected from the chest wall to expose an end  65  to be grafted onto a grafting site  60  on artery  61 . Blood flow in vessel  62  can be occluded with a clamp  64 . 
   In this example, a connector such as a pair of cords or sialastic tapes  70 ,  72  are threaded through myocardium surface  78  under the artery  61  at two locations  74 ,  76  on opposite sides of the grafting site  60 . Note that the exposed surface  78  of heart  52  is undergoing substantial movement during the procedure. 
   As seen in the reverse perspective view of  FIG. 3  in which the retractor  10  has been inserted and positioned during the procedure, the retractor  10  serves to immobilize the grafting site  60  using connecting tapes  70 ,  72  which are stretched and attached to a holder mechanism including slots  20   a - 20   d  in the peripheral edge of base  12 . As described in greater detail below, the slots  20 A- 20   d  can be manually opened or closed using actuators  22   a - 22   d,  respectively, to allow the user to adjust the tension in the tapes or threads. 
   The aperture  16  extends longitudinally along the axis of artery  61 . The site  60  is preferably located in the plane of the upper surface of base  12 . The tapes  70 ,  72  exert a compressive force on the artery  61  which is pressed against a bottom surface  40  as seen in  FIG. 4 . More particularly, the tapes  70 ,  72  extend in a direction that is substantially perpendicular to the artery  61  axis exposed in the aperture  16 . The aperture can have a first pair of lateral sections  18   a  and  18   b  which are aligned to accommodate the positioning of tape  70  and the aperture can also have a second pair of lateral sections  18   c  and  18   d  to accommodate the positioning of tape  72 . Alternatively, holes extending through the base  12  that are separated from the aperture can be used. The holes are large enough to provide easy feed through and can be angled towards the bottom center to provide compression of the artery at lower tension of the cord. 
   The size of the aperture can be in the range of 1-3 cm in length and 5-15 mm in width. The aperture can be narrower in the center and wider at the opposite ends to accommodate the openings or sections  18   a - 18   d.    
   Between each pair of sections  18   a - 18   b  and  18   c - 18   d,  a sidewall section of the aperture, namely tabs  24 ,  26  extend on opposite ends of aperture  16 . The tapes  70 ,  72  compress respective portions of artery  61  on opposite sides of site  60  against tabs  26 ,  24 . As seen in  FIG. 4 , those portions  42 ,  44  of the bottom surface  40  are in contact with artery  61  and compress it. The bottom surface that surrounds the artery and is in contact with the heart wall can be roughened or abraded to frictionally engage the heart wall around the artery and thereby locally restrict heart motion around the surgical site. 
   In a preferred embodiment of the invention opposite ends  82  and  84  can be positioned under adjacent ribs  54  and  58 , respectively. This eliminates any substantial movement of the base  12  while the heart is pumping so that anastomosis  80  of the end  65  onto site  60  can be quickly completed. The opposite ends  82 ,  84  can be slightly raised relative to the plane of the remainder of the base  12  to provide a concave structure to enhance the frictional engagement of sections  82 ,  84  to ribs  54 ,  58 , respectively. The platform has a substantially rectangular shape with each side having a length in the range between 3.5 cm and 6 cm. Thus the surface of the platform is between 12 cm 2  and 25 cm 2 , preferably between 14 cm 2  and 20 cm 2 . This size fits readily in the incision between the ribs and can be positioned with both ends extending under the 3rd and 5th ribs. This structure exerts little downward force on the heart or upward force on the artery while immobilizing the artery at the surgical site. Also the anterior-posterior compression of the artery avoids trauma to the artery due to circumferential compression. By engaging the ribs, the retractor is self-retaining providing for easier use and manipulation. 
   As seen in  FIG. 5 , the tape  76  under the bottom surface  94  of the tab  24  lifts the artery  60  to form an occlusion  86 . This view also shows the optional channel  92  extending around the periphery of base  12  that is used to irrigate or suction around the site. 
   The fastening mechanism is illustrated in the partial cross-sectional views of  FIGS. 6A and 6B . The closed position  110  is illustrated in  FIG. 6A  where spring  112  has expanded to move slot  116  in element  115  out of alignment with slot  114  in the outer tube. The cord  72  is displaced and frictionally grasped by the sliding movement of element  115 . The user can manually displace  118  to align slot  114  with slot  116  while compressing spring  112 . In the “open” position  120 , the cord  72  can be easily removed or pulled through to increase tension. 
   After the procedure is complete the retractor  10  needs to be removed from the site. In the embodiment of  FIG. 1 , the base  12  can be formed with two sections or plates  14   a,    14   b.  As seen in  FIG. 7 , these components can be separated at joint  25  to allow removal of the retractor  10 . The two halves  14   a,    14   b  can be connected with a frictional tube section  96 . 
   In the preferred embodiment illustrated in  FIG. 8 , the retractor  100  can have a plurality of handle attachment sites  102 ,  104 ,  106 ,  108  so that the user can attach the handle  105  at any site to provide the most convenient access to the aperture and facilitate immobilization of other arteries. The handle can alternatively be positioned between the two cords at an orthogonal angle relative to the aperture axis and extending above the top surface of the base. 
   In another preferred embodiment of the invention illustrated in the perspective view of  FIG. 9 , a retractor  140  has a handle  142 , slots  144  located in the plane of the aperture  160  to secure the cords extending through lateral sections of the aperture (for example, sections  152 ,  154 ), end sections  162 ,  164  that engage the ribs  54 ,  58 , tabs  148 ,  150  for compression of both sides of the artery at the site  60  and a side opening  146  so that the retractor can be removed. 
   In this embodiment, the LIMA slides out through opening  146  during removal of the retractor after completion of the procedure. This unitary retractor structure  140  can also include various features described previously in connection with the embodiment of  FIG. 1  including the attached or integrated suction tube, the detachable handle, the irrigation or suction channel with ports or the mechanically actuated fasteners. 
   A preferred method of stabilizing tissue during a coronary bypass procedure  200  is illustrated in the process flow sequence of  FIG. 10 . A 5-8 cm sized incision is made over the 4th rib and a section of the 4th costal cartilage is removed  202 . The LIMA is dissected from the chest wall  204  and divided distally. After blood flow assessment the LIMA can be temporarily closed with a spring loaded clip. 
   A self-retaining wound retractor is used to distract the edges of the incision and a “trap door” incision is made in the pericardium and the cut edge sewn to the skin to pull the pericardial sack and heart anteriorly. The LAD is exposed and a site suitable for anastomosis is selected for grafting  206 . Tapes are inserted in the myocardium with blunt needles approximately 1-2 cm apart  208  and the retractor is inserted  210  with the tapes being pulled through the aperture and positioned in the lateral sections thereof. The tapes are connected to the holder  212  to compress the artery  214  and occlude blood flow on both sides of the grafting site. The tension in the tapes can optionally be adjusted during the procedure to minimize blood loss at the site. 
   The retractor is secured  216  at the site by positioning one or both ends under adjoining ribs, or alternatively, attaching the handle or arm to the wound retractor or other implement. The grafting site undergoes less than 0.1 mm of movement in any direction during this example procedure. 
   The site is suctioned or irrigated  218  during anastomosis, the grafting site is inspected, the tapes are released from the holders, and the retractor is removed either by sliding the LIMA through a side opening in the retractor or detaching a section of the retractor to accommodate removal of the LIMA from the aperture. After blood flow is restored, the site is inspected and closed  220 . 
   Although the use of the retractor has been described in connection with a particular bypass procedure, it can also be used in other procedures such as bypass operations involving the diagonal, right or other coronary artery where movement at the site can interfere with the procedure. 
   Alternative embodiments involve opening of the chest and positioning the retractor at any exposed site on the heart wall or surrounding areas to immobilize the operative site. The retractor serves to isolate the site and limits or stops motion at the site due to respiratory movement of the lungs or the pumping motion of the heart. 
   In another preferred embodiment, a stabilizer system or frame  240  manufactured by Genzyme Surgical Products is illustrated in  FIG. 11  to support a surgical retractor  260  in accordance with the invention. 
   The frame  240  used with the invention includes a bar  242  having an arm  244  extending orthogonally from a first end and attached to a second arm  246  with a thumb screw at a second end. Each arm  244 ,  246  has a pair of mounting elements  252 ,  255  on which a pivot rod  256  can be mounted. This rod  256  can be rotated 360 degrees to any desired position such that mounting arm  245  can oriented relative to the surgical site as needed to position the retractor  260 . Each arm  244 ,  246  has a pair of grippers  248 ,  250  that engage anatomical features such as neighboring ribs at the site to stabilize the frame  240 . 
   The mounting arm  245  supports the handle or support arm  262  with a friction fitting  258  which the user tightens with knob  268  to grip arm  262  at region  266 . The support arm  262  has a knob  264  at one end that can be turned by the user to engage a post  276  shown in  FIG. 12A . A ball on the post  276  can be slipped through an opening  265  in the second end of arm  262  and locked into position using knob  264 . 
   The post  276  can be pivoted relative to arm  262  by loosening the knob  264 , thus allowing the user to orient the retractor  260  at the site for fine positioning. The post  276  is mounted on a plastic retaining element  270  in this embodiment. The element  270  can be a transparent or opaque molded device that can be separated into two components  272 ,  274  as described previously. The two components can be attached by friction fit rods  294  that are inserted into holes in element  272 . Element  270  can be made with a transparent material to enhance viability at the site. 
   Both components have raised holder elements  284 ,  286 . Element  284  has a pair of slots  288 ,  289  that each frictionally grip an end of a cord which extends through the aperture  278  to attach tissue to the retractor. The second end of each cord is gripped by corresponding slots  290 ,  292  in element  286 . 
   Tabs or cord retainers  280 ,  282  are integrally formed with component  274  and function as described previously. In the detailed partial view of  FIG. 12B , the front inclined surface can be formed at a shallower angle such that the top ridge  279  is narrower. This embodiment of cord retainer  281  affords easier insertion of cords into the aperture. 
   This embodiment can also be formed with integral suction channels or openings in the top surface of the element  270 . A suction tube can be attached through or with the arm  262  or attached to a suction port on element  270 . 
   While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.